Recent conventional and non-conventional WCO pretreatment methods: Implementation of green chemistry principles and metrics

Abstract

Several waste cooking oil (WCO) conventional pretreatment methods have been used to reduce free fatty acids (FFA) for biodiesel production via transesterification. The objective is to achieve high yields of biodiesel with characteristics that comply with standards. However conventional methods have certain limitations mainly due to the fact that very often the impact on the environment is not considered, which may affect their effectiveness and their greenness. Thus, conventional pretreatment methods are time and chemical-consuming, waste-generating and costly. The present review describes recent intensified techniques (2019–2021) used to overcome conventional limitations and their relationship with green chemistry principles. Also, it highlights the use of green chemistry metrics to quantify the greenness of a process hence providing a decision making tool for sustainability implementation.