Researchers at Brigham Young University (BYU) in Utah, US, are sourcing biomass suitable for power plants from trees killed by wildfires.
Wildfires are becoming more frequent in the Western US, due to factors such as bark beetles, which burrow and reproduce under the bark of trees and eventually cause the tree to decay and die, if infested. According to BYU chemical engineering professor Andrew Fry, there are some forests where over 70% of the trees are dead and standing. These become the perfect fuel for wildfires and increase the probability and severity of fires.
Fry and other BYU researchers have developed new ways to transform these trees into useful fuel for coal power plants, helping to reduce carbon emissions. Nonetheless, there are challenges to face in the transition from using coal-based fuel to one using dead and decaying trees, according to BYU researchers. Biomass fuel can cause blockages in coal power plants and the minerals released from burning the wood can also coat mechanisms with ash, which can be dangerous.
“Ash is a bad thing in a combustor because it coats surfaces of heat transfer and places where heat needs to escape,” said Fry. “It reduces the efficiency of the whole power plant and can eventually shut you down if you don’t handle it right.”
Fry and his team demonstrated a biomass fuel safe for power plants to use with confidence at the Hunter Power Plant in Emery County, Utah. They burned 900 tons of biomass mixed with coal for 24 hours “with great success”. The demonstration revealed there were no meaningful changes in ash deposition from coal in comparison to co-fired coal and biomass material.
The team worked to develop a new type of fuel that was compatible and avoided making changes to the existing hardware necessary.
Fry used two approaches to break down the trees’ lignin structure. One was torrefaction, which shreds the trees down to very small particles and then heats them. The second, called steam explosion, was used to pressurise the shredded wood material with steam, then release the pressure rapidly. After the structure is broken, the processed biomass can be pressed into pellets and treated like coal.
Fry and his team tested the safety by using a combustor and other smaller-scale equipment that mimicked a power plant to test their prepared materials and new fuel, to ensure it would not cause issues when transitioned to real plants.
The BYU researchers plan to continue working with several power plants in hopes of making the use of biomass fuel a viable long-term option for coal-fired power plants.
