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Pyrolysis is a low-emission and sustainable thermochemical technique used in the production of biofuels, which can be used as an alternative to fossil fuels. Understanding the kinetic characterization of biomass pyrolysis is essential for process upscaling and optimization. There is no accepted model that can predict pyrolysis kinetics over a wide range of pyrolysis conditions and biomass types. This study investigates whether or not the classical lumped kinetic model with a three-competitive reaction scheme can accurately predict the walnut shell pyrolysis product yields. The experimental data were obtained from walnut shell pyrolysis experiments at different temperatures (300–600 °C) using a fixed-bed reactor. The chosen reaction scheme was in good agreement with our experimental data for low temperatures, where the primary degradation of biomass occurred (300 and 400 °C). However, at higher temperatures, there was less agreement with the model, indicating that some other reactions may occur at such temperatures. Hence, further studies are needed to investigate the use of detailed reaction schemes to accurately predict the char, tar, and gas yields for all types of biomass pyrolysis.

The amount of PCDD/F emissions produced by gasification operations is often within standard limits set by national and international laws (<0.1 ng TEQ/Nm3). However, a recent assessment of the literature indicates that gasification cannot always reduce PCDD/Fs emissions to acceptable levels, and thus a common belief on the replacement of incineration with gasification in order to reduce PCDD/Fs emissions seems overly simplistic. A review that summarizes the evidence on when gasification would likely result in environmentally benign emissions with PCDD/F below legal limits, and when not, would be of scientific and practical interest. Moreover, there are no reviews on dioxin formation in gasification. This review discusses the available data on the levels of dioxins formed by gasifying different waste streams, such as municipal solid wastes, plastics, wood waste, animal manure, and sewage sludge, from the existing experimental work. The PCDD/Fs formation in gasification and the operational parameters that can be controlled during the process to minimize PCDD/Fs formation are reviewed.

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.