Cattails use some pollutants as nutrients. Cattail farms near sewage treatment plants could clean troublesome nitrogen and phosphorus from effluent. Unlike nuclear power and fossil fuels, cattails do not add heat and carbon dioxide to the earth but recycle them. The plants use the sun's energy and the atmosphere's carbon dioxide to produce starches and sugars through photosynthesis. This heat and gas are returned to the cycle when the cattails are used as fuel.
Wetlands are extensive and largely unused.
According to one estimate, the United States has 140,000 square miles of wetlands from Alaska to the tip of Florida. Minnesota is estimated to have 10 million acres where cattail could grow, which theoretically could supply enough of them to meet the state's entire energy needs. Harvesting cattails in strips is compatible with preservation of wildlife and makes replanting unnecessary. Cattails spread with underwater stems called rhizomes and each year can recover the harvested strips. Cattails are an annually renewable resource, whereas coal, oil and peat take thousands or millions of years to form.