All bioenergy options are not created equal

Researchers from Bangor University in the UK and the Thünen Institute in Germany have evaluated various bioenergy options offered as alternatives to greenhouse gas-emitting fossil fuels and found that some options are far better for the environment than others.

The team stated that measures such as bio-electricity feed-in-tariffs (FiTs) and renewable heat incentives (RHIs) are driving the production of biofuels from food crops. But there is concern that these policy measures do not target the most sustainable bioenergy options to reduce dependence on fossil fuels and reduce greenhouse gas (GHG) emissions. The researchers therefore decided to assess the environmental performance of several bioenergy options introduced into a typical arable farm rotation:

• Electricity and heat production from on-farm biogas plants fed by maize, grass, pig manure or food waste;
• Bioethanol and biodiesel production from wheat and oil seed rape, respectively; and
• Heat production from Miscanthus (woody grass) pellets.

While all options were found to conserve fossil fuels, the team concluded that biogas and liquid biofuels are at best inefficient options for greenhouse gas mitigation, based on the hectares of land used and the amount of public subsidy required. At worst, these options could actually lead to higher global GHG emissions owing to indirect land use change caused by displacement of food production. In comparison, waste-biogas and Miscanthus heating pellets achieve at least 10 times more GHG mitigation per tonne of dry matter biomass and per hectare of land used, respectively.

Writing in the journal Global Change Biology Bioenergy, the researchers noted that FiT payments are currently “not dependent on compliance with sustainability criteria”. Yet study leader Dr David Styles, from Bangor’s School of Environment, Natural Resources & Geography, said, “Whilst subsidies are necessary to correct for market failure and develop vital renewable energy sources, it would seem sensible to link such subsidies with environmental sustainability criteria to ensure that they efficiently contribute to overall net public good.”

The researchers concluded that consequential life cycle assessment and ecosystem services effects “should be integrated into sustainability criteria for FiTs and RHIs, to direct public money towards resource-efficient renewable energy options that achieve genuine climate protection without degrading soil, air or water quality”.