Reducing Methane From Food Waste is a Climate Solution That Can Make a Difference Now

One impactful climate initiative that could realistically make progress over the next few years is tackling organic waste, especially food waste, to lower methane emissions. It just gained new momentum with the Reducing Methane from Organic Waste Declaration at the global U.N. COP29 climate talks in Azerbaijan, signed by some 30 countries including the United States. And there’s a decent outlook for implementing it in the U.S., even if the second Donald Trump administration pulls us out of the United Nations climate process again. This is partly because implementation will happen mostly on the municipal level. Also, while Trump has signaled he intends to roll back climate actions taken under the Joe Biden administration, his first administration worked to cut food waste, and his second one may well do it again.
 
Politics aside, there’s growing recognition that food waste rotting in landfills is a huge problem for the climate, because it generates methane-rich biogas as it decomposes, much of which escapes into the atmosphere. In fact, landfills are the third largest source of methane emissions in the U.S., largely due to the food waste dumped in them. Methane is 84 to 87 times as strong a greenhouse gas as carbon dioxide over a 20-year period. Acting fast to cut methane emissions is the strongest lever we have to stave off the most catastrophic effects of a warming planet.
 
So, how can we avoid landfilling food waste? For starters, at the national level, half of the food that Americans throw out as “waste” is perfectly edible and should be redistributed instead of discarded. Of the other, inedible half, we need to compost more. Fruits, vegetables, and yard waste make good feedstocks for backyard and community-scale composting, which releases negligible methane. But fats, oils, grease, meat, fish and dairy can only be composted at large-scale commercial facilities, and NASA satellite data from California shows these sites on average emit nearly as much methane as landfills.
 
We need another way to keep inedible, non-compostable food waste out of landfills and process it without emitting methane. Fortunately, many cities and towns have a secret weapon that can do this: wastewater plants. Almost invisible to the public, there are over 15,000 wastewater plants that do the inglorious but indispensable work of processing our sewage. Many of them could also cut methane from our food waste and make a huge contribution to lowering greenhouse gas emissions using municipal authority and existing critical infrastructure.
 
Across the U.S., 475 large wastewater plants already use airless tanks called anaerobic digesters (ADs) to process sewage sludge. As the sludge decomposes, it produces methane-rich biogas, which is either captured for use as an energy source or flared off. Most anaerobic digesters have extra capacity that can also process (or “co-digest”) food waste with the sludge. The food waste acts like rocket fuel. It boosts production of methane-rich biogas, which can be used to produce electricity or renewable natural gas (RNG), an ultra-low-carbon fuel which displaces carbon- and methane-intensive fossil fuels. The more food waste gets diverted from landfills and processed in digesters, the more RNG they produce, and the more they cut methane emissions from both the waste and energy sectors.
 
How much more? The nonprofit Energy Vision’s primer on wastewater anaerobic digesters calculates that the 50 largest U.S. wastewater plants already equipped with digesters could potentially co-digest 7.5 percent of the nation’s food waste. For example, Brooklyn’s Newtown Creek wastewater plant can co-digest up to 500 tons of food waste per day. More than 130 U.S. wastewater plants do some amount of co-digestion, but with some retrofits, hundreds more could also begin to process food waste. If most of the 475 U.S. wastewater plants using digesters did this, they could handle about 10 percent of all U.S. food waste and avoid massive methane emissions — about 5 million metric tons of carbon dioxide equivalent annually.  That's like taking over a million fossil-fuel powered cars off the road.
 
Starting with the existing urban and suburban wastewater infrastructure saves years and tens of millions of dollars per project that would otherwise have to be spent to build them from scratch. It takes far less time and money to do the retrofits needed to receive, mix and pipe food waste into existing anaerobic digesters, with an average cost of $500,000 to $2.5 million depending on scale and geography.  That’s climate action on a budget that municipalities can cope with. 

In fact, they can recoup their expenses and earn net income by charging tipping fees to take in food waste, and by monetizing the expanded biogas output as a clean energy source. The biogas can generate onsite power, lowering the plant’s operating costs, and/or be upgraded to RNG and sold to the gas grid or dispensed locally as vehicle fuel. Some plants have recently started to tap both new income streams, like the Pleasant Grove wastewater plant in Roseville, California. It uses a portion of its biogas to fuel microturbines that power the plant, while the rest is upgraded into RNG, which is dispensed onsite to fuel a portion of the city’s fleet of garbage trucks.
 
We need to cut methane emissions rapidly to avoid the worst effects of climate change. Sending our non-compostable food waste to wastewater plants that already have anaerobic digesters can be a quick, high-impact win at a low price. It’s a clean energy and climate action strategy municipalities can undertake themselves, which also happens to align with the Trump administration’s interest in cutting food waste and the U.N.’s declaration on reducing methane emissions from organic waste — a rare triple win that makes it implementable and replicable now.