Unless environmentally friendly businesses make your trimmer line, the answer is a no. Mower strings, on the other hand, are single-use plastic — a source of pollution that few people are aware of. Trimmer strings will disperse into small plastic bits during operation. And these fragments will be mixed with your plants and soil. Unfortunately, most mower lines are composed of durable plastic that can take thousands of years to degrade completely. Choose a trimmer line with high durability if the environment is a concern. It contributes to reducing the number of times they break and emit plastic into the environment. A string from a biodegradable brand would also be wonderful.