Patent ID: 8105413

Claim:
A method of manufacturing a fertilizer comprising: mixing and heating an organic sludge with a force sufficient to produce a thixotropic paste in a first mixer; separately mixing acid with ammonia to produce an acidic mixture; acidifying the thixotropic paste with the acidic mixture to produce an acidic paste in the first mixer, wherein the acidified thixotropic paste is heated to a temperature exceeding 44° C. and has a pH of less than 5.5; blending the acidic paste and a heated inorganic fertilizer melt comprising an ammonium salt, while maintaining a temperature over 85° C. in a second mixer, wherein the ammonium salt is produced separate from the production of the fertilizer and the melt is maintained at a temperature over 177° C.; mixing a pH control agent and a hardening agent with the acidic paste to produce the fertilizer in a third mixer, wherein the fertilizer has a pH of between 5.0 and 7.0; and regulating the pressure within the mixers; removing water from the fertilizer.