The efficacy of biogas to protect stored grains from insect pests

Abstract

Stored grains such as rice and wheat (and other grains/pulses) are prone to pest infestation mainly by Sitophilus oryzae, Tribolium castaneum and Rhyzopertha dominica in India and more than 30% of harvested grain is lost to stored grain pests. Protection of the grains by creating an oxygen deficit atmosphere by using carbon-dioxide or biogas is an alternative. In this study, biogas was used as a ‘fumigant’ against S .oryzae, T. castaneum and R. dominica reared on rice (Oryza sativa) and wheat (Triticum aestivum; Semolina and whole wheat flour) grain types, respectively. The optimum biogas flow rate required to remove the oxygen from an empty container and partially grain filled container was found to be 40 ml per minute sustained up to a time leading to an equivalent of three times the volume of the grain container. Using these fumigation conditions 100 % adult mortality was observed in T. castaneum and R. dominica within 24 hours and S. oryzae within 48 hours. Farmers in rural India have been using biogas plants to meet their kitchen energy needs. Some surplus gas could be used for fumigation of stored agro-products making this process inexpensive, environment friendly as well as acceptable to a growing ‘organic food market’.

Keywords

• Stored grain pest
• biogas fumigation
• oxygen-deficit environment
• insect mortality