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

Introduction

The last three decades have been the warmest of the last 1400 years in the northern hemisphere. Human influence on the climate is clear and the on-going climate changes have had widespread impacts on the environment and the economy (IPCC, 2015). Agricultural activities are estimated to be responsible for one-third of climate change, partly because of deforestation and the use of fertilisers (Climate Institute, n.d.). The beef production is also a major contributor to climate change, and the beef consumption worldwide is increasing, raising the demand for animal feed (Dalgaard, et al., 2008). One of the reasons why the beef production has such a large environmental impact is the large area of arable land required in order to grow animal feed (Larsson, 2015). The population growth and the climate change will probably lead to a decrease in available arable land in parts of the world (Zhang & Cai, 2011), which means it is more important than ever to use the arable land existing today in the best possible way from a climate change perspective.

Biofuels, such as bioethanol and rape methyl ester (RME), are produced with the hope to reduce greenhouse gas emissions from a life cycle perspective, since biofuels can replace fossil fuels in the transportation sector. As the availability of arable land is limited, the greenhouse gas reduction per hectare of land and year is an important measure of sustainability when producing biofuels (Börjesson, et al., 2013). Lately, using arable land for biofuel production has been criticized for competing with food production and leading to indirect land use changes, i.e. the production of biofuels in Europe leading to changed land use and greenhouse gas emissions somewhere else in the world. At the same time, a significant part of the European arable land is used as fallow (Eriksson, 2013), land that could have been used to produce food or biofuels. These aspects opens up for a discussion – how should the arable land be used to contribute as little as possible to climate change?

When producing bioethanol from wheat and RME from rapeseed, the co-products Dried Distillers Grain with Solubles (DDGS) and rapeseed meal are also produced. These co-products can be used as protein sources in animal feed and substitute imported soybean meal, which means less land is required to grow soybeans (Börjesson, et al., 2010). However, different protein feeds have different protein content, and soybean meal contains more protein than DDGS and rapeseed meal which means a smaller amount of soybean meal is required to provide the animals with their daily protein intake compared to the two other protein feeds (Bernesson & Strid, 2011). The question remains which of the three protein feeds that contributes the least to climate change.

Aim and method

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.

Results and conclusion

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.

What is this?

This summary is an extended abstract for a Master of Science in Energy Environment Management thesis performed at Linköping University, the Department of Management and Engineering, written by Malin Karlsson and Linnea Sund.
 
The thesis has been supervised by f3 partner Lantmännen Agroetanol. The full text can be found in the f3 library of external resources.
 
References in summary
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