The present project aims at scaling-up a low-cost microalgae-based biotechnology for the optimum recovery of CO2 from biogas and nutrients from digestate (liquid waste produced) for the production of a high value bio-fertilizer, clean water and an enriched methane gas. In addition, the system allows taking advantage of the oxygen excess produced during the process of carbon dioxide fixation, for the removing of hydrogen sulphide (H2S) in the biogas.
The process is based on the ability of microalgae to capture CO2 via photosynthesis in the presence of sunlight in symbiosis with both a specific bacterial consortium capable of removing H2S (biogas contaminant). The carbon dioxide absorbed is then subsequently converted into microalgae biomass in the High Rate Algae Pond (HRAP), using the digestate produced as nutrients source (N, P, K). The HRAP is interconnected to a separate absorption column (scrubber) where both CO2 and H2S are sparged from its bottom and absorbed into the microalgal culture broth. An upgraded biogas (rich in CH4) and algae biomass are obtained.
The wet microalgae biomass obtained after the HRAP is then harvested through an innovative system. The harvesting system consists of a unique patented pre-concentration system (coalescer) based on the principle of lamellar separation of suspended particles from liquids. The preconcentrated algal slurry from the coalescer will then be dewatered on a dewatering table with a sieve belt press. The press cake will be air dried in a belt-tunnel dryer and followed by a conventional centrifugation and stove drying for the further processing.
After the drying process, a dried algae biomass is obtained ready to extract the high added value products out. The process consists of the extraction of a plant hormone rich fraction from the algae biomass with the use of a green solvent and the remaining acqueous phase is collected as an enriched biofertilizer product.