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Texas Agriculture Archive

December 5, 2003

Propane Power
Groundbreaking propane propelled products in the works...

By Lana Robinson
Field Editor

Liquid propane gas (LPG) has long been a practical, economical fuel for farm use, so it isn't surprising that a variety of groundbreaking propane-powered products will soon emerge to help farmers and ranchers address the challenges of growing food and fiber.

Exciting technologies designed to improve energy efficiency, production practices, yields, and food safety, while protecting the environment, are progressing nicely.

From broad spectrum tools, such as flame weeders and tractors, to products aimed at specific targets—including pathogens in poultry houses and soil-borne diseases that hinder crops—these emerging propane-propelled products have potential.

The Propane Education & Research Council (PERC) and the Alternative Fuels Research & Education Division (AFRED) of the Railroad Commission of Texas—working in consultation with the division's advisory committee and the Texas Propane Gas Association (TPGA)—are behind the cultivation of low-cost, low polluting uses of propane gas in agriculture. Partnering scientists and agricultural engineers at Mississippi State University, Texas A&M University, and the University of Florida have teamed up to hasten the development of these promising prototypes.

'Gator tail' kills nematodes

While crop rotation goes a long way towards reducing the risk of soil disease, it isn't always easy to do. Researchers in Florida looking for new ways to control soil-dwelling parasites that feed on plants are focusing on a propane soil pasteurization unit. Called the "gator tail," the unit heat treats soil to reduce nematodes, which annually do some $80 billion in damage to crops worldwide. Dr. Jim Leary, an Extension scientist and team leader of this project, says the primary enemy is root-knot nematode.

"We are mostly working with tomatoes, although other plants are susceptible to the root-knot nematode," says Leary. "Peppers, even strawberries, are possibilities. We're trying to work with organic growers with nematode infestations to consider this as an option. It doesn't actually sterilize the soil, but rather acts as a soil pasteurizer, so it retains a lot of important soil characteristics for good growth.

In appearance, the "gator tail" is an inverted trough, approximately nine inches in height with dual propane burners along the length of it. The soil pasteurizer plows through the soil, applying 125 F to 130 F degrees heat in an 8 to 12- inch deep zone deep.

It's a slow process, which is true of anything that puts that much heat into the ground," notes Leary.

Pioneered by Dr. Lawrence N. Shaw, a University of Florida agricultural engineer, seven years ago, the propane-powered implement has since undergone several changes to improve efficiency.

"We have not taken it out to commercial growers or organic farmers yet, but they are certainly willing to cooperate to make our final evaluations. We're shooting for completion of the project within the year. That's the target. The target is to actually move this on to a marketable process," Leary says.

According to Leary, the loss of methyl bromide, widely used as a soil fumigant in the vegetable industry for controlling soil-borne pests and diseases, has fast-forwarded the need for an effective alternative like the pasteurization unit.

The Environmental Protection Agency (EPA) determined that methyl bromide erodes the ozone layer and plans a total phaseout of the chemical by 2005. Without an adequate replacement chemical or technology, the National Center for Food and Agriculture policy estimates economic losses could be as high as $479 million.

"Higher production rates decrease costs for farmers and potentially, for the consumer. It (the soil pasteurizer) is at par with chemical treatments. It is a good alternative to methyl bromide because you are not putting chemicals in the ground or that vaporize and are ozone depleting. It's environmentally friendly," says Leary.

Flame weeding advancements

Another promising propane product currently involved in trials is a flame weeder, which directs a carefully controlled flame that kills weeds by simply passing over them. Available as hand-held, portable backpack or tractor-mounted models, flame weeders are successful in controlling broad-leaved weeds, when the weeds are small and dry. Although flame cultivation cannot be used with all crops, field studies in Weslaco suggest it works well in organic sugar cane production. Other states are conducting trials to determine effectiveness in cotton and soybean crops.

The recirculating covered burner flame weeder prototype developed by the agricultural engineering department at Texas A&M University, College Station, recycles heated air for greater efficiency. The burners shield the crop while allowing the flame to eliminate small weeds.

Steve Diver, an agriculture specialist in the Appropriate Technology Transfer for Rural Areas (ATTRA) program at the National Center for Appropriate Technology (NCAT) (University of Arkansas, Fayetteville), says the new flame weeding technology is rooted in an earlier concept.

"Flame weeding was commonly used in row crops like cotton and sorghum from the late 1930s until the mid-1960s, when selective herbicides became widely available. In the 1980s and 90s, flame weeding made a rapid comeback as a non-chemical weed control technique, especially among organic farmers," says Diver. "Essentially, you are helping your vegetable crops get off to a good start by eliminating early-season weed competition. Once the vegetable canopy forms, shade reduces weed germination; weed seedlings that do sprout can be controlled by mechanical cultivation."

Flame weeders suitable for market gardeners are already available from a number of sources.

Another branch of research funded by PERC and AFRED will explore "preemptive" heating techniques that inhibit germination of weed seeds in the row before crops go into the ground. Feasibility studies are also in the works for thermal defoliation of cotton.

Propane poultry developments

A major PERC-funded project has deemed the Bio-Burner, patented by Wallace Manufacturing, Siloam Springs, Ark., an effective aid in the reduction of microbial populations as part of a poultry and chicken-house management program.

"Sanitation in poultry houses kills salmonella and helps control some of the pathogens at the farm level," says project leader, Dr. Susan Watkins, Extension Poultry Specialist at the University of Arkansas Center of Excellence for Poultry Science, who along with scientists from Texas A&M University, conducted the research. "That helps us to reduce the cost of production and avoid the use of antibiotics. It's an alternative way to control disease. It's potentially safe. There are no residues when we use it. We don't have to worry about contaminating our food supply. Those are the key things that count for consumers."

The Bio-Burner is an insulated, stainless steel cabinet measuring 4 x 7 x 2 feet.

Six liquid propane torches supply a direct flame with a temperature of greater than 1900 F. Surface temperature during burning has been measured in excess of 900 degrees F. Exposure time is approximately 10 seconds.

"It can treat a large chicken house in less than an hour using 20 to 40 gallons of propane," Watkins adds.

Watkins points out that the concept of heat sterilization to destroy pathogens is not new, citing discoveries by 19th century chemist Louis Pasteur.

In the Bio-Burner trials, aerobic bacteria, E. coli, coliform, yeast and mold levels were significantly reduced after litter surface burning, and no Salmonella were found post burn. Other studies indicate the Bio-Burner may help control Clostridium levels in poultry houses as well as botulism. Subsequent tests, in cooperation with Pilgrim's Pride in Pittsburg, Texas, will establish cost data and evaluate a modified burner designed to deliver a higher, more consistent temperature.

Additional research will similarly test the feasibility of using propane to control insects and pathogens in cattle feedlots, Watkins notes.

Propaned-powered John Deere

Finally, John Deere has developed a propane-propelled 74-horsepower tractor.

The John Deere Model 5410, developed at the Southwest Research Institute (SwRI) in San Antonio with grants provided by the Texas Alternative Fuels Council and PERC, features a lean-burn combustion system and electronic controls. The tractor has undergone stringent field testing under real-world conditions to assess performance and reliability.

Tier 3 emission standards, effective in 2008, will restrict off-road equipment emissions of nitrogen oxides (NOx) and non-methane hydrocarbons. New mandates also call for reduced particulate matter (PM). John Deere's new propane engine—which reduces NOx emissions by half compared with a diesel engine and PM by more than 90 percent—is poised to meet these requirements.

John Deere estimates that 70 percent of the market for the propane tractor, once commercially available, will be in air-quality nonattainment areas like Dallas and Houston, for use in highway maintenance, industrial parks, golf courses, and off-road construction. The initial market thrust will likely be in Texas, California and Oklahoma.

The engine in this uniquely-designed tractor creates 50 percent less noise than diesel tractors. The tractor's propane components have been designed to be retrofitted into existing machinery with minimal changes.