Ash release and transformation behaviours are briefly summarized in this paper. Additives based on
different chemical compositions and possible counteracting effects can be used to abate ash related
problems during biomass combustion. Chemical binding is the most important effect of additives, and
converts problematic ash elements into high temperature stable substances. More studies are still needed
for further understanding interactions between additives and biomass ashes. There are still critical studies
that are necessary to further increase our understanding. Since utilization of additives is related to costs,
the amount of additives used for different scenarios are important. Normally, the input amount is based on
stoichiometric calculation. However, considering the loss of both additive mass and activity during a
combustion process, more detailed calculations are required in combination with real combustion
parameters. Furthermore, most of the studies reported in the literature are based on laboratory scale tests,
while more in-situ and industrial scale tests are preferred with full scale operation for a longer time. In
addition, new additives with multi-functions, high stability and reactivity and low cost should be
identified and tested. It would be most attractive to find more additives from wastes materials with low
costs and large amounts available.