Producing High-Strength Pellets From Seaweed, Sawdust, and Hay for Gasification

Hay, invasive lupine plants, wood chips, and seaweed are the four abundant biogenic fuel options in Iceland. These four biomass types are potential renewable fuel feedstock as they can be converted into syngas or high-value fuels using thermochemical processes such as pyrolysis and gasification. In this study, we focus on biomass pelletizing, which is a major process for preparing various kinds of feed for either gasification or controlled combustion as in powerplants and heat applications. Pelletizing is producing a low-humid, dense, and uniform shape of feedstock, which is appropriate for the continuous and efficient performance of the gasifier. The pellets need to be dense enough not to collapse in the hopper while being fed to the reactor. The challenge in this study is to produce high-quality pellets with high energy content, high strength, and optimized moisture level from abundant biomass types in Iceland that can be gasified efficiently and continuously in the gasifier. To address this challenge, we pelletized blends of hay, wood chips, and seaweed with different percentages. In this study, we focus on the strength of the pellets. The experiments suggest that up to a hay fraction of 20 wt.% a higher hay content results in a stronger pellet. Based on our experiments, pellets made only from wood are typically not strong enough for gasification. It was observed that after running several pelletizing experiments continuously, the temperature of the discharged pellets increased, and this parameter influenced the strength of the pellets.