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Urine Composting

by Ted Sterling

I was surprised to learn, years ago, that the synthetic fertilizers integral to conventional agriculture are derived in large part from natural gas. This is but one component of an agricultural system that is estimated to consume 10 calories of energy for every one it produces. Every step of the way, contemporary commercial agricultural practices rely on petrochemicals or petro-powered tractors, trucks, and other machinery employed in the process of growing commodities. The products of this process travel the globe to satiate market demands, contributing further to the tally of energy consumed to bring a cup of beans or grain to the table anywhere in the world. The land this agriculture employs ends up impoverished in numerous ways or washed away; the ecology of the planet suffers as a whole because the system focuses on extraction without paying the true costs. If peak oil is a concept that stands up as years advance, then presumably we can also expect a significant crisis in the fundamental viability of commercial agriculture both here and abroad.

One of the trends of necessity I expect we'll see as such changes progress is a focus on diversifying agriculture locally. Where now most farmers grow one or two commodities, increased regional self-reliance will make other crops more valuable as local demand for them goes up.

Across huge swaths of territory, notably the Midwest, almost all the agricultural land is seeded in commodities like corn and soybeans. Other locales may be better suited to different crops, but the pattern remains: in large-scale commercial agriculture, specialization and monocropping remain the norm. Local and regional self-reliance are simply not goals of modern agriculture.

When we can no longer support this energetically-expensive agriculture, and we look at all the ways we need to make agriculture more sustainable, soil fertility strategies must also shift. No readily available source of fertility can be ignored. One most people might prefer not to consider is human waste, but people are part of the web of energy that constitutes ecosystems. In nature nothing is wasted, all is recycled in a continuous cycle. If we wish to sustain ourselves and the land we live on, then our waste is a valuable resource for sustaining the soil that grows our food; from whence it came, so it must go.

Dancing Rabbit has used the humanure system for many years. Basically, we compost the poo we produce in large piles of a size that promotes efficient and safe decomposition. Our system is not perfect, though. Sawdust, used to cover each contribution in a humey bucket, and straw, incorporated to cover layers of humanure as each pile is built, both contribute high levels of carbon. One of the fundamentals of composting is creating a good balance of carbon and nitrogen to achieve thorough breakdown of all components. Our system tends to produce compost that after two years is still full of uncomposted wood particles, though the human waste component is entirely gone. One way to alter that balance is to add more urine, which is full of nitrogenous compounds. Higher quantities of urine add some challenges to a system based on five-gallon buckets, however. More urine creates more odor, and it also adds weight, neither of which are desirable. Most folks at DR pee outside for this reason, as well as for convenience, since most of us spend a lot of time outdoors or walking from one building to another repeatedly throughout the day.

Yet 80% of the nutrients that leave our body in waste products are found in our urine. Dancing Rabbit will certainly benefit from much more agriculture on site, particularly the farming of staple foods like the beans and grains we eat so much of, and that will require increased soil fertility. We are producing lots of fertilizer content ourselves; we just need to harness it more effectively.


Space-efficient urine composter in use

Sara and I have employed a urine composting system since shortly after we moved here in 2003. While we still lived in a tent, we set up a system like one I learned of from my friend Terrance in northern Washington. It consists of four stacked buckets. The top three are filled with partially composted material, and each has numerous holes drilled in the bottom to allow liquid to progress to the bucket below. The lowest bucket serves as a receptacle, and has a spigot at the bottom to allow one to draw off the composted urine tea the system produces. We've found the mature humanure compost, still full of that carbon-heavy wood material, to be a perfect material for the upper buckets, sometimes with some straw or other woody material mixed in. It provides an ideal medium for the growth of various bacteria that break down the rich organic compounds in our urine. We change out the material in the buckets two or three times a year, adding the spent compost to our garden compost pile as a great bioactivator.

Our tiny house has no bathroom, and the tight spiral stair is enough of a hurdle in the dark that we're quite happy to forgo the trip outside in lieu of using the composter, particularly in winter. Its presence in our loft consists of a small funnel that hangs on a hook in our window sill; the tubing attached to it, which goes down through the wall to the composter in the greenhouse below; and a jug of water typically stocked by our rain barrels, used for washing down each addition.

Our funnel doesn't smell unless the bucket needs to be changed. Every two weeks or so we empty the reservoir, either into the greenhouse beds or into a jug for transporting to the garden bed or tree favored for the fertilizer boost. The compost tea has a dark color and almost no odor. The water added to the system keeps it dilute enough for direct watering. Plants love it. If it still sounds a little gross, consider that in healthy populations, urine is typically sterile as it exits the body.

This compost tea is not your super-amped commercial fertilizer, but fertilizer nonetheless, which is steady in supply, hyper-local, and essentially free. It does not provide organic matter to the soil, and so is no substitute for standard compost or manure, but can form an important part of your soil fertility practices. In some places, notably Scandinavia, this is done on a municipal scale. To employ this here, we'd need to alter our toilet systems to provide for efficient collection. Urine-diverting toilets are manufactured in a handful of countries, but such a system is not too challenging to craft at home. I expect to install such a system when we build a moldering privy in the next few years.

For more information, track down a copy of Liquid Gold- The Lore and Logic of Using Urine to Grow Plants, by Carol Steinfeld, or The Humanure Handbook, by Joseph Jenkins (also available for free download at http://www.jenkinspublishing.com/humanure.html).

March Hare Summer/Fall 2008 Issue 57
The Road Home It’s a Foundation!
Low-Tech Solutions Urine Composting
The Life of Brian Representing Water
Popcorn, My Love