I wonder how much carbon dioxide does grass sequester, compared to trees. Moreover, is grass still efficient in absorbing pollution? It seems to me that grass would be more efficient in storing carbon in soil than trees.
I found this article regarding lawns. It suggests that lawns could be regarded as carbon sinks only if they are not (frequently) mowered, and do not use pesticedes.
An acre of established temperate forest can hold from 2,000 lbs. up to 6,000 or more lbs. of carbon per year, depending on the age of the trees and other conditions. Mature grasslands sequester 2,400-3,600 lbs. per acre each year.