Likely much more than at present.
Most of the early carbon dioxide was converted into two forms:
1. Carbonate
2. Keragen (organic residues)
When living organisms died, large quantities wound up as keragen in rocks throughout the Earth's sedimentary rocks. All living organisms contain significant quantities of nitrogen, which is incorporated into keragen. The amount of highly dispersed keragen is vast, far exceeding fossil fuel reserves. The quantity of nitrogen in this keragen is also vast.