Energy Discussion

by Mike Ewall - July 29, 1999, updated February 10, 2000

Printable Landfill Gas Factsheet (Updated Nov 2007)

“Landfill gas” is not the same thing as “natural gas” or “methane.” They are three separate terms which mean different things. They should not be used interchangeably. The term “landfill methane” is deceiving as it’s usually used to imply that landfill gas is simply methane.

Methane is a hydrocarbon gas (CH₄). It is a greenhouse gas and it is explosive. It is generated by decomposition (in landfills, from swamps, in the stomachs of cows, etc.).

Natural gas is approximately 80-99% methane, with the remainder being mostly other hydrocarbons (ethane, propane, butane, etc.) as well as some nitrogen, oxygen, water, CO₂, sulfur and various contaminants.¹

Landfill gas is about 40-60% methane, with the remainder being mostly carbon dioxide (CO2). Landfill gas also contains varying amounts of nitrogen, oxygen, water vapor, sulfur and a hundreds of other contaminants — most of which are known as “non-methane organic compounds” or NMOCs. Inorganic contaminants like mercury are also known to be present in landfill gas. Sometimes, even radioactive contaminants such as tritium (radioactive hydrogen) have been found in landfill gas.

NMOCs usually make up less than 1% of landfill gas. EPA identifies 94 NMOCs in their 1991 report, “Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed Standards and Guidelines.” Many of these are toxic chemicals like benzene, toluene, chloroform, vinyl chloride, carbon tetrachloride, and 1,1,1 trichloroethane. At least 41 of these are halogenated compounds. Many others are non-halogenated toxic chemicals. ^{2, 3} More exhaustive test for contaminants in landfill gas have found hundreds of different NMOC contaminants.[**NJ**]

When halogenated chemicals (chemicals containing halogens - typically chlorine, fluorine, or bromine) are combusted in the presence of hydrocarbons, they can recombine into highly toxic compounds such as dioxins and furans, the most toxic chemicals ever studied. Burning at high temperatures doesn’t solve the problem as dioxins are formed at low temperatures and can be formed as the gases are cooling down after the combustion process.⁴

Matter cannot be created or destroyed - it is one of the first lessons of high school physics. Throughout EPA’s reports on landfill gas utilization, they refer to the destruction efficiency of various landfill gas combustion technologies. They usually assume it’s about 98% or more. In other words, they pretend that these halogenated non-methane organic compounds simply go away. There is almost no talk about what happens to the chlorine, fluorine and bromine atoms that go into the burner.

Mercury and tritium cannot be destroyed through combustion and no efforts have been made to prevent their release into the environment when landfill gas is collected and burned. http://www.sciencenews.org/articles/20010707/fob1.asp

Isn’t it cleaner to burn landfill gas to make energy than to just flare it?

There is limited data comparing emissions from landfill gas flares to energy producing combustion devices (which includes boilers, turbines and internal combustion engines).

According to very limited data in a 1995 EPA report, carbon monoxide and NO_x emissions are highest from internal combustion engines and lowest from boilers. Flares and gas turbines are in the middle.⁵

Dioxin emissions data is also very sparse. EPA, in their 1998 dioxin inventory, looks at only a few tests and shows that, for the most part, flares produce more dioxin than internal combustion engines or boiler mufflers.⁶ However, a more comprehensive review (by the County Sanitation Districts of Los Angeles County in 199 of about 20 studies involving 76 tests at 27 facilities shows that internal combustion engines on average produce 44% more dioxin than shrouded flares. Since there is high variability in dioxin emissions from landfill gas burners (based on composition of waste dumped and also on the combustion technology - internal combustion engines are much more variable), these figures should not be applied to site-specific situations.⁷

Burning landfill gas is dirtier than burning natural gas. Whether using an internal combustion engine or a gas turbine, burning landfill gas to produce energy emits more pollution per kilowatt hour than natural gas does.⁸

Why is it that natural gas (a non-renewable resource which is not considered “green energy”) burns cleaner than landfill gas, yet energy from landfill gas gets away with being considered renewable green power?

But the landfill gas is there anyway (usually being flared), so why not use it to make energy?

This is a classic case of asking the wrong question.

It’s a very different thing to ask “what is the best way to manage landfill gas?” than to ask “how should we produce green, renewable energy?”

Green energy marketers aren’t in the business of managing landfill gas. If they want to be in the waste management business, then that’s a different story.

In brief, if you ask what the best way to manage landfill gas is, the answer is along the lines of “before you do anything with it, filter out the toxic contaminants and treat them with a non-burn technology.” If the question is how to produce green, renewable energy, the answer is “use technologies such as wind and solar that don’t create pollution in the process of making energy.”

Nothing that emits dioxins should be considered “green” or “renewable” energy.

“Green” or “renewable” resources shouldn’t produce pollution in the process of making energy. Anything that has environmentally-damaging emissions you can measure per kilowatt is not deserving of subsidies or preferential pricing afforded to “green power.”

So what should be done with landfill gas?

Well, let’s examine the options:

The default option is to do nothing. Doing nothing leads to gas migration off-site and can cause explosions. The release of the methane creates some global warming problems and the release of the toxic contaminants can cause cancer and other health problems in local communities. A New York study of 38 landfills found that women living near solid waste landfills where gas is escaping have a four-fold increased chance of bladder cancer or leukemia.^{9, 10}

Landfills should install gas collection systems to prevent the problems with gas migration. Once collected, landfills can do any of the other options. These options are focused around handling the methane (usually by burning it) and are not focused around addressing the toxics issues. Regardless of what is ultimately done with the gas, the gas should be filtered so that the halogenated compounds are segregated. Once filtered out, these compounds should not be combusted (as that doesn’t tend to improve the situation, but may make it worse). They should be handled as hazardous waste and isolated from the environment as best as is possible until there is a proven technology which can neutralize the toxics by converting the halogens to relatively harmless chemicals like salts.

The general options for dealing with landfill gas (once collected) are as follows:

1. flare it
   
2. boiler - makes heat
   
3. internal combustion engine - makes electricity
   
4. gas turbine - makes electricity
   
5. fuel cell - makes electricity
   
6. convert the methane to methyl alcohol
   
7. clean it up enough to pipe it to other industries or into the natural gas lines
   

Note: a more comprehensive list of options is online at http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/chap10.html

Flares

Flaring of landfill gas is either done in a candle flare or a shrouded flare. A candle flare is an open air flame. With such, there is no reliable means to monitor for dioxins or other toxic emissions. Shrouded flares involve enclosing the flame in an insulated cylindrical shroud which can be anywhere from 16 to 60 feet tall.¹¹ While dioxins can be tested for in such flares, it is possible that enclosing the flare will keep the post-combustion temperature in dioxin-formation range, resulting in increased dioxin emissions. Essentially, this is a lose-lose situation. It should be noted that some (perhaps most or all) shrouded landfill gas flares have exit temperatures of around 1400^oF - well above the dioxin formation range (which end around 752^oF). In such cases, dioxins will be formed in mid-air as the exhaust hits the cooler background air after leaving the stack.

Boilers

Boilers are among the cheapest options. They produce heat, not electricity. Boilers are generally less sensitive to landfill gas contaminants and therefore require less cleanup than other alternatives. Boilers have the lowest NO_x and carbon monoxide emissions of the combustion technologies.¹²

Landfill gas use in boilers bring in the issue of piping the gas to local industries. While boilers themselves may not require much cleanup of the gas, the pipelines do require some cleanup, since corrosive compounds in the gas (particularly the acids and hydrogen sulfide - H₂S) can damage the pipelines. There have been many concerns associated with landfill gas pipelines brought out by environmentalists living near landfills considering this use. Among the concerns are the integrity of the pipeline (at least one proposal involves lateral seams), liability issues, and the economic support of neighboring polluting industries which might use the gas.¹³ In addition, such projects have been used as excuses to develop additional polluting industry that would utilize the gas in their processes.

Internal Combustion Engines

IC engines are the dirtiest technology for burning landfill gas. They emit the most carbon monoxide and NO_x and they may be the largest dioxin source of the available technologies.¹⁴

Gas Turbines

Gas turbines are somewhere in the middle in terms of carbon monoxide and NO_x emissions. There isn’t enough data on dioxin emissions from landfill gas turbines to provide any sort of comparison.

Fuel Cells

Fuel cells are the most expensive technology, as they are still largely experimental. EPA describes fuel cells as “potentially one of the cleanest energy conversion technologies available.” In order not to “poison” the fuel cells, halogenated contaminants must be filtered out. This is a wonderful thing, since it demonstrates that such filtering technologies are realistic and may eventually be put into practice. However, in EPA’s twisted logic, they state that the filtered contaminants would be incinerated.¹⁵ This would defeat the point of filtering them in the first place, unless all we care about is the health of fuel cells.

Conversion to Methanol and/or Dry Ice

At least one company is involved with converting methane from landfills into methyl alcohol or methanol. However, the halogenated organics they filter out are sent to a flare (again defeating the point).¹⁶ Other companies have expressed interest in converting the carbon dioxide in landfill gas to dry ice for sale to industry. They have claimed that the carbon dioxide in landfill gas is actually more profitable to recover than the methane.

Cleaning up the Gas to Pipeline Quality

Since natural gas prices are so low, this is not expected to be economical anytime soon. It also requires a high degree of cleaning and filtering the gas. To the extent that the gas is not adequately filtered, then the landfill gas will be degrading the quality of the natural gas by adding more contaminants to the system.¹⁷

What about source reduction? How can we cut down on landfill gas?

As with any waste issue, the proactive solution is to look upstream and see what can be done to stop creating waste products. With landfill gas, it’s no different. Landfills are the end-point of much of the excesses of our wasteful economy. At the very beginning of the system, we must look at such things as phasing out of halogens in industrial use. This is the only way that we can stop chlorine, fluorine and bromine pollution and the organohalogens (dioxins, furans, etc.) that come with them. We also must consider the technology of landfills. There are communities in the United States which are recycling 80-90% of their waste (some even higher). It is the act of mixing materials together that makes waste. Source separation and recycling prevents this.

In landfills themselves, it makes sense to segregate organic wastes from other wastes by placing them in different cells of a landfill. This would concentrate the methane generation in an area where many of the toxic compounds won’t be present (which is not to imply that yard waste and such doesn’t come laden with pesticides and toxic sludge “fertilizer” applications).¹⁸ In consideration of landfill gas management, EPA dismissed comments which would favor waste segregation.¹⁹

The Global Warming Politics of Landfill Gas

Promoters of landfill gas combustion consistently point to the fact that methane is a potent greenhouse gas. This gets used as a reason to burn landfill gas to produce energy and also to have that energy considered “green.” Often ignored is the fact that most landfills which have gas collection systems are burning that gas in one form or another anyway. “Green energy” should not be used as an excuse to move from flares to internal combustion engines or gas turbines, as there is not a solid environmental argument for doing so. The incentives involved in green energy marketing are not enough that landfills without gas collection systems are going to install them to produce “renewable” energy from landfill gas. Landfill gas management should be based on isolation of toxic contaminants and not on the politics of global warming.

Proponents of landfill gas pipelines to boilers of local industries often argue that there would be displacement of other greenhouse-gas emitting fuels in the boilers of the pre-existing industries by the landfill gas that would be used in its place. While this can be a legitimate argument, it does not necessitate piping gas that is not cleaned up to natural gas pipeline standards.

EPA has a misnamed “Landfill Methane Outreach Program” which promotes burning landfill gas to produce energy. This program is part of EPA’s Methane Outreach Programs which are a part of their Atmospheric Pollution Prevention Division.²⁰ It is apparent that EPA’s agenda on landfill gas management is being driven by global warming politics and not sound management of toxic air pollutants.

As greenhouse gases go, methane is the least potent next to carbon dioxide. According to the EPA, methane is 21 times more efficient at trapping heat than carbon dioxide (CO₂). Nitrous oxide (N₂O) is 310 times more efficient than CO₂. Perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) are anywhere from around 1,000 to 10,000 times more effective than CO₂. Another fluoridated compound, sulfur hexafluoride (SF₆), traps 23,900 times as much heat as CO₂.²¹ Methane is responsible for 10.6% of global warming damage from human-sources in the U.S. Of this, 35.8% is from landfill gas. Thus, 3.8% of U.S. global warming damage is from methane in landfill gas.²² This is hardly a reason to advocate burning it one way vs. another, or even burning it at all. Since methane in captured landfill gas can be converted to methyl alcohol without requiring combustion, there is no need to have to subject the other chemical contaminants in landfill gas to incineration.

Why is there such a push for landfill gas to be considered “renewable” energy?

Landfill gas and other “biomass” (incineration) technologies are cheaper to develop than wind (which is the next cheapest “renewable” technology). Energy from landfill gas projects also provides the easiest-to-obtain new renewable (built since the inception of green energy marketing) for the Green-e certification process.

It is because of this that we don’t expect to see as much development of truly clean renewables from green energy marketing as we expect to see development of polluting landfill gas and biomass technologies. While not a renewable energy source, cheap natural gas is also likely to undercut renewables. Until we succeed at knocking out polluting technologies like “biomass” from the definition of renewables, we won’t see the true potential for long overdue wind development.

FOOTNOTES:

1. “Technical Data for Natural Gas,” Ely Energy http://www.elyenergy.com/tdngtypchemcomp.htm Contaminants in natural gas include organometallic compounds such as those containing lead and mercury, as well as many other compounds which lead to the formation of hazardous air pollutants, including some halogenated compounds. Natural gas lines have also been known to be contaminated with PCBs. Documentation on this can be found on the web at http://www.energyjustice.net/naturalgas/
   
   
2. “Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed Standards and Guidelines” Document # is EPA/450/3-90/011A. March 1991, 544 pages. http://www.epa.gov/ttn/atw/landfill/landflpg.html#TECH
   
   
3. “Growth of the Landfill Gas Industry,” Chapter 10 of the “Renewable Energy Annual 1996″ report by the U.S. Department of Energy’s Energy Information Administration. Available online at http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/chap10.html
   
   
4. The 1994 EPA Dioxin Reassessment, Estimating Exposure to Dioxin-Like Compounds, Volume 2, Chapter 3 http://www.cqs.com/epa/exposure/ Dioxins are formed from around 200^oC (392^oF) to 400^oC (752^oF).
   
5. “Methodologies for Quantifying Pollution Prevention Benefits from Landfill Gas Control and Utilization,” EPA document #600SR95089, July 1995.
   
6. “The Inventory of Sources of Dioxin in the United States,” EPA/600/P-98/002Aa, April 1998.
   
7. Caponi, Frank R., Ed Wheless & David Frediani, “Dioxin and Furan Emissions From Landfill Gas-Fired Combustion Units,” County Sanitation Districts of Los Angeles County, 98-RP105A.03, 1955 Workman Mill Rd. Whittier, CA 90607.
   
8. Note 5 supra.
   
9. “Investigation of Cancer Incidence and Residence Near 38 Landfills With Soil Gas Migration Conditions, New York State, 1980-1989,” State of New York Department of Health, (Atlanta, Ga: Agency for Toxic Substances and Disease Registry, June, 1998). Available from the National Technical Information Service in Springfield, Virginia [800-553-6847]; request publication PB98-142144.
   
10. “Landfills are Dangerous,” RACHEL’s Environment & Health Weekly #617, September 24, 1998. http://www.rachel.org/bulletin/index.cfm?issue_ID=1149
    
    
11. Note 7 supra.
    
12. Note 5 supra.
    
13. All of these issues have been raised by the Alliance for a Clean Environment (ACE). ACE worked for several years to successfully stop plans for building a 5 mile pipeline to pipe the toxic landfill gas from Waste Management Inc.’s Pottstown, PA landfill to an Occidental Petroleum vinyl chloride facility on the other side of town.
    
14. Note 5 supra.
    
15. “Demonstration of Fuel Cells to Recover Energy from Landfill Gas: Phase I Final Report: Conceptual Study,” EPA #600SR92007, January 1992.
    
16. Conversation with Bill Wisbrock of Alcohol Solutions, January 12, 1999.
    
17. Note 3 supra.
    
18. Even the Natural Lawn company, which markets environmentally-benign lawn care, uses sewage sludges in their products which they spray on their customer’s lawns. Sewage sludges contain a stew of toxic chemicals which aren’t filtered out before being sold as fertilizer. For background on sewage sludge, visit http://www.ejnet.org/sludge/
    
    
19. “Air Emissions from Municipal Solid Waste Landfills. Background Information for Final Standards and Guidelines.” Document # is EPA-453/R-94-021. December 1995, 311 pages. http://www.epa.gov/ttn/atw/landfill/landflpg.html#TECH
    
    
20. See their website at: http://www.epa.gov/methane/
    
    
21. See EPA’s Greenhouse Gas Inventory
    
    
22. Ibid.
    

South Africa’s first landfill methane gas-to energy projects, powered by GE Energy’s Jenbacher generator sets, will be commissioned at two sites near the city of Durban on the country’s east coast in early 2007. The plants are in the municipal region of eThekwini, which in Zulu means “in the place of the bay.”

The plants, at the La Mercy and Mariannhill landfills, will serve as renewable energy reference projects, providing much-needed electricity to the municipal grid. Meanwhile, funds from the sale of carbon credits – which was the key to making the project economically viable –also will be used in part for community upgrades.

For the La Mercy and Mariannhill power plants, GE supplied two containerized gen-sets to the projects’ contractor, Envitech Solutions (Pty) Ltd of Benoni, South Africa. Envitech Solutions installed the Jenbacher units and gas extraction equipment on behalf of Durban Solid Waste (DSW), which operates the eThekwini Metropolitan Municipality’s solid waste disposal and owns both landfill sites.

For La Mercy, Envitech Solutions installed a Jenbacher JGC 312 GS-L.L. gen-set and for Mariannhill, a JGC 320 GS-L.L. unit. Electrical output for the JGC 320 unit is 1064 kW and 526 kW for the JGC 312 unit. Electrical efficiency for each unit is 40.8% and 39.1%, respectively.

GE Energy’s Jenbacher gas engine business was recently awarded a contract to supply two CHP units for a new, wood gas project in the town of Oberwart in the Austrian province of Burgenland. The CHP units will be supplied to Ortner GmbH and include two Jenbacher JMS 612 GS-S/N.L engines. The plant is expected to be commissioned in November 2007, providing an electrical output of more than 2 MW and thermal output of 6 MW. The generated heat will be fed into the district heating system operated by Energie Oberwart, supplying heating to the local hospital and future facilities in the industrial area of Nord. The plant’s produced electricity will be fed into the local public grid.

As the main contractor, Ortner GmbH has been commissioned to design and construct the entire plant on behalf of Energie Oberwart Errichtungs-GmbH. Ortner GmbH is responsible for the overall engineering, construction, systems engineering, and instrumentation and control equipment. The project is scientifically supported by the Vienna University of Technology’s Institute of Chemical Engineering.

Large municipal or industrial landfills produce gas that can be tapped to generate electricity. Microorganisms that live in organic materials such as food wastes, paper or yard clippings cause these materials to decompose. This produces landfill gas, typically comprised of roughly 60 percent methane and 40 percent carbon dioxide (or “CO2″).

The US Environmental Protection Agency (EPA) requires all large landfills to install collection systems at landfill sites to minimize the release of methane, a major contributor to global climate change. Though not a renewable resource, landfill gas will be in great supply absent major innovations in solid waste management systems and could supply up to 1 percent of the nation’s energy demand.

Landfill gas is collected from landfills by drilling “wells” into the landfills, and collecting the gases through pipes. Once the landfill gas is processed, it can be combined with natural gas to fuel conventional combustion turbines or used to fuel small combustion or combined cycle turbines. Landfill gas may also be used in fuel cell technologies, which use chemical reactions to create electricity, and are much more efficient than combustion turbines.

What are the environmental impacts?

The environmental impacts of landfill gas begin with issues surrounding landfills themselves - land use impacts and surface and groundwater issues. Does reliance on landfills discourage more environmentally preferred waste management substitutes, such as waste reduction, reuse and recycling?

Since the landfill, typically, is sited for other municipal purposes, many of the negative issues associated with landfills themselves are not incorporated in the analysis of landfill gas as a power source.

Use of the gas produced by landfills may reduce the harmful environmental impacts that would otherwise result from landfill operations. Landfill gas electricity generation offers major air quality benefits where landfills already exist or where the decision to build the landfill has already been made.

Landfill gas power plants reduce methane emissions, a global climate change agent with 23 times the negative impact of CO2.

A landfill gas power plant burns a waste - methane — that would otherwise be released into the atmosphere or burned off in a flaring process. Methane is a highly potent agent of global climate change, having about 23 times the negative impact on a pound-by-pound basis as CO2. Landfill gas combustion produces some CO2, but the impact of these emissions on global climate change is offset many times over by the methane emission reductions.

While new EPA regulations require gathering and flaring of methane from large landfill operations, small landfills, which fall outside the federal agency’s jurisdiction, may amount to as much as 40 percent of the methane generated by landfills nationwide.

Landfill gas generators produce nitrogen oxides emissions that vary widely from one site to another, depending on the type of generator and the extent to which steps have been taken to minimize such emissions. Combustion of landfill gas can also result in the release of organic compounds and trace amounts of toxic materials, including mercury and dioxins, although such releases are at levels lower than if the landfill gas is flared.

There are few water impacts associated with landfill gas power plants. Unlike other power plants that rely upon water for cooling, landfill gas power plants are usually very small, and therefore pollution discharges into local lakes or streams are typically quite small.

LANDFILL GAS UTILIZATION PROJECT

MOUNTAINGATE LANDFILL, WEST LOS ANGELES

PROJECT BACKGROUND AND SCOPE

NST/Engineers, Inc. prepared updated P&ID information and plant safety and operating instructions for the second decade of the MountainGate Landfill Gas Plant’s operation.

The Plant and well field system were designed, built, and have been operated for about two decades as a GSF facility. The Plant is owned and operated by the GSF Energy, a wholly owned subsidiary of Montauk Energy Capital, a subsidiary of DQE Financial Corp.

The landfill consists of eight canyons in the Brentwood-Westwood area of West Los Angeles, with the plant located off Sepulveda Boulevard.

The Los Angeles County Sanitation Districts (LACSD) operated the landfill until 1980. LACSD deposited municipal solid waste into the eight canyons. The GSF energy plant recovers its feed gas from five of the canyons covering approximately 375 acres. Four of the canyon surfaces are now supporting 27 holes of championship golf as part of the MountainGate Country Club.

The GSF Facility consists of gas well fields, a gas processing plant, and a gas delivery pipeline to the customer, the University Of California Los Angeles (UCLA). The facility is designed to:
1) recover the crude methane gas naturally being generated within the landfill,
2) process the gas to produce “medium Btu” gas (about 500 Btu), and
3) deliver it 4.5 miles away via a dedicated pipeline to a 40MW cogeneration facility at the UCLA campus.
UCLA uses this otherwise wasted and polluting LandFill Gas (LFG) to provide a significant portion of their boiler station’s fuel needs.

CRUDE GAS PRODUCTION AND COLLECTION AS PLANT FEED

The MountainGate plant collects about four million standard cubic feet per day of LFG . The gas is drawn from 125 wells ranging between 60 and 100 feet in depth. The wells are connected to a main collection header that carries the gas to the entrance of the canyon and down an 80-ft cliff to the processing plant. The total gas collection system is about 9 miles in length including the main line and laterals.

There are a number of production wells in each canyon wellfield. Each wellhead connects with the near-surface-level lateral system of gas collection piping and delivery pipelines to the plant. Where the wellfields are a mile or so from the plant, a booster blower is used to supplement the vacuum produced by the plant inlet blower. The flowrate and composition of the gas from each well is carefully monitored. Wellfield technicians “tune” the wells (adjust the gas flowrates) to get the maximum flowrates with an acceptable composition.

MIGRATION CONTROL

GSF Energy operates another gas collection system at MountainGate designed to prevent the migration of LFG into neighboring, upscale, residential communities. These are smaller wells drilled at the periphery of producing wellfields. The gas migration control system consists of 125 control wells, 230 monitoring probes, seven miles of pipeline and two flares.

These migration control systems are complete in themselves. They draw an even more crude gas from the wells to the lateral system with blowers. This gas is also collected in piping manifolds, and then disposed of by controlled combustion.

By operating both production and migration control systems at maximum efficiency, GSF Energy is able to meet both the environmental and energy recovery objectives of the project.

CRUDE GAS PROCESSING TO PRODUCE SALES GAS

The processing plant draws the crude methane from the well fields. Numerous vapor-liquid separators are used throughout the gas collection, processing, and pipeline delivery steps to remove contaminating liquid condensate from the gas. The liquid is mostly water and a complex mixture of hydrocarbons. The hydrocarbons, resembling contaminated gasoline or kerosene, are separated from the wastewater and disposed of, or sold.

Further vapor contaminant removal is accomplished by solvent scrubbing. The crude gas is compressed and then cooled and scrubbed by countercurrent solvent flow.

The solvent is regenerated by countercurrent air stripping. The stripper overhead vapor stream is incinerated at 1800 deg.F in a flare, eliminating objectionable emissions.

SALES GAS DELIVERY TO UCLA

The processed gas is analyzed to determine its composition and fuel value. If the gas does not exceed the safe level of oxygen content, it is sent through the pipeline as a boiler fuel to UCLA.

Pipeline gas is analyzed routinely for: methane, carbon dioxide, hydrogen, nitrogen, oxygen, and Btu content. The composition averages about half methane and usually less than 0.1% oxygen, with an energy content of about 500 Btus.

If the oxygen content rises to 0.5%, an alarm is initiated. Should the oxygen content rise to 1.0%, the plant is shut down. Then, LFG draw from the wellfields is tuned to lower the oxygen content. The gas pressure delivered to the sales pipeline is controlled at about 100 psig.