The Story Behind the Sink Garbage Disposal

Guest post from Belinda Bankes Frykman  

While updating our kitchen and installing a new sink, my husband and I considered whether or not to add a sink garbage disposal, or “food waste disposer.” We didn’t currently have one and I didn’t see the need, since I compost food. Prior to marrying me, my husband had always had a sink disposal and doesn’t think twice about rinsing food down the sink. We have different perspectives, experience and knowledge. So began my search for the true, un-biased story behind sink garbage disposals.

What actually happens to food scraps after being ground up and rinsed down the sink?

Science’s Stance

The strongest argument for using sink garbage disposals is based on anaerobic digestion. A blog post written by Science 2.0 on August 12, 2011, commissioned by InSinkErator, found that “food scraps processed through a wastewater treatment plant with anaerobic digestion and co-generation can result in a reduction of global warming potential. It also concludes that processing of food scraps at these advanced wastewater treatment facilities has lower energy demand—less than landfills, incineration and centralized composting.” The challenge with this argument is that the majority of wastewater treatment plants do not use anaerobic digestion or co-generation. Most of them, including the Metropolitan Sewer District of Greater Cincinnati, filter out solids, incinerate or dry them out and then and send the residue to the landfill.

According to a March 13, 2013 post in the Good on-line magazine, “If, and this is a big if, the plant where your wastewater is treated converts waste into biogas, then your banana peels and potato skins will be used to create renewable energy and fertilizer products. If not, the solids are typically hauled away to a landfill or burned.”

Wastewater plants that convert to biogas are not common enough to create a strong argument for using a sink disposal as a viable source for renewable energy.

The Landfill and Food Waste

Although sending our food scraps to the landfill isn’t an ideal solution for lots of reasons, one of big concern is the generation of greenhouse gases. Decomposition of organic matter in a landfill happens slowly (it is mostly an anaerobic process because of how modern landfills are constructed). But decomposition does happen and methane is generated and emitted.

There are ways, however, to minimize these gas emissions. The Rumpke Sanitary Landfill here in Hamilton County, “recovers methane gas and use it as natural gas energy” including “more than 200 gas wells that recover enough natural gas energy for up to 25,000 homes in the Cincinnati area.” In addition, Rumpke installed “10 compressed natural gas (CNG) refuse collection trucks, and construction of a slow-fill, compressed natural gas fueling station and 16 fueling stands. The switch to these trucks not only offers another use for landfill gas, but also offers a 21-26 percent reduction in green house gases.” Therefore, if you cannot compost and you’re deciding between tossing food scraps into the garbage or washing them down the drain, it is less detrimental to send food scraps straight to the landfill on a garbage truck rather than divert them through a wastewater treatment plant before burying them in a landfill.

A Plumber’s Perspective

I found Roto-Rooter’s take on sink garbage disposals worth noting: “Many of Roto-Rooter's plumbing service calls involve garbage disposals. They may be one of the most misused appliances in any home. Few people realize that garbage disposals are only designed to handle light food residue that is rinsed from plates and cooking utensils before they go into the dishwasher.” So sink garbage disposals are not even intended to grind up leftover food. They’re just a bulky appliance that basically replaces the task of tapping bits of residue from a sink strainer into a compost bucket or garbage can.

My Final Decision…

Ultimately, the decision to install a sink garbage disposal came down to whether or not I am comfortable sending food through the wastewater treatment plant and then to the landfill. I considered the convenience of rinsing food residue down the sink. It seemed like an unnecessary expense and poor use of space, when all I have to do is simply tap the sink strainer into my compost pail (or garbage can, depending on what is in the strainer—no fats, dairy or meats go in the compost bin).

So, did we install a sink garbage disposal? Nope, my husband and I continue to use the “tap the strainer method” of removing residue from the sink. I am the “food waste disposer” in our house! I do believe the best option for disposing of food scraps is composting. It takes very little effort to compost and I like seeing the progress in my bin. It’s pretty cool watching nature take care of us.

Of course, this is a compost blog—I presume we all agree the best use for food scraps is to turn them into a nutritious soil additive through composting. If you don’t have room in your yard for a compost pile or bin, or you live in an apartment or condo, a worm bin can do the trick. If neither of these options is viable for you, make an effort to keep food waste to a minimum since all those food scraps are landfill-bound—whether you throw them in your garbage can or grind and wash them down the sink.