Why You Should (Or Shouldn’t) Use Your Sink Garbage Disposal
By Alberto Castagnoli, Environmental Engineering ‘28
Filtration pods. Photo from Unsplash, Ivan Bandura.
Dinner is finished, you’ve washed the plates, and now a mess sits at the bottom of your sink. Your eye drifts to a button nearby –– to dispose, or not? A disposal is an installation under the sink that grinds food waste into small chunks to be sent further down the drain. Some say that garbage disposals are a great way to mitigate your carbon footprint, while others contend they are a serious problem for the wastewater industry. These devices have been around for almost a hundred years now, and the debate has been going on for just as long.
When you throw food scraps in the garbage, they are sent to a landfill where organic waste decays through anaerobic digestion. Landfills and wastewater plants rely on bacteria to break down organic waste and convert it into biogas, largely methane, and biosolids for fertilizer. However, it can be beneficial to reduce the amount of food waste sent to landfills and divert manageable amounts down the drain if local wastewater treatment plants have advanced biogas energy generation.
More than 1,200 treatment plants across the U.S. utilize anaerobic digestion to produce renewable energy from the sludge that comes through the plant. Although biogas generation is not exclusive to wastewater plants, they take up almost 50% of all biogas capture systems in the U.S. compared to 24% taken up by farms and 23% by landfills. King County’s South Plant has utilized this process since 1987 and has been selling renewable natural gas longer than any other plant in the country.
Biogas is used to generate heat and power for the plant as well as renewable energy to be used by the surrounding community. Photo by King County Waste Services.
The life cycle assessment of different food waste management systems in Sydney, Australia, reveals some important disadvantages to garbage disposal units. While they have lower overall energy usage and emissions than landfilling due largely to transportation, they release more nitrogen and phosphorus into local waterways, contributing to algal blooms. The garbage disposal uses almost fifty times more water on average than landfilling, which is a significant hit to the clean water supply. A city like Sydney that is situated on the driest inhabited continent runs into serious problems with such high water use despite its developed wastewater plants, comparable in function to those of King County.
The best way to decrease your emissions is to efficiently use the food you buy and avoid wasting food, but the next best option is to compost. The EPA estimates that of all food waste produced, about 60% of it is landfilled, and only 5% is composted. After those first two options, it depends on whether your sink leads to a biogas treatment facility and if you live in a city with a significant water supply. The convenience offered by a sink disposal is undeniable, but it comes with responsibilities towards your community and the environment at large, so next time you want to click that button, consider if that’s really the best option at your disposal.