[KaiserJeep]

Scientists Want to Mine Sewage For Technologically Important Metals


Image: Heather Lowers/USGS Denver Microbeam Laboratory

Human waste is a useful source of energy. Schemes abound for converting treated waste into biogas for heat, generating electricity, or conversion into biofuels for cars and rockets.

Apparently, the contents of your toilet are also a goldmine. Solid waste can contain copper, silver, gold as well as rare-earth elements like palladium and vanadium that are used in electronics. Scientists at the US Geological Survey are now trying to find out just how much of these useful metals Americans are flushing down their toilets every year, and how they could be recovered. They are presenting details at the American Chemical Society national meeting this week.

Metal traces are in everything—including detergents, hair care products, and odor-fighting socks, said Kathleen Smith, a research geologist with the USGS, in a press release. These metals end up in the leftover solid waste that comes out of wastewater treatment plants. More than 7 million metric tons of nutrient-rich organic matter are produced by sewage treatment facilities in the US every year. About half of these biosolid are used as fertilizer, while the other half is incinerated or sent to landfills.

Recently, other researchers reported in Environmental Science & Technology that the waste from 1 million Americans could contain as much as US $13 million worth of metals.

Smith and her colleagues have analyzed biosolid samples from various Rocky Mountain towns and cities for eight years. They’ve found microscopic particles of metals such as gold, silver, copper, and vanadium. The researchers are now experimenting with methods used by the mining industry to leach metals out of rock.

It’s unclear whether mining sewage for metals will be practical any time soon. Smith said that “the economic and technical feasibility of metal recovery from biosolids needs to be evaluated on a case-by-case basis.”

http://spectrum.ieee.org/tech-talk/energy/renewables/scientists-want-to-mine-sewage-for-technologically-important-metals

http://www.newswise.com/articles/view/630751

http://pubs.acs.org/doi/abs/10.1021/es505329q

I realized the many opportunities for humor, and decided to refrain.

[Fishman]

Er, um, how does one respond to this thread? Perhaps humor is the best way KJ. Does one dump a lode as opposed to a load? So heavy metal covers mining, certain music, and the morning constitution?

[KaiserJeep]

Er, um, how does one respond to this thread? Perhaps humor is the best way KJ. Does one dump a lode as opposed to a load? So heavy metal covers mining, certain music, and the morning constitution?

My point was simply that this is a serious topic that deserves more than potty-mouthed "humor". There are lots of Doomsteads owned by lots of PO.com members which have either "mound" sewage treatments or conventional unpowered septic tanks and leach fields. When you combine this inadequate water treatment with people who are using shampoos, soaps, conditioners, medicines, and other personal care products that contain a witches brew of scents, dyes, antibiotics, organic chemicals, and metals, these Doomsteads with their inadequate sewage systems amount to gross toxic waste polluters. We are no longer 19th century consumers who make soap from wood-ash lye and animal fats.

Effective greywater management requires another separate set of cold water plumbing and above-ground tanks in a heated space that treat such water with ion-exchange resins, semi-permeable membranes, ultraviolet disinfectants, chemical disinfectants, and effective micro-filtration. Then the processed and treated greywater can be safely used for flushing and landscape (but not food) irrigation. Untreated greywater should NEVER be added to a septic tank or leach field and the concentrated toxics from the greywater treatment should be treated as the toxic waste they are - separately disposed of in a manner that prevents these substances from entering a water table that you are tapping for drinking water.



For those of you who think that simple sewage treatment as designed in the 18th century is perfectly fine and adequate for 21st century high tech chemical consumption, you are clearly wrong, and your attitudes obsolete. The fact that most municipal waste water treatment is also inadequate is a whole topic on it's own - urban houses need greywater treatment and residence-scale recycling just as do rural doomsteads.

As for your dream of a low tech Doomstead and simple plumbing (or even an outhouse), this is only appropriate after you have gotten your spouse and every other family member to abandon soaps, shampoos, medicines, and other products that would pass unaffected through a septic field or a pit toilet vault and back into your drinking water supply.