This blog aims to describe in brief the history of China’s national biogas program and its transition phases in both the 1980s (moving to prefabricated plastic digesters) and more recently in promoting household scale systems, as well as how this program compares to other government-scale programs in household and centralised biodigesters.   
The Chinese National Biogas Program is one of the most cited examples of a successful biogas dissemination program at a government scale. The first biodigesters started appearing in China in the 1920s, and from the 1970s onwards the government began introducing household-scale centralised biodigester systems for rural communities under the predecessor of the current program. The first major transition in the program took place in the 1980s. Previously to this, most biodigesters in the country were constructed on-site from brick or concrete, however this period saw the introduction of what are known in the country as “commercialised digesters”. This covers three constructions of prefabricated biodigesters. Fibreglass-reinforced plastic (FRP) digesters began appearing in the 1980s themselves, whilst so-called plastic soft (PS) and plastic hard (PH) digesters came into the market in the mid-90s. These digesters offered significant commercial and operational advantages, being able to be constructed at a central site and then disseminated, as well as being more reliable, having lower maintenance requirements and a better performance overall.
Source: Adapted from Zuzhang (2014) Domestic biogas in a changing China: Can biogas still meet the energy needs of China’s rural households, http://pubs.iied.org/pdfs/16553IIED.pdf
As of 2011, 41.68 million households were using biogas services through the National Biogas Program. As of 2010 production capacity for the three previously-described prefabricated digester types was approximately 2,500,000 per year, and as of 2014, approximately 50 million households had been reached with biogas supply, using over 16 million cubic metres of biogas per year . At least one prefabricated digester manufacturer exists in each Chinese province, over 100 in total. These digesters are also marketed across South-East Asia, and also recently to Sub-Saharan Africa.
However, there exist a number of present challenges to the continued development of the Program. Current funding for biogas digester construction predominantly comes from state, regional and government sources in the form of a subsidy for rural households. Rural households are expected to contribute, but this varies widely from just the labour costs, to 50-70% of the total installation costs. Some funding criteria stipulated by the government also exclude large proportions of the rural population: for a village to qualify for biodigester subsidies for example, at least 70% of the households must own sufficient livestock. This funding regime, as it exists, makes no provision for servicing and maintenance, and whilst biogas service cooperatives are beginning to appear in rural areas, no effort has been made to assess the current proportion of functioning digesters nor repair any identified non-functioning systems at a local government level.
Possibly the largest constraint to the continued operation and growth of the program is internal migration in China. The rural population is falling significantly as urban development continues, with huge number of rural people moving to urban areas for greater employment prospects and wages. This also contributes to biodigester effectiveness; with traditional animal husbandry industries giving way to larger, centralised livestock farming, feedstock regimes are decreasing in suitability in rural China for household-scale digesters, presenting an ongoing constraint to the operation of the program.
– Xavier Lemaire & Daniel Kerr, UCL Energy Institute
 IRENA (2014) Renewable Energy Prospects: China. Available at http://irena.org/remap/IRENA_REmap_China_report_2014.pdf