The carbon capture con

Carbon capture and storage (CCS) tops the list of silly schemes "to reduce man-made global warming". The idea is to capture carbon dioxide from power stations and cement plants, separate it, compress it, pump it long distances and force it underground, hoping it will never escape.

Smart engineers with unlimited money could do all this. But only green zealots would support the sacrifice of billions of dollars and scads of energy to bury this harmless, invisible, life-supporting gas in the hope of appeasing the global warming gods.

The quantities of gases that CCS would need to handle are enormous and capital and operating costs will be horrendous. For every tonne of coal burnt in a power station, about 11 tonnes of gases are exhausted – 7.5 tonnes of nitrogen from the air used to burn the coal, plus 2.5 tonnes of CO2 and one tonne of water vapour from the coal combustion process.

Normally these beneficial atmospheric gases are released to the atmosphere after filters take out any nasties like soot and noxious fumes.

However, CCS also requires energy to produce and fabricate steel and erect gas storages, pumps and pipelines and to drill disposal wells. This will chew up more coal resources and produce yet more carbon dioxide, for zero benefit.

But the real problems are at the burial site – how to create secure space for the CO2 gas.

There is no vacuum occurring naturally anywhere on earth – every bit of space is occupied by solids, liquids or gases. Underground disposal of CO2 requires it to be pumped AGAINST the pressure of whatever fills the pore space of the rock formation now – either natural gases or liquids. These pressures can be substantial, especially after more gas is pumped in.

The natural gases in rock formations are commonly air, CO2, CH4 (methane) or rarely, H2S (rotten egg gas). The liquids are commonly salty water, sometimes fresh water or very rarely, liquid hydrocarbons.

Pumping out air is costly; pumping natural CO2 out to make room for man-made CO2 is pointless; and releasing rotten egg gas or salty water on the surface would create a real problem, unlike the imaginary threat from CO2.

In some cases CCS may require the removal of fresh water to make space for CO2. Producing fresh water on the surface would be seen as a boon by most locals. Naturally, some carbon dioxide buried under pressure will dissolve in groundwater and aerate it, so that the next water driller in the area could get a real bonus – bubbling Perrier Water on tap, worth more than oil.

Then there is the dangerous risk of a surface outburst or leakage from a pressurised reservoir of CO2. The atmosphere contains 0.04% CO2 which is beneficial for all life. But a CCS reservoir would contain +90% of this heavier-than-air gas - a lethal, suffocating concentration for nearby animal life if it escaped.

Pumping gases underground is only sensible if it brings real benefits such as using waste gases to increase oil recovery from declining oil fields – frack the strata, pump in CO2 and force out oil/gas. To find a place where you could drive out natural hydro-carbons in order to make space to bury CO2 would be like winning the Lottery – a profitable but unlikely event.