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Prometheus Produces World’s First Commercial LNG from Landfill Gas; Targeted for Public Transit Fuel

26 January 2007

Prometheuslng
Prometheus LFG to LNG plant at Bowerman Landfill. Click to enlarge.

Prometheus Energy Company has begun producing liquefied natural gas (LNG) from the world’s first landfill gas-to-LNG plant. The plant was installed in late 2006 at the Frank R. Bowerman Landfill in Orange County, California. The entire output of the plant will be used as an alternative fuel in public transport vehicles in the Orange County Transit Authority fleet.

The Bowerman Landfill currently flares enough landfill gas to make approximately 40,000 gallons of LNG per day, and this amount is increasing each year. The current plant, which has production capacity of 5,000 gallons per day, is the first of three phases planned to be built at the landfill.

On 20 January 2007, the plant produced LNG at the rate of 1,000 gallons per day. As the commissioning process continues, the company expects the plant’s operations to approach its nameplate capacity of 5,000 gallons per day.

At a production level of 5,000 gallons per day, the project will reduce carbon dioxide output by the equivalent of 10,000 tons per year.

Diagramtechnology
Prometheus LFG LNG system. Click to enlarge.

While the basic technologies and processes for the production of LNG are well established, Prometheus has focused on integrating and packaging them into a compact format for small-scale liquefaction. Prometheus’ process design incorporates a systematic approach to purification of LFG prior to and while cooling and liquefying the feed gas mixture. The process also uses a novel method to reject N2 from the LNG. The optimal recapture of work and thermal energy increases the overall thermal efficiency of the system while minimizing its capital costs, according to the company.

To compress, purify and cool the biomethane, Prometheus uses a modular approach. The Prometheus landfill gas system consists of the following:

  • Pre-Purification Module to remove corrosive sulfur compounds, low concentrations (parts per million) of non-methane-organic compounds (NMOCs) including siloxanes, and water from the LFG process stream and also compresses the LFG from ~2 psig to ~50 psig or more as required.

  • Bulk Carbon Dioxide (CO2) Purification Module to further purify the LFG process stream by removing CO2 using a proprietary cryogenic freezing technique that simultaneously pre-cools the methane (CH4) and any nitrogen (N2) while freezing out the CO2.

  • Combined Liquefaction and Post-Purification Module to liquefy the purified LFG and enhance the concentration of CH4 in the LNG by dynamic flash evaporation of the N2. The N2 rejection steps in the process reduce the N2 concentration to less than 3% in the LNG.

  • Refrigeration Module to provide the cooling to the process stream in the purification and liquefaction modules. The refrigeration system is a closed loop system that uses a separate refrigerant and therefore remains immune from process stream variations. Careful use of the cryogenic refrigerant allows maximum pre-cooling of the LFG process stream in stages—an important feature for increasing the thermodynamic efficiency of the overall purification and liquefaction.

  • Instrumentation and Controls Module to manage the entire LFG-to-LNG system. Once installed and configured, the system can be operated and managed remotely.

Together with three other projects, two in California and one in Poland, the company is working on developments with an estimated capacity of 65,000 gallons of LNG per day. In Poland, Prometheus has joined with the Polish company CETUS Energetyka Gazowa to form LNG Silesia to take advantage of coal mine methane opportunities in southern Poland and the emerging alternative energy markets present there.

The Company is also in the design phase of its landfill gas-to-LNG project at the Kiefer Road Landfill in Sacramento County, California, and in the build phase of a stranded gas well to LNG project in San Joaquin County, California.

(A hat-tip to John!)

January 26, 2007 in LFG, LNG | Permalink | Comments (10) | TrackBack (0)

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Comments

What's the point of liquefying? Isn't there a NG pipeline near by.

1654 landfills in the usa according to

http://www.epa.gov/msw/facts.htm

If all were capable of this production potentially a good 10% of our gasoline use.

DS,
I suppose it is for LNG fueled vehicles.

Love the modular design. If a major component needs to be replaced/upgraded, or needs major servicing, you can move the various parts in and out.

Lotfw:

There are zillion estimations of municipal waste to energy potential. Most estimations (optimistic ones) put landfill biogas potential comparable to about 3-5% of domestic gasoline use.

EPA requires collection of biogas from landfills strictly on basis of air quality protection. Using it to produce energy or fuel is a win-win situation.

Excellent project! I hope it meets its goals.

They claim an annual CO2 equivalent of 10,000 tons/year. I assume they are referring to the methane which is a much stronger greenhouse gas than CO2 and is frequently denominated in CO2 equivalence.

I notice in the description they have a waste stream of solid CO2. I wonder what they are doing with it. The most expensive part of carbon sequestration is concentration.

DS -

landfill gas does not meet the purity standards required for NG distribution networks. Liquefaction is one way way to purify gas mixtures, as different compounds become liquid at different temperatures.

OCTA currently operates a fleet of CNG buses. LNG can easily be pressurized by allowing it to boil off, so the filling station does not require a compressor.

However, with a ready source of LNG now available, they might well consider purchasing some HDVs that can use LNG directly. These feature smaller, lighter tanks but require special safety training for operators. LNG needs to be vented continuously and therefore only makes sense for vehicles that are in use for many hours every day.

http://engva.org/content.aspx?PageID=386

The attention to entropy management evident in the description of the technology sounds exemplary.  It's this sort of detail-oriented approach which can produce systems which get close to theoretical efficiencies.

This is the sort of thing which ought to be used for teaching examples in intro thermodynamics courses, and perhaps in AP physics as well.

That said, it is indeed time to start looking at ways to exploit the CO2 stream.  Perhaps burn just enough methane in it to get rid of toxics like siloxane, and try one of the algal conversion schemes on it.

OCTA actually runs over 200 LNG buses already and has for years. The LNG from this project will be used for their existing buses. They are only just beginning to buy CNG buses... FYI.

I agree with Engineer-Poet, the best method of dealing with the CO2 stream is to run it into an algal emissions-to-biomass reactor. With the combination of removing so much methane from the atmosphere, offsetting the production/use of a good amount of conventional LNG, and recapture of the emitted CO2 into biomass/liquid transportation fuels, this is indeed a good teaching example. I will recommed that my Physics profs are aware that this is taking place!

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