When we talk about methane I think about all of the manure currently being put out by our cattle and hog confinements. How much energy could we be producing. Renewable energy. Imagine being able to hook-up every hog confinement to a methane powered generator that was hooked directly to the grid.
With all these excellent ideas AND cost-efficiency involved, we might see the concepts developed on a large scale, as in municipal sewage facilities that could power themselves and provide useful by-products. I can recall when I was a kid people would go to the local sewage plant where tomatoes sprang wild in the settling beds. Plenty of water and fertilizer, I assume. Then there was a major oubreak of hepatitis, and that was stopped. 50 years later, with the new technologies available to us, we should be able to generate power, reasonably clean water, safe organic fertilizer, and ingredients of which to create chemical fertilizers.
My father-in-law engineered several fertilizer production facilities in the world, and he always listed the main requirements as close access to ship and rail lterminals and an inexpensive source of urea or chemicals from which they coould synthesize it.
I understood that the NASA toilet, although a problem sometimes, recycled water for the astronauts to drink. I don't know what process it used but I am sure one or more of the teams involved is probably looking into it. I hope the results can meet the cost per daily use targets.
I would think a mechanical vacuum pump type system would be able to extract the water via low pressure boiling and leave behind dried material for use as a fertilizer once it was sterilized. Perhaps some kind of UV or Radiation treatment would be sufficient to sterilize the waste.
The user of the toilet has to do the manual pumping of the vacuum system.
Actually, some of the grant money, under the broader Sanitation Science and Technology funding, is going toward a project where methane is an output. The Gates Foundation documentation says: "A grantee is developing an algae-based water treatment system that would use bacteria to treat a community's waste while producing renewable resources: a nutrient-rich fertilizer for agricultural use and bio-methane to power the sanitation facility as well as the neighboring community."
This caught my eye as well and I applaud the foundation's efforts and the innovative students and university researchers that will rise to the task. Apparently, the foundation last week chose more than 500 scientific ideas out of 20,000 proposals as part of its Grand Challenges Explorations grants. Each grant gets $100,000, according to published reports, and the monies are going to research projects aimed at stamping out malaria, HIV, and addressing other global health problems.
The National University of Singapore team is developing a waterless toilet under its Gates Foundation grant. It uses air (pneumatic flushing) instead of water. It also has a scheme to divert the urine. It's not described but I'm guess that needn't be sophisticated; a size-based filtering scheme would do the trick. Interestingly, the toilet recovers clean water via a treatement and desalinization process.
I went back through the documentation to see if urea recovery was listed as an objective of any of the efforts, and it wasn't. Doesn't mean it's not being looked at somewhere/somehow, but it's definitely an important and relevant question, David. Perhaps it's not compatible with the low-cost goal. A Google seach notes that there's been some work on urea recovery by the U.S. Army Corps of Engineers R&D Center.
I am surprised to see nothing here about the recovery of urea for use in the manufacturing of fertilizer products. Most of the areas mentioned are also in poor shape agriculturally, so it would make sense for these people to be able to improve their soil and increase food crop production at the same time.
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