Evaluation of the Effect of Chemical or Enzymatic Synthesis Methods on Biodegradability of Polyesters

This work compares the biodegradability of polyesters produced by an esterification reaction between glycerol and oleic di-acid (D 18:1) issued from green chemical pathways, via either classical thermo-chemical methods, or an enzymatic method using the immobilized lipase of Candida antartica B (Novozym 435). An elastomeric polymer synthesized by enzymatic catalysis is more biodegradable than an elastomeric thermo-chemical polyester synthesized by a standard chemical procedure. This difference lies in percentage of the dendritic motifs, in values of the degree of substitution, and certainly in cross-links inducing an hyper-branched structure less accessible to the lipolytic enzymes in a waste treatment plant. However, when the elastomeric polymer synthesized by enzymatic catalysis is processed at high temperature as required for certain industrial applications, it presents an identical rate of biodegradation than the chemical polyester. The advantages of the thermo-chemical methods are greater speed and lower cost. Enzymatic synthesis appears be suited to producing polyesters, devoid of metallic catalysts, which must be used without processing at high temperature to keep a high biodegradability.     

Case study evidence that direct regulation remains the main driver of industrial pollution avoidance and may benefit operational efficiency

Environmental regulation is required to reduce industrial pollution to levels that are socially acceptable and economically efficient, but there is debate over the most efficient form of such regulation. Typically, a limited range of environmental and economic parameters are accounted for in the econometric studies that inform that debate. This paper integrates evidence from two separate studies to assess a broad range of parameters related to the efficiency of industrial environmental regulation. Questionnaire responses from 25 Italian manufacturers of building-chemicals and 28 Irish pharmaceutical manufacturers provided evidence on the environmental effectiveness and operational impacts of different regulatory instruments. Combined with extensive emissions data from Irish pharmaceutical manufacturers, survey results enabled a quantitative estimation of pollution avoidance specifically attributable to direct regulation. The monetised social benefit of avoided pollution was found to be equal to direct compliance costs. Chemical manufacturers in Italy and Ireland stated that direct regulation is a more important driver of industrial environmental performance than economic or voluntary regulation, and their responses indicated that direct compliance costs may be countered somewhat by stimulated operational improvements. It was concluded that direct regulation is an effective approach for multi-pollutant control in an industrial context, and that the efficiency of such regulation may be underestimated in studies that do not consider the full range of pollutants and operational effects.