Composting human wastes

Imagine a country in the developing world. Fertilizer is both expensive and scarce. The few farmers that can afford it, buy up the whole supply and then dump twice the adequate amount, so half of it runs off into the river. Meanwhile, the rest of the alternatives are owned by the utility company and held in giant tanks of water, where their main accomplishment is producing tons of methane.

That’s not too different from what we do in most of the US. Our current system requires a huge input of energy to fuel the Haber-Bosch process, whereby we acquire nearly all of the supplemental nitrogen our crops need. Meanwhile, we literally flush nitrogen down the drain in the form of both “humanure” and manure from hogs and cattle. Both are kept in holding tanks of water and treated as a problem.

Yes, there are a LOT of reasons that raw sludge can be a problem. For example heavy metals and E Coli. are a big reason to keep the public safely away from this material. Also, the powerful smells produced during waste treatment are a powerful deterrent in themselves.  However, with proper testing for temperatures and safety guidelines, these wastes can be composted into a safe and valuable product. The manure that we throw away is a major reserve of nutrients that we should consider tapping into.

While working in Athens, GA this summer I got to meet some of the great people that help run the county’s municipal waste composting program. They processed about 1/3 of the Athens-Clarke County’s solid municipal waste. The biggest reason they couldn’t take on more material was that they can’t get enough carbonaceous materials to keep up with the supply of nitrogen. By their estimate, three similar programs exist in the nation. Why aren’t there more of these programs?

Based on the tests he had seen, the facility manager told me the finished product is surprisingly low in potential heavy metals, coming in well below EPA guidelines for every regulated heavy metal. His managers did not allow him to share copies of these tests for fear that people might deem the compost *gasp* safe to use on food crops. Against every recommendation, we used the final product to grow food at Spring Valley Ecofarms, the farm where I acted as TA for a course in Organic Agriculture.

The composting facility itself was pretty cool. Huge tractors with weird belly-mounted mixers would mix the compost. The manager would check temperatures on certain piles. A big machine screened out the coarsest and finest materials from the finished product. We even saw “fresh” dewatered sludge, which still smelled a few orders of magnitude better than a wet-processing facility. Walking around the facility we’d sometimes get a whiff of something sour, but all in all, I think the whole class and I were pretty impressed!

The program is not widely publicized and it’s pretty hard to find any literature in clear language about how cool/important this program is. Here’s a link to one of the few resources I could find about the program:
Commercial Composting

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