Energy Recovery

Learn about new and efficient methods to minimize waste through energy recovery.

There is a wide range of thermal treatment technologies (involving high temperatures) that extract energy from waste while also reducing the volume of waste.

These thermal treatment technologies can be grouped into three broad categories: conventional combustion, advanced thermal treatment, emerging thermal treatment and energy-from-waste Non-Thermal technologies.

Conventional Combustion Technologies:

• Mass-burn – most commonly applied technology; involves the combustion of unprocessed or minimally processed refuse.
• Modular 2-stage combustion – waste fuel is combusted in a starved air environment in the first chamber; the off-gases are moved into the second chamber to combust in an oxygen rich environment.
• Batch combustion – utilize dual chamber controlled air technology; tend to treat smaller amounts of waste vs. other conventional methods since they operate in a noncontinuous manner.
• Fluidized bed combustion – waste fuel is shredded and metals are separated to develop a homogenous solid fuel; combustion occurs within the fluidized bed (composed of an inert material like sand).

Advanced Thermal Treatment Technologies:

• Gasification – although the technology has been used for over a century, it is a recent approach to use MSW as a feedstock. This process heats the waste to produce a syngas (burnable gas) mainly composed of H2 and CO that can be used to generate heat and/or electricity.
• Plasma arc gasification – utilizes an electric current that passes through a gas to create plasma (collection of free-moving electrons and ions) which gasifies waste into simple molecules.
• Pyrolysis – thermal decomposition of feedstock in the absence of oxygen to generate oils and syngas that can be used as a boiler fuel or can be refined for engine fuels or chemicals.

Emerging Thermal Treatment Technologies:

• Gasplasma – uses heated gas and electricity to molecularly disassemble waste, releasing energy and a synthetic gas that can be converted to fuel or combusted for electricity.
• Thermal cracking – also referred to as “fast pyrolysis” as it involves the heating of the waste fuel in the absence of oxygen.
• Thermal oxidation – this process gasifies the fuel source to generate CO and H2 - this synthetic gas can be used to produce liquid fuels (i.e. diesel).
• Waste-to-Fuels – rather than using the syngas (generated through gasification) as a direct energy source, the syngas can be utilized as a feedstock to produce liquid fuels to be used off-site.

Energy-from-Waste Non-Thermal Technologies:

• Anaerobic Digestion – A process that biologically degrades organic materials (like food scraps) in the absence of oxygen. This produces a methane concentrated “biogas” used to generate energy.
• Mechanical biological treatment (MBT) – Describes a range of processes that treat residual waste using a combination of mechanical separation and biological treatment. MBT technologies include MBT with Aerobic Composting, MBT with Biostabilization, MBT with Anaerobic Digestion, and MBT with Refuse-Derived Fuel (RDF) Production.
• Landfill Gas to Energy – Landfill gas is generated when microorganisms breakdown organic waste in landfills. This process involves the capturing of landfill gas (mainly composed of methane) to be used as a source of energy to create electricity or heat.