There is broad consensus about the importance of moving from linear to more circular food systems. But can we find good indicators to measure the effect of this? In a new article NORSUS researcher Hanne Møller and colleagues discuss circularity indicators using examples of environmental actions in pig production and testing various circularity indicators in comparison with LCA results.
The following measures were assessed: Treatment of livestock manure in biogas plants and use of digestate as fertiliser, biogas treatment of bread waste and use of digestate as fertiliser, precision fertilization, use of cover crops in feed production, and use of bread waste as pig feed. The functional unit was 1 kg carcass weight of pork, and treatment of 1.1 kg of bread waste. Based on this, the functionality and suitability of these circularity indicators were discussed.
Four of the circularity indicators were based on nitrogen (N) or phosphorus (P): N recycling index, partial N balance, consumption of fossil P fertilizers and emissions of P to water. Although the indicators do not show the effect of emissions of N and P in the form of eutrophication, they provide a useful indication of the circularity of agricultural production.
The three other circularity indicators that were tested were production of renewable energy, soil organic carbon and land use ratio. The renewable energy production indicator is easy to understand and communicate and provides unique information. Soil organic carbon is closely linked to greenhouse gas emissions because carbon sequestration in the soil captures CO2 from the atmosphere. However, this indicator must be reported separately from greenhouse gas emissions because there is still no agreement on methodology and to show the difference between actual emissions and carbon storage that may not be permanent.
The land use ratio is an indicator that measures the efficiency of land use in livestock production. The indicator is based on the same data as land use but includes the amount of plant protein from the area for feed to produce 1 kg of digestible animal protein. The indicator thus provides an assessment of whether the area for fodder production would have yielded more protein if it had been used for the cultivation of food crops directly.
Circularity indicators provide valuable information about the circularity of an agricultural product system and can be used either separately or together with LCA impact categories. Which indicators should be chosen depends on the questions being asked, i.e. goals and scope, and it is therefore important to have a number of circular indicators to choose from in order to achieve a holistic assessment.
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