Biodigesters: Creating Energy

Biodigesters

Using Organic Waste to Create Renewable Energy and Reduce Methane Emissions

What’s the challenge?

Modern societies and economies produce an increasing amount of organic waste, such as agricultural residues that include things like food waste and animal manure. When these materials break down, they release methane into the atmosphere.

Methane is a strong greenhouse gas up to 30 times more potent than carbon dioxide over a 100-year period, and it is responsible for around 30 percent of the global temperature rise since the Industrial Revolution.

It is estimated that around 580 million tonnes of methane is emitted each year, with approximately 60 percent attributed to human activity, including emissions from the agriculture and waste treatment sectors.

How do biodigesters work?

A biodigester is a system that decomposes organic material such as food waste, animal manure and sewage. Through a biological process called anaerobic digestion, organic material diluted in water is broken down by microorganisms, releasing two valuable by-products:

Biogas: A mixture of methane and carbon dioxide.
Digestate: A nutrient-rich material that can be used as an organic fertiliser.

The biogas can be used as a sustainable energy source for electricity, cooking and heating. This provides an environmentally friendlier alternative to fossil fuel-derived energy. Biogas can also be upgraded to biomethane, which is a drop-in alternative for natural gas, without needing modifications to existing infrastructure while offering the same energy system benefits of natural gas and also being renewable.

Climate mitigation potential

Thanks to their flexibility in processing various organic materials, biodigesters can be strategically placed near farms, landfill sites, and sewage treatment plants. This positioning allows them to efficiently convert organic waste streams into renewable biogas and biomethane.

The IEA’s report, “Net Zero Roadmap – A Global Pathway to Keep the 1.5 °C Goal in Reach“ projects that the supply of biogas and biomethane could increase sevenfold from current levels by 2030, accounting for 1.2% of global energy supply. By 2050, this share could rise to 2.7%.

The biogas generated from biodigesters that would otherwise have been released into the atmosphere can be quantified and converted into carbon credits under established carbon crediting methodologies.

Co-benefits of efficient cookstoves

In addition to reducing greenhouse gas emissions, biodigesters create several co-benefits, including:

Renewable energy generation – The biogas generated by biodigesters is a renewable source of energy for cooking, heating or electricity generation.
Improved waste management – Biodigesters convert organic waste into valuable products, preventing waste from rotting in landfills, open dumps, or sewage lagoons where it would generate uncontrolled methane emissions and odours.
Health benefits – Biodigesters help reduce indoor pollution by replacing smoky cooking fuels like firewood or charcoal with cleaner biogas. This significantly lowers respiratory illnesses, especially among women and children in rural areas caused by cooking. Additionally, improved waste management reduces pathogen spread and cuts down on insect and rodent breeding around waste sites.
Energy access – In areas with unreliable energy supplies, biogas systems offer a valuable opportunity to increase energy access. Small-scale household biodigesters allow families to generate their energy independently, improving energy security.
Agricultural benefits – The digestate left after biogas production is rich in nutrients, which can be applied to farmland as organic fertiliser.
Empowerment and gender benefits – In many cultures, women and children often bear the responsibility of collecting firewood and cooking over smokey fires. Biodigesters reduce this time burden, freeing up time for education, income-generating activities or leisure.