Diesel tops the list of alternative fuels to power mowers

Snapper Pro’s S175x Yanmar diesel mower is available in 52 and 61-inch cutting widths.
Photo Courtesy of Snapper Pro.

From solar to hydrogen to natural gas to electric to biomass, there are plenty of new fuel technologies being developed as “alternative” energy sources. One of the most popular options for those looking to get away from gasoline, however, is an alternative fuel that’s been around for more than a century: diesel.

Diesel is a popular option for lawn care professionals looking for a mower with added power and long engine life.
Photo courtesy of Toro.
Cub Cadet offers its TANK S series in both diesel (shown here) as well as liquid propane models, allowing lawn care companies to select the fuel type of their choice.
Photo courtesy of Cub Cadet.
The Ferris IS5100Z is approved for use with B20 biodiesel. Diesel mowers provide greater torque than gasoline units, allowing them to power through heavy cutting situations, says Roy Dust, product specialist with Ferris.
Photo courtesy of Ferris.

When Rudolf Diesel first developed the pressure-ignited engine that now bears his name in the mid-1890s, diesel looked to become the mainstream power system of choice. Gasoline engines soon sparked to life, however, and took over much of the automobile market. Diesel has remained the fuel of choice in larger tractors, trucks and construction equipment, and it’s now finding its way into smaller equipment, like zero-turn mowers.

“Diesel is really emerging as the most viable alternative for landscapers, in our opinion,” says Ray Garvey with Grasshopper. “It’s the one alternative that reduces fuel consumption, reduces emissions and, at the same time, increases productivity.” He notes that the third factor, productivity, is critical to ensuring an alternative fuel is not only environmentally sustainable, but also financially viable for those operating lawn care businesses.

Diesel has other advantages going for it, too. For starters, it’s readily available. “It’s also a very safe fuel to handle,” says Garvey.

Most importantly, from a power perspective, “Diesel fuel, drop for drop, has about 30 percent more energy than gasoline and more than 40 percent more energy than liquid propane,” says Garvey. “That power is captured through pressurized combustion rather than spark ignition. That concept creates a lot of additional power.”

So, why hasn’t diesel always been the fuel of choice when it comes to commercial mowers? Garvey says the vibration present in smaller equipment has traditionally been one of the factors that’s limited the use of diesel engines in lawn mowers. “Most manufacturers in the past who have tried to utilize diesel in smaller equipment, such as zero-turn mowers, have simply replaced a gas engine with a diesel engine, and that led to all sorts of problems in trying to capture the power of diesel,” he explains. Grasshopper has addressed those challenges by designing a special “Smart Frame” around its MaxTorque diesel engines and uses other anti-vibration technologies to better channel the power of diesel to the mower. Garvey says the MaxTorque diesel mowers also reduce emissions, in part by simply providing more power and allowing the operator to get the job done more quickly. “The engine is running less on any given task, and thus, consuming less fuel,” he explains.

Garvey adds that the engines feature a “clean diesel” technology that produces a more thorough burn of the diesel fuel and reduces emissions. “There’s a misperception of diesel being a black smoke, dirty fuel, but within the last 10 years, 99 percent of all the black carbon diesel emissions have been eliminated and sulfur has been virtually eliminated from diesel fuel. So, diesel is really a very clean fuel these days.” In fact, Grasshopper reports that the MaxTorque diesel line already exceeds Tier 4-1 emissions standards, and the engines can save up to 700 gallons of fuel versus gasoline or liquid propane mowers over 1,000 hours of run-time.

Grasshopper recommends that B5 (the number refers to the percentage of biodiesel mixed with petroleum diesel) or lower be used in its diesel mowers. “That’s really because the biodiesel industry doesn’t yet have consistent standards, but as that industry continues to grow and standardize, I think that biofuel mix is going to increase,” says Garvey. He says that lawn care professionals switching to diesel zero-turn mowers will likely be surprised by two factors. “First, they’re going to see the amazing amount of power that diesel provides, and second, at the end of the job they’re going to be amazed by how little fuel was consumed.”

Environmentally focused lawn care companies are just one group looking to switch to diesel mowers these days, says Roy Dust, product specialist with Ferris Industries. “Interest is definitely up from where it was five years ago. Some people are interested because they are eco-friendly, but the majority of people that I’ve worked with are looking into diesel mowers for their longevity and fuel economy.”

The Ferris IS5100Z, powered by a 33.5 hp Cat diesel, is now approved for up to B20 biodiesel fuel. “My experience does show that biodiesel will not produce quite as good fuel economy as conventional diesel, and there also seems to be a slight power reduction from biodiesel,” explains Dust. Performance in both areas should still far outpace gasoline engines, he notes, so those tied to the idea of using biodiesel should still be pleased with the results.

Check with the manufacturer of your particular diesel mower to see exactly what level of biodiesel is approved in your model. Scag, for example, offers its Turf Tiger with both a 25 hp Kubota diesel engine approved for use with B5 fuel, and with a 28 hp Cat engine rated for up to B20. Exmark offers a diesel zero-turn that’s approved for use with B20 biodiesel.

Grasshopper says that its MaxTorque diesel features decreased vibration and emissions, leading to increased productivity for lawn care professionals.
Photo courtesy of Grasshopper.
Toro Z-Master mowers manufactured after 2008 can be used with biodiesel up to B20. The company offers a conversion kit to support biodiesel use with earlier models.
Photo courtesy of Toro.

Toro is one company that’s long worked to meet the needs of lawn care operators wanting to use biodiesel, even in older mowers. For example, the company began approving the use of biodiesel up to B20 in its diesel Z-Masters as early as 2008. The company also introduced a kit for those wanting to use biodiesel in mowers manufactured in 2007 and earlier. “Our biodiesel readiness initiative represents The Toro Company’s continued commitment to exploring and developing innovative solutions that meet the needs of our customers while protecting the environment,” the company stated at the time.

Dust says that sky-high gas prices a few years back really spurred interest in diesel mowers, and despite the higher purchase, there has continued to be demand even during the economic slowdown that followed. “You have a higher purchase price with a diesel mower, but you have a much lower operating cost,” he explains. “Especially for those people who do long-term planning, when they start putting pencil to paper, they realize that the lower day-to-day operating costs, combined with the longer life of the engine, make a diesel mower worth the investment.”

Dust says that, from a servicing standpoint, “there is a totally different requirement for internal diesel maintenance,” but also notes that “most of the diesel engines that are available on the market are really good quality, not just commercial, but industrial-grade.” There’s typically not much work to be done inside diesel engines, so most maintenance is on external components (electrical, alternator, water pump, etc.).

Operating a diesel mower is similarly straightforward, says Dust. “You usually have some sort of a pre-heat that you should use every time you start the machine, and particularly in cold conditions,” he explains of the only real difference for those accustomed to gasoline models.

During use, diesel mowers will display more torque than a comparable gasoline engine, according to Dust. In truck applications, that extra diesel torque makes for improved pulling power. In a mower, he explains, “the torque means that the mower won’t bog down as easily. It’s more able to power its way through a heavy cutting or uphill situation.”

Dust says the majority of lawn care companies he’s worked with that have purchased diesel mowers have purchased at least enough mowers to support one entire crew. “The biggest problem is when you have one crew running different types of machines. Sooner or later, someone is going to put the wrong fuel in the wrong machine,” he explains. “If you pour diesel into a gasoline engine, it won’t run well, but it’s not too big of a deal. If you poor gasoline into a diesel engine, it’s a huge deal.” Diesels typically have a yellow fuel cap in order to help prevent such a mistake.

In general, those in the lawn care business are already used to using diesel in other types of equipment or vehicles, so the move to powering mowers with this “alternative fuel” usually doesn’t seem very daunting. “Propane is gaining ground, but diesel is still far-and-away more popular than propane,” says Dust. “I think there’s just a higher comfort level with diesel.”

Baker Landscaping has retrofitted this mower to run on propane instead of gasoline with a conversion kit by Heritage Propane.
Photos courtesy of Heritage Propane.

Options Galore

They say there are 1,000 ways to skin a cat. There may not be quite that many ways to power lawn mowers, but the scope of alternatives to gasoline certainly is growing. In addition to the increased use of diesel highlighted in the accompanying article, the green industry is embracing the use of propane in mowers and other equipment.

Jim Coker, president of Heritage Propane, is doing everything he can to educate lawn care companies, equipment manufacturers and others on the benefits of propane power. Conversion kits are available to change over many gasoline mowers to use with propane, and many mower manufacturers now produce propane-powered mowers available directly from dealers. “As I travel the country and talk to dealers and ask them about alternative fuels, they often don’t recommend them because they don’t know how to work on them,” he says. He urges manufacturers and distributors to offer more education and support for dealers in this area. For Coker, the lawn and garden industry is the perfect venue to reduce reliance on foreign oil and take advantage of a fuel source, propane, that has much lower emissions and is available here in the U.S.

Heritage Propane, through the MetroLawn program, offers training for lawn care pros, a choice of easy delivery options and even provides a propane canister exchange service to help reduce the upfront costs of those switching over to propane mowers. At GIE+EXPO in late October, Heritage Propane is joining forces with Roush, Alt Fuel, Envirogard, Manchester Tank and others in a single booth to provide answers to any questions lawn care professionals might have about using propane in their equipment. “We’re going to provide information for all their vehicles, their mowers and their hand-held equipment,” explains Coker.

One very recent development is the introduction by MetroLawn of refillable (rather than throwaway) canisters to power hand-held equipment. There are some propane-specific models of hand-held equipment on the market from companies like Lehr, and Coker says that Alt Fuel now offers the ability to convert any four-stroke power equipment over to propane use. Onyx Environmental Solutions (Envirogard) was a pioneer in such conversion kits for lawn mowers, and that continues to be a popular approach for those with existing gasoline mowers wanting to make the move to propane.

Cub Cadet offers its TANK S series commercial zero-turn mowers in diesel, as well as liquid propane configurations. “The benefits of liquid propane go far beyond reduced emissions and offer lawn care professionals longer engine life, longer run times and less engine maintenance,” the company states. “Additionally, Cub Cadet’s TANK S LP meets all current EPA and CARB emissions standards making it the perfect energy efficient solution for green industry professionals. With the TANK S LP, professionals will reduce their carbon footprint and save on fuel costs since liquid propane is, on average, 30 percent less expensive than gasoline and diesel.”

There are other alternative fuel mowers also on the market. For example, Dixie Chopper introduced the world’s first CNG (compressed natural gas) zero-turn in 2009, and not long ago, Hustler unveiled the first electric-powered zero-turn. In the residential sector, there are even solar-powered mowers, perhaps a sign of yet another alternative fuel source that might someday be available to the pros.

Patrick White is a freelance writer and editor who has covered every aspect of the green industry in the past 13 years. He is based in Middlesex, Vt., and is always on the lookout for unusual stories.