Abstract
Symbiotic integration of agricultural activities is widespread but quantitative assessments of the environmental benefits are scarce. To explore the potential benefits of applying the industrial symbiosis approach in agriculture and horticulture, a detailed case study is reported of a potential Eco-Industrial Park (EIP) including three activities: dairy farming, greenhouse cultivation of vegetables, and mushroom growing. These activities are widespread world-wide but, to enable quantitative assessment, the specific EIP studied is located in the Canadian province of British Columbia (BC). The activities are linked by anaerobic digestion of dairy manure to produce biogas and digestate. Biogas replaces natural gas to supply heat to the farms and carbon dioxide (CO2) to the greenhouse. Digestate is separated into a liquid fertilizer and a solid substrate; the former replaces chemical fertilizers and the latter can be utilized as cow bedding and growing medium for plants and mushrooms. Mushroom growing emits CO2 which is conventionally ventilated but can be used for stimulating plant growth in the greenhouse. Life Cycle Assessment (LCA) is used to quantify the environmental benefits of the EIP compared to conventional independent farms. Non-renewable energy consumption, greenhouse gas emissions, aquatic acidification, respiratory effects from organic emissions, and human toxicity can be reduced by 50%–90% and aquatic eutrophication and respiratory effects from inorganic emissions can be reduced by more than 10%. Such EIPs can also alleviate nutrient management problems in regions with intensive livestock farming.
•An LCA model of EIP linking AD of dairy manure, greenhouse and mushroom operations.•Exchange of by-products enhances energy and material self-sufficiency.•Digestate utilisation within the EIP improves nutrient management.•Reductions of ∼60% achievable in non-renewable energy use and global warming potential.•Reductions of 10%–90% achievable across five other life cycle impact categories.