Landfill design and method for improved landfill gas capture

• US 7,448,828 B2
• Filed: 02/23/2007
• Issued: 11/11/2008
• Est. Priority Date: 05/03/2001
• Status: Expired due to Fees

• Current Assignee: Institute For Environmental Management, Inc.
• Original Assignee: Institute For Environmental Management, Inc.
• Inventors: Augenstein, Don Churchill, Benemann, John Rudiger, Yazdani, Ramin
• Primary Examiner(s): KRECK, JANINE MUIR
• Application Number:
  US11/710,625
• Publication Number:
  US 20070243023A1
• Time in Patent Office: 627 Days
• Field of Search: 405/129.95, 405/129.9, 405/129.57
• US Class Current: 405/129.95
• CPC Class Codes: B09B 1/00 Dumping solid waste
• CPC Class Codes: B09B 1/004 Covering of dumping sites
• CPC Class Codes: B09B 1/006 Shafts or wells in waste dumps
• CPC Class Codes: Y02C 20/20 of methane
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02W 30/30 Landfill technologies aiming to mitigate methane emissions

Abstract

The invention provides an improved method of collecting biogas from a landfill that results in more complete collection of biogas produced in the landfill, and with less contamination with air. The method involves providing the landfill with an upper gas containment layer near the surface of the landfill to retard biogas escape and air entrainment into the landfill. Underneath the gas containment layer is provided a gas-permeable conductive layer. Underneath the conductive layer, a well withdraws biogas from the landfill. Withdrawal of biogas from the well creates a partial vacuum that draws gas from the gas-permeable conductive layer down through the waste mass to the well. If the rate of gas withdrawal from the well is too rapid, air will be entrained from the atmosphere into the gas-permeable conductive layer. But if the rate of gas withdrawal from the well is too slow, biogas may percolate through the gas-containment layer and the surface of the landfill to escape. Monitoring the gas composition of the gas-permeable layer allows one to determine quickly and continuously whether the rate of gas withdrawal from the well is too fast or too slow.

Claims

1. A method of collecting biogas from a landfill having waste and an outer surface contacting the atmosphere, wherein

the landfill contains (i) at or near the outer surface contacting the atmosphere a gas-containment layer that has low gas permeability;

and (ii) a gas-permeable layer toward the interior of the landfill from the gas-containment layer and toward the exterior of most of the landfill waste mass, the gas-permeable layer having at least 10-fold the gas-permeability of the gas-containment layer;

the method comprising;

(a) collecting biogas from the landfill from a location toward the interior of the landfill from the gas-permeable layer with at least one gas-collection well that collects biogas from an extraction location toward the interior of the landfill from the gas-permeable layer and separated by waste from the gas-permeable layer and draws it to the surface, the well comprising a biogas-collecting wellhead at the extraction location and a gas-impermeable conduit linking the wellhead to the surface to draw biogas from the wellhead to the surface;

wherein if any biogas is collected directly from the gas permeable layer, it is less than 10% of the volume of biogas collected from the landfill from the extraction location toward the interior of the landfill through the at least one gas-collection well.

2. The method of claim 1 wherein the outer surface contacting the atmosphere is an upper surface of the landfill, the gas-permeable layer is underneath the gas-containment layer and above most of the landfill waste mass;

and the biogas extraction location is underneath and separated by waste from the gas-permeable layer.

3. The method of claim 1 wherein if any biogas is collected directly from the gas permeable layer, it is less than 2% of the volume of biogas collected from the landfill from the extraction location located toward the interior of the landfill from the gas-permeable layer through the at least one gas-collection well.

4. The method of claim 1 wherein the area of the gas-permeable layer and the area of the gas-containment layer are each at least 50% of the landfill outer surface area contacting the atmosphere.

5. The method of claim 1 wherein the area of the gas-permeable layer and the area of the gas-containment layer are each at least 90% of the landfill outer surface area contacting the atmosphere.

6. The method of claim 1 wherein the gas-permeable layer has at least 1000-fold the gas permeability of the gas-containment layer.

7. The method of claim 1 wherein the gas-containment layer is predominantly soil.

8. The method of claim 1 wherein the gas-containment layer is predominantly clay.

9. The method of claim 1 wherein the gas-containment layer comprises a synthetic membrane.

10. The method of claim 1 wherein the gas-permeable layer comprises predominantly rigid or semi-rigid particles with an average particle diameter of 1 mm or greater, wherein gas-flow passages exist between the particles.

11. The method of claim 10 wherein the particles are gravel or pebbles.

12. The method of claim 10 wherein the particles are shredded tire, pieces of construction debris, paving debris, concrete chunks, wood debris, wood pallets, wood branches, wood logs, wood twigs, or wood chips.

13. The method of claim 1 wherein the gas-permeable layer comprises a network of apertured conduits oriented generally parallel to the surface contacting the atmosphere.

14. The method of claim 1 further comprising adding moisture or nutrients or both to the landfill mass to promote biogas formation in the landfill.

15. The method of claim 1 further comprising heating a portion or the whole of the landfill mass to promote biogas formation in the landfill.

16. A method of collecting biogas from a landfill wherein the landfill has an outer surface contacting the atmosphere, the method comprising:

providing the landfill at or near the outer surface contacting the atmosphere with a gas-containment layer that has low gas permeability;

providing the landfill with a gas-permeable layer toward the interior of the landfill from the gas-containment layer and toward the exterior of most of the landfill waste mass, the gas-permeable layer having at least 10-fold the gas-permeability of the gas-containment layer;

providing the landfill with at least one gas-collection well that collects biogas from an extraction location toward the interior of the landfill from the gas-permeable layer and separated by waste from the gas-permeable layer and draws it to the surface, the well comprising a biogas-collecting wellhead at the extraction location and a gas-impermeable conduit linking the wellhead to the surface to draw biogas from the wellhead to the surface; and

collecting biogas from the landfill toward the interior of the landfill from the gas-permeable layer through the at least one gas-collection well;

wherein if any biogas is collected directly from the gas permeable layer, it is less than 10% of the volume of biogas collected from the landfill from the extraction location toward the interior of the landfill through the at least one gas-collection well.