Biogas = mixture of gases produced by anaerobic digestion – the breakdown of organic material.
Biomass= Material from living or once living organisms. Mainly plant based materials. If managed can: take co2 out of environment when growing/releases co2 when burned/decayed = no net increase in atmospheric co2 levels.
Heat sources. Burning produces the energy
Wood burners/boilers
Two main sources of biogas = anaerobic digestion (AD) plants and landfill sites.
Anaerobic digestion =
The natural breakdown of organic matter into carbon dioxide, methane and water, by microorganisms.
Sources= Excrement from farms (cows, chickens etc.), sewage, plant material.
End products = Methane, carbon dioxide gases (biogas), water and some organic material (digestate).
Biogas can be burned to produce both heat and electricity - methane can be used as vehicle fuel or injected into the gas grid - Water can be treated then go back into watercourses - Digestate is used for fertilizer and as an animal food.
Anti-landfill legislation is expected to lead to greater use of AD to deal with organic waste, thereby reducing the amount of waste sent to landfill.
Disadvantages
- High construction costs - lack of expertise to operate plants - Co2 production
Advantages over landfill gas: - AD gas is less complex and has a higher methane content at ~60% (~50% for landfill gas). - Plants can be created close to the source, so less transport.
