Biohydrogen production from microalgae—Major bottlenecks and future research perspectives

Abstract

The imprudent use of fossil fuels has resulted in high greenhouse gas (GHG) emissions, leading to climate change and global warming. Reduction in GHG emissions and energy insecurity imposed by the depleting fossil fuel reserves led to the search for alternative sustainable fuels. Hydrogen is a potential alternative energy carrier and is of particular interest because hydrogen combustion releases only water. Hydrogen is also an important industrial feedstock. As an alternative energy carrier, hydrogen can be used in fuel cells for power generation. Current hydrogen production mainly relies on fossil fuels and is usually energy and CO 2 -emission intensive, thus the use of fossil fuel-derived hydrogen as a carbon-free fuel source is fallacious. Biohydrogen production can be achieved via microbial methods, and the use of microalgae for hydrogen production is outstanding due to the carbon mitigating effects and the utilization of solar energy as an energy source by microalgae. This review provides comprehensive information on the mechanisms of hydrogen production by microalgae and the enzymes involved. The major challenges in the commercialization of microalgae-based photobiological hydrogen production are critically analyzed and future research perspectives are discussed. Life cycle analysis and economic assessment of hydrogen production by microalgae are also presented.

Use of Hydrogen as Fuel: A Trend of the 21st Century

“…The production of H 2 requires the optimization of several parameters such as the selection of the microalgal strain, growth medium, pH, temperature, light, chlorophyll concentration and photobioreactor [107,108]. Many works describe the production of H 2 by many strains of microalgae using sulfur-, phosphorus-or nitrogen-poor medium [109,110].…”

Biohydrogen Production From Biomass Sources: Metabolic Pathways and Economic Analysis

“…Following the initial failure of continuous biohydrogen production using S-deprived wild type C. reinhardtii, the National Renewable Energy Laboratory in collaboration with the researchers at UC-Berkeley developed a two-stage continuous phase system that promoted an aerobic growth phase and a subsequent anaerobic hydrogen evolving phase (Nagarajan et al, 2021). Their design reduced the photobioreactor costs to $1 m −2 , determined the selling price of hydrogen at $8.97 kg −1 (or ¢22.80 kWh −1 ), and further revealed the capital costs of custom-built photobioreactors can be drastically reduced if open ponds are used.…”

“…With a production of 55 million tonnes every year, hydrogen is an important eco-friendly industrial feedstock due to its high energy density (Wang and Yin, 2018;Bolatkhan et al, 2019;Gielen, 2019). The hydrogen market is experiencing up to 10% growth year on year and is forecast to reach over $191.80 billion in 2024 (Bolatkhan et al, 2019;Nagarajan et al, 2021). However, the commercialization of hydrogen as a fuel suffers major bottlenecks in terms of the techno-economic and environmental feasibility of conventional methods (Das et al, 2019), the dependence on fossil fuels to drive some processes (Dawood et al, 2020), and challenges related to transportation and storage (Nagarajan et al, 2017;Abdalla et al, 2018).…”

Biohydrogen from Microalgae: Production and Applications

“…Specifically, during the light phase, an electron transport chain is generated along with photosystems II (PSII) via the plastoquinone (PQ) pool, cytochrome b6f complex (Cyt b6f), and photosystems I (PSI) due to the light energy received as photosystems are associated with light-harvesting complexes I and II (LHC I and LHCII), consisting of numerous photoreceptive pigments. These electrons through PSI leave the electron transport chain and reach the final acceptor ferredoxin (Fd) [8,9]. In recent years, many green systems have focused on algal biomass to obtain energy from living matter.…”

“…Hydrogen is an energy carrier with a high calorific value of 122 kJ/g, which is about 2.75 folds than fossil fuels, and it is also an environmentally friendly molecule since it only gives water as a by-product of its combustion [62]. For this reason, hydrogen environmental damage ratio has been estimated as 1, compared to that of several hydrocarbon fuels about 20 times higher [8,63]. Hence, hydrogen is considered as the best alternative to fossil fuels, which usage is supposed to be drastically reduced by 2050, according to the 2015 Paris Climate Agreement.…”