(302c) Hydrochar Obtained from Hydrothermal Carbonization from Lipid Extracted Algae and Its Use As Solid Fuel

Authors: 
Jena, U., New Mexico State University
Hoekman, S. K., Desert Research Institute
Microalgae have tremendous potential as a feedstock for production of liquid biofuels such as biodiesel and renewable diesel along with value-added co-products. Both biodiesel and renewable diesel production pathways involve a lipid extraction step that results in significant solid residues (60-80%) known as ‘lipid extracted algal reside (LEAR). Suitable utilization of LEAR will be important to the overall cost economics of algal bio-fuels production. In the present study, we evaluate LEAR as a bioenergy feedstock- we specifically investigate the pelletization and combustion properties of algal hydrochar obtained from the hydrothermal carbonization (HTC) process. HTC of Scenedesmus dimorphous (whole biomass and LEAR) was performed using a 2-L Parr reactor at 175 oC for 30 min holding time to obtain the hydrochar. Combustion of hydrochar and untreated biomass samples was conducted in a controlled environment using a thermogravimetric analyzer (TGA) at 25-900 oC ( heating rate of 40-100 oC/min) and was compared with a conventional coal. The solids (hydrochar and untreated algae) were pelletized using a laboratory hand press pelletizer at 120 oC and 20 MPa pressure and characterized for energy densification and pellet properties. TGA studies showed that combustion of the all types of algae samples occurred in three stages. Pelletization provided higher energy densification for hydrochar obtained from the LEAR feedstocks. Pellets from hydrochar materials were found to be hydrophobic and stronger than pellets from the raw feedstocks. This presentation also details the combustion kinetics of different algal samples obtained in the study.