CHAPTER 1. Sustainability of Green Synthetic Processes and Procedures

Although the ecological footprint was perhaps the first green metric, the atom economy and E-factor have become the key metrics of green chemistry by providing the mass balance of chemical reactions and processes at the molecular level. Sustainability was poorly defined originally, since the key requisite to accurately forecast the needs of future generations remains difficult to pinpoint. Consequently, sustainability was replaced with suitability by many stake holders, as they had vested and/or conflicts of interests to label suitable developments sustainable. The sustainable development goals recently introduced by the United Nations seem to serve as a ‘roadmap to happiness’ instead of metrics. A simple and independent definition of sustainability was recently provided: Nature's resources, including energy, should be used at a rate at which they can be replaced naturally, and the generation of wastes cannot be faster than the rate of their remediation by Nature. The ethanol equivalent, the sustainability values of resource replacement and fate of waste, and the sustainability indicator have been recently defined to measure the sustainability of biomass-based carbon-chemicals and renewable energy. The production of ethylene, propylene, toluene, xylenes, styrene, and ethylene oxides cannot be sustainable due to the limited amount of bioethanol. The required volume of corn and the corresponding size of land are only enough to replace one sixth of fossil resources in the USA, EU, and China, and practically insufficient in Canada and the Russian Federation. Until the utilization of electricity becomes practical and economical in aviation, biomass-based liquid fuels are the sustainable alternative.