There are some problems may affect directly on human healthy and natural, like the energy resources and crops quality. Biogas is clean and environment friendly if we comber with Fossil fuel. If we focus on china situation, Carbon dioxide emissions from consumption in China increase sharply every year, it was 1550 million tons in 1980 and increasing to nearly 8000 million tons in 2009. In 2010, consumption growth accelerated for all over the world, and growth was above average in all regions.
Chinese energy consumption grew by 11.2%, and China surpassed the US as the world’s largest energy consumer. In 2011, China’s share of global energy consumption was 20.3%.thus, biogas can play big role to solve this problem by improving the efficiency of production and create it more reliable and more popular. From this point china proposed many designs that can help the farmer to improve their life and help the environment by decreasing the co2 in the same time decrease the fuel gap.
One of the difficulties that faced biogas system in china is the temperature; it has to be within mesophilic range (32 ± 3 °C). accordingly, it is difficult to generate large amounts of gas with stable performance without heating and the heating must be cheap, reliable, environmental friendly, high performance and efficient. All these properties are available when using solar energy. The relation between ambient temperature and the temperature inside the digesters is one of the most important factors. The gas production has been a significant affect by temperature inside the digester, as the temperature decreases sharply, the gas production also decrees sharply. We propose using greenhouse as the source of heating by four designs.
1) Biogas digester above ground with solar heating by using plastic cover, it consists of 10 pieces of double plastic layer with 2 m in width and 4.5 m in height, while between them is air gab layer. The plastic area is faced to south direction, and the wall faced to north. 2) Biogas digester above ground with solar water heating, the heat sends though the pipe line from solar water heater inside the digester. 3) Underground biogas digesters Heating by using solar greenhouse and solar inlet heating. 4) Underground biogas digesters Heating by using solar greenhouse and Parabolic-trough solar concentrator. These designs can provide the plants by co2 as fertilizer inside the green house also it can provide the plants by the slurry, the slurry is a clean organic fertilizer that potentially increases agricultural productivity.