Furthermore if the CO 2 contained in the waste gas of the purification process is recovered, credit may be earned for the saving of fossil fuel that is normally combusted to produce CO 2 . Membrasep's membrane-based biogas purification process is able to do exactly that. Trends in the UK and North America By increasing energy efficiencies, emissions can be drastically reduced. When used in conjunction with a sewerage digester, the cooling water of the engine is recycled through the digester to heat the process and enhance gas production. The shift towards zero effluent processes includes the recovery of water from digesters utilising methane, produced from biomass, through combustion in a power-generating engine, reclaiming CO 2 in exhaust gas, and recovering waste heat from engines.
Vehicles are the fastest growing source of emissions.
All large engines are diesel and emit carcinogenic particulate matter as black smoke. Westport predicts that all diesel engines in the US will be converted to NG by 2010. It is projected that international airports will double their capacity within the next ten years. To prevent and reduce airport pollution the focus is now on using ground vehicles powered by NG or other alternative fuels. The next generation of vehicles will be electrically powered by fuel cells using hydrogen and emitting only water vapour.