Biogas plants – how do they work and where can they be used?

A biogas plant is a technological installation where anaerobic digestion (the breakdown of organic matter without access to oxygen) of biomass occurs. Biomass includes, for example, agricultural waste, food production waste, slurry and manure, or municipal biowaste. As a result of fermentation, biogas is produced—a mixture mainly consisting of methane (CH₄) and carbon dioxide (CO₂). Methane content in biogas typically ranges from 50–70%, making it a valuable fuel.

Biogas can be used for:

• electricity production,
• heat production,
• powering cogeneration engines (so-called biogas cogeneration),
• purification and injection into the gas grid (in the form of biomethane).

A typical industrial or agricultural biogas plant consists of several key components:

• substrate storage – e.g. silos, tanks, halls for silage, slurry, organic waste,
• substrate feeding system – devices (conveyors, pumps, feeders) ensuring uniform feeding of the fermenter,
• fermenter – the “heart” of the biogas plant. A sealed, heated tank where anaerobic fermentation occurs,
• digestate tank – where digested biomass (digestate) is stored, often used as fertilizer,
• biogas tank – a flexible dome or separate tank storing the produced biogas,
• biogas purification system – removes hydrogen sulfide, water, and other contaminants to prepare biogas for combustion,
• CHP unit (combined heat and power) – a device that converts biogas into electricity and heat,
• control and monitoring systems – enabling automation and control of the fermentation process.

Odor is one of the most common concerns associated with biogas plants. However, modern installations are designed to minimize the emission of unpleasant smells. The most important factor is system tightness – from substrate storage and transport to fermentation and digestate storage. Proper substrate management (e.g. quickly covering silage, closed feeding systems) and regular cleaning and ventilation of technical facilities help significantly reduce unpleasant odors. In practice, a well-designed and properly operated biogas plant should not cause nuisance odors in the surroundings, even when processing organic waste. Especially since any odor emission potentially means the loss of valuable gas.

Biogas is not entirely zero-emission, but it is significantly less emissive than traditional fossil-based energy sources. CO₂ is also produced when biogas is burned, but this is biogenic carbon dioxide, previously absorbed from the atmosphere by plants. Therefore, the emission balance is largely climate-neutral.

Biogas with a negative emission factor is also gaining increasing importance on the market. It is produced through the fermentation of substrates which, in the case of uncontrolled natural decomposition (e.g. slurry, biowaste), would emit significantly more methane and CO₂ into the atmosphere than during the controlled combustion of biogas. As a result, the emission balance of such fuel is not only neutral but even negative. Biogas with a negative carbon footprint opens new opportunities for industry in the context of achieving climate goals.

Advantages of biogas plants:

• renewable energy source – biogas is produced from organic waste, which is continuously available and considered renewable,
• local energy production – reduces transmission losses and independence from external energy suppliers,
• reduction of methane and CO₂ emissions – less environmental burden,
• utilization of organic waste – especially in the agri-food industry,
• fertilizer production – digestate can replace synthetic fertilizers,
• possibility of cogeneration – increases energy efficiency.

Disadvantages of biogas plants:

• high investment costs – especially for large industrial installations,
• complex technological process – requires knowledge, experience, and constant supervision,
• dependence on substrate suppliers – if the fermented waste does not come from own production,
• digestate disposal cost – if there is no possibility to use the post-fermentation waste, it must be disposed of,
• potential odor nuisances – in case of poor waste management.

Industrial biogas plants are most effective in places where significant amounts of organic waste are generated and there is constant demand for energy and heat (to efficiently use, for example, cogeneration). The most common sectors include:

• food and agri-food industry – e.g. dairies, vegetable and fruit processing plants, meat plants,
• agriculture and large-scale farms – with access to slurry and silage,
• sludge treatment facilities – e.g. wastewater treatment plants,
• municipal and waste management plants – processing municipal biowaste.

Biogas cogeneration is a technology in which biogas is burned in a cogeneration unit to simultaneously produce electricity and heat. This achieves high energy efficiency, often exceeding 80%.

In practice, this means that:

• electricity powers the plant’s systems or is sold to the grid,
• heat is used locally – e.g. for heating buildings, technological processes, or maintaining fermentation temperature.

Biogas cogeneration is ideal for industrial plants with continuous energy and heat demand – it significantly improves biogas utilization efficiency and shortens the investment payback period.

Biomethane plants are a modern extension of traditional biogas plants, offering more advanced and efficient biomass utilization. Unlike classic installations producing biogas, biomethane plants purify it into biomethane, which has properties comparable to natural gas and can be directly injected into the gas grid. This process not only increases the energy value of the produced fuel but also enables its storage and long-distance transport. Biomethane plants are also a viable alternative to biogas plants when there is no local heat demand, as the gas is only burned to sustain fermentation, and the entire surplus is sent to the gas grid. Importantly, biomethane can be used in both energy and transport sectors, serving as an alternative to LPG or CNG.

Biogas and biomethane plants represent a viable alternative to traditional energy sources, especially in industry. They allow for the utilization of problematic organic waste, reduce reliance on external energy suppliers, and lower energy costs. Thanks to biogas cogeneration, full use of the produced fuel is possible, making this technology particularly attractive in terms of energy and economic efficiency.

Investing in a biogas plant can also be part of a broader ESG strategy and a response to EU environmental regulations. By producing energy from local, renewable resources, industrial plants not only reduce their carbon footprint but also enhance their brand image as responsible and innovative companies. When combined with other energy efficiency solutions, a biogas plant can be an important step toward circular and sustainable production.