Greenhouse gases (GHG) are gases in the atmosphere that capture and reflect heat back to the Earth, and act like the glass roof of a greenhouse. The Earth naturally has greenhouse gases in its atmosphere, however there are now more greenhouse gases in the Earth’s atmosphere due to human activities such as power stations, motor vehicles and agriculture. The increase in greenhouse gases means that the Earth is now trapping more heat in the atmosphere than it normally would and this is leading to climate change. There are 4 types of greenhouse gases:
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (N2O)
- Fluorinated gases.
For more information on greenhouse gases visit the United States Environmental Protection Authority website.
Queensland has a number of projects that are trying to capture GHG or find ways to store them.
Capturing GHG involves separating them from other gases, including water vapor and ash, from power stations. There are 2 basic ways to capture GHG, pre-combustion and post-combustion.
Pre-combustion processes convert the fuel into a gas consisting of hydrogen and GHG before being burnt. The hydrogen is separated, then burnt as fuel, while the GHG is captured and compressed for transport to a GHG storage well or to a factory that sells the GHG for agriculture or industry products.
Post-combustion capture processes separate GHG from gases emitted after the fuel is burnt. These processes include using chemicals to absorb GHG from emissions or even pumping the emissions through water to help grow algae, which uses the GHG to grow and can later be turned into diesel.
For more information on capturing GHG visit the CSIRO website.
The department ensures that these activities are appropriately regulated under the Environmental Protection Act to ensure there are no negative impacts on the environment.
GHG storage (also known as geosequestration) utilises suitable deeply buried geological formations to store captured carbon dioxide (CO2) and methane (CH4).
The range of GHG storage options includes:
- geological storage (replacing water, gas or petroleum locked underground with GHG)
- mineralisation (binding GHG to minerals with a natural chemical reaction similar to the way coal seam gas is bound to underground coal).
How does GHG storage work?
GHG is injected into deep underground geological formations and is permanently trapped there through several natural mechanisms.
GHG are first cooled and compressed into a liquid then transported (usually by pipeline) to a GHG storage site, where they are injected through a well into the target geological formation at depths of 800 metres or more. The GHG can become trapped in the deep underground formation by:
- using surrounding solid rock to stop the gas from moving out of the formation
- using water in the formation to absorb the GHG
- using coal or other compounds in the rock to bind the GHG (mineralisation).
For more information on greenhouse gas storage visit the Geoscience Australia website.
In Queensland GHG storage is regulated under the Greenhouse Gas Storage Act 2009 (GHG Storage Act) and the Environmental Protection Act 1994 (EP Act). A company that wants to explore for GHG storage sites and eventually inject GHG must first apply for a GHG permit or license from the Department of Natural Resources and Mines and apply for an environmental authority from the department.
Currently the department has not authorised the injection of GHG underground. A full environmental assessment will need to be undertaken to prove the injection will not result in impacts to the environment before the department will allow injection to commence.