By Faith Miller
Operations Manager at Bootstrap Compost, Inc.
Welcome back to The BiG Stink and thanks for tuning in for Part 2 of the ins and outs of composting scat. Last time I covered the merits of composting cat, dog, rodent, and bird wastes but this week is all about your fellow man. So without further ado, let’s talk about composting human poo.
There are two reactions to composting human waste; either you think it’s gross or you think it’s awesome. For those of you on team gross, the ick-factor is warranted. Human feces may contain pathogens such as Hepatitis A, norovirus, E. coli, and roundworms to name a few. Also, food contaminated by night soil (untreated human waste) has led to major public health scares in places such as China, Southeast Asia, and Africa. Since poop can kill, a little fecophobia is justified.
Given that human feces is packed with pathogens and could be deadly, why would one want to compost it? Turns out excrement is chock-full of nutrients plants need including phosphates, potassium, and nitrogen which are the same ingredients in synthetic fertilizers. Americans are flushing 8 million pounds of poop a year, letting a major nutrient source go down the toilet.
There are in fact people collecting their waste and saving it from a watery grave. Dedicated composters are harnessing the power of their poop using specialty composting toilets or by simply collecting their waste in a bucket. Contents of the bucket are transferred to the compost pile and given a generous dose of sawdust to mask odors. After several months of curing, a humanure pile should test negative for coliform bacteria and be safe for use on edible crops. When the pile reaches high enough temperatures to kill off pathogens, it appears humanure can be perfectly safe.
That’s human waste composting at a small scale. What about large scale composting of poo? Mass quantities of human waste are composted in the form of biosolids. Biosolids are the organic materials resulting from the processing of sewage in a treatment facility. Biosolids are NOT sewage. Sewage is the untreated mush from everything we flush, throw down the kitchen sink, and wash down the bathroom shower. Biosolids are produced from a heavily regulated process overseen by the EPA and can be applied to crops. In fact, nearly 50% of biosolids produced in the U.S. are returned to farmland.
While a significant portion of human waste is being recovered for fertilizer, many people are concerned that the heavy metals, steroids, and pharmaceuticals found in human waste will make their way into soils and crops. However, regular testing has found that soils treated with biosolids have heavy metal concentrations significantly below the maximum permissible levels. When tested, biosolids are found to have the same concentrations of pharmaceuticals and steroids as water, soil and human bodies. Which begs the question- if these contaminants already are in the environment, does it matter if they’re in biosolids?
That’s the story on humanure. It may kill you or it may bless your garden. As long as the pile reaches high temperatures and is allowed to cure, pathogens shouldn’t be an issue for home composters (or they can invest in a $960.00 composting toilet). As for biosolids, they contain no more heavy metals or pharmaceuticals than the background environment. My take? Excrement is complicated and one should take it seriously. Tackle the turds at your own risk.