I did my own calculations based on the Victorian fires and found that Packham seems to be roughly correct. I obtained the figure of 1290 Hiroshima bomb equivalents compared to Packham’s estimate of 660. I'm not saying that my figures are more accurate, there is some guess work involved, but my figure is in the same ballpark as that estimated by David Packham
Here are my calculations.
More than 330,000 hectares were destroyed in Victoria’s “hell on earth” bushfires and according to Mr Packham each hectare contained 30 tons of bushfire fuel — adding up to 9.9m tons. ”That equates to the energy release of 660 Hiroshima bombs” ...
- Victoria's bushfires compared to Hiroshima
Yield of Hiroshima Bomb: 1 Hiroshima Bomb is roughly 20 Kilotons TNT Equivalents of 1 Kiloton of TNT: 1 Kiloton TNT equals 1.15 x 10^6 Kilowatt-hours. KT means Kiloton.The amount of energy in wood is a tricky one to calculate accurately. It can vary between fresh wood which has only 2000 Btu/pound of energy and the "high heat value" of 8660 Btu/lb, which is obtained only with perfectly dry wood (0% moisture content) and only in an atmosphere of pure oxygen. Given that the Victorian fires were fuelled mainly by partially or largely dried out dead fuel then it is fair to take an intermediate figure, let us say 5000 Btu/pound
- The fission product equivalent between nuclear reactors and nuclear weapons
- The Amount of Energy in Wood Fuel
1 Btu (thermochemical) = 0.00029287508333 kilowatt-hours
1 pound = 0.00045359237 ton (metric)
By our estimate, wood burns to create 5000 Btu/pound. To convert to Kilowatt-hours / ton then multiply by 0.00029287508333 and divide by 0.00045359237
Hence wood burns to create roughly 3300 kilowatt-hours / ton (rounded). For 9 million tons burnt –> 9 * 10^6 * 3300 kilowatt-hours energy = VB (victorian bushfires)
1 Hiroshima bomb = 20 * 1.15 x 10^6 Kilowatt-hours = HB (Hiroshima bomb)
To calculate Hiroshima bomb equivalents divide VB by HB = 1290 Hiroshima bomb equivalents
David Packham's qualifications:
OAM, MAppSci, worked for 40 years in bushfire research with CSIRO, Monash University and the Australian Emergency Management Institute. He was responsible for fire weather services in the Bureau of Meteorology. His extensive research concentrated on the physics of bushfires, and he applied this research to practical issues including the development of aerial prescribed burning, non-evacuation of properties, modelling of fire behaviour, and forensics