Carbon concerns

Contractors can reduce the impact of their fleets on the environment. Photo: Grounds Guys Mowing is the most fundamental of all cultural practices. Regular mowing maintains an aesthetically appealing lawn and, when done properly, enhances turf density. Enhanced turf density has the added benefit of reducing runoff of fertilizers and pesticides and in general improving the environmental benefits of lawns. Now that we live in a new climate- and carbon-sensitive world we have to be mindful of carbon emissions from our mowers.

Grasses 
The first step to reducing carbon emissions might be to mow less. To mow less might require a shift in the types of grasses we grow, to species that require less mowing. We have grown accustomed to certain types of grasses, mostly due to the visual appeal. Few lawns receive the intense traffic of sports turf and therefore one must question why we have grasses that grow rapidly and require such frequent mowing. Can we get the look we want with less mowing?

There are alternatives such as the fine leaf fescues (red, chewings, hard and sheeps) that allow for an 80 percent reduction in mowing compared to any turfgrass mixture that contains perennial ryegrass and tall fescue. Kentucky bluegrasses require about 40 percent more mowing than the fine fescues and about 20 percent less than ryegrass and tall fescue.

Consider renovating some areas in the landscape to more slower-growing turf types. Of course there are trade-offs with some slower growing species relative to thatch production and visual quality.

Mow Differently
Mowing differently would require changing the fuel source we currently use to a source that reduces carbon emissions. Looking strictly at carbon emissions and efficiency, propane-powered equipment looks like a great option.

According to the Alternative Fuel Vehicle Institute, propane is the most widely available alternative fuel, with more than 3,400 fueling stations nationwide. Propane, which can achieve 90 percent of the fuel economy of gasoline, carries an octane rating of 104 to 112, and its total hydrocarbon emissions are 87 percent lower than that of gasoline.

As more managers continue looking for fuel alternatives, diesel-powered mowers are becoming more popular. They offer greater power and durability than gasoline engines and greater fuel efficiency. Compared to gasoline, diesel fuel burns more slowly and produces more power per gallon.

Diesel fuel contains much more energy than gasoline, resulting in less fuel use per hour of operation. Biodiesel fuel also can be used to power any conventional diesel engine, and it is a renewable fuel that is produced domestically.

The demand for greater fuel efficiency and lower emission levels has prompted manufacturers to offer improved engine designs. For example, incorporating electronic fuel-injection technology has enabled one manufacturer to reduce the fuel demands of one mower model by 20 percent.

The final aspect to mowing differently might include mowing pattern. Studies have shown that turning mowers consumes between 20 and 30 percent of the total fuel burned while mowing. Furthermore, there is evidence that increasing mowing speed, requiring the engine to be running for less time at full throttle, will also reduce fuel consumption.

A Toro study found mowing lengthwise compared to mowing at a 45 degree angle tripled the mowing time. Looking closely at these data indicates the increased fuel consumption is almost entirely explained by the amount of turning.
 

Putting it all Together
A recent study from the University of California-Irvine was corrected to reveal that lawns are a positive contributor to global warming. Additional studies from Ohio State University also indicate lawns are a positive contributor to carbon levels.

The largest single energy use and carbon issue associated with lawns is mowing. Addressing this issue proactively will not only shed a positive light on our industry, but will also lead to increased profitability in the future carbon economy.

The author is a professor of horticulture at Cornell University.