Furthermore, due to their harsh environment and phototropic life, algae are often exposed to high oxidative and free-radical stresses. Marine algae do not require freshwater or arable land to grow, maximising resources that can be used for additional food production or other cash crops. Terrestrial agriculture already requires approximately 75% of the total global freshwater with animal protein in particular requiring 100 times more water than if the equivalent amount of protein was produced from plant sources.

Seaweed and microalgae have higher protein yield per unit area (2.5–7.5 tons/Ha/year and 4–15 tons/Ha/year, respectively) compared to terrestrial crops, such as soybean, pulse legumes, and wheat (0.6–1.2 tons/Ha/year, 1–2 tons/Ha/year, and 1.1 tons/Ha/year, respectively). Algae use for protein production has several benefits over traditional high-protein crop use in terms of productivity and nutritional value. Some species of seaweed and microalgae are known to contain protein levels similar to those of traditional protein sources, such as meat, egg, soybean, and milk. Seaweed and microalgae are considered a viable source of protein. Alternative protein sources and production methods are required to fulfil the demand of consumers and to meet predicted global protein requirements. In particular, protein is one of the main nutrients that will be in short supply in the future. Previously utilised methods of intensifying agriculture will soon no longer be an option due to the high impact trade-offs they have on the environment, including fragmenting natural habitats and threatening biodiversity, production of greenhouse gases from land clearing, fertilisers and animal livestock production, and nutrient run-off from fertiliser damaging marine, freshwater and terrestrial ecosystems. However, worldwide food production is now facing a greater challenge than ever before. A combination of improved agricultural food production methods and an increase of average per capita income have led to a decrease in global hunger over the last half-century, despite a doubling of the world’s population. The global population is expected to increase by over a third (2.3 billion people) by 2050, requiring an estimated 70% increase in food production. Applications of algae in human nutrition, animal feed, and aquaculture are examined.

Moreover, existing protein enrichment methods used in the dairy industry and the potential of these methods to generate high value ingredients from algae, such as bioactive peptides and functional ingredients are discussed. Protein extraction methods applied to algae to date, including enzymatic hydrolysis, physical processes, and chemical extraction and novel methods such as ultrasound-assisted extraction, pulsed electric field, and microwave-assisted extraction are discussed. This review details the characteristics of commonly consumed algae, as well as their potential for use as a protein source based on their protein quality, amino acid composition, and digestibility. Algae do not compete with traditional food crops for space and resources. Macroalgae (seaweed) and microalgae are examples of under-exploited “crops”.

Population growth combined with increasingly limited resources of arable land and fresh water has resulted in a need for alternative protein sources.

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