Letter: Better ways of making use of carbon dioxide (1)

From Martin Pitt, Leeds, West Yorkshire, UK

Michael Marshall suggests we can capture carbon dioxide from the air to make building materials by reacting it with calcium oxide to form calcium carbonate (17 March, p 34). Surely it would be better to capture the CO₂ in a more concentrated form from the chimneys of lime kilns, where calcium oxide is produced by decomposing calcium carbonate. This involves lots of energy – generally from fossil fuels.