Rice-crayfish coculture delivers more nutrition at a lower environmental cost

A growing demand for food products from limited arable land has meant that paddy fields have been developed to provide both grain and aquatic products. China has the world's largest aquaculture area of crayfish, of which ∼86% is in the form of rice-crayfish coculture. Here, we use a life cycle assessment to evaluate and compare the environmental impacts of three farming systems: rice monoculture, crayfish monoculture, and rice-crayfish coculture. Two functional units were used: one hectare of land occupied, and one Nutrient Density Unit (NDU) – i.e., the combined nutrition delivered in rice and/or crayfish products. Rice-crayfish coculture has a larger environmental footprint than rice monoculture per hectare occupied across at least 7 of the 8 impact categories studied, though performs better than crayfish monoculture. However, rice-crayfish coculture yields 1.12 to 2.21 times more nutrition per hectare than rice monoculture and crayfish monoculture, respectively. Hence, rice-crayfish coculture was found to have lower impact per NDU across all 8 impact categories studied, compared with the monoculture systems. Application of urea, crayfish feed inputs, and electricity consumption dominated most environmental burdens for rice-crayfish coculture, while field emissions (e.g., CH₄ and NH₃) strongly influenced global warming potential, terrestrial acidification potential and freshwater eutrophication potential, respectively. Environmental burdens of rice-crayfish coculture could be further reduced by increasing productivity per hectare and/or improving fertilizer and feed use efficiency. Shifting from rice- and crayfish-monoculture to rice-crayfish coculture could deliver more nutrition at a lower environmental cost, as well as increasing farm profitability by 7−462%.