Assessing the environmental performance of biomass supply chains: Methods, results, challenges and limitations

The on-going public debate on sustainability of bioenergy began in 2007 and 2008 after a couple of papers were published questioning the reported N2O emissions caused by cultivation of agricultural crops (Crutzen et al., 2007) and the carbon neutrality of biomass use (Searchinger et al., 2008) due to direct and indirect land use change as well as change of carbon stocks. Since these initial papers, many others have been published mainly questioning the positive climate impact of bioenergy. The impact of these papers changed the attitude towards use of bioenergy in the public and political arena. The European Commission, for example, released the Renewable Energies Directive 2009/28/EC (European Parliament, 2009) with sustainability criteria for liquid biofuels, prohibiting the marketing of liquid biofuels that exceed predefined carbon emission saving thresholds and that originate from certain types of ecosystem. Criteria for solid biofuels are currently under development. It is important to mention that these sustainability criteria are valid for biofuel imports into the European Union (EU) as well as for biofuels produced within the EU. Hence, the directive has a global impact.