Happy Air Quality Awareness Week! Read Up How Alt Fuels Helps to Lower Emissions!

Currently, the U.S. Environmental Protection Agency (EPA) requires all 2010 and newer engines and vehicles to meet the same emissions standards, regardless of fuel type. Even though this standard is in place for all newer engines and vehicles, most alternative fuel vehicles (AFVs) provide greater reductions in tailpipe and greenhouse gas (GHG) emissions when compared to petroleum-powered vehicles; including the emissions: nitrogen oxides (NOx), volatile organic carbons (VOCs), and ozone (O3).

All-electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs; when in all-electric mode) produce zero tailpipe emissions. When using the internal combustion engine, PHEVs produce tailpipe emissions, such as NOx and VOCs.  Although, these emissions are typically lower than those of comparable petroleum-powered vehicles. EVs and PHEVs may produce well-to-wheel emissions (emissions measured as a sum of the fuel’s entire life cycle) depending on the source of electrical power used to charge the battery, such as a power plant.

Biodiesel also offers tailpipe GHG emissions benefits compared to petroleum diesel. The GHG emissions benefits of biodiesel are especially significant because the carbon dioxide (CO2) released during fuel combustion is offset by the CO2 captured by the plants from which biodiesel is produced. However, biodiesel does slightly increase NOx emissions. Though the integration of sophisticated engine controls—as well as fueling and exhaust after-treatment devices—are the determining factors governing how clean a vehicle or engine will be.

As with conventional fuels, the use and storage of ethanol blends can result in emissions of regulated pollutants, toxic chemicals, and GHGs. Emissions of primary concern from ethanol include hydrocarbons, NOx, carbon monoxide (CO), air toxics, and CO2. However, when compared to gasoline, the use of high-level ethanol blends, such as E85, generally result in lower emissions levels, including NOx and VOCs.

Because natural gas is a low-carbon, clean-burning fuel, using natural gas can result in substantial reductions of hydrocarbon, CO, NOx, and GHG emissions. Natural gas vehicles can provide emissions benefits—especially when replacing older conventional vehicles or when considering life cycle emissions.

Propane is also an inherently clean burning fuel due to its lower carbon content. When used as a vehicle fuel, propane can offer life cycle GHG emissions benefits over conventional fuels, depending on vehicle type, and drive cycle. In addition, using propane in place of petroleum-based fuels may reduce some tailpipe emissions. Emissions from propane vehicles are comparable to those of gasoline and diesel vehicles with modern emissions controls. Propane is frequently used to replace gasoline in smaller applications, such as forklifts and commercial lawn equipment. Because propane is a low-carbon fuel, a switch to propane in these applications can result in substantial reductions of hydrocarbon, CO, NOx, and GHG emissions.

Please note, that O3 is a GHG that is not a direct vehicle emission; it is formed in the air through reactions of NOx, VOCs, and atmospheric air in the presence of sunlight. As such, AFVs that reduce NOx and VOCs can reduce the formation of O3. Generally, O3 formation in urban areas is more VOC-sensitive, while it is more NOx-sensitive in rural areas.

For more information on AFV emissions, please refer to the following Alternative Fuels Data Center (AFDC) pages:

·         Emissions from Hybrid and Plug-in Electric Vehicles        (

·         Biodiesel Vehicle Emissions (

·         Ethanol Vehicle Emissions (

·         Natural Gas Vehicle Emissions (

·         Propane Vehicle Emissions (

You may also be interested in the Argonne National Laboratory’s (ANL) Alternative Fuel Life-Cycle Environmental and Economic Transportation (AFLEET) Tool ( to calculate and compare the emission reduction benefits of AFVs compared with conventional vehicles. Instructions for using the AFLEET Tool are available here: For further information on how to use the AFLEET Tool, you can also view the Clean Cities webinar on how to use the AFLEET Tool, located on the Clean Cities Webinar Archives page (

Additionally, you may also refer to the AFDC’s Petroleum Reduction Planning Tool ( This tool is a simple calculator for annual petroleum and GHG reductions. In particular, you may use the “Replace Vehicles” simulation to compare the annual GHG reductions associated with switching fleet vehicles from conventional fuels to alternative fuels.

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15th Anniversary Gala | BR River Center

Click here to purchase tickets!


Celebrate 15 years of success!

May 21  |  6:30pm-9:00pm

- Guest of Honor: Mayor Kip Holden & Miss Louisiana
- Indoor alternative fuel vehicle expo
- Live music by BIG FUN BRASS BAND
- Presentation of the Louisiana Clean Fuel Leader Awards by
Master of Ceremonies, Commissioner Mike Strain
- Food, drinks, live music, and FUN!

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TRS Question of the Month: What are the weight limits for heavy-duty vehicles on interstate highways? What weight limit exemptions exist for vehicles equipped with idle reduction technology?

Question of the Month: What are the weight limits for heavy-duty vehicles on interstate highways? What weight limit exemptions exist for vehicles equipped with idle reduction technology?

Answer: Under federal law, no vehicle weighing more than 20,000 pounds (lbs) on one axle, 34,000 lbs on a tandem axle, or 80,000 lbs overall may access federal interstate highways (e.g., Interstate 70, which runs across the country from Maryland to Utah), regardless of where they get on the highway.[1] States must enforce these requirements, or they may not be eligible for federal highway funding. However, the U.S. Department of Transportation (DOT) allows states to offer weight-limit exemptions for heavy-duty vehicles (HDVs) with on-board idle reduction technology.

Please note that states may set their own weight restrictions for roads that start and end within their boundaries, but we will focus on interstate highway requirements here.

Idle Reduction Technologies

Federal regulations allow states to adopt weight exemptions for auxiliary power units (APUs) or other qualified technologies that reduce fuel consumption and tailpipe emissions from engine idling. APUs are portable, vehicle-mounted systems that provide power for climate control and electrical devices without idling. For long-haul trucks, these systems typically have a small internal combustion engine (usually diesel) equipped with a generator to provide electricity and heat. Other on-board idle reduction technologies include automatic start-stop controls, energy recovery systems, fuel-operated heaters, coolant heaters, and battery-electric and thermal-storage air conditioners.

State Weight Exemptions

States may permit HDVs equipped with idle reduction technology to exceed the specified weight limit by up to 550 lbs to compensate for the additional weight of the equipment. The allowance was previously 400 lbs, but the federal Moving Ahead for Progress in the 21st Century (MAP-21) legislation, enacted in 2012, increased it to 550 lbs. States must enact a law or institute an enforcement policy with their own exemptions to reflect this increased weight allowance. A map of APU weight exemptions by state is available on the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) State Recognition of the Auxiliary Power Weight Exemption to Gross Vehicle Weight website ( Vehicle weight limit exemptions for APUs are also displayed in the table below. As the map and table show, many states have not updated their laws and enforcement policies to reflect the increase in the federal allowance to 550 lbs, which means the exemption is still limited to 400 lbs. There are also six states where the exemption is not permitted at all.

APU Weight Exemption


State Implementation

550 lbs

State Legislation


400 lbs

State Enforcement Policy


State Legislation



State Legislation


* West Virginia Code 17C-13A-4 refers to the U.S. Code directly for the exact weight.

States must require HDV drivers to demonstrate eligibility for vehicle weight limit exemptions. For example, drivers may need to have paperwork on hand that verifies the weight of the idle reduction equipment and be able to demonstrate that it is functional. Requirements are different from state to state.

More information on these state weight limit exemptions is also available on the Alternative Fuels Data Center (AFDC) Laws and Incentives database ( The Advanced Search options ( allow you to identify specific exemptions by location, technology/fuel type (idle reduction), incentive/regulation type (exemption), and user-type (vehicle owner or driver). Each description of a state idle reduction weight exemption includes a reference to the applicable legislation or policy.

Refer to the following for more information on idle reduction technologies and state vehicle weight limit exemptions for this equipment:


Clean Cities Technical Response Service Team

For specific weight formulas and information about grandfathered weights, see DOT’s website (

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DOE Announces Webinar on Biofuel Sustainability

Free Biofuels Webinar | April 22nd 

The Energy Department will present a live webinar titled "Biofuels for the Environment and Communities" on Wednesday, April 22, from 1:00 p.m. to 2:00 p.m. Eastern Daylight Time.

During this webinar, Drs. Virginia Dale from Oak Ridge National Laboratory and Christina Negri from Argonne National Laboratory will discuss their EERE-sponsored research on how to develop biofuels that positively impact the environmental, socioeconomic, and technoeconomic sustainability of biofuel development in the United States. 

Register for the webinar.

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