4 ms·

Relevant HN discussion from last month: https://news.ycombinator.com/item?id=34182343 https://news.ycombinator.com/item?id=34182343 When it comes to recapturi

Relevant HN discussion from last month: https://news.ycombinator.com/item?id=34182343 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 https://en.wikipedia.org/wiki/Milorganite

skybrian 4y ago
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 https://www.publishersweekly.com/9781567510607
- farmaway 4y ago
  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-could-county-supervisors-to-settle-decade-long-sludge-lawsuit/article_c953e076-7c76-11e7-bd23-932fba132466.html 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://en.wikipedia.org/wiki/Thermal_hydrolysis https://www.cambi.com/what-we-do/thermal-hydrolysis/how-does-thermal-hydrolysis-work/ 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_Wastewater_Treatment_Plant#Sludge_treatment 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_Plant_brochure.pdf https://www.dcwater.com/sites/default/files/Blue_Plains_Plan...

skybrian 4y ago

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 https://www.publishersweekly.com/9781567510607

farmaway 4y ago
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-could-county-supervisors-to-settle-decade-long-sludge-lawsuit/article_c953e076-7c76-11e7-bd23-932fba132466.html 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://en.wikipedia.org/wiki/Thermal_hydrolysis https://www.cambi.com/what-we-do/thermal-hydrolysis/how-does-thermal-hydrolysis-work/ 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_Wastewater_Treatment_Plant#Sludge_treatment 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_Plant_brochure.pdf https://www.dcwater.com/sites/default/files/Blue_Plains_Plan...