Are you ready to transform organic waste into genuinely high-quality fertilisers and multiply the amount of electrical energy generated from waste?
The term biogas essentially refers to the production of usable gas from organic waste. In other words, it is the conversion of organic matter into carbon dioxide and methane gas under the influence of microbiological flora in an oxygen-free environment.
Since biogas production is fundamentally based on the decomposition of organic matter, plant waste or animal manure can be used as the primary material. Animal manure is widely used as a primary material worldwide because fermentation during its conversion into biogas makes it more beneficial. Poultry manure can also be used to produce biogas highly efficiently. The use of poultry manure is important for agriculture. However, due to its highly acidic content, this manure cannot be applied directly to soil. Converting this otherwise unusable manure into biogas makes it beneficial. Today, biogas is produced on many different scales—from meeting the heating and cooking requirements of a single household to generating electricity with generators and operating large-scale power plants.
Biogas is formed in three stages:
The first stage involves converting waste into soluble substances through enzymes secreted by microorganisms. During this stage, polysaccharides are converted into monosaccharides, while proteins are converted into peptides and amino acids. In the following stage, acid-forming bacteria convert these substances into smaller molecules such as acetic acid. Acid formation may cause the pH to decrease during production, which can negatively affect the bacteria responsible for methane formation. During the final stage, methane-forming bacteria convert these substances into biogas. As can be seen, biogas formation occurs through microbiological agents; consequently, any condition affecting these microbiological organisms also affects biogas production.
Hydrolysis stage: During the first stage, substances that are not soluble are dissolved in the sludge through cellular enzymes secreted by microorganisms. Long-chain complex carbohydrates, proteins, fats and lipids are converted into short-chain structures. The first stage—hydrolysis—is completed once they have been converted into these simple organic compounds.
Acid-formation stage: The dissolved organic substances are converted into small molecules such as acetic acid, volatile fatty acids, hydrogen and carbon dioxide. This stage is carried out by anaerobic bacteria. These bacteria create a suitable environment for methane-forming bacteria.
Methane formation: This is the process through which bacteria break down acetic acid or synthesise hydrogen and carbon dioxide to produce biogas. Methane production is slower than the other processes. The bacteria involved in methane formation are strongly affected by environmental conditions.
The materials used in biogas production can be examined under three categories: animal manure, organic waste and industrial waste. The materials used in this context include:
Biogas can be produced using agricultural waste as well as industrial waste. The separate collection of municipal waste and the collection of sewage waste at treatment plants offer significant opportunities for biogas production. In this context, the İzmir Metropolitan Municipality has conducted certain studies in Türkiye as part of its Grand Canal Project.
Bioreactors are the general name given to structures designed for biogas production. They can be divided into small-volume and large-volume systems. Small-volume reactors can have capacities of up to three tonnes. However, research has shown that the desired level of efficiency cannot be achieved with capacities below 10 tonnes. Whether production will be batch-based or continuous is also a determining factor in bioreactor design. China is the country that uses bioreactors and biogas most extensively in the world. It also has its own distinctive small-capacity reactor systems. Bag-type or balloon-type reactor models have recently become more widespread because of their low cost. However, the efficient service life of these reactor models is approximately two to three years. The three most commonly used reactors in biogas production are:
When animal manure is released into the environment without undergoing any treatment, it creates extremely high levels of pollution. The annual CH₄ emissions generated by manure from a farm with 80 cows are equivalent to 110 tonnes of CO₂—the carbon emissions produced by 110 vehicles continuously on the road. Installing a biogas facility at such a farm can transform this environmental burden into green energy that can be used by the farm.
Applying untreated animal manure to the soil increases soil salinity. Harmful organisms contained in the manure enter the cultivated soil and cause groundwater contamination.
A wind turbine with a capacity of 1 MW can generate an average of 3,066 MWh of electricity annually. A solar power plant with a capacity of 1 MW can operate only during sunlight hours—an average of 2,300 hours per year—and generate 2,300 MWh of electricity. A biogas facility with a capacity of 1 MW can generate electricity for 8,200 hours per year.
In addition to electricity generation, the thermal energy produced while the cogeneration facility is operating can be used in numerous fields.
The waste obtained after fermentation is an effective soil conditioner and can be enriched and made available for use as biofertiliser.
Operating biogas processes efficiently involves numerous challenges and parameters. Many factors—including variations in the organic waste used as the primary raw material, changing seasonal conditions and air temperatures, the organic-matter loading rate, pH value, toxicity, the C/N (carbon/nitrogen) ratio and ammonia formation—can affect or even completely halt the production of biogas from waste.
Furthermore, the extremely long fermentation periods reduce the capacity of the waste that can be processed and decrease the proportion of METHANE (CH₄) obtained and, consequently, the amount of electricity generated.
The organic outputs obtained through fermentation often fall far short of being efficient, high-quality fertilisers and cannot be used on agricultural land. This results in the loss of an additional source of economic value and prevents agricultural land from achieving efficient results.
Subjecting organic waste to hydrogenation through BAUER processes:
With the next-generation HYDROMETHAN technology, the objective is to produce electrical and thermal energy more rapidly, sustainably and economically while obtaining high-quality fertilisers and organic materials.
