# Biomass-Based Chemical Looping Gasification: Overview and Recent Developments
## 5 Progress in Biomass Chemical Looping Gasification
### Pilot-Scale Investigations
It was evaluated the capacity of transport oxygen and heat from the air reactor to the fuel reactor to promote gasification, and catalytic function for fuel gasification and syngas reforming. Four series of experiments took place in a Bench-scale fluidized bed at 950 \({}^{\circ}\)C and atmospheric pressure to examine the performance of the process and oxygen carrier. Those experiments demonstrated that the oxygen carrier was able to promote endothermic gasification due to its stable transport capacity of oxygen and heat during multiple redox cycles. Furthermore, its reduced forms could strongly catalyze internal syngas reforming. Red mud oxygen carrier has a high melting point and proper heat capacity; thus, it can be operated at a high temperature in the FR. [PERSON] et al. [75] combined Fe\({}_{2}\)O\({}_{3}\) and CuO to produce a novel oxygen carrier for biomass gasification. It was found that the bimetallic oxides showed advantages over two mono-metallic oxygen carriers in the investigation. A ratio of 50 wt.% of Fe\({}_{2}\)O\({}_{3}\) and 10 wt.% CuO was selected as an optimal ratio in the study. Furthermore, the best per formance was observed at the O/C ratio of 0.75 and 900 \({}^{\circ}\)C. However, the combined oxygen carrier performed the worst reactivity after three cycles. It was mainly attributed to sintering caused by Cu atomic that resulted in the reactivity decline. During steam gasification of biomass, undesirable CO2 and tar would be produced, which will reduce the quality of the hydrogen stream and process efficiency. The adding of calcium oxide (CaO) could be used to overcome such challenges. Calcium oxide could work as a tar reforming catalyst and CO2 sorbent, and thereby increase hydrogen-rich gas production. However, the deactivation of calcium oxide after the carbonation reaction is a challenge for continuous hydrogen production and economic issues [91]. A study was conducted to evaluate the effects of Fe/Ca ratio on hydrogen production from chemical looping gasification of rice straw [86]. Synthesized bimetallic Fe-Ca oxides were used as an oxygen carrier in the study. Its results found that there are two types of calcium ferrites (Ca2 Fe2O5 and CaFe2O4) formed with different ratios of Fe/Ca; and at the Fe:Ca ratio of 1:1, the highest hydrogen yield was obtained with 23.07 mmol/g biomass at 800 \({}^{\circ}\)C. Furthermore, the process temperature needed for the completed redox of Ca2 Fe2O5 was higher than 800 \({}^{\circ}\)C during chemical looping gasification with steam. [PERSON] et al. [85] investigated CLG of biomass using steam and CaO additive. It found that CaO showed a positive effect on gasification performance, and worked mainly as a CO2 adsorbent at low temperature but as a catalyst above 700 \({}^{\circ}\)C. It was also found to retard the sintering and porosity reduction of Fe2O3. A novel process was proposed to combine BCLG and CO2 splitting using Ca2 Fe2O5 aerogel as an oxygen carrier [90]. In the process, pine wood was decomposed with the presence of an oxygen carrier in the FR to produce syngas, phenolic-rich bio-oil, and biochar. The reduced oxygen carrier was re-oxidized in the AR by CO2 instead of air to generate CO. The results showed that Ca2 Fe2O5 aerogel is a promising oxygen carrier due to its redox activity, phase reversibility and cyclic stability. The study also investigated the mechanism of the synergistic enhancement of chemical looping-based CO2 splitting using biomass cascade. It was found that the products from biomass fast pyrolysis and oxygen carrier reduction can further benefit oxygen carrier reduction and biomass conversion, respectively, as well as enhance CO2 reduction in the AR. Continuous operations in a 1.5 kWth pilot were conducted for syngas production using pine wood as fuel and ilmenite [32], Fe2O3/Al2O3 [33] as oxygen carriers. A new method was proposed [32] for controlling the lattice oxygen used in the fuel reactor for syngas production by controlling the oxygen fed into the air reactor.