The Soufriere Marine Management Association has collaborated with a local pig farmer at Ravine Claire to construct a model biogas digester. Construction of the holding tank has been completed. The next phase is to cover the tank with a plastic sheet that will expand as gas is collected. The project is funded by the Global Environment Facility. Worldwide animal farmers have for years realized the energy potential in animal waste and have been using digesters to convert organic matter into biogas. In the 1980’s a GTZ project installed 13 steel dome biogas digesters around St. Lucia. The Still Plantation in Soufriere had a digester installed from that project and utilized the gas produced in their restaurant daily until the digester became too costly to maintain and was decommissioned in the 1990’s. At our count, there was only one still in operation in 2008 which the owner decommissioned late last year. This farmer used the gas for cooking in his home and then had to purchase a tank of cooking gas (LPG) for the first time then since 1986.
How does it work?
Animal manure and organic matter are fed into an enclosed tank. In the absence of oxygen, bacteria convert animal manure and organic matter into biogas (methane and carbon dioxide) and a nutrient rich effluent. Biogas is a colourless, odourless gas that burns with a clean blue flame. The biogas is collected from the top of the digester and piped to a kitchen for cooking and other uses such as for lighting and to generate electricity. The effluent is an excellent fertilizer which can be dried and sold as an organic alternative.
The SMMA is promoting the use of biogas digesters to animal farmers in an effort to reduce the volume of raw untreated animal waste that flows into watercourses in Soufriere. Previous SMMA research has documented high levels of faecal coliform bacteria in the Soufriere River and bay which is a source of concern. Consultations with Soufriere residents on the source(s) of sewage pollution suggested animal farms as one of the pollution sources. With a growing number of pig farms located adjacent to or in close proximity to watercourses the volume of animal waste and associated faecal bacteria and pathogens will increase unless proper waste management techniques are implemented. This has serious health implications for residents and the marine ecosystem.
Digesters for Farm Waste Management
The Ministry of Agriculture has commenced a farm certification programme which encourages the use of biogas digesters as one method of waste management. Technicians from the ministry have been providing support in the design and installation of the digester for this project. The benefits to farmers include: qualification for farm waste management certification, odour control, free cooking fuel and a potential income generating fertilizer. The community benefits from less air and water pollution and a sustainable agricultural sector.