The Great Artesian Basin of Queensland, New South Wales, the Northern Territory and South Australia is the largest groundwater basin in Australia and one of the largest in the world. One aquifer, the Precipice Sandstone, is the source of artesian water, gas and oil and older sedimentary rock units in the Basin which produce coal and coal seam gas.

Current recharge of water is from the northern and eastern edges of the Basin and water moves laterally in the aquifer up to 200 metres per day. A recent injection of 20 gigalitres of treated water from coal seam gas production into the Precipice Sandstone had pressure responses that propagated 100 km in the aquifer. Water in the far western part of the Basin is more than 2 million years old whereas in the far east of the Basin, it is only decades old. Water at depth is up to 130°C and hot artesian water rises to the surface under its own pressure.

In some areas where water has been exploited for a long time, the pressure has decreased and deep water needs to be pumped to the surface. Artesian water is alkaline, varies from fresh to brackish and is used for stock and irrigation and, in some towns, is used for human consumption. Some Outback towns such as Lightning Ridge and Moree have artesian water thermal springs called bore baths. Artesian water contains methane and rotten egg gas and water from some bores pongs so much that it would kill a dead camel.

Coal-fired power stations produce carbon dioxide as an exhaust gas. Carbon dioxide can be liquefied at low temperature and high pressure which requires energy from a coal-fired power station. There is a proposal to inject 330,000 tonnes of liquid carbon dioxide from a Queensland coal-fired power station into the Precipice Sandstone of the Great Artesian Basin at a depth of 2.3 kilometres. At that depth, the liquid carbon dioxide could be at 600 times atmospheric pressure and up to 130°C and hence could flash, expand up to 300 times its volume and explosively ascend to the surface.

Explosive volcanic eruptions are driven by the sudden expansion of a water-carbon dioxide mixture and carbon dioxide can be explosively or passively released from modern or extinct volcanoes where it can be exploited for the food and beverage industry, such as at Mount Gambier in South Australia. In areas of crustal extension, thermal baths rich in carbon dioxide often precipitate calcium carbonate, such as at Pamukkale in Turkey. Crustal compression of rock sequences to form mountain ranges results in the degassing of rocks and bicarbonate mineral springs with bubbles of carbon dioxide are ubiquitous. These are the source of some natural sparkling mineral water. In nature, liquid carbon dioxide occurs in microscopic fluid inclusions which make quartz milky white and liquid carbon dioxide is released as droplets in active submarine tectonic areas, which you will find at the Okinawa Trough or the Mariana Arc.

In many parts of the world, there are gas volcanoes that are the host for gold, copper-gold and copper-gold-uranium mineral deposits. The behaviour of carbon dioxide in geological processes and carbon dioxide at depth is well studied.

The risk of a gas explosion by injection of liquid carbon dioxide from coal-fired power stations into the Precipice Sandstone is real yet has not been evaluated in either the scientific literature and government reports on the Great Artesian Basin or by the company that proposes liquid carbon dioxide injection.

Disconformities, unconformities, sedimentary rock bedding, joints, faults and abandoned wells are conduits for fluids from the Precipice Sandstone to the surface in the western part of the Great Artesian Basin as shown by more than 5,000 mound springs that tap artesian waters from depths of up to 3,000 metres. Such conduits could equally well be conduits for liquid carbon dioxide which would open existing rock weaknesses to the surface.

The same subsurface conditions exist in the eastern part of the Great Artesian Basin where it is proposed to inject liquid carbon dioxide into the aquifer. A phase change from liquid to gaseous carbon dioxide in dilation zones would result in the rapid expansion and cooling of gaseous carbon dioxide during catastrophic explosive ascent from the aquifer to form a cold gas volcano.

It is not suggested that injection of liquid carbon dioxide could stimulate volcanism or a magmatic gas explosion. Injection and residence of liquid carbon dioxide in the Precipice Sandstone would not only make artesian waters acid but could initiate a catastrophic gas explosion and associated gas volcano by phase change or gas expansion-induced fracturing. This is not far-fetched speculation. It has happened before.

The best-known example is that of Lake Nyos in Cameroon. On a still evening on 21 August 1986, the release of 100,000 to 300,000 tonnes of gaseous carbon dioxide from deep below the Lake Nyos caldera at a velocity of over 100 kilometres per hour displaced air for a radius of 25 kilometres around the exhalation vent and killed 1,746 humans, 3,500 livestock and countless wildlife. The trigger for the catastrophic release of carbon dioxide at Lake Nyos is unknown.

Because carbon dioxide is denser than air, it flowed downslope and displaced air in valleys and low-lying areas with the resultant asphyxiation of animals. Lake Nyos is now vented of carbon dioxide from drill holes to prevent any future sudden explosive catastrophic releases. Carbon dioxide venting into the atmosphere also now takes place in the far larger Lake Kivu in Rwanda.

The risk of storing liquid (or even high pressure gaseous) carbon dioxide in a deep aquifer is that there could be a repetition of the Lake Nyos disaster with settlements, stock and wildlife in western Queensland blanketed by a dense gaseous carbon dioxide cloud that would displace air and create asphyxiation.

There is a simple solution. Don’t liquefy and bury plant food. Feed trees, grasslands and crops by venting carbon dioxide into the air from coal-fired power stations to green the planet. Save electricity that would have been used to cool and compress carbon dioxide.

There is no evidence that increased carbon dioxide in the atmosphere drives global warming. Only evidence to the contrary. There has been a decrease in atmospheric carbon dioxide from 0.7 per cent during the Cambrian explosion of life 520 million years ago to the present level of 0.04 per cent by natural sequestration into life, coral reefs, lime-rich and carbonaceous sediments, coal, oil and gas. If this trend continues, when carbon dioxide reaches 0.02 per cent, all plant life will die. Nasa satellites show that the planet has greened because of the slight increase in atmospheric carbon dioxide over the last few decades.

Feed plants, green the planet by burning more coal, oil and gas and don’t starve vegans. You know it’s common sense.

Pity there is no artesian basin beneath Canberra.