Sludge Power - Anaerobic digestion’s output (biogas) can be used effectively


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Sludge Power - Anaerobic digestion’s output (biogas) can be used effectively

Sludge Power

Back in 1964, P L McCarty of Stanford University published papers on Anaerobic Waste Treatment Fundamentals. These are still available online at .

These classical papers gives an in-depth knowledge on anaerobic digestion. Students, wishing to learn about anaerobic digestion, and those in-practice professionals wishing to refresh their knowledge on anaerobic digestion, must go through these papers.

In 1969, P L McCarty and C J Young developed anaerobic filters. Anaerobic digestion, as is known, produce methane and carbon dioxide. Methane is an energy gas, meaning that it can be used for energy purpose.

James Jaffrey’s blog on Benefits of Backpack Biogas ( ), carries an interesting picture. It shows a woman, Salome Zeresulos, carrying a backpack filled with biogas through the streets of Addis Ababa. *

According to the blog, the backpack is 1.5 metre wide, pillow-shaped inflatable blue bag, and is filled with biogas from a special biogas digester, a sealed compost bag. Afterwards, the biogas-filled backpack can be hoisted onto a back for carrying to a home where it is hooked up to a biogas cooking stove.

James Jaffrey also makes a powerful opening statement is his blog. He says:

Billions of dollars of aid has been pumped into Africa. Yet effective change too often remains an elusive outcome, leading to a vicious cycle: more needs, more aid but still little change. How to resolve this seemingly intractable dilemma?

It is, at the same time, a bit surprising that, in this case, a massive donor aid, is not working in terms of progress in Africa.

Lijin Zhong, Xiaotian Fu, Betsy Otto and Andrew Maddocks, in their recent (22 March 2016) write-up:
World Water Day: How “Sludge” Can Power China’s Cities While Cutting Emissions, talk of how the Chinese are using sludge to produce power ( ).

Linjin Zhong, et al., calling it “sludge-to-power” treatment, says: Bioenergy plants work by converting the organic matter, or “sludge,” left over from treated sewage into electricity. The plant heats the solid waste, then employs microbes to digest it, which produce methane. The plant then burns that methane to generate power for water treatment. Excess methane can generate electricity for the facility, or power cars as a substitute for compressed natural gas (CNG). Leftover solid waste is sterilized, and can be used as fertilizer for certain types of crops. Other sludge-energy byproducts – called biochar – can be used to grow potted trees on landfill sites to restore landscapes or on city streets to help lower temperatures and improve air quality.

Anaerobic digestion’s output can be used effectively. However, a constraint that can crop up, is to ensure that the process works properly, as the methane-forming bacteria (species of Methanobacterium, Methanococcus and Methanosarcina) are highly weak in nature. They are strict anaerobes, grow over a wide range of temperature, difficult to cultivate and, they remain inalienable. They are highly sensitive to low pH conditions. All this means that a fair amount of knowledge in anaerobic digestion, and a careful operation is required, if the system is to work perfectly.

F H Mughal

* Note by moderator: the biogas backpack was also mentioned here on the forum:
F H Mughal (Mr.)
Karachi, Pakistan
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