The World’s Farms Are Hooked on Phosphorus | Hacker News Reader

The World’s Farms Are Hooked on Phosphorus

wired.com

11 pointsWithinReason5 comments

We need to close the nutrient loop by returning animal and human manure back to the soils that fed them. It's not hard, just expensive. As Phosphorus becomes more expensive due to scarcity, our incentive to recycle it from animal and human excreta will grow until it reaches a tipping point where recycling all human and animal waste starts to become the more economical choice.

Relevant HN discussion from last month:

https://news.ycombinator.com/item?id=34182343

When it comes to recapturing phosphates from waste streams, Milwaukee provides an example to follow:

https://en.wikipedia.org/wiki/Milorganite

It seems like it has a bit of a PR problem, though? See "environmental concerns" in that article and also [1].

I don't know how bad the problem with contaminants is, but it seems like this kind of recycling is going to face a lot of skepticism from environmentalists?

[1] https://www.publishersweekly.com/9781567510607

Yes, biosolid fertilizers have a PR problem. Some of the bad press is deserved. Depending on how septic sludge is treated, the resulting product can still release nasty smalls, contain harmful compounds like PFAS and birth control hormones, host residual human pathogens, and accumulate heavy metals that wind up back in the food chain. People who live near farms where treated sludge is used as fertilizer sometimes report bad odors and health problems. For example, the city of Los Angeles spreads treated sludge on city-owned farms near Bakersfield, California. Local residents have complained about the smell and potential health hazards, filing lawsuits against the city of L.A.:

https://www.bakersfield.com/news/we-fought-this-as-best-we-c...

Fortunately, these problems are surmountable. Most large U.S. cities treat their sludge with methods that result in the above listed downsides. Newer, safer, and more efficient processes have been developed to mitigate or eliminate these pitfalls. Thermal hydrolysis in particular can eliminate practically all organic contaminants, improve the nutritional quality of the final product, and increase anaerobic sludge digester throughput. With thermal hydrolysis, solid waste is essentially boiled in an autoclave at high temperature and pressure and then rapidly decompressed. This process thermally decomposes PFAS "forever chemicals" and organic contaminants like birth control hormones:

https://en.wikipedia.org/wiki/Thermal_hydrolysis

https://www.cambi.com/what-we-do/thermal-hydrolysis/how-does...

Thermal hydrolysis is a relatively new process for waste management, just now starting to see wider adoption. As of 2015 the Washington, D.C. water treatment plant uses thermal hydrolysis to treat a large subset of that city's solid waste, producing 200,000 tons of biosolid fertilizer each year:

https://en.wikipedia.org/wiki/Blue_Plains_Advanced_Wastewate...

See page 5 for an easy-to-follow system diagram:

https://www.dcwater.com/sites/default/files/Blue_Plains_Plan...

Yet another great example of how much of our world is powered by unsustainable practices. These are credit card solutions that provide value today at a much higher price tomorrow. The sad thing is that we already know how to address these issues, and instead of encouraging, educating, and improving those processes we are doubling down on the things that are making the system more brittle.

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