Community Landscape

Electric or Gas Leaf Blowers…Neither?

We are midway into autumn and most leaves have fallen down the deciduous trees. How are you managing your leaves this fall? Selecting the right strategy and equipment can minimize environmental impact.

Lawn care equipment can emit toxic gases

Gas powered leaf blowers and lawn mowers are more detrimental than one would think. Many consumer-grade blowers (and some mowers) use a two-stroke engine, which lacks an independent lubrication system, so fuel has to be mixed with oil. Burning oil and fuel emits a number of harmful toxic pollutants into the air, including carbon monoxide, nitrous oxides (which cause smog formation and acid rain), and hydrocarbons (a carcinogenic gas that also causes smog).

Surprisingly, the number of air pollutants emitted by gas-powered leaf blowers and lawn mowers exceed pollutant emissions of large automobiles, which are regulated to reduce and capture many air pollutants. A 2011 study showed that a leaf blower emits nearly 300 times the amount of air pollutants as a pickup truck. Similarly, a 2001 study showed that one hour using a gas-powered lawn mower is equivalent to driving a car 100 miles. Gas-powered leaf blowers and lawn mowers have the potential to cause serious environmental damage, so finding alternatives and utilizing best practices is key (Source: Washington Post).

In addition to air pollution, ozone is created when heat and sunlight react with nitrogen oxides and Volatile Organic Compounds (VOCs) that are emitted from combustion engines, including lawn equipment. St. Louis is among the top-ranked areas for ozone and particle pollution. In fact, according to the Clean Air Partnership, summertime ozone levels have exceeded federal-based health standards every year since the passage of the Clean Air Act. Therefore, small actions like seeking alternatives to standard use of lawn equipment can go a long way in improving regional air quality and human health.

Leaves aren’t litter!

According to the Xerces Society for Invertebrate Conservation, “one of the most valuable things you can do to support pollinators and other invertebrates is to provide them with the winter cover they need.” Leaving the leaves, either by mowing them into a thin layer of mulch on your lawn or leaving them whole on landscaped areas, is actually the best alternative for everyone!

Of course, this will require a shift in mindset, but it’s not out of reach. Here are some things to consider:

  • A thin layer of mowed/mulched leaves is beneficial for grass, as it cycles nutrients back into the soil. However, too much will damage or kill your grass – find the right balance!
  • Leaves are a great addition to compost. Bag or pile extra leaves near your compost pile, and add a handful or two every time you empty your food scraps. This helps the compost process, protects insects hibernating in the leaf litter, and also deters scavenger animals. Note that it is better to leave leaves whole (rather than mulch them) to protect overwintering insects.
  • Many of the insects we love and attract with native plants (like pollinators!) require safe habitat over the winter. The majority of butterflies and moths overwinter in the landscape (including leaf litter) as an egg, caterpillar, chrysalis, or adult. Some tuck themselves into a pile of leaves for protection. Others lay eggs in fallen leaves, which are also food when the eggs hatch. Some (like Luna moths and swallowtails) disguise cocoons and chrysalis as dried leaves, blending in with surrounding leaves. Bumble bees burrow under the ground and need leaves for extra protection from the cold. Other leaf-dependent animals – spiders, worms, beetles, millipedes and more – are necessary food sources for chipmunks, birds, and amphibians.
  • Leaves are free mulch, protecting perennial plants, especially those that sprout early. Consider piling leaves on empty vegetable beds or perennial beds, or around the bases of trees to protect from cold and keep in moisture. They also keep weed seeds from sprouting.
  • However: thick leaves on the sidewalk can be a hazard. Kindly relocate these to another landscape to avoid creating a slippery surface as they decompose.
  • In the spring, after the last frost, you can compost any remaining leaves as needed.

What can individuals do?

Your approach will be different according to your circumstances. For the best environmental outcomes, prioritize leaving leaves, moving leaves to preferred areas, using for compost, or mowing and leaving on the lawn. If collection or removal is required, consider the options for your best tool options.

For both year-round lawn care and raking, consider non-motorized options! Emission-free, non motorized push mowers and “old-fashion” rakes are very manageable for small yards, or ambitious individuals with medium or large yards. For smaller landscapes it may be possible to switch to an emission-free, non motorized push mower. Push mowers are solely operated by the user pushing the lawn mower across the yard, meaning it emits absolutely zero pollutants.

manual push mower

If you are going to opt for some motorized support, switching to electric alternatives can drastically reduce the number of toxic pollutants directly released into the air. While electric models do not eliminate your contribution to greenhouse gasses, it shifts combustion to power plants. Power plants are equipped with scrubbers that filter out pollutants, sharply reducing the overall amount of air pollution being released when fossil fuels are burned.

Time of day matters too. According to the St. Louis Clean Air Partnership, if you are using a gas lawn mower, mow before 10 a.m. or after 7 p.m. to avoid peak ozone formation hours.

What is WashU doing to minimize the impact of lawn care equipment?

WashU has also recognized the need for a shift away from gas-powered leaf blowers and lawn mowers and has taken major steps to make landscaping and lawn care more environmentally friendly.

All lawn equipment used by WashU meets current EPA regulations. The lawn mowers used throughout campus are all propane-powered to reduce emissions, with very minimal use of gas-powered units (for example, when propane units are being serviced). The line trimmers and blowers used are all 4-stroke equipment, which is significantly better than the 2-stroke engines found in most gas-powered leaf blowers. Four-stroke engines offer more complete combustion and produce less air pollution. In addition, the oil used in the 4-stroke engine is a higher quality synthetic oil which can be mixed at a thinner rate (80:1) and ultimately burns clearer. Equipment is maintained on a regular schedule to keep everything operating at peak condition. Additionally, leaves are mulched over with propane mowers as often as possible to reduce the use of leaf blowers, while adding organic matter back into the soil. 

While the 4-stroke engines are currently more effective for larger landscapes, WashU has been experimenting with battery-powered equipment since 2018. Switching over equipment is a big expense, and the technology for commercial grade battery-powered is not yet proven (though it is improving!). Equipment currently being tested includes a push mower, line trimmers, and leaf blowers.

Thank you to the Focal Pointe Outdoor Solutions team for providing updates on WashU’s current landscape practices. Focal Pointe provides the landscape maintenance services on WashU’s campuses.