Massachusetts has over 1,000 growers producing greenhouse crops in 12 million square feet of protected growing space (2002 Census of Agriculture). This includes over 10,400,000 sq ft. in bedding plants, flowers and floral greens, foliage plants and potted flowering plants and over 700,000 sq ft in vegetable crops. Greenhouses need to be heated all winter for some flowers and bedding plants, or may be started in midwinter, late winter or early spring depending on the timing and needs of each crop. Temperature needs of the crops vary, but often require a night temperature of at least 60 degrees F. Most of Massachusetts’ greenhouses are heated with either fuel oil or liquid propane. A 20,000 sq. ft. greenhouse, heated all winter with a night temperature of 60 degrees F, uses an estimated 3200 gallons of fuel oil or the equivalent (Bartok, 2006). While there are no firm figures on the total fossil fuel used for greenhouse heat in the state, we know that we have the equivalent of 550 greenhouses that are 20,000 sq. ft. in size. If only one third of these greenhouses are heated all winter, and two thirds of these greenhouses begin heating in late winter (using one-third the heat energy), our total use of fossil fuels for greenhouse heat is equivalent to nearly 1 million gallons of fuel oil, with emissions in the range of 22 million pounds of CO2 annually.
When we began this project in the winter of 2008-2009 floriculture and vegetable growers were in a state of shock over the prices of propane and heating oil they were facing, and face continued economic risk from volatility in energy costs. While growers are able to significantly reduce their energy consumption through conservation measures and by starting plants later in the winter, there is a limit. In order to maintain greenhouse tomatoes, spring bedding plants or vegetable transplants at the required minimum temperature for healthy growth, supplemental heat is essential. In floriculture, greenhouse production is the core of the industry. Greenhouses are not incidental to the vegetable industry; vegetable transplants are used to ensure good crop establishment, avoid insects, diseases and weeds, reach early markets, get high yields, and ensure an early season cash flow. For both vegetable and floriculture industries, solving the question of how to heat these greenhouses often means the difference between staying in business, or not.
This project focused on shelled corn, a renewable heat source that can be grown and used in Massachusetts more cheaply than fossil fuels, using available and proven technology. At current prices, corn compares very favorably with the standard fossil fuels that are used for greenhouse heat. Changing to energy sources that can be produced locally, travel a short distance from producer to user, and that have a high ratio of energy output to fossil fuel input is key to a viable future for farming in Massachusetts. Growers who shift to a source of carbon that is sequestered and burned for fuel on an annual basis will reduce the load of carbon dioxide emissions from fossil fuels and will reduce our reliance on foreign sources of petroleum. These growers will also reduce their own fuel costs, and by purchasing a locally produced fuel, will provide increased revenues for farms that grow this new crop.
Although shelled corn is certainly not the only viable or promising choice as a source of biomass for fuel, it does have many advantages. It is one of the most clean-burning fuels, producing few particulates, no carbon monoxide and virtually no environmental pollution (Dr. Dennis Buffington, Pennsylvania State University, 2004). What remains is less than 1% ash, in a form that is safe to use on agricultural soils. There is no risk of toxic spills or explosions. Corn sequesters carbon in a single growing season, making rapid use of solar energy. The ratio of fossil fuels invested (as fertilizer and fuel) for energy gained (as BTUs of heat) ranges from 1:5 to 1:10 depending on yield, quality, weather and other factors (Buffington 2004). Fertilizer inputs can be partially offset with organic sources such as manure and legume cover crops. When grain is harvested, over half of the biomass is returned to the soil, helping build organic matter. As an annual crop, grain corn provides flexibility for selecting fields and can be worked into existing rotation strategies on vegetable and dairy farms. On vegetable farms, corn is a valuable rotation crop because it is not susceptible to the same diseases and insect pests as cucurbits, tomatoes, peppers, or most other vegetables. Cucurbits (squash, pumpkins, melons and cucumbers) comprise nearly 40% of our vegetable acreage, and are subject to a growing number of serious diseases. Growing fuel corn in rotational system allows growers to take fields out of production of these crop groups, while still providing income.
The emphasis of this project was on making the best possible use of our land for food and fuel production and not to detract from our ability to grow food crops. We're envisioning a system where fuel crops become a valuable rotational crop in vegetable farms and an alternative revenue stream for dairy farmers.