“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)

Update November 26, 2018: This post was originally written in response to the multi-state outbreak of e.coli contamination in romaine lettuce that occurred in April 2018. That particular outbreak was sourced to lettuce out of Arizona. Another multi-state recall of romaine lettuce due to E. coli contamination has recently been announced, prompting a resurgence of interest in this post. At the time of this update, the CDC had not yet identified a single source for the contamination. The type of contamination is the same, however, E. coli O157:H7, so the advice about composting remains valid. TL;DR: Don’t compost your E. coli-infected lettuce.  

As you may have heard, romaine lettuce has been contaminated with a particularly nasty form of E. coli, E. coli O157:H7. So far in the November 2018 outbreak, 32 people in 11 states have been infected. Those cases include 13 people sick enough to have been hospitalized, and one patient who 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(You probably shouldn’t be eating salad at your favorite restaurants right now either.)

The warning covers all types of romaine lettuce:

  • whole romaine heads
  • hearts of romaine
  • any bagged salads containing romaine, including baby romaine, spring mix, and Caesar salad

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.

Update for the November 2018 outbreak: I made some edits to the previous paragraphs to clarify that the CDC is recommending that people who have any type of romaine lettuce in their home should not eat it and just throw it away, regardless of its point of origin. In the April 2018 outbreak, we were simply told to avoid romaine from Yuma, Arizona. This time around, we need to avoid all of it.

The sickness stats in the previous paragraphs have been updated for the November 2018 outbreak as well.

In case you were wondering, by the time the CDC declared the April 2018 e.coli outbreak to be over on June 28, 2018, 210 people in 36 states had been infected, 96 people hospitalized, and 27 people had developed HUS. Five people died in Arkansas, California, Minnesota (2), and New York.

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.

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