Opportunities for the use of agroindustrial organic residues in biorefineries

In order to reduce the amount of landfilled waste and to attain the valorization of the material and energy content of organic wastes, the integrated approach based on the biorefinery concept seems to be the most promising in terms of resource recovery, technical feasibility as well as overall environmental and economic benefits. Biorefineries are aimed at converting biomass into biofuels and biobased products, thus they can contribute to reducing the overall consumption of fossil fuels and to minimizing the global carbon footprint of both energy and material production. Compared to conventional refineries, the “bio” configuration allows for producing gaseous/ liquid fuels, plastics and valuable compounds starting from organic biomass instead of hydrocarbons, and may consequently contribute to the reduction of the global carbon footprint and dependency on fossil fuels. Irrespectively of the specific outputs, microbial fermentation, possibly controlled so as to increase the process yields and the products quality, represents the core process in the biorefinery concept. As for the biomass to be treated, an intense debate has grown over the utilization of food crops for biofuels and biomaterials production since the end of 1900, when the opponents stated that such a practice involve turning food for the poor into fuel for the rich, worsen soil erosion and may result into marginal replacement of fossil fuels. A strategy to overcome the food vs. fuel dilemma might be represented by the utilization of residual biomass, such as the biodegradable fraction of municipal waste and agro-industrial residues, as a feedstock for biorefineries. The present paper presents an overview of the most interesting metabolic pathways for liquid and gaseous biofuels. Conceptual schemes for integrating different fermentation processes aimed at biofuels and bioplastics production will be also shown.