Integration of an innovative offshore pilot plant for the cultivation of Microalgae in the harbor of Harburg


Funding bodies: BioProMare, BMBF
Project partners: TUHH I^3 Junior Projects
Project volume: 50.000 €
Timeframe: 02/2020 – approx. 06/2021
Over the last decade climate change and a strategy of natural resources preservation led to a dramatic increase in the interest for aquatic biomass. Along with mitigation of the environmental pressure and a reduction of waste streams such as CO2 and heat emissions, microalgae can supply food, feed, pharmaceutical and power industries with a number of value added products. Microalgae are microscopic cells growing in aqueous media. They are able to use sunlight energy via photosynthesis and to transform inorganic compounds into valuable organic materials. Compared to terrestrial crops, they possess enormous growth rates without a dependency on fertile soil.
Microalgal growth and composition is affected by many different factors, namely light and nutrient availability, pH and temperature. In general, cultivation processes can be divided into open and closed systems. The design depends significantly on the strain, cost of land, the potential application of the final product, the source of CO2 and the nutrients required. Open systems, mainly represented by open ponds, consist of shallow channels where the algal culture is circulated by pumps or paddle wheels. They offer relatively low construction and operating cost and are simple to maintain. However, open systems are susceptive to contaminations and weathering and have a reduced availability of sunlight for the single cells. The disadvantages of open systems can be avoided by closed and transparent photobioreactors. Their design parameters are leading to a basic classification into tubular, flat panel or column systems. Next to a better control of parameters like temperature, pH and nutrient concentration, these systems ensure a lower contamination risk, better mixing and a better availability of sunlight. However, they come with a higher cost, difficult scale up, material wear, and with a sophisticated cooling system.
Crucial challenges for the production of microalgae are the efficient and sustainable use of nutrients, energy and areas. Thus, the development of a swimming photobioreactor system for port cities is attractive. First of all, such a system can reduce and clean up waste streams of adjacent industries by fixing nutrients, e.g. CO2, without occupying valuable land. At the same time, the heat capacity of the surrounding water provides cooling and a constant temperature which is desirable for microalgal growth. Furthermore, the wave energy is leading to a supplementary smooth mixing within the reactor.
The objective of this project is to design, build and operate a swimming pilot-photobioreactor to demonstrate an efficient offshore cultivation of local, sweet-water microalga Tetradesmus obliquus.