Removing too much crop waste for bioenergy could come at a cost to biodiversity, study finds

Crop residues – the stems, leaves and husks left behind after harvesting cereals – could provide an important source of renewable energy for Europe, but research led by the University of Surrey suggests that removing too much from fields could come at a cost to biodiversity. 

While some waste material from crops, such as wheat and maize, is already used for fuel and bioenergy, much of it is used as animal feed or bedding or is left on fields, where it helps maintain healthy soils and provides food and habitats for wildlife.  

As Europe looks to increase renewable energy production, researchers at Surrey worked with the Natural History Museum's Biodiversity Futures Lab and Utrecht University in the Netherlands to better understand how the amount of crop residues left on fields is linked to local biodiversity. 

In a study published in Agriculture, Ecosystems and Environment, the research team built statistical models to analyse biodiversity measurements from land uses across Europe, including fields growing cereals, alongside data on crop yields, residue management and environmental conditions. 

The findings showed that cereal-growing areas where at least 70 per cent of crop residues were left on fields generally had greater local biodiversity than areas where less was retained. The amount of residue left was also a stronger predictor of biodiversity than crop yields, highlighting the importance of how these materials are managed. 

Professor Zoe M Harris, Director of the Centre for Environment and Sustainability at the University of Surrey, said: 

"Crop residues could provide a valuable source of renewable energy for Europe’s green transition, but as with any natural resource, we need to fully understand what happens if we take more of these materials from fields. Our findings suggest that there could indeed be consequences for biodiversity, and that needs to be factored in when assessing how much crop residue can sustainably be used for bioenergy production." 

The study warns that increasing the removal of cereal residues could have negative consequences for biodiversity, particularly in areas where a high proportion is currently left on fields. However, it also highlights the possibility of making more residues available for bioenergy by reducing the amount used for animal feed and bedding, rather than removing more from fields. 

Lead author Dr Sophie Tudge, now a postdoctoral researcher at the University of Leeds, who carried out the research during her PhD at Surrey, said: 

"It’s not just about finding enough material to produce renewable energy, but working out where that material should come from. Rather than removing more crop residues from fields, we should also be looking at how they're used elsewhere, including in animal production. There may be opportunities to make more of this material available for bioenergy without putting additional pressure on farmland and the wildlife it supports." 

The study also points to the wider challenges of producing sustainable bioenergy, including the need to protect natural habitats from agricultural expansion. Further research into how removing crop residues directly affects biodiversity could help Europe balance its renewable energy ambitions with the protection of its ecosystems. 

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Notes to editors 

• Professor Harris and Dr Tudge are available for interview; please contact mediarelations@surrey.ac.uk to arrange. 

• The full paper can be found here: Associations between landscape-scale cereal residue management and local biodiversity in Europe - ScienceDirect