Humanity's use of materials is immense and growing. The energy required to make these materials, and the carbon emissions associated with this production, are also huge, consuming 15% of the total global primary energy per year and responsible for a similarly large proportion of anthropogenic carbon emissions.
This chapter summarizes the orders of magnitude of the flow of materials, energy and water that material production entails. The growth in demand over time is approximately exponential, meaning that consumption grows at a rate that is proportional to its current value - for most materials it is between 3 and 6 % per year. Exponential growth has a number of consequences. One is that consumption doubles every years, where is the growth rate in % per year. It also means that the total amount consumed (the integral of the consumption over time) also doubles in the same time interval.
There is a tight coupling between materials, energy and carbon in today's economy. Energy is needed to make materials. Materials are needed to make usable energy. Water is needed for both. Emissions are unavoidable if materials are made and energy is used. The chapter sets the scene for a fuller exploration of this coupling later in the book.
