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TxLED Looms: Texas Low Emissions Diesel Rule Comes into Effect 1 Oct 05

12 August 2005

110 Texas counties affected by TxLED

The Texas Low Emissions Diesel (TxLED) requirements are designed to lower the emissions of NOx and other pollutants from diesel-powered vehicles and non-road equipment in 110 counties in the eastern half of Texas as part of the State Implementation Plan to address non-compliance with federal ozone standards.

Under the rule, diesel supplied in those 110 counties must comply with the more stringent California Air Resources Board specifications for diesel fuel (e.g., 10% or less total aromatic hydrocarbon content; a cetane number of at least 48, a maximum 15-ppm sulfur content).

Originally adopted in 2000, the rule was due for implementation in April 2005. That was changed to the current 1 October 2005 implementation date.

The law first applies to producers and importers; bulk plant distribution facilities have until November, and retail fuel dispensing outlets, wholesale bulk purchaser/consumer facilities, and all other affected persons until 1 January 2006.

Biodiesel is not by default an approved solution for TxLED, either as an additive or neat (B100).

The executive director of the TCEQ has determined that blending biodiesel into Texas Low Emission Diesel (TxLED) is not acceptable unless the blend has been approved by TCEQ as being equivalent to TxLED in reducing NOx emissions.

Pure biodiesel (B100) and other biodiesel blends such as B20 are known to be effective in reducing emissions of carbon monoxide, total hydrocarbons, and particulate. The U.S. Environmental Protection Agency (EPA) has verified the use of biodiesel as a retrofit technology to reduce these specific emissions.

However, the use of B100 in compression-ignition engines is also known to increase NOx emissions by at least 10 percent and by 2 percent or more with B20 blends.

This increase in NOx emissions is acknowledged by industry groups, the EPA, the California Air Resources Board (CARB), and the National Biodiesel Board. In fact, because of the known increase in NOx emissions, the Engine Manufacturers Association (EMA) does not recommend the use of B100 or biodiesel blends as a means to improve air quality in ozone non-attainment areas. (TxLED FAQ)

The TCEQ will accept the use of biodiesel on a case-by-case basis if the blend can demonstrate that is has been verified by EPA or CARB to reduce NOx emissions by a percentage that is equivalent to or greater than the NOx reduction of at least 5.7 percent attributed to TxLED when blended with regular EPA diesel; or it has been approved by the executive director as an TxLED alternative diesel formulation.

An alternative diesel formulation is one that either meets the emissions target without specifically meeting the fuel characteristics as specified by TxLED, or that is produced through blending with an approved additive.

So far, only two additives have been approved: Lubrizol PuriNOx and, most recently, Biofriendly Green Plus.

Green Plus is a fuel catalyst. Mixed into diesel in concentrations of 50 ppm or less, the additive promotes a more complete, and lower-temperature combustion, resulting in reduced emissions and an improvement in fuel economy, according to their testing results, of some 6%–9%.

Lubrizol takes a different approach, blending a diesel-water-PuriNOx emulsion. The water in the emulsion promotes a finer, more even spray and combustion at a lower temperature, and the PuriNOx additive keeps the diesel-water mixture stable.


August 12, 2005 in Biodiesel, Diesel, Emissions, Policy | Permalink | Comments (8) | TrackBack (0)


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How were these 110 counties chosen? Is there any chance of the number increasing or decreasing in the next 10 years?

These counties make up the non-attainment area because they exceeded the ozone limits too often. The ozone is created when N2O3 is split by sunlight into a nitrogen molecule and an ozone molecule. No NOx no ozone.
There is a zirconium based ceramic which absorbs oxygen on one side and releases oxygen on the other when an electric charge is placed across it. This would make it the ultimate air filter because no nitrogen would get into the cylinders. No nitrogen, no NOx, no ozone.

So the thing is, those 110 counties include urban, suburban, and rural areas. How is it that those contiguous 110 all required the extra regulation, but none of the other TX counties did?

Basically, it’s guilt by proximity. :-)

There are specific areas in the state that are in non-attainment of the ozone requirements. To devise a remediation plan, the state used photochemical grid modeling for ozone nonattainment areas designated serious, severe, or extreme, as required by federal law.

Hundreds of emission control strategies were considered in developing the modeling. Varying degrees of reductions from point sources and mobile sources were analyzed in at least forty modeling iterations, to test the effectiveness of different NOx reductions.

The attainment demonstration modeling submitted for public hearing and comment concurrently with these rules shows that, in order for DFW to achieve the ozone NAAQS by 2007, almost all of the practicably achievable NOx reductions are necessary from each emission source category, including reductions from counties surrounding the DFW nonattainment area. (Rule Log Number 1999-055A-114-AI, Texas SIP here)

A DOE study completed in May 2005 casts considerable doubt on the effectiveness of NOx reductions absent other significant reductions in the other ozone precursors (VOCs and CO). This report shows that Houston (along with several other large cities across the CONUS) experience the "weekend ozone effect" where ozone levels actually increased on weekends (or at least didn't decrease) in spite of very large reductions in NOx emissions on weekends (and to a lesser extent reductions of the other ozone precursors). NOx reductions of >60% were measured on weekends.

By the way, NO2 is actually the ozone precursor species of NOx. NO2 photo-dissociates into NO + O (atomic oxygen). The O combines with O2 (molecular oxygen) to for ozone (O3). NO (nitric oxide) is the other species of NOx (diesel NOx emissions are about 90% NO) and actually DEPLETES ozone because the reverse reaction occurs nearly as fast as the ozone is formed. It's VOCs (and to some extent CO) which convert NO into NO2 thus making more NO2 available to create ozone and less NO available to destroy it.

Interesting. Do you have a pointer to the study? Thanks!


Some conclusions drawn in the report:

"…NOx concentration reductions on Sundays exceeded the Sunday reductions of CO and hydrocarbon concentrations in all cities that were studied…" (page 101)

"…all areas exhibited ozone concentration increases for data averaged over the period 10 am through 5 pm, with median Sunday ozone levels ranging from 100 to 115 percent of the Wednesday concentrations…" (page 104)

"…none of the metropolitan study areas exhibited significant reductions of weekend ozone levels, nor were significant ozone decreases observed downwind of the study areas on weekends...." (page 118)

The weekend effect has been studied quite extensively in California. See for example, ,,filter.all/pub_detail.asp , .

I want to know if the nonattainment condition in Port Arthur and Beaumont Texas has gotten any better.

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