This paper aims at highlighting the hurdles and traps on the way back from CO2 to chemicals (or even fuels). The case of the synthesis of diallcyl carbonates is discussed, considering several synthetic conditions and comparing the relevant amount of energy necessary for product separation. The calculations show that the post-reaction separation process may share an important part of the energy consumption in the whole synthetic procedure and make, in some conditions, the reaction a strong CO2 emitter more than a CO2 consumer. (C) 2016 Elsevier B.V. All rights reserved.