Emissions regulations have eliminated noisy and polluting two-stroke engines from most applications, but these engines still dominate in lawn equipment like string trimmers (aka weed eaters, weed whackers, line trimmers, weed whips) and leaf blowers. Lehr, a startup based in Los Angeles, has developed a cleaner and quieter alternative--small engines that run on 16 ounce propane canisters used for camp stoves.

Earlier this year, the EPA gave Lehr its Clean Air Excellence award for technology that produces 97 percent less particulates and 96 percent less carcinogens than gasoline engines. It also surpasses emissions standards for carbon monoxide by 75 percent and for hydrocarbons by 65 percent, emits less of smog-forming nitrogen oxide, and is 35 percent more efficient, reducing carbon dioxide emissions. And it's quieter--it can be used comfortably without earplugs.

Watch Bernardo Herzer, the founder and CEO of Lehr, describe the technology and demonstrate two of Lehr's products.