A solid composition comprising copper (Cu), zinc (Zn), molybdenum (Mo), tungsten (W), vanadium (V), tin (Sn) and silver (Ag), which improves performance of combustion engines by decreasing fuel consumption and levels of emission, particularly soot (particulate matter, or PM), carbon monoxide (CO), carbon dioxide (CO.sub.2) and nitrogen oxides (NOx), in an economically efficient way.

A solid biomass fuel derived from one or more sources of biomass, wherein the one or more sources of biomass comprise: straw, palm-derived material, nut shells, hemp, bamboo, corn cob, rice husk, fruit shells, crop residues, seaweed, calliandra calothyrsus, acacia mangium, albizia chinensis, hevea brasiliensis, grass, or any combination thereof: wherein the solid biomass fuel further comprises one or more aluminosilicate-containing clays, one or more aluminosilicates, one or more pulverised fuel ashes, or a combination thereof.

Proposed is a pretreatment desulfurization system including: a first chute for supplying a pretreatment apparatus with coal transported by a belt conveyor; a pretreatment apparatus for immersing the supplied coal in a catalyst mixture obtained by mixing a desulfurization catalyst and water, thereby desulfurizing the coal; a mesh conveyor for separating the coal being immersed in the catalyst mixture and having passed through the pretreatment apparatus, into a liquid phase and a catalyst-treated coal; a mesh conveyor for transporting the catalyst-treated coal; and a storage tank for storing the transported catalyst-treated coal.

A method of reducing deposits in a diesel engine, the method comprising combusting in the engine a diesel fuel composition comprising a detergent additive which is not a quaternary ammonium salt or a Mannich reaction product; and a quaternary ammonium salt additive comprising the reaction product of nitrogen containing species having at least one tertiary amine group and a quaternizing agent; wherein the nitrogen containing species is selected from: (i) the reaction product of a hydrocarbyl-substituted acylating agent and a compound comprising at least one tertiary amine group and a primary amine, secondary amine or alcohol group; (ii) a Mannich reaction product comprising a tertiary amine group; and (v) a polyalkylene substituted amine having at least one tertiary amine group.