The potential of sewage sludge and microalgae: 'green energy' production and environment benefits

Identificador:  TDX:2247

Handle: https://hdl.handle.net/20.500.11797/TDX2247

Autors:  Caporgno, Martín Pablo

Resum:
The depletion of the fossil-fuel reserves is predicted to happen the next few decades. The biofuels production to alleviate the fossil-fuel demand has caused several problems; for example, the biodiesel production from edible oil seeds has shifted out the land from food to energy production. In this context, microalgae have arisen as low-cost and non-edible feedstocks for biofuels production. This thesis investigates different scenarios to produce biofuels from microalgae. Isochrysis galbana, Selenastrum capricornutum, Phaeodactylum tricornutum, Chlorella vulgaris, Chlorella kessleri, Nannochloropsis oculata and Nannochloropsis oceanica are microalgae species used in the experiments. The biomass was mainly converted into two different biofuels: methane, produced by anaerobic digestion, and bio-oil, produced by hydrothermal liquefaction. In case of anaerobic digestion, the influence of several parameters on the methane production has been evaluated: microalgae species, temperature of digestion, substrate to inoculum ratio, biomass pre-treatment and co-digestion of microalgae and sewage sludge. In case of hydrothermal liquefaction, the parameters investigated were: temperature and addition of co-solvents to improve bio-oil yields and quality. Additionally to the benefits of producing biofuels from microalgae, this thesis also evaluates the possibility of recycling nutrients after anaerobic digestion and liquefaction for microalgae cultivation.