The University of Twente recently developed a new technology to cheaply and efficiently capture CO2 from ambient air. The CO2 thus captured is used by the university to grow algae, but can also be used to store solar and wind energy in a closed cycle.
The ‘CO2 air capture unit’, the machine used by the University of Twente to capture CO2 from the air, was designed to capture at least 500 grams of CO2 from the air per day. The CO2 is present in the air a strongly diluted form (approximately 400ppm). As a result, around 1400 cubic meters of air is needed to get one kilo of CO2.
The test set-up used by the university captures CO2 from the ambient air rather than specific flue gases. The capacity of the new air capture unit can be compared to that of four big trees, each planted on a surface area of 50 square meters. The University of Twente will be using the device that captures CO2 from the air to grow algae, a valuable resource for food ingredients and various chemicals in it the bio-based economy. The growth rate of the algae is increased drastically under the influence of CO2.
To achieve the current capacity with which the university aims to capture CO2 from the air the researchers use sorbents, small particles to which CO2 binds. In an ‘adsorber’, the researchers bring non-charged particles into contact with a huge air flow that moves through the unit with a very low pressure drop. As soon as the particles are charged with CO2, they travel up to the top of the unit, which is about six meter in height. From there, gravity propels them to flow down through a heated column, the ‘desorber’, where they deliver their CO2 load. After this, the sorbents will repeat the same cycle again.
Opportunities for greenhouse horticulture
The CO2 -rich gas subsequently travels from the air capture unit to the algae reservoir. Although cooling down and heating requires energy, the net energy consumption of the capture unit is relatively low. The energy costs (estimated at about 75 euros per 1,000 kilograms of CO2) are relatively limited and in line with the current prices on the market for CO2. It is expected that the greenhouse horticulture industry will able to benefit from this technology. “The use of ‘CO2 air capture’ makes it possible to produce CO2 more sustainably, no matter where in the world”, says project leader Dr Wim Brilman.
Sustainable natural gas
The CO2 thus captured can also be used to store solar or wind energy. Using CO2 from the air, together with hydrogen, it is possible to produce methanol and sustainably produced methane (‘natural gas’). Thanks to this interim step, peaks in the supply and demand of energy can be responded to adequately, without any need for batteries. This ‘natural gas route’ will be tested in a ‘Power-to-Gas’ system connected to an existing apartment building complex in Rozenburg.
Source: NWO/Universiteit Twente. Photo: Gijs van Ouwerkerk.
Although they only started growing fresh algae commercially less than a year ago, Hendrik Staarink and his partner Stefano Canziani are fully confident about the future of their business, which they called Algreen. ‘Algae are the vegetables for the future.’
Starink started his studies in Agricultural Water Management at Wageningen University in 2008 and conducted the research for his final project near the Oosterschelde tidal basin in the province of Zeeland. A few visits to crustacean and seaweed farms further kindled his enthusiasm about algae. After reading several books on the cultivation of algae that summer the ball started rolling rapidly.
"We saw some excellent commercial opportunities, taking into account the high prices paid these days for Spirulina algae."
While he was at university he met Stefano, who was studying biotechnology and shared his fascination for algae. ‘We visited algae farms in France together. These are commercial farms, but they were very open about what they were doing. We studied their cultivation system, which they call raceway ponds. Almost all commercial algae are grown in raceways these days. We saw some excellent commercial opportunities, taking into account the high prices paid these days for Spirulina algae. So, we decided to try our hand at this, too!’
‘We first grew Spirulina on an experimental scale in 2014, which marked our first step out of the lab. A great deal of research has been done on the cultivation of Spirulina and we worked with tested techniques and a type of algae that was adapted to the climate in the Netherlands. As a result, we started production on a bigger scale in 2015. We now have an office in Wageningen and grow our algae on a nearby cultivation site.’
"We are directing our sales primarily at the market for healthy juices and good restaurants."
Spirulina is primarily eaten on account of its relatively high protein content. ‘I would like to call it a superfood, but that applies to other vegetables as well. To me, it’s a very special vegetable.’ Spirulina is also chock-full of easily absorbed protein, is an important source of vitamins (e.b. potassium), minerals (particularly iron) and antioxidants (phycocyanine). As a result, it can easily be included in a healthy diet.
Who will be buying your fresh algae?
‘One of our first steps was to conduct market research. We discovered that the market is growing, and that our product is healthy, not too expensive and has numerous uses. You can put it in virtually everything. Many people eat it as a dietary supplement. We are directing our sales primarily at the market for healthy juices and good restaurants. We are a supplier to various small-scale juice bars and shops in Amsterdam. Businesses like that often use powdered Spirulina, and are now replacing this with our product. They tell me that it tastes much better.’
Why do you consider algae to be the vegetable of the future?
‘Because it’s such an easy crop to grow! Harvesting is simple: there’s nothing that needs to be picked or cut. Also, the cultivation of algae can easily be automated and up or downscaled. You don’t need a lot of energy; just a little sunlight. We produce our algae in an unheated greenhouse. Also, we don’t use any crop protection agents. Algae have few requirements with regard to the quality of water (salt content) and don’t emit any greenhouse gases. It’s a very sustainable crop.’
"We distinguish ourselves from the competition by offering a product that is not only fresh, but also sustainably grown."
‘In a conventional greenhouse you need ventilation, which we have no need for. We already apply the principles of Next Generation Cultivation. You see a lot of technology applied to algae that look very interesting on paper, but that are simply not feasible from a commercial perspective. We keep it as simple as possible and make it as complex as necessary. We distinguish ourselves from the competition by offering a product that is not only fresh, but also sustainably grown.’ By offering the algae while they are fresh they not only taste better, but also retain more of their nutrient content, adds Starink. ‘Plus, it cuts costs, because drying the algae requires extra energy.’
Will every grower with access to a tank of salt water be able to grow algae in the future?
‘It’s not quite that simple. Growing algae requires a certain degree of craftsmanship. There’s actually a lot you need to know about: cultivation, certification, biological testing, microscopic testing, harvesting, processing, and so on. We studied the entire process in minute detail. In addition to that, we optimised the cultivation conditions for our algae. We prepare our own nutrient mix. Still, what we do can easily be compared to what other commercial growers of vegetables do.’
"If you operate on a large enough scale you should be able to produce algae profitably in the Netherlands with the variety we developed."
When asked what his production yield is, Starink keeps silent. ‘Even in a cold greenhouse we can earn a little. However, cultivation at this scale takes a lot of labour, relatively speaking. If you operate on a large enough scale you should be able to produce algae profitably in the Netherlands with the variety we developed. We grow an adapted Spirulina variety obtained through selection.’
What will your next step be?
‘Our next challenge is to start operating on a larger scale, cultivation-wise. We would like a bigger greenhouse, preferably with residual heat, to eliminate our winter dip in production. Our most serious competitors are producers of dried algae. We can say that our product is better, but if our fresh algae will become much more expensive, we will be fighting a tough battle,’ explains Starink.
"There is a lot left to discover in the underwater cultivation of vegetables."
‘We are also engaged in expanding our product range. There is a lot left to discover in the underwater cultivation of vegetables. Additionally, our customers keep asking for more varieties of healthy and tasty algae. We are currently busy developing an exceptionally tasty variety of seaweed (a type of macro-algae) and keep our knowledge and expertise about micro-algae up to date through projects like the ‘Luteine 2.0’ project, which won us a prize from the Netherlands Organisation for Scientific Research (NWO). We are currently speaking to investors to enable the business to continue growing and so that more people will be able to enjoy locally grown, super-fresh algae produced by Algreen in the future.’