(563d) Recycle of Water and Nutrients Using Anaerobic Digestion of Algal Hydrolysate Obtained by Flash Hydrolysis

Anaerobic digestion is considered as an effective alternative to convert biomass into energy. The process aims to transform the complex compounds present in organic matter in much simpler compounds; through the whole process gas is generated comprised approximately by 60% methane and 40% carbon dioxide called biogas, and also a solid byproduct is obtained with fertilizer characteristics.

In previous studies it was demonstrated that by means of in house developed flash hydrolysis about 60-80 wt% of proteins in microalgae could be extracted within few seconds in the temperature range of 200-325¢ªC under subcritical water conditions. After the flash hydrolysis of algae slurry a liquid algae hydrolysate is obtained that is rich in nitrogen (peptides and amino acids) and organic carbon and is near-neutral (pH 6.2-7.0) liquid, making it an attractive feedstock for the anaerobic digestion process. In order to maximize the biogas production, as well as the water and nutrients recycle to algal farm, factors such as the feedstock C/N ratio, pH, solids load, solids retention time, temperature, COD and BOD will be monitored and modified. After the anaerobic digestion process most of the organic compounds originally present in the algal hydrolysate will be transformed into much simpler compounds and inorganic salts mostly dissolved in water. The recirculation of the anaerobic digestion final product will be evaluated as a useful source of dissolved nutrients for algae cultivation.