Biohydrogen Production From Biomass Sources: Metabolic Pathways and Economic Analysis

T M Yunus Khan,M Mofijur,Abrar Inayat,Omar Farrok,Nazifa Rafa,Irfan Anjum Badruddin,Md Sawkat Ali,Shams Forruque Ahmed

doi:10.3389/fenrg.2021.753878

Abstract

The commercialization of hydrogen as a fuel faces severe technological, economic, and environmental challenges. As a method to overcome these challenges, microalgal biohydrogen production has become the subject of growing research interest. Microalgal biohydrogen can be produced through different metabolic routes, the economic considerations of which are largely missing from recent reviews. Thus, this review briefly explains the techniques and economics associated with enhancing microalgae-based biohydrogen production. The cost of producing biohydrogen has been estimated to be between $10 GJ-1 and $20 GJ−1, which is not competitive with gasoline ($0.33 GJ−1). Even though direct biophotolysis has a sunlight conversion efficiency of over 80%, its productivity is sensitive to oxygen and sunlight availability. While the electrochemical processes produce the highest biohydrogen (&gt;90%), fermentation and photobiological processes are more environmentally sustainable. Studies have revealed that the cost of producing biohydrogen is quite high, ranging between $2.13 kg−1 and 7.24 kg−1via direct biophotolysis, $1.42kg−1 through indirect biophotolysis, and between $7.54 kg−1 and 7.61 kg−1via fermentation. Therefore, low-cost hydrogen production technologies need to be developed to ensure long-term sustainability which requires the optimization of critical experimental parameters, microalgal metabolic engineering, and genetic modification.

Highlights

The energy crisis has emerged as the most significant impediment to the advancement of human civilisation
Indirect biophotolysis is a two-step process: i) the first stage involves oxygen producing and carbon dioxide fixing into chemical energy carbohydrates, and lipids; and ii) the second stage is functionally the same and a small sealed photo-bioreactor is used with CO2 synthesis which is divided periodically in the absence of light exposure (Razu et al, 2019)
The results revealed that the microbial electrolytic cell (MEC) system can contribute to a 2.68- and 1.19-times higher efficiency in biohydrogen production than uncoated Ni-Foam and Co3O4.rGO, respectively

Summary

INTRODUCTION

The energy crisis has emerged as the most significant impediment to the advancement of human civilisation Hydrogen production by photofermentation is described by the following equation (Baeyens et al, 2020): 16ATP + N2 + 16H2O + 10H+ + 8e → 16ADP + 2NH4+ For this pathway, instead of water, the green algae gain electrons from heterotrophic fermentation and the catabolic reaction of the endogenous substrate. Green algae rich in carbohydrates are the most common type of microalgae used to produce biohydrogen in this process (Banu et al, 2020) Substrates such as glucose, sucrose, starch, and cellulose are used to enhance the production rate of hydrogen. Indirect biophotolysis is a two-step process: i) the first stage involves oxygen producing and carbon dioxide fixing into chemical energy carbohydrates, and lipids; and ii) the second stage is functionally the same and a small sealed photo-bioreactor is used with CO2 synthesis which is divided periodically in the absence of light exposure (Razu et al, 2019). The biohydrogen production efficiency is increased in the presence of photosynthetic and non-photosynthetic microorganisms

Limitations

Findings

CONCLUSION