Operating material biogas

Biogas is a burnable gas that is produced by the fermentation of biomass and/or the biodegradable parts of waste. It mainly consists of the valuable fuel methane. The higher the methane content, the higher is the energy content of the produced gas.

MWK Biogas has utilized the experience and skills of our specialists to provide an extremely high methane content in the biogas for our systems. This mainly depends on the fermented substrates together with external additions. These additions allow an increase of up to 25% of the gas rate.

Detailed description of the fermentation process
Biogas results from the anaerobic degradation of organic materials. Anaerobic means ‘without presence of air’. Hence this degradation is also called digestion or fermentation. Many different bacterial strains, that degrade the organic materials step by step, are involved in the Biogas process. Which interstage products are built, primarily depends on the feeding materials. The thereby produced Biogas consists primarily of both gas parts methane (CH4) and carbon dioxide (CO2).

1. Stage of decomposition: Hydrolysis
In the first stage complex permanent organic compounds are degraded into simpler compounds. This will be achieved by enzymes set free by hydrolysis bacteria.

2. Stage of decomposition: acidification
Involved are acidified bacteria, that are able to continue degrading interstage products like sugar, long-chain fatty acids and amino acids. By this process evolve short-chain fatty acids like butter acid and propanoic acid, alhoholic compounds and some gas components like carbon dioxide.

3. Stage of decomposition: Production of acetic acid
In the third stage of anaerobic degradation, interstage products of the previous stage will be transformed into acetic acid, carbon dioxide and hydrogen. These compounds are the direct pre-products for the Biogas production.

4. Stage of decomposition: Methane production
In the last phase the high-energy methane will be produced. Here engaged bacterial strains are named after their end-product methane.

The valuable part of this combustible gas is methane (CH4) with a heating value of 10 kWh per m³. With an increasing methane content Biogas has a higher energy value.

Average consistence of Biogas:

Gas content Concentration
Methane (CH4) 50 - 75 vol. %
Carbon dioxide (Co2) 25 - 45 vol. %
Hydrogen sulphide (H2S) 0 - several 1,000 ppm
Oxygen (O2) / Hydrogen (H2) < 2 Vol. %

The quality of Biogas depends significantly on:

- ingredients of input materials: With an optimal fermentation, materials rich in fat and proteins deliver a higher quality and quantity of Biogas yields.

Organic element group Gas yield [l/kg organic dry matter] Methane content [Vol. %]
Proteins 600 - 700 70 - 75
Fats 1,000 - 1,250 68 - 73
Carbon hydrates 700 - 800 50 - 55

- the content of hydrogen sulphide; it depends on the sulphide content of input substrates / materials. Biogas from fermentation of protein-rich substrates generally contains higher sulphide concentrations.

- a sufficient retention time of the input materials in the digesters and on an optimal fermentation.

Zu den baulichen Bestandteilen einer Biogasanlage

Our staff with longterm experience in the Biogas business guarantee you a competent consultancy in respect of:

- Fermentation characteristics of your substrates
- Information about their consistency
- Avoidance of inhibitors of the biological process
- Options to increase the gas rate and to reduce input substrates by additives from our biotechnology.

Please also refer to our information concerning gas rate increase and a manure-free fermentation by addition of bacterial strains.

The diverse practical experience of our specialists is often the key criterion for your successful Biogas process.