Vast energy value in human waste

Nov 9, 2015

Source: United Nations University

Biogas from human waste, safely obtained under controlled circumstances using innovative technologies, is a potential fuel source great enough in theory to generate electricity for up to 138 million households — the number of households in Indonesia, Brazil, and Ethiopia combined.

A report from UN University’s Canadian-based Institute for Water, Environment and Health estimates that biogas potentially available from human waste worldwide would have a value of up to US$ 9.5 billion in natural gas equivalent.

And the residue, dried and charred, could produce 2 million tonnes of charcoal-equivalent fuel, curbing the destruction of trees.

Finally, experts say, the large energy value would prove small relative to that of the global health and environmental benefits that would accrue from the safe treatment of human waste in low-resource settings.

“Rather than treating our waste as a major liability, with proper controls in place we can use it in several circumstances to build innovative and sustained financing for development while protecting health and improving our environment in the process,” according to the report, “Valuing Human Waste as an Energy Resource.”

The report uses average waste volume statistics, high and low assumptions for the percentage of concentrated combustable solids contained (25 — 45%), its conversion into biogas and charcoal-like fuel and their thermal equivalents (natural gas and charcoal), to calculate the potential energy value of human waste.

Biogas, approximately 60% methane by volume, is generated through the bacterial breakdown of faecal matter, and any other organic matter, in an oxygen free (anaerobic) system.

Dried and charred faecal sludge, meanwhile, has energy content similar to coal and charcoal.

UN figures show that 2.4 billion people lack access to improved sanitation facilities and almost 1 billion people (about 60% of them in India) don’t use toilets at all, defecating instead in the open.

If the waste of only those practicing open defecation was targeted, the financial value of biogas potentially generated exceeds US$ 200 million per year and could reach as high as $376 million. The energy value would equal that of the fuel needed to generate electricity for 10 million to 18 million local households. Processing the residual faecal sludge, meanwhile, would yield the equivalent of 4.8 million to 8.5 million tonnes of charcoal to help power industrial furnaces, for example.


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5 comments on “Vast energy value in human waste

  • In nature everything gets recycled, sometimes on very long time cycles. That is what we have to aim for.

    One thing that bothers me is the way we do things like make gold leaf, tack in onto ornaments in ways that it will never be recycled. We should be more careful not to disperse precious metals.



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  • Not a new idea, perhaps the collection problem hasn’t been thought through? I read somewhere that Germany used anaerobic digestion of vegetable matter to produce fertiliser slurry which they then used to grow potatoes that they subsequently fermented to produce alcohol for rocket fuel. They used the methane to power the plant machinery.

    On the dispersal of metals a really careless dispersal method is to blast a few tons of metals into the air in fire work displays.



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  • @OP – Biogas from human waste, safely obtained under controlled circumstances using innovative technologies, is a potential fuel source great enough in theory to generate electricity for up to 138 million households

    We only have to look as far as cultures which use dried animal dung for fuel, to recognise that the individual human does not produce enough dung to produce a significant amount of energy in comparison to their personal energy usage.

    That therefore raises the questions of collection, transport, and contamination of sewage with other waste products.
    Once these are considered, there are probably only limited opportunities in specific locations where large volumes of sewage can be quickly collected, with transport only over short distances.
    Perhaps using generated gas to power the sewage treatment plant could be viable.



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