Resource usage of integrated Pig–Biogas–Fish system: Partitioningand substitution within attributional life cycle assessment

Abstract

The integration of agriculture and aquaculture with anaerobic digestion is a popular practice at small Asian farms as a way of producing energy and fish, i.e. providing a better nutrient balance and resourcerecycling. Concerns are raised whether the resource efficiency of such system is better or worse relative tothe monoculture system. In this study, we focused on quantifying the resource demand of two integratedPig–Biogas–Fish farms in Vietnam. The analysis was performed by using the exergy concept: exergy flowanalysis (ExFA) at process level and Cumulative Exergy Extraction from Natural Environment (CEENE) atlife cycle level.Results showed that such integrated systems considerably relied on land (68% farm A and 54% farm B,mainly for pig feed production) and water (28% farm A and 42% farm B, mainly for aquaculture). It can alsobe concluded that the intensive aquaculture practice had a higher feed input than the semi-intensive oneintegrated with pig and biogas production; however, the latter system had a higher CEENE value to delivera similar mass (i.e. one kilogram) of product at farm gate. This is mainly caused by a dramatically low arealyield of the integrated aquaculture, corresponding to an inefficient water use (16 m3kg−1fingerlings and10 m3kg−1fish) therefore identified as the resource hotspot.Improvements could be achieved through a better water management in aquaculture and an increasedbiogas utilization, preventing any leakages. Fertilizing the fish pond with manure-based digestate insteadof fresh manure and/or rising the application rate might be a more efficient way to reduce pelleted fishfeed consumption, although further research on such options are needed.