Environmental life cycle assessment of organic pigs fed with grass protein

The most common protein source for organic pig production in Denmark are imported organic soy. Since feed production is a major hotspot in the climate impact of pig production, alternative local protein sources could be a climate mitigation option. One alternative protein source is “grass protein” that are based on grassland biomass and can be fed to monogastrics. Some of the benefits of the grass protein is that it is based on a local resource, which minimises the transport, and that is contributes to carbon sequestration and biodiversity, which is higher under grasslands. One of the disadvantages is that the wet biomass requires some energy for the processing and drying. The energy use for processing and transportation therefore affects the carbon footprint of the grass protein. Feeding the grass protein to organic pigs instead of organic soy might also affect the feed uptake and growth of the organic pigs, which in turn will affect the carbon footprint of the pig meat. The aim of the current paper is to investigate whether the carbon footprint will be improved by feeding grass protein to organic pigs and which factors that affects the results. The results showed that if the grass protein is based on unfertilized grass-clover, the fibre fraction is fed to cattle and the energy for the biorefining process is based on biogas from the brown juice, then feeding the pigs with 15% organic grass protein will lower the carbon footprint of the pigmeat compared to feeding with organic soy. However, the sensitivity analysis showed that the carbon footprint of the grass protein, and thus also the carbon footprint of the pigmeat, is highly dependent on the energy utilization in the biorefinery and the transport distances.