How big is the world fossil fuel market?

I’m trying to understand the various options for the world to meet ever growing needs for energy, electrical power, transportation, etc. I found a figure of $400 billion a year for the alternative energy industry. I have no idea how accurate that is. But so far, I have been unable to find any estimates for the fossil fuel industry, including coal, oil and natural gas.

I did find figures on the production of each of those resources. By multiplying barrels of oil, tons of coal, and cubic meters of gas produced by their current prices, I came up with a figure of $37 trillion a year. But that could be wildly off, and doesn’t include conversion to electricity with cost per KW hour and so forth. Can anyone help with an accurate measure for any or all of the different energy sources out there—fossil fuels, renewables, nuclear and what else?