The growing volumes of food globally lost or wasted and implications for food security and sustainability have raised the concern of researchers, governments, international organizations and grass-root movements. Much research and experiences investigating food waste causes and drivers focus on one specific segment of the food supply chain and limit the analysis to the situation of one or few countries, while the few studies of wider geographical scope also target other relevant and diversified objectives (e.g., food waste definition, quantification, environmental and economic impacts, and recommendations for interventions). This study, carried out by a network of European institutions involved in research and initiatives against food waste, focuses on the analysis of a broad area, Europe, through a wide and systematic literature review and consultation with stakeholders in international focus groups. The food supply chain was divided into seven segments and three main contexts were defined for the examination of food waste sources: Technological, Institutional (related to organisational factors, i.e., business management, economy, legislation, and policy), and Social (related to consumers’ behaviours and lifestyles). Results suggest a wide and multifaceted problem, interconnected across all stages of the food supply chain, from primary production, to final consumption. Within each context, the identified drivers have been grouped according to the possibilities and the type of interventions for food waste reduction. A final cross-contextual prioritization distinguished food waste sources related to (A) inherent characteristics of food; (B) social and economic factors; (C) individual non-readily changeable behaviours; (D) other priorities targeted by private and public stakeholders; (E) diversified factors, such as mismanagement, inefficient legislation, lack of awareness or information; and sub-optimal use of available technologies, which could be more promptly changed. Such diversification of causes calls for specific monitoring systems, targeted policy measures, and actions of individual stakeholders at each stage of the food supply chain.

Rice cultivation produces two waste streams, straw and husk, which could be exploited more effectively. Chemical pretreatment studies using rice residues have largely focussed on straw exploitation alone, and often at low substrate concentrations. Moreover, it is currently not known how rice husk, the more recalcitrant residue, responds to steam explosion without the addition of chemicals. The aim of this study has been to systematically compare the effects of steam explosion severity on the enzymatic saccharification and simultaneous saccharification and fermentation of rice straw and husk produced from a variety widely grown in Vietnam (Oryza sativa, cv. KhangDan18). Rice straw and husk were steam exploded (180–230 °C for 10 min) into hot water and washed to remove fermentation inhibitors. In both cases, pretreatment at 210 °C and above removed most of the noncellulosic sugars. Prolonged saccharification at high cellulase doses showed that rice straw could be saccharified most effectively after steam explosion at 210 °C for 10 min. In contrast, rice husk required more severe pretreatment conditions (220 °C for 10 min), and achieved a much lower yield (75 %), even at optimal conditions. Rice husk also required a higher cellulase dose for optimal saccharification (10 instead of 6 FPU/g DM). Hemicellulase addition failed to improve saccharification. Small pilot scale saccharification at 20 % (w/v) substrate loading in a 10 L high torque bioreactor resulted in similarly high glucose yields for straw (reaching 9 % w/v), but much less for husk. Simultaneous saccharification and fermentation under optimal pretreatment and saccharification conditions showed similar trends, but the ethanol yield from the rice husk was less than 40 % of the theoretical yield. Despite having similar carbohydrate compositions, pretreated rice husk is much less amenable to saccharification than pretreated rice straw. This is likely to attenuate its use as a biorefinery feedstock unless improvements can be made either in the feedstock through breeding and/or modern biotechnology, or in the pretreatment through the employment of improved or alternative technologies. Physiological differences in the overall chemistry or structure may provide clues to the nature of lignocellulosic recalcitrance.