An essay on what we discard
A meditation on fertility, forgetfulness, and a very old idea whose time has quietly returned.
Not through carelessness. Through design. The flush toilet is one of the most elegant and least questioned machines of modern life. It enters the home with the authority of custom. You press a lever. The problem disappears. That is precisely the point — and precisely the problem.
What the body produces is not waste in any honest chemical sense. It is transformed matter — the residue of food that once grew from soil, carrying the minerals, nitrogen, and phosphorus that made it possible. What your body has finished with, the earth is not finished with at all.
He learned to pull nitrogen from the air and fix it into ammonia. Carl Bosch industrialized the process four years later. With that, humanity gained the ability to feed itself without returning anything to the soil.
Synthetic fertilizer delivers the molecules plants need. What it cannot deliver is organic matter: the living architecture of soil, the structure that holds water, the substrate that makes chemistry into biology. Every year, soils worldwide grow a little more mineral and a little less alive.
Meanwhile, every day, without ceremony, you produce roughly 150 grams and 1.5 litres of something that contains exactly those nutrients — and send it, diluted in six litres of clean drinking water, irretrievably into the sea.
Nutrients leave the field.
They travel to the city.
They are treated as a problem.
The same nutrients are then mined, synthesized, shipped back, and spread on the field again. Every year. At enormous cost in energy, in money, in atmospheric nitrogen.
Somewhere in that circuit is an absurdity so familiar we have stopped noticing it.
For most of human history, in most of the world, excreta were not a problem to be solved. They were a resource to be managed. In Edo-period Japan, cities had formal agreements with farmers. The contents of urban households were collected, transported, and paid for. The toilet was part of a transaction — and the transaction was part of a cycle.
The question is whether it is desirable — not merely as an ecological position, but as an aesthetic one. Whether the household that closes its own nutrient loops can do so with something that does not feel like a sacrifice.
That is the design problem. And it is, in the end, a more interesting problem than the engineering one. The engineering is largely solved. The culture — the sense that this belongs in a beautiful life — that part remains open.
Poudrette is a small attempt at that opening.
Continue reading
Two books explore what this essay only begins.
A clear-eyed look at the case for returning organic matter to the soil — and what stands in the way.
Every harvest removes nitrogen, phosphorus, and potassium from the soil. For millennia, what was taken was returned — through manure, composted food scraps, and human waste applied back to the land. The cycle was not romantic. It was structural.
Synthetic fertilizer broke that structural dependency — and for good reason. It allowed food production to scale beyond what local organic cycles could support. But it replaced a loop with a line.
A line is not a cycle. A line has an end. And at that end, something accumulates — in rivers, in coastal dead zones, in the slow degradation of topsoil — while somewhere else, something is depleted.
Nitrogen, phosphorus, potassium — these are the active molecules of plant nutrition. They are what conventional fertilizer delivers, and it delivers them efficiently. But soil is not merely a medium for delivering molecules to plants. It is a living system.
Organic matter — humus — is what gives that system structure, water retention, microbial diversity, and resilience. It is built slowly, from the decomposition of living things. It cannot be synthesized or shipped in a bag. It can only be grown, over time, in place.
Large-scale solutions to soil depletion require policy, infrastructure, and time. The household scale requires only a decision. One person, one year, one composting process: 350 to 450 litres of finished organic matter that did not become wastewater.
This is not a solution to industrial agriculture. It is not meant to be. It is a form of participation — local, direct, and legible. A household that understands its own material flows has already changed something, even before anything is composted.
The yètǔ is a composting toilet system designed around radical simplicity. No electricity. No chemicals. No compromise on aesthetics.
The yètǔ breaks into simple components. Each part can be repaired, replaced, or upgraded independently. Nothing is glued shut.
A robust 60-litre polypropylene bag receives all input. When full, it is sealed, moved to cure, and replaced. The toilet never stops. The process never pauses.
The structure is wood. Not because it is traditional, but because wood ages with dignity, can be worked by hand, and does not become landfill.
Four castors. The toilet moves to the compost site, not the other way around. Full bags travel on the same frame that holds them during use.
In classical Chinese, 夜土 (yètǔ) referred to human excreta collected at night for use as fertilizer — a practice that sustained Chinese agriculture for thousands of years. The name carries that history without hiding it.
Poudrette, too, is an old word — a French term for dried and powdered night soil, once sold commercially as fertilizer in 19th-century Europe. Two names from two continents, for the same old idea.
One explores the cultural and philosophical depth. The other builds the practical intelligence. Both are written for people who think carefully about how they live.
A journey through human civilisation seen through its most intimate and overlooked object. From ancient Rome to the Haber-Bosch process, from Edo-period Japan to the kitchen garden — this book makes the invisible visible.
A comprehensive guide to building, running, and understanding a composting toilet system — written with intellectual rigour and practical clarity. From biology to bag rotation, from troubleshooting to finished compost.
I grew up in Witzenhausen — a small town in central Germany known, if it is known at all, for its university of ecological agriculture. The word Kreislauf — cycle, circuit, closed loop — was in the air before I had a name for it.
I studied law, then left. I travelled — India twice, Athens, Toronto — working odd jobs, doing social work, finding out what I actually thought about things. I came back. I studied ecological agriculture and found myself, unexpectedly, back where I started.
Poudrette grew out of a simple observation: most composting toilet systems on the market are either too complex, too expensive, or aesthetically unkind. There is no reason the object that closes the nutrient loop should feel like a concession.
— Samuel Lennartz, founder
Poudrette does not exist to replace the flush toilet, condemn synthetic fertilizer, or tell anyone how to live. It exists to make one alternative more available, more beautiful, and more intelligible than it currently is.
The rest is up to whoever decides to try it.
Poudrette UG (haftungsbeschränkt)
Vertreten durch: Samuel Lennartz
E-Mail: poudrette@mailbox.org
Website: www.poudrette.org
Responsible for content according to § 55 Abs. 2 RStV: Samuel Lennartz
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Human excreta are not classified as biological waste under German law. Private composting for personal garden use is generally permissible but not formally regulated. Commercial use of compost derived from human excreta is subject to strict hygiene requirements. This website does not constitute legal advice.
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