An alternative method of generating energy from biogas is reducing it to biomethane gas, and compressing it for use as motor fuel.
To produce biomethane, carbon dioxide and other impurities are removed from the biogas. The resulting gas has a substantially uniform composition comprising 96 - 98% CH4. Biomethane is similar to natural gas, especially by the proportion of methane content, which ranges from 95 to 98% of the total volume. Used as motor fuel, biomethane has a high calorific value of 50-55 MJ / kg and an octane number of 110, which exceeds those of petrol, which are respectively equal to 44 MJ / kg and 72-85.
Compared with oil-based motor fuel, biomethane has a higher detonation resistance, which allows internal combustion engines to reduce the concentration of harmful substances in the exhaust gases and reduce the amount of deposits in the engine. Due to the absence of the liquid phase, lubricating film is not needed for the engine cylinder, so wear and tear to piston assemblies is halved. As a result, the engine is more reliable and durable. Analysis of toxicity studies on natural gas-powered vehicles shows that the replacement of petrol with biomethane led to a fall in the release of toxic constituents (g / km) in the atmosphere: carbon monoxide by five to ten times, hydrocarbons by three times, nitrogen oxide by 1.5-2.5 times, PAH by ten times, and exhaust fumes by eight to ten times, depending on the type of vehicle.
It should be noted that a vehicle’s gas equipment when powered by liquefied biomethane is identical to the equipment required for running on liquefied natural gas. This enables the speedy production of integrated infrastructure and alternative motor fuels – both liquefied natural gas and liquefied biomethane.