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Ask the Conservationist

March 2012: Are Garbage Disposals Eco-Friendly?

You're standing at the kitchen sink cleaning the dinner dishes when eco-confusion strikes: what's the greenest way to dispose of your meat scraps and other non-compostable leftovers — in the trash or garbage disposal (if you have one)?

Grinding up leftover chicken bones in the garbage disposal means sending them down the drain to be handled by your wastewater treatment facility, which requires plenty of water and energy. But dropping them in the trash means decades of slow decomposition in a landfill.

Read the answer from one of the Conservancy’s green living experts below, and don’t forget to send us your questions on any conservation subject for one of the Conservancy's 550 staff scientists. (Note: We regret that we can only answer one or two questions each month and that we cannot answer the others offline.)

John Bauer, of Hinsdale, IL, writes:

For food scraps that I can't put into my compost pile — like chicken bones, fat, etc. — what is the greener way to dispose of them: put them in my waste going to the landfill, or grind them up in the disposal for handling by my waste water treatment facility? The former method means years — or decades — of slow decomposition in the landfill, but the latter uses water and energy by the municipality.

Jon Fisher, data management specialist and member of the Conservancy’s “green group”, replies:

This is a question I had myself recently! While it may seem counter-intuitive, the difference between the two options is much smaller than some other choices we make. So first let’s look at two of those bigger choices that are more important than what you do with your scraps: minimize food waste and eat lower on the food chain.

#1 Minimize Food Waste. The Food and Agriculture Organization (FAO) of the United Nations has reported that one third of global food production is wasted, and while some of that happens before it gets to us, industrialized nations still waste 222 million tons of food after we buy it.

Simply doing better food planning like knowing the recipes you’re going to make and in what order you’ll make them during the week helps to ensure that you buy only the food you will need and can use it before it spoils. If you tend to throw out leftovers, consider freezing them immediately, both to reduce spoilage and so that you can eat them in a few weeks when you’re not sick of that dish anymore.

And continue composting your food waste as much as you can. Keep in mind that it is also possible to compost bones and other meat with a little extra thought. If you live in the city you should probably invest in a sturdy pest-proof compost bin with a tightly fitting lid to keep the smell out. In suburban or rural areas just burying the animal waste well in the pile may be enough. Either way, try to avoid putting fatty parts of meat in the pile as these cause the most trouble.

#2 Eat Low on the Food Chain. Another change you can make that has an enormous impact is eating as low on the food chain as possible, as often as you can. Aside from having fewer bones to dispose of, you also will save massive amounts of water and energy. While figures vary wildly on the relative water and energy use of animal products vs. vegetable products, there is unanimous consensus that eating more vegetarian and vegan meals saves water (and reduces water pollution, air pollution, energy use, and much more).

It’s hard to find trustworthy figures (many groups have an agenda either for or against meat, independent of environmental impact) but the FAO’s “Livestock’s Long Shadow” and the Water Footprint Network’s (WFN) reports have really rigorous calculations. WFN comes up with beef requiring about 9 more gallons of water than soybeans as one example (634 gallons of water for a single hamburger). This is just a global average — in the U.S. our intense factory farms typically have a much higher impact.

I highly recommend anyone interested in greening their diet to check out "Just Food" by James McWilliams, as he critically evaluates all of his existing beliefs about green eating (organic, local, vegetarian, etc.) and comes up with some surprising results (including a great summary on grass-fed beef).

But even if the difference between the garbage disposal and the landfill is tiny relative to the impact you can have by wasting less food and eating less animal products, it’s still a question worth answering. Fats should definitely go in the garbage, as they can cause plumbing problems. For the rest, while it can vary significantly depending on where you live, in general the garbage is preferable.

Here’s why:
1) As you noted, it takes a lot of water just to wash your scraps down the drain, and takes even more water and energy to filter the scraps back out. This is especially critical if you live in a dry area or are having a drought.

2) In many municipalities, the solid waste removed from the water goes to the landfill anyway. In some areas it’s used as crop fertilizer or to generate energy.

If you want to be 100 percent sure of what to do, I recommend finding out whether your local landfill or water treatment plant captures methane to produce energy. If the landfill doesn’t, and the water treatment plant does, that makes the garbage disposal a more attractive option.

Either way, if you can cut down on how much food you waste and/or cut back on your consumption of animal products, you can probably cross the garbage disposal off your list of big issues to worry about.


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