Greenhouse
 
Greenhouse and Coal – Threat or Opportunity? 
J Latten   Department of Mining and Energy, Brisbane
The 1990’s were the “environment” decade. “Ecologically sustainable development” was the phrase on everyone’s lips early in the decade. However, since late 1997, the word “greenhouse” has dominated the public environment agenda like no other.  Almost every conceivable use of coal leads to carbon dioxide emissions, the “arch-villain” in the greenhouse story.  So clearly greenhouse presents challenges to the coal industry and its customers. However, embedded in every challenge is an opportunity for those astute enough to seek it out. I believe clean coal technologies in particular will play a significant role in a greenhouse constrained future.
So let us have a closer look at greenhouse and its implications for the coal industry. Much of what I present here focuses on the background to greenhouse and coal in Australia, and may in your eyes be excessively focussed on the threats. However, be patient, for without that background, it will not be possible to discuss the opportunities for coal, as I will do briefly at the end of this paper.

A Potential Technology for “Zero” Greenhouse Gas Emissions from Conventional Power Plants
A-K Wong and D Zhang   Curtin University of Technology, Perth
Conventional combustion of fossil fuels for power generation contributed to a large proportion of man-made greenhouse gas (GHG) emissions.  One of the key difficulties of mitigating these emissions is separating CO2 from the flue gases (consisting mainly of N2 for sequestration
This paper discusses the feasibility of a potential technology for GHG emission control.  This technology employs conventional combustion of fossil fuels (such as coal), using oxygen as the oxidant and recycling CO2 and /or H2O form the flue gases with the aim to simplify the separation of flue gases.
Mass and energy balance analysis is performed for four cases: conventional combustion, recycling H2O only, recycling CO2 only, and recycling the whole flue gas.  Aspects addressed include combustion reactions, air/oxygen requirements and flue gases.  Preliminary analysis show recycling H2O alone is most beneficial because it is simpler, less energy consuming and cheaper to pump H2O and less sensible heat is loss through flue gases.  However, further study is needed to improved sufficient heat transfer.

Non-Combustion Sources of Greenhouse Gases
M Juniper, Brisbane
The current global trends are the increase in greenhouse gas concentrations and the associated increase in the earth’s surface temperature. Both the sources and sinks of greenhouse gases are important considerations as they effectively determine the atmospheric concentrations of the greenhouse gases. While CO2 is currently the most significant greenhouse gas, CH4 is becoming increasingly important due to its rate of increase and its physical and chemical nature. Global emissions of CH4 range from 305-775 T(1012)g CH4/yr. Wetlands are the largest source of CH4, followed by rice paddies, fossil fuels, ruminants, biomass burning, land-fill, termites and CH4 hydrates. Termites are therefore not major contributors to the CH4 emissions with estimates ranging from 10-50 Tg CH4/yr. The primary methane sink is the reaction with hydroxyl radicals within the troposphere. The amount of CO2 emitted from the combustion of fossil fuels is 5500 Tg/yr and is therefore a significant source of greenhouse gases. CH4 Therefore, CH4 has the potential for greater significance, in terms of it’s contribution to the greenhouse effect in the future.
 
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