A recent study discusses biodegradable plastics (BDPs) as an alternative to conventional plastic packaging. It investigates their advantages and the possibilities for waste management.

Over 67 million tonnes of packaging waste is generated annually in the EU. The EU directive on Packaging and Packaging Waste requires Member States to reduce waste and develop recycling systems. Although the recycling of all types of packaging has increased, rates remain low for most plastic packaging.

BDPs offer an alternative to traditional petrochemical-based plastic as they can be disposed of by composting.

The study compares BDPs and conventional plastics. It classifies BDPs as either bio-based or petrochemical-based. The former are renewable and produced from natural origins such as plants, animals or micro-organisms, e.g. natural rubber and polyactic acid (PLA) - a polyester derived from corn starch or sugarcane. Petrochemical based BDPs are not renewable, but some can have a certain amount of biodegradability. Examples include polyvinyl alcohol and aliphatic polyesters.

Many commercial BDPs combine materials from both classes of plastic to reduce cost and/or enhance performance. Current production of global BDPs represents less than 0.2 per cent of traditional petrochemical-based plastic. Despite their environmental benefits, the costs of BDPs are higher than conventional plastics at about 2-5 Euro per kg. Conventional plastics cost approximately 1.2 Euro per kg.

The study also examines waste management options for BDPs. In terms of recycling, BDPs may cause complications in existing plastic recycling systems because of their different properties. If incinerated, the bio-based BDPs could be considered as a form of renewable energy, but there is a lack of data on the actual heat energy produced by BDPs.

If BDPs degrade under anaerobic (airless) conditions in landfills, methane will be produced - a powerful greenhouse gas. European policy is trying to reduce the negative effects of landfill waste on the environment so disposal of BDPs in landfill should be kept to a minimum.

Unlike conventional plastics, the majority of BDPs can be composted which could divert waste from municipal collection systems. However, some BDPs suitable for industrial composting are not suitable for home composting because a high temperature period is needed to start the degradation.

The study cites a research project that classifies BDPs into fast, medium and slow degraders in terms of how much mass they lose after 90 days of home composting. The fast degraders are predominately made from high levels of starch, the medium are based on wood or coconut fibres and the slow degraders tend to be PLA or polypropenes with additives. The authors suggest that it would be necessary to distinguish between different BDPs for successful home composting. Labelling schemes could provide useful guidance for the public.

Original Source: Song, J.H., Murphy, R.J., Narayan, R. & Davies, G.B.H. (2009) Biodegradable and compostable alternatives to conventional plastics. Philosophical Transactions of the Royal Society B. 364: 2127-2139

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