Biofuels made from vegetable oils are as bad as fossil fuels when it comes to carbon emissions, a study says.
Researchers at Leicester University have found that emissions associated with palm oil plantations are 50 per cent worse than previously thought because the land releases carbon that was trapped in peat for thousands or even millions of years.
Producing biofuels from other vegetable oils such as rapeseed and soya also has high associated emissions because using them for fuel indirectly leads to an increase in palm oil farming to meet demand for cooking oil.
‘A tropical forest contains a lot of carbon in its biomass, and to grow the oil palm you need to chop the forest down and replace it with something that stores less carbon,’ Ross Morrison, one of the study’s authors, told The Engineer.
‘So there’s a loss of carbon when you deforest but the largest loss is from the old carbon being released. The only reason the peat is stable is because it’s waterlogged all the time. Once you drain it you allow oxygen into the peat and this causes very rapid microbial decomposition and that releases CO2.’
Biofuels are typically thought of as having low net greenhouse gas emissions because when they are burnt they release carbon dioxide only recently captured from the atmosphere. Previous estimates put their associated emissions at 50 tonnes of CO2 per hectare per year.
But by taking into account the carbon released from the drained peat and the resulting loss of the land as a carbon sink, the researchers concluded that 86 tonnes was a more accurate figure. Using the EU Renewable Energy Directive to assess emissions over a shorter-term period (20 years), this figure rises to 106 tonnes.
‘This research shows that estimates of emissions have been drawn from a very limited number of scientific studies, most of which have underestimated the actual scale of emissions from oil palm,’ Morrison said in a statement.
‘These results show that biofuels causing any significant expansion of palm on tropical peat will actually increase emissions relative to petroleum fuels. When produced in this way, biofuels do not represent a sustainable fuel source.’
Dr Sue Page, Leicester’s head of the physical geography department, said: ‘Projections indicate an increase in oil palm plantations on peat to a total area of 2.5Mha by the year 2020 in western Indonesia alone — an area equivalent in size to the land area of the United Kingdom.’
If these improved estimates are applied to recent International Food Policy Research Institute modelling of the European biofuel market they imply that, on average, biofuels in Europe will be as carbon intensive as petrol and worse than fossil diesel.
Bioethanol or biodiesel from waste cooking oil, on the other hand, could still offer carbon savings.
This outcome has important implications for European Union policies on climate and renewable energy sources, said the researchers.
‘It is important that the full greenhouse gas emissions “cost” of biofuel production is made clear to the consumer, who may otherwise be misled into thinking that all biofuels have a positive environmental impact,’ said Page.
‘In addition to the high greenhouse gas emissions associated with oil palm plantations on tropical peatlands, these agro-systems have also been implicated in loss of primary rainforest and associated biodiversity, including rare and endangered species such as the orang-utan and Sumatran tiger.’
The research was commissioned and funded by the International Council on Clean Transportation (ICCT), an international think-tank made up of representatives from the world’s leading vehicle manufacturing nations.