化学プロセスの環境調和性を定量評価する指標の一つであり、1992年にオランダの化学者Roger A. Sheldonによって提唱された。
関連論文 “The E Factor: fifteen years on”
Sheldon, R. A. Green Chem. 2007, 9, 1273. DOI: 10.1039/B713736M
 “E factors, green chemistry and catalysis: an odyssey”
The purpose of this perspective is to review the effect that the E Factor concept has had over the last fifteen years on developments in the (fine) chemical industry and pharmaceutical industry with regard to waste minimisation and to assess its current status in the broader context of green chemistry and sustainability. We conclude that the E Factor concept has played a major role in focusing the attention of the chemical industry world-wide, and particularly the pharmaceuticalindustry, on the problem of waste generation in chemicals manufacture. It provided, and continues to provide, the impetus for developing cleaner, more sustainable processes.
Sheldon, R. A. Chem. Commun. 2008, 3352. DOI: 10.1039/B803584A
The development of green chemistry is traced from the introduction of the concepts of atom economy (atom utilisation) and E factors in the early 1990s. The important role of catalysis in reducing or eliminating waste is emphasised and illustrated with examples from heterogeneous catalytic oxidations with hydrogen peroxide, homogeneous catalytic oxidations and carbonylations and organocatalytic oxidations with stable N-oxy radicals. Catalytic reactions in non-conventional media, e.g. aqueous biphasic, supercritical carbon dioxide and ionic liquids, are presented. Biotransformations involving non-natural reactions of enzymes, e.g. ester ammoniolysis, and the rational design of semi-synthetic enzymes, such as vanadatephytase, are discussed. The optimisation of enzyme properties using in vitro evolution and improvement of their operational stability by immobilisation as cross-linked enzyme aggregates (CLEA®) are presented. The ultimate in green chemistry is the integration of catalytic steps into a one-pot, catalytic cascade process. An example of a chemoenzymatic synthesis of an enantiomerically pure amino acid inwater and a trienzymatic cascade process using a triple-decker oxynitrilase/nitrilase/amidaseCLEA are discussed. Finally, catalytic conversions of renewable raw materials are examined and the biocatalytic aerobic oxidation of starch to carboxy starch is presented as an example of green chemistry in optima forma i.e. a biocompatible product from a renewable raw material using a biocatalytic air oxidation.