Waste to bioenergy: a review on the recent conversion technologies

Sze Ying Lee,Pau-Loke Show,Chung Hong Tan,Rambabu Krishnamoorthy,Dinh-Toi Chu,Revathy Sankaran,Kit Wayne Chew

doi:10.1186/s42500-019-0004-7

Abstract

Scientific studies have demonstrated that it is possible to generate a wide variety of bioenergy from biomass residues and waste, and however its cost is not competitive with petro-fuels and other renewable energy. On-going efforts are continued extensively to improve conversion technologies in order to reduce production costs. The present review focuses on the conversion technologies for transforming biomass residues and waste to biofuels, specifically their technological concepts, options and prospects for implementation are addressed. The emerging developments in the two primary conversion pathways, namely the thermochemical (i.e. gasification, liquefaction, and pyrolysis) and biochemical (i.e. anaerobic digestion, alcoholic fermentation and photobiological hydrogen production) conversion techniques, are evaluated. Additionally, transesterification, which appears to be the simplest and most economical route to produce biodiesel in large quantity, is discussed. Lastly, the strategies for direct conversion of biomass residues and waste to bioelectricity including the use of combustion and microbial fuel cells are reviewed.

Highlights

Since the energy crisis of the 1970s, many countries are interested to develop biomass as a fuel source
The present review provides an in-depth overview of the technological details of the conversion techniques of biomass residues and waste to biofuels and bioelectricity
Biomass residues and waste can be converted into transportation fuels and bioelectricity using transesterification, thermochemical and biochemical pathways

Summary

Introduction

Since the energy crisis of the 1970s, many countries are interested to develop biomass as a fuel source. The present review provides an in-depth overview of the technological details of the conversion techniques of biomass residues and waste to biofuels and bioelectricity. Similar to biomass residues and waste, the spent microalgae biomass can be converted to biofuels after the extraction processing of target products such as oils or/and other high value compounds from microalgae biomass. Environmental-friendly exploitation and conversion of biomass waste into chemical fuels is considered as one of the effective approaches developing renewable energy. Based on several research studies, it was reported that thermal conversion technologies have gained extra attention due to the availability of industrial infrastructure to supply thermochemical transformation equipment that is highly developed, short processing time, reduced water usage and added advantage of producing energy from plastics wastes which cannot be digested by microbial activity [60]. This process involves biomass heating at extreme temperatures (500– 1400 °C), from atmospheric pressures up to 33 bar and

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