The annual life cycle burden of a computer is 5,600 MJ. Because only 34% of the desktop's life cycle energy consumption occurs during the use phase, extending the lifetime of a computer could mitigate the energy burden of the production and disposal phases.
Development of Sustainable Shrimp Aquaculture
The purpose of this study is to compare the sustainability and environmental impact of two aquaculture systems suitable for adoption in the U.S.: 1) a zero-exchange, recirculating indoor system, and 2) a photosynthetic, suspended-growth system applied in flushed outdoor ponds, the typical shrimp aquaculture system today. Shrimp are marine, warm-water species, with optimal temperatures for growth around 28oC. Thus, to be feasible, shrimp aquaculture in Michigan requires a greenhouse or indoor system with heating and temperature control, salt water prepared by adding salt or by using local brackish water sources, and water treatment to allow recycling of the water. The energy and material costs of such a system may exceed those of outdoor production facilities in warmer areas with ready access to salt water; however, other costs, such as marketing and transportation costs, may be reduced. Therefore, it is necessary to do a comprehensive financial, energy, and material analyses over a production cycle in order to produce an integrated assessment of the overall impact of the indoor system.
Our comparison will utilize life cycle analysis (LCA), mass balance modeling, evaluation of microbial communities in the indoor system, and cost-benefit analysis of both systems. The indoor shrimp aquaculture system is relatively unstudied and will require field analysis. We already have sufficient data on a model outdoor shrimp pond system to do the major analysis needed for LCA and mass balance modeling.
The major objectives of this study include:
1. Perform LCA and life cycle cost analysis (LCCA) for two shrimp aquaculture systems, with emphasis on comparing an outdoor, flushed pond system and a zero-exchange, recirculating indoor system.
2. Develop mass balance models of the two shrimp aquaculture systems to make it possible to evaluate methods to improve the economics and reduce the environmental impacts of these systems.
3. Collect microbial, chemical, and other data from the indoor system to understand its longterm sustainability of water quality.
4. Build a lab-scale aquaculture system to experimentally evaluate best ideas generated from objectives 2-3 using principles of life cycle design.
The combined results of this work will test whether indoor aquaculture systems are more sustainable than outdoor systems in a common currency (energy, nutrients, etc.). Indoor systems have advantages in controlling disease, since they are enclosed and are removed from disease sources in marine systems. They could provide a new agriculture system of benefit to inland states like Michigan, and could significantly reduce the transportation costs and burdens of shrimp sourced from overseas and sold in metropolitan areas like Chicago and Detroit. At a minimum, this approach will help elucidate the relative advantages of indoor and outdoor shrimp aquaculture and determine the role of microbes in shrimp aquaculture, and at maximum, it will provide stimulus for a new industry in the state and region. In addition, this study will begin the analysis of environmental impacts for disparate food production systems that involve largely different costs and environmental effects, and in the future, we envision using such an approach to compare aquaculture and wild fisheries, as well as aquaculture and other agriculture systems, in a common currency.