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  • If you have a composting service at work or school, you might have noticed an odd pattern.

  • They can take as many apple cores and paper towels as you care to give them

  • but they will not accept meat or dairy.

  • And if you compost at home, you might avoid adding these things to your pile.

  • But the problem isn't that it's hard to break these things down.

  • The problem is that it's easytoo easy.

  • Composting is a way to convert things like food scraps and yard trimmings into fertilizer,

  • instead of sending those things to landfills.

  • So it might seem annoying that you can't toss all your leftovers in.

  • And it turns out you canif you're careful.

  • Some of the problems with composting meat are practical.

  • It can attract pests, and you probably don't want to have to fight off a bunch of rats and raccoons in your own backyard.

  • Plus, some folks worry about disease-causing bacteria being able to grow in home compost piles.

  • But the solution there is just to make sure the pile reaches a high enough temperature to kill those pathogens off.

  • Temperature is a super important factor in composting anyhowone any home composter should be keeping an eye on.

  • But the weirdest reason it's tough to compost meat and dairy is how delicious soil microbes find animal protein.

  • And even though composting is all about getting friendly soil organisms to break stuff down for us, we don't want them to get too excited.

  • Good composting relies on the ratio of two elements: carbon and nitrogen.

  • Carbon makes up the chemical foundation for practically all of life's favorite molecules, including proteins.

  • But proteins also contain a lot of nitrogen.

  • This means that animal products, which are more densely packed with proteins than veggies, contain more nitrogen.

  • Experts have determined that the best ratio of carbon to nitrogen in compost is somewhere between twenty and thirty to one.

  • Veggie scraps are generally in that sweet spot at twenty-five to one,

  • but something like a chicken carcass is more like five to one.

  • And when bacteria see all that nutritious nitrogen in a compost pile, they go a little bonkers.

  • They start to grow really fast.

  • That uses up oxygen, and when the bacteria use up all the oxygen in the pile,

  • that favors the growth of other bacteria that don't need oxygen to live.

  • Basically, the pile switches to anaerobic, or oxygen-free, decomposition.

  • And the chemical products of this process are very smelly.

  • Like hydrogen sulfide, which smells like rotten eggs.

  • So if you just casually toss your meat and cheese into your compost pile,

  • you'll probably end up with a slimy, putrefied mess instead of lovely fertilizer.

  • And putrefied compost can actually contain chemicals that are toxic to plants

  • though you might be able to salvage it if you dry it out and try again.

  • To avoid taking those extra steps, expert composters might add extra wood chips or paper products to the pile,

  • since they have a lot of lignin — a tough component of plant cell walls

  • which doesn't contain any nitrogen at all.

  • Bacteria can still eat lignin-packed materialsso they just slow down those overly- enthusiastic microbes.

  • And if you really want to compost meat at home, you could plan ahead.

  • One way is to use a method known as bokashi, which relies on anaerobic processes on purpose.

  • Basically, you add cultures of friendly anaerobic bacteria instead of bad, smelly ones.

  • Once things like meat scraps have been treated with the bokashi method,

  • they can be added to a compost pile with less risk of the whole thing going stinky.

  • So just because your municipal compost service won't take meat,

  • that doesn't mean it can't be compostedyou just have to know how to rein in your bacterial buddies.

  • Thanks for asking, and thanks to our patrons for helping us bring you these answers.

  • You guys are the best.

  • If you want to learn more about joining our amazing community of supporters, you can head

  • over to patreon.com/scishow.

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B2 中高級

為什麼不能堆肥肉? (Why Can't You Compost Meat?)

  • 6 2
    林宜悉 發佈於 2021 年 01 月 14 日
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