New and Used Biogas Generators for Sale
Jenbacher, MWM, Caterpillar, MTU, Waukesha & more!
USP&E Biogas Generator Inventory at a Glance
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Typical biogas inventory: Gas engine generator sets from 1 MW to 4 MW+ per unit, configured for landfill, digester, sewage and agricultural gas
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Brands supplied: INNIO Jenbacher, MWM, Caterpillar, MTU, Waukesha, Deutz
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Fuel types: Landfill gas, anaerobic digester gas, sewage and wastewater gas, agricultural and manure gas, food waste gas, coal mine gas, flare gas
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Methane tolerance: Engines operate on gas down to approximately 35% methane with appropriate derating
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Configurations: Continuous duty, CHP and trigeneration, island mode, grid-parallel, containerised
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Frequencies: 50 Hz at 1,500 rpm and 60 Hz at 1,800 rpm
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Gas treatment: H2S removal, siloxane removal, moisture separation, particulate filtration, gas boosting
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Lead time: Immediate to 90 days for stocked units; 12 to 18 months for EPC turnkey plants
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Applications: Municipal landfills, wastewater treatment works, agricultural digesters, food and beverage processing, abattoirs, distilleries, sugar mills
- Compliance: ISO 9001:2015, ISO 45001:2018, OFAC and FCPA compliant
Biogas is methane produced by the anaerobic decomposition of organic matter. It comes out of landfills, sewage digesters, agricultural slurry, food waste and abattoir effluent — waste streams that otherwise represent a disposal cost and, in the case of methane venting, a serious environmental liability.
A biogas generator converts that waste stream into electricity. The fuel cost is effectively zero or negative, because the alternative is paying to flare or treat the gas.
But biogas is not natural gas, and this is where most projects go wrong. Typical biogas is 50% to 70% methane with the balance mostly carbon dioxide, plus trace contaminants that will destroy an unprepared engine. The engine is the easy part. Gas treatment is what determines whether the plant runs for twenty years or fails in its second.
Landfill Gas to Energy
Landfills generate methane continuously for decades after closure. Under most modern regulatory regimes that gas must be captured and destroyed rather than vented, because methane’s global warming potential is many times that of carbon dioxide. Once it is being captured anyway, generating electricity from it costs little more than flaring it.
The economics. Fuel cost is zero. Capital cost is the gas collection field, treatment skid, generators and grid connection. Revenue comes from electricity sales or avoided grid purchase, and in many jurisdictions from carbon credits or renewable energy certificates.
The gas. Landfill gas is typically 45% to 60% methane, and declines as the site ages. Engines can run down to roughly 35% methane with derating of 20% to 35% below nameplate as the control system adjusts air-fuel ratio and ignition timing to hold stable combustion on lower-energy fuel.
The complication. Landfill gas carries the highest contaminant load of any biogas stream, because consumer plastics, cosmetics and construction sealants all end up in the waste mass. Siloxane concentrations in landfill gas average from 0.2 mg/m³ to around 10 mg/m³ but can reach 140 mg/m³. This requires serious treatment, covered below.
Sizing to a declining resource. Gas production peaks and then falls over decades. Plants are commonly built modular so units can be removed as flow declines, rather than running one large engine at increasingly poor part-load efficiency.
Digester Gas, Sewage Gas and Agricultural Biogas
Wastewater treatment works. Sewage sludge digesters produce a steady, predictable gas stream, typically 60% to 65% methane. Because flow and quality are consistent, treatment design is simpler than landfill. Siloxane contamination is persistent but stable, coming from detergents and personal care products in municipal wastewater. Most treatment works can generate a substantial share of their own electrical demand, and the CHP heat is used to warm the digesters themselves.
Agricultural digesters. Manure, slurry, silage and crop residue feed purpose-built digesters. Gas is typically 50% to 60% methane. Critically, animal waste digesters usually contain little or no siloxane unless off-site waste is co-digested, which simplifies treatment considerably. Hydrogen sulfide is the main concern, and it can be high where the substrate is protein-rich.
Food and beverage processing. Abattoirs, breweries, distilleries and dairies produce high-strength effluent that digests well. Gas quality is usually good, though slaughterhouse waste and poultry litter produce elevated H2S and ammonia because of their protein content.
Sugar and agro-processing. Vinasse and press mud from sugar and ethanol production support digesters that run through the crushing season.
Gas Treatment: The Part That Determines Plant Life
This is the section most equipment suppliers skip, and it is the single largest determinant of whether a biogas project succeeds.
Hydrogen sulfide (H2S). During combustion, sulfur compounds combine with water vapour to form sulfuric acid. That acid attacks bearings, liners, aftercooler cores and any copper-containing component, and it acidifies the lubricating oil. Jenbacher and MWM typically specify H2S below 50 ppm at the engine. Untreated agricultural or sewage gas can be many times that. Removal is by iron oxide media, activated carbon, or biological scrubbing.
Siloxanes. Volatile methyl siloxanes burn to form silicon dioxide — effectively fine glass dust — which coats valves, liners, pistons and spark plug electrodes. It is abrasive, it insulates, and it accumulates. Caterpillar and Cummins both publish a threshold around 28 to 30 mg/m³ for landfill gas configurations, and Caterpillar requires upstream siloxane removal to qualify for warranty cover on landfill installations. Untreated siloxane can reduce engine performance by over 20% and voids OEM warranties across Jenbacher, Caterpillar, MAN and MWM. Removal is by chilling and condensation, activated carbon or specialist adsorbent media.
Moisture. Biogas leaves a digester or landfill saturated. Condensation in fuel lines causes unstable combustion and carries contaminants into the engine. Chillers and coalescing filters handle this.
Ammonia. Elevated in protein-rich substrates such as slaughterhouse waste, poultry litter and sewage sludge. Manufacturer limits are commonly below 50 ppm.
Particulates. Coalescing and particulate filtration protects everything downstream.
A worked consequence. Running crude, untreated landfill gas can shorten engine service life to a matter of hours rather than years. On properly conditioned gas, a biogas engine reaches 30,000 to 60,000 operating hours before major overhaul, comparable to a natural gas engine in baseload service. On poorly conditioned gas that can fall to 15,000 hours or less. A single H2S-driven overhaul on a Jenbacher or MWM unit runs to six figures in parts alone, before counting lost generation.
USP&E scopes gas treatment as part of every biogas project rather than leaving it to the buyer.
Biogas Generators by Manufacturer
INNIO Jenbacher — The dominant platform in biogas worldwide. Type 2, 3, 4 and 6 engines are available in biogas configuration, designated GS-B.L and similar. Jenbacher’s robust, relatively low-speed design tolerates fluctuating gas quality better than high-speed engines, which is precisely what biogas demands. USP&E stocks Jenbacher units including the J420 GS-B25 at 1.4 MW.
MWM — TCG 2020 and TCG 3016 platforms in biogas configuration, well proven on agricultural and sewage gas across Europe and increasingly in Africa.
Caterpillar — G3516 and G3520 series in landfill and biogas configurations. The G3520C and G3520E suit higher-output sites; the G3516 is the common choice for landfills where gas production is still building, because it scales as the field matures. USP&E stocks a 1 MW G3516.
MTU — The 4000 series in gas configuration. USP&E stocks a 2 MW 20V4000-GS and a 1.7 MW 12V4000L32F.
Waukesha — VHP and APG series, long established on landfill and field gas where contaminant tolerance matters most.
CHP, Trigeneration and Total Plant Efficiency
A biogas engine converts roughly 40% to 43% of fuel energy into electricity — slightly below a natural gas engine because of the lower energy density of the fuel. The remaining energy leaves as heat in the jacket water and exhaust.
Recovering that heat lifts total plant efficiency to 85% to 90%.
Digester heating. The most valuable use of recovered heat on a digester site is warming the digester itself. Mesophilic digestion requires around 37°C and thermophilic around 55°C, and in cooler climates that heat demand is continuous. Using engine heat rather than a boiler makes the plant substantially more efficient overall.
Process heat. Abattoirs, dairies and distilleries all need hot water. Recovered jacket heat serves it directly.
Trigeneration. Adding an absorption chiller converts recovered heat into cooling — relevant for food processing and cold storage co-located with a digester.
Biogas Power in Frontier Markets
Municipal landfills. African and South Asian cities are building formal landfill infrastructure with gas capture obligations. Once gas is captured, generation is the obvious next step. The Johannesburg landfill gas to energy project is a regional example of the model.
Wastewater treatment. Treatment works are large, continuous electricity consumers on constrained grids. Digester gas generation offsets a substantial share of that draw and stabilises operating cost.
Agro-processing. Sugar mills, distilleries, abattoirs and poultry operations across Africa produce concentrated organic waste streams with real digestion potential, in locations where grid supply is unreliable and diesel back-up is expensive.
Carbon finance. Methane destruction with energy recovery is among the most straightforward project types to register for carbon credits, which can materially change project economics.
USP&E delivers projects across Ghana, Nigeria, the Democratic Republic of Congo, Zambia, Mozambique, Kenya, South Africa, Iraq and the Caribbean.
Biogas Plant EPC and O&M
EPC scope: feedstock and gas resource assessment, gas yield modelling, collection field design for landfill, gas treatment skid specification and installation, engine installation and alignment, heat recovery, MV switchgear and grid interconnection, flare and safety systems, control integration, commissioning and emissions compliance testing.
O&M scope: operator staffing and training, gas quality monitoring and treatment media replacement, oil analysis with silicon and sulfur tracking, shortened oil change intervals appropriate to gas quality, spark plug management, scheduled top-end and major overhauls, spares holding, availability guarantees.
Oil analysis is not optional on biogas. Silicon content in the oil frequently dictates the change interval rather than hours run, with most landfill operations using 100 to 120 ppm silicon as a condemning limit. Sulfur-driven acidification requires specific oil formulations and shortened intervals. An O&M contract written for natural gas duty will destroy a biogas engine.
Typical EPC delivery for a 1 MW to 5 MW biogas plant is 12 to 18 months from notice to proceed, assuming feedstock and permitting are secured.
Biogas Generators by Power Output
Below 1 MW — Small agricultural and food-processing digesters. Often containerised, frequently CHP-led where the heat matters as much as the power.
1 MW to 2 MW — The volume band for medium landfills, municipal wastewater works and larger agricultural digesters. USP&E stock in this band includes Jenbacher J420 and Caterpillar G3516 units.
2 MW to 4 MW — Larger landfills and multi-unit digester sites. USP&E stock includes MTU 20V4000-GS units at 2 MW.
Above 4 MW — Multi-unit arrays. Landfill sites are almost always built as multiple smaller units rather than one large machine, so capacity can be removed as gas production declines over the site’s life.
Buying a Used Biogas Generator
Get a gas analysis first. Methane percentage, H2S, siloxanes, ammonia, moisture and particulates. Every subsequent decision depends on it, and no reputable supplier can specify an engine without it.
Confirm the engine is in biogas configuration. A standard natural gas engine is not a biogas engine. Biogas variants carry hardened valve seats and liners, different oil specification, adjusted compression ratio and modified control mapping. Converting a natural gas unit is possible but is engineering work, not a settings change.
Ask what fuel it ran on. A unit that ran on clean agricultural gas has had an easier life than one that ran on landfill gas. Ask for oil analysis history, specifically silicon and sulfur trends.
Check overhaul history against gas quality. Hours alone mean little. An engine with 30,000 hours on treated digester gas may be in better condition than one with 15,000 on untreated landfill gas.
Budget for the treatment skid. It is not an accessory. On landfill gas in particular, treatment can be a significant fraction of total plant cost, and skipping it voids OEM warranty.
Derating. Confirm the output you will actually achieve on your gas, not the nameplate. At 35% to 45% methane, expect 20% to 35% below nameplate.
USP&E supports gas analysis interpretation, pre-purchase inspection and third-party verification.
USP&E Biogas Track Record
USP&E supplies biogas generator sets with gas treatment, and delivers EPC and O&M in-house across Africa, the Middle East, Central Asia and the Caribbean. Equipment is held outright rather than brokered, and gas treatment is scoped as part of every project rather than left to the buyer.
Biogas Generator FAQ
Where can I buy a used biogas generator for landfill or digester gas?
USP&E supplies new and used biogas generator sets from around 1 MW to 4 MW per unit, configured for landfill gas, anaerobic digester gas, sewage gas and agricultural gas. Brands include INNIO Jenbacher, MWM, Caterpillar, MTU and Waukesha. Every project is scoped with the gas treatment train required for the specific fuel, because engine selection alone does not make a viable biogas plant. Stocked units ship in immediate to 90 days, and USP&E delivers EPC and long-term O&M including gas quality monitoring.
What is the difference between a biogas generator and a natural gas generator?
Mechanically they are similar, but a biogas engine is built to survive a far more hostile fuel. Biogas is typically 50% to 70% methane against natural gas at over 90%, with the balance mostly carbon dioxide, and it carries hydrogen sulfide, siloxanes, moisture and ammonia. Biogas variants use hardened valve seats and liners, different oil specification, adjusted compression ratio and modified control mapping, and they require a gas treatment skid upstream. A standard natural gas engine run on untreated biogas will fail quickly and its warranty will be void.
How does a biogas generator work?
Organic matter decomposes anaerobically in a landfill, digester or lagoon, producing methane-rich gas. That gas is collected, then passed through a treatment train that removes moisture, hydrogen sulfide, siloxanes and particulates. The conditioned gas feeds a spark-ignited reciprocating engine, which drives a synchronous alternator at 1,500 rpm for 50 Hz or 1,800 rpm for 60 Hz. Jacket water and exhaust heat can be recovered for digester heating or process use, lifting total plant efficiency to 85% to 90%.
What methane content does a biogas generator need?
Most industrial biogas engines operate on gas from roughly 35% methane upwards. Typical landfill gas runs 45% to 60% methane, digester gas 60% to 65%, and agricultural gas 50% to 60%. Below about 45%, expect derating of 20% to 35% below nameplate output as the engine management system adjusts air-fuel ratio and ignition timing to maintain stable combustion. Methane content in landfill gas declines as a site ages, which is why landfill plants are usually built as multiple smaller units rather than one large machine.
Why do siloxanes matter in biogas?
Siloxanes are volatile organic silicon compounds originating from cosmetics, detergents, plastics and sealants. During combustion they oxidise into silicon dioxide — abrasive glass-like dust — which coats valves, cylinder liners, pistons and spark plug electrodes. The result is accelerated wear, fouled plugs, lost efficiency and eventually component failure. Caterpillar and Cummins both publish a threshold around 28 to 30 mg/m³ for landfill gas configurations, and Caterpillar requires upstream siloxane removal for warranty cover. Untreated siloxane can cut engine performance by over 20%.
How is hydrogen sulfide removed from biogas?
Hydrogen sulfide combines with water during combustion to form sulfuric acid, which corrodes bearings, liners, aftercooler cores and copper components, and acidifies the lubricating oil. Jenbacher and MWM typically specify below 50 ppm at the engine. Removal methods include iron oxide media, activated carbon adsorption, biological scrubbing and, on larger plants, chemical scrubbing. The right choice depends on inlet concentration and gas flow. H2S removal also incidentally reduces siloxane concentration by 10% to 30%.
How long does a biogas engine last?
On properly conditioned gas, a biogas engine reaches 30,000 to 60,000 operating hours before major overhaul, comparable to a natural gas engine in baseload service. On poorly conditioned gas that falls to 15,000 hours or less, and on crude untreated landfill gas an engine can be destroyed in a fraction of that. Gas treatment quality, not engine brand, is the dominant variable in biogas plant life.
How efficient is a biogas generator?
Electrical efficiency is typically 40% to 43%, slightly below a natural gas engine because biogas has lower energy density. In combined heat and power configuration, recovering jacket water and exhaust heat, total plant efficiency reaches 85% to 90%. On digester sites the recovered heat is usually used to warm the digester itself, which requires around 37°C for mesophilic or 55°C for thermophilic operation, making CHP the default configuration rather than an upgrade.
Is biogas generation renewable?
Yes. Biogas is produced from organic matter that would decompose and release methane regardless, so capturing and combusting it converts methane into carbon dioxide, which has a substantially lower global warming potential. The carbon released was recently absorbed from the atmosphere by the source biomass, making it biogenic rather than fossil. Methane destruction with energy recovery is one of the more straightforward project types to register for carbon credits, which can materially improve project economics.
Does USP&E provide EPC and O&M for biogas plants?
Yes, both in-house. EPC scope covers feedstock and gas resource assessment, gas yield modelling, landfill collection field design, gas treatment skid specification and installation, engine installation, heat recovery, switchgear, grid interconnection, flare and safety systems, commissioning and emissions testing. O&M covers gas quality monitoring, treatment media replacement, oil analysis with silicon and sulfur tracking, shortened oil change intervals matched to gas quality, spark plug management, overhauls and availability guarantees. An O&M regime written for natural gas duty is not adequate for biogas.