Kelp has a high rate of growth and its decay is quite efficient in yielding methane, as well as sugars that can be converted to ethanol. It has been proposed that large open-ocean kelp farms could serve as a source of renewable energy. Unlike some biofuels such as corn ethanol, kelp energy avoids "food vs fuel" issues and does not require irrigation. Seaweed may prove a viable future biofuel especially if harvested in summer. However the suitability of its chemical composition varies on a seasonal basis. Harvesting the kelp in July when carbohydrate levels are at their highest would ensure optimal sugar release for biofuel production.