Case Story China

Corn straw biogas production in cold northern region of China

December 2021

The problems in digesting corn straw

Corn straw has a high dry matter content, with a strong binding force of cellulose, hemicellulose and lignin. Biogas production from straw is exemplified by low yield and low rate of production, necessitating long retention times. Furthermore dark yellow lignocellulosic materials have poor hydrophilicity and as such straw is prone to float and generate crusts on the liquor surface of the digestion tank; this impacts negatively on the efficiency of anaerobic digestion. To further add to difficulties, the ambient temperature in this northern region of China is low in winter; fluctuations in temperature within the digestion tank may also lead to instability in biogas production.

Corn straw biogas plant in Fuyu county, Heilongjiang, China

The biogas plant located in a state-owned farm (Fanrong stock farm, Fuyu county, Qiqihar city, Heilongjiang Porvince) is the first biogas CHP facility to use pure yellow corn straw as feedstock in the alpine region of China. The 2MWe facility consumes 30,000 tonnes of yellow corn straw on a site of 2.3 ha; it was constructed (and is operated) by Nanjing General New Energy Power Co. Ltd. at a total investment cost of 55 million yuan. The project started commissioning in November 2016 and has been running continuously for over 30,000 hours. The processes employed (Figure 2) seek to optimise the efficiency of biogas production and the overall economics by producing high-value “breeding seedling soil” from biogas residue.