Pellets valorization of waste biomass harvested by coagulation of freshwater algae

• The blooms of green algae can be reduced by using tannins from forest waste.
• Tannins of Eucalyptus globulus bark were a suitable coagulants of freshwater algae.
• Waste biomass from freshwater algae can be used as fuel by their pelletization.

There is a comparison of different coagulants: calcium chloride (20, 60, 120 and 180 mg/L); sodium alginate (10 and 20 mg/L) and tannins of Eucalyptus globulus bark (10 and 20 mg/L) in order to make the most of each method. The results show that 20 mg/L of tannin achieved a recovery efficiency of 95.35 ± 1.16, sodium alginate 90.49 ± 0.53 and 84.04 ± 2.29 for calcium chloride. Taking into account the economic side of the coagulants, obtaining tannins is a profitable process. Bark is waste biomass obtained in the forestry process; therefore it does not involve extra costs. Finally, the feasibility of making pellets from harvested algae was studied, and the results suggest that waste biomass pellets may be used as fuel in boilers in a mixture <54% with other waste sources as Eucalyptus g. branches.