SIMULATION OF THE ANAEROBIC DIGESTION OF FOOD WASTE

This study has established that the use of a computer model, the Anaerobic Digestion Model 1, is suitable for investigation of the stability and energy balance of the anaerobic digestion of food waste. In simulations, digestion of undiluted food waste was less stable than that of sewage sludge or mixtures of the two, but gave much higher average methane yields per volume of digester. In the best case scenario simulations, food waste resulted in the production of 5.3 Nm3 of methane per day per m3 of digester volume, much higher than that of sewage sludge alone at 1.1 Nm3 of methane per day per m3. There was no substantial difference in the yield per volatile solids added. Food waste, however, did not sustain a stable digestion if its cation content was below a certain level. Mixing food waste and sewage sludge allowed digestion with a lower cation content. The changes in composition of food waste feedstock caused great variation in biogas output and even more so volatile fatty acid concentration, which lowered the digestion stability. Modelling anaerobic digestion allowed simulation of failure scenarios and gave insights into the importance of the cation/anion balance and the magnitude of variability in feedstocks.

Polymer film packaging for food: An environmental assessment

Plastics packaging is ubiquitous in the food industry, fulfilling a range of functions including a significant role in reducing food waste. The public perception of packaging, however, is dominated by end-of-life aspects, when the packaging becomes waste often found littering urban, rural and marine environments. A balanced analysis of the role of packaging demands that the whole lifecycle is examined, looking not only at the packaging itself but also at the product being packaged. This paper focuses on packaging in the meat and cheese industry, analysing the impact of films and bags. The functions of packaging are defined and the environmental impact of delivering these functions is assessed. The influence of packaging on levels of waste and energy consumption elsewhere in the system is examined, including the contentious issue of end-of-life for packaging. Strategies for minimizing the environmental impact of the packaging itself involve reduction in the amount of material used (thinner packaging), rather than emphasizing end-of-life issues. Currently, with polymer recycling not at a high level, evidence suggests that this strategy is justifiable. Biodegradable polymers may have some potential for improving environmental performance, but are still problematic. The conclusion is that although current packaging is in some ways wasteful and inefficient, the alternatives are even less desirable. © 2013 Elsevier B.V. All rights reserved.