Buyers often assume the choice is "the same genset, different fuel line". It is not. The engine platform is usually shared, but the gas train, derating, treatment and control logic change — and those changes decide whether your plant runs for 8,000 hours a year or fights derated output and fouled oil.
A natural gas genset is specified around a stable, clean, high-methane fuel at fairly consistent pressure. A biogas genset is specified around a variable, wet, contaminated fuel at low and fluctuating pressure. Same block, different fight. Everything below follows from that single difference.
Biogas from a digester typically carries roughly 55–65% methane with the balance mostly CO₂; landfill gas can sit lower, and it moves as the landfill ages. Natural gas is usually in the 85–98% methane range depending on the grid or field. Lower methane means a lower energy content per cubic metre, so the same engine makes less power on the same volumetric flow.
Two consequences worth writing into your specification:
On natural gas, the train between the pipeline and the mixer is mostly a regulator, a filter and a shut-off valve train. On biogas, it becomes a small process plant:
| Contaminant | What it does | Typical response |
|---|---|---|
| Hydrogen sulphide (H₂S) | Acid formation, accelerated oil degradation, corrosion of bearings and liners | Desulphurisation (biological or dry media), plus an oil specification matched to the actual H₂S level |
| Moisture | Free water in the gas train, erratic combustion, condensation in the intake | Cooling and knock-out, gas drying, heating of the gas line where climate demands it |
| Siloxanes (landfill, some waste streams) | Deposits on valves, pistons and turbochargers, glass-like ash in the combustion chamber | Carbon filters or scrubbers sized on a gas analysis, not on a guess |
| Particulates and foam carry-over | Plugged filters and mixers, unstable air/fuel ratio | Coalescing filtration, drip traps, revised filter service intervals |
This is where a biogas project's cost is decided. A "biogas-ready" sticker without a treatment scope matched to your gas analysis is the most expensive sentence in the quotation. We publish our position on this in gas treatment before the engine.
Digester and landfill sites often deliver gas at a pressure that is low and — more importantly — variable. Engines want a stable supply pressure into the gas mixer. The project therefore usually needs a gas booster or at least a properly sized regulator station with buffer volume.
Practical rule: lock the required inlet pressure at the mixer and the guaranteed pressure and flow at the site boundary as two separate numbers in the contract. If only one number is agreed, that argument lands at commissioning — after the container has shipped.
With that page, a supplier can commit to an output figure, a gas consumption figure and a guarantee — which is what your bank and your EPC actually need.
Often yes in principle, but the delivered configuration should be specified for the fuel you will run most of the time. A dual-fuel or changeover configuration needs the gas train, control maps and derating defined for both cases — and the commissioning should be done on the primary fuel.
Frequently yes. Digester and landfill gas pressure is often below what the mixer needs and varies with gas production. Confirm the required pressure at the mixer with your supplier before sizing treatment and boosters.
Almost always treatment scope, derating assumptions and control hardware. Compare the two offers line by line on gas quality basis, treatment equipment, output at your gas composition, and what is excluded.
Tell us the gas composition, flow, pressure and load profile. We reply with a configured proposal: output at your gas, consumption basis and guarantee values.
Request a Quotation