An Evaluation of the Use of Airborne Infra-Red Thermography as a Method for Monitoring Spontaneous C

The objectives of the project were to develop a method for estimating and monitoring the extent of spontaneous combustion in open cut coal mines using airborne infra-red thermography and use the temperature data from the infra-red surveys to estimate greenhouse gas emissions from spontaneous combustion.  The work program included flights in the Hunter Valley over similar ground, one year apart. The final flight obtained data at greater resolution to investigate the significance of large cracks in the spoil from which large emissions of hot gases could be emanating.  Three flights were carried out as follows:

A significant amount of data was also to be obtained using the CSIRO chamber to measure surface emissions so as to establish the clearest possible relationship between greenhouse gas emissions and surface temperature of hot spoil.

An area of a mine (including a self heating spoil pile) was chosen for detailed analysis for each set of data. The area within a particular surface temperature range was calculated for each of the data sets. As the background surface temperatures depended on the meteorological conditions prevailing at the time of the flight, an area of the mine known not to be self heating was used to normalise the temperatures for the three data sets so that the results could be more accurately compared.

Ground truthing temperature data were also obtained and surface temperature was calculated from the infra-red data sets using calibration curves developed from ground truthing data.

The area as a function of surface temperature for part of a spoil pile was used along with the relationship between greenhouse gas emissions and temperature to calculate greenhouse gas emission rates.

KEY RESULTS AND OUTCOMES

• The empirical relationship between greenhouse gas emissions and surface temperature was improved

• The 7x7m pixel data for the same area of spoil pile showed acceptable consistency for the data 1 year apart
• The method of airborne infra-red survey can be used to monitor the general temperatures of the spoil pile
• Greenhouse gas emission calculations showed acceptable consistency between the two 7x7m pixel data sets and increased values for the 2x2m pixel data
• The temperature taken to represent non-heating ground is critical in calculating the total greenhouse emission rate
• The project methodology can be used to monitor total greenhouse emissions