Local non-food yeast protein in pig production–environmental impacts and land use efficiency

Abstract

The aim of this study was to analyse the sustainability of pig production based on a diet containing yeast as a protein source. The yeast is produced from sugar, and the sugar can be produced from hydrolysed wood through a biorefinery process. This study included yeast from two different biorefinery processes: 1) a domestic demo plant in connection with a complex biorefinery, and 2) a small-scale wood refinery process largely based on wood residues. In the yeast diets, the yeast replaced soybean meal as a protein source and the two yeast diets were compared with a standard diet. The environmental impacts from the pig production systems were assessed by using life cycle assessment (LCA), and the functional unit was 1 kg carcass weight of pork at the farm gate.The results from the study show that yeast replacing imported feed protein sources used in pig production gives a lower impact for biodiversity loss and climate change including land use change . The lower impact was created by the replacement of soybean meal with yeast from wood sugar in the feed recipe. Also, the scenarios with yeast diets gave a land use ratio below 1, indicating an improved land use efficiency regarding producing human digestible protein. Even though the forest land used for deriving wood sugar constitutes a greater area than the corresponding area for soybean meal production, the forest land does not occupy areas suitable for food production. The reference case, representing current pig production and feeding system, had a land use ratio of 1.15, meaning that the feed production was directly competing for the area suitable for food production.The overall conclusion was that the utilisation of yeast from wood sugar appears to avoid feed-food competition and at the same time to be an environmentally sustainable solution for future feed protein employed in pig production.