Every day, food scraps are put into garbage bags, hauled away, and forgotten. Yet this waste can actually be turned into valuable resources.
In the United States, approximately 97 million tons of food waste are discarded each year, and around 37 million tons end up in landfills.
Once buried underground, these organic materials decompose without oxygen and release methane, a short‑lived but highly potent greenhouse gas.
Meanwhile, the nutrients and energy stored in food are lost forever. But there is a better alternative. Research conducted by my colleagues and me shows that communities across the country already operate facilities designed to process organic matter: wastewater treatment plants. Many large, well‑funded wastewater treatment plants already have the infrastructure to handle food waste, even though not all plants are ready to do so.
Landfills are not designed to handle food waste.
Food waste is fundamentally different from plastic, metal, or glass. It is organic and can decompose naturally. However, when buried in landfills, its decomposition releases large quantities of greenhouse gases.
Modern landfills are engineered to capture methane emissions, yet even the most efficient systems still allow nearly 58% of the methane to leak into the atmosphere. This food waste, which could otherwise be converted into energy or fertilizer, is instead contributing to global warming.
In contrast, wastewater treatment plants treat wastewater by using microbial communities to naturally break down organic matter. Many wastewater treatment plants also capture methane produced during the treatment process and convert it into usable energy. Others recover nutrients such as phosphorus, which can be processed into agricultural fertilizers. Over time, many wastewater treatment plants have evolved from simple sanitation systems into resource recovery facilities that generate electricity, recycle materials, and reduce environmental pollution.
These existing systems are already capable of processing organic matter and can handle food waste as well.
What happens to food waste when it is delivered to a treatment plant?
Our research investigated what would happen if food waste were sent to wastewater treatment plants instead of landfills. We used real data from a large wastewater treatment facility that processes both food waste and sewage.
When we compared greenhouse gas emissions for the same food waste composition, we found that sending food to landfills emits 58.2 kilograms (129 pounds) of CO₂ equivalent per ton of food waste.
By comparison, we examined a conventional wastewater treatment plant—the most common type in the United States. This plant achieved a net emission of -0.03 kilograms (about 1 ounce) of CO₂ equivalent per ton of food waste processed. In contrast to landfills, which capture roughly 50% of methane, this plant captures more than 95%, reducing greenhouse gas emissions into the atmosphere.
However, we found that the advanced treatment plant we studied reduced emissions even further. Our analysis showed that the advanced facility achieved a net emission of -0.19 kilograms (about 7 ounces) of CO₂ equivalent per ton of food waste.
Both conventional and advanced treatment plants achieve these benefits in similar ways. Regardless of the plant type, processing one ton of food waste prevents the release of 58.2 kilograms of CO₂ equivalent that would otherwise be emitted in landfills. These plants capture biogas to generate electricity, reducing the need to purchase power from the grid. They also recover enough nutrients to fertilize approximately 23 acres of farmland per year, thereby lowering the demand for synthetic fertilizers. The extraction and production of synthetic fertilizers are highly energy-intensive.
Logistics operation mode
Delivering food waste to wastewater treatment plants does not mean people pour food scraps down drains or grind them using garbage disposals. At the plant we studied, food waste is collected separately, just like recyclables or yard waste, and then transported to the treatment plant by truck. Our emissions calculations do not include truck emissions, as trucks are also used in other food waste management approaches.
Some cities have begun collecting food waste by truck and transporting it to composting facilities. San Francisco has been doing this since 1996. New York City has the largest curbside organic waste collection system in the United States, which composts food waste from 3.4 million households.
At the wastewater treatment plant in the southeastern United States that we studied, trucks deliver food waste to a receiving station, where it is processed to remove plastics, metals, and other inorganic materials before being mixed with wastewater solids into a slurry. This mixture is then fed into anaerobic digesters—sealed tanks where microorganisms break down organic matter.
The methane produced is captured and used to generate electricity and heat. The remaining solids are nutrient‑rich and can be used to produce valuable materials such as fertilizers.
We also found that adding food waste did not overload the plant or cause operational problems. The facility processed all of the county’s landfilled food waste—107,320 tons per year, accounting for 38% of the county’s total food waste. Since food waste is less dense than wastewater, it only increased the plant’s daily treatment capacity by 0.43%. The plant consistently met regulatory standards for effluent water quality. Moreover, in some cases, treatment efficiency even improved due to the additional organic matter, which boosted the system’s biological treatment processes.
The Economics May Surprise Cities
Local officials and taxpayers often worry about the potential costs of such programs. Wastewater treatment is already expensive, and existing treatment plants in communities may be near capacity.
However, our analysis shows that processing food waste at wastewater treatment plants is economically viable. Towns already pay so‑called tipping fees to landfills and incinerators based on the weight of waste. Wastewater treatment plants can also charge these fees.
They can also sell or use the methane produced on‑site, and sell fertilizers made from the by‑products. This extra revenue means the plant can be profitable even with lower treatment fees than landfills.
Not all wastewater treatment plants can accept food waste immediately. The plant we analyzed is large and well‑equipped. Smaller wastewater treatment plants may need to acquire or upgrade equipment, which requires planning and local investment.
Our overall conclusion is that the limiting factor is not technology or funding. The core systems to convert food waste into recoverable resources already exist: cities process organic matter every day and operate sophisticated biological treatment systems. Our evidence shows that these facilities can indeed process food waste in ways that are both environmentally sustainable and economically affordable.
