Greener coal for the future
Biochar has been presented as a substitute for regular coal. But biochar is far from being economically viable yet. Lorenzo Riva wrote his PhD thesis on how biochar can actually become an economically viable and useful substitute.
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“We often think of coal as a means to produce electricity, but it has so many more uses. My research is on coal used to extract metal which is used in mobile phones, computers and a lot more. The journey from raw material to finished product is a long process and big industry”, says Riva who defended his PhD thesis in September.
The industry depends on coal to extract raw material such as silicon, which is used in electronics and for making solar cells. Coal is considered the most polluting fuel in use today, and it is not renewable.
From mining to forests and plants
Biochar, which is climate neutral, has become an alternative. It is produced from forest residues and plant waste which is mixed into a biomass. The mass is heated to 350° C without the presence of oxygen. This process is called pyrolysis. The carbon in the biomass is converted to biochar, pyrolysis oil and various gases. The biochar can then be used to extract the same materials as regular coal, without having to resort to mining.
“But biochar is not as strong as regular coal, and that is a problem. Biochar is like chips and falls apart very easily. A truckload of biochar will lose up to 20% in transport, so on a large scale it does not make economic sense”, says Riva.
The coal industry is highly competitive, and biochar will either have to be cheaper or much better than regular coal to compete.
You can read Lorenzo Riva’s doctoral thesis here
Emissions cut by a third
“I converted biochar into biochar pellets, which are much denser. I did this by taking the pyrolysis oil that comes from biochar production, combining it with biochar and heating this up to 600 degrees. The pyrolysis oil becomes the binder, instead of being thrown away, as the usual practice is. The biochar pellets are much denser, and losses during transportation are reduced from 15-20% to 0.5% when compared to biochar”, says Riva.
For him, an overarching goal has been to make the whole process sustainable and environmentally friendly. Two considerations had to be taken into account. The production of biochar pellets is more polluting than the production of ordinary coal. However, the use of the product is more environment-friendly since biochar is considered climate neutral once it has been produced. In total, there is a 31% reduction in pollutant emissions in the use of biochar compared to the use of coal.
“Interest in the use of biochar for metal production is growing, but much depends on political decisions. Reducing CO2 emissions is becoming an increasing priority, and the use of biochar instead of regular coal is a promising area for future research”, says Lorenzo Riva.