Converting waste into energy
Waste-to-energy sources cover a wide spectrum of technologies, including landfill gas, biogas, anaerobic digestion, waste incineration and gasification.
Landfill gas is a mature technology which involves the collection of methane and other gases resulting from waste decomposition within landfills and their conversion into electricity. The process is well understood and has a long, proven track record. The technology is cost competitive, with relatively low upfront and operational costs. As waste decomposition continues long after the landfills have stopped receiving new volumes of waste, this sub-sector will continue to be a viable option despite the gradual shift away from landfill in many jurisdictions, particularly in developed economies which are aiming to recycle and/or incinerate waste rather than send it to landfill.
Biogas / anaerobic digestion represents the biological breakdown of organic matter in the absence of oxygen. Biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material, and crops can all be used to produce biogas. Biogas can then be combusted and a gas engine converts the energy released into electricity and heat. Biogas is used in scale to generate power in some countries (e.g. Germany) or as a vehicle fuel in others (e.g. Brazil). As a renewable fuel it qualifies for renewable energy subsidies in certain jurisdictions.
Waste incineration is a treatment process that involves the combustion of organic substances contained in waste materials. The heat resulting from the incineration process can be used to generate electric power and heat. Certain European countries, such as Denmark, Sweden and Germany, rely heavily on incineration as one of the main forms of waste disposal alongside recycling. Power generated from large-scale waste incineration does not normally qualify for renewable energy incentives, but in certain countries (such as Denmark and Sweden) energy generated from incineration has been an established part of the energy mix for more than a century. With other countries aiming to reduce their reliance on landfills for waste disposal (for example, the UK and Poland), there is significant potential for growth in waste incineration and associated power production.
Gasification is the conversion of biomass and/or other organic waste into synthetic gas (syngas) by reacting the material at high temperatures (>700 °C) without combustion. The resulting syngas is combusted to generate power that is deemed renewable energy. Gasification is at a relatively early stage in its development, with few industrial scale biomass gasification plants currently in operation. There are many demonstration projects around the world and various governments are providing incentives for the development of gasification technology.
An Infinis landfill gas site in the UK