Take all the trees in your neighborhood.
Now set aside a 6 feet by 7 feet section of your lawn.
That’s 42 square feet of grass. Or less than 0.5% of an average sized residential lawn in the US.
Replace that 42 square feet of grass with a
Now chop down all the trees in your neighborhood.
The moss lawn is still taking more CO2 out of the atmosphere than what the trees you cut down could’ve done.
“Studies suggest just 12 square metres of moss lawn can apparently absorb as much carbon as 275 mature trees.” The Guardian 
So I wanted to track down these studies since it seems like a preposterous claim.
Doing some digging it turns out that there is a vertical moss wall that does absorb CO2 at the same rate as 275 trees:
And what are the dimensions of this solution? The dimensions of the above City Tree are 2.9 metres x 3.75 metres or 11 square meters .
Bingo! So this is where The Guardian got their statistic of a 12 square meter moss lawn absorbing the same amount of CO2 as 275 trees.
The claim was validated by a lab called Proambiente; however, the lab’s website is in Italian so I was unable to even try to get my hands on their lab results concerning carbon sequestration. 
Assuming the results reported are valid, will you get the same results planting a horizontal lawn?
Probably not. The City Tree’s vertical arrangement increases the amount of wind passing through the moss and the placement of the systems are algorithmically calculated to maximize carbon capture .
I therefore cannot tell you how many trees’ worth of CO2 capture a horizontal lawn will do. But if you’re interested in creating an indoor moss garden, you might find this article helpful.
Also, if you’d like to plant a moss lawn, here’s a useful YouTube video.
And for more tips on how you can help the environment, check out this panel discussion.
 The Guardian, June 3, 2018 https://www.theguardian.com/lifeandstyle/2018/jun/03/blade-runners-the-joy-of-moss-lawns
 Air Pollution magazine, The CityTree: a vertical plant wall https://www.witpress.com/Secure/elibrary/papers/AIR15/AIR15025FU1.pdf
 Climate-KIC, foundation who paid for the lab testing https://www.climate-kic.org/partners/proambiente/