Landfill Biogas for heating Greenhouses and providing Carbon Dioxide Supplement for Plant Growth

Present municipal solid waste landfills generate biogas and leachate. Biogas is flared on site to destroy noxious contaminants and water is extracted from leachate to be drained away. However, biogas could alternatively be a cheap fuel for winter heating and could provide horticultural greenhouses with abundant carbon dioxide to boost plant growth all year long. The paper describes how this idea was tested in a full-scale experiment through a partnership between French Institut National de la Recherche Agronomique (INRA) and a pool of private industries. A commercial boiler was converted to biogas and combustion exhaust gases rich in carbon dioxide were purified to remove phytotoxic residues. A CO2 supplementation technique using these purified exhaust gases was tested. Two soilless rose crops were grown under two identical 300 m2 plastic greenhouses, one equipped with exhaust gas injection and the other one, kept under normal atmosphere, being the control. Crop yields and cut rose quality were compared during 24 months. It was found that the high crop productivity gains allowed by exhaust gas injection bring the major contribution to greenhouse economics, much more important than the reduction of heating costs brought by burning biogas. This underlines the potential for new efficient horticultural greenhouses locating near modern landfill sites in France and elsewhere in developed countries.