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Wednesday, 3 December 2003
Page: 23693

Dr WASHER (7:44 PM) —Tonight I want to talk about hell and heaven. Venus, the second planet from the sun, is hell. Venus has no moon, but it does have a substantial atmosphere—a choking shroud of almost pure carbon dioxide, or CO2. So dense is its waterless sky that it presses down on the surface at a pressure 92 times greater than that on earth and equivalent to the bottom of a lake 900 metres deep. A global greenhouse effect keeps the surface temperature twice as hot as a domestic oven: 480 degrees Celsius—enough to melt tin, zinc and lead. Carbon dioxide, the so-called greenhouse gas, lets in sunlight but is opaque to infrared radiation—that is, heat—so Venus has become a heat trap.

The clouds above Venus are composed mainly of sulfuric acid. The highest of these clouds float 65 kilometres above the surface—more than four times higher than the clouds on earth. On Venus, global episodes of volcanism vent huge quantities of water vapour and CO2 into the atmosphere. Venus, being more proximal to the sun than earth, was too hot for water to fall as rain or to pool on the planet's surface. Thus from the start Venus lacked oceans and seas, which caused a fatal blow for complex life, as carbon dioxide, which is soluble in liquid water, has nowhere to dissolve.

On earth—heaven, compared with Venus—it was cool enough for water to pool on the surface, allowing the poisonous CO2 to dissolve and be removed from our atmosphere. Venus never had any oceans to cleanse its atmosphere of CO2. The gas remaining in the atmosphere trapped the planet's heat and the heat, in turn, baked more and more water vapour and CO2 out of the soil and rocks. The sun's deadly ultraviolet rays destroyed the water vapour. As Venus lacks a protective ozone layer, the leftover CO2 piled up and the planet grew even hotter. This sad state of affairs is known as a runaway greenhouse effect.

Water is abundant throughout the solar system, but nowhere, apart from earth, are the conditions right for water to exist as liquid on the surface. Mars is too cold and Venus is too hot. The third planet from the sun, the blue earth, is the gem of our solar system and is the only world conducive to complex life forms. Three-quarters of the earth is covered in water, most of it in deep oceans—an average of four kilometres deep—while the rest is locked up at the poles, frozen solid. Our atmosphere consists of 78 per cent nitrogen, 21 per cent oxygen and, currently, only small amounts of the CO2 that makes Venus so inhospitable.

So why take a journey into the solar system to discuss the problem of greenhouse gas? It is a means of looking at carbon sequestration—the action of trapping essentially man-made atmospheric carbon dioxide into a nonatmospheric sink. Dr Peter Cooke from the CRC for Greenhouse Gas Technologies illustrated that CO2—the most significant greenhouse gas because of its quantity and which is generated mainly by industrial activity—can be sequestered by vegetation growth and captured and stored in deep ocean and physicochemical forms.

The 1997 Kyoto protocol recognises CO2 sequestration by vegetation growth and allows credits for CO2 in forest production. Currently, however, geosequestration is not contemplated as a credible method of CO2 fixing; hence there are no current credits in the protocol for geological storage. Over half our net annual CO2 emissions are from major stationary sources, such as power stations and industrial plants—500 million tonnes of CO2 equivalent. Fifty per cent of these stationary emissions are proximal to credible geological sinks.

Australia's current research focus on geological storage in deep saline-saturated reservoir rocks capable of storing CO2 for over 1,000 years is to be commended. It is proposed that a stream of concentrated CO2 be transported by pipeline and then compressed into a dense supercritical state for injection into the suitable geological formation. Injection into certain geological strata can have collateral benefits such as enhanced oil recovery and coal bed methane production. Currently carbon is naturally sequestered in trees and grasses; enormous amounts are fixed in the oceans and seaweed, coral, plankton and gas hydrates such as methane. It seems so strange with such planetary phenomenon that Kyoto could not comprehend—(Time expired)