Evaluation of environmental and economic implications of a cold-weather aquaponic food production system using life cycle assessment and economic analysis

Aquaponics, in which fish and plants are grown in a symbiotic closed-loop industrial metabolism, are promising test beds to implement industrial ecology in food production at a commercial scale. These systems have the potential to enhance the environmental and economic performance of aquaculture systems by reducing the overall burden on natural ecosystems (i.e., reducing resource and emission-based impacts per unit of food produced). To holistically evaluate the environmental and economic implications of aquaponics, specifically in a cold-weather climate, Life Cycle Assessment (LCA) and Economic Analysis (EA) were performed on a Midwestern United States aquaponic system, using data from 3 years of annual operation cycles with varying fish species production; tilapia, conventional walleye, and hybrid walleye. For the LCA, environmental impacts were quantified using 10 midpoint indicators. Assessments indicated that 1-kg production of live-weight tilapia, conventional walleye, and hybrid walleye resulted in 20.2-13.8-11.7 kg CO2-eq, 23.0-7.8-3.9 g N-eq, and 0.2-0.3-0.4 kg SO2-eq, consecutively, using the investigated system. The most sensitive parameters for environmental impacts were heat, aquafeed, electricity, and infrastructure (in all scenarios). For EA, benefit to cost ratios (BCRs) and three other widely used indices were analyzed for production cycles. The BCRs were 0.47, 1.16, and 1.75 for tilapia, conventional walleye, and hybrid walleye, respectively (using a 10% discount rate and a 20-year horizon), highlighting the necessity of optimizing both cash inflows (e.g., energy costs) and outflows (plant and fish revenues) to achieve practical enhancement of return on investments. The major cost contributors were infrastructure, labor, and heat (contributing to >89% of total costs for all cycles). Suggested steps for in-effect improvement of the investigated aquaponic system's environmental and economic favorability include heat and infrastructure optimization by (a) applying effective heating strategies (e.g., advanced insulation techniques), and (b) expanding the system's operational lifespan (e.g., prevention of waste accumulation).