Nothing can replace the trees. They not only produce oxygen by breathing in the carbon dioxide but also they give humans a healthy feel of fresh environment.
But, in overly populated cities if Biourban would be installed instead of growing 368 trees (which is quite hard in some of the cities because of the non-availability of the space and sometimes ground is not available which is suitable for the trees) then I'd say, "it's a superb replacement and a need of the time".