The human-centric goals of food and energy production, as well as water provisioning, can be met with minimal environmental impact if sustainable sources of food, energy and water are identified. Systems thinking can support the advancement of a sustainable society by maximising synergies and minimising trade-offs across ecosystem services in the food-energy-water nexus.
Techno-ecological synergies in manufacturing processes can aid in balancing supply and demand for ecosystem services across scales, from a single process to the entire life cycle of a product. This can not only help to alleviate negative environmental effects, but can also help to reduce demand overshoot for each ecosystem service through the life cycle efficiency of different materials. Bioresource-based production processes differ significantly from conventional production processes in terms of the trade-offs they present within the food-energy-water nexus. In order to replace the current fossil-fuel based economy with a circular bio-economy, biological principles must be incorporated into production processes.
Algae are protein-rich and have been used as food and feed for centuries. Macroalgae (seaweed) is widely consumed around the world, predominantly in Asia. Algae are also significant participants in the world's carbon cycle. The presence of phytoplankton - a type of microalgae, makes oceans one of the largest carbon sinks in the world. The ability of algae to sequester carbon has been used to design carbon removal systems that are less complicated and take up less space than other carbon capture technologies, while their ability to remove contaminants has been used in the remediation of polluted sites.
Over the last decade, there has been an increase in interest in energy-generating façades due to the trend toward net-zero buildings. Algal photobioreactor façades take advantage of algae's high photosynthetic efficiency to generate high-quality biomass, which may be used for power or heat generation. Algal biofuels have a lower environmental impact and a higher yield per acre than first-generation and second-generation biofuels. Carbon dioxide emissions from conventional combustion processes can be used by algal bio-reactor façades to make them viable small-scale carbon footprint offset systems. Increased daylight encourages algal growth in bio-reactor façades, providing greater shade for the building. A building with such a dynamic and adaptive shading device could help to reduce solar gains, resulting in lower heating, ventilation, and air-conditioning (HVAC) energy costs. Because temperature tolerance varies by algal species, they are best suited for large-scale projects in regions with average temperatures between 15°C - 30°C. Microalgae bioreactor panels may be a long-lasting solution for urban skyscrapers for improving building envelope energy performance and addressing climate change adaptation.
The depletion of natural resources, the high carbon footprint of building materials and processes, and linear waste management systems are all exacerbating environmental issues. As the world's building stock is expected to double by 2060, low-carbon alternatives to traditional building materials are becoming increasingly important. Algae can be incorporated into roofs and facades, as fibres or additives into pavements, particulate panels, and polymeric composites, and as ash into cement composites. Algal bricks and other algae-incorporated building materials have the potential to transform the construction industry from a major carbon emitter to a carbon absorber.
Regional-scale algal production is complicated since no single algae strain or culturing technique can accomplish all the goals, such as desired biofuel production volumes and appropriate levels of water remediation. It is therefore unrealistic to evaluate algal systems as a simple input-output technology. To achieve the desired commercialization objectives, the performance of algal systems needs to be examined for food-energy-water nexus concerns specific to the region.
Cross-sectoral planning and integration with other technologies are necessary to avoid negative externalities and maladaptation. Holistic evaluations of potential algal system projects can support policy coherence in the food, energy and water sectors and help to inform investment and research decisions.
Algae are a largely unexplored resource with immense potential for addressing the energy and food security crises, as well as environmental deterioration. Whether it be cultivated in raceway ponds, bioreactors or aquaculture systems, or harvested from wild stocks, optimizing the use of this sustainable super-crop is essential for the development of a circular economy. When resource management issues are viewed through the lens of algal bioresources, disruptive changes in food and energy production, wastewater remediation, and greenhouse gas mitigation can occur. Innovation in algal biotechnology can lead to the discovery of novel strains and techniques, which can inspire the development of new algae-based products and environmental services, leading to new jobs and markets.
The world needs to warm up to the concept of an 'algal culture', which refers to the very real potential of cultivating algae, as a sustainable alternative to burning fossil fuels - the black gold of the last few centuries.
(Ann Rochyne Thomas is a bio-climatic spatial planner and founder of Centre for Climate Resilience - a sustainability and climate change advisory.)
