Scientists are developing a new biofuel that could become a renewable substitute for coal in the near future.
The biofuel briquettes store similar amounts of energy to coal, but can be burned without releasing pollutants and impurities into the air.
The 'instant coal' does not take thousands of years to form and can be manufactured quickly from agricultural waste, including wood and plants, meaning there would be a steady supply of raw materials if production of the new fuel was scaled up.
"If you think about how Mother Nature made fossil coal, it's time, pressure and heat," said Tim Hagen, part of the team who developed the fuel from the Natural Resources Research Institute (NRRI) at the University of Minnesota Duluth.
"We're doing those same processes, but instead of millions of years, we're doing it in a few hours. And because minerals don't get into the mix, we don't have those potential pollutants."
The coal substitute offers nearly as much stored energy as normal coal – 8,000 to 9,500 British Thermal Units (BTUs), as opposed to 12,500 BTUs.
The biofuel briquettes are produced using a process called torrefaction. The biomass from the waste raw materials is dried and heated to around 250°C in a low-oxygen atmosphere, before being compressed into a brick-like product.
"Maybe you like light roast coffee, it's not as concentrated... or you can take it further and have a dark roast coffee. We can do the same thing here," said Don Fosnacht, another of the NRRI researchers.
The NRRI is also developing an 'energy mud' that stores even more energy than the 'instant coal' and is produced in a giant pressure cooker.
While it will be some time before the 'instant coal' and the 'energy mud' are ready for commercial use, technologies like these have the potential to reduce emissions from coal as we transition to an low-carbon economy. They could also reduce the impact of mining, while also making use of natural waste.
The NRRI is now looking for investors to help them commercialise the products.