Multi-objective optimization of SNG production through hydrothermal gasification from microalgae

Microalgae cultivation for biofuel conversion is widely treated in literature as it could allow reducing fossil fuel consumptions. One of the challenges of this technology is related to the high power and cost requirements for the harvesting and dewatering steps. The influence of dewatering process can be substantially reduced when considering hydrothermal gasification (HTG). This technology, which have already been demonstrated and tested, allows treating feedstock with more than 80% moisture content and can lead to high SNG conversion efficiencies. The object of this paper is to show the combination of microalgae growing and processing coupled with the HTG and syngas purification for SNG grid quality production. The productivity potential for this given technology is evaluated considering global solar radiation data available and the cultivation technology, which can be characterized by photosynthesis conversion efficiency. Systematic system design methodology followed by multi-objective optimization technique using evolutionary algorithms are carried out to provide a set of candidate solutions considering different configurations and conflictive objectives such as efficiency, cost and environmental impact.