What is the best cereal cropping system if you look at the big picture and take into account the impacts on global warming, eutrophication, land use in a global perspective, and arable land quality?

Working with Aarhus University and the University of Copenhagen, biotech company Novozymes used life cycle analyses to estimate the most environmentally friendly cropping system for Denmark.

Scientists analysed six different cereal cropping systems that included spring barley or winter wheat, various sowing times, various uses of catch crops or intercrops, and various ways of dealing with the straw. They found that early sown winter wheat, where the straw is removed every second year and used in biorefining, is the best of six different cereal cropping systems with regard to total environmental impact.

In the analysis, the scientists took various factors into account, including grain yield, straw yield, soil carbon storage, greenhouse gas emissions, arable land use, and loss of nutrients to the environment. A central element in the analyses was the use of the cereal straw, i.e. to which extent the straw was incorporated into the soil or used in a biorefinery for production of bioethanol, biogas, and bioelectricity.

The system with early sowing of winter wheat and export of straw every second year came out best with regard to both greenhouse gas emissions and nutrient losses to the environment.

This is partly because early sown winter wheat has better grain and straw yields compared to spring barley and winter wheat sowed at the normal time. As part of their estimates, the researchers said reduced yields from crops would result in increased crop production elsewhere, which would take up more arable land, and considered using straw to replace gasoline, natural gas, and electricity as an environmental benefit.

The analyses demonstrate the importance of taking a bird's eye view when evaluating the total environmental consequences of cereal production. The scientists behind the study recommend that crop production be viewed in a full life cycle perspective. The differences in yield between the various cropping systems can have great impact on their individual environmental profiles and the use of straw in biorefinery can improve the environmental profile significantly.