Ash deposition is a process limiting phenomenon for many boilers. The rates of deposition formation vary significantly with fuel characteristics, boiler design, and boiler operation. The following table quantitative compares the rates of deposit formation for two coals with that of four biomass fuels. As is indicated, the rates for the biomass fuels can be the same or over an order of magnitude higher or lower than those for coal. These are very large deviations. Not indicated is that the rates can vary by nearly the same amount for a given fuel, depending on how, when and where the fuel was collected and the conditions under which it was produced.