Algae certainly look green (Image: Ashley Cooper/Alamy)

ALGAE have been touted as a solution to environmental worries over biofuels, but they may be a long way from providing a truly green option.

Unlike maize, soya beans and oilseed rape (canola), algal farms don’t take up valuable farmland, so algae-based biofuels don’t threaten food supplies. However, Andres Clarens at the University of Virginia in Charlottesville has modelled the environmental impacts of algal farms and concludes that they require six times as much energy as growing land plants – and emit significantly more greenhouse gases (Environmental Science and Technology, DOI: 10.1021/es902838n).

“You have to add a whole lot …