Farm Cuts Fuel Costs with a Flex-Fuel Biomass System
Woodchip and Peat Pellet Heating System
Heating Capacity (output): Two 400 kW boilers totaling 800 kW (2.7 MMBtu/hr)
Emissions Reduction and Combustion Control Equipment; Cyclone, O2 sensor control, moving grates
Year Installed: 2007
Thermal Output: Hot water
Nordstrom Greenhouses PDF
Mats Nordstrom’s farm in Närpiö, Finland raises hydroponic tomatoes in a 7,500-square-meter (80,000 square foot) greenhouse, a relatively small facility in this agricultural area where many farms raise crops in large greenhouse facilities. Nordstrom’s plants grow in vertically supported vines, all the way to the top of this indoor space—and the cost of keeping these tomatoes warm is a major part of his farm’s operating budget.
Nordstrom used to depend entirely on oil to deliver this heat. But in the 2008-09 season, he drew on an oil burner for only 20 percent of the heat his greenhouse needed.
“This year, when the oil price is down, I’ll burn some oil,” he says. “But when the price goes up again, I won’t.”
Nordstrom now has that choice because he recently installed two small, modular biomass boilers that sit side by side next to his greenhouse.
Produced by Megakone, a Finnish company that specializes in small-size, modular boilers that are quickly installed and reliable to operate, the heating plant at Nordstrom’s farm can burn either wood pellets, peat, or woodchips. Nordstrom uses peat pellets and woodchips; he says peat is generally cheaper, but it creates more problems in combustion than woodchips.
“The two Megakone heating plants together require about two hours per week of labor,” the farmer explains. “If we burn peat, there is slagging on the grates and it takes more of our time. That’s why we would prefer to burn wood. Unfortunately, we do not have a good supply of small woodchips in this area and we are forced to burn peat.”
“A heating station fully completed at the factory is more economical than a new heating station built at site,” says Megakone’s website. “The building of a heating station could not be any easier—site building has been minimized! Before you know it, the station is heating the production premises. The silo can easily be filled with a front loader and frequent filling is no longer necessary.”
Megakone has sold more than 500 of its modular units, and many other farmers in Nordstrom’s area also heat their greenhouses with biomass. Nordstrom’s boilers each produce 400 thermal kW, or a total of 800 kW (2.7 MMBtu/hour).
Improving System Efficiency
Nordstrom’s farm is about 50 kilometers (30 miles) from Vasa, a Finnish industrial city. Like many communities of northern New England, his local economy has suffered from the loss of a local paper mill. About half the jobs in Närpiö were lost when the mill closed, the farmer says.
Nordstrom buys his tomatoes in the flower stage, and raises them to full maturity in eight weeks. In his greenhouse, hot-water heating pipes run alongside the vines as horizontal pipes and vertical flex tubes.
Biomass fuel in the area is sold on the basis of its energy content rather than its volume or weight. For his woodchips, Nordstrom pays €33 per MW hour ($13 US per MMBtu).
“Our smallest, residential-size systems are 30 kW (100,000 Btu/hour) in capacity,” says Jari Luoma, CEO of Megakone. “Mostly they are used to burn pellets. But some are owned by small hobby forestland owners who chip their own fuel.”
In actual practice, about three-quarters of the heat that Nordstrom’s greenhouse requires comes from its electric lighting. About 600 kW of heating capacity are delivered by the lights.
“Greenhouses require a lot of heat,” Nordstrom says, “and our lights—needed for enhanced growing conditions—provide a tremendous amount of heat. This is a big operating cost for us.”
He adds, “I’m thinking about putting in a big accumulator, or buffer tank”—an insulated tank that can store the hot water produced by the heating plant, then distribute it as needed. “The heat load of a greenhouse is very spikey, so a buffer would even that out and make the biomass system run more efficiently.”