The Facts
Gas vs Coal – The Greenhouse Gas Debate
There is no question that the road to total energy generation by renewable energy only has to be the worldwide goal. However, there is a need to build a bridge between coal fired electricity generation and total renewable energy electricity generation.
About six per cent of the total NSW electricity usage is provided from renewable energy sources. The NSW Government has set targets through the State Plan to achieve 20% renewable energy consumption by 2020 in light of the Federal Government's expanded Renewable Energy Target. Renewable energy in NSW is derived from the following sources:
- hydro (88%)
- biomass (5%)
- landfill methane (5%)
- wind (1%)
- solar (1%)
An interesting and detailed paper explaining the different renewable energy sources and the issues with them can be found at the following link:
http://www.aph.gov.au/library/pubs/rp/2000-01/01RP08.htm
There are major problems at present with renewable energy sources. Many of these problems are of an environmental impact nature. The environmental impact relating hydro electricity generation is well known. Issues relating to wind farms are coming more and more into the public eye. However, the major problem is the capacity for renewable energy sources such as wind and solar to serve the energy needs of the nations. These energy sources can only provide base load power and only do this for less than 10% of the time. This is because the wind does not blow and the sun does not shine on demand. Therefore, to maintain the base load electricity requirements alone, there is currently a need for larger scale electricity generation such as coal and gas. Nuclear power is an option but this power source is not currently on the national agenda. It is widely accepted that coal fired power generation must be phased out in favour of a cleaner alternative such as natural gas. The problem is how can this be done without affecting the nation’s power needs? Base load power must be maintained and furthermore peak power demand must also be satisfied. At present renewable energy sources cannot meet this demand. It will be many years until the technology allows this.
Therefore the question remains how can Australia maintain its necessary base and peak load power demand, become cleaner and bridge the gap towards viable total renewable energy production?
Quite simply, if nuclear power is off the agenda then there is only one answer – natural gas.
Coal seam gas (CSG) and coal mine gas (CMG) is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy.
The term refers to methane adsorbed into the solid matrix of the coal. It is called 'sweet gas' because of its general lack of hydrogen sulphide. The presence of this gas is well known from its occurrence in underground coal mining, where it presents a serious safety risk. CSG and CMG are distinct from a typical sandstone or other conventional gas reservoir, as the methane is stored within the coal by a process called adsorption. The methane is in a near-liquid state, lining the inside of pores within the coal (called the matrix). The open fractures in the coal (called the cleats) can also contain free gas or can be saturated with water.
Unlike much natural gas from conventional reservoirs, coal seam methane contains very little heavier hydrocarbons such as propane or butane, and no natural gas condensate. It often contains up to a few percent carbon dioxide.
Natural gas (including CSG and CMG) has a substantially lower carbon ‘footprint’ than coal as can be seen in the Figure 1.
There is much of information on the internet relating to coal seam gas and the greenhouse gas debate. There is no question that natural gas, including CSG is a medium term answer to reducing worldwide greenhouse gas emissions. However, modern production techniques, engineering design, processes and risk management techniques enable gas to be extracted in such a way as to reduce the overall worldwide carbon footprint if this extraction is tied in with a reduction in coal production and use for power generation.
The following are examples of information available on the internet.
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