Forget about cremation, with all of that heat and pollution. You can go the opposite direction, and freeze yourself to dust, courtesy of a Swedish company called Promessa. Your corpse is frozen down to -18 degrees Celsius. Then, coffin and all, you are lowered into liquid nitrogen.
Inside the coffin, according to Promessa, your body "becomes very firm and brittle." Then body and coffin are subjected to "light vibration," and ... well, dust to dust (55 to 65 pounds, in fact) as they say. You then get a coffin made from corn and/or potato starch. You and your coffin will compost in six months to a year. Promessa recommends planting a tree above the grave, as it will "absorb the nutrients given off."