Biotrix Project - Anaerobic Digestion System in China

Intensive pig rearing can result in odours and pollution, but also presents the opportunity for the production of renewable energy as "biogas". In the Haikou-Luoniushan Agricultural Development Zone (HADZ) in the Island of Hainan (China) eight pig farms in close proximity discharge their waste into an open lagoon which is odorous and contaminated with high COD wastewater.

Anaerobic Digestion System of Pig Waste in Hainan Island, China

Biotrix Asia Company Ltd and Bronzeoak were funded by the UK Foreign and Commonwealth Office (FCO) to review the technical and commercial feasibility of installing an anaerobic digestion system. This would have the potential benefits of reducing the environmental impact on local watercourses as well as generating up to 350kW electricity from the biogas produced from the process. The solids separated from the final effluent would be stabilised, odour reduced and could be used as a fertilizer and/or fish food. In addition, by capturing the methane (21 times more damaging as Greenhouse Gas than Carbon dioxide) which would otherwise be released into the atmosphere, climate change impacts can be mitigated. This might present an opportunity for funding under the Clean Development Mechanism.

In order to achieve these benefits, however, changes in current practice are needed, including retaining as much of the solids as possible for treatment by the digester and reducing the wash water and rain water collected in the effluent drainage system. Currently, solids are collected and removed before digestion resulting in poor gas production.