“Can I compost my potentially E. coli-infected lettuce?”

This is romaine lettuce. Don’t eat it for a while. (Photo: Rainer Zenz via Wikipedia Creative Commons)

As you may have heard, romaine lettuce out of Arizona has been contaminated with a particularly nasty form of E. coli, E. coli O157:H7. So far, 53 cases have been identified across 16 states, including California, Pennsylvania, and Idaho. Those cases include 31 people sick enough to have been hospitalized, and five who have developed something called hemolytic uremic syndrome (HUS). HUS is a severe complication from E. coli infection, in which red blood cells get damaged and the kidneys fail. Even ICU docs are afraid of it.

The E. coli strain involved in this particular lettuce recall is so bad the CDC is taking no chances with it. Because it’s very hard for consumers to tell where their romaine is sourced from, the CDC is telling U.S. consumers nationwide to simply throw away all of their romaine unless they know for a fact it isn’t from Yuma, Arizona(You probably shouldn’t be eating salad at your favorite restaurants right now either, unless you know for a fact that their romaine isn’t from Yuma, Arizona.)

The warning covers all types of romaine lettuce:

  • whole romaine heads
  • hearts of romaine
  • any bagged salads containing romaine

To make matters worse, not all bags of mixed salad list romaine as an ingredient even if it’s in there. If you’re not sure whether or not the bag of salad in your hand contains romaine, the CDC says you should just throw it out and thoroughly sanitize your refrigerator after.

Guess who bought a week’s worth of salad in the hours before the warning was announced?

Hint: This is her cat.

(Photo: Shala Howell)

If we still lived in Chicago, this would be easy. I’d simply toss my lettuce in all of its merry little forms into the garbage bin as instructed.

But we live in California now, and that means we have curbside compost pickup.

Tossing a week’s worth of salad into the trash seems so wasteful. Which got me wondering: Wouldn’t it be better to compost it?

The 30-second answer (That’s “tl;dr” for all you youngsters out there) 

Probably not.

The 3-minute explanation for “Probably not”

I did a lot of reading about composting this morning.

Composting is sort of amazing when you think about it. It turns my spoiled food and rotting yard waste into rich and clean soil for next year’s crop. You know how you are supposed to cook food to specific temperatures and keep it there for a while to kill off the pathogens that cause food poisoning? That’s more or less what composting does.

According to a composting fact sheet I found from the Colorado State University Extension school, properly managed compost piles can achieve internal temperatures of 130-140ºF. A well-mixed compost pile that achieves 130-140ºF for two five-day spans will kill off most of the nasty pathogens hidden within it, especially if that lovely baking period is followed by 2-4 months of curing before you work the compost into your garden.

Unfortunately, the key word in that paragraph was “most.”

Composting does kill off most types of E. coli, but the strain involved in this particular outbreak is particularly resilient. As far as I can tell, E. coli O157:H7 appears to be the honey badger of food-borne illness (parents, don’t watch this video with your children).

It can survive in all sorts of conditions that kill other bacteria off. Freeze it, refrigerate it, dry it out. O157:H7 doesn’t care. It can adapt to acidic conditions and survive for extended periods of time in water and soil. In other words, once this guy shows up, he’s around for the long haul.

Cooking E. coli O157:H7 to 160ºF, though, is one of the ways to kill it.

From what I can tell, the composting process has to be executed absolutely perfectly in order to kill E. coli O157:H7, and even then composting only kills most of it. Most home composting operations can’t eradicate E. coli O157:H7 completely. They are simply too small, don’t get hot enough, and have too much temperature variability inside the pile. Don’t feel bad, home composters. A 2010 study showed that many commercial composting operations couldn’t totally eliminate E. coli O157:H7 either.

That’s a problem because it only takes a few O157:H7 cells to cause infection. Since the resulting illness can become very serious very quickly, especially for young children and the elderly, let’s do everyone a favor and keep our potentially E. coli O157:H7-infected lettuce out of our compost heaps.

Related Links: 

About Shala Howell

I spent two decades helping companies like Bell Labs, Juniper Networks, and a genetic testing company that was later acquired by CVS translate some of the world’s most complicated concepts into actionable, understandable English. Now I'm working on a much harder problem -- fostering children’s curiosity and engagement in the scientific, artistic, and linguistic world that surrounds them. The first book in my Caterpickles Parenting Series, What’s That, Mom?, focuses on how to use public art to nurture children’s curiosity in the world around them. My next book will focus on science, and how parents without a science degree can answer their curious child's questions without enrolling in a college level refresher course. In the meantime, you can find me blogging about life with a very curious Eleven-Year-Old at Caterpickles.com, chatting about books and the writing life at BostonWriters.blog, and tweeting about books, writing, science, & things that make me smile at @shalahowell.
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