Cultivation of microalgae via an innovative technology

February 27, 2015

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.

The waters of the world, oceans, seas, rivers, creeks, lakes and even sea or land ice house a tremendous variety of micro-organisms able to use sunlight as the only source of energy to fuel metabolism. These unicellular organisms, micro- and cyanobacteria, are also capable of incorporating the greenhouse gas carbon dioxide (CO2) into their biomass. The process of sunlight capture and conversion to chemical energy (sugar) is the photosynthesis and leads to liberation of oxygen (O2). With the help of sunlight microalgae thus can be grown on purely inorganic nutrients many of which are considered waste products in our modern society such as nitrogen and phosphorous compounds.

Commercial production of microalgae already has taken place since the 1950's. This production, however, took place in open microalgae raceway ponds with limited control of the production process resulting in low productivity and low product quality. Cost price was still relatively high because of the high costs associated with harvesting of microalgae.

There is a need for a scalable, economically feasible algae production unit that is capable of delivering high value alga-based products as well as biomass, while reducing CO2 emissions. Current large-scale microalgae production is inhibited by the large capital and operational costs. Cultivation of algae always requires the downstream processing steps of harvesting and dewatering. One major issue is cost effectively harvesting algae cells from a solution that is about 99.98 % water. Due to the high water content, harvesting and dewatering algae can be very expensive and can account for 30 % of total production costs. In general, the higher the starting concentration of algae, the lower the harvesting cost.

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, 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 have access to CO2 both in liquid and gas phase, that results in high . A semi-automatic harvesting system was developed uniquely for the ALGADISK reactor to provide an easy and efficient method of biomass collection.

Explore further: Algae to capture CO2

Related Stories

Algae to capture CO2

March 21, 2013

Global warming's effects can be seen worldwide, and many experts believe it's only going to get worse as CO2 emissions continue to rise. Global warming is caused by the emission of greenhouse gases. 72% of the totally emitted ...

'Milking' algal cells proves efficient alternative

January 13, 2014

Biofuel researchers have dramatically improved microalgae hydrocarbon productivity by using non-destructive extraction, akin to 'milking' algal cells as opposed to the conventional harvest and destruction.

Recommended for you

How proteins reshape cell membranes

February 24, 2017

Small "bubbles" frequently form on membranes of cells and are taken up into their interior. The process involves EHD proteins - a focus of research by Prof. Oliver Daumke of the MDC. He and his team have now shed light on ...

New gene for atrazine resistance identified in waterhemp

February 23, 2017

Waterhemp has been locked in an arms race with farmers for decades. Nearly every time farmers attack the weed with a new herbicide, waterhemp becomes resistant to it, reducing or eliminating the efficacy of the chemical. ...

Neanderthal DNA contributes to human gene expression

February 23, 2017

The last Neanderthal died 40,000 years ago, but much of their genome lives on, in bits and pieces, through modern humans. The impact of Neanderthals' genetic contribution has been uncertain: Do these snippets affect our genome's ...

Arctic 'doomsday' seed vault receives 50,000 new deposits

February 23, 2017

Nearly 10 years after a "doomsday" seed vault opened on an Arctic island, some 50,000 new samples from seed collections around the world have been deposited in the world's largest repository built to safeguard against wars ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.