Integration of microwave assisted pretreatment for ameliorating anaerobic digestion for clean energy

Abstract

The United Nations Sustainable Development Goals (SDG7) aim towards the attainment of affordable and cleaner energy, underscoring the urgency to transition from fossil fuels to sustainable alternatives. Waste biomass utilization is considered a highly effective strategy for developing a biowaste economy or circular economy. The circular economy holds immense promise to provide a sustainable and affordable alternative to renewable energy and chemicals. Among several promising alternatives, Anaerobic digestion (AD) has emerged as a key technology that utilizes anaerobic microbes through a series of steps i.e., hydrolysis, acidogenesis, acetogenesis, and methanogenesis, for the conversion of complex biomass into biofuel and chemicals. However, the inherent recalcitrance properties of the waste biomass limit the efficient hydrolysis of biomass which in turn further limits the subsequent transformation stages of the AD. Thus, there is a need for a pretreatment stage before AD for ease of access to the biomass components. Microwave-assisted pretreatment (MAP) has demonstrated the ability to break down complex biomass structures, thus improving substrate availability for microbial action during different stages of AD. MAP has gained prominence due to several advantages such as high specificity for selective heating, rapid processing and lower energy requirement. The integration of MAP with AD offers promising solutions to achieve improved biodegradability, and higher energy yields at reduced operational costs, and lower power inputs. Thus, there is an urgent need to develop an efficient MAP system with the ability to utilize a wide range of biomass in a greener and cheaper manner. Thus, this conceptual review aims to provide insight into the mechanism of MAP technology and key biomass properties to be considered for integration to MAP to AD. The review also provides insight into techno-economic, energy efficiency, and environmental impact assessment for the integration of MAP to AD. Furthermore, this review provides a roadmap for the development of a scalable, cost-effective MAP-mediated AD system for finding bioenergy solutions aligning with global sustainability goals.