Watch Out Diesel: There’s a New Fuel in Town
Dave Dolan of Flying Rabbit Farm creates syngas out of locally produced grass pellets.
“VRRRRRRRMMM….” As the engine on Dave Dolan’s tractor sputtered to life, I stood by, watching Dolan scurry around the machine, turning knobs and flicking switches. Puffs of smoke emerged from the complex fueling system handcrafted for this tractor, which isn’t powered by conventional fuel; it’s powered by grass.
Dave Dolan, owner of Flying Rabbit Farm (a small, family-run farm in Otego, NY) has always been a proponent of utilizing alternative fuel sources. A few years ago, Dolan pursued his first SARE grant, attempting to create a flame weeder powered by waste vegetable oil (see the SARE column in SFQ Fall 2010). For the past four years, Dolan has been using a biofuel-powered boiler to heat his home, experimenting with a wide range of fuels, from wood chips to rye seeds (which he refers to as “God-made pellets” due to their size and shape), in order to determine the most fuel-efficient form of biomass.
The SARE Project
For Dolan’s most recent SARE-funded farmer grant, he explored the feasibility of transforming grass pellets into a usable fuel that could power his farm equipment, a topic on which he could find little prior research. His inspiration came from the arrival of a grass pellet manufacturing facility, EnviroEnergy LLC, just four miles up the road from his family’s farm. This source of grass pellets right in his backyard was the perfect motivation because it allowed him to explore using a truly local, renewable resource.
Dolan’s gasifier loaded with grass pellets, ready to start producing syngas. All photos by Rachel Whiteheart
Dolan, with the aid of his son and his nephew, soon set to work engineering a gasifier that could chemically transform grass pellets into another type of fuel called syngas, which is essentially just a gas form of any hydrocarbon fuel (coal, oil, etc.).
The building of the gasifier was a family affair; Dave Dolan and his son were joined by Dolan’s nephew, a chemistry major (Dolan’s wife stayed out of it due to, in Dolan’s words, “a fear that [they] were going to blow [themselves] up”). Dolan’s nephew helped ensure that the chemical and thermodynamic logistics (pressure, temperature, and volume of each chamber, gas compositions, etc.) were properly accounted for in the design of the gasifier. Dolan also turned to the Internet for further design tips.
Once Dolan had decided upon a general design for the machine, the entire Dolan clan set to work building the gasifier. After a grueling design process consisting of 15 different prototypes, they had their final product. The resultant gasifier consisted of a series of metal barrels (the purpose of which will be described later), each one sealed to create a pressurized environment. Each metal barrel is connected to the next via a series of tubes that allow the syngas to flow throughout the apparatus.
Results
I was lucky enough to venture out to Flying Rabbit Farm and see this device in action. As I pushed thoughts of exploding tractors out of my mind, Dolan poured two medium-sized buckets worth of grass pellets into the gasifier, an amount of fuel that can produce gas for up to 4 hours. He then sealed up the system, igniting a fire in the tank and commencing the gasification. The grass pellets burned in the first tank, giving off a very crude syngas that passed through a series of filters and barrels, each one purifying the gas more. This is so that it can run more smoothly through the engine, although Dolan lamented that “the syngas still contains a little tar which can clog [it] up.”
When the temperature in the first tank had reached 650°C (the temperature at which the gasifier starts to produce the purest form of syngas), Dolan sprinted along to the far side of the tractor, firing up the 3 cylinder diesel engine on his tractor. We all waited with anticipation until we heard a quick sputter of the engine, signaling that the syngas was working. Dolan has attempted to use his gasifier to power other machines on his farm, but as of now, the only machine it powers efficiently enough is his diesel-fueled tractor. In addition to using the pellets to make syngas, he has also started burning them in the biomass boiler that powers his home. He says grass pellets burn a little less cleanly than other biofuels that he has used in the past, but the ash that results as a consequence of burning can be used as a fertilizer which acts very similarly to lime.
Biochar is a by-product of the gasifying process and can be used as a soil amendment to enhance crop growth.
The gasifier also produces the useful byproduct biochar. Dolan has been using biochar, which is essentially charcoal, on his crops as a soil amendment. In a series of experiments Dolan conducted in his greenhouse, he determined that a mixture of 90% potting soil and 10% biochar enhances the health of his crops more than un-amended potting soil would. And as if healthier crops weren’t enough of a benefit, by returning the biochar back to the earth, Dolan further diminishes the environmental footprint of this fuel source.
Dolan’s device is still too cumbersome to be attached to a portable tractor, so he’s not sure whether it would be feasible for other small farmers in the area to develop any sort of similar apparatus. But for now, Dolan has determined that turning grass pellets into syngas is possible, even if you don’t have access to extensive amounts of technology. Dolan is grateful to SARE for providing the support that he and other entrepreneurial farmers need because, as he says “the creative genius residing in farm shops across the countryside is immense.”
If you’d like to see the gasifier in action, view the YouTube video that Dave Dolan created.
This article discusses SARE project number FNE11-713. Download the full final report.
