Numbers Don't Lie: 71 Things You Need to Know About the World

by Vaclav Smil

The material’s environmental impact is another worry. Air pollution (fine dust) from cement production can be captured by fabric filters, but the industry (burning such inferior fuels as low-quality coal and petroleum coke) remains a significant source of carbon dioxide, emitting roughly a ton of the gas per ton of cement. For comparison, producing a ton of steel is associated with emissions of about 1.8 tons of CO2. Production of cement now accounts for about 5 percent of global CO2 emissions from fossil fuels, but its carbon footprint can be lowered by a variety of measures. Old concrete can be recycled, and the crushed material can be reused in construction. Blast furnace slag or fly ash captured in coal-fire power plants can replace some of the cement in mixing concrete. There are also several new low-carbon or no-carbon cement-making processes, but these alternatives will be making only small annual dents in a global output that is now surpassing 4 billion tons.