# How the dark matter density parameter appears in Big Bang Nucleosynthesis (BBN)?

I know that it is possible to obtain the light element abundances ($$^{4}\mathrm{He}, \mathrm D, ^{7}\mathrm{Li}$$ etc.) and to determine the baryon-to-photon ratio $$\eta$$ from the total baryon abundance $$\Omega_\mathrm{b}$$. I know the procedure to get it and I understand it. Doing so we obtain $$\eta = (6 \pm 0.5)\times 10^{-10}$$ and $$0.018 < \Omega_\mathrm{b} \lt 0.023$$. From this outcome we know the abundance of light elements are very small compared to the total abundance $$\Omega_\text{total}$$, that is, $$\Omega_\mathrm {b} \lt \Omega_\text{total}$$, once $$\Omega_\text{total} = 1$$. My questions: how can I know that only $$\sim 23\ \%$$ of $$\Omega_\text{total}$$ is dark matter instead of any other amount once the dark energy were not determined here (just inside BBN)? Is really necessary to use results that come from another part of $$\Lambda$$CMD?

I hope I've been clear.