Systems and methods for digestion of solid waste

• US 9,328,323 B2
• Filed: 06/28/2013
• Issued: 05/03/2016
• Est. Priority Date: 07/08/2011
• Status: Active Grant

• Current Assignee: Aikan North America, Inc.
• Original Assignee: Aikan North America, Inc.
• Inventors: Christensen, Christian Boggild Smed
• Primary Examiner(s): HOBBS, MICHAEL L
• Application Number:
  US13/931,405
• Publication Number:
  US 20130295658A1
• Time in Patent Office: 1,040 Days
• US Class Current: 1/1
• CPC Class Codes: C05F 17/40 Treatment of liquids or slurries
• CPC Class Codes: C05F 17/50 Treatments combining two or more different biological or biochemical treatments, e.g. anaerobic and aerobic treatment or vermicomposting and aerobic treatment
• CPC Class Codes: C05F 17/964 Constructional parts, e.g. floors, covers or doors
• CPC Class Codes: C05F 17/986 the other material being liquid
• CPC Class Codes: C05F 17/989 Flow sheets for biological or biochemical treatment
• CPC Class Codes: C12M 21/04 for producing gas, e.g. biogas digesters for manure with production of biogas A01C3/028, biological treatment of water, waste water or sewage C02F3/00, C02F11/02, preparation of natural gas or syngas C10L3/06, C10L3/10
• CPC Class Codes: C12M 29/02 Percolation
• CPC Class Codes: C12P 5/023 Methane
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02P 20/145 the feedstock being materials of biological origin
• CPC Class Codes: Y02W 30/40 Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse

Abstract

This invention relates generally to systems and methods for digestion of solid waste that simplify solids handling. In certain embodiments, anaerobic methane extraction takes place for a period of time (e.g., from 1 to 4 weeks), after which an aerobic composting process begins in the same chamber. The organic waste remains in place and oxygen (e.g., in air) is forced into the chamber for an additional period of time (e.g., from 2 to 4 weeks). At the conclusion of the aerobic phase, the process yields a rough compost product that is stable and pathogen free. The rough compost can be further processed and blended to create high value engineered soils.

Claims

1. An apparatus for decomposition of organic matter into biogas and compost, the system comprising:

a waste processing tank into which solid organic waste is loaded and in which hydrolysis and composting takes place at separate times, with composting of the solid organic waste taking place during a separate stage after hydrolysis is completed, wherein the waste processing tank comprises a drain at or near its base, the drain allowing flow of the percolation liquid out of the waste processing tank during the hydrolysis stage, the drain also serving as a vent through which air flows into and/or out of the solid organic waste in the waste processing tank during the composting stage;

a controller programmed to automate addition of percolation liquid in the waste processing tank and initiate switchover from hydrolysis to composting according to pH in the waste processing tank;

a spraying system configured to spray percolate liquid onto the solid organic waste in the waste processing tank during the hydrolysis stage, wherein the percolate liquid comprises fatty acids leached from the solid organic waste and wherein the percolate liquid is recycled from the base of the waste processing tank during the hydrolysis stage; and

a biogas reactor tank into which the percolate liquid from the waste processing tank is pumped for generation of biogas under anaerobic conditions during a gasification stage.

2. The apparatus of claim 1, wherein the waste processing tank is configured to operate at ambient pressure during the hydrolysis stage, the composting stage, or both.

3. The apparatus of claim 1, wherein the waste processing tank is configured to operate under anaerobic conditions during the hydrolysis stage.

4. The apparatus of claim 1, further comprising a biofilter through which air from the waste processing tank passes prior to discharge to the atmosphere during the composting stage.

5. The apparatus of claim 1, further comprising a filter configured to separate solids from the percolate liquid.

6. The apparatus of claim 1, comprising at least two waste processing tanks connected in parallel.

7. The apparatus of claim 1, wherein the waste processing tank comprises an acid-resistant lining or coating.

8. The apparatus of claim 1, wherein the biogas reactor tank is gastight.

9. The apparatus of claim 1, further comprising a heater for heating the percolate liquid either in the biogas reactor tank or outside the biogas reactor tank.

10. The apparatus of claim 1, wherein the biogas reactor tank comprises a sump to separate sediment and/or particles from the percolate liquid.

11. The apparatus of claim 1, further comprising a liquid process tank into which percolate liquid from either the biogas reactor tank, the waste processing tank, or both flows prior to being pumped to the spraying system for spraying onto the solid organic waste in the waste processing tank during the hydrolysis stage.

12. The apparatus of claim 11, wherein percolate liquid from both the biogas reactor tank and the waste processing tank flows into the liquid process tank prior to being pumped to the spraying system for spraying onto the solid organic waste in the waste processing tank during the hydrolysis stage.

13. The apparatus of claim 12, further comprising a filter tank configured to separate solids from the percolate liquid before the percolate liquid enters the liquid process tank.

14. The apparatus of claim 11, comprising one liquid process tank for every waste processing tank.

15. The apparatus of claim 14, comprising at least five waste processing tanks for each of one or more biogas reactor tanks.