Salads for all seasons. Solviva solar greenhouse grows organic crops
West Tisbury, Mass.
With little or no previous experience in organic food production or solar design, a Swedish-born weaver on Martha's Vineyard is successfully demonstrating on a small scale that year-round organic agriculture and energy independence are possible in the northeastern United States. As Anna Edey's Solviva Winter Garden expands distribution of high-quality salad greens, and as the heating bills of conventional greenhouses again begin to eat profits, the economic viability of Ms. Edey's alternative is increasingly evident.
``Solviva is an example of a successful trend in agriculture toward specialty crops,'' says analyst Norm Marshall of Cape Cod's New Alchemy Institute. ``Economists call this `value added' at the farm - higher quality, more variety, as opposed to the traditional one- or two-commodity family farm.''
``If you don't know what to do,'' recalls Edey, architect-owner-manager of the Solviva greenhouse, ``it's really hard to keep delving into the problems.''
The problems include: the chemical contamination of food, expecially produce, by fertilizers, fungicides, and increasingly ineffective pesticides; the northern states' dependence on external food sources (in Massachusetts, for example, 85 percent of the food is shipped in); and a nation's growing dependence on foreign and finite fuel sources.
Built in 1983, the Solviva greenhouse is a two-story A-frame structure, roughly 4,000 square feet in size with 1,800 square feet of growing beds. The interior is passively heated by sunlight through the south face, pitched at a 45-degree angle and glazed with Sungain polyester panels. The panels, donated by the 3M Company, insulate as effectively as four sheets of glass, while transmitting more light than two sheets, according to the manufacturer. Six inches of fiberglass insulation cover the east, west, and north walls. Further heat retention occurs within two interior water walls, which hold 3,600 gallons and on a sunny day rise in temperature from 60 degrees to 80 degrees F.
Electricity is generated by a bank of photovoltaic cells, powering the pumps, lights, and convection fans.
Now in its fourth winter of operation, Solviva's internal thermometer has yet to dip near freezing, which would necessitate emergency heat from a wood-eating firebox. A subsurface clay-pipe irrigation system draws sun-warmed water down from a 600-gallon central tank then up to the plants by capillary action. This helps keep soil temperature at a healthy 57 degrees F.
Thus, while initially more expensive and demanding to build, and more labor-intensive to maintain, Edey's Solviva design has rapidly made up the cost difference with negligible heating and cooling costs. Conventional greenhouse materials run roughly $6 per square foot, according to Robert Luczai of the University of Massachusetts, Middlesex Extension. According to Edey, Solviva's materials ran $8 per square foot. But conventionally heated competitors currently pay $2 to $2.50 per square foot in heating and cooling, or on the order of $8,000 per year for a Solviva-size greenhouse.
Somewhat more difficult to calculate, and less technical in nature, is the heat contribution of 30 Angora rabbits and 100 or so laying hens penned at either end of the greenhouse. Edey estimates that the animals provide the equivalent of 500 gallons of oil per winter in body heat, as well as increased carbon dioxide for plant respiration, nitrogenous waste for composted fertilizer, angora fleece at $8 per ounce, and something like 24,000 eggs per year.
``The animals definitely pay for themselves,'' says Edey, originally a weaver by profession, who blends the Angora fleece with sheep wool for distinctive yarn.
This same sensibility, at once pastoral and pragmatic, Edey has applied to the cultivation of produce - over 18 varieties of lettuce, greens, and herbs, all with considerably extended growing seasons by regional greenhouse standards.
Composting of house sewage and animal waste with sawdust and leaf litter provides fertilizer. Fungus is minimized by interplanting resistant varieties, as well as by vigilant pruning. In lieu of chemical pesticide, Solviva employs the integrated pest management technique pioneered at the New Alchemy Institute. By this method, beneficial varieties of insect predators are introduced to check plant-eating insects. Ladybugs, for example, prey on aphids.
``Sometimes it takes a while for the good guy to catch up,'' confides Edey. ``But you have to keep saying `I'm not going to spray.' If you spray, you harm the beneficial insect. So you just have faith and ask them to please get on with the job.''
Solviva initially began selling to local markets only. But the quality of the produce so impressed Massachusetts agriculture secretary August Schumacher a year ago that the Vineyard greenhouse has since received two small state grants for packaging and distributing to the Boston market.
``The Solviva grants are part of a program to promote high-quality, locally grown foods in areas of competitive advantage,'' explains Mr. Schumacher. By year's end, Edey hopes to harvest 1,000 of 15-variety salads per week, a large number shipped to Boston markets within 24 hours.