Methyl bromide, an effective soil fumigant, has been identified as one of the worst depleters of the ozone layer. Methyl bromides strong suit, its reactivity, is also its Achilles heel. Over 80% of methyl bromide used in 1990 was used for soil fumigation and this application has been targeted directly for elimination. Consequently, the Montreal Protocol (1987) signed by 187 countries, outlawed the use of methyl bromide in the US by 2005. Suitable substitutes for many applications have not been found and the scientific consensus is that substitutes for some applications may never be found. Thus, many millions of pounds of methyl bromide will continue to be vented into the atmosphere. Value Recovery has technology to capture and destroy, or 'scrub', methyl bromide economically from dilute air streams. The technology takes advantage of methyl bromide's reactivity and uses this as a separation strategy by reacting and thus converting methyl bromide into harmless byproducts. Our Phase I proposal is meant to develop the technology and fit it economically to soil fumigation applications. We wish to develop a method based on a soil cylinder model to instantaneously and economically capture and destroy from 95 to 99% of fugitive methyl bromide emissions from soil fumigations. OBJECTIVES: 1.To demonstrate 99% removal levels of methyl bromide from air streams (instantaneous capture and destroy technology) using readily available and cheap non-hazardous scrubbing liquor. 2.To quantify methyl bromide adsorption and desorption in soil during novelfumigation operations and establish the practical use levels of methyl bromide needed in novel soil fumigation system. 3. To provide an economic estimate of the capital and operating costs for the instantaneous capture and destroy fumigation system as applied to an in-situ field application. Objective No. 1, demonstration of 99% removal of methyl bromide in air streams, is meant to complete and round out our previous work. Ammonium thiosulfate has been proposed [8] in California as a reactant spread on farmland to consume residual methyl bromide in the soil. In Objective 2 we will quantify what the amounts of methyl bromide are within the soil during and after fumigation IN A CLOSED SYSTEM and find a threshold minimum amount needed to destroy nematodes of interest. We will do this by building a soil chamber that is 130 cm long and 30 cm in diameter made up from teflon line pipe fitted with socket weld endcaps. To obtain a loading of 400 lbs/acre we would add 3.24 grams (200 cc) of methyl bromide to this apparatus at the radial center at 30 cm below the soil surface. The efficacy of soil fumigation will be verified using lesion (or pine wilt) nematodes as a bio-indicator. Populations of lesion nematodes will be maintained on rye under greenhouse conditions and extracted from roots using a mist chamber or shaker technique as needed for each experiment. Nematode mortality from fumigated soil will be compared with the numbers recovered from untreated checks. At the conclusion of a fumigation experiment we will desorb the methyl bromide by sweeping air across the surface (through the headspace) at a known flowrate (making sure to humidify the air to keep the soil from drying out) and monitor desorption from the IR cells. This data is needed to predict the following: a. How much of the methyl bromide will partition to the headspace under a tarp after 48 hours? Would decreasing the volume of the headspace under the tarp lead to significantly less methyl bromide being used and needlessly wasted? b. How much is adsorbed in the soil and how much is in the gas phase in contact with the soil in the headspace at equilibrium. This question is not addressed [Jin] in a study looking at losses of methyl bromide through thin polyethylene tarps. c. If we sweep air across the surface after fumigation and under the tarp enclosure, how long will it take to desorb the methyl bromide from the soil into a scrubber system? Will this rate be slower than published desorption times? We will determine what air ventilation rates are needed and the methyl bromide concentrations that result via comparison of actual data to a math model. In Objective 3, we intend to put the data together and make an estimate of what a scrubber system would cost by obtaining a budget grade capital and operating cost for the scrubbing system. APPROACH: All experimental work using methyl bromide will be performed in the walk-in hood at Value Recovery, Inc. in Bridgeport, New Jersey. Maintenance of nematode cultures, putting them into permeable pouches and the analysis of nematode viability will be done at the Penn State Fruit Research and Extension Center in Biglerville, PA under the direction of Dr. John Halbrendt. Since the nematodes can remain viable in soil in the absence of food for extended periods of time and even longer up to several weeks if kept refrigerated, there should be no problem shipping insulated packets of nematodes back and forth between labs for testing and subsequent evaluation. Alternatively, Biglerville is approximately 150 miles by car from Bridgeport and direct transport of the samples is an other option if need be. The scrubber apparatus is already built and operating. In Objective 2, we assemble the soil chamber apparatus that consists of a 30 cm diameter tube and two soil sections. Above methyl bromide injection point is 30 cm and below it is 90 cm of soil. Letter j (of the plan) begins the experimentation with nematodes in the chamber with low concentrations of methyl bromide. Each experiment will have a charge of 3 samples of nematodes that are put into a permeable pouch made of 30 micron nylon mesh and containing 25 cc of soil. The first two experiments will be nematodes exposed to 0.8 and 3.2 grams of methyl bromide in the soil cylinder which corresponds to 100 and 400 lbs/acre respectively (1.1 and 4.4 x 10-5 g/cm2) inclusive. Next we will begin the soil desorption experiments and obtain the equilibrium concentration of methyl bromide in the gas phase within the soil. As air is swept over the top of the soil we will be able to measure the desorption phenomena occurring within the soil. Very high air rates, 125 cc/min, would give a turnover of the headspace in 15 minutes (volume = 1.9 liters) indicative of a removed tarp or soil exposed to the open air while a low air sweep rate, 8 cc/min, would give twelve turnovers in 48 hours that would match up with our desired scrubber sizing for a commercial installation. Thus operating at these two extremes bracket the soil desorption phenomena. In objective 3 we will put the pieces together and estimate the capital and operating costs for a commercial scale scrubber system based on 25 acres of fumigated land
