Targeted grassland production – A Danish case study on multiple benefits from converting cereal to grasslands for green biorefinery

Abstract

Current research on, e.g. agricultural supply-chains, engages in implementing new technologies enabling extraction of protein from other sources than soya such as grass, clover, or alfalfa. Still, it is not obvious where to initiate production of the biorefinery crop without damaging existing ecological systems or maybe even to strengthen local environments.This paper uses a targeted approach to identify the most suitable agricultural areas to convert from cereal to grassland production while gaining multiple environmental benefits. For the Danish region, three individual biomass goals were set: 1) reach 3 × 106 t dry matter from organically produced non-fertilized grass-clover mixtures, and 2) reach 5 × 106 t dry matter from grass fertilized with 300 kg N/ha, or 3) 450 kg N/ha. Areas for conversion were selected based on coastal nitrogen (N) loads and a surrounding nature index in a stepwise manor until the three biomass goals were reached separately.Our results reveal a spatial distribution of some of the areas selected for conversion close to existing nature areas and vulnerable aquatic environments for all goals. Producing 5 × 106 t dry matter fertilizing grass with 450 kg N/ha requires less agricultural area (23% of total agricultural area) compared to fertilizing with 300 kg N/ha (28%) and even less than producing only 3 × 106 t dry matter without fertilizing (24% of total agricultural land). Despite less land area, goal 3 still has a higher coastal N load compared to goal 2, and consequently goal 2 reaches 50–60% of the national N reduction goal to reduce 13,000 t N compared to 21–28% for goal 3. Furthermore, surrounding nature shows a higher index value for goal 2 compared to goal 3. Hence, in our case goal 3 would be preferable if land scarcity was the heaviest weighing factor. Still, the environmental gain resulting from using goal 1 and 2 would increase potential multifunctionality of converting from cereal to grass production.