In my Poop book, I have a section about animal rendering, an age-old process used to dispose of dead animals. It’s been going on since the time of the ancient Egyptians. Although extremely gross to think about, disposing of millions of pounds of dead animals (including parts of animals discarded by slaughterhouses) is a vital service. In the nineteenth century, renderers were known as knackers. Back then, it could be a real problem for city traffic if a horse or donkey keeled over and died in the street. In poor neighborhoods, the carcass was often left to rot. In better neighborhoods, renderers were called.
Although still a thriving industry, you don’t hear about rendering much nowadays, because it’s a deeply uncomfortable subject, especially if you’re a pet owner. Or a vegetarian. Or a Muslim. Or a Hindu. Or an observant Catholic. Or you keep Kosher. It’s safe to say it makes everyone uncomfortable.
As described in this article in the New York Times, rendering is “the ancient but seldom-discussed practice of boiling down and making feed meal and other products out of slaughterhouse and restaurant scraps, dead farm animals, road kill and—distasteful as it may seem—cats and dogs euthanized in some animal shelters.”
My editor actually asked me (twice) to rewrite the rendering section to make it less skeevy. If this post is freaking you out, you might want to stop reading.
Still here? All right then, let’s talk about gelatin (or gelatine). Gelatin is used in a bajillion products. What is it, exactly? You can actually read about it on the Gelita website (formerly known as Knox Gelatine). According to the company’s site, “The raw materials used in the manufacture of gelatine are the skins of pigs and cows or demineralized bones from animals that have been slaughtered but approved for human consumption by the veterinary authorities.”
If you’ve ever made home-made turkey stock with the carcass from your Thanksgiving turkey and wondered why your “broth” looked all jiggly and gross the next day when you pulled it from the fridge—well, that’s why. It’s the collagen in the bones. “A natural foodstuff,” the website proudly proclaims. “A tasty, natural adhesive.”
During wartime, rendering plants even processed fat from households for manufacturing ammunition.
What products are made from gelatine? Get comfy. As described in a weird, dubbed-from-the-German video embedded on the Gelita website, they include marshmallows, gummy bears, licorice, whipped yogurts, and store-bought chocolate mousse.
There’s also gelatin and/or animal-based lubricants in many candy bars with “nougat” filling, caramel candy, chewy breath mints, sports drinks, butter, ice cream, medicines with gel caps, lipstick, wax, crayons, soaps, candles, and homeopathic medicines. And pet food.
I know. Ew.

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YUCKY!
Mmm…yep. It is no accident that on the North Shore of Massachusetts there were once leather tanneries and shoe factories, as well as Kraft Foods Atlantic Gelatin plant.
Wow–I didn’t know about the tanneries etc there. Talk about smelly. Yeesh.