Value to Work Trucks
As we transition from petroleum fuels to the ultimate clean solution, natural gas (NG) may well be the most important alternative fuel to the transportation industry. According to Natural Gas Vehicles for America (NGVA), approximately 13 million vehicles worldwide are powered by NG; of these, only 112,000 can be found in the U.S. (a negligible figure, given the 300 million vehicles currently operating in the nation).
NG can be used as transportation fuel and also as a source of fuel to generate the electricity that powers vehicles. Strengths and benefits of NG include:
- High supply – In the U.S. alone, a total of about 100 years worth of NG reserves are currently technically recoverable.
- Less harmful to the environment - When used in place of petroleum as a fuel, NG produces less greenhouse gas (GHG) and pollutants.
- Pipeline networks already exist – The transmission system for NG is fairly well established.
- Renewable source – NG is captured as waste and biomass from landfills
- Available in multiple forms – NG can be offered in two forms:
- Compressed natural gas (CNG) is gaseous and can be stored on the vehicle in high pressure tanks
- Liquefied natural gas (LNG) has a high British Thermal Unit (BTU) content and works well in large quantities. LNG requires special storage considerations.
Natural gas is a mixture of light hydrocarbon gases, predominantly methane (CH4). As delivered through the national pipeline distribution system, natural gas also contains hydrocarbons such as ethane and propane and other gases such as nitrogen, helium, carbon dioxide, hydrogen sulfide, and water vapor.
The quantities of these various compounds may vary considerably depending on the source and the amount of processing that the gas has received. The percentage of methane in natural gas typically ranges between 83 percent and 99 percent. The second most common component is ethane (C2H6), which can range between 1 percent and 13 percent.
Methane is an odorless gas but in commercial applications an odorant–typically methyl mercaptan–is added for leak detection.
Natural gas is the lightest hydrocarbon, which is a gas at atmospheric pressure, and is classified as a gaseous compound.
Natural gas is drawn from wells or extracted in conjunction with crude oil production.
Natural gas currently consumed in the United States is sourced from these countries:
Domestic – 85%
Canada – 13%
Other – 2%
When produced through the anaerobic decomposition of biomass–decaying organic materials such as waste from landfills, wastewater, and livestock–methane is commonly referred to as “bio-methane.” Methane can also be produced through various industrial processes. Like natural gas, raw bio-methane is typically very dirty and must be scrubbed and dried before it is suitable for use as a transportation fuel. Bio-methane is classified as a renewable fuel.
The United States has at least a 100-year supply of natural gas using today’s technology, with a consumption rate of about 20 trillion cubic feet of gas a year. In 2009, the Potential Gas Committee estimated that the U.S. has a total available future supply of 2,074 trillion cubic feet of gas. This figure represents an 11 percent increase over the previous (2007) estimate, primarily due to the development of improved extraction techniques.
The U.S. has an extensive natural gas distribution system, which can quickly and economically distribute natural gas to and from almost any location in the lower 48 states. Gas is distributed between and within states by 300,000 miles of transmission pipelines. In addition, 1.9 million miles of distribution pipes transport gas within utility service areas.
Natural gas is an approved, clean fuel listed in the 1990 Clean Air Act and the Energy Policy Act of 1992. CO2emissions for natural gas are 58.5 kilograms per million BTU (gasoline emits 70.88 kilograms per million BTU of CO2).
Tests conducted by the U.S. Environmental Protection Agency show that natural gas-fueled vehicles produce 20 percent to 40 percent less carbon monoxide and about 80 percent fewer toxins and other smog-producing emissions than gasoline engines per BTU of energy produced. Natural gas is classified as being nontoxic although it is an asphyxiant.
The development of natural gas as an internal combustion fuel is supported by Natural Gas Vehicles for America (NGVAmerica), a national organization dedicated to the development of a growing, sustainable and profitable market for vehicles powered by natural gas or hydrogen.
The Clean Vehicle Education Foundation (CVEF) is a non-profit national organization whose mission is to assess and guide alternative fuels including NGV and natural gas-to-hydrogen R&D³ activities, build awareness and foster deployment of alternative fuel systems including natural gas- and other clean fuel-powered vehicles in the public and private sector.
Natural Gas as an Internal Combustion Fuel – When used as a transportation fuel, natural gas may be stored on board the vehicle as either a compressed natural gas (CNG) or as a liquefied natural gas (LNG). CNG is the more prevalent form, but LNG is seeing increased use in heavy vehicle applications, primarily because of its significantly increased energy density.
Energy density - 20,000 to 22,000 BTU per pound. 5.7 pounds of natural gas has the same energy density as one gallon of gasoline (125,000 BTU).
On-board vehicle storage - To provide adequate driving range, CNG must be stored onboard a vehicle in tanks at high pressure. Current CNG systems utilize storage pressures in the range of 3,000 to 3,600 pounds per square inch.
Octane rating - 120+
Fuel efficiency - A CNG-powered vehicle gets about the same fuel economy as a conventional gasoline vehicle on a gasoline gallon equivalent basis.
Fueling - CNG vehicles may be fueled using either a fast-fill or time-fill system. Fast-fill systems utilize a combination of a large compressor and a high-pressure storage tank system (called a cascade) to pre-compress and store natural gas. These systems can fill a CNG vehicle’s tanks in about the same amount of time it takes to fuel a comparable gasoline or diesel vehicle. Time-fill systems are typically intended for small fleet or home use and do not have a storage system. They utilize a much smaller (and less expensive) compressor which typically refuels a vehicle overnight at a rate of about one gallon per hour.
Supply source - CNG fueling systems (fast and slow fill) are connected to the natural gas pipeline distribution infrastructure.
Petroleum offsets - According to data provided by the Argonne National Labs the use of CNG as a transportation fuel will reduce U.S. petroleum consumption by approximately 100% compared to an equivalent gasoline fueled vehicle.
- Reduced greenhouse gas emissions
- Reduced engine wear and extended service intervals
- When used as an automobile fuel, CNG is stored onboard vehicles in tanks that meet stringent safety requirements.
- Natural gas fuel systems are "sealed," which prevents spills or evaporative losses.
- Natural gas has a high ignition temperature, about 1,200° Fahrenheit, compared with about 600° Fahrenheit for gasoline.
- Natural gas is not toxic or corrosive and will not contaminate ground water.
- Primarily domestically sourced. Purpose built engines with higher compression ratios (equivalent octane rating of 120+) provide improved performance and fuel economy.
Lifestyle cost factors
- Higher conversion costs than alternative fuels such as propane (primarily due to higher storage tank costs
- Very high infrastructure cost compared to other gaseous fuels
- Reduced vehicle maintenance costs
- Fuel tanks require periodic inspection and recertification
- Minimal driver training costs
Energy density - 75,000 to 85,000 BTU per gallon. 1.5 gallons of liquefied natural gas has the same energy density as one gallon of gasoline (125,000 BTU).
On-board vehicle storage - To produce LNG, natural gas is purified and condensed into a liquid by cooling to -260°F (-162°C). At atmospheric pressure, LNG occupies only 1/600 the volume of natural gas in vapor form. Because it must be kept at such cold temperatures, LNG is stored in double-wall, vacuum-insulated pressure vessels.
Octane rating - 120+
Fuel efficiency - An LNG-powered vehicle gets about the same fuel economy as a conventional gasoline vehicle on a gasoline gallon equivalent basis.
Fueling - To fuel vehicles, LNG is pumped into the vehicles much like other liquid fuels (although using much more sophisticated cryogenic fueling equipment. Refueling vehicles with LNG requires training because of the fuel’s ultra low temperature. It can cause frostbite if it contacts skin.
Supply source - LNG can be produced on-site from available natural gas, but in most cases it is delivered to the fueling site by tanker truck. In either case, the LNG is stored onsite in special cryogenic storage tanks.
Petroleum offsets - Offsets for LNG are approximately 97%.
Intangible benefits - Primarily domestically sourced. Purpose built engines with higher compression ratios (equivalent octane rating of 130) provide improved performance and fuel economy.
- Very limited availability at this time
- If not operated for a period of a week or more, LNG vehicle fuel tanks will vent a flammable gas mixture that could catch fire in the vicinity of an ignition source. To address this safety issue, LNG use should be restricted to frequently driven fleet vehicles or to vehicles stored outdoors.
- Training required to fuel vehicles
Lifestyle cost factors
- Higher conversion costs than alternative fuels such as propane (primarily due to higher storage tank costs)
- Infrastructure costs significantly less than for CNG
- Reduced vehicle maintenance costs
- Increased driver training costs (fueling procedures)
Lifecycle Greenhouse Gas Reduction – The use of natural gas as an internal combustion fuel produces significantly less carbon dioxide (CO2) than the use of an equivalent amount of gasoline or diesel fuel. CNGutilizes the national pipeline distribution system and LNG is distributed in a manner similar to gasoline and diesel fuel (tanker trucks) although the truck haul is typically longer than for petroleum products which utilize pipelines for much of their distribution. As a result, the total lifecycle greenhouse gas emissions for propane is 25% to 30% less than petroleum (Source -- Argonne National Labs).
Economic Drivers - Due to the fact that it is domestically produced and in plentiful supply, natural gas prices have remained relatively stable in recent years. As of January 2011, the price of natural gas as an engine fuel ranged between $1.52 and $2.63 per diesel equivalent gallon, with an average of $2.15. The equivalent diesel average for January 2011 was $3.45.
Other potential factors such as carbon credits, tax incentives, etc. will have a significant impact on the economic viability of natural gas as an engine fuel.
Vehicle and Equipment Suppliers
A well-established network of suppliers and vehicle modifiers is in place to facilitate the use of natural gas as an alternative fuel. In addition, several OEMs now offer factory warranted natural gas-fueled vehicles.