Student’s Robotic Mower Reaches Far Beyond the Lawn

Spring comes soon, and with it the pleasures of lawn mowing — the smell of cut grass, the fresh air, the communing with nature.
Or maybe you don't find it so pleasurable. Mason graduate student Jason Force certainly doesn't. Even worse, he says, is the practice of bagging grass and throwing it in a landfill. So he designed an easier, greener way to mow.
Force, who received his BS in electrical engineering from George Mason University in 1996 and is currently working on his master's in electrical engineering at George Mason, has come up with a concept for the E-mow Harvester. This self-navigated, robotic mower operates much like the popular Roomba vacuums that propel themselves through your house and suck up dirt. But imagine if, instead of running on batteries, your Roomba ran on dirt itself. That's the concept behind the E-mower, which uses grass trimmings for fuel.
"You tell it where you want it to mow, press go, and it just goes," Force explains. "You have to preload some grass pellets into it at the start, but then the machine makes the pellets all by itself."
The E-mower prototype consists of a guidance development vehicle Force created out of an electric hobby truck. He's also devised a biomass gasifier, engine, air filter and a fuel gas mixer assembly, and is trying to secure funds to build a complete fuel system for this complicated, and expensive, machine. The finished product will include an onboard computer, GPS system and grass "pelletizer" in addition to an engine, water extractor, rotary drier and other parts.
Users simply download a property overview from Google Maps. They select a plat file, overlay that on the picture of their yard and then input any obstacles the machine might encounter. An internal GPS system locates roads, sidewalks, driveways and other visual boundaries.
The E-mower cuts grass using a covered, nonkinetic electrical bar cutter instead of a rotary blade, which improves safety. A pelletizer uses high pressure and temperatures to form the grass cuttings into pellets. A gasifier reactor converts the pellets to fuel gas. The fuel is filtered, cooled and mixed with air before it is used in an engine to create shaft power. An internal alternator generates power for onboard electrical components.
But mowing is only a part of it.
Since the E-mower uses only 20 percent of grass fuel for itself, 80 percent could be stored in bins in users' yards to heat their houses. Those on large tracts of land who would generate more than they could use on their own would be able to sell leftovers "to city friends who don't have enough land to heat their houses," Force says.
But think bigger.
"The obvious consumer is power plants," he says. "On paper I can actually generate biomass cheaper than the natural gas equivalent. But I have to convince someone I have a real product and can actually make this work in a real business sense."
Grass fuel pellet companies operate today, often collecting low-grade hay from farmers for $60 a ton, Force explains. They process it in large, centralized plants and sell it for $200 a ton. Force's harvester would cut those production, transportation and processing costs by generating pellets right in the field. "And if your power plant is nearby," he says, "the robots could actually deliver the product too."
Since it's difficult to convince large power utilities to switch from natural gas to "natural grass," Force is targeting rural utilities in areas without gas pipelines and hopes to work his way into foreign markets in need of sustainable energy.
And think bigger still.
The potential global impact of the product is huge, particularly for developing countries. A harvester such as this could supply an entire region with electrical power, crop utility functions, and water pumping and purification systems. And because turnaround is quick, sustainability is vastly improved over other biomass products. While forestry waste and sawdust from sawmills is now used to create wood pellets on every continent, "they don't have the forestry to generate the wood required," Force explains. "And the cycle time for wood is 40 years; the cycle time for grass is 40 days."
Force created the core reactor for his mower in George Mason's machine shop and, thanks to guidance from Startup Mason and the Mason Center for Social Entrepreneurship, he's excelled in numerous pitch contests, plan competitions and incubators. These included the prestigious Ballston Bid LaunchPad competition in which the E-mower was chosen as one of 14 finalists among 200 entries.
Force recently partnered with a cofounder for his company, and he has applied to Mason's Patriot Green Fund for assistance in building a complete fuel system for the device. The Green Fund has "been very helpful in connecting me with people and organizations oriented towards sustainability. Their connections and advice have helped me adjust my business plan," Force says. "The support infrastructure at Mason has been incredible."
A version of this story appeared on Mason's Newsdesk on January 22, 2014.
Write to Cathy Cruise at