Potential raw materials for biorefineries to ensure food security: The Cocoyam case

During the last decades, the use of biomass has increased considerably for the production of chemicals, biofuels, and direct bioenergy, among others. However, the use of first and second-generation biomass has been raising concerns about the possibilities of threatening food security and to compete for the use of productive land. Biomass is a versatile feedstock based on different compounds with the potential to obtain a considerable spectrum of products. However, it is still necessary to look for cheap raw materials that might have high availability and with the potential for obtaining added-value products without risking food security and decreasing the environmental impact. Cocoyam (Xanthosoma sagittifolium) is a plant grown extensively in tropical regions and mainly used as a source of starch and animal feed. It consists of three parts: leaves, which have a high protein and fiber content; stem, composed of lignocellulose; and a corm, with a starch content similar to that of cassava and potatoes. Nigeria, China and Ghana produce around 1.3, 1.18 and 0.9 million tonnes/year, respectively. In Colombia, they are not technified crops, but it is used mainly as animal feed. Cocoyam use is generally limited to the leaves, discarding the other parts. Based on the potential use of these discarded parts, this work proposed a biorefinery using cocoyam as feedstock to obtain different products: a feed (animal consumption), a biofuel (ethanol), a bioproduct used as food preservative (lactic acid) and food for direct human consumption (starch). The assessment of the potential of the biorefinery included an experimental stage to obtain the products, a simulation stage of techno-economic and environmental assessment and an analysis of the scale to determine minimum processing scale of feedstock at which the biorefinery is economically feasible. The obtained results showed that exploiting the compositional diversity of an unused raw material, it is possible to efficiently produce chemicals, food, feed and biofuels under a biorefinery scheme. The obtained yields for the feed additive, ethanol, lactic acid and starch were 0.147, 0.062, 0.110 and 0.192 kg/kg of feedstock, respectively. Starch, lactic acid and the feed additive are the products that have a higher contribution to the incomes of the process. The minimum processing scale for economic feasibility of the biorefinery was 880 ton/day, which is in the order of commercial scale production plants. The proposed process integrally uses a raw material and does not threaten food security.