consider I have a mixture of Hydrogen and Natural Gas.
The volumetric mixture is $\varphi_{H_2} = 70 \%$ and $\varphi_{NG} = 30 \%$.
So the $H_2$ makes up a mass fraction of
$$w_{H_2} = \frac{\rho_{H_2}\cdot\varphi_{H_2}}{\rho_{H_2}\cdot\varphi_{H_2}+\rho_{NG}\cdot\varphi_{NG}} = 21.2 \%$$
with $\rho_{H_2} = 0.0899 \frac{kg}{m_n^3}$ and $\rho_{NG} = 0.780 \frac{kg}{m_n^3}$.
How much CO2-Emissions does the combustion of $1 kWh$ of my mixture produce, if the combustion of Natural Gas produces $0.200 \frac{kg}{kWh}$? How does the calculation work out?