SLU news

Feed production is the key to climate impact of dairy cows

Published: 01 July 2014

Dairy cows have been an important engine in Swedish agriculture, but currently the cows receive criticism for their contribution to global warming. But their unique abilities to convert pasture plants to high-quality protein and to produce manure to fertilize our crops have been neglected. Maria Henriksson shows in her thesis, that dairy farmers have greater opportunities to reduce climate emissions from the feed production, than trying to affect emissions from the stomachs of cows.

Maria Henriksson from SLU has in her doctoral work used life cycle analysis (LCA) to describe how the different stages of the production chain on a dairy farm affect the climate. According to these estimates, the greenhouse gas emissions vary significantly from farm to farm, suggesting that there are opportunities to reduce the emissions.

The feed accounts for more than eighty percent
Over 80 percent of the emissions were found to be caused by the animals' digestion and the production of feed, which means that the animals' intake of feed plays a crucial role. When Maria Henriksson investigated how different diets can influence the carbon footprint of the milk, it was found that the differences primarily are a function of how the feed is produced. Methane emissions from digestion were certainly large, but they did not vary much with different types of diets.

Effective use of farm resources
The general measures to reduce greenhouse gas emissions on dairy farms is primarily about making use of existing resources such as animal manure, feed and land as efficiently as possible. The diet composition should be evaluated at the farm level, since regional conditions for feed production influence the effect of different feeding strategies.

– More than half of the greenhouse gas emissions from feed production comes from roughage production, so it is very important how this feed is produced and how much that goes wasted, says Maria Henriksson.

Difficult to calculate climate impact of agricultural products
Unlike energy, industry and transport sectors, where carbon dioxide emissions dominate, emissions from agricultural production only to a small portion consist of fossil carbon dioxide. The large proportion, about 80 percent of the climate impact from Swedish milk production is related to biological processes that are difficult to predict and counteract, namely the emission of methane during rumination and nitrous oxide in the feed production. This means that estimates on the climate impact of agricultural products are associated with relatively large uncertainties and may therefore only be compared if they have been calculated with similar methods.