Tech & Science
National Geographic Emerging Explorer T.H. Culhane talks about harnessing the power of poo.
Break down your take on trash and poop.
In the field of industrial ecology, the mantra is that, in nature, there is no waste. And we are a part of nature. Everything we produce is a material. We produce energy and matter and it comes back around and is transformed into something else. My insight is that we are almost self-contained biospheres. We’re pulling materials into our nests and then we’re excreting—if you like—urine, fecal matter, sweat, lemon peels and banana peels and avocado pits and onion skins and the food that we didn’t eat that was still on our plate. My study is harvesting this stuff that other people have ignored.
What is biogas and what’s so great about it?
Biogas [fuels like methane produced by the breakdown of organic matter] is the most ancient simple hydrocarbon. It’s what dominated the Earth’s atmosphere when this planet began. There’s methane everywhere in the universe, but Earth was almost completely dominated by methane until microbes began to produce oxygen. At that time, the methane-producing organisms went into hiding because they can’t stand oxygen—it’s a poison to them. So they went down into ocean sediments and deep into rock and that’s why we have so much natural gas; they’re still there, churning, making the stuff. And we have them living in our guts, in our intestines, in our stomachs, and so does every multicellular life form.
How’d you start with methane?
I started a biodigestor in my bathroom using my baby’s diaper waste. I knew there were all these organisms in that material the baby was creating. I’d take the food waste the baby didn’t eat, and I’d put those in the biodigestor and the organisms would eat the food waste and then fart out methane. I had this stomach I created out of plastic in the bathroom, and it farts and it also pees out this liquid fertilizer. You can burn it on a stove and you can run electric generators off of it so you can run lights, gas lamps, refrigerators—it’s true natural gas. And then eventually you have a sludge that builds up that you can dry and it’s soil. Three byproducts—methane, fertilizer and soil—that are fantastically useful and you don’t have to worry about waste treatment.
How does all this translate into turning on lights and ovens?
You store the methane in a balloon or a plastic bag, and we use a hose to deliver it. In India, we used garden hoses, and, here in the U.S., we go to Home Depot and get the clear plastic hoses people use in their aquariums. If we want to create pressure, we get biogas pumps from China, which have an inlet and an outlet so you can plug a tube in one side and then it pumps it out the other. You can turn any stove into a biogas stove.
Would this work for people who want to live off the energy grid?
If you’ve got a kitchen and a toilet, you’ve got all the makings of a biogas system. A family of four to six produces enough waste, both toilet and food—you can keep them separate or you can combine them—to cook for about two hours a day or run a generator for about 45 minutes a day, which you can use to charge batteries to run lights for many, many hours. And that’s just on the waste they produce. Now if they went out and hunted and gathered great sources of biogas that are just piling up to rot—grass clippings, fruit fall, animal waste—they begin to get to the point where they can probably heat water for bathing as well and generate emergency backup electricity. Could a prepper live 100 percent off-grid? Yes.
What about places that are snow-covered?
You can put a big tarp over a permafrost lake and it bubbles constantly and you capture that gas and you use it—they’re starting to do that in some parts of Scandinavia. The microbes are there. It’s all been a question of how much organic material is available at any given time, and, at most cold temperatures, the microbes are producing gas very slowly.
What can we do to maximize our daily energy output?
I’ve said that InSinkErator garbage disposals are the most important technological achievement of the 21st century because you grind up the food waste and then you can turn it into soil in three to six days instead of composting it for three to six months, or you can turn it into biogas in 24 hours. And no rats, raccoons, dogs, cats or other animals have interest in it after it’s been ground up. It all belongs to the microbes.
Can you mess up the recipe?
Yeah. It’s a stomach and people tend to overfeed it and then it goes sour and won’t produce methane anymore and starts to produce carbon dioxide. Then you have a couple of options: 1) stop feeding it and wait until it recovers, which will take several weeks; 2) dump in sodium bicarbonate or antacid and wait for it to start again; 3) drain it and refill it with more manure or lake mud to get it started again. If you have a system that has toilet waste going in all the time, or animal waste of any kind, you almost never have to do anything, but many communities don’t want to do that because of psychological taboos.
Can you store it?
It’s natural gas. It can be stored for millions of years. It’ll be as good as the day you produced it.
This article appears in the latest Newsweek Special Issue, "Off Grid: Exploring the End of Life as We Know It," by Executive Editor Jeff Ashworth of Topix Media Lab.