Providing sanitation, housing, food, refrigeration and indoor fires for cooking takes energy, as do the pumping and purifi cation of water and the desalination of seawater for irrigation.

• （假如卫生、住房、食物、制冷以及烹饪等室内用火需要能源的话，那么抽水、净化水以及将海水脱盐以供灌溉也同样需要能源。）