Fields of green plants are giant solar collectors. Growing plants remove CO2 from the air, water and other nutrients from soil in the presence of sunlight to produce energy rich carbohydrates. Plants store carbohydrate carbon in leaves, stems and seeds above ground which are easy to harvest for fuel. Plants also store carbohydrate carbon in roots below ground and, over time, in soil as roots decay. In some plants about half the CO2 removed from the air is used to grow roots. Many perennial plants grow more roots than leaves, stems and seeds thereby injecting more carbon into the soil. If the soil remains undisturbed much of the carbon stays there. The land becomes a carbon "sink."
Growing and using plants for fuel offers ample "low tech" safe, reliable renewable energy and cleans the air at the same time.