For such a dark, cold, slightly radioactive lump of fossil, coal has achieved a lot for humanity. We have only coal and a spark of ingenuity to thank for the explosive development in science, technology and engineering that we have seen in the past 300 years.
With so much chemical energy packed into such a dense form, it was the ideal power source for the steam engine, driving mass production, improving transport and contributing to overall quality of life over the industrial revolution. But no honeymoon lasts forever, and the initial charm of coal has been replaced by something rather unpleasant, irksome and insecure.
Nowadays, coal is near the bottom of the list of things you might imagine to be innovative or inspiring. It is the dirtiest and most hazardous of the fossil-fuels. It has lead to many respiratory and cardiovascular illnesses in heavily polluted urban areas and is contributing to smog, acid rain and toxic nitrogen and sulfur oxides in the atmosphere.
So it may come as a surprise that coal remains a subject of interest to researchers at the National Resources Research Institute of the University of Minnesota Duluth, who have successfully managed to reproduce a coal substitute with increased energy density and no heavy metal pollutants.
This solid biofuel has been shown to have an energy density up to 6.5 kWh per kilogram, compared to between 2.5 and 6 kWh per kilogram for the different varieties of coal, and can be produced from waste biological material such as invasive plants and agricultural waste, thereby benefiting the environment.
Seeing market potential in this fuel source, the NRRI have been avidly working to scale up production of the biofuel briquettes to commercially-relevant scales for use in energy production. This even led to a trial in a power plant in Portland, Oregon, where the entire supply of fossil coal was replaced with 3500 US tons of the man-made biofuel.
Not only did the they observe a power output increase of over 1.5 kWh per kilogram of fuel, but the process required minimal mechanical alterations, indicating the compatibility of the solid biofuel to coal-powered infrastructure.
Solid biofuel is made by a process mirroring the dry-roasting of coffee, where wooden chips are dried in a kiln, heated under a low oxygen atmosphere (to prevent combustion) and compressed into a solid. A second process can also be used for certain types of biomass feedstocks that resembles a pressure cooker.
The end product for this process is moist and a higher energy density then dry fuels. It is aptly named ‘energy mud’. NRRI Engineer Tim Hagen reflects on the parallels between their process and the natural process of the Earth – “If you think about how Mother Nature made fossil coal, it’s time, pressure and heat. We’re doing those same processes, but instead of millions of years, we’re doing it in a few hours.”
This development comes at a time when coal is experiencing a significant decline across the world in pursuit of renewable technologies and cleaner non-renewables. The USA has seen a 9% decrease in coal consumption in 2016 over the previous year due to increased efficiency of buildings and appliances, as well as an increased interest in natural gas, which may in itself be a problem due to the environmental concerns of fracking and drilling.
Less than 25% of the EU’s energy supply comes from coal, with this figure expected to drop due to its commitment to increase renewable energy installation in keeping with the Paris Agreement. China’s coal consumption has dropped 4.7% between 2015 and 2016 and it’s overall dependence has decreased from 64% to 62% over the same time period. These figures are significant, considering that China is the globe’s biggest consumer of coal, at 49% of world consumption in 2014.
Overall, coal has lost its metaphorical lustre and is not as economically incentivizing as it used to be. Perhaps solid biofuel can be used as a cost-effective and cleaner alternative to power our homes and business? It may work, it just all depends on whether the fuel will get a grip on the market.
Needless to say, our love affair with coal has come to an end. The embers have blown out and now we are just trying to get out as quickly and painlessly as possible.