CaCO₃ and air/steam effect on the gasification and biohydrogen performance of corn cob as received: Application in the Colombian Caribbean region

Corncob is one of the most abundant agro-industrial wastes globally. It represents a bioenergy feedstock of 1500–5500 million tons per year. The shape and size of the corncob are suitable for gasification without pretreatment (size reduction, densification, or drying) in a downdraft gasifier. However, its volatile content (about 80% DAF) can generate high tar content, representing a challenge to adopt this technology. In the present work, an evaluation of the effect of air-steam mixture and calcium carbonate CaCO₃ as a promoter of both reforming and gasification reaction was carried out using corn cob without grains as raw material in a 40 kW gasifier. An analysis of variance of four experimental treatments was used to determine the main statistical and interactive effects on the syngas composition, hydrogen yield (yH₂), syngas lower heating value (LHV_gas), and cold gas efficiency (CGE). Results reveal the highest gasification performance achieved hydrogen production yields of 310 Nml/g, an LHV_gas value of 4.8 MJ/Nm³, and cold gas efficiency of 59.18% with steam and CaCO₃. Statistical analysis indicated that CaCO₃ and steam influence H₂ production by increasing 15.8% and 10.8%, respectively, with a CaCO₃/biomass ratio of 1% (w/w) and a Steam/biomass ratio of 11% (w/w). Main statistical effects were found for CGE increase of 5% with the addition of steam, 10% with CaCO₃, and synergy of 10% using CaCO₃ and steam simultaneously.