In microalgae cultivation, enrichment of culture water with CO2 facilitates growth and productivity. Farmers’ needs, thanks to SIAD, meet the need to reduce climate-changing gas emissions into the environment by reusing waste from other industrial production, embracing a virtuous cycle of CO2 production and utilization.
Let’s see, then, what microalgae are, what the main cultivation systems are, and how SIAD contributes to the development of this sector through CO2 delivery systems.
What are microalgae
Microalgae are photosynthetic microorganisms found in freshwater and marine systems. They can be unicellular or multicellular. In order to grow, they need light, nutrients and an organic component (carbon source), which, in most cases, is CO2, the key element in initiating chlorophyll photosynthesis, the process necessary for plant nutrition.
In addition to oxygen, the output of the photosynthesis process of microalgae consists of high value-added substances such as:
- Lipids
- Proteins
- Zuccheri
The areas of use of microalgae
Interest in microalgae cultivation is widespread and growing because the substances we have listed, produced in the growth process of these microorganisms, open up great opportunities for use and efficiency in the production of extremely valuable and highly sought-after compounds on the market.
In fact, lipids, proteins and sugars produced by processing microalgae can be used in an important variety of areas:
- Food and nutraceuticals, to produce protein supplements, antioxidants, food additives, etc….
- Aquaculture: for feeding fish with high protein and omega-3 feeds
- Pharmaceutics
- Cosmetics, exploiting antioxidant and moisturizing agents to create, for example, new types of sunscreens
- Agriculture, for the production of biostimulants
- Bioenergy, for the synthesis of bio-fuels
Despite this variety of uses, microalgae production still has enormous room for growth (especially in Italy), and it is still considered, to this day, a relatively “young” crop compared to more traditional crops, leaving great room for movement for those who have the opportunity to embark on this path, structuring themselves appropriately.
How microalgae cultivation takes place: tanks or photobioreactors
The main factors that influence the process of chlorophyll photosynthesis allowing microalgae growth are:
- Light Intensity
- pH levels
- Concentration of CO
- Temperature
- Water salinity
Microalgae cultivation techniques are mainly based on two different systems:
- Open systems (tanks)
- Closed systems (photobioreactors).
Open systems consist of using large tanks, canals, ponds, low water circulation units (as low as 20-30 cm) as the growing environment. The culture is agitated by means of blades mounted on radial motors that prevent sedimentation of the biomass and promote exchange with the external environment. They are most suitable for fast-growing microalgae species that thrive well under more extreme environmental conditions (e.g., spirulina).
The advantages provided by open systems are definitely lower management and initial investment costs and a greater possibility of scale-up. But at the same time, they allow more limited productivity, with high use of fresh water and CO2.
Closed systems represent a more efficient production solution based on clear plastic glass photobioreactors of various shapes, of which the best known are tubular and flat-plate ones.
Since this configuration has no exchange of matter with the external environment, it is necessary to supply CO2 through appropriate diffusers or with a pump-injection system depending on the type of closed reactor employed.
The advantages of using a microalgae photobioreactor fleet are, therefore:
- Better control of process variables such as pH and temperature and consequently greater process optimization
- Reduced contamination with the external environment making this configuration an ideal choice for the food industry
The main disadvantages are higher system design, maintenance and upkeep costs than open systems.
SIAD and the provision of CO2 for microalgae growth.
Enrichment of microalgae culture water with CO2 generates:
- +20% estimated productivity
- Maintaining the optimal pH level between 7 and 9
- Avoid CO2 deficits in the environment that can lead to crop damage.
With long experience in the use of technical gases in water treatment, the group SIAD can provide highly efficient CO2 dissolution systems that can be adapted to any photobioreactor. Gas delivery can be regulated by an appropriate control system, depending on continuous monitoring of the parameters most useful for algal biomass growth.
Thus, the gas supply system consists of:
- CO2 tank + evaporator (in case of high consumption of carbon dioxide) or cylinder pack (for lower consumption)
- Safe gas delivery system (Safety and control valves, pressure indicators, etc…)
- Control panel and appropriate analysis and monitoring probes
We can carry out pilot-scale tests in advance to assess its concrete impact on the crop and then proceed to the implementation of the final plant, supporting the customer in the various design stages.
