How to keep a green footprint?

It seems sort of impossible. I've coated my houses in grass and trees, even putting grass on and inside the roofs. I've used only eco-friendly flooring and wall materials. I've made sure that there is no concrete anywhere, even on the outside of the basements and the inside of the fireplaces. But it never seems to make a difference. I understand there is a machine you can make that will help, but none of my Sims have made it yet. It's frustrating.