Challenges and opportunities for hydrogen production from microalgae

Abstract

The global population is predicted to increase from ~7.3 billion to over 9 billion people by 2050. Together with rising economic growth, this is forecast to result in a 50% increase in fuel demand, which will have to be met while reducing carbon dioxide (CO2 ) emissions by 50-80% to maintain social, political, energy and climate security. This tension between rising fuel demand and the requirement for rapid global decarbonization highlights the need to fast-track the coordinated development and deployment of efficient cost-effective renewable technologies for the production of CO2 neutral energy. Currently, only 20% of global energy is provided as electricity, while 80% is provided as fuel. Hydrogen (H2 ) is the most advanced CO2 -free fuel and provides a 'common' energy currency as it can be produced via a range of renewable technologies, including photovoltaic (PV), wind, wave and biological systems such as microalgae, to power the next generation of H2 fuel cells. Microalgae production systems for carbon-based fuel (oil and ethanol) are now at the demonstration scale. This review focuses on evaluating the potential of microalgal technologies for the commercial production of solar-driven H2 from water. It summarizes key global technology drivers, the potential and theoretical limits of microalgal H2 production systems, emerging strategies to engineer next-generation systems and how these fit into an evolving H2 economy.

Keywords: algae; fuel; hydrogen; renewable energy; solar; water.

Figure 1

Overview of the photosynthetic microalgal H2 production from water. Aerobic (a) and anaerobic (b) stages of the two phase H2 production and Micro‐oxic continuous H2 production (c). Proton (H⁺) flow is marked with dashed lines, electron flow with continuous lines. Potential engineering targets for improved H₂‐production are marked in red (labels #1–5) and described in detail in section ‘Biological challenges and bottlenecks for microalgal H2‐production’. LHCII : light‐harvesting antenna proteins of photosystem II; PSII : photosystem II reaction centre; PQ : plastoquinone pool; Cytb ₆ f: cytochrome b₆f complex; PC : plastocyanin; PGRL1: proton gradient regulation like1 protein; LHCI : light‐harvesting antenna proteins of photosystem I; HydA: hydrogenase A; PETF: ferredoxin; FNR : ferredoxin (flavodoxin)‐NADP(H) reductase; NDH : NADPH‐dehydrogenase.

Figure 2

Hydrogen budget and potential market in G20 countries. (a): Allocated budget per country for the development of hydrogen technology. (b–f) Patents filed in the respective countries. Numbers derived from the European Espacenet world wide database keyword search using: Hydrogen + Energy, Hydrogen + Production and Hydrogen  +  Production  +  Renewable (renewables are shown as absolute patent numbers above bar), Hydrogen + Storage, Hydrogen + Fuel cell, Hydrogen + Transport.