Environmental impact of tomato purée : anaerobic digestion of by-products as mitigation strategy

Agricultural by-products and wastes usually represent a cost for farmers and agro-food industries. Nevertheless, concerning their use to produce biogas by the anaerobic digestion (AD) there are still unexplored possibilities. In fact, differently than for animal slurries already widely used as feedstock for biogas production, the wastes from agro-food industries are more rarely exploited as feedstock for energy purpose and therefore often represent an economic and environmental issue. In this study, the environmental benefits arising from the AD of tomato by-products was evaluated, using the Life Cycle Assessment, as strategy to reduce the environmental load of tomato purée production systems. Nine impact categories were evaluated using the Recipe midpoint LCIA method. Data concerning tomato purée production were collected in an agro-food industry processing each year 200.000 tons of fresh tomato. Laboratory tests were carried out as regard to the methane production of the different tomato by-products. Technical and operative data concerning the operativeness of AD plants were achieved by means of surveys in real AD plants fed with by-products from food industry The AD of tomato by-products entails an environmental impact reduction for the tomato purée. The achieved results could be up-scaled to all the food industries with high heat demand producing considerable amounts of fermentable by-products employable as feedstock for biogas production.