An ethanol plant in the USA and a large pile of corn, which is burnt to create biofuel (image: JMichl/iStock).

Renewable energy sources such as biofuels are being criticised for releasing more greenhouse gases than previously expected.

Several recent studies on corn ethanol (a type of biofuel) indicate that it is responsible for releasing more CO₂ into the atmosphere than fossil fuels.

This is largely due to the effort needed to grow the crops, and agricultural land being converted, or forests destroyed to free up the land.

In addition, growing the crops needed for biofuel can lead to increased stress on water supplies and push up corn prices as a result of increased demand for the crop.

‘The University of Michigan Energy Institute’s research was based on US Department of Agriculture crop-production data which showed that during a period when US biofuel production was amplified, the increased carbon dioxide uptake by the crops was only enough to offset 37% of the CO₂ emissions due to biofuel combustion.

According to research professor John DeCicco, “When you look at what’s happening on the land, you find that not enough carbon is being removed from the atmosphere to balance what’s coming out of the tailpipe”.

However, corn ethanol is a first generation biofuel. We also have second generation biofuels, which instead of being made from corn or sugar cane, are made from trees and plants. The two are related, but not the same.

Second generation biofuels are less carbon intensive than first generation or fossil fuels, and they avoid land-use changes.

“Second generation biofuels will take trees, say pine trees, and make biofuels from them. The CO₂ savings are higher and the land use changes are not a problem anymore. It removes the ‘food vs fuel’ debate from biofuels,” says Dr Jason Hallet, a researcher in bio-renewables and biofuels at Imperial College London.

It is more important than ever that we work towards reducing the human effect on climate change, we need to make sure that future fuel sources are a help not a hindrance.