Compostex compost cover is a completely breathable, non-woven fabric made of 100% UV-resistant, black polypropylene that completely sheds rainfall from covered piles or windrows. It is 1.7mm thick and will be usable for at least 5 to 10-plus years (depending on climate conditions and whether you leave it in the sun, when not in use). Compostex maintains the optimum level of humidity throughout the composting process by accelerating the evaporation of excess water from the pile. It is completely permeable to oxygen, carbon dioxide, and water vapor. In wet weather, Compostex ensures surface runoff of up to 100% of rain and snow melt. In dry weather, it reduces moisture loss by protecting the covered materials from the drying effects of sun and wind. The cover will also protect the pile from windblown weed seeds, flies and scavenging animals.