Writing Blog

January 23, 2008

BioGas Digesters

Filed under: Environment,Gadgets — Rafael Minuesa @ 1:35 AM
Tags: , , , , ,
This is one of a series of articles I posted for the Green Gadget Inspector’s Blog.
You can view the original version at:
* http://gadgetgreeninspector.blogspot.com/2008/01/biogas-digesters.html

Biogas is an incredibly simple technology. It works by turning human or animal waste accumulated into closed chambers into gas that is produced by absence of oxygen, a mixture of mainly methane with some carbon dioxide. This resulting gas can then be used for cooking and lighting or even for generating electrical power, and the solid residue can be used as organic compost.

The power of biogas has been known to Mankind as far back as 10 BC, when it was used in Assyria to heat bath water.
Marco Polo did mention the use of covered sewage tanks in China that are believed to date back to 2,000-3,000 years ago in ancient China.

China is also one of countries in the world that have adopted modern biogas technology earlier in its history. Since the end of the nineteenth century, simple biogas digesters had appeared in the coastal areas of southern China.
Half a century later, in 1958, a campaign was launched in Wuchang to exploit the multiple functions of biogas production, which simultaneously solved the problems of the disposal of manure and improvement of hygiene.
Between the late 1970s and early 1980s when the Chinese government fomented biogas production not only as a way of providing energy, but also as environmental protection and improvement of hygiene, as well as modernization of agriculture. Some 6 million digesters were set up in China at that time, attracting many from the developing countries to learn from it.

The “China dome” digester became the standard construction to the present day, specially for small-scale domestic use.

diagram of biogas production
A biogas tank can produce about 400 cubic meters of biogas. Just 1 cubic metre of biogas can meet the daily energy needs of rural households, mainly for cooking three meals.

Today, farmers in the Chinese province of Guangxi Province are the flagship of Chinese biogas technology. The central government pays half the price of building a $260 biogas “digester” in their backyards. It’s an example of what the Chinese government, in its 11th five-year economic plan, refers to as a new socialist village – environmentally sustainable, socially harmonious and prosperous.

The vast majority of farmers who live in Guangxi don’t earn enough to pay for fuel or electricity. That is if they’re lucky enough to be connected to the power grid in the first place.
All that has changed now and Guanxi is becoming a prosperous place, as well as restoring its natural surroundings. No more cutting wood for cooking and the precious time spent looking for and cutting down trees is now spent in business activities, many of them environmentally friendly.

The Chinese government has launched the “Environment-friendly Homeland” project to develop renewable energy, especially biogas, that aims at having 15 per cent of the country’s energy consumption to come from renewable sources like biogas by 2020.
In Guangxi, there are now 3 million biogas tanks in operation, according to the government, making the province the largest producer of biogas in China if not the world. As each one routes animal and human waste into biogas digesters, they not only prevent vast amounts of methane from escaping into the atmosphere but an estimated 8 million tons of standard coal and 13 million tons of firewood from being burned each year, according to IFAD, the International Fund for Agricultural Development.

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