Life cycle assessments of arable land use options and protein feeds : A comparative study investigating the climate impact from different scenarios in the agricultural sector

Abstract: The aim of this study was to investigate and compare the climate impact from different arable land use options and protein feeds aimed for cattle. This has been made by executing two life cycle assessments (LCAs). The first LCA aimed to compare the following three arable land use options: Cultivation of wheat used for production of bioethanol, carbon dioxide and DDGS Cultivation of rapeseed used for production of RME, rapeseed meal and glycerine Fallow in the form of long-term grassland The second LCA aimed to compare the three protein feeds DDGS, rapeseed meal and soybean meal. In the LCA of arable land, the functional unit 1 ha arable land during one year was used and the LCA had a cradle-to-grave perspective. The LCA of protein feeds had the functional unit 100 kg digestible crude protein and had a cradle-to-gate perspective, hence the use and disposal phases of the feeds were excluded. Bioethanol, DDGS and carbon dioxide produced at Lantmännen Agroetanol, Norrköping, were investigated in this study. The production of RME, rapeseed meal and glycerine were considered to occur at a large-scale plant in Östergötland, but no site-specific data was used. Instead, general data of Swedish production was used in the assessment. The wheat and rapeseed cultivations were considered to take place at the same Swedish field as the fallow takes place. The protein feed DDGS was produced at Lantmännen Agroetanol and the rapeseed meal was assumed to be produced at a general large-scale plant in Sweden. In the soybean meal scenario, a general case for the Brazilian state Mato Grosso was assumed and no specific production site was investigated. Data required for the LCAs was retrieved from literature, the LCI database Ecoinvent and from Lantmännen Agroetanol. In the LCA of arable land use options, system expansion was used on all products produced to be able to compare the wheat and rapeseed scenarios with the fallow scenario. In the LCA of protein feeds, system expansion was used on co-products. The products in the arable land use options and the co-products in the protein feed scenarios are considered to replace the production and use of products on the market with the same function. The result shows that the best arable land use option from a climate change perspective is to cultivate wheat and produce bioethanol, carbon dioxide and DDGS. This is since wheat cultivation has a higher yield per hectare compared to rapeseed and therefore a bigger amount of fossil products and feed ingredients can be substituted. To have the arable land in fallow is the worst option from a climate change perspective, since no products are produced that can substitute alternative products. Furthermore, the result shows that DDGS and rapeseed meal are to prefer before soybean meal from a climate change perspective, since soybean meal has a higher climate impact than DDGS and rapeseed meal. This can be explained by the smaller share of co-products produced in the soybean meal scenario compared to the DDGS and rapeseed meal scenarios. Since the production and use of co-products leads to avoided greenhouse gas emissions (since they substitute alternatives), the amount of co-products being produced is an important factor. A sensitivity analysis was also executed testing different system boundaries and variables critical for the result in both LCAs. The conclusion of this study is that arable land should be used to cultivate wheat in order to reduce the total climate impact from arable land. Furthermore, it is favorable for the climate if DDGS or rapeseed meal are used as protein feeds instead of imported soybean meal.