Every day, food scraps are tossed into garbage bags and sent to landfills. But those scraps could actually be transformed into something valuable.
In the U.S., around 97 million metric tons of food waste are thrown away annually. Out of that, about 37 million metric tons are buried in landfills. When food waste breaks down underground without oxygen, it produces methane, a potent greenhouse gas that contributes to climate change. More importantly, when this happens, the nutrients and energy in our food are lost forever.
Instead of dumping food waste in landfills, what if we used it more wisely? My colleagues and I found that many communities already have facilities, like wastewater treatment plants, that can handle organic waste. Some of these plants have the infrastructure needed to process food waste. However, not every facility is suited for it just yet.
Landfills vs. Treatment Plants
Food waste is different from materials like plastics or metals. It can decompose naturally, but when placed in a landfill, it emits greenhouse gases. Landfills capture some methane, yet studies show that up to 58% still escapes into the atmosphere. Instead of contributing to global warming, this waste could be converted into energy or fertilizer.
On the other hand, wastewater treatment plants have systems that already break down organic materials. These facilities often capture methane produced during treatment and can convert it into usable energy. Over the years, many treatment plants have evolved to become resource-recovery facilities that generate power, reclaim valuable materials, and reduce environmental pollution.
What If Food Waste Went to Treatment Plants?
We looked into the effects of diverting food waste from landfills to wastewater plants. By analyzing real data from one such facility that mixed food waste with sewage, we found significant differences in environmental impact. Sending food waste to a landfill emits around 58.2 kilograms (about 129 pounds) of CO2 equivalent per ton. In contrast, the treatment plant achieved net-negative emissions of –0.03 kilograms (1 ounce) per ton treated, capturing over 95% of methane. An advanced treatment facility we studied saw even better results with net-negative emissions of –0.19 kilograms (7 ounces) per ton.
These facilities not only prevent waste from contributing to climate change; they also produce renewable energy that cuts down electricity costs. Plus, the nutrients captured can fertilize about 23 acres of farmland each year, reducing the need for environmentally damaging synthetic fertilizers.
Logistics of Food Waste Collection
Collecting food waste for treatment doesn’t involve grinding it up in sinks. Instead, cities can gather it separately, similar to how recycling is done. For example, San Francisco has been doing this since 1996, and New York City manages the largest curbside organics collection program in the U.S., serving 3.4 million households.
At the wastewater plant we studied, trucks deliver food waste to be processed. Nonorganic materials like plastics are removed, and the remaining mixture is combined with sewage solids. This mixture is then treated in anaerobic digesters, which are sealed tanks that use microorganisms to break down the organic material. The resultant methane is captured for energy use, while the nutrient-rich solid can be transformed into useful products like fertilizer.
Our analysis showed that adding food waste didn’t overwhelm the treatment plant. In fact, it processed 107,320 tons of food waste each year, which was 38% of the county’s total food waste generation. The added food waste only increased the plant’s capacity by about 0.43%, and at times, improved its efficiency.
Economic Considerations
City officials often worry about the costs of implementing such systems. Wastewater treatment is expensive, and many existing plants may be near full capacity. However, our research indicates that managing food waste in wastewater plants can be economically viable. Towns already pay landfills “tipping fees” based on the amount of waste they send. Wastewater plants could charge similar fees.
Additionally, they can monetize the methane and sell the fertilizer produced, creating a potential revenue stream. This means they could still be profitable even with lower fees than landfills. Not every plant is equipped to accept food waste immediately, but larger, well-funded facilities could implement these changes more readily. Smaller plants may need upgrades, requiring planning and investment.
Ultimately, our findings suggest that the barriers are not technological or financial. The essential infrastructure to transform food waste into a resource already exists. Cities are already managing organic matter daily and operating complex biological systems. With the right adjustments, these facilities can effectively handle food waste in a way that benefits the environment and the economy.
For more detailed insights on this topic, you can check the original research published in Renewable and Sustainable Energy Reviews.
Source link
anaerobic digesters,composting,food waste,greenhouse gas emissions,landfills,methane,tipping fees,wastewater treatment plants
