Although microalgae certainly represent a novel, promising source of several bioactive compounds such as astaxanthin, fucoxanthin, EPA/DHA, and phycocyanin, less attention has been paid to the difference between potential cultivation techniques and their associated environmental and sustainability footprint. Here, location, water availability and quality, cultivation technique, energy source, energy requirements, volumetric productivity, downstream approach, and carbon footprint are key factors in the overall sustainability profile of a given approach. Let’s take a closer look at two of those factors: location and water source.
Location
Location in this context can refer to both geographical location, but also the distinction between cultivation that takes place outdoors and cultivation that takes place indoors. In both cases though, access to a sustainable, stable, and renewable energy source is of critical importance.
Outdoor operations are usually located in warm, sunny climates and have the general sustainability advantage of using natural sunlight to drive the photosynthesis and thereby requiring less energy overall. The disadvantages include increased contamination risk and bioburden, low productivity, limited light utilization and a stronger need for external temperature adjustments – all of which can increase the environmental footprint substantially.
Indoor operations are usually more energy intensive as the process is often driven by artificial high-energy lighting. The advantages however include full parameter control (temperature, pH etc.), enhanced productivity (partly due to being able to cultivate both day and night), lower contamination risk and lower energy requirements for temperature adjustment. Locations with stable, low-temperature climates, low bioburden and access to renewable energy are therefore best suited for indoor microalgae cultivation.
Water availability & quality
Water is the single most important ingredient in microalgae cultivation. Microalgae cultures are predominantly made up of water (biomass density rarely exceeds 10 g/L and is often around 1-4 g/L), so it goes without saying that water availability and quality are critical factors. Sustainability and environmental considerations are tightly linked to the water source in many ways;
- Sustainable, steady water access is of primary importance and water usage must not be at the expense of other industries or general usage.
- Chemical pre-treatment of the water is needed in locations with poor water quality, and this has a negative impact on the overall sustainability and environmental profile.
- The suitability of the local water profile needs to be aligned with the intended culture medium to be used and the microalgae species in question. If the profile is not suitable, adjustments need to be made and these can have negative environmental impacts.
- Controlling water use by ensuring that evaporation rates are minimized is a sustainable step to take. Evaporation rates in open pond, outdoor systems can exceed 20% per day but in closed, indoor systems the evaporation rates can be maintained well below 1%
Overall, this discussion demonstrates that although microalgae cultivation for the production of bioactive compounds is an inherently environmentally friendly process, many details have to be taken into consideration to assess the overall sustainability profile and to compare products produced by different cultivation techniques and in different locations.
An Algalif Blog by Dr. Tryggvi Stefansson, CChief Operating Officer of Algalif
The benefits of astaxanthin for humans will be explored in future blogs – keep up to date by following us at www.algalif.com.
