Jhon F. Vélez et al. at the Universidad Nacional de Colombia in Medellín, Colombia have reported on experimental work on the co-gasification of Colombian biomass and coal blends in a fluidized bed working at atmospheric pressure. Several samples of blends were prepared by mixing 6–15 wt% biomass (sawdust, rice or coffee husk) with coal.

Experimental assays were carried out using mixtures of different steams/blends and air/blend ratios, to show the feasibility of implementing co-gasification as an alternative to the production of fuel gas for heating and the generation of electricity. The process offers the possibility of clean and efficient conversion of the refuse coal to a low-heating-value gas.

Although the presence of biomass reduces the energy efficiency of the process, this reduction is minor and should not overcome the benefit of reduced CO₂ emissions obtained through the use of biomass as a renewable source.

The produced fuel gas was found to be rich in hydrogen (up to 15%). Other combustible gases present in the syngas are carbon monoxide (~11%), methane (CH₄) and hydrocarbons (tars). A higher proportion of biomass in the fuel increased the content of hydrogen in the sample, but decreased the energy efficiency of the process. The experiments also showed ash agglomeration and tar deposition as minor drawbacks of the gasification process.

Fuel, Volume 88, Issue 3, March 2009, Pages 424–430.
DOI: 10.1016/j.fuel.2008.10.018