Patent ID: 6368849
Filing Date: 2002-04-09
Classification: C02F,C05F,Y02A,Y02E,Y02P,Y02W

Abstract:
A method for the treatment of an organic waste material in liquid form, comprising:(i) subjecting the liquid to anaerobic fermentation in a biogas reactor, (ii) separating a substantially sterile and particle-free permeate stream from the biogas reactor by means of a tubular ultrafiltration membrane having a mean molecular weight cut-off of up to about 100,000 Dalton, wherein the separation is performed at a pressure of about 4-6 bar, resulting in a methane-enriched fraction comprising bacteria and suspended organic matter retained by the tubular ultrafiltration membrane, (iii) returning said methane-enriched fraction to the biogas reactor to result in a biogas having a methane content of at least about 70% by weight, (iv) subjecting the substantially sterile and particle-free permeate stream to treatment with an ammonia stripper to result in an ammonia fraction and a nutrient salt fraction, and (v) separating the nutrient salt fraction into a fertilizer concentrate fraction and a water fraction, wherein treatment of the permeate stream with the ammonia stripper is performed at an elevated temperature.