CALIFORNIA AIR RESOURCES BOARD
Auditorium, Room 1138
107 South Broadway
Los Angeles, CA
August 13, 1987
87-11-1 Consideration of Status Report on Clean Air
Act Issues of Concern to California.
87-11-2 Public Hearing to Consider Amendments to 001
Regulation Regarding the Degree of Unsaturation
of Gasoline Sold as Motor Vehicle Fuel in the
South Coast Air Basin.
87-11-3 Status Report on Efforts to Develop Clean Diesel 048
a. Closed Session
1. Personnel (as authorized by State Agency Open Meeting
Act, Govt. Code Sec. 11126(a).).
2. Litigation (Pursuant to the attorney-client privilege,
Evidence Code Sec. 950-962, and Govt. Code Sec.
b. Research Proposals
c. Delegations to Executive Officer
ITEM NO.: 87-11-2
Public Hearing to Consider Amendments to Regulation Regarding the
Degree of Unsaturation of Gasoline Sold as Motor Vehicle Fuel in
the South Coast Air Basin.
The staff recommends that the Board adopt and incorporate in
Section 2250, Title 13, California Administrative Code, and
updated version of the current test method for the bromine number
of gasoline with a provision explicitly stating that the method
applies to blends of gasoline containing ethanol, methanol, tert-butyl
alcohol (TBA), and methyl tert-butyl ether (MTBE). The
staff also recommends that the Board amend the regulation to
clarify the definition of gasoline.
Section 2250 limits the degree of unsaturation of gasoline sold
or supplied as a motor vehicle fuel in the South Coast Air Basin
(SCAB) to that indicated by a bromine number of 30. The bromine
number, a measure of the degree of unsaturation, is roughly two
times the olefin content of gasoline. The olefin content of
gasoline evaporative emissions is dependent on the olefin content
of the gasoline. Olefins generally react more rapidly than other
hydrocarbons. The regulation was adopted to place a cap on the
olefin content of gasoline to control the reactivity of gasoline-related
The method presently referenced in the regulation is ASTM D 1159-77.
The method states that it is not generally applicable to
gasoline with blending agents such as ethers, alcohols, ketones
or aminoes. Recent data from ARCO Chemical Company and from the
ARB Haagen-Smit Laboratory indicate that the bromine numbers, as
measured with ASTM test method D 1159-77, of blends of gasoline
with either methanol, ethanol, TBA or MTBE are not significantly
different than the bromine number of the base gasoline in the
SUMMARY AND IMPACTS OF PROPOSED BOARD ACTION
Adoption of the proposed test method would enhance enforcement of
the bromine number regulation with reference to the subject
blends. The proposed action is not expected to create
significant costs or savings to any public agency or private
ITEM NO.: 87-11-3
Status Report on Diesel Fuel and Its Effects on Emissions from
Diesel Motor Vehicles.
This is a status report. The staff is not making a
The Board's diesel vehicle emission control program.-The Air
Resources Board has had for a number of years a program to
control emissions from diesel vehicles. The Board has
established strict exhaust emission standards for diesel vehicles
and has adopted strict requirements for the sulfur content of
diesel fuel sold in the South Coast Air Basin. In addition to
these past actions, the Board has a continuing program to
investigate additional strategies to reduce further emissions
from diesel vehicles. Some of the elements of that program are
the evaluation of vehicular emission standards, hardware
retrofits, alternative fuels, and an inspection and maintenance
program. In addition to those control strategies, the evaluation
of modifications to conventional diesel fuel - the subject of
this report - is another element of the Board's diesel vehicle
emission reduction program.
Where we are now.-It is well known that diesel fuel quality
affects diesel engine emissions. However, the extent of the fuel
quality-emissions relationship has not been well established.
Results of studies that are to be completed in the near future
will allow the staff to evaluate more completely diesel fuel
modifications as a control strategy. The staff will then present
its findings for the Board's consideration.
What we know.-Based on limited data that are now available,
diesel motor vehicle emissions of particulate matter (soot) can
be reduced up to perhaps 50 percent by reducing the concentration
of aromatic hydrocarbons in the fuel. Aromatic hydrocarbons have
been identified as a major variable in the formation of soot
emissions from diesel engines. Fuel sulfur content also affects
diesel engine particulate emissions, but not the soot emissions.
Sulfur dioxide emissions, which result from sulfur in the fuel,
are converted to particulate matter in the atmosphere.
What we don't know.-The current state of knowledge regarding the
effects of fuel quality on diesel engine emissions is not
complete. Although it is known that aromatic hydrocarbons in the
fuel affect soot emissions, it is not known by how much they are
affected. Different studies have given different results. Also,
the effects of fuel quality on emissions of other pollutants are
less well known. Much of the data that are now available were
obtained on light-duty engines. Heavy-duty engines are the major
contributors to diesel vehicle emissions, and less is known about
the effects of fuel quality on these engines. Some studies have
given contradicting results. The cost to reduce emissions from
diesel vehicles is also uncertain.
Forthcoming additional emissions-fuel quality data.-There is a
major study now in progress that will provide a more certain
basis for evaluating the relationship between fuel quality and
diesel emissions. The study is being conducted on four heavy-duty diesel
engines - the engines that are the source of most
diesel emissions. This study, sponsored by the Coordinating
Research Council (CRC) with ARB participation, will also provide
information on the relationship, if any, between diesel fuel
composition and benzene emissions.
Forthcoming additional cost data.-Another area of uncertainty is
the cost of modifying diesel fuel properties. The staff has made
some cost estimates based on a three-year old survey of
California oil refiners. To obtain a more complete cost
estimate, the ARB has contracted with A.D. Little to perform a
linear programming study of California refineries to obtain an
independent cost estimate of various changes to motor vehicle
diesel fuel specifications.
Our Schedule.-When the additional data on cost and the data on
the fuel quality-emissions relationship are available, the staff
will present its findings to the Board in a formal report. The
cost study information is scheduled to be available in January
1988, and the fuel quality-emissions data are scheduled to be
available in the second quarter of 1988. The staff has planned
for workshops on the various issues related to fuel modification.
A workshop is scheduled for the fall of 1987, and others are
planned to be held following the availability of the emissions
and cost study data. Staff regulatory proposals, if justified,
can be heard by the Board six months after receipt of the results
of the CRC study on fuel quality and emissions.