Grønt protein fra eng – biorafinering, bærekraft og systemperspektiv

Green biorefining is a technology in which forage crops are processed to extract protein along with other valuable co-products. Nordic research shows that, with ongoing developments, this technology holds great potential to increase self-sufficiency and reduce the environmental burden from the production of protein feed ingredients. In the green biorefining process, mechanical pressing is used to separate the green biomass into two fractions: fiber-rich pulp and green juice. The green juice is further processed, usually through precipitation, to obtain a protein concentrate. This protein concentrate can be used as feed for monogastric animals such as pigs and poultry. The pulp from the first step can be used as feed for ruminants such as cattle, while the remaining brown juice from the precipitation step can be used as fertilizer or as a raw material for biogas production. The aim of our project is to assess the environmental impacts of green biorefining in Norway and to conduct a system analysis to strengthen knowledge about sustainable implementation. In our first published study, we analyzed how different nitrogen fertilization levels and biomass treatments affect climate impact and land use of the green biorefinery process. The results showed that for all levels (0–240 kg N/ha), and for both fresh and ensiled biomass, emissions were lower than those of the avoided products (including soy). When 1 ton of dry matter biomass at harvest was processed in a green biorefinery, the system resulted in a net negative climate impact. The inclusion of clover contributed to high yields, reduced the need for mineral fertilizer and thereby emissions at lower fertilization levels, but at the same time led to somewhat higher land use. Biomass cultivation was the largest source of emissions in a life cycle perspective, with nitrogen fertilization as the decisive factor due to nitrous oxide emissions. We are currently working on a study of dairy production where pulp from green biorefining is included in the feeding strategy. Previous studies have shown varying effects on production, feed efficiency, methane emissions, and nutrient balances, highlighting the need for a systems perspective. In our analysis, we compare a reference system with two alternative systems in which pulp is included in the ration. Preliminary results indicate that the use of pulp has the potential to reduce greenhouse gas emissions from milk production.