Response to an additional information request from the EPA Response to an additional information request from the EPA Response to an additional information request from the EPA Response to an additional information request from the EPA
28 June 2019 28 June 201928 June 2019
28 June 2019
STIMBR lodged an application with the EPA on Friday 22 March 2019 seeking a modified
reassessment of methyl bromide that focused on addressing specific controls that the EPA (then ERMA) put into their 2010 methyl bromide reassessment decision. The EPA wrote a letter of receipt to STIMBR dated 15 April 2019 (received by STIMBR on 17 April) to confirm that a publicly-notified modified reassessment would be undertaken, and to request additional information from STIMBR.
The additional information that the EPA requested is documented below in bold text. STIMBR worked with subject matter experts, including Dr Jack Armstrong, a quarantine and phytosanitary treatment specialist with close to 40 years of research experience with the United States
Department of Agriculture and 13 years in New Zealand, the New Zealand Plant Market Access Council, horticulture sectors and United Fresh on behalf of the Fresh Produce importers.
This document was prepared in response to the information requested by the EPA.
STIMBR’S RESPONSE TO THE REQUEST FOR ADDITIONAL INFORMATION
Additional information request from the EPA
1. Is the proposed 80% recapture control based on each individual fumigation, the
cumulative recovery at a particular site, or the cumulative recovery for all quarantine and pre-shipment uses in New Zealand? Clarity over the scale over which the proposed recapture rate extends is important for the impacts of the proposed change to be understood.
We are proposing 80% recapture of the methyl bromide that remains in the headspace at the end of fumigation for each, individual log stack and produce fumigation under tarpaulin that takes place in New Zealand.
The operational sequence to accomplish the 80% recapture rate is:
(1) the concentration of methyl bromide remaining in the headspace at the end of each log stack and produce fumigation under tarpaulin is measured;
(2) a methyl bromide recapture technology is applied to each log stack or produce fumigation under tarpaulin; and
(3) the tarpaulins are removed when the measured concentration of methyl bromide that was measured at the end of the fumigation has been reduced to 20% (i.e., an 80%
We propose that a set of performance and reporting measures be implemented as follows:
1. Recapture technologies must be applied in every instance where container and sheet (tarpaulin) fumigations using methyl bromide occur.
What is to be reported
• Commodity being fumigated
• Treatment rate /m3 (e.g., 1.5 kg methyl bromide / 1,000 m3)
• Total volume of fumigation in /m3 (e.g., 1,000 m3)
• Weight methyl bromide applied in kg
• Duration of fumigation
• Concentration (in ppm and g/m3) of methyl bromide present in the head space at 30 minutes after the fumigation begins (i.e., after the methyl bromide has been released under the tarpaulin or in the container)
• Concentration (in ppm and g/m3) of methyl bromide present in the head space at the end of the fumigation duration
• Duration (i.e., beginning and end times) of methyl bromide recapture
• Concentration (in ppm and g/m3) of methyl bromide present in the head space at the end of recapture process
2. Fumigation service providers will aggregate individual sheet (tarpaulin) fumigations to determine the average level of recapture achieved on a monthly and annual basis. The annual (calendar) average for the preceding 12 months is to be reported and must be no less than 80% of the available gas in the headspace for every completed fumigation using the records for every individual fumigation (see “What is to be reported” above).
3. All container and sheet (tarpaulin) fumigations are to be maintained and reported as separate records with the information described in “What is to be reported” section above.
4. In-hold fumigation is exempt from these measures until 2030 while industry continues to look for solutions.
What is to be reported: The industry will report semi-annually to the EPA on progress towards the development of a solution to the recapture of methyl bromide from ship holds at the end of fumigation.
2. Information on internationally available recapture technologies is requested. The application claims that current technologies cannot meet the 5-ppm requirement in the current definition of recapture. Further evidence is required to support this claim.
Dr Jack Armstrong completed a comprehensive review of the methyl bromide destruction and recapture technologies for STIMBR in 2017. In response to the request for additional information from the EPA STIMBR engaged Dr Armstrong to review and update the report. The report follows.
Revised Review of Proposed Concepts and Technologies to Recapture and/or Destroy Residual Methyl Bromide (MB) after Log Fumigations at New Zealand Ports
A Report Prepared for Stakeholders in Methyl Bromide Reduction Originally submitted 02 September 2017
Revised/updated version submitted 18 June 2019
Jack Armstrong, PhD
Quarantine Treatments and Market Access Specialist Quarantine Scientific Limited
Kerikeri, New Zealand
This review version, updated 20 June 2019, provides additional information and current status for MB recapture and destruction technologies (MBRDT) with specific reference to progress and issues in meeting the 2020 recapture requirements that occurred since the original review submitted to STIMBR 01 October 2017. The purpose of the review is to inform the STIMBR Board on their potential use by the New Zealand log export industry to meet the Environmental Protection Authority MB recapture and destruction goals by 1 October 2020.
The review found that neither electric arc (plasma) technology or ozone were applicable as MBRDT, and that MBRDT that use activated carbon (AC, a solid MB sorbant) or ammonium thiosulfate (a reactive liquid sorbant that destroys MB) or a combination of both were cost prohibitive or not amenable to port operations and log fumigations. None of the companies using AC and/or ammonium thiosulfate were engaged in current research programs relevant to the needs of the New Zealand log export industry for meeting the 2020 MB regulations. One company, Genera, was unique in having both a potentially viable MBRDT and a current research and development program specific to the New Zealand log export industry. Updated recommendations to the STIMBR Board are provided in the review report.
Revised MBRDT Review – 18 June 2019
TERMS OF REFERENCE
An independent review carried out by Jack Armstrong, Quarantine Scientific Limited, to inform the STIMBR Board will be done on all known currently available or proposed methyl bromide recapture and destruction technologies (MBRDT). The MBRDT review will include:
• The PFR report prepared for Genera dated June 2015 in which the Genera technology was subject to a testing protocol developed by STIMBR.
• Work completed since then by Genera – specifically to access and assess the data generated from Genera testing of their MBRDT.
• Consider potential factors involved with the lower-than-expected performance of the Genera MBRDT during winter months.
• A high-level desktop evaluation of other MBRDT that show promise and are commercially available, including but not limited to the Nordiko and Value Recovery MBRDT.
• MBRDT that have been proposed but are not currently available. Specifically, these include methods and technologies that have been proposed to STIMBR for funding to build and test a MBRDT based on theory alone.
1. Recent advances in knowledge about MBRDT and the issues related to achieving the recapture and/or destruction of MB after logs, ship hold, and other MB fumigations required the updating of information to this 2017 report. The Terms of Reference and most of the information remains unchanged.
2. The author found that during the current decade (and especially as the 2020 deadline for the MB recapture requirement approaches), numerous entities, including individuals and national or international companies, have entered the MBRDT discussion without the capability to produce viable technologies. Many of these entities were providing “desktop” designs and unproven concepts to solicit research funding. While others had technologies for sale without providing proof of concept at the commercial level of the New Zealand log trade. In some instances, unfortunately, these entities became protagonists; their claims of potentially applicable but untested technology garnered support amongst some in New Zealand that effectively hindered progress by artificially inflating perceptions of progress, and distracting attention from more promising alternative technologies.
3. The author notes that STIMBR, in its search for viable MBRDT options, has been responsive to every MBRDT submission of merit. Moreover, STIMBR has offered to fund commercial scale validation trials for any MBRDT that meets the simple application criteria outlined in the STIMBR Assessment Criteria for Considering Support for MBRDT Validation Tests (Appendix B).
Regardless, of the many claims for MBRDT capable of recapture and/or destruction of MB from log stacks, no applications other than those from Bletchley and Genera have been made.
4. The author developed this report as an objective, science-based review of the available MBRDT and concepts for the recapture and/or destruction of MB after fumigation and does not support one technology or company over another. However, it is fair to note that Genera Research and Innovation, Mt Maunganui, New Zealand, is the only entity this author found that was actively (and with its own funds) pursuing comprehensive research and development for large scale log fumigations across a wide range of MBRDT to meet the 2020 requirements. No other individual or company, nationally or internationally, is currently engaged at this level of response to the MBRDT issues facing log fumigators, including owning and testing credible MBRDT.
Revised MBRDT Review – 18 June 2019
5. The author reaffirms the earlier conclusion that, despite claims that suitable technologies are available for use with large scale log fumigations, those claims have not been substantiated by their advocates. Moreover; despite their respective commitment, considerable research investment and nine years of effort by STIMBR and Genera Research and Innovation towards the goal of reducing the MB concentration to 5-ppm or less (set by the EPA in 2010) in the headspace following log fumigations in stacks or ship holds, no immediate solutions are available. While Genera Research and Innovation now has a partial solution currently available for log stacks, the recovery and destruction of MB from ship holds in which logs are fumigated presents significant challenges that must be addressed.
After the implementation of the Montreal Protocol (UNEP 1992) that culminated in the elimination of MB for other than quarantine and pre-shipment (QPS) uses, a concerted and ongoing research effort has been seeking to identify alternatives. A fraction of that research effort has gone into the research and development of methods and technologies to control MB emission by capture and destruction of any MB remaining in the treated space after a fumigation is completed, including the MB that desorbs from the treated material.
Although initial work on the concept of MB recapture dates from the mid- to late-1990s (e.g., Gan and Yates 1998, Knapp and Leesch 1995, Knapp et al. 1997, Knapp and McAllister 1998), a consequence of the Montreal Protocol (UNEP 1992) was that little progress was made in developing actual
commercial systems beyond the laboratory. In a country-wide review, the Australian Pesticides and Veterinary Medicines Authority (APVMA) noted that: “For economic and logistical reasons, recapture technology is not yet mature enough for mandatory implementation within the Australian fumigation industry. Note that the Montreal Protocol does not expect adoption of technologies for methyl bromide reduction, if there are no available options or the cost of options is not economical.”
The bold-faced notation by the APVMA acknowledges both the philosophy of the Montreal Protocol and the difficulty in developing MBRDT. The APVMA (2007) stated that they would continue to monitor developments in MBRDT to determine when such technologies became “economically and logistically feasible”.
The AVPMA (2007) review, which preceded the New Zealand Environmental Risk Management Authority (ERMA, now the New Zealand Environmental Protection Authority, EPA) by several years, acknowledged the difficulty in up-scaling laboratory, small prototype or equipment that worked for smaller (and usually static) MB recapture operations to fit large commercial operations, such as log stack and ship hold fumigations. Although consideration was given to the use of mandatory recapture and/or destruction by a specified date in the future, forcing the use of MBRDT when none existed or were not economically feasible was untenable. For example, use of MBRDT in Australia was found to increase the cost of fumigation by 25% to 50% (APVMA 2007). Moreover, APVMA (2007) identified that ship hold fumigation presented a particular challenge because of the great amount of gas that must be recaptured on activated carbon (AC) at a rate of 1.0 g MB to 10 g of AC, which results in tonnes of AC required to recapture the MB and then that amount of MB-saturated AC requiring safe disposal.
The ERMA (2010) decision that required the recapture of any remaining MB at the end of every fumigation by October 2020 highlighted the significant gap that existed in both MBRDT research and available technology. For example, the issue of MB recapture was identified during a Māori Reference Group Workshop convened to consider the application to the EPA seeking approval to use
Revised MBRDT Review – 18 June 2019
ethanedinitrile in New Zealand (NZEPA 2016): “research and global experience has shown that recapture [and/or] destruction of MB from large scale fumigations is both scientifically and technically challenging. [The] recapture [and/or] destruction of all of the methyl bromide remaining in the head space at the end of a fumigation, as required by the EPA 2010 decision, may not be possible.”
Before research on MBRDT first appeared in the literature (1995), the recapture of MB and other halogen compounds (e.g., ethylene dibromide, methyl iodide) was restricted to research on improving gas mask filters that used AC or other materials that either adsorbed or chemically degraded the target toxicant (Miura et al. 1983, Rozvaga and Bakhishev 1982, Wood 1985). Setting the stage for MBRDT research was an evaluation of [then] current containment and control options for methyl bromide (MB) in commodity treatment done by DeWolfe and Harrison (1994) for the US Environmental Protection Agency.
A review of the literature from the 1990s to the present found that two methods of recapturing MB received the most consideration for research, development and commercialization, viz., absorption by AC or by reactive liquids. Sorption by reactive liquid technologies resulted in the destruction of the MB molecule, i.e., a “stand-alone” MBRDT. Several methods that received the most consideration for processing MB-contaminated AC included pyrolysis (high-energy destruction), chemical destruction, recovery as liquid MB for reuse, or simple disposal in waste sites. However, for all the MBRDT reviewed herein, the first and foremost problem is one of “scalability” to meet the needs of the log export industry. Although many of the MBRDT reviewed had attributes that made them ideal for removing MB from containers, static fumigation facilities or other small fumigation processes, none could be upscaled for use in removing residual MB from log stacks or ship holds. Moreover, no entity worldwide other than Genera Science and Innovation in New Zealand has an ongoing program that is attempting to develop MBRDT on the scale necessary to meet the October 2020 deadline for the recapture and/or destruction of MB following fumigations in New Zealand.
Appendix A provides an overview of the issues and challenges that must be addressed in the use of AC in any MBRDT.
AC was the first of two MBRDT that became prominent in the literature. AC was used as a sorbant for the removal of MB (i.e., the MB was captured by sorption) (Bell et al. 1996; Falco 2010; Gan and Yates 1998; Gan et al. 1995; Gan et al. 2001; Hall and Walse 2014; Kawakami and Soma 1995; Knapp 2001, 2005; Knapp and Leesch 1995; Knapp et al. 1997; Knapp and McAllister 1998; Knapp and Mazzoni 2009; Leesch 1996, 1998; Leesch and Knapp 1998; Leesch et al. 2000; McAllister and Knapp 1999;
Nordiko Quarantine Systems 2010; Nordiko 2014; Snyder and Leesch 2001)
AC can adsorb relatively substantial amounts of MB. MB capacities vary with carbon type, conditions and tolerance for quantities of fumigant transiting through the system. Capacities of up to 30% by weight are said to be achievable at low temperatures (10°C) (Snyder and Leesch, 2001), but in practice maximum loading of MB is more likely to be around 5 – 10%. Sorption is temperature dependent, with less MB adsorbed at higher temperatures (MBTOC 2006). The adsorption is exothermic (Leesch et al., 2000). In small fumigations with low residual MB concentrations, rapid and almost complete removal of MB from a vented air stream is easily achievable. Publications on carbon for MB recapture do not typically specify the type of carbon used. It appears that carbon derived from coconut husk is typically used. This is a microporous carbon that is widely used for removal of organic contaminants from air streams. It had the highest capacity of the three types of carbon tested by Leesch et al. (2000). Leesch
Revised MBRDT Review – 18 June 2019
et al. (2000) and Snyder and Leesch (2001) give mathematical descriptions of MB loading as a function of temperature and moisture content of the carbon.
Well designed, sized and operated recapture systems based on AC as the recapture medium provide almost complete recovery of MB, often at efficacy >99.9% (MBTOC 2014). However, eventually the adsorption capacity of the AC is reached, and it needs to be regenerated or disposed. Regeneration can be achieved by passing hot air over the AC and could be the basis of a reclamation process.
Alternatively, the AC and MB can be incinerated in a specialized facility (no such facility currently exists in New Zealand). However, concerns about emissions of toxic chemicals may prevent this from being a viable option in some locations (MBTOC 2014). Otherwise, the MB-contaminated AC must be disposed in a landfill or other commercial or municipal dump site.
Although many commercial AC-based MBRDT claim to be efficient in removing MB, the author found little data in the literature to support these claims, and no data to support the efficiency of these MBRDT to remove MB from log stacks or ship holds. The ability of an AC-based MBRDT to recapture >99% of MB after a fumigation would certainly be a “selling point” for the purveyor of the MBRDT and it would be reported in the Assessment Reports of the Methyl Bromide Technical Options Committee cited herein.
Interestingly, although the 2006 MBTOC Assessment Report discussed the efficiency of one MBRDT, no Assessment Report after that year provided any additional discussions on MBRDT efficiency.
Moreover, the efficacy of any commercial MBRDT cannot be deduced by simply scaling up the results of small-scale laboratory studies found in the various MBRDT patents.
The following example shows the specifications that a carbon-based MBRDT must meet for the US Department of Agriculture – Animal and Plant Health Inspection Service (USDA-APHIS) to consider it for regulatory use (MBTOC 2014). Specifically, the system should:
• accommodate a variety of enclosure types (both portable and fixed chamber);
• accommodate MB monitoring sensors in the air flow (number and placement of sensors will depend on the size of the equipment);
• accommodate the fumigant concentrations and temperature conditions listed in the USDA-APHIS Treatment Manual;
• ensure that all untreated ventilation air is under negative pressure (in the event of a leak, ambient air will leak into the system instead of contaminated air escaping from the system);
• leak-tight (including all valves, ducts, canisters);
• provide a minimum adsorptive capacity of 1 kg of MB per 22 kg of carbon (The quality of the carbon will determine the adsorptive capacity. A lower quality carbon could result in a ratio of 1 kg of MB per 44 – 55 kg of carbon);
• provide between 4 and 15 complete gas exchanges per hour;
• provide flow and pressure system monitoring;
• provide onsite installation, training, and continual technical support;
• retain approved fumigation and aeration times as mandated by the PPQ Treatment Manual;
• not exceed 500 ppm (32 g/m3) MB gas released to the atmosphere and provide the ability to document MB concentration levels; and
Revised MBRDT Review – 18 June 2019
• reduce emissions of MB by at least 80%1
From the emissions reduction requirement of “…at least 80%...”, an assumption can be made that carbon-based MBRDT cannot reasonably be expected to recapture more than 80% of the MB after fumigation. If such were the case, USDA-APHIS would have required a greater percent recapture.
Moreover, the European Community in its document on the EC strategy for phasing out MB stated that
“Worldwide there are very few facilities that have the operational capability to capture methyl bromide that would otherwise be vented to the environment after fumigation. Even when such equipment is in place, it can only capture the methyl bromide that remains free in the fumigation chamber or facility, as often a significant quantity remains in the wood, packaging, or the commodity, which is then slowly released to the environment weeks or months after fumigation. For this reason, capture equipment is not able to reduce methyl bromide emissions to zero or even very low levels. However, recapture technologies reduce MB emissions and are technically feasible for commodity fumigations and some structural fumigations” (EC 2009).
Ultimately, four questions must be answered before considering any AC-based MBRDT:
• Does the MBRDT provide the desired efficacy (percent of MB removed after fumigation)?
• Is the MBRDT cost-effective (what is the cost of either destroying the MB captured on the AC or disposing of the contaminated carbon?
• Does the process effectively manage the disposal / environmental fate of the captured MB?
• Has the MBRDT been demonstrated to be capable of large-scale recapture (e.g., multiple log stacks, ship holds)?
First, an AC-based MBRDT that provides the desired efficacy must be identified based on data from testing the system in the commercial log fumigation situation, then doing cost-benefit analysis to determine the economic impact on log export profits based on the amount of MB that needs to be recaptured over a given period, operating cost, and the cost for either MB destruction or disposal of the contaminated carbon.
A critical issue with an AC-based MBRDT is that the AC does not destroy the MB but instead only holds the fumigant for a brief time, eventually allowing it to be let back into the atmosphere (Swords et al 2012). Desorption of MB from AC stored in intermediate bulk containers left in sunlight has be reported at CentrePort Wellington (Dr Matt Hall, pers. comm.), indicating that thermal desorption of MB is possible at ambient temperatures experienced at New Zealand ports.
1 The current level of MBRDT capability appears to be about 80% recapture of the MB remaining under the tarpaulin at the end of log stack fumigations (M. Self, Genera, personal communication). The 80% recovery rate is significantly different from the 5-ppm limit on remaining MB that is required by the control determined in the 2010 MB reassessment (NZERMA 2011).
The 5-ppm requirement (NZERMA 2010) was based on the Workplace Exposure Standard (WES) for MB. Unfortunately, the 5-ppm requirement does not appear to have been subject to public comment during the MB reassessment decision-making process (I. Gear, STIMBR, pers. comm.). The 5-ppm WES value is a worker safety exposure value and has nothing in common with the recapture and/or destruction of MB to reduce the concentration that is released into the environment after a fumigation is completed. In the latter case, where a MBRDT would be used, the significant value is a percentage of the remaining fumigant that would be removed before venting occurs. Attempting to use a ppm value does not consider the desorption characteristic that are inherent in any fumigation regardless of the fumigant used and, therefore, has no scientific merit as a MB recapture and/or destruction value. An application was approved to be processed as a modified
reassessment by the EPA (formerly ERMA) in May 2019 (Refer: https://www.epa.govt.nz/news-and-alerts/latest- news/reassessment-of-methyl-bromide/ ). The modified MB reassessment seeks, in part, to revise the 5-ppm limit to a science-based calculation that can be achieved under commercial conditions with the available advances in MBRDT.
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It is technically possible to recycle MB adsorbed on AC by heating the Carbon. The MB is reclaimed as a high concentration mixture in air suitable for direct reuse as a fumigant, but some topping up will be necessary to compensate for system losses to achieve a satisfactory fumigation concentration.
However, there have been concerns about the purity of recycled MB (MBTOC 2014).
A consideration for recycling MB used for log fumigations would be the potential for substantial contaminants from the logs themselves, including terpenes and other constituent compounds found in pine2. Additionally, desorption from carbon is relatively slow, operational attempts to desorb faster have encountered problems with uneven heating and fire risk. Because of the problems encountered with recycling captured MB, AC has received more attention as a means of capturing MB after fumigation for subsequent destruction (MBTOC 2014). From an economic perspective, there is little information on the costs associated with recycling MB from AC in the literature. MBTOC (2002) states that the cost of a complete MB supply and removal service would be about seven times that of the MB price, but on a per unit basis for commodity treated, the price may be affordable (Leesch 1998). The commodity to which Leesch (1998) referred was fresh produce, not durables, such as logs. One of the critical features of this process is the environmental impact (truck fuel, energy use) of transporting equipment containing the AC beds saturated with MB over some distance to the reprocessing or destruction plant (MBTOC 2002). Other “novel” technologies developed over the years and reported in the literature and/or presented at symposia (e.g., Chen and Pignatello 2012; Laurence et al. 2003; Li and Mitch 2015; Miller and Baesman 2002; Miller et al. 2003a, b; Mitch 2011; Park et al. 2001; Pignatello and Chen 2011;
Pignatello and Hsieh 2016; and others) have not seen commercial use. Regardless, concepts for the recapture and reuse of MB have resulted in several commercial operations using fixed fumigation chambers or systems (Hall and Walse 2014, MBTOC 2014).
Zeolites in place of activated carbon
Zeolites are hydrated aluminosilicates of the alkaline and alkaline-earth metals. About 40 natural zeolites have been identified during the past 200 years; the most common are analcime, chabazite, clinoptilolite, erionite, ferrierite, heulandite, laumontite, mordenite, and phillipsite. Today, there are more than 150 industrially synthesized zeolites. Major markets for natural zeolites are pet litter, animal feed, horticultural applications (soil conditioners and growth media), and wastewater treatment. Major use categories for synthetic zeolites are catalysts, detergents, molecular sieves.
Zeolites have been noted in the literature as a potential alternative to AC. Zeolites have a porous structure that make them valuable as adsorbents and catalysts. They are found naturally and can also be manufactured to precise specifications. Processes based on the use of zeolite adsorbents to remove CFCs from vented air streams are in commercial use.
Zeolites are more expensive than AC at about twenty times more in cost per kilogram (USEPA 1999).
Although zeolites are more expensive than AC, they have high adsorptive capacity, particularly at low concentrations. They can be manufactured to very narrow pore size distribution tolerances for specific applications and it may be possible to avoid any potential problems of contamination of the recovered MB with other volatile compounds, by utilizing the selective sorption that is conferred by a specific pore size range. A commercial zeolite based MBRDT, Bromosorb™ (Nagji and Veljovic 1994), was tested
2 There are two MBRDT systems that do reuse MB recovered from the AC. One is a fixed facility found at several ports in China where log fumigations with MB are done. However, there are no data available that prove the operate successfully.
The second MBRDT system, a prototype built by Genera Science & Innovation, is a portable MBRDT that reuses the MB and has been demonstrated to be effective only for full-sized log stacks under research conditions (M. Self, Genera, personal communication).
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(MBTOC 2002) but disappeared from the literature. Later, Willis and Veljovic 1996, Willis (1998) and Weightman (1999) attempted to resurrect the use of Bromosorb™ but no commercial applications resulted from their work (MBTOC 2002), and the Australian parent company for Bromosorb™, Halozone Recycling, Inc., is no longer a registered company (see
One additional issue with the use of zeolites is that of health and safety. Although the more expensive industrially manufactured zeolites are listed only as eye and respiratory system irritants, the significantly less expensive natural zeolites are known respiratory carcinogens that, like asbestos, can cause mesothelioma in the lungs (see https://www.cancer.org/cancer/malignant-mesothelioma/causes-risks- prevention/risk-factors.html).
Absorption into reactive liquids
MB can be destroyed by reaction with ammonium thiosulphate (Gan et al. 1997, 1998) and amines, e.g., ethanolamine (Hettenbach et al. 2002). The reaction products, Br− and sodium methyl thiosulfate (NaCH3S2O3), are freely soluble in water, non-corrosive, non-volatile and low in toxicity.
Although some applications using only a reactive liquids were attempted, the technology using reactive liquids quickly morphed into a combination MBRDT in which AC is initially used to recapture the MB (a carbon “sink”) after fumigation and then ammonium thiosulphate (or other proprietary reactive fluid or combination of reactive fluids) are then used to destroy the MB by a substitution reaction (Joyce 2005, 2007, 2014; Joyce and Bielski 2003, 2004, 2008, 2010, 2013; Joyce and Gomez 2016; Joyce et al.
2004; Mitch and li 2014; Mitch and Yang 2013; Swords et al. 2011, 2012; Thompson et al. 2015 and others). Therefore, almost all the commercial MBRDT available today (and those reviewed in this document) are based on a combination of recapture using adsorption onto AC and destruction using absorption into a reactive fluid.
ATTRIBUTES OF A COMMERCIALLY VIABLE MBRDT
The attributes necessary for the commercial viability of a MBRDT for eliminating MB remaining under the tarpaulins at the completion of log fumigations include:
• The MBRDT must be mobile so that it can service every individual fumigated stack at the port and access each individual hold on every ship in which in-hold MB fumigation is undertaken.
Moreover, the MBRDT cannot be static whereby exhaust ducting from the stacks to the MBRDT impedes movement at the port or requires major port modification to place the ducts below the port surface.
• The MBRDT must be self-contained and should not require major port redesign and/or impede the flow of vehicles and logs. The MBRDT cannot be static whereby exhaust ducting impedes movement at the ports.
• The MBRDT must be rapid in application and be capable of recapturing and destroying MB remaining in a stack at a commercially viable and cost-effective rate to the desired percent required by regulation.
• It is critical that the MBRDT does not emit secondary chemical components into the atmosphere or produce any byproducts (e.g., carbon contaminated with MB) that cannot be readily disposed into landfill or the environment without causing unnecessary harm or leaving unwanted residues.
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• The MBRDT must be cost-effective and commercially competitive3 with current fumigants, e.g., phosphine at $1/JAS and MB (without a MBRDT) at $4/JAS; current non-fumigation
technologies, e.g., $8-10/JAS for debarking; or technologies currently under development, e.g., Joule Heating estimated at $7-9/JAS. Some 2006 fumigator estimates in Australia for the lease and filter costs for MBRDT systems for them, plus extra work hours to mount, monitor and operate the systems, could be in the order of AU$500,000 to AU$750,000 per annum.
• Every commercially available or proposed MBRDT must have readily available scientifically validated documentation of data showing the percent MB that is recaptured from log stacks over time under commercial conditions, i.e., system cannot be unproven “drawing board” concepts.
• Systems must be amenable to immediate scale-up to commercial conditions at the ports and readily fit into port operations.
• Overall, the logistical operation and costs of sufficient recapture systems to handle peaks (in particular), transportation of recapture systems between depots (or multiple stores of recapture systems at key locations) and the replacement of recapture filters, all need to be clarified at a practical level (APVMA 2007).
REVIEW AND ASSESSMENT OF CURRENT AND POTENTIAL MBRDT 1. Incineration / Combustion
Research was carried out in Japan in the 1970s on methods using either direct combustion or catalytic cracking to destroy MB in the venting gas stream from chamber fumigations (Anon. 1976).
Large pilot plants were constructed to test the techniques, but neither method proceeded to commercial installation. Although the processes were able to reduce the MB concentration to low [sic] ppm levels, further development was prevented because of the prohibitive cost, the unsuitability of the methods for stack fumigations (i.e., the equipment was not transportable), concerns about the use of direct heat when MB can (under very restricted conditions) form an explosive mixture with air, and the difficulties of handling the by-products that resulted from MB destruction (i.e., HBr and Br2) (Anon. 1976).
Catalytic decomposition of MB using new Mn/Cu zeolites was investigated in Japan with promising results that indicated satisfactory levels of recapture and destruction could be obtained at low [sic]
temperatures around 300°C (Nippon Shokubai 2002). Tests were conducted with a MBRDT machine equipped with alumina/precious metal-based catalysis for combustion of halogens.
Although this machine required an alkali neutralization process, it could recapture and decompose MB at temperatures < 300°C. However, further production of such machines for commercial use was halted due to a lack of demand (Nippon Shokubai 2002).
Belmonte et al. (2001) patented the mixing of alkyl halides with a combustible fluid and then oxidizing the mixture catalytically. This approach was not commercialized or progressed further.
3 Logs are a “durable commodity” and the export values must be taken into consideration when mandating requirements that negatively impact profit margins. For example, the significant capital costs involved with the construction and implementation of MBRDT will have a greater negative impact for logs at < NZ$3.00/tonne (highest current landed at wharf price; D.
Hammond, STIMBR, personal communication) compared with the impact mandated MBRDT on export kiwifruit at
NZ$4,150/tonne or apple and pear exports at NZ$2,050/tonne (2019 forecast figures, MPI 2019).
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A literature search in June 2019 found no advances for the use of combustion as an MBRDT.
However, some email correspondence from Smith Agri International Distribution (SAID) to STIMBR claimed SAID were the exclusive distributors of an EIM Technologies (EIM) Gas Destruction Unit (GDU). The SAID-EIM-GDU was stated to be designed specifically for the capture and destruction of MB, and “that meets, exceeds and is approved by the Montreal Protocol.” The latter claim was cited as “formal approval as a methyl bromide destruction technology at the Thirtieth Meeting of the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer held on 5-9 November 2018”. Interestingly, SAID also stated that the “EIM-GDU was officially launched to institutional investors and industry” in September 2018 at a conference in Portland, Oregon USA, i.e., SAID was seeking investors to fund the EIM-GDU scheme. Problematic for the SAID claim of UNEP approval is that the Montreal Protocol does not “approve methyl bromide destruction
technology” (UNEP technical panels and committees are responsible for technology approvals) nor was any mention of the EIM-GDU found in the agenda or minutes of that meeting (UNEP 2018a).
SAID, as described on their website (https://www.commercialrealestate.com.au/real-estate- agents/smith-agri-international-pty-ltd-30846) is a real estate agency specializing in commercial property, offering agricultural properties for sale, and with an apparent sideline business in
developing investment resources. Between March 2019 (the date of the original email from SAID to STIMBR) and June 2019 there were no further contacts from SAID.
Information was found in the Technology and Economic Assessment Panel reports for 2018 that may be related to the SAID-EIM-GDU claims (UNEP 2018b,c,d), The supplement to the April 2018 Technology and Economic Assessment Panel (UNEP 2018c) noted that “a technology submitted by one company (Australia) is of the general multi-step type that extracts and then destroys methyl bromide after fumigation”. The 2018 Task Force on Destruction Technologies assessed the destruction step alone of this technology (i.e., thermal decay of methyl bromide) against the DRE (destruction and removal efficiency) criteria of 99.99% or above. It did not attempt to quantify the efficiency of the fumigation and extraction steps of the process or any associated fugitive emissions.
Although the assessment recommended that the technology had “high potential”, no “approval” of the technology was given (UNEP 2018c). Following the supplemental report (UNEP 2018b), an addendum (UNEP 2018b) provided for presentations by members of the assessment panels and technical committees that reviewed the destruction technologies for controlled substances. UNEP (2018b) states that, for the submitted technology on thermal decay, “the operating temperature remained in the range where dioxins/furans could still be formed and, although thermal decay of methyl bromide remained recommended as high potential…[it was] not recommended for approval…”.
While the SAID-EIM-GDU story may appear to be vacuous and unnecessary to this review, it is an example of the claims that are becoming increasingly made to STIMBR, members of the forest industry, and various entities of the New Zealand government that advocate MBRDT concepts or systems that need funding to build and/or test. At best, these unsupported claims can be simply ignored, at worst, they result in expended time and cost to determine their veracity and they impede progress by disseminating erroneous information and causing confusion within an industry that is facing a serious issue.
By comparison, the MeBrom® thermal decay MBRDT is a proven system, albeit not currently applicable to use for removing residual MB after log stacks or ship hold fumigations. MEBROM® (see https://www.mebrom.com/index.html), the second largest distributor of MB worldwide, has developed internationally recognized refrigerant gas reclamation methods and services from reclaiming, storing and destruction of refrigerants and other gases, including MB, that adversely affect the ozone layer. MeBrom® Research and Development in Adelaide, Australia developed a
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mobile gas destruction unit called the MeBrom® Gas Destruction Unit called the GDU 3600 (the
“3600” refers to the total air intake volume in m3/24 h). The GDU 3600 is a single pass destruction system designed to capture and destroy toxic, ozone depleting and global warming gases, such as (but not limited to), MB, sulfuryl fluoride, sulphur hexafluoride and phosphine .
Initial testing of the GDU 3600 carried out by MeBrom showed that almost 100% MB recapture (Cox 2017) was possible although there are no reports of this system being used for the destruction of the other fumigants. Specific to its use as a MBRDT, the GDU 3600 was only tested on 20ft shipping containers. Although MeBrom indicated that the GDU 3600 could be upscaled to meet the needs of any application, including log rows and vessel holds, tests by Genera (Appendix C) on log stacks fumigated with MB found a number of issues that included (1) the generation of significant amounts of hydrogen bromide gas that indicated both an insufficient scrubbing process and a worker safety hazard, (2) inability to completely remove residual MB from the stacks, i.e., an insufficient capacity for use on log stacks, (3) potential waste disposal issues, and (4) the time required for MB removal (about 25 h) was too lengthy for use on log stacks as a port.
Although Genera found that the GDU had the potential to be upscaled for some MBRDT uses, the GDU 3600 in its current state could not be used to remove MB from log stacks after fumigation (Appendix C).
2. EnviroFume / Bletchley System
EnviroFume, which later became Bletchley Ltd., developed a thiosulphate based MBRDT. A scientific validation test of the EnviroFume / Bletchley MBRDT was carried out at South Port, Bluff, on 25–26 April 2015. The validation test of the destruction system was determined after fumigating three rows of pine logs (Pinus radiata D. Don.; average volume = 407.8 m3) with 120 g/m3 MB for 16 h under tarpaulin. The logs were fumigated by South Fume Ltd, Timaru, using similar commercial practices and equipment to those used throughout the industry for log exports, and the MBRDT was operated by Bletchley Ltd, during the validation test. The analysis of air samples found that the MB concentrations entering and exiting the MBRDT were similar over a 1-h period, which means that the system did not effectively destroy MB. This result was unexpected, because the chemistry of thiosulphate-based destruction of MB is well known (Hall et al. 2015). If the destroyed fumigant/air mixture were returned to the stack for further passes through the system, then the destruction efficiency may have been established. However, there was only one pass of the fumigant/air mixture through the system before venting which may have impacted the results. Consequently, the
EnviroFume / Bletchley MBRDT was not recommended to STIMBR for further support. The
EnviroFume / Bletchley MBRDT equipment was purchased by Genera and further testing found the equipment did not work (M. Self, Genera, personal communication).
3. Salience Solutions / PyroPlas – Electric Arc (Plasma) Destruction of MB
Pursuant to discussions in April 2016 between Ian Gear and Dr. V. S. Nair, Managing Director, Salience Solutions, Victoria, Australia, regarding the potential use of his company’s “state of the art”
electric-arc technology combined with an integrated sodium hydroxide scrubber system. A review of the PyroPlas™ MBRDT was done by the author (Armstrong 2016) to provide STIMBR with advice whether to pursue further discussion with Salience Solutions regarding the use of their MBRDT.
The 10 November 2015 document, “Introduction to PyroPlas™ Plasma Arc Destruction Unit”, which describes in detail the PyroPlas™ MBRDT, was reviewed. The author then queried a contact in Australia, Dr. John Sanderson, Principal Environmental Engineer, Earth Systems, another company
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that produces commercial chemical scrubbing and destruction systems based on electric-arc technology. Dr. Sanderson was provided with a basic overview of the New Zealand log export industry, port operations, and MB fumigation of log stacks.
Dr. Sanderson did not believe his or any other company’s electric arc technology was suitable as a MBRDT for the New Zealand log export industry because the electric arc technology and equipment would be too expensive, would have too great a footprint in the port situation, and would not be portable. Dr. Sanderson was familiar with scrubbing technologies for fumigants and recommended the use of liquid phase recapture and destruction technologies (e.g., the method proposed by Genera, Bletchley, and others) over any consideration of plasma technology.
Additionally, contacts at the US Department of Agriculture, Animal and Plant Health Inspection Service were queried because a variety of incinerator systems are located at various ports in the US. The response was that the incinerators were used to eliminate potential insect infestations in contraband fruits and vegetables and in wood pallets, dunnage and packing materials, but they were not used for fumigant destruction (R. Mack, USDA-APHIS, pers. comm.).
The author sent email queries to Dr. Nair requesting:
• A comparison of the relative capital outlay and operating costs between the PyroPlas™
MBRDT and other MBRDT that use AC and/or liquid phase absorption and destruction technologies. This information would be valuable for comparing the PyroPlas™ system with currently available technologies.
• His opinion on the potential for the PyroPlas™ MBRDT be manufactured as a compact and mobile system (which Dr. Sanderson did not believe could be done), preferably small enough to fit on the back of a flatbed truck or on a trailer.
• His opinion on whether the PyroPlas™ MBRDT, if amenable to manufacture as compact mobile systems, could be manufactured in quantity at a cost-effective price for the New Zealand log export industry and, if so, could a cost estimate be provided?
Unfortunately, no response was received to retransmitted queries over a two-month period.
Based on the author’s review of the PyroPlas™ technology, discussions with Dr. Sanderson and USDA-APHIS, and the lack of response from Salience Solutions, the author concluded that the PyroPlas™ technology was not a suitable MBRDT for further consideration by STIMBR (Armstrong 2016).
Salience Solutions / Pyroplas™ does not appear to have changed its website since 2017. Although the Pyroplas™ system was still identified as a method for MB destruction, no new information was provided.
Ozone is an unstable three-atom allotrope of oxygen formed by the excitation of molecular oxygen (O2) into atomic oxygen (O) in an energizing environment that allows the recombination of atoms into ozone (O3). Ozone is a powerful oxidizing agent that is used for disinfection processes in aquaculture, marine aquaria, fish disease laboratories, heating and cooling units, water treatment, food processing, bleaching of paper pulp, and treatment of contaminated groundwater (Armstrong et al. 2014).
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Any discussion of ozone as a potential candidate compound for use as a MBRDT must consider its many important characteristics (Armstrong et al. 2014), including:
• Ozone is a highly unstable and highly (dangerously) reactive compound. Although ozone is not flammable, it a strong oxidant that can initiate and accelerate combustion or cause explosions.
• Because it readily oxidizes organic compounds, ozone can cause severe respiratory toxicity.
• Ozone is corrosive to copper and other base metals; therefore, all systems used to hold, transport, or conduct ozone must be made of stainless steel and all electrical components must be isolated.
• Ozone is corrosive to fabrics and plastics, including plastic tarpaulins used for fumigation.
• Ozone is readily absorbed into water (e.g., free water in logs) where it decomposes rapidly (half-life is approximately 15 min) into oxygen. Additionally, ozone rapidly decomposes in air (half-life is approximately 30 min) into oxygen. Therefore, any system with water and/or air in which ozone is used will require a continuous replacement of lost ozone to maintain the desired concentration.
• Ozone rapidly dissipates into the atmosphere. Therefore, any system using ozone must be a closed (i.e., airtight) system. Moreover, Armstrong et al. (2014) noted that the use of ozone in a closed system generally required the system to operate under vacuum conditions, which greatly increases the cost for ozone chambers and would preclude the use of a pass-through system that could move the remaining MB after treatment.
Because of the difficulty in handling ozone and its highly reactive nature, ozone is not considered a viable candidate for use as a MBRDT for log fumigations in New Zealand. However, a “recovery”
plant was installed in late 1996 at a cotton fumigation facility at the port of Los Angeles, USA. The facility used ozone to destroy the MB in the discharge and air washes for the USDA vacuum fumigation chambers followed by scrubbing with AC to eliminate any residual traces of MB from the discharge air stream that did not react with the ozone. The system appears to be unique and it was installed to meet strict local air quality requirements (MBTOC 2006). Whether this facility was currently in operation was not ascertained. Additionally, Walse and Hall (2011) reported the use of ozone to destroy MB captured on AC, but the results were from small laboratory-scale tests.
As of June 2019, the author found no new information on the use of ozone as a component of an MBRDT system since the report by Walse and Hall (2011).
5. Value Recovery
MB reacts with nucleophiles to produce bromide ion and methylated products. Typical reactive nucleophiles include activated oxygen, sulphur and nitrogen. The reaction occurs when MB reacts with many constituents of foodstuffs and other natural products, giving rise to the bromide residues typically produced in MB fumigations. Several different nucleophiles have been used on an
experimental and pilot scale to recapture and decompose MB after fumigations. MB can be destroyed by reaction with ammonium thiosulphate (Gan et al., 1998), through reaction with one of the sulphur atoms in the thiosulphate.
The Value Recovery MBRDT is based on the original US patent of Joyce et al. (2004) that proposed a phase transfer catalysis scrubber to destroy alkyl halides, such as MB, and a subsequent US
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patent (Joyce and Bielski 2010) that proposed a scrubbing system based on reaction with aqueous thiosulphate, with or without an immiscible organic solvent present to assist trapping the MB.
“In some applications, for example where alkyl halide levels are to be reduced to an especially low level, it may be desirable to connect two or more scrubbers in series, such that purified gases exiting a scrubber are further purified by subsequent passage through another. On the other hand, in some applications it may be desired to rapidly purify a large volume of gas, in which case two or more scrubbers may be used in parallel. Combinations of series and parallel arrangements may also be practiced according to the invention, using multiple scrubbers” (Joyce and Bielski 2010).
Data provided by Joyce and Bielski (2010) in their patent documents show that the percentages of MB removed by their process from 15,000 ppm MB concentrations in eight separate experiments were 63, 56, 70, 86, 80, 73, 77, and 87% with an experimental uncertainty of 1.2% for each figure.
According to the 2006 MBTOC Assessment Report, a review of data provided by Value Recovery and a Value Recovery press release found that the destruction of MB was about 86% of the total entering the scrubber. However, later MBTOC Assessment Reports mention the Value Recovery MBRDT but provide no information regarding efficacy in removing MB after fumigations. A 2006 press release claims that the Value Recovery MBRDT “…destroys 91-percent of MB in commercial demonstrations” (Value Recovery 2006). Interestingly, a Value Recovery press release in 2016 claims an independent California-approved validation source showed that the Value Recovery MBRDT destroyed over 94% of the MB collected. Hence, the destruction efficacy of the Value Recovery MBRDT can be assumed to be somewhere between 86% and ≤94%.
Although the Value Recovery MBRDT is the most “advertised” system in the literature, no additional data could be found which specifically addresses the efficiency of the system. Before further
consideration by STIMBR, Value Recovery needs to provide data specific to the recovery and destruction of MB from commercial log fumigations. Volumes of MB recaptured by existing Value Recovery installations measure in the tens of kilograms per cycle, indicating that significant scaling would be required to meet the requirements of large-scale log fumigations.
Further review in June 2019 found no change to the information offered by Value Recovery. And, although Value Recovery claims to be “the only company to offer validated methyl bromide
emissions controls on this scale and ours is the only performance based methyl bromide emissions control system on the market”, the systems identified in the Value Recovery literature appear to be large, stand-alone, static facilities that may work well when attached to a stationary fumigation facility. The author found no indication that Value Recovery can produce equipment that could readily be used to recapture and/or destroy MB from log stacks or ship holds. The mention of a portable scrubber was found at https://www.valuerecovery.net/portable.html. However, the two sentences regarding a “portable scrubber” must be quoted here verbatim because there is some apparent confusion between recapture and fumigation. Specifically, the statements are: “Our partners can provide a scrubbing service at your site by deploying a portable system that sits on the back of a flat-bed truck. This system is capable of scrubbing volumes of up to 15,000 cubic feet or less in one application. This unit is used to fumigate individual containers and small structures (houses and stores), furniture, electronic goods, trucks and equipment”.
An assessment of the Value Recovery MBRDT by Genera for STIMBR found that the technology in its current form could not be used for the recapture and/or destruction of MB for log stack or ship hold fumigations (Appendix D).
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Nordiko (Nordiko 2006, MBTOC 2006) have developed an efficient system for the recapture of fumigant MB on AC, followed by destruction with aqueous sodium thiosulphate solution. This system is in commercial use for shipping containers in Australia and elsewhere. Typical efficiencies
(MBTOC 2006) of destruction (DRE) for the Nordiko system are claimed to be high (>99.8%), with overall efficiencies of about 70%. According to Falco (2010), the Nordiko MBRDT is capable of >
95% recapture efficiency. However, because the Nordiko and Value Recovery MBRDT systems are essentially the same, the Nordiko system has the same issues regarding lack of efficacy data.
Although Nordiko manufactures both stationary and mobile MBRDT systems, including under-tarp scrubbers, there is no data available on the actual efficacy of the mobile systems in a commercial log fumigation situation. Before further consideration by STIMBR, Nordiko needs to provide data specific to (1) the amount of AC and time required to remove 1.0 kg of MB from under a stack of fumigated logs, and because these answers may not provide a direct arithmetical model, (2) the time required for removal of all MB remaining under tarp after a log fumigation, and the efficacy and cost for the recovery and destruction of MB from commercial log fumigations.
Additionally, the economics of using the Nordiko system need to be studied in relation to using this MBRDT for commercial fumigations of logs at New Zealand ports. The only costs found in the literature were from a submission to ERMA in 2010 on the assessment of recapture of MB. The costs given were for fumigations of containers and based on leasing the system from Nordiko. The costs in 2010 were approximately $186 or $161 per containerized fumigation based on a 3- or 5- year lease term, respectively (at the time of the submission) (FPIA 2010). One fumigation operator indicated that to introduce the Nordiko “recapture” system would more than double the price of each fumigation treatment, without factoring in the leasing cost for the equipment, alterations to vehicle fleet required to transport the equipment, or costs associated with the purchase, storage and disposal of the AC (FPIA 2010).
Although Genera is currently using the Nordiko AC system to recapture MB following container fumigations at Wellington and other ports in New Zealand, the technology is not feasible for the recapture of MB after log stack, top stow, or ship hold fumigations.
As of 2019, Nordiko has participated in public hearings on the application for use of ethanedinitrile fumigant in New Zealand and in meetings at the regional and national level and made public statements to the effect that Nordiko has viable MBRDT to recapture MB from log stack fumigations for both ethanedinitrile and MB. Unfortunately, Nordiko has not agreed to enter into a contract with STIMBR to have their technology independently validated using log stacks under commercial conditions. Nordiko has declined offers by STIMBR to fund the cost of Plant and Food Research Ltd undertaking commercial verification trials (Author was present at the ethanedinitrile application hearing; I. Gear, STIMBR, personal communication; email from Nordiko rejecting STIMBR offer).
Genera has found that the Nordiko systems that they own provides an acceptable technology for reducing MB from containers holding commodities after fumigation where there is low humidity in the head space, and where the scale of recapture is sufficiently low to allow appropriate disposal of the MB-saturated carbon. The equipment would not be applicable for removing MB from the head space of log stacks after fumigation because the high moisture content would result in water being
adsorbed in place of MB uptake and because of the large volumes of AC required for the amount of MB to be recaptured (Appendix A; M. Self, personal communication).
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7. BioFume / Ecotool Systems
Ecotool Systems propose to build a trial plant to test the effectiveness of MB recapture using a cooling system to drop the temperature of the air and MB mixture below the boiling point of pure MB (< 4.4°C). This is an experimental concept that, although it may work in the laboratory, the scale-up to commercial conditions present significant challenges, including mass movement of air from a stack of logs under tarpaulin through a refrigerated ducting system with the capability of collecting and storing the MB that is “condensed” from the airflow. Although this concept is technically interesting, there is no data that can be produced to show such a technology would work commercially. Systems for recycling MB from AC using low temperatures have been studied (MBTOC 2006) but only for static fumigation systems, e.g., fumigation chambers. The proposal needs to be more than a “concept” before consideration for funding by STIMBR, i.e., data that shows efficacy under experimental conditions, and Ecotools Systems also needs to identify and address all potential issues related to the use of their concept under commercial log fumigation conditions at ports.
As of June 2019, the 02 September 2017 review for Biofume / Ecotools Systems remains accurate.
8. Desclean MB Recapture / Recovery for Reuse System
Verhaeven et al. (2005) reported research carried out in Belgium in conjunction with Desclean Belgium Development Department and VITO, the Flemish Institute for Technological Research, on the optimization of a MB recovery system. The Desclean system recaptured MB on AC, called Organosorb, a catalytic-activated microporous carbon, followed by a heating process (about 30°C) under vacuum. The recovered MB could be returned to the fumigation system with additional MB injected to obtain the desired fumigant concentration. Although Verhaweven et al. (2005) and other articles and reports dated between 2005 and 2010 on the internet claimed that the Desclean system would remove MB after fumigation down to 5 ppm, the conclusion by Verhaeven et al. (2005) states that only partial recovery of MB “up to 60% is possible on a practical and mobile way (i.e., a non- static mobile system)”. Regardless, the Desclean system was not successfully commercialized and a report by SCS Engineering (2015) reported that “Desclean Belgie N.V. (Desclean), based in Antwerp, Belgium …filed bankruptcy and ceased operations during 2011 or 2012, and its website (www.desclean.be) is no longer active”.
As of June 2019, the 02 September 2017 review of the Desclean MBRDT remains accurate.
In June 2019, L. Dear, Biovapor NZ, provided the following information to the author to clarify the review of the Biodesorb equipment that was given in the 2017 review:
“Biodesorb carried out a technical concept feasibility study and system design for STIMBR of a MBRDT that captured MB using activated carbon followed by a gas recompression process to recover MB for recycling. Biodesorb contracted the services of Worley-Parsons for the initial system modelling and feasibility study and progressed to a full system design and costing estimation.
Further studies completed by Aurecon for STIMBR were used in part to inform the development of this system and provide independent peer review of the technical concept. The Biodesorb study consists of mathematical models that show the rates of compression and cooling required to extract MB out of the airflow after fumigation is completed, including the MB desorbed from the logs. All residual MB is captured on AC beds that are mounted on wheels (mobile) and moved to the stacks
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of logs under tarpaulin or to containers being fumigated. The concept requires a central port-based
“recycling” facility (designed to fit within a 40-ft container) to contain the equipment for extracting and recompressing the MB from the carbon beds for re-use with log fumigations. The mobile carbon beds are designed to be approximately 12 m3 and are modelled to recapture up to 5 log stacks (5,000 m3 of logs) before requiring the MB to be extracted and re-used. Although the concept study indicated that the recapture and recompression system was technically feasible and commercially viable, the developers have not yet produced a prototype to test the efficacy and prove the commercial viability of this MBRDT primarily due to the lack of funding interest from the log and fumigation industries. Although the major issue with this MBRDT concept is the significant capital outlay, the commercial viability of the system was compelling due to the intrinsic value of the MB that could be reused combined with the closed-loop system that would preclude any residual by- products typically associated with alternative MBRDT technologies. Because the Biodesorb system concept also complements the current under-tarpaulin fumigation methods, no significant changes to current fumigation practices would be required.”
In addition to the above information received from L. Dear, R. Newson, Biovapor NZ (personal communication) said that “Biodesorb has determined to maintain their MBRDT concept without further financial input (e.g., building prototype equipment) until they can determine what direction the MB fumigation industry progresses”.
TIGG / Chemtura(R. Mack, USDA-APHIS, and J. Kearns, TIGG, personal communications) In the mid-1990s, Chemtura (formerly Great Lakes Chemical Corporation, the predominant MB manufacturer and distributor in the US) worked with the USDA and GFK Consulting to develop a system to mitigate emissions from fumigation chambers and enclosures by capturing methyl bromide on AC. The goal was to create a MBRDT that was safe, easy to operate, and consistent with USDA treatment schedules. The MBRDT was developed and proven in laboratory and pilot scale demonstrations before the first commercial unit was installed. TIGG (a subsidiary of Spencer Turbine and a manufacturer of steel tanks, pressure vessels and AC; https://tigg.com) provided the pilot scale systems for testing. Ultimately, Chemtura dropped out of the partnership and GFK Consulting is no longer in business, leaving TIGG to manufacture and sell the AC-based system.
The TIGG MBRDT is a static system that is attached to a fumigation chamber and the AC filters are sized to meet the fumigation chamber size, the maximum MB concentration used, and the USDA- required fumigation and aeration times. Currently, there are four TIGG units in operation in the US (one each in Hawaii, Texas, Mississippi, and California). Although TIGG receives three to five queries a year about their MBRDT, no units have been manufactured and sold since about 2007.
The primary reason for lack of sales, according to TIGG, is that the units tend to be cost-prohibitive.
Like Biodesorb, the TIGG / Chemtura technology is not amenable for use as a self-contained mobile unit that can move readily to each fumigated stack on the port.
TIGG / Chemtura was again reviewed in 2019 and found no advances in their systems that would permit them to be developed into self-contained portable units that could be used at a port facility to remove MB from fumigated log stacks.
The reviewer found that Genera is currently the only entity worldwide that is actively engaged in MBRDT research and development for the past seven years to find solutions, if possible, whereby the New Zealand log export industry can meet the October 2020 (ERMA 2010) recapture and/or