A process for burning coal or other carbonaceous fuels captures sulfur and other undesirable compounds are captured and retained in non-reactive ceramic-like form after the combustion phase. The process involves addition of multiple element alkali powders and/or sorbents preferably containing oxidizing anions such as nitrates and nitrites, preferably based on calcium. In various embodiments, the remediation materials when applied in a complex powder and/or liquid containing multiple elements, result in higher sulfur capture than the materials would otherwise achieve on an individual basis. In a preferred embodiment, the sorbents contain elements that minimize or lower the melting point of the ash. This leads to lowered cohesiveness and toughness of the ash so that less ash builds up on the boiler and better heat transfer is obtained.