Soil Emissions from field scale methyl bromide fumigations can be removed by venting the emissions from under impermeable films to a portable scrubber. In this example, methyl bromide has been "broadcast" into the soil and covered with a tarp.
Value Recovery has demonstrated this approach to scrubbing methyhl bromide on a small scale in a USDA sponsored research project (SBIR # 2005-33610-15474) where it was shown in a model system (4ft long and 1 ft diameter) that the desorption rate of methyl bromide from the soil governs the overall time it takes to come to complete removal. A tarp was spread over farmland in New Jersey and fumigant air from under the tarp was removed in a controlled manner without collapsing the tarp. The air withdrawal rate was great enough to remove the methyl bromide yet slow enough to prevent collapse of the tarp since provision was made for make up air to enter the tarp on the opposite end from where it was withdrawn.
Below are US government statistical data showing methyl bromide use for major Critical Use Exemption categories for the last 4 years that data are available. With the possible exception of Bell Peppers, the numbers show that the overall use of methyl bromide in soil applications use is not going down in the US and have remained constant. Thus, claims that "methyl bromide is being phased out" are without merit.
Source:
Thousands of Pounds of Methyl Bromide Applied to Soil in the U.S.
| |
2002 |
2004 |
2006 |
| |
|
|
|
| Cucumbers-Fresh |
689 |
156 |
691 |
| Melons-Watermelons-All |
365 |
523 |
259 |
| Peppers-Bell-All |
2,470 |
2,187 |
1,129 |
| Squash-All |
49 |
35 |
258 |
| Strawberries-All |
4,263 |
2,709 |
3,640 |
| Tomatoes-Fresh |
5,621 |
6,457 |
5,643 |
| |
|
|
|
| Totals |
13,457 |
12,067 |
11,619 |
| |
|
|
|
| (total minus peppers) |
10,987 |
9,880 |
10,490 |
Thus over ten million lbs per year of methyl bromide are still applied to soils in the US under the Critical Use Exemption program and with the exception of the small amount that reacts in the soil, all of it winds up in the upper atmosphere destroying the ozone layer.
Since alternatives have not diminished the use of methyl bromide on soils, as shown in the above data, then controlling emissions on a post-application basis makes logical sense. Further, emissions controls will protect the ozone layer and thus further the objectives of the Montreal Protocol.
Quarantine and Pre-shipment
Small Chamber Fumigation
Portable Scrubber System
Anthrax Fumigation
Reactive Separations
