Volatile organic compounds (VOCs) have a profoundly negative impact on the wellbeing of the environment. Besides being major contributors to global air pollution, VOCs also adversely affect human health. Thus, chemical industries are being increasingly pressurised into limiting the release of VOCs into the atmosphere. Chemical industries often use absorption processes to accomplish this task. The methyl esters that constitute biodiesel are an environmentally friendly substitute for conventional organic solvents in absorbing and removing VOCs from waste process gas streams. This book focuses on the use of UNIFAC as a thermodynamic model to evaluate which VOCs are suitable for absorption by the solvent biodiesel. This is accomplished by measuring the activity coefficients of various VOC/ biodiesel mixtures. In the book, various VOC control technologies are investigated and an investigation into the various thermodynamic models used in computing activity coefficient values is also conducted. This book will be useful to anyone who is searching for a suitable absorption solvent, as well as those who wish to know more about the various thermodynamic models being used by industry today.