Welcome to the arid canyons, steep ravines and squalid bushes of Almería, in the southeast of Spain. This region is the driest place and receives the highest number of sun hours in Europe (1). These extreme conditions are not amenable to most life, however they represent an ideal location to test the conversion of solar energy into biomaterials (e.g. food, fuel, fertilisers, etc.) This process, carried out by plants and microorganisms, is called photosynthesis and sustains all complex life on our planet. Photosynthesis is however a very inefficient process, as Isaac Asimov, the popular American science-fiction writer, already noted in 1968 in his eponymous book (2). The reason is that RuBisCO, the enzyme at the heart of the process performs poorly. Plants compensate for this by producing large quantities of RuBisCO, to the point of being the most abundant enzyme in nature. That is for plants, what about algae? At the University of Almería professor Gabriel Acién overlooks a raceway pond holding 4,000 litres of cyanobacteria (see picture). “Our goal is to produce the highest amount of biomass at the lowest price” exclaims under his straw hat as he strolls the outdoor facilities in the heat of the day. He moves into a greenhouse where a paddleboard stirs another raceway. The temperature is suffocating. “We aim to harvest 20% of the volume of the pond every day year round, and in summer we can increase this to up to 40%”. This is a huge production rate. Microalgae are indeed the most efficient of the microorganisms in transforming sun light into biomass. Not only that, they are also safe, growth fast, extract carbon dioxide from the air, and have simple requirements. That last point is particularly interesting because it means they can utilise sewage as a food source transforming it into valuable biomass (3). Professor Acién showcases a water treatment facility in El Toyo, not far from the university, to a group of a summer students. “Light is the limiting factor in photosynthesis. In raceways, we must keep the depth of the pond to a maximum of 20 cm”, he explains. Light may be the next gold; an inexhaustible source of energy that captured by microalgae can, not only substitute fossil fuels, but also decarbonise the atmosphere. Read more: 1) Tout, D. G., “South-east Almería province, Spain – the driest region in Europe.” Weather (1987). https://doi.org/10.1002/j.1477-8696.1987.tb04899.x, last accessed July 2024. 2) Asimov, I. "Photosynthesis, 193 S." (1968). 3) Acién Fernández, F. G., et al. “The role of microalgae in the bioeconomy.” New Biotechnology 61 (2021): 99-107. https://doi.org/10.1016/j.nbt.2020.11.011. Photograph: Experimental raceway at the University of Almería, Spain.