European biogenic residues and wastes used for syngas production in a 20 kWth Chemical Looping Gasification unit

Reaching the targets set by the Paris Agreement demands sustainable alternatives to fossil fuels. Biomass gasification, where syngas is generated and afterwards converted into liquid biofuels, is one of the routes to produce low-carbon fuels. Chemical Looping Gasification (CLG) is a promising route in this context, since the oxygen is supplied to the fuel by a solid oxygen carrier, so that a syngas free of atmospheric N 2 can be obtained without an air separation unit, which simplifies its downstream conversion into biofuels and makes CO 2 capture more feasible. In this work, syngas was generated in a 20 kW th CLG unit from a range of European biomass residues representative of agricultural, forestry, and waste streams, including olive pits, buckwheat pellets, spruce treetops and branches, and waste wood type B, using ilmenite as the oxygen carrier. The process was assessed during about 85 h of steady-state operation. The variables explored were the oxygen-to-fuel ratio, λ, (0.2-0.5), temperature (850-970 °C), and the use of steam or CO 2 as gasifying agent. The oxygen-to-fuel ratio was identified as the most influential variable, with lower values clearly favoring syngas yield, while producing minor differences among the biogenic residues, which had a similar composition. Temperatures above 900 °C enhanced the gasification process, achieving biomass conversions exceeding 90 % for all fuels tested. Carbon emissions to the atmosphere were found to depend on temperature, size and biomass reactivity. The use of CO 2 as gasifying agent enabled the production of syngas with varying H 2 /CO molar ratios, which is of interest for its subsequent use in biofuel production.