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New Micro-Biogas Plant

Together with the urban planner and energy activist T. H. Culhane from the US, (see: solarcities.blogspot.com) the participants of the Global Campus built a new, small biogas plant within three days and finished another one that had been started last year. With the organic kitchen waste of just one day, enough gas for two hours of cooking can be produced. This way the solar kitchen can be complemented with a biogas driven stove at night or during rainy days.


Can it really be that easy? Shredded organic kitchen waste is being mixed with water in a hermetically sealed container and then given to stomach bacteria to be eaten. After a few days, the gasometer in the gas container, mounted above the fermenter, is already climbing; biogas is being passed onto to the user through a thin hose, and we can light a gas lantern or cook. Each bucket of kitchen residue produces gas for two hours of cooking. In addition to this, valuable liquid fertilizer for the garden is produced as a by-product.



T. H. Culhane himself could hardly believe it when he first met Dr. Anand Karve from the ARTI-Institute two years ago in the Indian industrial town of Poona. In the micro biogas plants, the specialist used kitchen residue instead of the usual cow dung. The conclusion he draws: "It is 400 times as efficient as the system with cow dung!"



For years, T. H. has been working in the slums of Cairo and other African cities in order to develop decentralized solutions for energy production together with the local people.


"I mean decentralized in fact – not what Bill Gates means by decentralized when he wants to supply all African villages with micro nuclear power plants. Even if it wasn't a catastrophe for human health and the environment – it would deprive the people of something decisive: their capacity to think for themselves and find their own solutions."


At first, his plan was to bring decentralized solar energy into the slums. "But the people there suffered not only from the lack of energy; they also had another giant problem: They were drowning in garbage. From metal and plastic, they produce merchandise. But what to do with the continuous horrible smell and the misery of the organic waste where rats prosper and children become sick? For composting, there is often not enough space."



With the biogas idea, organic waste becomes a valuable raw material. In the poorest settlements in the African bush and in slums, T. H. experimented together with the inhabitants. They used what they found – buckets, plastic containers, hoses, old gas cookers – to built a biogas fermenter, a gas container, almost in the same size, to be hung above, the inputs for the kitchen waste, the outlets for gas and the liquid fertilizer, and the end user devices.


T.H. also used this improvisational capacity in Tamera, and together with the enthused participants of the Global Campus, he built a functioning biogas system for the solar kitchen of the testfield within two days. It was in one of his promotion videos in which a slum inhabitant said: "I love it, because I built it myself.”


T. H. wrote the lyrics for a song about this which he accompanies with his electric guitar.


The refrain is tuneful and catchy: "It´s the same gas we pass."



In fact, it's the same bacteria which do in the fermenter exactly what they do in our stomach: digesting food. This is also why organic kitchen waste is much more suitable for biogas plants than compost toilets or pure vegetable mass. The general rule is: The more diverse the food for the fermenter, the better. With a few shovels of cow dung diluted in warm water, the biogas system is initiated, the bacteria find their food and start to work.



The second product resulting from a biogas plant is a fertilizer, a concentrated nutrient solution containing all the elements that made the plant grow in the first place. In many aspects, it is even more valuable than compost, because from the closed container, no ammonium escapes, and all the nitrogen is kept as fertilizer.



"The only delimiting factor is the fact that the bacteria in a smooth 1000 liter container can digest only one bucketful of kitchen waste. The bacteria do not swim in the compost soup, they live on firm surfaces, on the bottom and on the walls. But in a settlement in Kenya, the inhabitants had this idea: We could increase the surface in the fermenter. Inspired by the way the inside of a cows tummy i.e. is folded, we are now building drainage pipes with big surfaces into the container so as to increase the number of bacteria and thus the efficiency of the fermenter."



The Culhanes demonstrate the use of an "Insinkerator" feedstock preparation device, a common household "garbage disposal" that Solar CITIES has re-purposed for the efficient production of biogas and compost. The kitchen waste is being shredded with this insinkerator, mixed with dishwashing water and poured into the fermenter. It is painted black on the outside, as bacteria work best when it is warm.


Tamera's chief biogas engineer Martin Funk: "I am enchanted, T. H. is a true master of LowTech – the simple technological solution. Both plants are filled and are slowly starting to produce. Within three weeks, they should be fully productive, and then we only need to install the pipes, and we will be able to cook with biogas in the winter. At night and during winter, this will be an important addition to our solar energy."


Addition: For finishing the biogas plant - for the toilet roofs, wood, piles, toilet with a low need of water and the design of the surrounding we still need 4.800 Euros.

If you can support us, please write to solarvillage(at)tamera.org


Find some video clips and songs of T. H. Culhane:

Thanksgiving Song (More and More):

Portrait of T. H. Culhane and weblog of the Global Campus 2011
Order the book "Terra Nova" here