Bacteria minimizes effects of coal contaminants
UN/DICYT Through a novel formula a group of researchers are working to boost the capability of certain microorganisms to naturally extract contaminants such as sulphur-associated coal. Although coal is the most abundant fossil fuel in the world, it is also a polluting source after its combustion as it produces adverse environmental factors due to emission of sulphur gases into the environment, especially in large-scale industrial processes.
Therefore the idea behind the project is to take advantage of the decontamination achieved naturally by certain bacteria and attack the issue, said Mining Faculty’s Applied Mineralogy and Bioprocesses Group (GMAB, for its Spanish acronym) Director Marco Antonio Márquez.
“Bacteria are submitted to an adaptation process with coal at a laboratory level until the microorganism eliminates the pollutant considerably. From there results are assessed with chemical additives to discover an optimum level between both forms,” said Márquez.
Microorganisms degrade the mineral and act as drivers of oxidation and pyrite leaching (substance extraction) processes. Pyrite is the main material of sulphur.
The alternative is viable for Colombia as coal unlike other minerals, is a low-cost raw material easily found in areas with coal mines such as the Provinces of Cauca, Valle del Cauca, Antioquia, Guajira and Córdoba, with potential for industrial combustion processes.
However in some cases there are high sulphur concentrations, therefore biodesulfurization is an important decontamination process.
High quality process
Although coal biodesulfurization has been in use for approximately 20 years, it has only been used at a pilot level. Therefore the idea behind the UNal project is achieve worthy sulphur removal levels.
In this sense researchers approached cement producer ARGOS with the purpose of developing the technique at medium term and determine its effectiveness in order to take it to an industrial level.
The project hopes to regulate the combustion contaminating process which results from manufacturing clinker, a regent mixed with gypsum to product cement.
Argos Innovation Vice-president Camilo Restrepo said that in the coal combustion process to manufacture clinker and cement there are products such as sulphur which need to be controlled in gaseous emissions using technology which may be implemented as pre-treatments. Removing sulphur can bring enormous environmental benefits as the firm uses approximately 100 kgs of coal for every ton of clinker to produce cement, after a series of thermal and chemical processes.
With these processes experts have achieved removal of up to 90% of sulphur, although they are still searching for more efficient bacteria culture media to improve large scale processes and continue with the project. According to Restrepo the results are promising and both parties have benefitted from the learning process produced by the research project.
Paola Duarte, another UNal researcher highlights that the 4,000 liter pilot plan and designed by the researchers has decontaminated 800 kgs of coal in periods of eight days, although they continue to research in order to achieve the same result in two days for the process to be accessible for the industry.
According to the researchers the greatest advantage is that these microorganisms may be found in the environment. Therefore they are extracted from the coal mines where decontamination processes are performed naturally or using Acidithiobacillus ferrooxidans cultures acquired commercially, said Gerardo Andrés Caicedo, GMAB researcher.