Case Study: Promoting Sustainable Energy Greenhouse Heating Systems to Small-Scale Local Farms

Biomass energy generated from livestock manure, other agricultural by-products and food waste can be an affordable greenhouse-heating energy source for those seeking lower energy costs. Appalachian State University, North Carolina (NC), USA, has built a 6.1 m × 9.1 m greenhouse, called the “Nexus” to test the integrated sustainable energy heating system for growing season extension with less energy cost. This is done by using on-farm biomass resources/wastes such as agricultural waste and wood chips to produce energy coupled with solar water heating to store and supplement required thermal inputs. Growing season extension with heated greenhouses increases the availability of local food throughout the year, expands available markets and increases farmers’ profits. Nexus includes an above ground 5,680-L water storage tank and an aquaculture pond. It is supported by a small-scale pyrolysis system, an anaerobic digestion system, solar thermal and compost heating. The preliminary result showed that compared to a conventional space heating system, about 30% of energy was saved to keep the greenhouse temperature available for growing by radiation from the water storage tank. The main purpose of this study was to test the proposed greenhouse heating systems developed at Nexus by implementing pilot systems on two local farms. Pyrolysis and solar thermal system in conjunction with heat storage and delivery system for each farm were built and tested in order to demonstrate how to reduce greenhouse energy use. This paper describes the results of the case study, which showed significant energy savings that can promote the resource-limited farmers’ interest.