Improving carbon footprint calculations of agricultural products

Life cycle assessment and product carbon footprints are well established tools which assist the process of improving environmental performance. However, there is room for methodological improvement. New methods tested in a recent study allow the inclusion of crop rotation effects and crop residues as co-products to achieve more accurate results.

Image credit: Carl Wycoff, flickr/Creative Commons

If rape, barley and other crops alternate on farm fields during the growing season, soil quality improves. For centuries, farmers have used the so-called “crop rotation” to maintain soil fertility. But the carbon footprint of bread, milk and biofuels will also be affected. Scientists at the Technical University (TU) Berlin have developed new methods for life cycle assessment. The researchers are first in demonstrating that crop rotations and straw harvest should be considered for the product carbon footprints of bread, milk, and first- and second-generation biofuels.

Both crop rotations and crop residues such as straw were examined and evaluated. “For the first time, we can now calculate product-related carbon footprints of agricultural produce grown in crop rotation systems,” explains Dr. Gerhard Brankatschk, who works at the Institute for Technical Environmental Protection of the TU Berlin in the Department of Sustainable Engineering, and has focused on new methods for the life cycle assessment of agricultural products. He points out that the calculation method also complies with the international standards for life cycle assessment (ISO 14040/14044).

In a study over several years, the life cycle assessment of various products, including the crop rotation or the by-product straw, were recalculated and compared with previous results. Bread from wheat, milk from cows, biodiesel from rapeseed and straw bioethanol were considered. Cultivation in crop rotations, it turned out, improves the product carbon footprints of bread, milk and biodiesel by 11 percent, 22 percent and 16 percent, respectively. However, the product carbon footprint of straw bioethanol increases by 80 percent when considering straw as an agricultural co-product (which is relevant for livestock farming and soil fertility) instead of as waste.

Meaningful instrument for sustainability assessment

“We therefore recommend adjustments to the current accounting practice and individual legal requirements,” explains the researcher, “including the European Renewable Energy Directive, which is currently being revised.” The study was published in December 2017 in the journal Agronomy for Sustainable Development. “With the internationally acknowledged instrument ‘Life Cycle Assessment’, not only agriculture, but also politics and the economy will have access to a meaningful and attractive tool for life-cycle-based sustainability assessment”, says Professor Matthias Finkbeiner, also of the TU Berlin. “It also helps to evaluate the environmental effects of agricultural technology options such as the inclusion of nitrogen-fixing legumes in the crop rotation.” Gerhard Brankatschk adds another advantage: “Our calculations also take into account the nutritional value of livestock and thus include the two ambitious UN sustainability goals of food security and combating climate change. “

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