On-Farm Heating with Biomass at River Berry Farm in Fairfax

David Marchant and Jane Sorensen of River Berry Farm—an organic vegetable and fruit producer in Fairfax—were early adopters of biomass heating when they installed a corn and pellet furnace in one of their greenhouses in 2008. The furnace required manual lighting and was snuffed out often when strong winds blew, and did not produce reasonable heat. “I kept thinking, there has got to be a better option,” recalls David, “It was a real labor burden, and you couldn’t count on it.”

Based on their early experiences and bolstered by a commitment to long-term sustainability and reduced fossil fuel dependence, River Berry Farm opted to host a biomass heating demonstration project. This time, they opted for a higher-rated boiler rather than a furnace. Boilers produce hot water, rather than hot air, which allows more options for distributing the heat. The new system also had an automated propane ignition system.

The biomass heating demonstration was part of a UVM Extension project aimed at trialing several furnaces in agricultural heating applications with funding support provided by the High Meadows Fund. According to Chris Callahan, Ag Engineer with UVM Extension Agricultural Engineering Program who assisted with some of the design and performance assessment, “The main lessons learned from these early installations were to buy high quality fuel, seek improved automatic ignition controls, invest in a good chimney and install it well, and know the actual heat output rating of the unit.”

Modern biomass heating appliances generally include a fuel storage bin, an auger for feeding fuel to the appliance, the appliance itself (boiler or furnace) with an ignition system, a combustion chamber, a heat exchanger, and a heat distribution system. They also incorporate some means of controlling combustion, fuel feed rate, and air flow and often include emissions control measures and automated ash removal.

The selected boiler was a Central Boiler Maxim 250 with a 250,000 BTU/hr input rating, efficiency of 87.8%, and EPA Phase II Hydronic Heater qualification. “The boiler makes hot water which we can use in multiple greenhouses by plumbing it to them in insulated PEX piping.  Once in the greenhouse, we convert to hot air with a hot water fan coil, put it in the ground for root-zone heating or on the benches in our mat-heating system for starts,” says Marchant. “I like it. I keep trying to find something wrong with it, but I can’t. The payback period is a bit longer due to higher initial costs, but you have to expect that.”

The basic system cost was approximately $13,000 for the boiler, bin, pad, and plumbing to a hot water fan coil. The other heat distribution systems included in-ground PEX, heat exchange, and plumbing for a bench heat system and added approximately another $5,000. The system is more automated and reliable than the earlier furnace was, but the higher initial costs and the fact that the system is only used 3 months out of the year do prolong the payback period to about 12 years when compared with a propane furnace. If the system was used for 6 (space heating) or even 12 months (wash water, pasteurization) of the year the payback would be halved or quartered, respectively.

“In addition to the financial payback, the carbon emissions avoidance is also of interest to many people,” says Callahan, “In River Berry Farm’s case, the Maxim is helping them avoid 5,910 pounds of net CO2 emissions per year which is about equivalent to 5,000 miles car travel or the CO2 sequestered by half an acre of pine forest.”

Learn more about UVM Extension’s Agricultural Engineering Program at.

This story was originally released in a series of energy case studies showcasing farms, businesses, vendors, installers, and technical assistance providers who have made a difference with energy efficiency savings and renewable energy production—all of which are components for helping Vermont reach the renewable energy and environmental impact goals of the Farm to Plate Strategic Plan. Learn more at www.vtfarmtoplate.com.