I’ll never forget the look on my housemate Ruth’s face when she walked into our garden and found me crouched next to what she later described as “a suspicious wooden box” that definitely hadn’t been there the day before. It was 2012, I was halfway through my Environmental Science degree, and I’d just finished building my first humanure composting system. Poor Ruth thought I’d lost the plot completely. “Eliza,” she said slowly, backing away slightly, “please tell me that’s not what I think it is.” Well, it absolutely was what she thought it was, and thus began one of the most educational (and occasionally mortifying) experiments of my sustainable living journey.
Let’s be honest—there’s no delicate way to talk about human waste. We’re all trained from childhood to flush and forget, to believe that our bodily outputs are disgusting, dangerous, and best sent away through underground pipes to become someone else’s problem. God, we’re so disconnected from our own basic biology, aren’t we? But here’s the thing: our waste isn’t waste at all—it’s nutrient-rich organic matter that could be safely recycled back into soil if we just got over our cultural squeamishness and applied a bit of science. That’s what humanure composting is all about, and why I’ve spent nearly a decade experimenting with systems that would make most of my friends disown me if they knew the full extent of my “projects.”
So what exactly is humanure composting? It’s basically the controlled decomposition of human excreta (yeah, I said it) through thermophilic, or heat-generating, composting processes. When done properly—and this is the critical bit, so stick with me here—these systems harness the natural power of beneficial microorganisms to transform potentially pathogenic material into safe, nutrient-dense compost. The key word there is “properly.” This isn’t a chuck-it-and-hope situation. There’s actual science involved, and if you ignore it, you’re just making a pile of dangerous crap. Literally.
My first system was… well, let’s call it educational. I’d read Joe Jenkins’ “Humanure Handbook” cover to cover about seventeen times and was convinced I had all the theoretical knowledge needed. I built a basic two-chamber wooden composting toilet with a urine diverter (separating liquid and solid waste makes the whole process easier to manage and significantly less smelly) and a collection system using sawdust as cover material. The idea is simple: do your business, cover it completely with carbon-rich material like sawdust or wood chips, and let it compost for at least a year after the chamber is full.
What the handbook didn’t prepare me for was explaining this setup to visitors. My parents dropped by unexpectedly that summer, and Dad—bless him—actually seemed impressed by the engineering while Mum just stood there with an expression I can only describe as “pained resignation.” She finally said, “Darling, is this… strictly legal?” Which, fair question.
And that brings me to one of the most important aspects of humanure systems that enthusiasts often gloss over—the legal and regulatory considerations. In the UK, the Environment Agency doesn’t explicitly prohibit composting toilets, but there are regulations around the disposal of the resulting compost. The legal landscape is patchy and often confusing. Some local authorities are more accommodating than others, and rural areas typically have more flexibility than urban ones. In some countries, like Sweden and Finland, composting toilets are actually encouraged in certain contexts, while in others, you might as well be proposing to build a nuclear reactor in your garden.
I soon discovered that my university rental agreement definitely did not allow for “alternative waste management systems” (I checked after Ruth’s initial horror). So I reluctantly dismantled my first attempt and chalked it up as theoretical research. But I didn’t give up—I just got sneakier and more scientific about it.
A few years later, when I was working at EcoLogical magazine, I convinced the editor to let me write a lengthy feature on “closed-loop systems” which gave me the perfect excuse to visit several established humanure composting sites across the country. One was at a permaculture education center in Wales where they’d been successfully composting human waste for over 15 years with zero health incidents. Their system was beautiful in its simplicity and effectiveness—multiple composting chambers on a rotation schedule that allowed each batch to fully process for two years before being used on non-food plants.
The manager there, a wonderful woman named Fiona with wild grey hair and soil-stained hands, showed me their temperature monitoring system. “The magic happens between 55 and 65 degrees Celsius,” she explained, showing me the logbooks where they tracked the core temperature of each compost pile. “Maintain that for at least a week, and you’ve killed off the pathogens. But we give it two years just to be certain.”
And that’s the key scientific parameter that makes humanure composting safe: temperature. Thermophilic composting relies on the heat generated by microbial activity to kill potential pathogens. Research has shown that maintaining temperatures above 55°C (131°F) for at least three consecutive days will destroy most harmful organisms, including the ones that keep health officials up at night. But most well-run systems aim for higher temperatures maintained for longer periods, with regular turning to ensure all material reaches these pathogen-killing temperatures.
After my visit to Wales, I became slightly obsessed with the science of thermal composting. I bought a set of compost thermometers and started experimenting with different carbon-to-nitrogen ratios in my regular garden compost to see how hot I could get the piles. My housemates at the time thought I was mad, standing out in the rain with a thermometer, grinning like a lunatic because my pile had hit 60°C. “It’s alive!” I’d shout, and they’d just roll their eyes and close the curtains.
The carbon-to-nitrogen ratio is another crucial factor in effective humanure composting. Human excreta has a high nitrogen content, which needs to be balanced with carbon-rich materials like sawdust, straw, or dried leaves. The ideal C:N ratio is around 25-30:1 for optimal decomposition. Too little carbon and you’ll end up with a smelly, anaerobic mess that attracts flies and doesn’t heat up properly. Too much carbon and decomposition slows to a crawl. Getting this balance right is part science, part art, and takes some practice.
When I finally bought my own place—a tiny cottage with an actual garden in Bristol—one of the first things I did was set up a proper three-bin humanure system in a discreet corner behind the shed. I used reclaimed pallets, lined them with heavy-duty plastic, and built a proper cover to keep out rain. This time, I did everything by the book, monitoring temperatures religiously, keeping detailed logs, and waiting a full two years before using any of the finished compost.
The results were honestly incredible. The rich, dark, earthy-smelling humus that emerged from the final chamber after two years bore no resemblance whatsoever to its origins. Laboratory testing (yes, I actually sent samples to be tested—I told you I was thorough) confirmed it was free from pathogens and rich in nutrients. The flowering shrubs I planted with this compost practically exploded with growth and blooms. My neighbors kept asking what my secret fertilizer was, and I’d just smile mysteriously and change the subject. Some truths are better left unshared over garden fences.
Of course, there are legitimate concerns about humanure composting that can’t be dismissed. If not managed properly, there are real risks of pathogen transmission. And certain medications and substances that pass through our bodies can potentially contaminate the compost. These are valid concerns that require respect and proper management strategies, not dismissal.
Safety protocols for any humanure system should include:
Strict temperature monitoring and recording
Proper containment to prevent leaching into groundwater
Clear separation from water sources (at least 30 meters)
Use of the finished compost on non-food plants initially
Hand washing stations and hygiene protocols
Adequate aging of the compost (minimum one year, preferably two)
Regular turning to ensure all material reaches pathogen-killing temperatures
When I started writing for Zero Emission Living, I pitched an article on humanure composting and watched my editor’s face go through about seven different expressions before landing on “reluctant interest.” The resulting piece generated more emails than anything else I’d written—half of them enthusiastic, half horrified, and all of them passionate. One reader wrote a six-page letter detailing his 20-year humanure system and sent actual photos of his setup, which was both heartwarming and slightly alarming.
Look, I’m not suggesting everyone should start composting their bodily waste tomorrow. For most people living in urban areas with functioning sewage systems, it’s not practical or necessarily the most sustainable option right now. But our current water-based sewage systems are enormously resource-intensive and fundamentally flawed in their design. They use drinking-quality water to transport waste, require massive infrastructure, and often struggle to safely process pharmaceuticals and other contaminants.
The future of sustainable waste management will likely involve multiple approaches, including advanced composting systems, biogas digesters, and technologies we haven’t even developed yet. What’s important is that we start challenging our culturally-ingrained disgust and begin seeing our waste as the resource it actually is.
My own humanure journey continues to evolve. These days, my system is more sophisticated, with better temperature monitoring, a more effective urine diversion design, and a proper three-year composting rotation. I’ve given talks at several permaculture conferences (where, thankfully, people don’t gasp in horror at the topic), consulted on designs for off-grid properties, and even helped a community garden set up a communal composting toilet that’s been successfully operating for four years now.
The best moment, though, was when my mum visited last summer and admired the massive hydrangeas growing by my garden gate. “They’re absolutely magnificent, darling,” she said. “What’s your secret?” I just smiled and said, “Closed-loop nutrients, Mum.” She narrowed her eyes suspiciously, then laughed and said, “I don’t want to know, do I?” Probably not, Mum. Probably not.
