CALIFORNIA AIR RESOURCES BOARD
Auditorium, First Floor
400 "P" Street
June 9, 1988
88-8-1 Status Report on Benzene Control 001
88-8-2 Public Meeting to Consider Approval of a 003
Procedure Relating to the Determination of
Agricultural/Forestry Emission Offset Credits
(AB 2158, Condit, 1987)
88-8-3 Public Meeting to Consider a Report to the 128
Legislature on the Landfill Gas Testing Program
88-8-4 Status Report on Modeling Center
88-8-5 Establishment of Modeling Advisory Committee and
Appointment of Committee Members
a. Closed Session
Personnel (as authorized by State Agency Open Meeting Act,
Govt. Code Sec. 11126(a).)
b. Research proposals
c. Delegations to Executive Officer
ITEM NO. 88-8-1
Status Report on Benzene Control.
In 1986, the Board approved the Benzene Control Plan, which
contains three primary elements for reducing benzene emissions.
These elements are:
1. requiring new vehicular controls for hydrocarbon
emissions (which include benzene),
2. adopting and emission standard for benzene from new
light-duty vehicles, and
3. regulating the composition of motor gasoline.
This report is an update on the benzene control plan and relates
the staff's progress and schedule for presenting proposals to the
Board for control measures that correspond to these plan
elements. No control measures are proposed in this report, and
no action by the Board is required.
Emissions and Cancer Risk
Emissions of benzene in the state have decreased by half since
1965 as the result of emission controls on vehicles, vapor
recovery at service stations, and other hydrocarbon control
measures. We expect this downward trend to continue until the
year 2000. Benzene emissions are then projected to begin
increasing as more miles are driven and more fuel is used, unless
new controls reducing benzene or hydrocarbons containing benzene
are adopted. In 2000, about 60 percent of the projected benzene
emissions of 38 tons per day will be from on-road vehicles
(mostly from gasoline-powered vehicles), with 30 percent from
off-road vehicles and 10 percent from stationary sources.
Because gasoline use is the major source of benzene emission and
because gasoline is used everywhere in the state, all persons are
exposed to some level of risk. At the year 2000 emission rate,
the potential statewide cancer incidence due to benzene exposure
is estimated to be 1,450 to 11,400 cases over a 70-year period.
The maximum individual risk due to benzene exposure in the south
Coast Air Basin is about 100 to 800 potential cases per million
Planned Control Measures
Over the next several years, the staff will propose a series of
new control measures for hydrocarbon emissions from vehicles.
The first proposal, scheduled to be brought to the Board in
November 1988, will be to limit hydrocarbon emissions from new
light-duty vehicles to 0.25 gram per mile. (The current standard
is 0.41 gram per mile.) In later years, proposals will be made
for improvements in the motor vehicle Inspection and Maintenance
(I/M) program and for additional measures to eliminate excess
These vehicular control measures are being developed principally
to reduce hydrocarbon emissions. Substantial reductions of
benzene emissions would also result from the measures, however.
Adopting all of the staff's planned vehicular measures would
reduce the total lifetime cancer indecence due to benzene
exposure in the year 2000 by about 18 percent.
In November 1988, we will also propose a statewide regulation
limiting the benzene content of gasoline. The limit will reduce
the average benzene content from its current level of
approximately 1.9 volume percent to a level (not yet determined)
that is between 0.6 and 1.2 volume percent. This measure would
reduce potential cancer incidence due to benzene exposure in the
year 2000 by an additional 13 to 24 percent.
Potential Additional Measures
The ARB is also sponsoring some research on the feasibilities of
(1) restricting the content of other benzene-like aromatic
compounds in gasoline, which partially convert to benzene in the
engine or catalyst, and (2) modifying vehicular emission control
systems to meet an exhaust benzene standard. The benefits and
costs of these potential measures are currently unknown.
Limiting the aromatic content of gasoline, however, is estimated
to cost much more per potential cancer case avoided (perhaps 5
times as much) than limiting the benzene content of gasoline.
Another means of reducing benzene emissions over the long term is
to substitute alternative fuels for gasoline. The staff is
currently investigating the feasibility of promoting greater use
of methanol-powered and electric-powered vehicles.
Benzene emissions have declined significantly over the past two
decades due to the ARB's various emission control programs. A
number of additional control measures are being developed and, if
adopted by the Board, will result in further decreases in benzene
emissions. The cancer risk remaining even after full
implementation of all currently planned measures is, in the
staff's view, still large. Therefore, we will continue to study
the feasibility of additional measures.
ITEM NO. 88-8-2
Public meeting to consider approval of A Procedure Relating to
the Determination of Agricultural/Forestry Emission Offset
Credits (AB 2158, Condit. 1987).
Approve the amended procedure and recommend that districts
incorporate this procedure into their New Source Review programs.
Background: Previous Legislation
In 1983 legislation was enacted (AB 1223) which required
districts to include the incremental emission benefits of
reducing open field burning in considering the offset
requirements for projects which use agricultural and forest waste
products as fuel to generate steam or electricity. These
benefits are based on the emission reductions which will result
because these wastes are no longer disposed of by open field
Under this law, the ARB and the districts were directed to
develop, in cooperation, a procedure to determine the magnitude
of emission credits available to facilities which burn
agricultural or forest wastes for the production of steam or
electricity. This procedure was presented in the 1984 ARB report
"A Procedure to Implement the provisions of Health and Safety
Code Section 41605.5 (AB 1223: Relating to the Determination of
Agricultural/Forestry Emission Offset Credits", which was
approved by the Board in June of 1984.
In its current form, the document is a procedure for the
Calculation of agricultural/forestry emission offsets (Ag
offsets). The procedure contains recommendations and suggestions
regarding applicability, requirements for obtaining emission
offset credits, emission offset calculations, enforcement
considerations, interpollutant offset credits, and an accounting
mechanism for agricultural/forestry waste offset credits. Air
pollution control districts and air quality management districts
use the procedure as part of the process for deciding whether to
authorize the construction of projects that burn agricultural or
forest waste (biomass).
In 1987 AB 2158 was passed. This law amended the requirements of
Section 41605.5. AB 2158 required the districts and the Board,
in cooperation to develop by July 1, 1988, a procedure to
determine the magnitude of offset credits available to facilities
which propose to use agricultural, forestry, or similar wastes as
fuel in a boiler to produce steam or electricity, or to be used
as a feedstock in a digester which will produce animal feed at a
cogeneration facility. The districts and the ARB are also
required to re-evaluate the procedure every two years.
The staff, in cooperation with a committee comprised of
representatives from the California Air Pollution Control
Officers Association (CAPCOA), the U.S. EPA Region IX, and Board
staff, has modified the existing procedure. The proposed
procedure is an amended version of the existing procedure.
A draft of the amended procedure developed by the committee was
released for public review and comment on February 26, 1988 and a
public consultation meeting was held on March 16, 1988. As a
result of its own work and the comments received on the draft
procedure, the committee proposes the following specific changes
to update the 1984 procedure:
* Define "digester feedstock in a cogeneration facility" and
incorporate methods of determining the appropriate emission
* Clarify emission factors for use in offset calculation;
* Update the list of crops which are normally open field
* Update the recommended permit conditions to strengthen
districts' abilities to assure enforceability and permanence
of emission reductions used for emission offset credits; and
* Base emission reduction credits on the percentage of biomass
historically open burned.
The committee in its draft procedure initially proposed changes
that addressed the seasonal nature of the emission reductions
associated with the elimination of open field burning. The
committee proposed that the offsets be credited to a new source
only in the months the emission reductions would occur from the
elimination of field burning. Participants at the public
consultation meeting questioned whether open field burning takes
place in each month of the year, and emphasized that the proposal
would therefore unduly limit the ability to site new biomass
Because of the need for additional documentation on the seasonal
nature of open field burning, the committee will continue to
evaluate the impact of this aspect of these emission reductions.
If the committee determines as a result that the procedure should
be modified, the committee will return to the Board with its
recommended changes to the procedure.
ITEM NO. 88-8-3
Public Meeting to Discuss "The Landfill Gas Testing Program: A
Report to the Legislature".
The staff recommends that the Board approve the report for
transmittal to the Legislature.
This is a report on the status of the statewide landfill gas
testing program being conducted pursuant to AB 3374 (Calderon,
Under the testi