Synergies between industry and nature - An emergy evaluation of a biodiesel production system integrated with ecological systems

Techno-ecological synergy (TES) is a framework that encourages integration of technological and ecological systems. Specifically, it incorporates the role of natural capital in engineering assessment and design by quantifying both demand and supply of ecosystem services. Emergy can provide valuable support to improve and interpret TES evaluation, as it is a methodology particularly useful for evaluating systems at the biosphere-technosphere interface. The present study evaluates how the TES framework based on emergy can shed new light by comparing conventional technological alternatives and ecological alternatives for meeting a particular ecosystem service demand. Both the demand and supply of ecosystem services are quantified in consistent units of emergy to obtain aggregated TES metrics. Specifically it was found that additional equipment to treat air pollutants have a higher emergy investment as compared to the forest ecosystem, while the technological unit to treat wastewater requires less emergy as compared to the horizontal subsurface flow wetland, its ecological counterpart. This new approach is tested by application to a biodiesel production plant and by calculating emergy metrics. This work shows that emergy can provide a fundamental improvement to the current TES framework, as it provides an aggregated metric for multiple ecosystem services.