Illustrations towards quantifying the sustainability of technology

This paper attempts to quantify the sustainability of technological process es. It is based on thermodynamics with energy carriers and materials (produ cts, waste, etc.) expressed in the same calculable quantity-exergy (Joule). The results have three considerations. One factor reflects to that extent renewable resources are used. In addition, the technological efficiency has to be accounted for as it affects sustainability. Finally, the results tak e into account the generation of waste products and the exergy required for converting the waste into products which are harmless or assimilable in th e ecosphere. The proposed measure of sustainability has been illustrated fo r two types of products. In the first illustration, ethanol production was studied. Two routes were investigated, one starting from fossil oil and the other from agricultural products. Additionally, a route based on the synth esis from carbon dioxide and hydrogen was examined, in which hydrogen was g enerated by splitting water with electricity from photovoltaic solar energy conversion. The second product studied was electricity, generated from the combustion of natural gas or from photovoltaic solar energy conversion. Th e merit of the obtained results are that they treat technological sustainab ility not only in qualitative but also in quantitative terms. The insights obtained can help to account for sustainability in the development of new c oncepts of chemical technology.