Is It Safe To Use Compost Made From Treated Human Waste?
May 12, 2013
“For thousands of years, before the invention of synthetic fertilizer in 1913, many farmers utilized their decomposed sewage, sometimes called "night soil," to replenish the soil with nutrients lost in farming. The Chinese were especially adept at using human waste this way – one historical account notes that in 1908, a contractor paid the city of Shanghai $31,000 in gold for the privilege of collecting 78,000 tons of human waste and carting it off to spread on fields.
When growing urban areas required that sewage be piped outside of the city, the practice dropped off and attention turned to improving wastewater treatment to avoid polluting waterways. Raw waste is, of course, nasty stuff until all the dangerous bacteria have been killed off, either by heat or anaerobic digestion.
But the sludge was still piling up in landfills, so scientists began testing how to use it in agriculture safely; the waste was a free source of nutrients like nitrogen and phosphorus, afterall. And letting it sit in landfills or incinerating it created its own environmental issues. By the 1990s, the Environmental Protection Agency created strict standards with two tiers for biosolids still in use today. To sell Class A biosolids to farmers and gardeners, facilities have to ensure that there are no dangerous heavy metals or bacteria in the end product.”