Since these alternative sources of energy come from crops, the amount of carbon dioxide released by burning them is the same as is absorbed from the atmosphere during photosynthesis. No excess carbon is produced or released, so it's considered a clean, environmentally friendly energy source for a low-carbon era.
由於這兩種替代能源均以農作物為料源，燃燒過程中排放的二氧化碳，就是作物進行光合作用時從空氣中所吸收的二氧化碳，並沒有額外製造或釋放，因而在低碳時代被視為友善環境的潔淨能源。