**3. Results and Discussion**

The descriptors and the regression coefficients of the model are presented in Table 3. Together, the independent variables are statistically significant in estimating the water footprint (*p* < 0.00). According to the R squared statistic, 43% of the total variation of WFP is explained by the model. The model was also checked for multicollinearity as mentioned above. The variance inflation factor (VIF) value obtained was close to one and, thus, there was no evidence of multicollinearity [48]. To evaluate the relative importance of the independent variables, it is common to calculate the beta coefficients (standardized regression coefficients). In a regression of standardized variables, the (beta) coefficient estimates express the rank of independent variables in terms of the effect on the dependent variable. The independent variable with the largest (absolute) beta coefficient has the biggest effect on the dependent variable. The intercept in such a regression is zero by construction. According to the results, the F-ratio test confirms that the overall regression model is a good fit for the data (Table 3). The output shows that the independent variables statistically significantly predict the dependent variable.

**Table 3.** Results of the semi-log multiple linear regression model (n = 4853).

\*, \*\*, and \*\*\*, statistically significant at 10%, 5%, and 1%, respectively.

According to Table 3, both demographic variables (household size and age of the head of the household) are very significant (at 1%) in the prediction of the water footprint of food consumption of the household with coefficients −0.044 and 0.002, respectively. The city/geographic variable it is statistically significant at the 5% level; people with higher water footprints are more likely to be found in big cities than in small and medium ones. Region is very significant, with only the southeast not differing from the base of Tunis. The centre-east, centre-west and northeast have the highest coefficients: 0.165, 0.155, and 0.116, respectively. Concerning the socio-economic variables, poverty (−0.221), education particularly illiterate people (−0.040), and the socio-professional categories (SPC), especially farmers (0.108), are also very significant. Finally, variables related to food habits (Expenditures and Food waste) are also significant at the 1% level.

In terms of the relative importance of the effects on the dependent variable, based on beta coefficients, food expenditure per capita (0.456), household size (−0.157), and poverty (−0.151) have the largest contributions across the model. We also find that the centre-east (0.125) and centre-west (0.114) regions have the largest effects on the water footprint. This is followed by food waste, represented by the number of dishes thrown away with a beta coefficient equal to 0.069, the socio-professional category "farmer" (0.064), the age of household head (0.056), the education level of the household head, and, finally, the variable "City size" determining the size of the city of residence. The City size variable is linked to the degree of the economic development of the city. According to Souissi et al. [18], the evolution and increase in water footprint during the last thirty years in Tunisia is more rapid in urban regions. The more developed the city is and the better the economic situation, the higher the household water footprint. A 1 TND (US\$ 0.69) increase in food expenditure is associated with 0.04% increase in the average water footprint. This can be explained by the increased consumption of animal products, which are usually more expensive than plant products [49]. Meat and dairy products have a significant impact on the water footprint. This is an alarming sign, especially since the measured footprint is mainly internal (more than 70% of the water footprint of the main food products comes from local production) [18]. In other words, Tunisia is severely depleted of internal water resources by consumption habits.

A one-unit increase in the size of the household implies a 4% decrease in the average food consumption water footprint, controlling for food expenditure. Poor households have a 22% lower water footprint than other households. Wealthier households seem to consume products with a large water footprint.

Region is also an important factor to determine the water footprint of households. The average water footprint is, respectively, higher by 16%, 15%, 11%, and 8% for households living in the centre-east, the centre-west, the northeast, and the southwest of the country than for people living in Tunis. The centre-east and northeast regions are characterized by high economic development and tourism. Households' incomes are higher and access to more expensive food products, especially of animal origin, is better. Concerning the centrewest and the southwest, these regions are characterised by sheep and goat production, resulting in meat being both available and culturally important. Meat consumption is the highest in the southwest of the country. The average water footprint for people living in the northwest is 6% lower than for people living in Tunis. The diet in the northwest is based on cereal products, which has a lower water footprint. This region is less economically developed and has substantial cereal production. There is no significant difference between the water footprint for households living in the southeast and those living in Tunis. These results can be explained by the variation in culinary habits from one region to another. Regional food patterns are often very pronounced in Tunisia, particularly for meats [49].

Regarding food waste, all other variables being constant, we found that for each dish thrown away by the household the water footprint increases by 1.5%. Li et al. [33] found similar results showing that the increase in food waste contributes to a higher water footprint. For the socio-professional categories of the head of the household, the average water footprint is, respectively, higher by 10%, 5%, 4%, and 3% for farmers, freelance jobs, industry and commerce independents, and employees than for labourers.

Considering the effect of the head of the household's age, the unstandardized coefficient for the variable age is equal to 0.002. This means that for each one-year increase in the age, there is an increase in the average water footprint of 0.2%, all other variables held constant. It is hard to explain this small but very significant effect of age on the water footprint. On one hand, the increase with age may imply the presence of children, whose food consumption is characterised by incorporation of dairy products, meats, and cold cuts [50]. On the other hand, studies in other countries have shown that the oldest consumers ate more vegetables and fruits as well as less meat and fewer sugary desserts [50,51]. For education, the average water footprint is 4% lower for illiterate heads of households than for those with primary education. There is no significant difference between the other categories. Finally, regarding the city size, results show that the average water footprint is 3% lower in medium and small cities than in big cities. The effect of urbanization should not be overlooked. Urbanization was involved in our analyses due to the association of urbanization and the structure of the diet in many studies [52–56]. The literature examined shows that, unlike rural diets, urban diets are more characterized by the consumption of flour, more fat and animal products, more processed food, more sugar, and more food consumed outside the home. All of these elements necessarily impact the water footprint, which continues to climb in urban areas.

#### **4. Conclusions and Policy Implications**

The determinants of a consumer's water footprint depend on the water footprint of the goods produced. It also depends on what the consumer chooses to consume and the consumed quantities. Until now, studies related to the water footprint have not highlighted the factors affecting these choices nor their contributions to the water footprint of consumers.

In this paper, to better understand the factors that influence the food water footprint of Tunisian consumers, we used a semi-log multiple regression model. Results show that the increased consumption of animal origin products is necessarily linked to the increase in food expenditure per household and has a significant role in the water footprint increase. Demographic and economic characteristics such as household size and poverty are among the factors that contribute to the decrease in the consumer's water footprint. Moreover, regional disparities in food choices mean substantial differences in water footprints. Residents of the most developed cities and coastal cities in the centre-east, centre-west and northeast are more likely to have a large water footprint than residents of Tunis. Significant variability in water footprints, due to the different modes of food consumption and sociodemographic characteristics, was also noted. Food waste is one of the determining factors of households with a large water footprint.

This study contributes to the literature on the water footprint of food consumption using household level data. Estimates of the food water footprint can be used to assess potential scenarios for water demand as food consumption patterns change. Reducing the water footprint to sustainable levels is possible if consumption patterns change.

Analysis at geographic and social levels helps inform policy makers by identifying realistic dietary changes, taking into account socio-economic and regional disparities to effectively plan interventions and recommendations for a sustainable diet. It would be important to encourage more sustainable diets rich in vegetables and fruits, in particular through schools and advertising campaigns. In addition, in accordance with sustainable development goals and, in particular, objectives two (SDG2), six (SDG6), and twelve (SDG12), namely, to end hunger, ensure availability, and sustainable management of water and reduce food waste, it will be necessary to reconsider import and export strategies for food/agricultural products as well as food subsidy policies. For example, the wheat import strategy is effective during years when world prices for cereal products are lower than the cost of production. This allows Tunisia to save very important volumes of water. However, for reasons of food security and food sovereignty, the cultivation of wheat should

be encouraged especially in more humid areas, especially in the north-west where the diet depends mainly on these products.

Several economic and political mechanisms aimed at reducing the water footprint of food consumption are possible. On the one hand, this may be achieved by relying on supply chain marketing strategies such as labeling. On the other hand, on an international scale, the ISO 14046 standard specifying the principles, requirements, and directives relating to the evaluation of the water footprint of products and processes has been established. Other measures based on food price and subsidy policies as well as consumer awareness campaigns can yield tangible results. Agricultural policies can also be an effective tool to reduce the water footprint of food consumption.

However, conclusions and recommendations should be viewed with caution since several limitations are noted in the use of this concept. The main limitations are the imprecision of the estimates, which is due to the difficulty of estimating water consumption at all stages of the food chain. Water volumes for products vary depending on production systems, rainfall, soil quality, yields, irrigation, etc. Other factors affect other aspects of the food chain, so imprecision accumulates. In addition, only the main food groups are considered and the data do not include fish products. In addition, the insufficiency of the volumetric approach should not be overlooked, since in addition to the volume of water consumed, the quality and conditions of access to water also play a role in decisionmaking regarding the use of resources. Another difficulty is the evaluation of grey water; determining the volumes of water "hypothetically" necessary to dilute the pollution to a tolerable level is quite arbitrary and very complex. To conclude, we can say that the use of the water footprint must take into account several limits depending on the context and the objective.

Finally, the absence of previous work that models the factors influencing the water footprint of food consumption opens up several perspectives for future research. The exploration and identification of new influencing variables (such as diet diversity, processed food consumption, etc.) and the use of more recent data that take into account postrevolutionary political and social changes in Tunisia are a priority.

**Author Contributions:** Conceptualization, A.S. and N.M.; methodology, L.M., N.M. and C.T.; software, A.S.; validation, L.M., N.M., C.T. and A.C.; formal analysis, A.S. and N.M.; investigation, A.S.; resources, L.M.; data curation, A.S.; writing—original draft preparation, A.S. and N.M.; writing review and editing, L.M., N.M. and A.C.; visualization, A.S.; supervision, C.T. and N.M.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

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

#### **Appendix A**

**Table A1.** Akaike's information criterion and Bayesian information criterion.

Note: N = Obs used in calculating BIC.

#### **Appendix B**

estat hettest, rhs Breush–Pagan/Cook–Weisberg test for heteroscedasticity Ho: Constant variance

Variables: AgeChefMe Nombredeplatsjetes vuln taille DAP 1b.newstrate 2.newstarte 1.DNiveau 2b.DNiveau 3.DNiveau 4.DNiveau 1b.region 2.region 3.region 4.region 5.region 6.region 7.region 1.DCSP 2.DCSP 3.DCSP 4.DCSP 5b.DCSP 6.DCSP 7.DCSP Chi2(21) = 467.20 Prob > chi2 = 0.0000


**3. Bryophyta on the hydraulic media**

Moss (Bryophyta) is a group of lower plants that grow widely on land. Moss is a small plant that grows attached to the substrate (stones, trees, wood, and soil). The life of moss is influenced by environmental factors such as temperature, humidity and light [3].

Moss has green leaves and contains chlorophyll so that with the help of sunlight it can carry out the process of photosynthesis [4]. Leaf moss (musci) is an expanseof leaf moss consists of one leaf moss plant that grows tightly and densely in groups to strengthen and support each other (**Figure 1**). This moss is not attached to its substrate but has rhizoids attached to its body. The body is generally erect, in the form of a thallus, leaves like scales that are dense, dense, and flattened or piled up. Moss forms a thallus in the form of a pillow or thick, and on the forest, the soil is often a layer resembling a velvet [8]. Leaf moss (moss) is the most famous moss plant. Leaf mosses consist of dense groups of mosses, which support each other. Each plant incorporated in the bed is attached to the substrate by elongated cells or cellular filaments called rhizoids. Unfortunately, in this paper, the identification of mosses has not been carried out.

**Figure 1.** *Moss on Hydrophonic Media in Cirebon, West Java, Indonesia.*


**6. Magnesium solution in the automotive sector: the present**

One significant value that manufacturers usually give to magnesium is its excellent die-castability resources, compared with aluminum. It is mainly due to very low viscosity in the molten state and reduced (or absent) die-soldering phenomena with steel mold-die that broadly extend mold-dies lifespan. The high castability is one metallurgy factor that allows die-casters to realize large, thin-walled, and complex casting shapes. It is due to a less costly manufacturing process that would replace steel-made components by assembling numerous steel stamped pieces or heavily reinforced plastic members [37]. As magnesium alloys can be cast with thinner walls than aluminum, the lower elastic modulus of magnesium alloys can be compensated using located ribs of thin wall thickness that allow restoring stiffness at required values. Secondly, the lower latent heat for solidification of magnesium compared to aluminum leads to considerably shorter casting cycle times, compensating for the lower heat conductivity of magnesium. For a comprehensive overview of die-casting processes and recent advancements, you may refer to [38], here in the following, shortly resumed. Two main casting processes are available for magnesium, the pressure-assisted cold, and hot-chamber injection, with an alternative represented by low-pressure die casting. In pressurized injection casting processes, high pressure is exerted after the liquid metal injection to compensate for metal shrinkage and remove as much possible air entrapped during the shot sleeve movement that accelerated to pressurize liquid metal into the die. The metal solidifies at high cooling rates (higher for the cold chamber than the hot chamber), leaving a fine-grained material (more satisfactory for the cold-chamber process) with secondary dendrite arm spacing in the range of 5–10 μm. As it is usual for any metal, particularly for magnesium alloys, grain refinement is one primary strengthening mechanism capable of saving good ductility and though properties, generally lower for the common magnesium-aluminum alloys containing more than 3–4% of aluminum. If, on one hand, aluminum promotes a strengthening mechanism based on a solid solution, on the other hand, an excess of aluminum (it is limited up to 9%) produces an almost continuous secondary phase of aluminum enriched—the magnesium aluminide, Mg17Al12. The magnesium aluminide decreases local plastic resources at the alpha-solution grain boundaries, where magnesium aluminide precipitates.

The long tradition of magnesium automotive part die-casting is proper for magnesium manufacturers, as shown in **Figure 8**, where an example of Meridien's timeline for automobile products is summarized. Magnesium die-casting is evolving in Mercedes-Benz automatic transmission cases, from the first seven-speed automatic transmission case developed in 2003 (**Figure 9**) to the current eight-speed transmission case, still manufactured by magnesium alloy.

**Figure 10a** shows the recent magnesium die-cast liftgate inner for the 2017 Chrysler Pacifica Mini-Van realized by Meridian Company with Fiat-Chrysler Automobiles. The liftgate assembly consists of:

### **Figure 8.**

*Meridian product development timeline (courtesy of IMA).*

### **Figure 9.**

*The 2003 case of the 7G-TRONIC, the world's first seven-speed automatic transmission.*

### **Figure 10.**

*(a) Diecast liftgate inner by Meridien (courtesy of IMA), 1450 mm wide, 1210 mm in height, the mass of 6.9 kg, (b) Strut bar Audi A8 (courtesy of IMA).*

An AM60B alloy has been used due to elongation, strength, castability, and energy-absorbing properties. The magnesium casting allows replacing seven steel stampings, including reinforcements in hinge & latch areas, two plastic pieces, joining technologies. In the final assembly, a powder coat was applied to all structures to prevent galvanic corrosion problems. **Figure 10b** shows the new die-cast strut bar of *Magnesium Alloys for Sustainable Weight-Saving Approach: A Brief Market Overview, New… DOI: http://dx.doi.org/10.5772/intechopen.102777*

### **Figure 11.**

*Recent die cast parts from magnesium industry [courtesy of GF Casting Solutions]: (a) Porsche Control Box Cover, made of MgAl4RE4 alloy, 2.6 kg weight, realized by multistage process (casting, stamping, machining), then assembled; (b) E-vehicle upper door frame alloy made of AM 50 alloy, 2.9 kg weight, realized by multistage process (casting, punching, machining, e-coating); (c) Ranger Rover Front End & Cross Car beam made of AM60 alloy, 6.0 kg weight realized by the multistage process then assembled (casting, machining, stamping); (d) Daimler SLK 2 seat back frame, AM 50 alloy by die-casting, 2.6 kg weight (courtesy of GF Casting Solution AG).*

Strut bar for Audi A8 realized by Stihl Magnesium. In **Figure 11**, several magnesiummade parts have been recently put onboard vehicles.

Magnesium part manufacturers deploy a long-tradition cumulated in warm and hot deformation processes (**Figure 12**). Opposite to the common thought about magnesium deformation resources, wrought magnesium alloys are suitable for sheet forming contributing to weight-saving projects in the automotive sector. Indeed, significant drawbacks in magnesium alloys' sheet forming and deformation processes exist, especially compared to aluminum alloys. Due to its hexagonal structure, to activate enough slip systems for assuring sufficient plasticity, magnesium alloys must be formed above 200°C. Furthermore, the different heat transfer capability compared to aluminum is an issue to consider for optimizing pre and re-heating temperatures in the hot-deformation multistage processes. Extrusion of magnesium alloys is usually carried out in multiple steps, starting with a pre-extrusion of large billets into smaller diameter billets. After the preliminary stage, the billet can be re-heated and subsequently extruded into the final shape. Generally, the pressure per unit volume material

**Figure 12.** *The Chevrolet Corvette SS Race Car, 1957, made of magnesium-formed panels.*

extruded is higher than in aluminum alloys. Thus, extrusion speed shall be carefully controlled and optimized for specific magnesium alloy to avoid local melting and local oxidation phenomena, particularly critical for hollow sections extrusion process by porthole dies, as typically employed for aluminum alloys. These aspects are firm limits for semi-finishing and net-shape forming processes, prominently for affordability.

But on the other hand, warm deep drawing is also possible for magnesium alloys, as for aluminum alloys; in the range of 100–180°C thin sheet of 0.5 mm approximately can be drawn, with precise temperature control and at a lower speed [39]. The recent application of magnesium sheets we can find in the literature illustrates the successful use of a novel Mg-Zn-Ca-Zr alloy in sheet form produced by twin-roll casting. This alloy has been used to manufacture a Volkswagen Passat decklid magnesium-made that saved half 6 kg of the original 12 kg steel weight [40]. Large magnesium components can also be produced by die casting (see **Figure 13**).

Net-shape semi-solid forming has attracted automakers with alternate attention since the middle 1990s. The net-shape semi-solid forming is possible for magnesium alloys thanks to its thixotropic state realized when vigorously sheared in a semi-solid state. Shearing reduces the viscosity of the slurry mass to a similar value of the liquid metal, providing similar (sometimes better) castability of the liquid form. Still, the semi-solid state allows shaping with lower latent heat in the mass; this creates advantages for shorter casting cycles than die-casting (depending on chosen semisolid process) lower metal shrinkage to compensate, and consequently near-net shaping. The industrial application of semi-solid net-shaping in the magnesium industry commenced in the early 1980s with the Dow Chemical Company. Dow Chemical patented the Thixomolding technology based on the architecture of plastic injection molding machinery for injecting magnesium alloys in the semi-solid state into a mold die.

Further advantages of injection molding of magnesium alloys are that this technology's highly complex shaping capability allows for more innovative design concepts and a multi-body-material concept design. Direct assembly of different

*Magnesium Alloys for Sustainable Weight-Saving Approach: A Brief Market Overview, New… DOI: http://dx.doi.org/10.5772/intechopen.102777*

**Figure 13.**

*(a) The Porsche window frame realized by AM50 magnesium alloy with multi process stages (casting, laser cutting, machining), finally coated and joined; (b) The Aston Martin cover door made AM50 with multi-stage process (Casting, Stamping, Flattening) [courtesy of GF Casting Solutions AG].*

parts during injection molding in a molded-in technique, thanks to inserting aluminum parts directly in the tool. As a semi-solid process, less energy is consumed by the Thixomolding apparatus; the power energy is estimated to be on the order of 12–24% lower than the total energy required by a conventional casting process. An additional benefit is that the Thixomolding product cycle employs inert gas, usually argon, to protect magnesium feedstock from oxidation once introduced in the hopper in particulate and solid forms (pellets or chips) [41]. However, it is worth noticing that current die-casting processes align with the environmental sustainability of the Thixomolding process thanks to much more environmentally friendly cover gases mixtures today used instead of the banded SF6. With relevant advantages of the Thixomolding process in net-shaping part of high complexity in a single shot, two are the most drawbacks acknowledged by part manufacturers. The high price and the limited number of suppliers of chip or pellet forms of magnesium alloys, namely the material feedstock of Thixomolding machinery, and the maximum clamping force exerted during the metal injection into mold dies. Clamping forces of 2700–6500 kN generally allow the production of thin flat surfaces (0.8 mm, not possible by high pressure die-casting) such as that for tablet terminals, notebook computers, electronics, sports goods. Instead, the interest of the automotive sector is to even thicker and wider structural components with a weight of over 2 kg. This would require more giant machines with increased clamping forces over 8000 kN [41].


**Author details**

Robyn Hudson1 \* and Gerard A. Kennedy2

1 National University of Mexico, Mexico City, Mexico

2 Federation University, Ballarat, Australia

\*Address all correspondence to<EMAIL_ADDRESS>
© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.