What can you tell me about bio-heated greenhouses?
Answer: A bio-heated greenhouse most often refers to the practice of generating heat in a greenhouse from animals, but it can also refer to using compost. The following information focuses on the use of animals in a greenhouse as a heat source. For information on composted heated greenhouses, refer to the ATTRA publication Compost Heated Greenhouses, available at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=57.Generating heat in a greenhouse from animals is primarily accomplished using small livestock, such as chickens and rabbits. Farmer Anna Edey, of Solviva Solar Greenhouse, successfully raises chickens and rabbits in her solar and bio-heated greenhouse. She tried to incorporate small ruminants into her greenhouse operation but discovered that the heat generation from the sheep flock was not significant. Growing Power, an urban farm nonprofit, uses aquaculture to heat its greenhouses.Generally, there are two main reasons to incorporate animals into a greenhouse. First is the biothermal heating produced by the animals. According to Edey, chickens and Angora rabbits each contribute about 8 BTUs per pound of weight, which she states is the equivalence of 2? gallons of fuel oil per animal per heating season (1). The second reason is to create a bio-shelter. The bio-shelter serves as both an animal shelter and as a greenhouse, which can help reduce costs. Edey has written the book Solviva ? How to Grow $500,000 on One Acre & Peace on Earth, which is available at bookstores, libraries, or on the Solviva website: www.solviva.com.While rabbits and chickens can provide warmth in a greenhouse, it is important that they receive adequate ventilation as the higher temperature and humidity of a greenhouse are generally not healthy for animals. Ventilation is very important in preventing a build-up of ammonia and preventing the spread of diseases.Edey uses an “earth-lung” to filter out the toxic ammonia gas from the rabbit and chicken manure, and her chickens are kept in a poultry room in the greenhouse where temperatures do not fluctuate from about 70? F (1). She does not have a backup heating system for cloudy days and does not believe it to be necessary. She believes that the carbon dioxide emitted by the animals enhances plant growth in the greenhouse. The manure is composted.Reference: (1) Anon. 1998. Producer Grants: Michigan: Permaculture Greenhouse System: Integrating Greenhouse and Poultry Production. North Central Region SARE, 1998 Annual Report, University of NE, Lincoln, NE.