A new curing technology, developed in Croatia, substitutes biomass for expensive oil and gas.
By Robin Sutton Anders
For the past five years, Croatian tobacco growers have witnessed a startling decline in revenues. But unlike other farmers around the globe who attribute their recent losses to lower demand, poor weather conditions or stifling regulations, Croatian growers point to a rising cost of energy. “The decrease in growers’ profits is estimated to be 15 percent, so the production of tobacco is stagnating, or even slightly decreasing,” says Vladamir Hrovjc, managing director of Herbas d.o.o., a Croatian company that manufactures tobacco processing machinery.
“Tobacco drying costs have increased up to 40 percent in the last five years,” Hrovjc continues. This increase is foreboding for the entire Croatian industry, including Herbas, whose machinery sales depend on the industry’s success. So through long-term cooperation with Hrvatski Duhani, a leading Croatian manufacturer of flue-cured Virginia tobacco, Herbas set out to reduce the cost of drying flue-cured tobacco for struggling growers.
Because the typical Croatian tobacco barn’s thermal generator relies on expensive gas or oil to dry its flue-cured tobacco, Herbas immediately recognized the need to find an alternative energy source. According to Hrovjc, the company started by experimenting with biomass like wooden chips, pellets and firewood. An effective generator, however, would take more than just a new fuel source, Hrovjc says. “Tobacco is typically dried using thermal generators fueled on gas and oil because using biomass tends to lead to great temperature losses. The temperature of outgoing gasses was around 300 degrees Celsius.”
The company developed a new model thermal generator based on the principle of pirolitic biomass burning, which it hypothesized would lead to more efficient combustion. The result was encouraging—the temperature of outgoing gasses in the chimney measured 130 degrees C.
Hrovjc explains how it works: “The biomass is put into the input hopper, which can be positioned at the side or in front of the thermal generator,” he says. “Then it is transported by a caterpillar conveyer system into the furnace. This dual-axial caterpillar transporter system ensures safety from [the] return flame.”
The barn’s thermal generator furnace—located beneath the ventilator—is made out of sheet metal, and the parts exposed to intense heat are constructed from fireproof sheet metal. “An 18,000 cubic meter air-per-hour ventilator creates forced air flow,” Hrovjc explains. “The thermal generator has primary and secondary air dampers which are angled at 90 degrees so to manually choose the ratio of external unsaturated air and internal recycled air. The temperature of output air is 130 to 150 degrees Celsius.”
Basically, Hrovjc says, the dry distillation of wood is carried out within the furnace, which creates a gas that burns with minimal ash and soot. “So cleaning the furnace is easy and done only once in a drying cycle.” Ash is removed manually by emptying the ash tray. And depending on the type of biomass used, it is necessary to periodically clean the thermal generator chimney.
Putting it to the test
Last year, Herbas conducted a series of tests to determine whether the biomass was, in fact, more cost-efficient. “We compared natural gas, oil and biomass,” says Hrovjc. “The results indicate that drying tobacco in thermal generators fueled on biomass is three to four times cheaper than those fueled on gas, and five to six times cheaper than those fueled on oil.”
Of the three biomass forms tested (wooden chips, pellets and firewood), firewood 1 meter in length was shown to be the cheapest fuel for drying.
Justin Macialek, a research assistant at North Carolina State University who studies tobacco mechanization and post-harvest curing structures, visited Herbas’ research facilities this past August to see for himself the company’s new curing technology.
Macialek also works with biomass fuels to generate heat for tobacco production and, like Herbas, understands growers’ interest in biomass fuels runs deep into their bottom line, as rising fuel costs in the United States also contribute to growers’ production costs. “One of the issues driving biomass burner selection is the uncertainty of gas prices that vary from year to year,” he says. “This past year it was $1 a gallon, but the year before it was $2 per gallon. That makes it tough for growers to budget their production costs.”
In Macialek’s view, Herbas’ biomass fuel system performs above standard, but he points to a remarkable adoption rate of the burners by Croatian growers as evidence of its success. “This is the second year biomass burners have been available to Croatian growers,” Macialek says. “The first year their technology was available, two growers used the burners. This past growing season, 42 growers utilized the technology. They were able to adapt the technology to existing barns and also build new barns using biomass burners. That greatly reduced their production costs.”
From hothouse to greenhouse
According to Macialek, U.S. researchers have been tinkering with biomass burner technology for a while. At North Carolina State University, the biological and agricultural engineering department studied biomass as a fuel alternative for tobacco barns in the late 1970s and early 1980s. “When gas prices went back down, nobody wanted to use wood for heating,” Macialek says. “But in 2007, when gas prices started increasing again, people gained a renewed interest in alternative energy and we started looking at biomass fuels again.”
Whereas these new burners can torch costs in Europe, implementing the technology in the United States is not necessarily the most cost-efficient strategy, says Macialek. “In the United States, a very small percentage—at most 5 percent—of growers currently use wood as a fuel source.”
All things being equal, Macialek believes gas is more efficient and convenient for most U.S. growers, as fueling barns with biomass requires extra management time and maintenance costs.
And although the payback period for initial investment in Herbas’ technology is just three to five years, most growers only have contracts for one year at a time. “It’s difficult to make an investment for three to five years if growers are uncertain whether or not they will have a contract in the following years.”
For growers uncertain about their future with tobacco, old barns can be retrofitted to fit the biomass burner technology. Further, growers can use their burners for a variety of farming needs, dramatically slashing the payback time.
“A disadvantage of buying this equipment is that tobacco production only lasts two to three months a year, so you’ve got a short time to recoup costs,” Macialek says. “However, we work with a grower who uses this boiler system on his barn for tobacco in the summer, and in the winter he uses it for his greenhouses while he grows tomatoes. In late winter he’ll use the system to heat tobacco transplant houses.”
Hrovjc believes the investment in biomass burner technology can be recovered more quickly—in just two to three years. One grower, he says, even recouped his expenses in one year.
The future of biomass
Macialek predicts technology like Herbas’ biomass burner will only be adopted in the United States if the market turns enough so that alternative fuel technology offsets grower input. “It really comes down to convenience,” he says. “Even though gas prices are currently anywhere from five to 10 times the cost of wood, there’s a lot of value in the convenience of flipping a switch.”
In the meantime, there’s no question that Croatian growers have already realized the benefits of Herbas’ new technology. “It’s beneficial that the growers have committed to using biomass to fuel their barns,” says Macialek. “And if Herbas can help local growers produce tobacco for a lower cost, they can in turn pay lower costs for that tobacco.”
As local growers continue to realize the benefits of Herbas’ new technology that saves money while stabilizing input costs, what’s on the horizon for the tobacco machinery manufacturing company? “We’ve already come up with some high-quality solutions for increasing machine capacity and improving raw material processing,” says Hrovjc. “In the future, we’d like to continue to modernize production and develop new processing lines for our customers.” For the country’s growers and manufacturers alike, new technology that aids in production while reducing input costs will likely be an easy sell.