NOVELTY - Converting (M1) ash into cementitious slag with properties similar to ground granulated blast furnace slag involves: co-firing fly ash-carbon mixtures, or de-volatilized coal char, or anthracite coal culm in an air-cooled, slagging combustor with limestone or similar slag fluxing materials to convert ash into cementitious slag with properties similar to ground granulated blast furnace slag.    USE - For converting ash from municipal wastes i.e. anthracite culm or coal mine waste into cementitious slag particularly for producing hydraulic cementitious slag used for constructing sea walls to protect shorelines from rising seas, storms, and contamination from oil spills in oceans; for co-production of the cementitious slag and electricity (all claimed).    ADVANTAGE - The method enables retrofitting new power plants or existing coal power plants i.e. fossil fuel fired power plants to perform the above process utilizing a revenue stream generated from co-benefits due to sale of the cementitious slag, electricity and the sale of carbon dioxide sequestration credits offset the power plant's capital and operating costs. The method operates fossil fuel fired power plants with near total emission controls and near total carbon dioxide sequestration and co-benefits, with annual electric power capacity factors of greater than or equal to 70%, and sells electricity without any government subsidies at prices below government subsidized renewable electricity including at least one of wind and solar power combined with the power plants to achieve greater than or equal to 70% annual capacity factor. The method nearly cuts in half a heat rate achievable in mass burn municipal incinerators. The refuse derived fuel is gasified indirectly to hydrogen or methane with remaining char co-fired in the air-cooled slagging combustor, thus the produced hydrogen or methane is used as a primary or major auxiliary fuel in municipal mass burning incinerators in place of bulk waste combustion to almost double an incinerator's capacity factor. The method operates coal power plants and produces sufficient revenue to offset costs associated with achieving near zero emissions to air, land and water from coal fired combustion. The method extends an operating life of existing coal fired power plants; increases domestic manufacturing and associated jobs by retrofitting existing or new coal fired boilers with the air-cooled slagging combustors and operating the air-cooled slagging combustors at near 100% capacity factors to reduce electricity costs below all government subsidized power; reduces operating cost of electric furnaces for metals production by using coal fired electric power and co-produces the cementitious slag, and sequesters carbon dioxide, and installs metals or metal ore manufacturing facilities at or near metal ore or coal mines or carbon dioxide sequestration locations; reduces the municipal waste disposal costs and increases waste furnace thermal efficiency and reduces environmental impact of the waste by physically separating non-combustible waste and shipping it to a landfill or using it, and converts all combustible matter to refuse derived fuel and co-firing it with 80% coal or coal waste in an air-cooled slagging combustor, where disposal of organic content in municipal waste has a minimal increase on carbon dioxide equivalent emissions compared to landfill disposal because methane emitted from the landfill has a two dozen times more carbon dioxide equivalent emissions than an equal weight of carbon dioxide, thus produces hydrogen from coal volatile matter which is used for reduction of metal oxides to metals, including iron and aluminum and all other metals suitable for hydrogen reduction, at least at one of coal mine sites and above suitable carbon dioxide sequestration geologic formations, including those of limestone. The method revenues obtained from power plants erected according to near Butte, Mont are used to rehabilitate a copper mine pit in it, or abandoned mines by removing and cleaning its accumulated water, recovering any residual copper or other ore, and filling the pit with fresh earth. The method neutralizes acidified rivers, streams, lakes and water wells that were a result of previous mining of coal or gas or oil with the excess limestone that remains after being used for fluxing coal ash in slagging combustors, removing SO2, removing coal ash trace metals, removing chemicals from combustion products, and prepares emulsions for CO2 sequestration.