How One Grower Is Heating His Greenhouses This Year

To combat the single largest expense of owning and operating greenhouses, Dick Kearley of Robrick Nursery in Hawthorne, Fla., looked to the forest.

“I was inspired by the rising cost of fuel to find some sort of alternative,” Kearley says. “Then I began looking at wood for the alternative.”

When he first began looking at conventional wood-burning stoves, Kearley found the price to be astounding. Instead of paying around $30,000 for the equipment, he came up with a plan to go with something basic and low-tech. With a water stove, the simplified unit is essentially a fire box surrounded by water. The heat gets transferred to the walls and the water heats the greenhouse.

His initial problem appeared to be solved, but after using the water stoves for two to three years, Kearley wanted to improve efficiency. He had been learning about wood gasification, the process of converting organic materials into carbon monoxide, carbon dioxide, hydrogen and methane by reacting it at high temperatures.

Kearley thought this could be a good way to address the heating and efficiency issues. At that time, however, no one was willing or able to build a gasifier that could heat a greenhouse.

“Many people didn’t feel like it was worth it to build one,” Kearley says. “So I took what I was reading and went out to go build one.”

What Kearley ended up with was a piece of equipment that used unprocessed wood to gasify the greenhouse with a water heater backup. If the gasification failed, vents could be opened so the water heater would heat the greenhouse conventionally.

With his new design, Kearley saw savings of 80 percent. Although that figure is normally the attention-grabber, there is another number to keep in mind: the nursery owner estimates that 75 percent of the heat is generated by the gas and the other 25 percent comes from the fire box.

“It gives me goosebumps every time it lights up,” says Kearley.

Another benefit Kearley sites is creating minimal fuel waste. Whereas a coal-burning model might create 40 to 50 pounds of charcoal, the gasification stove turns out a mere 20 pounds of ash. The reduced smoke output also makes the stove a much greener option.

One positive that surprised the amateur inventor was how “controllable” his stove would be. Working like a conventional home oven, the gasification stove cycles its heat.

“It doesn’t cycle as fast as the home oven, but it does the same thing,” he says. “It might pop on and off every 20 minutes or so. It shuts off and turns back on quickly. The new stove is far better in that regard.”

There is one potential downside to the gasification stove, however: cost. Although Kearley kept the specific price point a secret – he doesn’t want anyone clamoring for him to build one for their greenhouse – he notes that the price tag might make some greenhouse owners sweat.

“I will say that this stove would cost more because it has more steel. It’s a complicated structure; it has 14,000 pounds of steel and 200 pounds of welding wire,” Kearley says.

Learn more about Robrick Nursery at www.robrick.com.

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2 comments on “How One Grower Is Heating His Greenhouses This Year

  1. tom wagner

    I'd really like to see more about the heating system using wood for fuel and water pipes to hold the heat….any pictures of this fellows system????

  2. William Carr (@Jkirk3279)

    The trick for gasification is to keep the fuel particle size consistent.

    Wood chips are the most common fuel; and they need to go through a drum sorter.

    That means having a huge source of wood chips or your own hog mill.