Process for producing useful concentrated slurries from waste material

A process for the production of a concentrated slurry containing fibers suitable for use in the production of a self-binding product selected from the group consisting of paper, board and fuel, with the contemporaneous consumption of domestic refuse containing both organic and inorganic materials and of a sewage sludge, which process comprises:

• diluting the domestic refuse with water and breaking up the refuse;
• separating off from the diluted, broken-up refuse, the larger pieces of refuse containing the majority by weight of the inorganic material originally present in the refuse;
• passing the diluted, broken-up refuse from which the larger pieces have been separated and which contains the majority by weight of the organic material originally present in the refuse, to a digestor containing microorganisms capable of assimilating the organic material present and maintaining said digestor at a temperature effective for producing a hydrocarbon combustible gas selected from the group consisting of methane, propane, and butane;
• passing to the digestor a sewage sludge;
• allowing the microorganisms to feed on the sewage sludge and on said diluted, broken-up refuse from which the larger pieces have been separated and to produce said hydrocarbon combustible gas, the contents of the digestor being agitated to produce a uniform dilute slurry;
• burning part of the resulting combustible gas to provide heat required to maintain the contents of the digestor at the required operating temperature;
• withdrawing a dilute slurry from the digestor, said slurry containing long fibers of a length sufficient to produce a selfbinding product and fibers shorter than said long fibers;
• dewatering the dilute slurry withdrawn from the digestor in a manner such that the majority of long fibers are retained in the resulting first concentrated slurry with the long fibers entwined with each other, there also being produced a more dilute slurry;
• withdrawing the first concentrated slurry from the dewatering stage and drying said long fibers to produce said self-binding product;
• concentrating the said more dilute slurry to obtain a second concentrated slurry containing said shorter fibers and other non-fibrous solid material, and to obtain a weak aqueous slurry;
• withdrawing the second concentrated slurry which is suitable for use in or as a nutrient-bearing solid conditioner or animal feedstuff;
• and
• recycling said weak aqueous slurry to the digestor.