Biodegradation promoters for plastics

Abstract

The politically favoured concept of sustainability has focused attention on the need to provide materials with low manufacturing energy demands and preferably made from renewable resources. That such materials should also offer biodegradability as an option in waste disposal, not conflicting with recycling or incineration activities, has served to motivate the development of degradable polymer compositions whose applications have already achieved a modest position in world markets. Claims that goods are overpacked are countered by drawing attention to the need for food hygiene and safety. A call for the recycling of all plastics disposables appears admirable until one learns of the extreme economic and technical problems which beset the recovery of the mixed plastics from MSW (municipal solid waste). Although European politicians have set a 50% target for plastics recycling, recent studies indicate that much more modest levels are realistic. Furthermore the progressive thermal degradation associated with each polymer melt processing operation in the recycling loop would surely eliminate the possibility of continuously cycling a ‘national’ pool of polymer material. An understandable ‘green’ urge to return to natural products brings some unwelcome reminders of the cost of paper and card, especially when food contact quality is demanded, as well as recollections of the unsuitability of paper for packaging wet goods. We are also reminded that paper cannot really be considered as a ‘natural product’ and is separated from its botanical source materials by massive industrial chemical technology such as pulp making, bleaching, coating, glazing and printing techniques. The necessity to conserve non-renewable resources must remain a dominant consideration. We must also face the surprising fact that natural fibre resources would not be adequate to meet the needs of present population levels and expectations.