Heater Hens and Hothouses

By Rupert Jannasch

Signs of consensus among resource experts that known oil reserves will peak in about six years' time reminds me of a novel grow system invented by an Israeli scientist. He manufactured an automated, hydroponic greenhouse out of sheet metal and glass. A bit larger than a hotdog stand but smaller than a combine, the unit was designed to produce enough food for a small family without needing land or oil.

His invention was not strictly organic, but the man's thinking was on the right track. Agriculture and transport account for the bulk of world's oil consumption, and some day food production as we know it will grind to a halt. Organic agriculture will be no exception. As it is increasingly styled after the conventional food system, complete with processing, packaging and bewildering methods of distribution, there is a clear need to consider alternatives.

One approach is to integrate greenhouse and livestock production. Researchers are already investigating using methane from intensive livestock operations for heating greenhouses.

On a smaller scale, it is more efficient to house livestock and crop plants in the same building. The animals generate plant food in the form of carbon dioxide, nitrogen-rich fertilizer and heat. The animals benefit from shelter. In a pinch, a compost pile will produce heat just as rabbits or chickens do.

At Solviva, on Martha's Vineyard, Massachusetts, Anna Edey employs one hundred chickens and 30 angora rabbits to help heat a 3000 ft² greenhouse. The sun does the rest. The animals are housed at separate ends of the building. Using water bag heat collectors, growing temperatures are kept at a minimum of 44 degrees Fahrenheit without supplemental heating. Fresh produce is harvested year round.

One chicken yields about eight BTUs per hour per pound, or the equivalent of two and one half gallons of fuel oil in a year. Carbon dioxide levels are about four times higher in the greenhouse than outside.

The reuse and recycling of carbon, nutrients and energy generates a high level of biological efficiency. In contrast to conventional systems, purchased inputs are minimal. Production costs should remain stable when energy prices soar because the sun, livestock and microbes do most of the work. Depending on scale, the method is affordable for novice growers with limited access to land or capital.

Granted, the operation is management intensive and requires technical and scientific know-how. For instance, ammonia levels released from the manure need to be regulated. At Solviva, this problem was solved using research from the Cape Cod based, New Alchemy Institute (NAI). Researchers demonstrated that ammonia can be vented through perforated pipes laid in the soil. Circulating ammonia through damp soil, rich in carbon and microbes, converts it into nitrate nitrogen - the form needed by plants.

Another trick is to balance carbon dioxide, nitrogen and heat production. For example, heating a greenhouse (with compost only) in southern New England requires half a cubic yard of compost per square foot. However, this process generates six times more carbon dioxide and 50 times more nitrogen than what is needed by plants. The NAI recommends basing the size of the composting operation on optimum levels of carbon dioxide. In other words, it is better to sacrifice some heat so as not to produce excess nitrogen.

Certainly, there will be other technical challenges, especially with larger scale facilities. But surely, if we can learn to milk a cow with a computer for the dubious distinction of putting people out of work, then developing integrated greenhouse technology should be a cinch.

The difficulties of marketing to other than family and friends should also not be overlooked. The ideal, of course, is having a dedicated clientele willing to buy products in season, a locally owned grocery store and a thriving restaurant within a half hour's drive from the farm.

To be sure, Anna Edey's customers near Boston and in New York are of the well-heeled variety. Perhaps this accounts for the somewhat questionable claims made in her book, Solviva, about earning half million dollar incomes with hybrid greenhouse barns.

Nonetheless, it is to her credit, that she has demonstrated both production and marketing to be feasible. Although the current economic climate makes it easy to dismiss the technology, the future will demand more innovative ideas, not fewer.

The New Alchemy Institute no longer operates, but an extensive list of research reports on solar greenhouse design and soil and water management are available. The accomplishments and failures of an NAI-led attempt in Prince Edward Island to supply food, power and shelter from one building is reviewed in "A Story of the Ark and the Institute", by Alan MacEachern (Island Studies Press, 2003).

Eliot Coleman has written extensively about winter vegetable harvesting in "Four Season Harvest" (Chelsea Green, 1999).


Rupert Jannasch, M.Sc., P.Ag. is a consultant for the Organic Agriculture Centre of Canada. Please send comments or questions by phone to 902-893-7256 or by email.


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