Science - June 11, 2009

GREEN WITH A TOUCH OF GREY

Biodegradable plastics based on renewable resources are environmentally friendly because they can be produced with less energy and lower CO2 emissions. Yet the cultivation of crops for bioplastics can compete with food production and lead to deforestation. So how green are bioplastics really?

The development of biodegradable plastics made from renewable natural resources such as corn starch and cane sugar is really taking off. Unlike finite resources such as crude oil, these crops can be produced again and again. A few food products are sold nowadays in transparent compostable plastic boxes, and compostable plastic shopping bags are available. The rise of ‘green’ plastic seems irresistible.

But ‘biodegradable’ and ‘organic’ do not necessarily mean environmentally friendly. One serious downside of bioplastics can be that they are made from agricultural products that can compete with food crops for water and space. Greenpeace worker Andre van der Vlucht says sugar cane and maize, which are used to make bioplastics based on polylactic acid (PLA) are the real problem crops. ‘As soon as you start growing these sorts of crops for bioplastic or biofuels, it will be at the expense of food crops’, he says. ‘This has to be compensated for elsewhere in the world. Indirectly, this can lead to environmental damage.’ PLA is often produced from genetically modified maize from the US. The increased demand for this maize has led to decreased soya production in the US, says a report from the American Department of Agriculture. As a result, soya production has partially shifted to Brazil, leading to land use change that can harm rain forests and other ecologically important ecosystems, according to the respected journal Science.

Karin Molenveld of the Agrotechnology and Food Sciences Group (ASFG) puts this criticism in perspective: ‘An increase in meat consumption can have a much bigger impact on deforestation than the production of bioplastics, in spite of the rising demand’. And in future production, more use will be made of waste materials. This should cut the risk of environmental problems.

AFSG colleague Gerald Schennink thinks the problems can be resolved within the EU. ‘If we start growing maize on fallow agricultural land in the EU we’ll have enough raw material to meet the demand for bioplastics’, he claims.

Lot Folgering, press officer for the Worldwide Fund for Nature (WNF) stresses that there are no statistics yet on how bioplastics affect deforestation, but this could soon change, she thinks. ‘Rising demand for agricultural land is a central problem in the very complex issue of deforestation’, she says. ‘Which crop ends up replacing the forests depends on the market price. It could be sugar cane for bioplastics, but it might equally well be soya for cattle feed.’ For Alois Clemens of WNF’s Forest programme, the best hope for a solution lies in a broad global approach which assesses the total land area needed for various products: land management on a global scale, keeping the most precious ecosystems out of the line of fire.

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