Converting waste such as paper and cardboard into biofuel is a neglected option that could provide clean energy, cut the amount of municipal waste and reduce greenhouse gas emissions, researchers say.
Around 83 billion litres of ethanol could be produced from waste paper, according to their model. This could replace five per cent of the world's global petrol demand.
Moreover, ethanol produced this way would emit fewer greenhouse gases than the same amount of petrol — although this reduction could be anywhere from 29 to 86 per cent.
Researchers from the National University of Singapore created a model to assessed the amount of wastepaper and cardboard generated in 170 countries, incorporating data from 70 countries — which they then extrapolated to the further 100 countries using information about their socioeconomic development.
They also calculated the petrol consumption of these countries using EarthTrends — an online environmental information database.
By combining these calculations, they established a global figure for the amount of ethanol that could be yielded from wastepaper. Their results were published online in Global Change Biology: Bioenergy last month (22 September).
Narasinha Shurpali, an environmental science researcher at the University of Kuopio in Finland, believes the idea could work for developed countries that would find it particularly easy to adapt their waste disposal systems — paper waste would simply be transported to biofuel processing units instead of landfills. But it could be a challenge for developing countries.
Driss Zejli, head of the Renewable Energy Economy and Technologies Unit at Morocco's National Centre for Scientific and Technological Research, is less convinced by the model.
"It ignores critical factors such as the variable waste levels of each country," he told SciDev.Net. "Though it's important to treat waste for environmental, health and agricultural purposes, we should look to serious sources for energy."
Ahmad Houri, a renewable energy expert at the Lebanese American University in Beirut, does not think it would be cost-effective to produce ethanol from cellulose. Also, there would be negative knock-on effects for recycling.
"Paper and organic matter would be used up [by the production of biofuel] so the recycling opportunities for these two would be lost. This cost has to be weighed against the generated income," he said.
Link to abstract in Global Change Biology: Bioenergy