Two pilot projects in Sweden are using algae cultivation to achieve a number of sustainable effects. Besides reducing carbon dioxide emissions and purifying waste water to minimise over-fertilization, the algae cultivation produces energy-rich algae mass that can be used for biodiesel and animal feed.
Research into algae and how it can be used for various sustainability purposes is increasing around the world. Apart from research in Canada, it has never been carried out as far north as Umeå, Sweden. This is where two pilot projects are using algae cultivation to convert unwanted substances for utility companies. The aim is to mass-produce algae while also scrubbing flue gases and municipal wastewater. This both cuts CO2 emissions and produces a useful raw material that can contribute other sustainability effects. The algae is filtered, sedimented or centrifuged from the liquid for use.
A range of benefits
Like other plants, algae needs carbon dioxide, nutrition and sunlight to grow. But algae offers a number of benefits that make it particularly interesting from an environmental point of view. First, algae grows much faster than terrestrial plants, at up to 100 tonnes dry weight per hectare per year, which means it needs a smaller area for cultivation. Secondly, it can be grown in pools on land that’s not suitable or profitable for agriculture.
Both pilot schemes are located in Umeå in the north of Sweden. The larger of the two is based close to the Dåva CHP combined heat and power plant. The smaller project is located at a wastewater treatment plant run by the municipal water and sewage company Vakin.
Two different applications
The pilot project at Dåva sees the combined power and heating plant pump flue gases into the algae facility, providing the algae with carbon dioxide. To provide nutrition, the facility uses composting leachate and residual streams from the pulp and paper industry. The algae facility consists of four open dams of 6m³ or 20m³ in size, and a laboratory unit with the necessary equipment. Four dams allow testing with different algae and different kinds of water to compare and optimise the results.
The project relating to Vakin’s wastewater plant instead uses flue gases from biogas combustion to provide carbon dioxide for the algae, and the nutrition source is municipal wastewater influent, which provides nitrogen and phosphorus. The arrangement consists of an 880 litre photobioreactor placed in a greenhouse with a removable roof to let in as much sunlight as possible.
A promising route to increased sustainability
The pilot projects started in 2014 and are run by a broad consortium of academic institutions and local and regional authorities, as well as energy, wastewater and heating companies. They include Umeå and Luleå University, SLU (the Swedish University of Agricultural Sciences), SP Processum and SP (in Borås), Vakin, Umeå Energi and Ragnsells. The algae pilot projects are showing promising results in using algae to solve both environmental and climate challenges. They reduce CO2 emissions while producing energy-rich biomass that can be used for anything from energy production or biodiesel to animal feed and fertilizer.