Carbon Capture for lawns

I have a robot mower that mows my grass. I was wondering if it actually captures carbon.

I can see that the soil is capturing soil as it is getting higher. I had an edging made of bricks and over the last 15 year the grass has crept up ca 15cm. So about 1 cm a year capture. This is a capture of carbon but need to do the calculations to see if overall positive.