Visit to Rural Countryside to Study China’s Bio-Gas

The Chinese government’s passage of the Renewable Energy Law in 2005 demonstrated China’s concern for creating a sustainable future and improving the lives of rural farmers, see Chapter 4, Article 16 and Article 18, in English and Chinese.  According to China Daily, the government aims to have the country’s renewable energy consumption account for 15% of the total energy consumption by 2020.  Yet it is difficult for us to conceptualize the meaning and impact of this law without providing a personal account.

Two weeks ago, I was able to travel to Yunnan Province’s Er Yuan County (洱源县), which is an hour and a half away from Dali.  Er Yuan County is well-known for its cow industry throughout the province.   According to the Er Yuan County Environmental Protection Bureau , in 2008, Er Yuan County had approximately 70,000 cows that produced 700,000 tons of manure each year.   Since there is no waste management system in place in the countryside, animal and human waste is the largest source of agricultural pollution.   In order to maintain farmer productivity and protect the environment, biogas digesters were installed to turn manure into gas for cooking.  Biogas is obtained by the fermentation of animal and/or human waste into digesters.

While biogas digesters have been in place since the 1970s, it is only since 2004-2006 that the quality of biogas digesters has improved and is used on a larger scale.  Additionally, due to the passage of the Renewable Energy Law, the government has been very active in promoting the use of biogas digesters to farmers and has set up quotas for the number of biogas digesters to be installed.  From the conversations I had with local farmers, each household received a significant subsidy from the government to construct a biogas digester.  Typically, a biogas digester costs approximately 2,000 RMB ($292 USD) to construct, but the government subsidizes the majority of the cost, and farmers only pay approximately 500 RMB ($73 USD).

The local Yunnan Provincial news site reported that in 2006, 20,000 tons of waste was managed and turned into clean energy by the 800 households that have set up biogas digesters.  Er Yuan County is also the first county in Yunnan Province to set up several solar powered animal and human waste biogas stations that turn manure into gas.  The leftover manure is turned into slurry, which is high in nutrient content and used as an organic fertilizer.  Farmers can sell their animal waste at 40 yuan/ton (around $5.85/ton) at these stations.  These stations have successfully managed 4,000 tons of waste every year and have reduced the pollution in the neighboring body of water.

A major impetus of setting up these waste stations was to divert manure from contaminating the local people’s major water source, Er Hai Lake.  Er Yuan County is located at the head of Er Hai Lake and serves as a river basin.  Any trace of pollution from Er Yuan County that enters the water will flow down and contaminate Er Hai Lake.  The biogas digesters have played an important role in protecting the ecosystem of Er Hai Lake and servicing as a natural resource to the local people.

Despite all the merits of biogas digesters, there are still several issues that prevent it from reaching its full potential as a reliable source of clean energy.  The temperature of the fermentation process is critical – it must reach 35 or 35 degrees Celsius to operate effectively.  During my visit, the cool outside temperature and the poor insulation of the household biogas digester meant it wasn’t very effective in producing gas in the winter, though it is effective in the spring and summer months.  However, the community biogas stations that receive energy from the solar panels are effective in producing gas.  While newer models are in place to address the temperature problem, the household biogas digesters in the villages I visited are of an older model and the villagers lacked the technical expertise to address this problem.  Additionally, the plastic tubes connecting from the biogas digester to the biogas stove in the kitchen needs better insulation to prevent loss of heat.

While the installation of biogas digesters in Er Yuan County has undeniably brought about numerous benefits to farmers and the environment, there are still technical challenges that need to be overcome for biogas to be used on a large scale.

One response to “Visit to Rural Countryside to Study China’s Bio-Gas

  1. Michael Davidson

    Hi Amy,

    Good post. I’m glad you could visit the biogas villages. I did not get to see the solar-powered community stations you talked about. They sound fascinating. Who funded the project?

    A few comments on biogas digesters and the issues you raised. The benefits of a digester indeed extend beyond the clean gas at low cost. Reduction in non-point source pollution, increased hygiene (both from animal waste and outhouses) and reduced deforestation pressure in Yunnan, especially, are some of the co-benefits.

    The ambient temperature is often cited as a constraint on biogas digester adoption in many areas. However, Yunnan is not one of them. Yunnan has an ideal climate for the fermentation process, and it’s more likely that if the pressure drops in winter months, it is poorly maintained. I have visited installations in chilly Gansu and they work fine throughout the winter…because they are properly cared for.

    The tubing, while seemingly simple, is often the largest source of inefficiency. They develop leaks over time and the pressure drops. I’ve seen some that have turned yellow and still no one noticed. It is not so much the temperature within the tube, but that a proper seal is maintained. Users need to do pressure tests occasionally and replace the whole assembly every few years.

    A last note about the subsidies. The Renewable Energy Law created a feed-in tariff for on-grid renewable energy for electricity production. The real money for biogas production was part of the National Rural Biogas Construction Program (农村沼气国债项目) begun in 2003. There were of course many programs at the regional level before then, but they were poorly maintained, and the 1980s is known for years in which the number of new installations was smaller than the number that went offline during the same period.

    Keep me abreast of the latest!

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