United States Air and Energy Engineering

Environmental Protection Research Laboratory

Agency Research Triangle Park, NC 27711

Research and Development EPA/600/SR-94/126 November 1994

E AP Project Summary

Evaluation of Containment and

Control Options for Methyl

Bromide in Commodity

Treatment

Methyl bromide (MeBr) is an ozonedepleting chemical scheduled to be

phased out by The Clean Air Act by the

year 2001. For agricultural commodity

fumigation, there is no ready substitute for MeBr. This study was undertaken to investigate means for MeBr

recovery, reuse, and destruction to prevent atmospheric emissions if its limited use were still allowed.

Approximately 4 - 5 million lb/yr

(1.8 - 2.3 million kg/yr) of MeBr is

used for commodity/agricultural

harvest fumigation. Commodity fumigation is carried out extensively at a

few locations, mostly major seaports.

Fumigation is conducted in chambers

built for holding the commodity during

fumigation and in temporary enclosure,

such as under tarpaulins and in vehicles. The emissions are vented to the

atmosphere.

Few control systems exist for MeBr

emissions. Likewise, control system

research and development has been

limited. Vendors have proposed control technologies for MeBr control, recovery, and recycle, but few systems

have been built. Conventional vapor

control technologies, such as activated

carbon adsorption systems, appear to

be applicable to MeBr emissions. These

systems must also provide for recovery. Control will probably be expensive

due to the small volumes of recoverable material and the intermittent nature of fumigation operations.

This Project Summary was developed

by EPA’s Air and Energy Engineering

Research Laboratory, Research Triangle Park, NC, to announce key findings of the research project that is fully

documented in a separate report of the

same title (see Project Report ordering

information at back).

Introduction

Methyl bromide (MeBr), with the

chemical formula CH3Br, also called

bromomethane, is listed by the 1991

Montreal Protocol as an ozone depleting chemical similar to the other halogenated hydrocarbons such as the

chlorofluorocarbons (CFCs). The U.S.

Environmental Protection Agency's (EPA's)

regulations authorized by the Clean Air

Act (CAA) call for a phaseout of MeBr

production by the year 2001. This would

mean an end to uses of MeBr where the

material is emitted to the atmosphere since

no future supply of MeBr would be available. In some applications, there is no

apparent, ready substitute for MeBr. Therefore, this study was undertaken to investigate possible means for MeBr recovery

for reuse and for MeBr destruction to prevent atmospheric emissions if its limited

use were still allowed.

MeBr is widely used in U.S. agriculture

as a fumigant. A fumigant is a material

that can exist as a gas in a concentration

lethal to a pest organism. As a gas, it can

penetrate the material being fumigated,

and then diffuse away after the fumigation

ends. MeBr is a very useful general fumigant since it is a permeating gas at ambient temperatures and pressures and since

it has a very desirable toxicity to many

pest populations.

Table 1 shows that the primary use of

MeBr is in soil fumigation, where it is used

to kill nematodes and soil insects prior to

Glenn B. DeWolf and Matthew R. Harrison
2

planting. According to Chemical Products

Synopsis (CPS), approximately 75% of

the 47 million lb (21 million kg) of MeBr

consumed in 1991 in the U.S. was for this

application. An additional 8% of MeBr consumption is as a chemical intermediate or

as a solvent. The remaining 16% of MeBr

consumption is used in space fumigation.

Half of that space fumigation is structural

fumigation, and half is for commodity fumigation.

The National Agricultural Pesticide Impact Assessment Program (NAPIAP) of

the U.S. Department of Agriculture (USDA)

has produced use numbers for MeBr that

are different from the CPS numbers. However, both sources show that approximately 4 - 5 million lb/yr (1.8 - 2.3 million

kg/yr) of MeBr is used for commodity/

agricultural harvest space fumigation.

This study has gathered preliminary data

that can be used to determine if some of

the essential agricultural commodity fumigation applications of MeBr could be continued by the use of some emission control

methods on those commodity fumigation

applications.

Conclusions

MeBr Uses and Quantities

Since MeBr uses are relatively restricted,

MeBr can be viewed as a specialty fumigant. The consumption of MeBr for space

fumigation of commodities represents

about 8% of MeBr use. The primary use

for MeBr in commodity fumigation is for

fruits and nuts. In the treatment of these

commodities, there are general commodity containment schemes that are common throughout the industry, although

some details may vary with individual installations. The types of configurations for

commodity containment are relatively limited.

Fumigation is carried out extensively at

a few primary locations, mostly major seaports. Two of the largest ports where MeBr

is used are San Diego and Philadelphia.

Other major ports include Seattle and Miami, but any port where fruit and nuts are

imported is a candidate. Also, fumigation

facilities are reported to be present at

some airports and military facilities.

Emission Source

Characteristics

Emissions sources are characterized in

terms of physical configuration and emission stream characteristics.

Physical configurations are divided into

two categories: (1) sources with a duct,

pipe, or stack outlet, and (2) sources with

multiple, irregular outlets. The former occur in chambers specifically built for holding the commodity during fumigation. The

latter occur with tarpaulin fumigation or

fumigation in vehicles where ordinary leakage or simply an open door is used to

vent the MeBr when fumigation is complete.

 The emissions arise when air is blown

through the commodity to remove the

MeBr. Currently the emissions are vented

directly to the atmosphere.

Little data are currently available for

stream characteristics. Information that is

available suggests flow rates in the range

of no more than a few thousand to a few

tens of thousand of cubic feet per minute

air flow with a MeBr content ranging from

a few hundred to a few thousand parts

per million.

Currently few control systems exist for

MeBr emissions. Likewise, research and

development related to control system design has been extremely limited.

Various vendors have proposed control

technologies for MeBr control, recovery,

and recycle. Few systems have been built.

Currently, systems are being investigated

and the Port of San Diego is installing a

MeBr treatment system. Some systems

have been installed overseas. Technical

details of these systems are not readily

available, so that further work would be

required to determine how extensively they

control emissions and how effective they

may be at recovery.

In general, conventional vapor control

technologies, such as activated carbon

adsorption systems, appear to be applicable to MeBr emissions. However, in the

context of minimum or even zero emissions, depending on the regulatory scenario, control systems must also provide

for recovery. Conventional approaches

using condensation and other methods

appear to be applicable here. The fundamental technologies required appear to

exist, but the specifics of the application

of these technologies to the MeBr control

issue require much more investigation and

design data acquisition.

Process Economics

Process economics of MeBr control and

recovery are not well defined. Scattered

data on actual and possible costs of systems were skimpy. Because many components of a control system would appear

to rely on existing technologies, costs and

the corresponding economics do not appear to be difficult to estimate. Costs can

be expected to be comparable to those of

other vapor control systems for similar

gas stream flow rates.

Preliminary economics of a conceptual

design prepared specifically for this report

indicate that control will be relatively expensive. The relative expense compared

with control systems of similar nature in

other applications is based on relatively

small volumes of recoverable material that

would be handled and the intermittent nature of many of the fumigation operations

to which the control system would be applied. At this time, sufficient data are not

available for either design or costs to make

a definitive statement.

 A factor that might considerably influence the economics of MeBr control is the

availability of future MeBr supplies. This

will be influenced by the regulatory scenario. A total ban, but allowance of the

use of existing MeBr inventories with recycle would, in effect, make recycle impractical for technical reasons. Chemical

reaction losses would quickly deplete the

supply. On the other hand, a selective

ban that would allow some manufacture

of MeBr to continue might drive up the

price, assuming a manufacturer were willing to continue manufacture, because the

use volume would be sharply reduced.

Unit manufacturing costs would increase

sharply.

Current Research and

Development Activities

Current research and development activities appear to be underway in several

quarters on the very issues discussed in

this report. These activities do appear to

Table 1. Methyl Bromide Use [million lb/yr (million kg/yr)]

1991 Use from CPS 1990 Use from NAPIAP

Total 47 (21) 64 (29)

Soil Fumigation 35 (16) 47 (21)

Chemical Intermediate 3.8 (1.7)

Structural Space Fumigation 3.8 (1.7) 4 to 9 (1.8 to 4.1)

Commodity Space Fumigation 3.8 (1.7) 5 (2.3)
3

be limited at the present time, however.

Much of the current work appears to be

under the auspices of various vendors of

systems and equipment. Some government agencies and industrial groups are

showing increasing interest in funding

some research. The United Nations Environment Programme (UNEP) has had a

leading role in addressing some of these

issues.

Information Gaps

In general, information is lacking in two

fundamental categories: (1) MeBr emission source characterization and (2) control technology characterization. The

fundamental focus needs to shift beyond

mere reduction of emissions and toward

recovery and recycle. There also needs to

be an effort to gather some fundamental

performance data related specifically to

fundamental stream characteristics. This

is especially important because of the reported potential for the accumulation of

various commodity chemical components

picked up by the MeBr on each cycle of

contact with the commodity being fumigated. Detailed economic evaluations

based on existing data should be carried

out early in order to better direct the research and maximize research efficiency.
4

G. DeWolf and M. Harrison are with Radian Corp., Austin, TX 78720-1088.

Robert V. Hendriks is the EPA Project Officer (see below).

The complete report, entitled “Evaluation of Containment and Control Options for

Methyl Bromide in Commodity Treatment,” (Order No. PB94-195070; Cost:

$27.00, subject to change) will be available only from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: 703-487-4650

The EPA Project Officer can be contacted at:

Air and Energy Engineering Research Laboratory

U.S. Environmental Protection Agency

Cincinnati, OH 45268

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

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