Ahh what the heck - here is my calculation - rough draft:
- Combustibles per quare meter: 100kg/m2 (that is a very low value, compared to most office buildings)
- Office space area: 400,000m2
-> Total mass of combustibles: 40,000,000kg
- Average energy density of office combustibles: 10MJ/kg (again, that is a very low estimate; paper has more, plastics have much more)
-> Total energy of combustibles: 400,000,000MJ.
- This is the energy found in roughly 2.5 million gallons of fuel, or 100,000 tons of TNT
- Seconds in 99 days are 99*24*60*60 = 8,553,600s
-> Power of fires in 99 days: 47MW
47MW is the average net electrical power consumption of a city of more than 40,000 people in Germany (including housholds, industry and public sector).
My car has a power output of 90kW or 0.09MW. So the fires had the power of 500 times my car.
One block of an average nuclear power plant has an output of 1000MW, or 21 times the power of that debris fire.
The largest onshore wind turbines have a power of 1.5 MW. You need about 30 of these to equal the power of GZ.
Conclusion: There was plenty of combustible energy to be released by fires for 99 days.