Biogas / Biomethane
Organic material breaks down without oxygen inside an anaerobic digester, producing methane-rich gas.
- Complexity
- Medium
- Best suited for
- Farms, rural properties, food operations and community-scale systems
- Scale
- Home · Farm · Commercial · Industrial
Overview
Biogas is a methane-rich gas produced when organic material breaks down in the absence of oxygen. It is one of the oldest and most widely deployed decentralised fuel technologies in the world.
Raw biogas is typically used close to where it is produced — for cooking, heating or a stationary generator. Using it as a vehicle fuel requires cleaning, upgrading to biomethane and compression, which is a substantially more involved and regulated step.
Key consideration
Raw biogas normally requires cleaning and upgrading before vehicle use.
Inputs & outputs
Feedstocks in
- Food waste
- Manure
- Agricultural waste
- Other organic material
Fuel out
- Methane-rich raw biogas
- Upgraded biomethane
How it works
- 1Organic waste
- 2Anaerobic digester
- 3Raw biogas
- 4Cleaning / upgrading
- 5Biomethane
- 6Vehicle / generator / heat
Conceptual diagram. Real systems include control, monitoring and safety equipment at every stage.
What can it power?
Equipment categories
- Feedstock preparation and mixing
- Digester vessel with temperature control
- Gas collection and pressure management
- Gas treatment (moisture, hydrogen sulphide, carbon dioxide)
- Storage
- Gas detection and monitoring
- Engine or burner interface
- Digestate handling
Described at a category level. Equipment should be professionally specified, certified and installed.
Cost profile
Startup
Medium – High
Operating
Low – Medium
Feedstock
Free to low-cost
Relative categories only. Real costs depend heavily on scale, equipment and local conditions.
Efficiency
Digestion converts only the biodegradable fraction of a feedstock into gas, and some of the energy produced is used to keep the digester warm. Upgrading and compression for vehicle use consume more energy again. Well-run farm systems recover a useful share of the available energy; poorly matched feedstocks recover very little.
Pros & limitations
Advantages
- Uses waste streams that otherwise cost money to dispose of
- Produces digestate that can be used as a soil amendment
- Runs continuously rather than intermittently
- Mature technology with established commercial suppliers
Limitations
- Needs a steady, consistent supply of feedstock
- Raw gas is corrosive and must be treated
- Vehicle use requires upgrading, compression and storage infrastructure
- Space, permitting and odour management requirements
Vehicle compatibility
Never assume compatibility. Verify with the engine or equipment manufacturer before use.
Storage
Low-pressure gas storage is bulky. Vehicle use needs high-pressure cylinders that fall under pressure-vessel codes and require certified components and inspection.
Safety & Regulations
Safety considerations
- Methane is flammable and can form explosive mixtures with air
- Digesters can produce hydrogen sulphide, which is toxic at low concentrations
- Confined-space entry around digesters is a recognised fatality risk
- Gas detection, ventilation and flame arrestors are standard professional requirements
Legal & regulatory
- Digester siting, zoning and odour rules
- Waste-handling and biosecurity requirements for some feedstocks
- Pressure-vessel and fire codes for gas storage
- Road-fuel tax and fuel-quality rules if used in a vehicle
Requirements vary by jurisdiction and fuel type. Verify applicable rules before producing, storing, selling or using fuel. Use certified equipment and qualified professionals.