How is biogas produced?
Biogas is a way to extract valuable energy from materials we usually throw away. Whether it’s manure from farms, food scraps from kitchens, or wastewater from treatment plants, organic waste can become a useful energy source when processed correctly.
In this article, we take a closer look at this ingenious process and explain how biogas is formed, what conditions it requires, and how it fits into a more efficient and sustainable energy system.
What is biogas made from?
Biogas is produced from organic material, also known as feedstock. These materials are rich in biodegradable matter and come from a variety of sources:
- Agricultural waste, such as animal manure, straw, or silage leftovers
- Food waste, including kitchen scraps, expired groceries, and food industry byproducts
- Sewage sludge and wastewater, often collected from municipal treatment plants
- Organic industrial waste, such as glycerin, dairy byproducts, or distillery residues
The key requirement is that the feedstock contains organic compounds that bacteria can break down in an oxygen-free environment. The more consistent and nutrient-rich the feedstock, the more reliable the biogas production.
Biogas production — The anaerobic digestion process explained
The core of biogas production is anaerobic digestion, a biological process that happens when microorganisms break down organic material in the absence of oxygen.
This process happens in four main steps:
- Hydrolysis: Complex organic molecules like carbohydrates, proteins, and fats are broken down into simpler compounds such as sugars and amino acids.
- Acidogenesis: These simple compounds are converted into volatile fatty acids, alcohols, carbon dioxide, and hydrogen.
- Acetogenesis: The intermediate products are further digested into acetic acid, CO₂, and hydrogen.
- Methanogenesis: Special microorganisms called methanogens convert these compounds into methane (CH₄) and carbon dioxide (CO₂) — the primary components of biogas.
Each phase relies on different types of bacteria, working in a carefully balanced environment. If the process becomes unstable — due to pH changes, temperature shifts, or toxic substances — gas production can be affected.
Biogas plant setup: What happens inside a digester?
Anaerobic digestion typically takes place inside a biogas digester — a sealed, oxygen-free tank designed to maintain the right conditions for microbial activity. The digester is filled with organic feedstock and kept at a consistent temperature (usually mesophilic, around 35–40°C, or thermophilic, around 50–55°C).
Inside the digester:
- The material is mixed regularly to distribute bacteria and prevent scum or sediment buildup
- Gas accumulates in the top section and is piped off for storage or use
- Digestate — the remaining liquid or solid — is removed periodically and often used as a natural fertilizer
Depending on the scale of the system, the digester may be part of a larger facility that includes storage tanks, separators, and gas treatment units.
Renewable natural gas: Upgrading biogas to biomethane
Raw biogas contains about 50–70% methane, with the rest mostly carbon dioxide, plus small amounts of hydrogen sulfide, moisture, and other trace gases. For some applications, especially grid injection or vehicle fuel, this gas needs to be upgraded.
Biogas upgrading involves removing CO₂, water vapor, and impurities to increase the methane concentration to above 95% — creating biomethane or renewable natural gas (RNG).
This can be done using:
- Pressure swing adsorption (PSA)
- Water or chemical scrubbing
- Membrane separation
Once upgraded, biomethane can be compressed or liquefied and used just in pipelines, Combined Heat and Power (CHP) systems, or heavy-duty vehicles, just like natural gas.
Factors that influence gas yield and quality
Several factors impact how much biogas is produced, and how clean and consistent it is. Well-managed systems can produce high gas yields with minimal downtime. When gas composition is stable and free of contaminants, it’s easier to control emissions and stay within environmental limits. This is especially important in regulated sectors or urban applications.
Factors that influence gas yield and quality include::
- Type of feedstock: Different organic materials break down at different rates and produce varying amounts of methane. Manure, food waste, crop residues, and industrial byproducts all have unique energy content and biodegradability. High-energy materials like fats and starches tend to produce more gas, while woody or fibrous inputs are harder to digest.
- Feedstock consistency: A steady, well-balanced supply of feedstock supports stable microbial activity. Sudden changes in volume or composition can disrupt the digestion process and reduce gas yield.
- Retention time: This is the time the feedstock stays inside the digester. Longer retention generally leads to more complete digestion and higher methane production — up to a point. If the material moves through too quickly, some of the potential energy is lost.
- Process temperature: Anaerobic digestion works best at controlled temperatures. Mesophilic conditions (around 35–40°C) are common, while thermophilic digestion (around 50–55°C) can increase output but is more sensitive to fluctuations.
- pH and system balance: Biogas-producing bacteria are sensitive to pH changes. The system should stay slightly alkaline (around 6.8–7.4) for optimal microbial performance. Acid build-up from improper feedstock balance can inhibit gas production.
- Mixing and system design: Regular mixing ensures even distribution of microbes and feedstock, and prevents sedimentation. The digester’s size, shape, and insulation also affect how efficiently the process runs.
- Inhibitors and contaminants: Some substances — like ammonia, sulfur compounds, or heavy metals — can interfere with microbial activity and reduce methane content. Gas quality monitoring and feedstock screening help manage this risk.
High quality biogas can be used more efficiently and contributes to a more environmentally friendly impact. It reduces wear, improves efficiency, and ensures the long-term viability of biogas-powered systems.
What is the difference between natural gas and biogas?
What is better — biogas or natural gas? In this article, we will look into their advantages and drawbacks. Biogas and natural gas are two significant energy sources that are utilized in different sectors for energy generation.
Environmental and operational benefits of biogas
Producing biogas offers many environmental and operational benefits. It reduces methane emissions from decomposing waste, lowers dependence on fossil fuels, and supports local energy production.
The digestate which is left after gas production can be used as synthetic fertilizer, which further reduces both the cost and environmental impact of the gas. This makes biogas particularly valuable in sectors like agriculture, where biological waste is a byproduct that can be as for different tasks that require fuel.
By using existing waste streams, biogas supports a more circular economy where resources are reused and emissions are kept in check.
PowerUP’s role in supporting biogas-based energy systems
Biogas is a valuable fuel, but it can also come with technical challenges. Gas quality varies depending on feedstock and process control. Impurities like sulfur and moisture can affect engine components and combustion efficiency.
At PowerUP, we work with operators who use biogas in combined heat and power systems or off-grid applications. Our focus is on maintaining performance, even when gas conditions are less than ideal.
This includes:
- Helping optimize combustion for variable gas composition
- Offering gas engine spare parts and upgrade options designed for durability and high performance
- Supporting condition-based overhauls to extend engine life
- Providing remote diagnostics to track system behavior and detect early signs of wear or inefficiency
With the right support, biogas systems can operate reliably, deliver consistent output, and make better use of locally available energy resources.
