Contents

### **Preface XI**

## **Section 3 Security and Template Protection 171**

Preface

new challenge fields.

be thought together and deeply integrated.

In recent years, biometrics has developed rapidly with its worldwide applications for daily life. New trends and novel developments have been proposed to acquire and process many different biometric traits. The ignored challenges in the past and potential problems need to

The key objective of the book is to keep up with the new technologies on some recent theoretical development as well as new trends of applications in biometrics. The topics covered in this book reflect well both aspects of development. They include the new development in forensic speaker recognition, 3D and thermo face recognition, finger vein recognition, contact-less biometric system, hand geometry recognition, biometric performance evaluation, multi-biometric template protection, and novel subfields in the

The book consists of 13 chapters. It is divided into four sections, namely, theory and method, performance evaluation, security and template protection, and other applications. Chapter 1 explores the latest techniques which are being deployed in the various branches of speaker recognition, and highlights the technical challenges that need to be overcome. Chapter 2 presents a novel biometric system based on 3D and thermo face recognition, including specify data acquisition, image processing and recognition algorithms. In Chapter 3, the author proposes a scattering removal method for finger-vein image restoration, which is based on a biological optical model which reasonably described the effects of skin scattering. Chapter 4 gives an overarching survey of existing principles of contact-based hand geometry systems and mentions trends in the contact-less systems. Chapter 5 introduces a new subfield, namely, Genetic and Evolutionary Biometrics (GECs), which shows how GECs can be hybridized with a well-known feature extraction technique needed

Section 2 is a collection of two chapters on performance evaluation. Chapter 6 analyzes the efficiently and reliably whether the state-of-the-art speaker recognition techniques can be employed in this context, as well as the limitations and their strengths to be improved to migrate from old-school manual or semi-automatic techniques to new, reliable and objective automatic methods. Chapter 7 presents the performance evaluation of biometric systems related to three aspects: data quality, usability, and security. Security as respect to the

for recognition, recognition accuracy, and computational complexity.

privacy of an individual is focused on emerging trends in this research fields.

#### **Section 4 Others 219**

Chapter 10 **An AFIS Candidate List Centric Fingerprint Likelihood Ratio Model Based on Morphometric and Spatial Analyses (MSA) 221** Joshua Abraham, Paul Kwan, Christophe Champod, Chris Lennard and Claude Roux


**Evaluation of the Weed Infestation, Grain Health, and Productivity Parameters of Two Spelt Wheat Cultivars Depending on Crop Protection Intensification and Seeding Densities**

**Małgorzata Haliniarz 1 , Dorota Gaw ˛eda 1,\* , Bo ˙zena Nowakowicz-D ˛ebek 2 , Agnieszka Najda 3 , Sylwia Chojnacka 1 , Justyna Łukasz 1 , Łukasz Wlazło 2 and Monika Ró˙za ´nska-Boczula 4**

Received: 15 May 2020; Accepted: 11 June 2020; Published: 15 June 2020

**Abstract:** Spelt wheat is one of the oldest wheat with very high nutritional value. It does not have particular climatic requirements and tolerates adverse environmental conditions well. The versatile advantages of spelt wheat make it attractive to farmers, plant breeders, food technologists, and consumers. The aim of this study was to determine the effect of different crop protection systems and seeding densities on yield, weed infestation, and grain health of the spelt wheat cultivars "Rokosz" and "Schwabenspelz". The research showed that the spelt wheat cultivars studied responded differently to production intensification. The use of crop protection chemicals in the crop of the cultivar "Rokosz" resulted in lower weed infestation and in obtaining higher yields. In the case of the cultivar "Schwabenspelz", production intensification did not have a significant effect on its productivity and quantitative weed infestation parameters. Therefore, this cultivar can be recommended for cultivation in farms with extensive farming methods, for example, in organic farms. In both cultivars studied, an increase in seeding density and chemical plant protection with fungicide caused lower grain contamination with mycotoxins, and the content of individual mycotoxins did not exceed the maximum levels set for grain intended for food and animal feed purposes.

**Keywords:** spelt wheat; cultivars; crop protection methods; seeding rate; weed infestation; yield; fungi; mycotoxins

#### **1. Introduction**

Spelt wheat (*Triticum aestivum* ssp. *spelta*) probably originates from the region of southeastern Asia and is one of the oldest wheat subspecies [1,2]. The beginnings of its cultivation date back to the Stone Age. Archaeological investigations reveal that, starting with the Bronze Age, spelt was the most important consumption crop in Europe for many years [3,4]. However, its small production potential and difficulties with grain dehulling became the reason why the cultivation of this crop was abandoned in favor of more productive common wheat varieties [4,5].

Changing trends both in cultivation of agricultural crops and in human nutrition have been observed in recent years. People have started to attach a great importance to increased biological diversity of agricultural plant communities, reduced use of industrial production means in agriculture, and consumption of products with health promoting properties [3,4,6]. During the last 20 years, due to its nutritional qualities, spelt wheat was again introduced into cultivation, primarily through the organic farming system [7–11]. In Poland, similar to other European countries, the cultivation of spelt wheat is concentrated in organic farms and the interest in this cereal is continually growing [12]. The estimated cropped area of spelt in 2015 was about 225 ha [13]. The productivity of this species in Poland varies greatly. Grain yield can exceed 6 t ha−1 [14], while under conditions unfavorable for growing common wheat, yields can be even higher than those obtained for common wheat [12]. In comparison with common wheat, spelt grain contains more protein, gluten, and fat, but less dietary fiber. It is a rich source of silicon, minerals, and group B vitamins. Moreover, it contains substances with antioxidant properties [5,15–18]. Spelt wheat does not have high climatic and soil requirements, and tolerates adverse environmental conditions well [19–22]. It is characterized by a rather high level of resistance to ear and grain diseases caused by fungal pathogens [8,23] and, due to its high tillering ability, competes with weeds better than common wheat [24]. These characteristics allow this crop to be grown without excessive use of crop protection products and mineral fertilizers, and hence it is considered to be environmentally friendly [25]. Studies conducted by different researchers have shown great variations in productivity and quality parameters between different spelt wheat varieties [18,21,26,27], as well as their varying response to soil and climatic conditions [22] and agronomic factors [18,27–29]. Most research is focused on organic cultivation of spelt [17,21,22,30], but there is little information how spelt wheat responds to production intensification. According to Racho ´n et al. [31] and Andruszczak et al. [32], higher grain yields were obtained under full chemical protection conditions compared to extensive cultivation conditions. Therefore, a study was undertaken to explain how crop protection intensification and different seeding densities affect yield, yield components, weed infestation, and grain health of two winter wheat spelt cultivars. Taking into account the genetic characteristics of spelt wheat, the experiment assumed that (i) the absence of any crop protection or mechanical protection and application of herbicide alone would not contribute to a significant decrease in grain yield and health, compared to full chemical protection; (ii) pro-ecological technology involving the complete abandonment of crop protection or the use of only harrowing would not deteriorate the productivity of spelt wheat and its health, in comparison with chemical protection; (iii) in treatments with a higher seeding rate, the denser spelt crop would be more competitive against weeds, which would contribute to reduced weed infestation and would not increase grain infection with fungal pathogens, in consequence allowing a satisfactory yield to be obtained; and (iv) the response of spelt wheat to production technologies is cultivar-dependent.

#### **2. Materials and Methods**

#### *2.1. Location of the Experiment—Soil and Climatic Conditions*

The field study was carried out for three growing seasons, 2012/2013, 2013/2014, and 2014/2015, at the Czesławice Experimental Farm (51◦18′23′′ N, 22◦16′2 ′′ E), belonging to the Lublin University of Life Sciences, Poland. The experiment on growing spelt wheat was established on a loess-derived Luvisol. The arable layer of the soil was characterized by high availability of phosphorus (P, 76.3–77.7 mg kg−1 soil) and potassium (K, 117.8–132.3 mg kg−1 soil), as well as medium availability of magnesium (Mg, 79–85 mg kg−1 soil), slightly acidic pH (in 1 M KCl, 6.1–6.4), and a low humus content of 1.59–1.63%.

The 2013/2014 season could be described as very wet since the total rainfall was higher by 281 mm than in the 2014/2015 season, 147.1 mm higher than in 2012/2013, and 206.3 mm higher than the 1963–2010 average (Table 1). In the years 2013 and 2014, the amount of rainfall in May and June much exceeded the long-term average (LTA). In August 2014, there was 32.5 mm more rain than the LTA. In 2015 the amount of rainfall in May was high, but June and August were very dry with only 13.5 and 5.9 mm of rain, respectively. The temperature ranges in the 2013/2014 and 2014/2015 growing seasons were similar. The mean temperature in these years was higher by 0.9 ◦C in the 2013/2014 season and by 1 ◦C in 2014/2015. In the 2012/2013 season, the mean temperature was the same as the long-term average. In all the growing seasons, July was warmer than over the period 1963–2010.

**Table 1.** The rainfall and mean monthly air temperature in the growing season of spelt wheat, recorded by the Meteorological Station in Czesławice (Poland). LTA is the long term average.

#### *2.2. Experimental Design and Agronomic Practices*

A field experiment was set up using a split-block design in three replicates. Two winter spelt wheat cultivars, the German cultivar "Schwabenspelz" and the Polish cultivar "Rokosz", were evaluated in this study. The experiment included the following factors:

I—crop protection

1. pro-ecological:

A—untreated control plots (no herbicide, fungicide, or insecticide treatment);

B—harrowing in early spring at the beginning of the growing season;

2. chemical:

C—application of the herbicides Sekator 125 OD (Bayer AG, Leverkusen, Germany, active ingredients (a.i.) amidosulfuron, iodosulfuron, mefenpyr-diethyl) at a rate of 150 mL ha−1 and Attribut 70 WG (Bayer AG, Leverkusen, Germany; a.i. propoxycarbazone-sodium) at a rate of 60 g ha−1 at BBCH (**B**iologische **B**undesanstalt, **B**undessortenamt und **CH**emische Industrie) stages 22–24 of spelt wheat;

D—application of complete chemical protection—the herbicides Sekator 125 OD at a rate of 150 mL ha−1 and Attribut 70 WG at a rate of 60 g ha−1 at BBCH 22–24 of spelt wheat; the growth retardant Cerone 480 SL (Bayer AG, Leverkusen, Germany, a.i. ethephon) at BBCH 30–31 at a rate of 0.75 L ha−1 , the fungicide Wirtuoz 520 EC (Corteva, Inc., Wilmington, DE, USA, a.i. prochloraz, tebuconazole, proquinazid) at BBCH 24–25 and 32–33 at a rate of 1 L ha−1 , as well as the insecticide Decis 2,5 EC (Bayer AG, Leverkusen, Germany, a.i. deltamethrin) at BBCH 37–39 at an amount of 0.25 L ha−1 .

II—seeding density:

Mineral fertilization was applied at the following rates: N, 50 kg ha−1 ; P, 26.2 kg ha−1 ; and K, 58.1 kg ha−1 . All phosphorus and potassium fertilizers and part of the nitrogen fertilizers (20 kg N) were applied before sowing the spelt wheat. The remaining portion of nitrogen fertilizers was applied right after the beginning of the growing season. The sown and harvested plot area was 13.5 m2 , per repetition. Winter wheat was the previous crop for spelt wheat. Tillage was typical for common wheat cultivation. The spelt wheat was sown in the third decade of September 2012–2014 and harvested in the second decade of August 2013–2015.

#### *2.3. Evaluation of Yield and Weed Infestation*

Approximately 3–4 weeks after herbicide treatment and at the dough stage of spelt wheat (BBCH 83–85), evaluation of weed infestation of the spelt crop was made using the dry-weight-rank system. The evaluation involved determination of the botanical composition of weeds, as well as their number and dry weight per 1 m2 . The sampling area was delineated with a 0.5 × 1 m quadrat frame in two randomly selected places in each plot. Weed nomenclature followed Mirek et al. [33].

Plant height and ear length were determined based on 30 randomly selected plants from each plot. Weight of grains per ear was determined based on the average results for 30 randomly selected ears per plot. Ear density was calculated in two randomly chosen places with an area of 0.5 m2 per plot. Yield was estimated based on grain harvested from the individual plots and expressed on a per hectare basis.

#### *2.4. Determination of Fungal Contamination of Grain*

Samples of about 20 g of spelt grain (from each plot) were homogenized by hand for 5 min and then sedimented for 15 minutes in sterile dilution liquid with approximately 100 µL of Tween 80 (Sigma-Aldrich, St. Louis, MO, USA). The dilutions were prepared and inoculated on sterile Sabouraud Chloramphenicol Agar (BTL Poland Ltd., Warsaw, Poland). To determine the total number of fungi, the plates were incubated at a temperature of 25 ± 0.2 ◦C for 7 days according to the relevant standard [34,35]. The colonies were transferred to microcultures and species were determined using Watanabe's key [36]. Each sample was analyzed in triplicate and the results presented as the number of fungi per 1 g of the tested material (cfu g−1 ).

#### *2.5. Determination of Mycotoxin Contamination of Grain*

The content of deoxynivalenol (DON) and its derivatives: 3-O-acetylDON (3AcDON), 15-O-acetylDON (15AcDON), and zearalenone (UAE) were determined according to the authors' method developed in the Laboratory of Vegetable and Herb Raw Material Quality Research: "Determination of deoxynivalenol and its derivatives, nivalenol and zearalenone by HPLC method with purification by immunological affinity column in plant raw materials". The presence of trichothecene mycotoxins such as T-2 toxin (T-2) and its derivatives HT-2 toxin (HT-2), nivalenol (NIV), DAS (diacetoxyscirpenol), and fuzarenone X were analyzed by gas chromatography following the procedure given by Valle-Algarra et al. [37].

#### 2.5.1. Sample Preparation and Extraction

A 5 g sample of spelt grain previously finely ground with a laboratory mill (FW135, ChemLand, Stargard Szczeci ´nski, Poland) was placed in a test tube and treated with 20 mL of acetonitrile (ACN): H2O so lution (85:15). The diluted samples were shaken with a centrifuge (30 min, 21.000× g, Universal 32, Hettich, Tuttlingen, Germany) and left for 6 h, after which time it was again shaken for 30 min. The extract was filtered through a 0.2 Pm membrane syringe filter (Costar X, Corning Inc., Salt Lake City, UT, USA). Then, 5 mL of filtrate was collected for thorough purification and applied to a MycoSep 225 Trich column (Romer Laboratories, Union, MO, USA). Two mL of purified eluents were evaporated to dryness at 50 ◦C, and the residue dissolved in 0.5 mL of mobile phase (10% aqueous acetonitrile) after which the mycotoxin content was determined.

#### 2.5.2. HPLC Analysis Conditions

A LaChrom–Merck HPLC liquid chromatograph (Merck, Darmstadt, Germany) was equipped with a DAD diode detector (L-7450), binary pump (L-7100), degasser (L-7612), thermostat (L-7360), Rheodyne injector, and steel column LiChrospher 100 RP C18 (250 × 4 mm) filled with stationary phase (particle diameter—dp = 5 µM). UV detection was performed at 220 nm (deoxynivalenol, 3-O-acetylDON, 15-O-acetylDON) and 220–440 (zearalenone) at 28 ◦C and a flow rate of 0.800 mL min−1 . The mobile phase was aqueous acetonitrile. Separation was achieved in an isocratic water: acetonitrile (8:92) analysis by deoxynivalenol, 3-O-acetylDON, 15-O-acetylDON, and (63:37) by analysis of zearalenone. To increase the separation, 1% acetic acid was added to the mobile phase. Identification of analyzed compounds was made on the basis of retention time. Quantitative assessment was carried out using the external standard method, after creating a calibration curve using pure reference substances.

#### 2.5.3. GC/MS Analysis Conditions

Separation of trichothecenes, nivalenol, and fuzarenone X was carried out using a Varian CP-3800 gas chromatograph (Varian Medical Systems, Palo Alto, CA, USA) equipped with an detector ECD (instant connect Electron Capture Detector) and columns VF-1ms 30 m × 0.32 mm ID (Column Internal Diameter), DF (film thickness) = 0.25 µm from Varian. The temperature of the dispenser chamber was 250 ◦C and the detector 300 ◦C. The following oven temperature gradient was used: 80 ◦C for 1 min, increment 40 ◦C for 1 min to 160 ◦C, 3 ◦C for 1 min to 178 ◦C, 2 ◦C for 1 min to 240 ◦C, 40 ◦C for 1 min to 270 ◦C, 270 ◦C for 1 min. Nitrogen was used as carrier gas at a flow rate of 1 mL for min.

#### 2.5.4. Chemical Reagents

Organic solvents with spectroscopic purity were obtained from Merck (Darmstadt, Germany). All deoxynivalenol (DON) purity ≥ 95% (reference standard), 3-O-acetylDON (3AcDON) purity ≥ 95% (reference standard), 15-O-acetylDON (15AcDON) purity ≥ 95% (reference standard), zearalenone (UAE) purity ≥ 95% (reference standard), T-2 toxin (T-2) purity ≥ 95% (reference standard) and its derivatives HT-2 toxin (HT-2) purity ≥ 95% (reference standard), nivalenol (NIV) purity ≥ 95% (reference standard), DAS—diacetoxyscirpenol purity ≥ 95% (reference standard) and fuzarenone X purity ≥ 95% (reference standard) were from Sigma-Aldrich (St. Louis, MO, USA).

#### *2.6. Statistical Analysis*

The results were statistically analyzed using analysis of variance (Statistica PL 13.3, StatSoft Polska, Krakow, Poland). The distribution conformity with normal distribution was verified with the Shapiro–Wilk test, while homogeneity of the variance was tested with Levene's test. In the case of any feature where a significant interaction was found between the factor and year, interaction effects were analyzed separately for each year of the study. If no significant interactions were found between the factors, then Tukey's multiple comparison test was used to compare differences between the means for main factors (crop protection, seeding density, cultivar). Confidence half-intervals were calculated by Tukey's test at a significance level of 0.05. Significant differences between the two groups of treatments, pro-ecological protection (treatments A and B) and chemical protection (treatments C and D), were evaluated based on the Scheffe test (α = 0.05). Total number of fungi in grain is presented in log CFU g−1 .

#### **3. Results**

#### *3.1. Weed Infestation of Spelt Wheat*

The statistical analysis of the weed infestation parameters for the crop of the "Rokosz" spelt wheat cultivar, as evaluated 3–4 weeks after herbicide application, revealed significant differences in the traits between years (Table 2). The highest number of weeds was found in the first year of the study in the treatments where no herbicide was used (treatments A and B) and in the second year of the study in the control treatment. Weeds produced the highest biomass in 2013 in treatments A and B. Harrowing done as the only weed control operation (treatment B) proved to be ineffective in reducing weed infestation because the number and dry weight of weeds were similar to those found in the control treatment (A) in each year of the study. However, it was only in 2013 that weed infestation in this treatment was significantly higher than in the treatments where the herbicide was applied. In the years 2014 and 2015, as well as in treatments C and D in 2013, weed infestation of the crop was at a similar level. At the dough stage of wheat, crop protection method and year were not found to significantly affect number of weeds. The highest weight of weeds was determined in the first year of the study in the treatments without herbicide application (A and B). In the other treatments, the weight of weeds was similar. The results for the three-year study showed that in cv. "Rokosz", herbicide application had a significant impact on weed infestation of the crop. At the first evaluation of weed infestation, the average number of weeds in the chemical protection treatments (C and D) was more than one-half lower, while their dry weight was four times lower than in the pro-ecological treatments A and B. At the dough stage of cv. "Rokosz", similar relationships were observed as those made 3–4 weeks after herbicide treatment.

**Table 2.** The weed infestation indicators in the spelt wheat cv. "Rokosz" showing the interaction between crop protection and years of research, and comparison of the pro-ecological and chemical crop protection. NW I—number of weeds 3–4 weeks after herbicide treatment, WW I—air-dry weight of weeds 3–4 weeks after herbicide treatment, NW II—number of weeds at the dough stage of spelt wheat (BBCH 83–85), WW II—air-dry weight of weeds at the dough stage of spelt wheat (BBCH 83–85). Different letters denote significant differences (*p* ≤ 0.05). The same letter means not significantly different values.

−

In the cv. "Schwabenspelz" crop, the evaluation of weed infestation performed 3–4 weeks after herbicide treatment demonstrated that significantly the lowest number of weeds was found under chemical protection conditions (treatments C and D) (Table 3). Nonetheless, the number of weeds in the harrowing treatment and in the treatment where the herbicide was applied alone (treatment C) was similar. After application of chemical protection (treatments C and D), the dry weight of weeds was lower by 76.4% and 69.4% than in the control treatment (A). The statistical calculations showed that at the first evaluation of weed infestation, the average number and dry weight of weeds found in the chemical treatments (C and D) were significantly lower than those determined for the pro-ecological treatments (A and B) by 42.7% and 70.5%, respectively. At the dough stage of wheat, crop protection method was not shown to have an effect on the number and dry weight of weeds in the cv. "Schwabenspelz" crop.

**Table 3.** The impact of crop protection system on weed infestation indicators in the spelt wheat cv. "Schwabenspelz" (mean for 2013–2015). NW I—number of weeds 3–4 weeks after herbicide treatment, WW I—air-dry weight of weeds 3–4 weeks after herbicide treatment, NW II—number of weeds at the dough stage of spelt wheat (BBCH 83–85), WW II—air-dry weight of weeds at the dough stage of spelt wheat (BBCH 83–85). Different letters denote significant differences (*p* ≤ 0.05). The same letter means not significantly different values.

On average over the period 2013–2015, seeding density was not found to have a significant influence on the number and dry weight of weeds in the cv. "Rokosz" the cv. "Schwabenspelz" crop at both times that weed infestation was evaluated (Figure 1). Nonetheless, it could be observed that a higher seeding density had a more beneficial effect on weed infestation, as demonstrated by the lower number and weight of weeds in the crop.

The analysis of the quantitative weed infestation parameters did not reveal significant differences in the number of weeds between the studied cultivars, but it proved a significantly lower biomass of weeds in the tall cultivar "Schwabenspelz". At the first evaluation of weed infestation, 3–4 weeks after herbicide treatment, the weed biomass in the crop of this cultivar was determined to be 15.64 g m−2 and it was 21% lower than for cv. "Rokosz". During the evaluation of weed infestation at the dough stage of spelt wheat, the difference in the biomass of weeds occurring in the crops of the cultivars studied was even greater, since for cv. "Rokosz" it was almost twice higher than for cv. "Schwabenspelz". At the first evaluation of weed infestation, *Viola arvensis*, *Geranium pusillum*, and *Apera spica-venti* were predominant in the spelt wheat crop (Figure 2a,b). In both cultivars, chemical crop protection significantly reduced the number of *Apera spica-venti* and *Viola arvensis* (Figure 2a). Seeding density did not cause differences in numbers of the dominant weed species in the crop (Figure 2b). At the dough stage (BBCH 83–85) of spelt wheat, the number of *Viola arvensis* plants was similar among all the treatments, while the number of *Apera spica-venti* was significantly lower on chemical crop protection treatments, compared to treatments A and B. (Figure 3a). In the cv. "Schwabenspelz", an increased seeding density reduced significantly the numbers of *Apera spica-venti* (Figure 3b).

≤ **Figure 2.** The impact of crop protection system on number of dominant weeds species 3–4 weeks after herbicide treatment in the spelt wheat cultivars "Rokosz" and "Schwabenspelz" (mean for 2013–2015). Different letters denote significant differences (*p* ≤ 0.05) of number of weed species among different crop protection methods (A, B, C, D) (**a**) and seeding density (**b**). The same letter means not significantly different values. ≤

≤ ≤ **Figure 3.** The impact of crop protection system on number of dominant weeds species at the dough stage (BBCH 83–85) in the spelt wheat cultivars "Rokosz" and "Schwabenspelz" (mean for 2013–2015). Different letters denote significant differences (*p* ≤ 0.05) of number of weed species among different crop protection methods (A, B, C, D) (**a**) and seeding density (**b**). The same letter means not significantly different values.

#### *3.2. Yield and Yield Components of Spelt Wheat*

On average over the three-year study period, the crop protection system did not cause significant differences in the yield components of the cultivar "Rokosz" (Table 4). The comparison of pro-ecological crop protection systems (A, B) and chemical crop protection did not reveal any significant differences in the yield components.

**Table 4.** The impact of crop protection system on selected yield components of the spelt wheat cv. "Rokosz" (mean for 2013–2015). HP—height of plant, LE—length of ear, NE—number of ears per m2 , WG—weight of grains per ear. The same letter means not significantly different values.

The statistical analysis showed cv. "Rokosz" grain yield to be significantly dependent on crop protection system and year (Table 5). In the first year of the experiment, the highest grain yield was obtained from the treatment where full chemical crop protection was used (treatment D). In the years 2014 and 2015, crop protection intensification did not contribute to increased yields of cv. "Rokosz". In 2015, higher yields were obtained in all crop protection treatments than in 2014, while treatments A, B, and C were higher than in 2013. The statistical analysis, performed based on the means for the three-year study period, revealed that the average grain yield from the chemical protection treatments (C, D) was 19.1% higher than in the pro-ecological treatments (A, B).

**Table 5.** The grain yield of the spelt wheat cv. "Rokosz". The interaction between crop protection and years of research, and comparison of the pro-ecological and chemical crop protection. Different letters denote significant differences (*p* ≤ 0.05).

As far as the analyzed yield components for cv. "Schwabenspelz" are concerned, the crop protection methods significantly modified plant height, but they had no effect on ear length, density, or grain weight per ear (Table 6). Wheat in the treatment that included only harrowing produced the highest plants (treatment B); the plant height was significantly lower in the treatment with full chemical protection (D). The different crop protection methods used did not affect yield of the spelt wheat cultivar "Schwabenspelz". The Scheffe test did not show significant differences in grain yield between pro-ecological technologies and chemical protection of the cv. "Schwabenspelz" crop.

**Table 6.** The impact of crop protection system on selected yield components and grain yield of the spelt wheat cv. "Schwabenspelz" (mean for 2013–2015). HP—height of plant, LE—length of ear, NE—number of ears per m2 , WG—weight of grains per ear, Y—yield for the crop protection methods A–D.

Different letters denote significant differences (*p* ≤ 0.05). The same letter means not significantly different values.

On average over the period 2013–2015, seeding density significantly modified only the ear length of the wheat cultivar "Rokosz", but significantly the highest value of this parameter was achieved at an optimal seeding density (Table 7). The seeding density factor did not cause significant differences in the other biometric characteristics and yield of cv. "Rokosz". Also, seeding density was not found to have a significant effect on the yield components and grain yield of cv. "Schwabenspelz".

**Table 7.** The impact of seeding density on selected yield components and grain yield of the spelt wheat cultivars "Rokosz" and "Schwabenspelz" (mean for 2013–2015). HP–height of plant, LE–length of ear, NE–number of ears per m2 , WG–weight of grains per ear, Y–yield.

Different letters denote significant differences (*p* ≤ 0.05). The same letter means not significantly different values.

Comparing the cultivars studied, it was found that the spelt wheat cultivar "Schwabenspelz" was characterized by significantly higher plants (by 22.7%) and longer ears (by 29.5%) relative to cv. "Rokosz". The comparison of the spelt wheat cultivars concerning the other biometric characteristics did not show significant differences. The grain yield of the spelt wheat cultivar "Rokosz" was significantly higher than that of cv. "Schwabenspelz", on average by 31.8%.

#### *3.3. Grain Health*

The results showed that the total number of fungi in cv. "Rokosz" grain ranged from 3.11 log CFU g−1 in treatment D with a increased seeding density to 3.87 log CFU g−1 in treatment A with an optimal seeding density, while in cv. "Schwabenspelz" grain ranged from 3.82 log CFU g−1 in treatment D with a higher seeding density to 4.46 log CFU g−1 in treatment B with an optimal seeding density (Figure 4a,b). In the grain with chemical crop protection (treatments C and D) in cv. "Rokosz" the total number of fungi was statistically significantly lower (*p* ≤ 0.05). The fungi *Penicillium* sp., *Penicillium expansum*, *Candida* sp., *Aureobasidium* sp., *Aspergillus* sp., *Aspergillus flavus*, *Aspergillus terreus*, *Cladosporium* sp., *Cladosporium cladosporides*, *Ulocladium* sp., *Fusarium* sp., *Rhodotorula* sp., *Rhizopus* sp., *Trichophyton* sp., and *Phoma* sp. were found in different ratio in spelt wheat (Figures 5 and 6). In cv. "Rokosz" grain, *Fusarium* sp. (19.4–76.7%) and *Aspergillus* sp. (11.9–38.9%) were the most

abundant species, while in cv. "Schwabenspelz" grain the most abundant were *Cladosporium* sp. (7.23–53.3%) and *Fusarium* sp. (4.76–38.5%).

**Figure 4.** Total number of fungi in the grain of spelt wheat cv. "Rokosz" (**a**) and cv. "Schwabenspelz" (**b**) (mean for 2014–2015). Note: \* crop protection methods, \*\* seeding density.

**Figure 5.** Identified mold fungi in the grain of spelt wheat cv. "Rokosz" (%) (mean for 2014–2015). Note: \* crop protection methods, \*\* seeding density.

**Figure 6.** Identified mold fungi in grain of spelt wheat cv. "Schwabenspelz" (%) (mean for 2014–2015). **Figure 6.** Identified mold fungi in grain of spelt wheat cv. "Schwabenspelz" (%) (mean for 2014–2015). Note: \* crop protection methods, \*\* seeding density.

Both total mycotoxin content and the content of individual toxins in spelt grain were modified by the crop protection system and seeding density (Tables 8 and 9). In cv. "Rokosz" grain, significantly the highest number of mycotoxins was found in treatment C after application of herbicide crop protection alone, while the lowest number of mycotoxins was recorded in treatment D (after application of the fungicide) (Table 8). In grain harvested from the pro-ecological treatments (A and B), the number mycotoxins was at a similar level, but the amount of DAS, DON, ZEA, HT-2, and 15-acDON mycotoxins differed significantly. A denser seeding resulted in reduced grain contamination with mycotoxins. In cv. "Schwabenspelz", the lowest number of mycotoxins was found in the treatment with full chemical crop protection (treatment D) (Table 9). In the other treatments, on the other hand, grain contamination with mycotoxins was at a similar level and significantly higher than in treatment D. Similarly as in the case of cv. "Rokosz", a denser seeding contributed to a decrease in the number of mycotoxins in grain.

Regardless of the experimental factors, the amount of mycotoxins in grain of the spelt wheat cultivars studied did not differ significantly. One can only observe slightly greater susceptibility of cv. "Rokosz" to contamination with mycotoxins. In grain of this cultivar, the amounts of DAS and DON mycotoxins and of HT-2 toxin were found to be significantly greater than in "Schwabenspelz". Cv. "Rokosz" was found to have the highest content of NIV, 3-AcDON, and DAS mycotoxins, while cv. "Schwabenspelz" had the largest amounts of 3-AcDON, NIV, and 15-AcDON.

**Table 8.** Mycotoxin content in wheat grain of the spelt wheat cv. "Rokosz" (concentration of mycotoxins µg kg−1 of grain) (mean for 2014–2015). NIV—nivalenol , DAS—diacetoxyscirpenol, 15- AcDON—15-acetyldeoxynivalenol, DON—deoxynivalenol, ZEA—zearalenone, 3-AcDON—3 acetyldeoxynivalenol.

Different letters denote significant differences (*p* ≤ 0.05). The same letter means not significantly different values.

**Table 9.** Mycotoxin content in wheat grain of the spelt wheat cv. "Schwabenspelz" (concentration of mycotoxins µg kg−1 of grain) (mean for 2014–2015). NIV—nivalenol, DAS—diacetoxyscirpenol, 15- AcDON—15-acetyldeoxynivalenol, DON—deoxynivalenol, ZEA—zearalenone, 3-AcDON—3 acetyldeoxynivalenol.

Different letters denote significant differences (*p* ≤ 0.05). The same letter means not significantly different values.

#### **4. Discussion**

Many authors indicate that the appropriate selection of a weed competitive variety is a major no-cost method of reducing weed infestation in crops [24,38–40]. In the opinion of Korres and Froud-Williams [41], as well as Mason and Spaner [42], high plants with intense tillering and forming a dense crop contribute to a reduced occurrence of weeds. This theory was confirmed by Kraska et al. [14], according to whom the selection of an appropriate cultivar had a significant impact on weed infestation of crops. Weeds produced significantly the lowest biomass in the tall spelt cultivar "Oberkulmer Rotkorn", while the highest biomass developed in the shortest spelt cultivar "Badengold". Although the research presented in this paper did not confirm statistically significant differences in the number of weeds found in the crops of the evaluated cultivars, at each time weed infestation was evaluated a significantly lower dry weight of weeds was determined in the tall cultivar "Schwabenspelz". Due to the higher competitive pressure of this cultivar, weeds were more shaded and had less space for growth, and hence they produced a lower biomass. Other research results confirm that spelt wheat is characterized

by high competitiveness against weeds, but they do not indicate unequivocally that this trait depends directly on plant height [24,43]. According to the study by Andruszczak et al. [40], the spelt cultivar "Frankenkorn", which was not significantly lower than many evaluated cultivars [43], was the most competitive against weeds, whereas according to Feledyn-Szewczyk [24] and Andruszczak et al. [39] the lowest weed infestation was found in the tall cultivar "Schwabenkorn" [43]. In the present study, the averages for the three-year study indicate that chemical crop protection (treatments C and D), based on its effect evaluated 3–4 weeks after application, significantly reduced the number and dry weight of weeds in the crops of both spelt wheat cultivars. The effect of the applied herbicide could be seen particularly in the first year of the study, in which the high rainfall in October caused intensive emergence of weeds. In 2014, the rainfall at the end of April and in May could have reduced the effectiveness of the herbicide. In the last year of the study, on the other hand, weed infestation of the crop was so low that the effect of herbicide action was not very visible. Herbicide application had no significant impact on weed infestation of cv. "Schwabenspelz" before harvest, but in the cv. "Rokosz" crop significantly lower weed infestation was shown in the treatments where herbicides were applied in comparison with the pro-ecological protection methods. In the studies by Andruszczak et al. [39,40], herbicide treatment significantly decreased the dry weight of weeds, but had no effect on their number. The results of the present study confirm the opinion of many authors who stress the low effectiveness of harrowing and its high dependence on weather conditions [44,45]. In the cv. "Rokosz" crop, weed infestation of the crop was not found to be significantly lower in the harrowing treatment compared to the control treatment in any year of the study. Nevertheless, in the first two growing seasons the number and biomass of weeds were slightly lower than in treatment A, whereas in 2015 weed infestation was slightly higher than in the harrowing treatment. In the cv. "Schwabenspelz" crop, harrowing also reduced weed infestation relative to the control treatment. According to Hansen et al. [46] and Lundkvist [47], the effectiveness of harrowing as a weed control method can be increased by performing this operation at an early time and repeating it two or three times, as well as by selecting weed-competitive crop plant cultivars. Despite the opinion of Korres and Froud-Williams [41] that an increase in seeding density of wheat contributes to reduced weed infestation of crops, this study did not demonstrate such a correlation for spelt wheat. It was attributable to the fact that a denser seeding did not cause a significant increase in ear density and therefore did not increase significantly the crop density.

The yield potential of crops is genetically driven and therefore selection of a variety with expected parameters is very important in crop production [14,22,32]. Moreover, in field cultivation a crop is affected by variable atmospheric conditions, which determine crop growth and development and, in consequence, yields obtained [16,22,28]. Spelt wheat is considered to be a species resistant to stress caused by adverse environmental conditions [25]. In the present study, the average grain yield for the period 2013–2015 was lower than those obtained by some researchers conducting studies in Poland [14,28]. This is due to adverse weather conditions in the first two years of the experiment, especially unevenly distributed rainfall in May and June, which contributed to the lower crop productivity. In a study by Wojtkowiak and St ˛epie ´n [28], the average yield of cv. "Schwabenkorn" in 2013 was 7.47 t ha−1 , while a year earlier it was 46% lower. Jablonskyte-Rašˇc ˙ e et al. [ ˙ 16] also found large differences in spelt yield in individual years of the study. This confirms the thesis that relatively small and unstable yields are a factor that limits the cultivation of spelt wheat [14]. Andruszczak [43] and Jablonskyte-Rašˇc ˙ e et al. [ ˙ 16] found spelt wheat yields at a similar level compared to that obtained in the present study. In the study by Andruszczak [43], the yield of cv. "Schwabenspelz" was higher than in the present experiment, standing at 4.18 t ha−1 . According to a study conducted by Glamoˇclija et al. [21] in Serbia, on the other hand, yields of organically grown spelt wheat were lower, ranging from 2.33 to 3.35 t ha−1 . The study by Pospišil et al. [48,49], on the other hand, demonstrates that agronomic factors have a great impact on spelt wheat yield.

In many papers, it is stressed that spelt wheat is tolerant to different growing conditions and does not require intensive protection [9,21]. The results of conducted research indicate that the effect of crop protection intensification on this species' yield is dependent on the variety. In the case of the Polish cultivar "Rokosz", a 19% higher yield was obtained after application of chemical crop protection (C, D) compared to pro-ecological cropping (A, B). Cv. "Schwabenspelz", on the other hand, did not respond with a substantial increase in yield after application of crop protection products, but the yields obtained were slightly higher than for the pro-ecologically grown crop. Andruszczak [43] demonstrated that crop protection intensification had a beneficial effect on the productivity of spelt wheat, whereas in the research carried out by Pospišil et al. [48] the impact of fungicide application on spelt wheat varied between years.

Similar to the studies conducted by Andruszczak [4] and Pospišil et al. [48,49], in the present experiment seeding density did not have a significant effect on most of the yield components and yield of spelt wheat. This finding is related to the phenomenon of the so-called crop self-regulation, due to which the number of plants per unit area is not directly proportional to the seeding rate. With increasing seeding rate, the phenomenon of self-regulation of the number of plants in a crop intensifies in order not to allow excessive density. At lower seeding densities, the tillering ability of the crop increases [12].

Wheat grains are colonized by various fungi, including plant pathogens and mycotoxin-producing species. The species composition of seed-colonizing fungi can be modified by various agronomic practices and weather conditions [23,50,51]. In this study, spelt grain was colonized by many fungi, but mainly by *Fusarium* sp., *Cladosporium* sp., and *Aspergillus* sp. The main mycotoxin producers are fungi of the genera *Aspergillus*, *Penicillium*, and *Fusarium* [52,53]. Species of the genus *Fusarium* differ in their epidemiology, pathogenicity, and ability to produce mycotoxins. Most *Fusarium* species can produce one or more mycotoxins exhibiting different degrees of toxicity [54,55]. Deoxynivalenol (DON), T-2, HT-2, and nivalenol (NIV) are the most common in cereals [56,57]. In the spelt grain evaluated, similar to products investigated by Serrano et al. [58], the mycotoxin NIV was found to have the highest content. In the opinion of Serrano et al. [58], special attention should be paid to this mycotoxin due to the toxicological effects of its occurrence and its large amount in cereal products. Spelt wheat is characterized by a higher level of resistance to fungal ear and grain infections than common wheat [8,59]. In grain of the spelt cultivars studied, all nine mycotoxins were found to occur, whereas Juan et al. [60] identified in spelt only four mycotoxins: DON, NIV, fuzarenon X (FUS-X), and enniatin A (EN A), whose amounts were comparable to the content of these compounds in the cultivar "Schwabenspelz". According to Mankeviˇciene et al. [ ˙ 23], lower DON, ZEA, and T-2/HT-2 concentrations were found in spelt grain without glumes than in spelt grain with glumes, in glumes, and in spring wheat grain. Likewise, Vuˇckoviˇc et al. [8] detected higher levels of mycotoxins in hulls compared to grains. Conditions that are most favorable for the development of fungi and contamination of grain with mycotoxins include high humidity, frequent rainfall, particularly before harvest, and relatively warm night temperatures [61,62]. In the opinion of Blandino et al. [63,64], high plant density is associated with higher grain infection, while in the present study, grain of both cultivars contained fewer mycotoxins under conditions of denser seeding compared to less dense seeding. Such results could have been attributable to several factors. Firstly, the denser seeding did not cause an increase in ear density in the crop. Furthermore, despite that it was not confirmed statistically, under conditions of the higher seeding rate, the weed infestation of the crop before harvest of spelt wheat was slightly lower. Weeds occurring in the crop significantly affect crop health because they can change moisture conditions in the crop and host disease-causing fungi [65]. Lower infestation of spelt wheat resulted in lower fungal infection of grain and thus contributed to lower mycotoxin content. The effect of plant density on the amount of mycotoxins was investigated by many authors, but due to the diversity of factors affecting grain infection, their results are not unambiguous [66–68]. Mycotoxin content also depends on the cultivar [67,69]. In grain of both cultivars, in line with the expectations, the lowest amount of mycotoxins was found in the treatment with fungicide application. In cv. "Rokosz", most mycotoxins were found after application of the herbicide alone (treatment C). In cv. "Schwabenspelz", the amount of mycotoxins in grain obtained from treatments A, B, and C was

at a similar level. Grain of the evaluated spelt wheat cultivars, both in the pro-ecological treatments (A and B) and in the treatments with application of crop protection products, can be considered as safe and good because the content of individual mycotoxins did not exceed the maximum levels set for grain intended for food and animal feed purposes [70].

#### **5. Conclusions**

The present study showed how production intensification affected the productivity, weed infestation, and grain health of the spelt wheat cultivars "Rokosz" and "Schwabenspelz". The cultivar "Rokosz" was significantly less infested with weeds and produced significantly higher yields under chemical crop protection conditions than in the case of pro-ecological crop protection. The effect of crop protection methods on the quantitative weed infestation parameters and yield of this cultivar varied between years. Grain harvested from the treatment with herbicide application alone was characterized by the highest contamination with mycotoxins, while it was found to be lowest in the case of grain of grain harvested from treatment D. In the case of the cultivar "Schwabenspelz", no significant differences in yield were revealed between the pro-ecological and chemical crop protection treatments, and the effect of crop protection treatments on yield was not dependent on weather conditions. Cv. "Schwabenspelz" proved to be more competitive to weeds. At the dough stage of this crop plant, no significant differences in weed infestation were found between the pro-ecological treatments and those in which an herbicide was used. The lowest content of mycotoxins was determined in grain harvested from treatment D. In cv. "Schwabenspelz" grain, in comparison with the cultivar "Rokosz", the amount of mycotoxins DAS, DON, and HT-2 was determined be significantly lower, while the mycotoxin ZEA was not found at all.

Seeding density did not have a significant effect on most of the yield components, yield, and weed infestation of the spelt wheat crop. In both cultivars investigated, a higher seeding density contributed to reduced grain contamination with mycotoxins.

Due to the favorable response of the cultivar "Rokosz" to application of chemical crop protection, it is advisable to grow this species in conventional farms using integrated crop protection. The cultivar "Schwabenspelz", on the other hand, can be recommended for cultivation in organic farms on account of its competitive ability and resistance.

**Author Contributions:** The authors contributed to this article in the following ways—conceptualization: M.H., D.G., and B.N.-D.; data curation: D.G., S.C., and J.Ł.; formal analysis: M.H., D.G., B.N.-D., A.N., Ł.W., and M.R.-B.; funding acquisition: M.H.; investigation: M.H., D.G., B.N.-D., and A.N.; methodology: M.H., D.G., B.N.-D., A.N., and Ł.W.; project administration: M.H.; supervision: M.H. and D.G.; writing—original draft: M.H., D.G., B.N.-D., S.C., and J. Ł.; writing—review and editing: M.H., D.G., S.C., and M.R.-B. All authors have read and agreed to the published version of the manuscript.

**Funding:** Research supported by the Ministry of Science and Higher Education of Poland as the part of statutory activities of Department of Herbology and Plant Cultivation Techniques, University of Life Sciences in Lublin.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).


**Preface XI**

Chapter 8 **High-Porosity Metal Foams: Potentials, Applications, and Formulations 181** Ahmed Niameh Mehdy Alhusseny, Adel Gharib Nasser and Nabeel M J Al-zurf

Preface

Given their practical importance in improving the general or specific properties, the porosity in materials has been extensively investigated and prepared in the recent decades with vari‐ ous techniques. The preparation techniques can be mechanical, chemical, or electrical, such as electrical discharge machining (EDM) and electrochemical anodization process. Several sci‐ entists have been oriented toward the production of well-spaced and well-organized nano‐ metric and micrometric pores, which constitute a technological revolution useful for a wide variety of applications. Nowadays, numerous studies have been focused on the effect of po‐ rosity by exploring the effect of pore size, shape, and density with the goal to enhance some surface or volume properties, such as heat capacity, thermal conductivity, gap energy, optical absorption, optical emissivity, and mechanical hardness. Several techniques are used in the characterizations of the porous materials, such as scanning electron microscopy (SEM); atom‐ ic force microscopy (AFM); transmission electron microscopy (TEM); X-ray diffraction (XRD) for the imagining and structural characterization; and the photoluminescence (PL), ultravio‐

let-visible (UV-VIS), and infrared (IR) spectroscopy for the optical characterization.

layers on the total properties; and to give more ways to use them in different fields.

The purpose of this book is to present various techniques for the production of pores on the surface and the volume of different materials; to investigate the influence of some parame‐ ters, such as the anodizing current, the annealing temperature, the heating time, the chemi‐ cal composition and concentration, and the nature of some additive and deposited thin

**Taher Hcine Ghrib**

Dammam, Saudi Arabia

College of Science of Dammam

Imam Abdulrahman Bin Faisal University


**3. Results and Discussion**

*3.1. Properties in a Fresh State*

3.1.1. Consistency

Table 6 shows the results of consistency, entrained air content and density of the concretes designed. Regarding consistency, all mixes were within the target design workability (50 ≤ S2 ≤ 90 mm), which reveals that adding the mixed recycled fine and/or coarse fraction does not have a negative effect on this property. This result is in line with Plaza et al. [18] who observed that the simultaneous addition of recycled concrete aggregate and concrete or mixed sand does not lead to a decline in the workability of recycled concretes. This behaviour is in line with Agrela et al. [23] and Medina et al. [29] who respectively suggested, as strategies to mitigate the negative effect that the higher water absorption of recycled aggregates has on this property, to pre-saturate them before the mixing process or to add the water initially absorbed by these recycled aggregates to the dosage.

**Table 6.** Concrete properties in a fresh state.

Figure 4 shows the concrete slump test of conventional concrete (M1) and concrete with a higher content of MRA, highlighting that the individual or simultaneous use of the fractions does not have a negative effect on this property.

**Figure 4.** Concrete slump test: (**a**) Concrete with 100% NA (M1) and (**b**) Concrete with 50% fMRA and cMRA (M9).

#### 3.1.2. Entrained Air

Table 6 lists the amount of entrained air in fresh concrete, revealing that the addition of fine and/or coarse MRA caused an increase in this property, with the value for M3 (50% fMRA), M7 (50% cMRA), M8 (25% fMRA + 50% cMRA) and M9 (50% fMRAf 50% cMRA) being 1.9, 1.4, 2.1 and 2.79 times higher than that registered for mix M1 (100% NA), respectively. This performance could be connected with [49,50] (i) higher water absorption by the MRA, (ii) lower density of the adhered mortar present in the recycled aggregate

due to the presence of air bubbles within, (iii) the rougher texture of MRA compared with NA and (iv) the presence of microcracks inside the MRA which are not connected to the aggregate's permeable pores. These results are in line with the observations by Cantero et al. [30] and Plaza et al. [18], who registered an increase of this property when adding contents of up to 100% MRA and 100% RCA, respectively.

Figure 5 reveals the linear relationship that exists between this property and the percentage of recycled sand for different percentages of coarse aggregate replacement (0%, 25% and 50%), with all cases having an *R*2 ≥ 0.99. This trend was previously registered by Yaprak et al. [49], who added from 0% to 100% of recycled concrete sand.

**Figure 5.** Connection between the percentage of mixed recycled sand and entrained air.

### 3.1.3. Density

Table 6 lists the density values for fresh concrete. It reveals a decrease of said property in connection with the percentage of addition of mixed recycled aggregate (fMRA and/or cMRA). These decreases reached their maximum value in mixes that had both fractions added at 50% simultaneously; as for mixes M8 and M9, these values were 5.4 and 5.3 compared with mix M1, respectively. This was also the case with the mix that added 25% cMRA + 50% fMRA (M6), with a 5.8% decrease compared with M1. This decrease is in line with Brito et al. [50], who registered decreases of up to 10% for concretes that had up to 100% of MRA. This behaviour would be connected with the lower density of recycled aggregates due to the presence of adhered mortar and ceramic material, as well as the apparent higher water/cement ratio of the new concrete mixes designed [49,51].

Regarding the values obtained, it is worth noting that they were within the 2430–2300 kg/m3 and 2430–2220 kg/m3 ranges of values for concretes that have different percentages of recycled concrete aggregate [52,53] and mixed recycled aggregate [51], respectively. Lastly, this observed trend is in line with research previously registered by other authors: Plaza et al. [18] registered densities of 2428.56 kg/m3 for conventional concretes, 2367.38 kg/m3 for concretes with a 100% coarse aggregate replacement rate and 2310.51 kg/m3 for mixes with 100% recycled coarse aggregate replacement and 50% fMRA; César Medina et al. [52] registered a density of 2347 kg/m3 with 25% of cMRA replacement and densities of 2335 kg/m3 with 50% cMRA replacement. A. González et al. [51], with

high-performance recycled concrete aggregates with 20% and 50% cMRA replacement, obtained densities of 2430 kg/m3 and 2340 kg/m3, respectively.

#### *3.2. Properties in a Hardened State*

3.2.1. Density

Table 7 lists the values of apparent density in hardened concretes analysed following 28 days of curing, once again revealing a decrease of this property with the percentage of addition of MRA (fMRA and/or cMRA), due to the lower density of this new typology of recycled aggregates compared with natural aggregates (Table 2). This decrease was between 1.4% and 5.7% compared with the reference concrete (M1). In this context, it is worth noting that said decrease is in line with the 3.3–5.0% range registered by other authors who added up to 100% of MRA [49]. Regarding the values obtained, it is worth stressing that they are within the range of values (2450–2270 kg/m3) registered previously by other authors who added mixed recycled aggregates [10,29,30].

**Table 7.** Density and compressive strength evolution.

Note. D28d: density in a hardened state after 28 days; σ: standard deviation; acs7d: average compressive strength after seven days; acs28d: average compressive strength after 28 days; acs90d: average compressive strength after 90 days. acs average compressive strength with a cubic sample, which must be multiplied by 0.90 to turn it into a cylindrical sample of 150 φ × 300 mm.

#### 3.2.2. Compressive Strength

Table 7 shows the evolution of the compressive strength of the various mixes analysed after 7, 28 and 90 days. It shows that regardless of the type of concrete, (i) compressive strength increases with the curing time, an evolution which is very similar to that displayed by the reference concrete, (ii) the relative compressive strength after seven days is 75.7–83.6% of that obtained after 28 days, a similar percentage to the figure obtained (70%) in Portland cement concretes with no additions and a w/c ratio <0.45 [54] and to the 65–93% range of values registered by Bravo et al. [16] for concretes that partially added C&DW, and (iii) the average strength after 28 days is higher than the design strength of 25 MPa. Therefore, these new recycled concretes could be used as concretes for structural use.

Figure 6 shows the compressive strength variation of recycled concretes compared with conventional concrete for the various curing times. It reveals that for short times (t < 28 days), the addition of fMRA and/or cMRA caused a maximum performance loss of 10.7% compared with M1 and was suffered by the mix that had 50% fMRA + 50% cMRA (M9). However, at t = 90 days there was an increase in strength. The maximum increase was +19% over M1, observed in the mix that had 25% fMRA (M2). Likewise, concretes with 50% cMRA and 0%, 25% and 50% fMRA (M7–M9) had a better behaviour, recording increases ranging from 8.4% to 12.4% compared with M1.

**Figure 6.** Compressive strength variation of recycled concretes (M2–M9) compared with conventional concrete (M1).

These results reveal that the addition of cMRA individually (M4–M7) does not have a negative effect on this attribute, registering a small decrease (ΔM4 = −3.8%/ΔM7 = −5.6%) and a slight increase (ΔM4 = +3.5%/ΔM7 = 8.4%) compared with M1 after 28 and 90 days, respectively. This performance is in line with the observations of Cantero et al. [30], Poon et al. [54], Gomes et al. [55] and Lotfy et al. [56], who revealed that for recycled coarse aggregate replacement percentages ≤ 50%, there are no significant differences with conventional concretes.

Regarding the individual addition of fMRA (M2 and M4), we observed that the addition of 25% in weight (M2) led to a slight increase in compressive strength, reaching +3.8% and +19.1% compared with M1 after 28 and 90 days, respectively. This behaviour is in line with the study of Bravo et al. [10], who established that type I recycled fine aggregates (Rc + Ru ≥ 80% and other components ≤20%) caused variations in compressive strength ranging from +3.8 to −12.5 after 28 days and in concretes with a replacement percentage of 25%. Likewise, this result was also obtained by other authors [57–60], who registered 3.7%, 5% and 16% increases compared with conventional concrete for 10%, 30% and 50% additions of RCA, respectively. This increase was connected with the filler effect of fine RCA and their rough texture and shape, which allowed for a better packing of the granular skeleton [61,62].

Regarding the 50% fMRA replacement (M3), the study showed that after 28 days the resistance remained constant, whereas after 90 days, there was a slight increase of +8.1% compared with M1. This behaviour is better than that established by Bravo et al. [63] for a 50% replacement with type-I sand comprised by Rc + Ru = 83.7%, Rb = 0.9% and Rg = 15.4. These authors registered an attribute loss ranging from −6.1% to −13.3% compared with conventional concrete, for a 50% percentage of replacement. This improved behaviour of M3 is linked to the better quality of fMRA (Table 2) compared with the type-I sand studied by said authors.

Likewise, Figure 5 reveals that mixes M5, M6, M8 and M9, which simultaneously incorporated cMRA (25% and 50%) and fMRA (25% and 50%) in their composition, had a worse performance after 28 days, registering a 5.5%, 5.0%, 8.0% and 1.4% decrease compared with M1, respectively. These decreases are lower than the ~7% and ~17% observed by Plaza et al. [18], who added 50% coarse RCA + 50% fine RCA and 50% coarse RCA + 50% mixed sand, respectively. In addition, it is worth noting that similar to when MRA were added individually, an improved performance was registered for the concretes after 90 days of curing, with mix M9 (cMRA = 50% + fMRA = 50%) reaching a maximum increase of 12.4% compared with M1.

This improved behaviour of the new concretes (M2–M9) at curing times greater than 28 days could be connected with the pozzolanic activity of the fine fraction (sizes < 0.063 mm) present in fMRA, where there are mainly ceramic fines. This aspect was previously registered by Medina et al. [60,61] and Asensio et al. [62,63], who analysed the pozzolanic performance of the fine fraction of C&DW with variable compositions (26.5% ≤ SiO2 ≤ 70.5%, 4.4% ≤ CaO ≤ 24.5%, 5.8% ≤ Al2O3 ≤ 18.5%), observing that they have a lime fixation capacity after 28 days of 53.3–82.1%. These values are lower than silica fume (~90%) and higher than fly ash (~45%).

In addition, this behaviour could also be linked to (i) the presence of anhydride cement particles [64–66] in the mortar adhered to the fMRA that will become hydrated, generating calcium silicate hydrate (C-S-H) which will positively contribute to the mechanical behaviour and (ii) the attributes of existing ITZs among the Rb components of MRA (cMRA and fMRA)/paste that can have a thickness equal to or lower than the one that natural aggregates normally have (eITZ = 10–50 μm), as shown previously in the studies by Medina et al. [29] and Sáez del Bosque et al. [24] in concretes that had coarse fractions of ceramic aggregate from bathroom fittings and coarse mixed recycled aggregate, respectively.

Figure 7 shows the appearance of concretes M1, M3, M6 and M9 after being subjected to the compression test after 28 days, revealing that the type of failure was similar in all of them and that their morphology can be classified as suitable according to European standard EN 12390-3 [65,67].

**Figure 7.** Type of failure of the concretes: (**a**) M1; (**b**) M3; (**c**) M6; and (**d**) M9.

Lastly, Figure 6 verifies that the aggregate/paste ITZ is the area where the cracks preferentially begin and then spread when a concrete item is subjected to an external force that surpasses its operational status limit [68]. This happens because this area is the weakest and the one where the most stress concentrates, as observed by Medina et al. [67] by simulating the stress in the coarse/paste aggregate ITZ subjected to compressive forces [69].

#### 3.2.3. Splitting Tensile Strength

Table 8 shows the tensile strength of concretes tested after 28 days and the variations in strength compared with conventional concrete (M1) and compared with the concretes that exclusively had cMRA (M4 and M7). It reveals that the mixes that only had fMRA (M2 and M3) experienced a slight increase in tensile strength between 8.7% and 5.5% compared with M1, respectively. This behaviour is in line with the observations of Ahmed et al. [68] and Kirthika et al. [69], who revealed that the use of fine MRA in percentages lower than 50% did not lead to a significant loss of performance (<10%) in the new concretes.

**Table 8.** Tensile and flexural strength of concretes 28 days later.

Note. fcmt: mean splitting tensile strength; fcmf: mean flexural strength; ♣ strength variation compared with M1; ♠ strength variation compared with M4; and \* strength variation compared with M7.

Regarding the mixes whose composition included 25% cMRA (M4) and 50% cMRA (M7), it is worth noting that they registered a small decrease of 7.0% and 4.6% compared with M1, respectively. These losses are similar to those registered by Cantero et al. [30] in concretes with 25% and 50% of mixed recycled aggregate and lower than the 12% and 14% losses registered previously by other authors who [70–75] analysed concretes with 100% of recycled aggregates, which had 10% ≤ Rb ≤ 14%.

Regarding the mixes that include both fractions simultaneously, we observed that the addition of fMRA had a positive effect by (i) lessening the decrease in strength of the mixes (M5, M6, M8 and M9) compared with the mixes that only included cMRA (M4 and M7), with the decrease reaching 1.45% ≤ Δfcmt ≤ 4.06%, and (ii) increasing their strength compared with mixes that only had cMRA (M4 and M7), with this change ultimately being 3.12% ≤ Δfcmt ≤ 6.23%. This behaviour is better than that observed previously by Plaza et al., who registered a 7.3% and 11.0% decrease compared with conventional concrete in concretes with 25% coarse RCA + 50% fine MRA and 50% coarse RCA + 50% fine MRA, respectively. This same tendency was revealed for concretes with 50% coarse RCA + 50% fine RCA, again registering decreases ~11% compared with conventional concrete [76].

Lastly, it is worth noting that the failure mechanism was the same in all tested concretes, causing a brittle failure that led to the tested mixes splitting in half. In addition, we observed that (i) the failure surface obtained is irregular, confirming the existence of intact coarse aggregates (cNA or cMRA) and thus again revealing that the failure emerges from the ITZ of the coarse and/or fine aggregates and the cement paste, and (ii) the granular skeleton (fine and coarse aggregates) is distributed homogeneously, regardless of whether the aggregate is natural or recycled (Figure 8).

**Figure 8.** Appearance of the concretes when performing the tensile test 28 days after producing the mortar: (**a**) conventional concrete (M1) and (**b**) concrete with 50% cMRA + 50% fMRA (M9).

#### 3.2.4. Flexural Resistance

Table 8 lists the flexural strength values of the tested concretes after 28 days, and the variations in strength compared both with conventional concrete (M1) and with the concretes that exclusively had cMRA (M4 and M7). It reveals that the mixes that only had fMRA (M2 and M3) experienced a slight increase in flexural strength of +8.9 and +8.6% compared with M1, respectively. This result is in line with the prior observations of Ahmed [76] and Kirthika [77], who registered 6.7% and 3.2% increases compared with conventional concrete for a fine MRA replacement percentage of 50%, respectively.

Regarding mixes with 25% cMRA (M4) and 50% cMRA (M7), it is worth noting that they displayed an uneven behaviour, with mix M4 registering a 7.3% increase compared with M1 and M7 showing a 3.4% decrease compared with M1. This behaviour was similar to that observed by Cantero et al. [30], who established that for replacement percentages lower than or equal to 50% of coarse MRA, there were no significant variations of this mechanical attribute (Δfcmf ≤ 10% compared with conventional concrete).

Regarding the mixes that simultaneously incorporate both fractions, we observed that the addition of fMRA had a positive effect by improving the behaviour of mixes with cMRA (M4 and M7). It is worth noting that mixes M5 and M6 registered a 4.4% and 2.7% increase compared with M4, and mixes M8 and M9 showed a 3.8% and 10.0% increase compared with M7. Likewise, all of them had a similar or improved behaviour compared with that observed in conventional concrete with 100% natural aggregate (cNA and fNA).

Lastly, all samples tested, regardless of the composition of their granular skeleton, had failures due to the formation of a crack in the middle part of the span, rising from the part being pulled (the lower part of the sample) to the part being compressed [77] (the highest part where the load is applied). Likewise, observing the cracked area, we once again saw that the failure took place along the aggregate/paste transition area, with the aggregates being detached from the matrix.

#### 3.2.5. Water Penetration Depth under Pressure

Figure 9 shows the results obtained regarding the maximum and mean depth of the mixes analysed.

**Figure 9.** Water penetration of the concretes under pressure. Limits established in EHE-08 and EC-2 (Note. IIIa: marine class—subclass: aerial; IIIb: marine class—subclass: submerged; IIIc: marine class—subclass: tidal and splash zones; Qa: aggressive chemical class—subclass: weak; Qb: aggressive chemical class—subclass: average; Qc: aggressive chemical class—subclass: strong; H: with frost class—subclass: without deicing salts; and F: with frost class—subclass: without deicing salts).

Regarding the individual incorporation of fMRA (M2 and M3), we observed that these mixes experienced a larger decrease both in maximum (Pmax) and mean (Pmed) water penetration, with the decrease ending up being between 16.1% ≤ Pmax ≤ 44.6% and 47.7% ≤ Pmed ≤ 52.9% compared with conventional concrete (M1). This greater watertightness could be connected with the pozzolanic activity of ceramic fines (<0.063 mm) of the fMRA, as well as with the hydration of anhydrous cement [78] present in the fines from fMRA mortars that give them a certain hydraulic activity and thus lead to a more sealed and tortuous pore structure.

Regarding the use of cMRA, we observed that an addition of 25% (M4) and 50% (M7) caused an uneven behaviour in these two properties. In the case of M4, the table shows that Pmax and Pmed experienced a slight (2.8%) and small (20.1%) decrease compared with M1, respectively. This behaviour is in line with the prior observations of Mas et al. [77], who observed that the depth remained constant for coarse MRA replacement percentages ≤25%. Regarding mix M7, it experienced an increase of Pmax (2.4%) and a slight decrease of Pmed (6.4%). This behaviour could be connected with the fact that the microcracks present in MRA have a greater impact on Pmax than Pmed.

Regarding the simultaneous use of cMRA and fMRA as the granular skeleton of the concretes, the table shows that only the 25% cMRA + 25% fMRA mix (M5) made it possible to obtain an increase in water penetration, causing a 35.8% and 33.9% decrease in Pmax and Pmed compared with M1, respectively. This result, as happened with the other properties studied, makes it possible to say that there is no performance loss for MRA replacement percentages lower than or equal to 25%.

In this context, it is worth noting that for weight percentages of cMRA and fMRA greater than 25%, there was an increase in water penetration, which could be explained by the beneficial effect of its rougher surface texture enabling a better entry (similar ITZs) in the cement matrix, as well as the pozzolanic activity of the <0.063 mm fraction not being able to compensate for the negative effect that its intrinsic properties have on water penetration (lower density, higher water absorption and the presence of microcracks in its microstructure).

The values obtained are under the limits established in chapter VII "Durability" Section 37.3.3 "Resistance to water penetration" of the Spanish Code on Structural Concrete (EHE-08), which establishes that a concrete is watertight enough for a given type of exposure (IIIa, IIIb, IIIc, IV, Qa, E, H, F, Qb, Qc) when its maximum and mean penetration depth is lower than 50 or 30 mm and 30 or 20 mm, respectively, depending on the type of environment (see Figure 9). This highlights that recycled concretes have a porous structure that guarantees watertightness and a suitable durability throughout their useful life against this transport mechanism.

Lastly, Figure 10 shows the penetration front of the samples manufactured for concretes M1, M3, M6 and M9. As can be seen, the water penetration outlines have a similar morphology, and there are no visible differences between the mixes manufactured with NA and cMRA and/or fMRA.

**Figure 10.** Penetration fronts of the concretes: (**a**) M1; (**b**) M3; (**c**) M6; and (**d**) M9.

3.2.6. Analysing the Concrete Manufacturing Costs

Table 9 lists the economic study of the cost of manufacturing the concretes analysed in order to reveal the financial aspects of this study. In this context, it is worth noting that the price of natural aggregates in Spain is lower than in other countries, as this country is characterised by having a high availability of natural resources, which enables the extraction of natural aggregates. These prices (EUR/t) will be much higher in countries with greater legal restrictions on extracting natural resources or with less availability, which would facilitate the recovery of recycled aggregates in the concrete industry from an economic point of view. This table shows that mix M9, with 50% fMRA + 50% cMRA, is the cheapest, leading to a −8.03% decrease compared with natural aggregate (M1). This result is in line with the prior observations of other authors, who registered decreases of under −50% for recycled coarse aggregate replacement percentages between 50% and 100% [78].

**Table 9.** Manufacturing cost of the mixes studied.

Lastly, in addition to these economic savings, one must consider the positive environmental effect, especially in terms of kgCO2eq/kg, that the correct management of MRA and a decrease in the extraction of natural aggregates entail.

#### **4. Conclusions**

The conclusions drawn from this research study are:

**Author Contributions:** Conceptualisation, M.D.G., P.P.C., D.B.F., M.M.J.V., I.F.S.d.B. and C.M.M.; methodology, M.D.G., I.F.S.d.B. and C.M.M.; formal analysis, M.D.G., P.P.C. and I.F.S.d.B.; investigation, M.D.G., P.P.C., D.B.F., M.M.J.V., I.F.S.d.B. and C.M.M.; writing—original draft preparation, M.D.G., P.P.C. and D.B.F.; writing—review and editing, M.D.G., M.M.J.V., I.F.S.d.B. and C.M.M.; supervision, D.B.F., I.F.S.d.B. and C.M.M.; project administration, D.B.F. and C.M.M.; funding acquisition, C.M.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was funded by the Spanish Ministry for Science and Innovation under coordinated research project PID2019-107238RB-C21/AEI/10.13039/501100011033 and in conjunction with the Government of Extremadura under grant GR 18122 awarded to the MATERIA research group. The authors are grateful to the "Programa de Formación de Capital Académico Avanzado", Universidad Tecnológica Metropolitana Grant: PM-VRAC2020 UTEM, for the financial support.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data sharing not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

**Nicole Meinusch 1,\*, Susanne Kramer 2, Oliver Körner 2, Jürgen Wiese 3, Ingolf Seick 3, Anita Beblek 4, Regine Berges 4, Bernhard Illenberger 5, Marco Illenberger 5, Jennifer Uebbing 6, Maximilian Wolf 1, Gunter Saake 7, Dirk Benndorf 1,8, Udo Reichl 1,9 and Robert Heyer 1,\***

**Abstract:** The integration of closed biomass cycles into residential buildings enables efficient resource utilization and avoids the transport of biowaste. In our scenario called Integrated Cycles for Urban Biomass (ICU), biowaste is degraded on-site into biogas that is converted into heat and electricity. Nitrification processes upgrade the liquid fermentation residues to refined fertilizer, which can be used subsequently in house-internal gardens to produce fresh food for residents. Our research aims to assess the ICU scenario regarding produced amounts of biogas and food, saved CO2 emissions and costs, and social–cultural aspects. Therefore, a model-based feasibility study was performed assuming a building with 100 residents. The calculations show that the ICU concept produces 21% of the annual power (electrical and heat) consumption from the accumulated biowaste and up to 7.6 t of the fresh mass of lettuce per year in a 70 m2 professional hydroponic production area. Furthermore, it saves 6468 kg CO2-equivalent (CO2-eq) per year. While the ICU concept is technically feasible, it becomes economically feasible for large-scale implementations and higher food prices. Overall, this study demonstrates that the ICU implementation can be a worthwhile contribution towards a sustainable CO2-neutral society and decrease the demand for agricultural land.

**Keywords:** integrated cycles for urban biomass; biogas; carbon footprint; sustainability; renewable energy; plant cultivation; feasibility study; simulations; CO2-neutral society


**2. Hydrothermal lignin: aromatic hydrocarbons from woody biomass**

### **2.1 Reducing molecular weight of lignin**

Lignin is one of main components of lignocellulosic biomass and a natural phenolic polymer with propyl-phenol groups. One big drawbacks of natural lignin in originally existing woody biomass is large molecular weight (because high molecular weight lignin has high viscosity or it is solid at room temperature and it has a complicated structure), and molecular weight reduction of lignin will provide many advantages in handling and processing as a chemical feedstock. In the paper [2], we proposed an environmental-friendly process for recovery of lignin from woody biomass, and it should have high efficiency with producing simple structure lignin, which is highly desired as a biorefinery feedstock. Here, the brief introduction of the process and the index of the operational parameters (how to know the optimum conditions) is summarized.

### **2.2 Experimental for hydrothermal lignin preparation**

In the paper [2], low-grade wood from Japanese cedar production was provided from a domestic wood manufacturer and had a lignin content of 44.6 wt% (the sample should be mainly bark of the Japanese cedar). The bark was crushed to have a coarse particle size of less than 5 mm. The elemental balance of the Japanese cedar *Resource Upgrading in Advanced Supercritical Fluid (Supercritical Fluid with Catalyst… DOI: http://dx.doi.org/10.5772/intechopen.89793*

### **Figure 2.**

ionic liquid as cosolvent: reduction of viscosity of ionic liquid solution [26], control of acidity and basicity of ionic liquid, solubility control of material in ionic liquid, separation of target molecule from ionic liquid into supercritical fluids, and so on. Our research group also progress the study of the separation of some components (biomass molecules or biomass refinery are targeted) from ionic liquid solution with supercritical carbon dioxide [27–30]. Here, we only briefly introduced some research results concerning biomass conversion into useful molecule in ionic liquid-

*Proposed process for liquid fuel production from protein-rich biomass by hydrothermal conversion together with*

In the conclusion of this chapter, we will conclude this chapter and mention

**2. Hydrothermal lignin: aromatic hydrocarbons from woody biomass**

Lignin is one of main components of lignocellulosic biomass and a natural phenolic polymer with propyl-phenol groups. One big drawbacks of natural lignin in originally existing woody biomass is large molecular weight (because high molecular weight lignin has high viscosity or it is solid at room temperature and it has a complicated structure), and molecular weight reduction of lignin will provide many advantages in handling and processing as a chemical feedstock. In the paper [2], we proposed an environmental-friendly process for recovery of lignin from woody biomass, and it should have high efficiency with producing simple structure lignin, which is highly desired as a biorefinery feedstock. Here, the brief introduction of the process and the index of the operational parameters (how to know the

In the paper [2], low-grade wood from Japanese cedar production was provided from a domestic wood manufacturer and had a lignin content of 44.6 wt% (the sample should be mainly bark of the Japanese cedar). The bark was crushed to have a coarse particle size of less than 5 mm. The elemental balance of the Japanese cedar

hydrothermal water mixture with additives (Section 4).

**2.1 Reducing molecular weight of lignin**

*Advanced Supercritical Fluids Technologies*

optimum conditions) is summarized.

**92**

**2.2 Experimental for hydrothermal lignin preparation**

outlook in this field.

**Figure 1.**

*"iso-conversion."*

*Coupled system of two batch reactors.*

was 49, 5.9, 0.1, 1, and 42.2 wt% for C, H, N, S, and O content, respectively. Ash content was 2 wt%.

A coupled system of two batch reactors was used (the photograph and schematic diagram of the reactor is shown in **Figure 2**, and its detail can be seen elsewhere [2]), and the sample was loaded into the upper reactor. The lower reactor was reservoir and used to recover hydrothermal extracts. The reservoir was maintained at a temperature of 473 K to inhibit the aggregation of lignin because lignin typically is melted into liquid phase at temperatures greater than 423 K in the presence of water [31]. Typically, a 7.5 g sample of bark (covered with stainless mesh) was loaded in the upper reactor along with 150 mL of pure water. After purging air inside the reactor, N2 gas was loaded. The upper reactor was heated up to 473–573 K. The pressure in the upper reactor (sample-loaded reactor) was close to the saturated pressure of water at the reaction temperature. After the desired treatment time, the valve between the two reactors was opened and the fractionated components in the reactor were recovered in the reservoir. The reservoir was then rapidly cooled with a water bath (ca. 10 min) and was then detached from the sample-loaded reactor. The residue in the upper (sample-loaded) reactor with the stainless mesh was weighed after drying at 333 K overnight. Connection lines between the two reactors were rinsed. The water-insoluble fraction among the recovered solutions was hydrothermal-soluble lignin (namely "hydrothermal lignin"). The soluble Klason lignin (hydrothermal lignin) was quantified, and the molecular characteristics (molecular weight with GPC and molecular structure with NMR) were evaluated.

As a result of the molecular characteristics, the hydrothermal lignin obtained from bark of Japanese cedar by hydrothermal extraction at 523 K under the saturated pressure of water, 3.98 MPa, about was mainly 6-mer (about 1 kDa of mean molecular weight) with syringyl-rich structure [2].

### **2.3 Dimensionless severity number**

The kinetic study for lignin recovery (how much percentage of Klason lignin can be recovered based on the Klason lignin in the raw material, the bark of Japanese cedar) was performed, and severity factor was used for consideration of the effect of reaction temperature and reaction time. The severity factor, *R*o [min], is defined as below:

*Advanced Supercritical Fluids Technologies*

$$R\_o = \exp\left(\frac{T - T\_r}{\alpha}\right)t\tag{1}$$

Eq. (5) shows that the dimensionless severity number (*k*r*R*o) is also the function of *t* and *T* as well as severity factor (*R*o) as shown in Eq. (1). While *R*o varies a wide range of values and the optimum *R*o for the target reaction is not easy to estimate, meaningful transitional change should occur at the range of 0.1 to 10 for the dimensionless severity number *k*r*R*o, as reported here and in the literatures [2, 32, 33]. Therefore, the dimensionless severity number (*k*r*R*o) is quite useful, and the severity analysis using *k*r*R*o can be adopted to various type of the reactions. Our research group is going to study on utilization of the dimensionless severity number (*k*r*R*o) for various kind of reactions and its application and usefulness with a variety

*Resource Upgrading in Advanced Supercritical Fluid (Supercritical Fluid with Catalyst…*

**3. Protein hydrolysis and amino acid degradation: low temperature catalytic hydrothermal cracking (LT-CHTC) for liquid fuel**

Based on the concept of "sustainable development goals (SDGs)" by UN and "circular economy" by EU, waste materials (by-product of main activity) must be used in effective and useful application and ideally must be back to primary resource production. In our daily life, huge amount of food waste generates and its utilization/valorization is still insufficient. This situation is not only for food waste (including house waste, municipal waste, sewage sludge, which are by-product of our daily life) but also agricultural by-product. One of the big problems of these wastes is to contain high amount of water, which is hard to exclude from the wastes. Water inside the waste (namely wet biomass) assists to cultivate fungi, and some of the wet biomass wastes are easy to rot with a bad odor and toxic component formation. Even with huge amount of energy loss, the large part of the wet wastes is forcedly burned to eliminate without effective utilization as energy or thermal

Microalgae, which has fast grow rate with CO2 stabilization through photosynthesis and attracts much attention as renewable resource, is also wet biomass as the same as daily-life wastes with containing a large amount of water mentioned above. The total difference of microalgae from the waste wet biomass is that cultivation and harvesting of microalgae can be controlled to level not only for yield but also composition. Thus, microalgae is a primary and industrial renewable resource. However, problem related to water is to be solved as well as wet biomass waste. Sub and supercritical water technologies enable water (also in the wet biomass)

to eliminate from the structure of the biomass and to use for hydrolysis of the natural polymer in the biomass as reactant. As mentioned above, supercritical water plays the important role in the CHTC for producing olefinic hydrocarbon from lipid and free fatty acid, as solvent and reactant. But, for feeding lipid into the process, extraction of the lipid from microalgae must be done. Typical lipid extraction processes from microalgae are solvent extraction and mechanical press, both of which require dry to improve lipid yield before the extraction. Also, in iso-

conversion concept, the residue of the extraction of lipid (protein and carbohydrate are main components) will be treated by anaerobic fermentation to form small molecules such as organic acids. Advantage of the biochemical process is high selectivity, but disadvantage is low reaction rate. For the purpose of liquid fuels production, broad product distribution in the range of small molecular weight is acceptable. Or rather, rapid transformation process has to be necessary for the residue conversion of the residual biomass containing protein and carbohydrate.

of the examples will be reported in near future.

*DOI: http://dx.doi.org/10.5772/intechopen.89793*

**3.1 How to convert protein-rich biomass into liquid fuels**

**production**

purposes.

**95**

where *T* [K] is reaction temperature,*T*r [K] is the reference temperature (here is 373 K), *t* [min] is reaction time, and*ω*is the function of activation energy,*Ea* [kJ mol�1 ], gas constant, *R* = 8.314 J mol�1 K�1 , and *T*r, as shown in the following equation.

$$\rho = \frac{R \bullet T\_r^2}{E\_a} \tag{2}$$

According to the derivation of the severity model, lignin recovery (*LR*) can be calculated by the next equation.

$$\text{Lignin\\_recovery} \ (LR)[wt96] = \{1 - \exp(-k\_r \bullet R\_o)\} \times 100 \tag{3}$$

where *k*r is the rate constants in min�1 at reference temperature *T*r (373 K), as described in the following equation:

$$k\_r = k\_o \exp\left(-\frac{E\_a}{RT\_r}\right) \tag{4}$$

where *k*o [min�1 ] is pre-exponential factor of the reference rate constant.

By fitting the equations to the experimental data (as shown in **Figure 3**), all the kinetic parameters were decided as to be 135 kJ mol�1 for *E*a and 6.8 � 10�5 min�1 for *k*r. The experimental data at the most severe condition (*k*r�*R*o value is over 1, and these data were obtained at 573 K for 10 min) were far from the calculated value, and the reason why the data are not fitted with the calculated value is because the cellulose in the bark was carbonized and the remained Klason lignin in the residue was estimated to be high.

As shown in **Figure 3**, lignin solubilization (lignin recovery) in hydrothermal water drastically changed between 0.1 < *k*r�*R*o value <10. The similar trend was seen in the previous reports [2, 32, 33]. From Eqs. (1), (2), and (4), the dimensionless severity number (*k*r�*R*o) is written by the below equation:

$$k\_r \bullet R\_o = k\_o \bullet t \bullet \exp\left(\frac{\mathcal{E}\_a(T - 2T\_r)}{R \bullet T\_r}\right) \tag{5}$$

**Figure 3.** *Dimensionless severity number for lignin recovery from bark of Japanese cedar (473–573 K for 3–40 min).* *Resource Upgrading in Advanced Supercritical Fluid (Supercritical Fluid with Catalyst… DOI: http://dx.doi.org/10.5772/intechopen.89793*

Eq. (5) shows that the dimensionless severity number (*k*r*R*o) is also the function of *t* and *T* as well as severity factor (*R*o) as shown in Eq. (1). While *R*o varies a wide range of values and the optimum *R*o for the target reaction is not easy to estimate, meaningful transitional change should occur at the range of 0.1 to 10 for the dimensionless severity number *k*r*R*o, as reported here and in the literatures [2, 32, 33]. Therefore, the dimensionless severity number (*k*r*R*o) is quite useful, and the severity analysis using *k*r*R*o can be adopted to various type of the reactions. Our research group is going to study on utilization of the dimensionless severity number (*k*r*R*o) for various kind of reactions and its application and usefulness with a variety of the examples will be reported in near future.