Green filters of Eucalyptus globulus for microalgae harvesting from freshwater reservoir and reuse of biomass harvested for pellet production

Abstract

Filtration was used for the separation of microalgae from water collected at the reservoir of a Baxe, in north-western Spain, where cyanobacterial blooms are known to occur. The barks of Eucalyptus globulus were used as bed filters. Filters were made with compacted and non-compacted barks of 0.5, 1 and 2 g. Filtration of water with compacted barks showed the best results with yields of 43.12, 76.85 and 63.67 % for the different weights. The microalgae obtained and the vegetation filters were used for the manufacturing of pellets to be used as fuels. Their energy potential was studied according to different parameters such as calorific value, humidity, volatile matter and ash content, to verify the requirements for the use of pellets as fuel in biomass boilers met the criteria according to UNE Standards. These pellets meet the requirements of UNE standards established and could, therefore, be used in boilers as biofuels. Obtaining a high heating value above to 15.00 MJ/kg, greater than 17.00 MJ/kg for all samples except the pellet sample with only microalgal biomass. The samples have a lower ash content of (10 %), with the exception of the microalgae pellet without eucalyptus bark (13.67 %). The use of Eucalyptus bark is a feasible option for the separation of microalgae in aquatic ecosystems. The next step would be to carry out the experiments on a large scale in a reservoir with eutrophication problems, to test if it works correctly under different conditions. Although the aim of obtaining pellets for boilers does not pursue an economic or commercial objective, the results obtained were promising. This would help towards reducing forest waste and as consequence, reducing environmental pollution.