Gas-powered lawn mowers are almost as bad for the environment as gas-powered cars, and just like cars, the bigger the mower, the bigger the carbon offender.

Now a Colorado-based startup is experimenting with commercial-grade electric mowers that not only produce no carbon emissions, but can run on their own. No rider necessary.

Scythe Robotics' autonomous electric mower can run for 8 to 11 hours at a time, depending on the grass length.

But the mowers are not for sale to consumers, or anybody else. Instead the company leases them to landscaping companies, which are charged for the acreage that the machines mow. That makes it much more attractive to the companies because these machines typically last only two to three years.

 "We enable the landscaping industry to transition from gas to electric mowers by using autonomy to sneak that technology in and eliminate the emissions with a different business model," said CEO and cofounder Jack Morrison.

"What we heard from a lot of landscapers early on was that they were tired of becoming what they call the 'iron collectors,' where they just end up with scrap heaps of broken down machines," said Morrison. "Every time we make the machine faster or make it last longer, Scythe benefits and so do our customers."

Clean Scapes, a commercial landscaping company in Texas, had converted its entire riding fleet to natural gas and propane about a decade ago because it burns cleaner. Now it is experimenting with Scythe mowers. 

"The leasing model gives us the flexibility to measure it up against how we normally operate and to really work with it as we learn and develop the, kind of, AI and the technology and work it into our operation," said Damian Matherne, CFO of Clean Scapes.

The mowers appear to be careful with surrounding objects. Two of them rolled across a park recently in downtown Austin, stopping automatically when dogs ran across their paths.

Beyond electrification's effect on carbon reduction, Morrison claims that the self-driving aspect of the mowers also benefits the planet. If a person doesn't have to spend hours mowing lawns, they have more time to do other landscaping work. That ultimately will lower the cost of maintaining outdoor spaces, helping to cultivate more green space, which in turn cools cities, he said.

Scythe Robotics is backed by True Ventures, Inspired Capital, Zigg capital and Lemnos, with total funding at $18.6 million. Morrison also said that tax breaks in the recently-passed Inflation Reduction Act should benefit the growth of his startup.

CNBC climate producer Lisa Rizzolo contributed to this piece.