1. Introduction
Due to ever growing concerns over depleting fossil fuel resources and their negative ecological impact, the development of environmentally benign and efficient processes for converting biomass energy to clean transportation fuels, chemicals and other value-added materials has received a worldwide attention. The advantages of using biomass are three-fold: it is a distributed, abundant and carbon-neutral resource. However, the use of terrestrial biomass for energy and fuels production is frequently queried by the relatively low solar energy conversion efficiency of plants and potential undesirable effects on the arable land for food production. From this point of view, the utilization of aquatic biomass via thermochemical conversion processes (e.g., liquefaction, gasification or pyrolysis) is more advantageous since it does not compete with agriculture for land usage [1], [2], [3] and [4]. In terms of solar energy utilization efficiency, some types of aquatic biomass are an order of magnitude more efficient than common crops and most terrestrial biomass.