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Project

The ALGADISK project aims to develop a biofilm reactor for algae biomass production which could compete with current algae cultivation technologies (e.g. open-pond and tubular photo-bioreactors). Biofilm formation is a widely observed characteristic of microalgae, which is considered as one of the main problems of tubular, flat-plate and other suspended photobioreactors. While in ALGADISK reactor, biofilm formation is enhanced and supported due to its special design, allowing harvesting high dry solid content biomass, reducing water loss and decreasing energy consumption. The reactor is scalable, modular, contains a sensor and control system to follow and keep growth conditions in optimal range, real time (e.g. pH and volume of medium, nutrient concentrations, temperature). Reactor consists of vertically positioned plastic disks and non-transparent tanks, in which disks are placed half way in growth medium. Surfaces of disks are modified in order to intensify primary biofilm formation and provide sufficient cell number for regrowth of biofilm after harvest. Continuous rotation of disks provides proper wetting of the whole surface and light distribution over the biofilm. In addition, negative effects of saturating light intensity are precluded by cyclic movement of biofilm from light part into the dark tank. Due to the position and orientation of disks, light utilization of reactor can reach a high level, resulting in high biomass productivity. Modules are covered with transparent, removable lids in order to reduce risk of contamination and protect biofilm from extreme weather changes. During the process of system development, concept of CO2 capturing from flue gases was one of the main aspects of design. Reactor is capable of enhancing CO2 to dissolve in the growth medium, just as to reach a high CO2 percentage in the air phase, thus microalgae have access to CO2 both in liquid and gas phase, that results in high biomass production. A semi-automatic harvesting system was developed uniquely for the ALGADISK reactor to provide an easy and efficient method of biomass collection.

Within the Algadisk concept microalgal biofilm growth is exploited resulting in an efficient production process for microalgal biomass. The biofilm on the disk is slowly rotated trough water and gas. The water is enriched with the essential nutrients necessary for microalgae growth such as carbon dioxide, nitrate, urea or ammonia and phosphate. Depending on the rate of microalgae growth the necessary amount of nutrients are automatically dosed to the Algadisk system. The gas phase is enriched with carbon dioxide and, in fact, any combustion gas could be used since these are very rich in carbon-dioxide (CO2) (of course it depends on the application of the final product whether it is possible to use specific waste combustion gasses). The addition of CO2 is simple controlled via monitoring the pH of the liquid. When CO2 is almost depleted, the pH will rise and fresh CO2 will be supplied. This is a simple but robust way to control both pH and CO2 levels in the ALGADISK system.

The Algadisk surfaces are coated with dedicated polyelectrolytes in order to speed up algae attachment and allow for a rapid inoculation procedure. On the long run we envision attachment of specific microalgae on the disk surface in order to ensure monocultures for the production of specific products.

Preliminary laboratory scale studies have shown consistent biomass production and weekly a thick microalgal biofilm could be harvested. A new and innovative harvesting device has been developed for ALGADISK able to directly harvest the dense biofilm with a dry matter of 150 gram per litre. At a daily light input of 35 mol photons per m2 of disk surface areal productivities of 20 gram per square meter disk per day have been reached consistently. These circumstances are comparable to those in central Spain where the first 4 m2 prototype was tested.

The ALGADISK prototype was installed at BFC biogas plant in Almazán, Spain in May 2014. The location provides an optimal environment for biofilm growth by its geographical features. The reactor tanks are installed in east-west direction to let optimal light reach the surface of the disks while at the same time prevent from strong sunlight. After the prototype installation the field test started with bi-weekly harvesting cycles and was running until the end of October 2014.

The three-year long project started in January 2012 and going to end in December 2014. The project is coordinated by the Confederacion Espanola De Fabricantes De Alimantos Compuestos Para Animales (Spain) with the participation of the below mentioned Small and Medium Enterprises (SMEs): Ateknea Solutions Hungary Kft. (Hungary), European Biomass Industry Association (Belgium), Fundacion CESFAC (Spain), Olajgép-Tec Ipari Karbantartó, Szerelő és Kivitelező Kft. (Hungary), Biogas Fuel Cell SA (Spain), Umwelt-Technik Csőtisztító Építő és Szolgáltató Kft. (Hungary), Caglar Dogal Urunler Yenilenebilir Enerji Gubre Gida Ve Tarim Ithalat Ihracat Sanayi Ticaret Limited Sirketi (Turkey), Cranfield University (United-Kingdom), Wageningen University (Netherlands), Bay Zoltán Alkalmazott Kutatási Közhasznú Nonprofit Kft. (Hungary), AlgEn, center za algne tehnologije, d.o.o.  (Slovenia).

The project received founding through the European Union’s Seventh Framework Programme under grant agreement number 286887 (FP7 / 2007-2013). The implementation of the project is managed and controlled by the Research Executive Agency (http://ec.europa.eu/research/rea)

 

 

THE NEED

There is a need for a scalable, economically feasible algae production unit that is capable of delivering high value alga-based products (animal and human nutrients, biofertiliser) as well as biomass (biodiesel precursors), while reducing CO2 emissions. Current large-scale microalgae production is inhibited by the large capital and operational costs.

SOLUTION

One system that has been developed to address the issue of high harvesting cost is the biofilm-based system. The solution is based on a modular, scalable and automatic biofilm reactor – with automatic and continuous harvesting system – for algae biomass production with low installation costs.

FUNDING

This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 286887