referring first to fig1 , a method of reducing nitrogen oxides 100 , includes the steps of producing an air stream having a nitrogen oxide by burning a raw material mixture in a kiln 110 , introducing a waste material containing cyanide into the air stream 120 in a manner that causes the cyanide to react with nitrogen oxides in the air stream at a temperature between 1200 ° f . and 1640 ° f . 130 , and using mineral residue from the waste material in a cement manufacturing process 140 . nitrogen oxide ( nox ) is a term that encompasses at least one of the following compounds : nitrous oxide ( n 2 o ), nitric oxide ( no ), dinitrogen dioxide ( n 2 o 2 ), dinitrogen trioxide ( n 2 o 3 ), nitrogen dioxide ( no 2 ), dinitrogen tetroxide ( n 2 o 4 ); and dinitrogen pentoxide ( n 2 o 5 ). an air stream having a nitrogen oxide is preferably a gas that has 200 - 1000 ppm of nox , however , the concentration of nox should not be interpreted herein as a limitation since reduction of nox would occur with substantially higher or lower concentrations . an air stream having a nitrogen oxide may be a flue gas resulting from a combustion process such as that which occurs during the burning of materials ( e . g . limestone , silica , iron ore , and aluminum oxide ) in a cement kiln . generally , the combustion referred to here in is the combustion of a fuel , for example , coal , methane gas , oil , waste materials , and so on . in a typical cement manufacturing process the nox laden gas is rises upward through a preheater tower and out an exhaust stack . as the nox laden gas rises , a waste material containing cyanide is introduced into the air stream 120 . cyanide is defined herein as any of various salts or esters of hydrogen cyanide containing a cn group , including potassium cyanide and sodium cyanide . such cyanide containing waste may optionally be derived from mining operations that utilize a heap leach process . in a heap leach process , cyanide is percolated through the mined material , and as a result a waste material high in mineral content ( e . g . iron , aluminum , and silica ) is produced . the waste material , however , contains hydrogen cyanide which is itself a highly toxic compound . by using such waste a dual benefit may be achieved in that nox concentration is reduced and desired mineral content is added . cyanide containing waste is also a bi - product of an aluminum related process in which a “ pot ” comprising a steel shell lined with insulation material and a layer of carbon is used wherein the layer of carbon acts as the cathode for an electrolysis process . this process is discussed in detail in a co - pending application filed by the same inventor titled use of spent potliners in cement production , and incorporated herein by reference in its entirety . it should be noted that under conditions in which moisture is present , ammonia ( nh 3 ) may be produced from the spent potliner waste . such ammonia may be used to additionally or alternatively aid in the reduction of nox . of course , cyanide - containing waste may be derived from other processes including an electroplating operation , and a chemical formulating operation . it is preferred that the waste material be in a non - aqueous form , and introduction of a waste material containing cyanide 120 may occur with the aid of a blower that disperses the waste material into the air stream . regardless of the mode for introducing the waste , sufficient mixing or intimate contact of the waste with the air stream is anticipated , and reacting of the cyanide with the nitrogen oxides 130 in a selective non - catalytic reduction ( sncr ) may occur . it should be appreciated that while a sncr process is preferred , it is contemplated that a selective catalytic reduction ( scr ) process may also produced desired results . in a preferred class of embodiments , reaction of the cyanide ( i . e . the reagent ) and the nox occurs at a temperature between 1200 ° f . and 1640 ° f . at this preferred temperature range , the reduction of nox has been shown to exceed that caused by ammonia . the temperature range within which reduction of nox occurs should be interpreted broadly and as such reasonable variations in the temperature range may still yield a favorable result . in fig2 , an exemplary cement manufacturing system 200 comprises a preheating and / or precalcining tower 210 , a waste intake 220 , a rising duct 230 , a rotary kiln 240 , and a clinker cooler 250 . the relevant portion of the system begins with burning of raw materials in the kiln 240 where the temperature can reach 2700 ° f . or higher . burning of the raw materials is accompanied by fuel combustion which generally produces nox in the air stream in the kiln . the air stream generally follows a path from the kiln , up through the riser duct into the pre - heater tower 210 and then out an exhaust stack . at a suitable point in the path , a cyanide containing waste is introduced into the air stream through waste intake 220 . a point in the path is suitable if the cyanide containing waste sufficiently mixes with a nox laden air stream to cause reduction of the nox . while introduction of the waste is depicted to occur directly into the pre - heater tower 210 , it is contemplated that the waste intake 220 may be located at a point before the preheater tower 210 ( i . e . the riser duct 230 or even the kiln 240 ) depending upon the temperature . it is contemplated that factors , other than the temperature at which the waste is introduced , may affect the efficiency of nox reduction . among these factors are the concentration of oxygen in the air stream , retention time at appropriate temperatures , and intimacy of contact between the nox reducing factors and nox compounds . thus , specific embodiments and applications of introduction of cyanide waste as a nox reductant have been disclosed . it should be apparent , however , to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein . the inventive subject matter , therefore , is not to be restricted except in the spirit of the appended claims . moreover , in interpreting both the specification and the claims , all terms should be interpreted in the broadest possible manner consistent with the context . in particular , the terms “ comprises ” and “ comprising ” should be interpreted as referring to elements , components , or steps in a non - exclusive manner , indicating that the referenced elements , components , or steps may be present , or utilized , or combined with other elements , components , or steps that are not expressly referenced .