Science Spotlight: Methane Tractor

The garage sits on the edge of the fields to the west of campus along Rte. 125. “Henry” the tractor is parked inside.  The years have only slightly tarnished the fire-truck red paint job on the 1950’s Ford 8N. It was the top selling tractor in North America in its day, the “tractor that replaced the horse.”

The tractor was originally repurposed to run on hydrogen gas fuel in the spring of 2008. It was the brain-child of Dick Catlin ’56, a businessman, and Mark Benz ’56, a former engineer with General Electric. They worked with four students over the course of the 2008 spring semester to develop a tractor engine to run on gaseous rather than liquid fuel. Associate Professor of Physics Noah Graham was on board as an advisor.

“I act as a sounding board,” Graham said. “Each week the team would present to me, and I’d give them feedback, try to find holes in their proposals, help them clarify their ideas.”

Last year, after a four year hiatus from the project, a Winter Term class took the 2008 product – an engine that would turn over with hydrogen fuel and run roughly on propane gas – and further refined it with the assistance of mechanics at Champlain Valley Equipment in Middlebury. But one of the major problems with hydrogen is storage and accessibility. The initial thinking was that farmers could generate their own hydrogen fuel using a windmill to generate the energy necessary to split water. They would then use the hydrogen fuel to power their tractors. But a large tank of hydrogen would only run the tractor for about 20 minutes. So this year’s team has begun to explore an alternative fuel: methane.

Henry Philip ’13, a Physics major who has been working on the project for the past year and heads up the student team, explains that “the drive to use methane over hydrogen is mostly practical. How could a farmer get the fuel? They could make hydrogen. But they already have access to methane. What we’re trying to do is create a tractor where the farmer has complete control over the fuel supply and its price.”

Numerous dairy farmers around Addison County already use manure digesters to convert cow manure into fertilizer. A product of this process is methane gas. Some farmers burn the methane to generate electricity that they pump back into the grid. But could it be used as a viable fuel for farm vehicles, instead?

That’s what Benz, Catlin, Philip and seven other students are working to determine this Winter  Term in INTD 1138: Methane as an Alternative Fuel for Agricultural and Transportation Applications. The challenges are two-fold. First, they are struggling with the fuel delivery system. According to Philip, each fuel injector (of which there are two) delivers fuel to two cylinders in the four-cylinder engine. Ensuring equal fuel levels in each cylinder has proved to be a headache. The timing is also difficult. The team is working to optimize engine performance by finding the right balance of methane fuel and air. A huge component of that is determining how much time each fuel injector should be open, letting methane into the cylinder.

The other problem with methane fuel is storage. The sizable tank currently strapped to the back of the tractor could run the tractor for an hour, estimates Philip. But ideally, the tractor could run for much longer on a single tank.

“It’s borderline practical to compress the methane and run [the tractor] off of compressed methane,” he said. “There’s some potential in liquid storage, but an issue is the amount of energy it takes to pressurize methane to keep it in liquid form. Another potential alternative is storing it on metal hydride — storing the gas molecules on a metal that are released when heated. The Department of Energy has gotten the concept to work with hydrogen. But not yet with methane.”

So for now, compression seems to be the best bet.

But the potential benefits — both economic and environmental — of a methane-burning tractor are well worth the effort of trying to solve these problems. If dairy farmers could use methane extracted from their own cow’s manure, they would cut fuel costs and have complete control over their fuel supply; an attractive option. Furthermore, the EPA estimates that the global warming potential (GWP) of methane is over twenty times greater than that of CO2 when not burnt as a fuel. And on the flip side, methane produces less CO2 when combusted than conventional diesel or gasoline fuels. By burning the methane, the farmers directly reduce their atmospheric impact on multiple levels.

The class of eight — first years and seniors, English and Physics majors — spent the first week of this winter term intimately acquainting themselves with the inner workings of the tractor. They are dedicating this week to examining the practicality of methane and natural gas as a fuel source. Next week, they’ll spend time on farms around Addison Country asking the question: how can this be feasible for local farmers?

“We’re trying to improve the economics and sustainability of farming. What’s great about the methane is that it brings [the fuel supply] back to Addison County, back to Middlebury,” said Philip.

By the end of Winter Term, the class hopes to have determined whether it is feasible for dairy farmers to fuel their tractors with methane produced from manure. In the future the Green Engineers, a student group on campus, hopes to continue to refine this process with the hope of helping develop methods for farmers in Addison County to become more environmentally and economically sustainable.