Multilevel environmental assessment of the anaerobic treatment of dairy processing effluents in the context of circular economy

Abstract

The capability of Anaerobic Digestion (AD) in minimising waste and retaining the value of materials and energy within the biological and technical cycles in the Dairy Industry (DI) makes AD a critical instrument of transition to circular economy. The aim of this paper is to propose an approach for measuring the environmental performance of the anaerobic treatment of dairy processing effluents based on the circular economy principles. The potential of AD to close the water, energy and nutrient circular loops is investigated together with the relevant environmental costs and benefits at different levels of the dairy supply chain. The developed methodology was based on Material Flow Analysis (MFA) and Life Cycle Assessment (LCA) applied at three different system levels: the AD plant, the dairy processing facility, the entire dairy supply chain. The approach is demonstrated in a dairy facility coupled with a full-scale AD unit. The results show that the excess electricity (426 MWh/annum) and heat (1236 MWh/annum) produced from the AD plant cause significant reduction of the overall environmental impact of the processing facility. The recovered energy from AD provides 20% of the energy requirements of the factory reducing the total carbon footprint emissions by 13% compared to the baseline scenario.