As we saw in Chapter 1, it is likely that we will face a difficult state of affairs in the 21st century, caused by the three-pronged crises of depletion of oil resources, global warming, and massive generation of wastes. In the previous two chapters, we examined the use of energy for activities in transportation, homes and offices. Clearly there is still plenty of room for improving the energy efficiency of the “daily life” activities that make up half of the total human consumption of energy. Improvements in energy efficiency help us to solve the problems of oil resource depletion and global warming. How can we address the problem of massive generation of wastes? One way is to construct a material-recycling society where waste materials are recycled into new products through the human activities of “making things.” However, because one half of the energy is consumed in “making things.” if recycling consumes too much energy, we will end up undoing all that we have achieved through improvements in the energy efficiency of “daily life” activities. Therefore, what we must do first is determine whether recycling with high energy efficiency is possible.