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Some Technical and Boring Stuff About Compressed Natural Gas (CNG) – Why Is CNG a Cleaner and Affordable Renewable and Non-Renewable Alternative Fuel for the Transportation Industry

August 15, 2010

How is Compressed Natural Gas Compared to Petroleum and other liquefied Fossil Fuels?

In the uncompressed state, natural gas has a BTU content 83% of regular gasoline (since natural gas is in the gaseous state and gasoline is in the liquid state, the comparison is based on Energy Content or BTUs):

• CNG: 103,000 -BTU per therm (100 standard cubic feet); Note: 1,030 BTU/scf x 100 scf/therm; BTU – The amount of heat (energy) required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

• Gasoline (regular): 124,800 BTU per GGE; Note: This is BTU energy content of gallon of gasoline (regular)

In actual practice, an American Honda Civic GX, which is American made and delivered to run on natural gas, with a 1.8 L 4-cylinder engine and an 8 GGE natural gas tank, will give 225 – 250 mile range.

When used as a fuel for vehicles, Natural Gas is compressed to 3,600 psi not 10,000 psi.

Filling time depends on the station and compressor design. While a time fill station which will fill the tank overnight can cost from $4K to $650K, a fast fill which fills as fast as a typical gasoline station can cost about $1.5 million (the price is use in my initial posting).

With today’s 5th generation technology for vehicles unfitted for natural gas, actual MPGGE (miles per gasoline gallon equivalent) is equal to or greater than gasoline powered vehicles.

Typical dedicated NGVs can reduce exhaust emissions of (data from Clean Vehicle Education Foundation):
• Carbon monoxide (CO) by 70 percent
• Non-methane organic gas (NMOG) by 87 percent
• Nitrogen oxides (NOx) by 87 percent
• Carbon dioxide (CO2) by almost 20 percent below those of gasoline vehicles.

Heavy-Duty vehicles running on Natural Gas meet the EPA’s 2010 stringent “Engine Emissions and Fuel Requirements” of:
• Particulate Matter – 0.01 g/bhp-hr
• NOx – 0.2 g/bhp-hr

As reported by Clean Vehicle Education Foundation, the cost of natural includes the following:
• Gas Commodity (one Mcf = about 8 GGE of uncompressed natural gas
o When NYMEX Mcf was $12.00, commodity component of CNG was $1.50/GGE
o When NYMEX Mcf was $8.00, commodity component of CNG was $1.00/GGE
o Currently NYMEX Mcf is $3.44, commodity component of CNG is $0.43/GGE
• Pipeline transportation to utility’s city gate
• Local gas distribution company service
• State/Local gross receipts / use taxes and/or special assessments
• Compression
• Station Maintenance
• Capital / Equipment amortization.

With all of these costs included in the at the pump price for natural gas (taxable fuel use/ sales):
• $1.45 to $1..85 (at $3.44 per Mcf)
• $1.92 to $2.32 (at $7.20 per Mcf) as compared to $3.50 to $3.70 for gasoline and 3.75-4.05 for diesel

Finally, the life-cycle costs are lower (data provided by Clean Vehicle Education Foundation).

For a Passenger Van used as a Limo:
• GVWR: >8,500 lbs. and 8,500 #, 26,000 lbs
o Blue Bird All American RE or Thomas Built Saf-T-Liner (both factory-built with CWI ISL-G engine)
• MPG 6.0 – 7.0 / DGE (avg. 18,000 miles per year) DGE = diesel gallon equivalents
• Fuel Use: 2,650 DGE/yr
• CNG Premium: $43,000 (before fed tax credit)
• Fed Tax Credit: $32,000
• Remaining Premium (assuming no grant): $11,000
• Simple Payback: 2.8 yrs
• Life-cycle cost advantage: $40,500 (based on 13 yr life @ $1.50/DGE savings).

Hope this primer help a little and did not put you to sleep.

8 Comments leave one →
  1. August 16, 2010 2:22 PM

    Ultra-Low Sulfur Biodiesel is more efficient and cleaner than natural gas.

  2. August 16, 2010 2:40 PM

    ULSB – how much can be produced today (08.16.2010) and at what cost? Utilities need a reiliable form or energy that is available 24/7/365, no if ands of buts.

  3. Gary D. Colby permalink
    August 19, 2010 9:52 AM

    [copied from a discussion on another forum at Barry’s request — note: context of discussion was comparing ecological “cleanness” of CNG production with other fossil fuel production and biofuel production. GDC]

    I’m not so sure that CNG production can be declared “clean” or “dirty” quite so broadly.

    Here in Pennsylvania and neighboring states, a tremendous number of NG wells have been bored in the Marcellus shale formation. Although the wellheads tend to have a relatively small geographical footprint, the wells that radiate outward from them extend over a broad area.

    There is, of course, a fair amount of concern generated mostly by unfamiliarity of folks with the process. However, there are legitimate environmental and health concerns as well. Apart from the obvious hazard of wellhead explosions (inherent in any gas extracting operation), shale extraction has its own hazards including, unfortunately, the occasional bout of flammable tap water (see picture at this link: ).

    Unlike extraction of NG from underground gas pockets or from decaying municipal wastes, extraction of NG from shales requires that the underground substrate be broken up to increase the porosity of the substrate, permitting recovery of NG at a practical rate. A common method of achieving this in the Marcellus shale formation (and elsewhere) is called hydraulic fracturing (“fracing” or “fracking”), which is a method in which a fluid at high pressure is injected into a well to open or expand fractures in the well substrate.

    Fracking fluid is a curious substance, usually containing at least a gritty substance (a “proppant” that props open new or expanded fractures) and a biocide or other anti-microbial ingredient (to retard growth of bacterial ‘gunk’ in the fractures). A significant contribution to perception problems is that fracking fluid often contains not-publicly-disclosed (sometimes proprietary) ingredients. There are at least two significant problems arising from the fracking process for extracting NG:

    First, by increasing the porosity of the geologic formation, fracking facilitates migration of NG to wellheads (and other nearby formations, potentially including underground water sources that are or lead to human aquifers). However, on the theory that “a hole is a hole,” other subterranean substances can migrate through the increased porosity of the formation. Thus, undesirable naturally-occurring substances (e.g., benzene and other organic compounds that can also occur in NG-bearing rock) become increasingly mobile and can travel to areas where they previously did not (or at least do so more quickly). So, even ignoring NG and any injected materials, fracking can enhance movement of underground substances to undesired locations (e.g., well water).

    Second, fracking fluids themselves can be undesirable contaminants. Apart from obvious spills like the release of tens of thousands of gallons of fracking fluid in Clearfield (?) County earlier this year, components of fracking fluid can seep through the fractures induced in the well substrate and potentially beyond. Disclosures like the article referenced above (i.e., allegations that drillers had included diesel fuel in their fracking fluids) cause concern that drillers are ‘poisoning’ well water. Even though drillers may justifiably wish to keep confidential the composition of their drilling fluid (i.e., to prevent other drillers from reaping the benefit of their research), the confidentiality can be perceived as “hiding something,” especially to a landowner who discovers an undesired chemical in his water.

    The point of this long ramble, though is to highlight that CNG cannot be declared “clean” or “dirty” with a broad brush — much depends on how it’s produced. As easily-extracted (i.e., relatively clean) NG formations are depleted or as production from such clean formations reaches a maximum rate, NG production will come to depend on “dirtier” methods of production.

    [intervening comment by another omitted — gist was ‘fossil CNG still produces more newly-released CO2 than biodiesel’]

    Yeah, I should, of course, have acknowledged that the same amount of CO2 is released by burning NG, regardless of its source.

    (By the same measure, though, unless you’re using B100, you’ve got to consider the amoung of fossil carbon being released from biodiesel blends. Also, regardless of the blend, you need to consider the carbon equivalents released in producing biodiesel, which can be substantially more than what’s released in NG harvesting).

    The point’s the same, though — the amount of fossil carbon released per unit of transportation distance provided is relevant, regardless of the fuel type or source.

  4. August 23, 2010 5:01 PM

    The small-scale LNG plant allows localized peak- shaving to occur – balancing the availability of natural gas during high and low periods of demand. It also makes it possible for communities without access to natural gas pipelines to install local distribution systems and have them supplied with stored LNG.

  5. August 27, 2010 7:49 AM

    The only direct knowledge of renewable energy and Obama’s new policies are that my brother-in-law went to a tech school for two years, graduated, and is now working out West on wind turbines.

    He loves his job. :-)

    The company that owns the wind farms is based in Spain.

  6. December 6, 2010 11:36 PM

    I have to admit that i sometimes get bored to read the whole thing but i think you can add some value. Grats !

  7. December 7, 2010 12:40 PM

    Very Nice website. I built mine and i was looking for some ideas and you gave me a few. The website was developed by you?

    Thank you

  8. June 2, 2011 1:03 AM

    I love it, I would love for you to be a guest writer on my blog sometime, let me know.

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