Vera et al.: Supply potential of lignocellulosic energy crops grown on marginal land and greenhouse gas footprint of advanced biofuels (2021)

Vera I., Hoefnagels R., Junginger M. & Van der Hilst F.: Supply potential of lignocellulosic energy crops grown on marginal land and greenhouse gas footprint of advanced biofuels— A spatially explicit assessment under the sustainability criteria of the Renewable Energy Directive Recast (2021)

The European Union (EU) has set ambitious greenhouse gas emission reductions to mitigate climate change impacts. Although there is still an ongoing debate about biomass for energy purposes, it is expected that biomass will contribute considerably to decarbonise the EU energy system.

There are still many sustainability concerns associated with large-scale biomass production for energy purposes. One relates to net carbon fluxes of land dedicated to biomass production: It is crucial for biomass production systems to avoid competition with other land-based services as food production and nature conservation. In that sense, marginal lands, which is land that has little or no agricutlural or industrial value, are interesting to dedicate these to grow sustainable biomass.

Generally, lignocellulosic energy crops have multiple advantages over food-based crops, for example related to less inputs (e.g. fertilisers) and high yields in less suitable conditions. Accordingly, advanced biofuels produced from lignocellulosic crops grown on marginal lands can become  an  important  part  of  the  European  Union  (EU)  climate  change  mitigation  strategy  to  reduce  CO2  emissions  and  meet  biofuel  demand.  

This study therefore quantifies spatially explicit the availability of marginal land in the EU, its production biomass potentials for eight different crops, and the greenhouse gas (GHG) performance of advanced biofuel supply chains. This is done for 2040, 2040 and 2050, but the GHG balance is only limited for 2030. The following lignocellulosic energy crops are analysed: Miscanthus, switchgrass, giant reed, reed canary grass, cardoon, poplar, willow and eucalyptus. Eight advanced biofuel pathways to produce ethanol, renewable jet fuel, gasoline, diesel, methanol and DME are considered.

Below, the approach and findings are summarised.

Available land

• Available land is mapped based on land marginality and Renewable Energy Directive Recast (REDII) land-related sustainability criteria.
• Available marginal land that meets REDII criteria is projected at 20.5–21 Mha in 2030 and 2050, respectively. Due to biophysical limitations, not all available land is suitable for energy crop production.

Biomass potentials

• Biomass potentials are assessed with a water-use-to-biomass-production  approach while considering the available land, location-specific biophysical  conditions and crop-specific phenological characteristics.  
• The maximum biomass potential of lignocellulosic energy crops (optimal  crop  choice with maximum yield for each available location) varies between 1951 PJ per year in 2030 and 2265 PJ per year in 2050.

GHG balance   

• The GHG balance of advanced biofuels from energy crops produced on marginal  lands is assessed considering both land-related carbon stock changes and supply chain emissions with the carbon footprint approach from the REDII.
• The GHG emission performance (net emissions) of different advanced biofuel supply chains varies on average between −32 g CO2eq/MJ for poplar/willow diesel to 38 g CO2eq/MJ for reed canary grass renewable jet fuel. The large variability in GHG performance is strongly determined by the spatial heterogeneity, which dictates the type of feedstock produced under specific local biophysical conditions, the crop characteristics, and the best conversion pathway. Negative GHG emissions are related to increased carbon stocks for the biomass and soil organic carbon pools compared to the land prior to conversion. When for each location, the advanced biofuel supply chain with the highest GHG  performance (lowest  net  GHG  emissions) is selected, 618 PJ  pear year of  advanced biofuels can be produced by 2030. Under REDII GHG emission criteria,  slightly less (552 PJ per year) is viable.  

The article concludes that, indeed, the production of advanced biofuels from marginal land sourced energy crops can rise a valuable EU climate change mitigation strategy to reduce CO2 emissions and support to meet EU biofuel demand. Smart choices on  location, crop type and supply chain design are paramount to achieve  maximum  benefits of bioenergy systems.