Plan to bury global warming

By SIMON COLLINS science reporter

New Zealand scientists are working on a novel solution to global warming - pumping carbon dioxide underground.

A team from Crown-owned Industrial Research Ltd and the Coal Association's CRL Energy (formerly Coal Research Ltd) plans to extract hydrogen from coal to provide fuel for fuel cells, then bury the leftover carbon dioxide.

The plan could slow global warming in two ways: clean-burning hydrogen fuel cells would replace petrol, and burying carbon dioxide would help remove one of the main contributors to the "greenhouse effect".

The carbon dioxide will be heated to about 45C and put under high pressure so that it becomes a "supercritical fluid" - described as "neither a gas nor a liquid, but like a liquid".

It will then be pumped a kilometre or more underground into the same kind of porous rocks that hold natural gas.

"If you do get the right geological structure that is very similar to that required for a natural gas field, you can put carbon dioxide down there and basically trap it for ever," said the project leader, Dr Stephen White. "There are enough geologically suitable places in the world ... You could put everything in there for the next 10,000 years and not see a fraction of it."

Dr White is working on an American-financed pilot project in the United States with a New Zealander who is director of the Utah Geological Survey, Dr Rick Allis.

Although details are still being negotiated, the Foundation for Research, Science and Technology has approved money for a six-year project to find suitable places to bury carbon dioxide in New Zealand.

"Clearly, there are structures like that in New Zealand - in the Waikato, off the coast, around the Maui gas field," Dr White said.

"The earth is solid, but it is porous, and maybe 10 per cent of the rock volume contains water or gas or something.

"By choosing a structure where you have a porous reservoir and a cap on top, like a natural gas-type system, you can inject [carbon dioxide], displace the water in the reservoir and trap it beneath the lower-permeability [more solid] rock."

In some cases, the carbon dioxide might even react with the rock and be trapped as a solid.

The new technology is not yet economical here.

But it is used commercially in Norway, where a heavy carbon tax makes it worthwhile for oil companies to extract carbon dioxide from natural gas and bury the COinf2 at sea. Dr White hopes to find suitable New Zealand burial spots on land.

"The trouble with putting it under the sea is that when the carbon dioxide reacts with the seawater, it forms a weak acid. This can be really quite destructive of life."

He expects that the technique will become viable at many sites where the gas is emitted on a large scale, such as the Huntly power station.

"Where it fails is in areas like transport, where you have a diffuse source of carbon dioxide. You can't capture it off each car."

That is where the other part of the project comes in.

If hydrogen can be extracted from the hydrocarbons of coal, it could be used for fuel cell batteries that combine hydrogen with oxygen from the air to produce electricity and water.

The research manager of Industrial Research's Electrotec division, Alister Gardiner, said the research could catapult New Zealand into "the hydrogen economy".

"CRL Energy has done some work with South Island lignites to show they are particularly suited to hydrogen production."

The research programme has grown out of Industrial Research's longstanding work on developing mathematical models of geothermal energy resources.

nzherald.co.nz/climate

Related links

nzherald.co.nz/environment