Big Oil must prepare itself for the end of the hydrocarbon age as alternative energies win over consumers in coming decades, chairman of world No. 2 energy firm Royal Dutch/Shell said yesterday...Shell has moved firmly into the same camp as fellow oil supermajor BP, which has made vigorous efforts to carve out an environmentally friendly public image. The world's No. 1 oil firm, Exxon, has by contrast concentrated firmly on its oil and gas interests, and had little truck with the environmental lobby.