Top Advancements in Energy Recovery Technologies

Dec 15, 2023

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By 2025, it's expected that global waste will reach 6 million tons per day and a lot of that will go straight to landfills.

In the U.S. alone, 140 million tons of waste find their way into landfills every year. When left to rot, landfill waste produces by-products that contaminate soil, water sources, and plants. Landfills also produce gases including carbon dioxide, water vapor, and traces of oxygen, nitrogen, and hydrogen that can create smog and contribute to climate change.

Energy recovery is a waste treatment process that sees Waste-to-Energy (WtE) technologies convert the chemicals in waste residues into practical forms of energy, such as electricity, heat, or fuel.

WtE technologies can process non-renewable wastes to reduce environmental damage and generate sustainable energy. It's a better option than sending waste directly to a landfill, but it's worth noting that reusing, refurbishing, and recycling should be prioritized whenever possible.

There are three main types of WtE technologies on the market today.

Thermal conversion WtEs are the most commonplace today. Direct combustion (incineration) sees non-recycled materials from the municipal solid waste (garbage) stream produce steam for electric power generation. The technologies that facilitate direct combustion include mass burn facilities, modular systems, and refuse-derived fuel systems.

This confined and controlled burning process reduces the volume of solid waste intended for landfills and generates a renewable energy source. However, because direct combustion is only a viable option when the MSW has a higher calorific value, thermo-chemical techniques are often preferred.

Like thermal energy recovery, this conversion process extracts energy (via techniques including gasification, pyrolysis, and liquefaction) using high temperatures, but is typically much more efficient.

Gasification, for example, produces syngas that can be easily combusted in a gas turbine or engine and generate electricity that is around 30% efficient. Using the thermal energy generated by direct combustion can drive a steam turbine, but with just 15-27% efficiency.

To give another example: Pyrolysis, also known as "plastics to fuel," converts recycled plastics from MSW into synthetic crude oil. This can be further refined into diesel fuel, gasoline, heating oil, or waxes.

This conversion process extracts energy via the bio-decomposition of waste. For example, biogas can be extracted via anaerobic digestion (AD).

AD is more commonly applied to convert agricultural waste like animal manure but it can also be applied to break down wastewater biosolids and food wastes. When the waste is placed into reactors containing microbial communities, it breaks down and produces resultant biogas. The biogas energy can be used much like natural gas to provide heat, generate electricity, and power cooling systems.

Image Credit: Belish / Shutterstock.com