We take cement for granted, which isn't surprising as it was developed by the Romans and is now the essential ingredient in our buildings, roads, tunnels, bridges, docks, airports and general urban development.

It is the key constituent in mortar and concrete and, once mixed with water, the chemical reaction ensures that it sets very hard over time and is then impervious to moisture. It becomes rock-like and durable.

We are fortunate that the basic raw material, limestone (calcium carbonate), is a very common sedimentary rock. Locally, the stone occurs in the Carboniferous limestone of Malham Cove or the Peak District. It is also found in the Cotswolds, the chalk of the Downs and the Chilterns - it is abundant.

It's just a pity that it is made up of the CO2 taken out of the atmosphere millions of years ago when the rocks formed from marine shells, and now we are getting it back when we don't need it.

Cement is manufactured by heating the limestone to over 1,000 degC to get quicklime and then crushing the resulting clinker and mixing it with gypsum. It is a well-understood process with two real problems for climate change.

The heating has to drive off CO2 and about half the amount added to the atmosphere comes from this basic chemical reaction and most of the rest from the heating, using coal, coke, waste and shredded tyres. The remaining ten per cent is from the quarrying and transport of a heavy commodity. Each tonne of cement produces one tonne of CO2.

Cement production is responsible for five per cent of the total global CO2 emissions and with the rising world population and economic growth this percentage will increase as the demand for cement continues to rise.

The three main producers of cement in 2002 were China, with 700 million tonnes, India, with 100 and the USA, with 91. Last year, China produced easily more than a billion tonnes and consumed 44 per cent of the world's production.

The UK produces about 12 million tonnes of cement a year and there has been some reduction in the CO2 produced as the industry has been using more waste in the kilns rather than coal and coke.

However, it is likely that the UK will see more production as wind turbines need concrete bases and access roads, and marine barrages and nuclear power stations are very greedy concrete consumers. Unfortunately, the plan to expand airports will also increase the demand, as will motorway widening, and the two million new homes which are to be built will need foundations, access roads and sewer pipes as well as new schools and hospitals.