The Sea's best kept secret: the use of seaweed as a source of biohydrogen for clean and renewable energy

Abstract

Sustainable alternatives to fossil fuels and chemicals are needed. The longer we continue to use petroleum-derived materials, the greater the detrimental effects of climate change. To this end, this tutorial review focuses on the use of macroalgae to produce hydrogen as a green fuel and also through third generation biorefineries to produce a complementary range of high value products compared to land-based feedstocks. Algae are important renewable feedstocks that can afford degradable polymers, bioactive compounds (e.g., polysaccharides and polyphenols) and fuels. They also have the potential to mitigate CO₂ emissions by acting as a carbon sink. The aim of this review is to show that different pre-treatment methods and a suite of analytical tools are needed to facilitate effective biohydrogen production from macroalgae. Consideration of pre-treatment methods has not been reviewed previously. We also highlight major challenges to its use including variability between species, environmental conditions, and extraction methods. Understanding macroalgae composition, especially carbohydrate content, is critical in order to optimize biohydrogen and other fuel yields. A variety of screening tools, including mass spectrometric methods, can be used to predict the usefulness of macroalgae species and optimize processing, and thus promote more sustainable research in this field. By optimizing pre-treatment techniques (mechanical, chemical, biological and inhibitor removal), and understanding the composition of algal biomass, hydrogen production from macroalgae can step up and play a role in meeting the world's needs for green energy. Strengths, weaknesses, opportunities and threats to potential seaweed biorefineries are presented.