While gas-powered string trimmers, also known as weed wackers, have long been a popular way to cut weeds for both commercial and personal landscaping, there has recently been a significant effort to reduce the pollution that string trimmers tend to produce. Many companies have begun to manufacture electric or propane-powered string trimmers in order to reduce their carbon footprint. However, there are both benefits and drawbacks to this development.

Gas-powered trimmers come in two major types: two-stroke and four-stroke. They are similar in that they require a mix of gasoline and oil for fuel; the main difference is in weight and eco-friendliness. Two-stroke gas-powered trimmers can be very cheap and light compared to other designs, but is not as green as the four-stroke model, which pays for that benefit by being quite heavy and costing more. Overall, though, gas-powered weed wackers are considered superior to other models when it comes to weed whacking. Unfortunately, despite advances in technology, they still produce a significant amount of noise and air pollution.

Electric string trimmers have become popular in recent years, both because of their lowered pollution and cheaper operating costs. The main distinctions made of electric trimmers are those which are corded, and those which are cordless. Corded models have the advantage of being cheap, light, and quieter than their gas-powered counterparts, but operators have found the power cord to be extremely limiting. Most corded designs have a limit of 100 feet of distance from a power source; a few allow 200 feet. While the cordless trimmer would appear to alleviate this problem, it also has significant limiting factors: the average battery life on a cordless electric design is 20 minutes per charge, and is also less powerful than a corded version, being suitable only to cut grass and light weeds easily.

The ideal string trimmer, then, would combine the cutting power of a gas model with the eco-friendliness of the electric design. Recent advances in fuel technology may have created just that. Propane weed wackers are the newest addition to the family, and only one company, has put a propane-powered model out on the market. However, since early 1999 when the propane-powered landscaping suite of lawnmower, leaf blower, and trimmer first emerged, the reviews have been sparse but promising, suggesting that it may in fact be able to make up for the deficiencies of electric power while producing far less pollution than gasoline. The use of non-refillable propane canisters, however, does significantly raise the price over the mechanism's lifespan.