ORDORIFOUS REALITY

January 14, 2017


My company is working on a project involved with capturing methane from the decomposition of organic material in landfill sites.  Research preparatory to accepting the job reviled very interesting facts.  Let’s take a look.

NUMBERS:

The U.S. has 3,091 active landfills and over 10,000 old municipal landfills, according to the Environmental Protection Agency. However, in the “good old days,” every town (and many businesses and factories) had its own dump.  This is somewhat disturbing since these landfills were unregulated.  Upregulation without standards can create situations where effluent can creep into groundwater possibly polluting wells and other sources of potable water.  That has now changed for the better.  The two digital maps below will indicate location and concentration of approved landfill sites.  You certainly can notice the greatest concentration is from the Mississippi River east where population densities are greatest.  This is certainly to be expected.

landfill-map2

landfill-map

Municipal solid waste (MSW) – more commonly known as trash or garbage – consists of everyday items people use and then throw away, such as product packaging, grass clippings, furniture, clothing, bottles, food scraps and papers. In 2010, individuals in the United States generated about 250 million short tons (230 Mt) of trash.   In the United Stateslandfills are regulated by the Environmental Protection Agency (EPA) and the states’ environmental agencies. Municipal solid waste landfills (MSWLF) are required to be designed to protect the environment from contaminants that may be present in the solid waste stream

Some materials may be banned from disposal in municipal solid waste landfills including common household items such as paints, cleaners/chemicalsmotor oilbatteriespesticides, and electronics. These products, if mishandled, can be dangerous to health and the environment.  Safe management of solid waste through guidance, technical assistance, regulations, permitting, environmental monitoring, compliance evaluation and enforcement is the goal of the EPA and state environmental agencies.

A typical landfill site looks pretty much as follows:

landfill-storage

You are correct—a big, very big mess.

CODES AND REGULATIONS:

Title 40 of the Code of Federal Regulations (CFR) part 258 addresses seven major aspects of MSWLFs, which include the following:

  • Location restrictions—ensure that landfills are built in suitable geological areas away from faults, wetlands, flood plains or other restricted areas.
  • Composite liners requirements—include a flexible membrane (i.e., geo-membrane) overlaying two feet of compacted clay soil lining the bottom and sides of the landfill. They are used to protect groundwater and the underlying soil from leachate releases.
  • Leachate collection and removal systems—sit on top of the composite liner and removes leachate from the landfill for treatment and disposal.
  • Operating practices—include compacting and covering waste frequently with several inches of soil. These practices help reduce odor, control litter, insects, and rodent, and protect public health.
  • Groundwater monitoring requirements—requires testing groundwater wells to determine whether waste materials have escaped from the landfill.
  • Closure and post-closure care requirements—include covering landfills and providing long-term care of closed landfills.
  • Corrective action provisions—control and clean up landfill releases and achieves groundwater protection standards.
  • Financial assurance—provides funding for environmental protection during and after landfill closure (i.e., closure and post-closure care).

TIME LINE FOR METHANE PRODUCTION FROM LANDFILL:

Collection of methane does not occur the first day garbage is dumped into a landfill.  The chart below will indicate the constituents and a typical timeline for production CH (4).

time-line

We are after the methane so as you can see, after two years, approximately, we have roughly twenty percent (20%) of the effluent available for reclama.

Typical characteristics and quantities from decomposition of an established landfill are as follows:

typical-characteristics-and-quantities

HOW WE DO IT:

The JPEG below will indicate a very rough schematic of a landfill site with wells “sunk” to receive mechane and basic piping necessary for the accumulation of mechane.  Well systems consist of a series of vertical LFG extraction wells (perforated or slotted collection pipes) that penetrate to near the bottom of the refuse or to near the depth of saturated waste. Well systems are often recommended for landfills or portions of landfills that exceed 12 m (40 ft.) in depth. The design of a well-system requires an estimate of the rate of LFG production and the radius of influence of the wells. A well- system, either active or passive, is useful for layered landfills where vertical LFG migration is impeded. Because of the variability of landfill refuse, design procedures are difficult to apply to LFG collection systems. Vertical LFG collection wells are typically installed once filling operations have been completed, and are commonly spaced at a frequency of one per acre and are constructed using an auger type drill rig. As a general rule, where LFG collection efficiency is important, it is generally advisable to develop a tighter grid of extraction points with smaller spacings operated at a lower vacuum. It has been found that a vacuum of 10 to 25 inches of water column (in wc) represents a reasonable balance between maximizing zones of influence and minimizing air intrusion into the site. Operating at higher vacuum levels tends to extend the zone of capture beyond the limits of the waste burial and increase the potential for atmospheric air intrusion that could create a landfill fire/explosion hazard. The radius of the capture zone for a vertical extraction well may range from around 50 feet to 200 feet and is strongly dependent on localized landfill conditions. LFG recovery rates from an individual extraction well may range from approximately 10 to 50 cubic feet per minute (cfm).

A depiction of a typical well is shown as follows:

well

Each well must meet EPA standards and have the ability to capture all affluent so contamination of ground water does not occur.  Well extraction piping and well placement patterns may look as follows:

well-extraction-piping

A cross-section of a typical site indicates multiple wells with the landfill area.  The digital below will give you some idea as to schematic piping and flow.

methane-collection

As you can see, after accumulation, the affluent must be cleaned to remove methane.  Constituents possible within the “mix” are as follows:

organic-contaminants

Some of these contaminants are cancer-causing so they must be dealt with prior to collection.

You will notice in our example above; the collected and scrubbed methane is used to fire generators used to produce electricity.  This electricity may be sold back to the grid or used for industry and/or homes.

Examples of LFG Energy Projects:

Projects can vary significantly depending on the size of the landfill, the energy end-user, and other factors. Currently operational projects include:

  • Apex (50 million tons of waste) Las Vegas, NV – CC Landfill Energy LLC is building a plant that will produce 11 megawatts (MW) of electricity for NV Energy, a utility that serves approximately 2.4 million customers.
  • Puente Hills (123 M tons) Whittier, CA – The largest LFG-to-electricity program currently in production, Puente Hills produces 50 megawatts, enough to power roughly 50,000 homes. Additionally, some of Puente Hills’ gas is used to fuel garbage trucks.
  • Rumpke Sanitary (36 M tons) Colerain Township, OH – This landfill site hosts the largest landfill-to-gas facility in the world, recovering approximately 15 million standard cubic feet of LFG per day, which is then distributed by Duke Energy Corporation.
  • Newton County Landfill Partnership (19 M tons) Brook, IN – More than 1.1 million standard cubic feet of gas is captured from Newton County Landfill per day. The energy is used by a nearby factory to make egg cartons.
  • Atlantic Waste (15 M tons) Waverly, VA – This site has in place a 20-mile pipeline to Honeywell’s Hopewell plant. The landfill provides 20 percent of the energy used at the plant.

CONCLUSIONS:

Methane extraction is not only possible but is being accomplished across the United States.  The very short list above indicates those states and cities in which technology is being applied to provide usable energy from old-fashioned garbage.

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