Biogas is potentially one of the most economical sources of energy for mountain farmers. In China, the Shenzhen Puxin Science and Technology Co., Ltd carried out many years’ study to develop the traditional biogas plant and produce a new generation hydraulic biogas system named the PUXIN Biogas Plant. The Puxin biogas plant has three major parts.

Concrete digester: The stomach (digester) of the plant is constructed by casting concrete (1:3:3 mixture of cement, smashed stone, and sand) with the help of ‘scaffolding’ (a steel mould). Hence it is stronger and more earthquake resistant than the traditional plants made of brick or stone mortar. The volume of the digester varies according to the frame; the two basic sizes are 6 and 10 cu m.

Neck and cover: The round part above the digester is known as the neck. This is also made with the help of a steel frame. The neck is essential for fixing the gasholder. The water level above the gasholder in the neck determines the gas pressure. The neck is covered with fi ve concrete covers (slabs), which make the plant attractive and help utilise the plant area.

Gasholder: The gasholder is made of reinforced glassfibre which is 100% air and water tight. The diameter of the gas holder is 1.6 m; the volume varies with the height.

The Puxin biogas plant has more advantages than the traditional fixed dome plant:

• It is easier and quicker to build.
• It is environmentally friendly, durable and easy to repair.
• Any solid biodegradable materials can be used including grass and straw so that it is not necessary for the farmer to have a large number of cattle.
• If used as a batch plant, there is regular discharge of gas over a long time (5-6 months), but the materials have to be replaced after 5-6 months.
• The slurry from the plant is perfectly digested and consists of 90% water. The plant is a very effective producer of bio-fertiliser to replace chemical fertiliser.