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Adams, Zak

Rubenstein School of Environment and Natural Resources

2005

M.S.

In the current food system, vast amounts of foods are imported into cold-climate regions to sustain winter consumer demand that cannot be met by local agricultural production. This process requires transportation and storage infrastructures, which are resource intensive and polluting. This system subsequently degrades human and ecosystem health in both the production and destination regions. Unfortunately the energy required to produce foods locally in the cold season using conventional greenhouse technologies is also resource intensive, polluting, or prohibitively expensive, therefore negating some possible benefits. Using principles of ecological design however, it may be possible to engineer a controlled environment that facilitates the production of food crops in cold climates while minimizing or eliminating the use of fossil fuels for climate control. A technology, referred to as Composting Greenhouses, has been proposed in various forms in sustainable agricultural networks and literature over the past three decades. This greenhouse or bioshelter has benefits over current practices ranging from reduction of pollution and resource use, to the strengthening of local food security and economies. It makes use of resources that are currently waste products of related agricultural processes subsequently reducing waste, closing local resource loops, and creating economic niches. Specifically, resources such as biothermal energy (heat), Carbon Dioxide (C0₂), Water Vapor, and Ammonia (NH₃) are contained and transferred fiom a composting operation to an adjacent greenhouse to provide a suitable climate for horticultural production. However, few greenhouses have actually been constructed and limited data has come from the experimentation and operation. Furthermore, no structure of this nature exists today that utilizes the vast amounts of feed stocks in the commercial composting industry. In short, the technology is still in its infancy after 30 years of experimentation. Construction of a reproducible, commercially viable system will require research, planning, and testing before it can be validated as a viable technology under specified applications. Preliminary steps include design and modeling of the contained environment to conclude issues of functionality, scale, and economy. For this reason, a systems model of a Biothermal Greenhouse has been created to simulate the processes. Data on input variables such as compost heat and C0₂ production, decomposition rates, and metabolic water generation, were extracted from peer-reviewed literature to create the basis for calculations that run the model. Operational data from a local composting facility, Intervale Compost, has been used. The model is run with weather data from Burlington, VT to simulate winter climate conditions. The modeling process has evaluated multiple hypotheses regarding operation to determine if the system can successfully function. It has been determined, based on experimental data, how much heat and C0₂ can be captured from a specified compost operation. The resources needed and produced from a compost system have been determined under several scenarios. Furthermore these results have been compared to the demand of a specified greenhouse structure and it has been determined how the resources produced from the modeled compost system compare to the needs of the modeled greenhouse. This work has answered previously unanswered questions through the comparison and has established a basis for further design of biothermal systems.