Vast energy value in human waste: UN University

03-Nov-2015 - Japan

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.

Corinne Schuster-Wallace, UNU-INWEH

Biogas, approximately 60 percent methane by volume, is generated through the bacterial breakdown of organic matter in an oxygen free system.

A report today 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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