(598a) Utilization of Marine Macroalgae for the Production of Biofuels and Biomaterials Via Hydrothermal Pyrolysis Process

Algae are known as the third-generation feedstock which are highly promising to be used for the synthesis of bio-based fuels, energy, and materials via biochemical, thermochemical, and biological conversion techniques. Compared to land biomass, algae have the advantages of having faster growth rates, in addition to potentially much higher yields per unit surface area of land. Furthermore, algae are unique since they contain carbohydrates, lipids, and proteins, which make them more potential for producing wider range of products via various processes. A significant shortcoming of algae as biofuel feedstock is the need of dewatering and drying processes which are both energy- and cost-intensive. Eliminating dewatering and drying pre-processing, prior to the conversion process, will be a significant cost and energy reduction.

In this study, three distinct species of marine macroalgae, i.e., Euchema cottonii, Sargassum sp, and Ulva lactuca, were used as feedstock for the synthesis of hydrochar and organic liquid via hydrothermal pyrolysis (HTP) process. HTP process is a thermochemical process that converts wet biomass materials to a solid, liquid, and gas products. Under sub-critical conditions, water in the HTP reactor stays in liquid form and acts as a reaction medium to promote the breakdown and cleavage of chemical bonds in the solid biomass. The absence of liquid-to-vapor phase change of the water makes the process significantly less energy intensive compared to a process that involves water vaporization or drying. The temperature range for HTP process is from 180-370^oC. At lower reaction temperature range (180–240^oC), known as hydrothermal carbonization (HTC), the main product is hydrochar, which is the solid product. The HTP process at higher temperature range, known as hydrothermal liquefaction (HTL), will produce liquid, i.e., bio-oil, as the primary product.

The focus of this research was to evaluate the effects of feedstock and HTP process parameters on the yields and selectivity, along with physicochemical properties, of the solid and liquid products. HTC reaction temperature and retention time were the major parameters that were varied. Retention times varied from thirty minutes to two hours and the temperature range was focused between 200^oC and 300^oC.

Various analytical and characterization testing will be conducted on the liquid and solid products of the HTP process. The characterization techniques will include CHNOS elemental analysis, approximate analysis (TGA), specific surface area, porosity, heating value, and microstructure (SEM analysis) of the hydrochar products. The liquid analysis to evaluate chemical compositions will be performed by using gas chromatography techniques. Specific attention will be given on the fate and the recovery of the lipid component. When the desired product is hydrochar, the lipid component in algae feedstock will remain in the solid product. Compared to extracting lipid from the original algae feedstock, extracting lipid from algae-derived hydrochar is significantly much easier due the “opening” of the solid structures. Reduction of the energy and cost requirements of extracting lipid from algae will be a noteworthy progress toward the commercial utilization of algae as renewable feedstock for producing biofuels and materials.