Questions about raw biogas generators

It is a generator whose engine burns biogas straight from the digester, without the gas-cleaning step (scrubbing) that is normally used to remove H₂S first. Biogas is mostly methane and carbon dioxide, made when bacteria break down manure and other organic waste in the absence of oxygen. More on how digesters work: US EPA: frequent questions about anaerobic digestion.

H₂S is a corrosive, poisonous gas found in biogas. In an engine it corrodes metal by sulphuric acid attack and sulphidation. This is why biogas is usually scrubbed before it goes into an engine. See also this Cornell University fact sheet on H₂S in biogas. Our unit is designed to run without that scrubbing step, up to about 2,000 ppmv of H₂S, and the design is based on real-biogas tests.

It depends on what feeds the digester. Raw biogas commonly holds 200 to 1,500 ppmv of H₂S (parts per million by volume) and can reach 10,000 ppmv. Reciprocating engines are generally rated for about 200 ppmv, while gas turbines tolerate up to about 5,000 ppmv (Potter and Chambers, 2002; Montenegro, 2026). Our design is based on real-biogas tests at up to about 2,000 ppmv of H₂S.

It runs on biogas and diesel together. The biogas is mixed with the air entering the engine and diesel is injected to ignite it, because biogas cannot ignite by compression alone (Ambarita, 2017). The two fuels supply equal shares of the energy, 1:1 by heating value (Montenegro, 2026), so you buy half the diesel of a diesel-only generator.

Four reasons. Diesel engines can burn biogas in dual-fuel mode without major modifications (Ambarita, 2017). Their oils have a higher total base number (TBN, about 10 to 14 mg KOH/g against 7 to 10 for petrol engine oils), so they neutralise more acid before the oil turns corrosive (Fubex Lubricants, 2025). Their higher compression ratio (about 20:1 against 8:1) keeps the cylinder walls hotter, further from the temperature where the wet biogas condenses (Montenegro, 2026). Diesel generators and mechanics are already everywhere: in Malawi, off-grid diesel capacity is about as large as the whole grid, 0.5 GW each (Ferris, 2022), making replacement parts and maintenance expertise widely available.

Half of what a diesel-only generator would use, as a first estimate. Use the savings calculator with your own diesel use and price. It is an estimate, not a guarantee: the real figure depends on your biogas supply and how you run the unit.

Farms, cooperatives, NGOs and development programmes that already have a biogas digester and want electricity from it. Biogas programmes across Africa have installed thousands of household digesters (see energypedia: African Biogas Partnership Programme); our unit is for turning that gas into electric power. For technical background on biogas worldwide, see IEA Bioenergy Task 37: Energy from Biogas.

Because electricity is scarce there. The World Bank reports that about 25.9% of Malawi's population has electricity access today, with 11.3% on the national grid and 14.6% on off-grid solutions (World Bank, May 2026). Farms with a digester already have a local fuel; the missing piece is an engine that can use it. Its grid is about 98% hydropower, and floods in the rainy season can force plants offline and cut supply (Taulo et al., 2015).

The service is very simple: engine oil and filters, every 200 operating hours. There is no gas-cleaning kit to service, because the unit runs on raw biogas.

Not yet. This page shows concept renders only. The design is based on real-biogas tests and the final design is due in Q3 2027. You can request a quote and register interest now, and we reply within 72 hours. Price is on request.