Next to water, concrete is the second-most consumed substance on earthon average, each person uses nearly three tonnes a year. Portland cement, the major component of concrete, is used to bind the materials that make up concrete. The concrete industry uses about 1.6 billion tonnes of portland cement and produces some 12 billion tonnes of concrete a year.The industry has a large ecological footprint: it uses significant amounts of natural resources such as limestone and sand, and depending on the variety and process, requires 60-130 kg of fuel oil and 110 kWh of electricity to produce each tonne of cement. In addition, the cement industry is second only to power generation in the production of CO2. Producing one tonne of portland cement releases roughly one tonne of CO2 to the atmosphere, and sometimes much more, and the cement industry accounts for 7-8 per cent of the planets human-produced CO2 emissions. Half of it comes from producing clinker (the incombustible remains of coal combustion), 40 per cent from burning fuel and 10 per cent from electricity use and transportation (Mahasenan and others 2003, WBCSD 2005).