Food Waste Decomposition Systems

By: Cassandra Kliewer 

Sustainable Associate

Josie Plaut 

Associate Dirtector

Food Waste

In 2010, America wasted an estimated 34 million tons of food and only about 3% of that waste was diverted from landfills. Food
digesters, which turn food waste into compost and gray water, are especially well-suited for large commercial kitchens like those found in hospitals and university campuses. Instead of putting food waste into landfills, food digesters turn waste food, into new soil and reduce the burden on municipal waste water treatment facilities.  Two waste audit studies, conducted by The Institute for The Built Environment for Rocky Mountain National Park, show that between 16-30% of the park’s waste, by weight, is food waste.

Food Digesters

Food digesters can either work with or without water. Both systems use an additive to accelerate the process of decomposition. Normally, the decomposing process would take a month, but instead the additive processes the food in 24 hours. The water-based process produces compost and gray water, which is water that is similar to the waste water from sinks and showers.  In a building that is connected to a municipal waste water treatment facility, gray water is easily treatable by the municipal waste water systems.  Gray water can also be treated on site and used for things like landscape irrigation.  Conversely, the dry system is evaporation-based and food waste is mixed with a decomposing additive. Both systems provide easy and sustainable solutions to landfill waste.
Food digesting systems produce nutrient rich material that can be used as compost to fertilize soil for landscapes. Since the dry system can digest food within 24 hours, a rapid source of compost for landscaping is readily available. If the building does not need compost, the facility can reach out to the community and provide compost for landscaping purposes elsewhere. Another benefit of having a food
digester is that it reduces the amount (and cost) of waste that would normally go to a landfill. Since food waste is composted on site with a food digester, there is also a benefit to reduced transportation cost and emissions.  In addition to saving dollars and emissions, and perhaps most importantly, wasted food is kept in the nutrient cycle to rebuild soil and is kept out of landfills where it contributes to methane gas production.

The Future of Food Waste

Various government officials have noticed the impact of food waste and are taken measures against food waste.  Massachusetts has taken measures to ban food waste from big food wasters (schools, hospitals, grocery stores, etc.) in favor of more sustainable options such as composting and using waste food as animal feed.  The ban aims to reduce landfill waste and improve soil health by prohibiting businesses from throwing-away leftovers into landfills.  Vermont and Connecticut have similar legislation in place.  The future where we universally turn leftovers into soil amendment, may be just around the corner!