Biomass is quickly becoming an important feedstock for energy generation in power plants. Due to their composition and nature, certain biomass fuels contribute to slagging, fouling, and corrosion. This invention provides a novel method of reducing or suppressing slag deposition and/or cleaning deposited slag in energy production processes in which potassium-containing solid fuels are combusted. Besides acting as a slag suppressant, further advantages of this invention are that the additive has no detrimental side-effects on capital equipment, increases slag friability, decreases slag fouling rate, reduces heat transfer corrosion as well as increasing the lifetime of the selective catalytic reduction catalyst.