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Waste-to-energy benefits highlighted in new research

A new study has assessed the environmental benefits of various waste-to-energy production pathways which avoid the emission of methane and other harmful pollutants.

Methane gas has a global warming impact 30 times higher than carbon. Organic waste such as yard trimmings, paper, wood and food produces millions of tons of methane emissions at landfills in the US each year. The new study, by Uisung Lee from the Department of Energy’s Argonne National Laboratory, assesses the potential of this waste as a means to produce renewable natural gas and liquid fuels.

"By using waste to produce energy, we can avoid emissions from landfills and potentially reduce the need for additional landfills across the country." - Uisung Lee explains.

“Our study shows that using what would otherwise become landfill waste to produce fuel typically generates less greenhouse gases than simply letting the waste decompose.”

Although the operators of landfills are required to combust landfill gas, it is impossible to perfectly capture the gas, meaning large amounts of methane, which has a global warming impact 30 times higher than carbon, still escape into the atmosphere.

Methods such as anaerobic digestion and fermentation, hydrothermal liquefaction, pyrolysis and gasification are all able to create fuel and energy from municipal waste, producing the likes of renewable natural gas, bio-char and fungible fossil fuel replacements.

"By using waste to produce energy, we can avoid emissions from landfills and potentially reduce the need for additional landfills across the country," said Lee, noting that in 2014 the US hauled an annual estimated 32 million metric tons of food waste resources to landfills, or about 70 trillion pounds of waste, according to the Department of Energy.

Crucially, Lee’s study argues that it is possible to collect waste feedstock using current infrastructure for collection and separation, lowering the cost of waste-derived energy. Meanwhile, a recent DOE report observed that waste feedstocks are actually available at a low or negative price, once tipping fees are taken into consideration.

Environmental benefits

Lee’s study makes clear that converting waste to energy has clear environmental benefits when compared to landfills that collect and combust waste gas. These benefits become even more apparent when the approach is applied to waste which would typically be taken to smaller landfills that collect lower amounts of methane, releasing much of it into the atmosphere.

It’s noted in the research that diverting and using waste from smaller landfills could have additional economic, logistical and operational challenges, however.

"These are the areas where we can realise the greatest environmental benefits while also producing transportation fuels," Lee said. He added that transportation fuels that displace fossil fuels can enhance energy independence and reduce fossil fuel use and greenhouse gas emissions.

Lee’s study has been published in the Journal of Cleaner Production

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