# How much CO2 is produced by plant litter?

I made measurements of CO2 formed during decomposition of dead plant material using gas spectrometer. It gives the results of CO2 in ppm. How do I convert it to $\large \rm \frac{mg~CO2}{\text{1 g plant matter}}$ per day? I know that it has something to do with volume of my jar and and mass of plant litter, but that's all.