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1 Technical Comments on Bill 36-0232 1 Controlled Incineration of Vegetative Debris 2 3 Good morning Senator Avery L. Lewis, Chaiman of the Committee on Government 4 Operation, Veterans Affairs, and Consumer Protection, other committee members of the 5 36th Legislature of the Virgin Islands, and those in the audience. 6 My name is Greg Guannel, and I’m the Director of the Caribbean Green Technology Center 7 at the University of the Virgin Islands. We develop and share knowledge on how 8 infrastructure, ecosystems, and institutions interact in the U.S. Virgin Islands, with the goal 9 of supporting more resilient and sustainable development. 10 Thank you for the opportunity to provide comments on Bill 36-0232. My goal in this 11 testimony is to provide technical context on the proposed use of controlled incineration 12 technologies for vegetative debris disposal. In preparing these comments, I reviewed 13 information on how air-curtain incinerators operate, how they are used in other 14 jurisdictions, and the operational considerations associated with their use. My comments 15 focus on several topics: the technology itself and how it is typically used, potential air- 16 quality considerations, the influence of weather and site location, operational and cost 17 considerations, and how other jurisdictions, including Puerto Rico and several Caribbean 18 islands, manage vegetative waste. I will also highlight several technical considerations in 19 the bill related to monitoring, setbacks, and operational safeguards. These comments are 20 intended to provide technical context to support informed decision-making and are not 21 intended to advocate for or against the proposed approach. 22 1 Purpose of the Bill 23 Bill 36-0232 proposes to amend Act 8018 to allow the Virgin Islands Waste Management 24 Authority (WMA) and landfill operators to dispose of vegetative debris using controlled 25 incineration technologies, including air‑curtain incinerators (ACIs). The bill also states that 26 other methods such as composting, mulching, and shredding remain permissible options. 27 Air‑curtain incinerators are widely used in the United States to rapidly reduce large volumes 28 of vegetative debris, particularly after storms and land‑clearing operations. 29 The bill also allows private individuals to burn vegetative debris generated on their property 30 with a permit from the Virgin Islands Fire Service. 31 Private burning must occur 50 ft from any structure, or 15 ft from any structure if using an 32 approved closed‑top burner. 33 Burning must be attended and conducted during favorable atmospheric conditions. 34 2 2 Description of Technology 35 An air‑curtain incinerator burns vegetative debris in a trench or refractory chamber while a 36 blower forces a high‑velocity air curtain over the burn pit. 37 The air curtain pushes smoke and particles back into the flame, increasing combustion 38 efficiency and reducing visible smoke compared with open pile burning. 39 Burning reduces debris volume by approximately 90–95% and significantly reduces 40 particulate emissions compared with open burning. Burning produces ash equal to 41 approximately 5–10% of the original debris mass, which is transported to a landfill for 42 disposal. 43 The burning of vegetative debris does generate emissions, especially fine particulate matter 44 and Nitrogen Oxides (NOx). Carbon monoxide and other gases are generally present at 45 lower levels and are not usually the dominant air‑quality concern for vegetative debris 46 burning. 47 3 Typical Uses of the Technology 48 Air‑curtain burners are used in several U.S. states, including Florida and Texas, particularly 49 for hurricane debris management, forestry debris, land‑clearing waste. However, these 50 states do not rely exclusively on burning for vegetative waste management. Municipal 51 programs also use grinding, mulch production, or composting. 52 In most jurisdictions, air-curtain incinerators are used intermittently rather than as a 53 continuous, year-round disposal method. Burning is often used when debris volumes 54 exceed grinding capacity, large woody material is difficult to process, or debris must be 55 reduced quickly to maintain landfill capacity. This happens after, for example, hurricanes. 56 It is sometimes suggested that air-curtain incinerators could be used to produce biochar,. 57 Biochar is a carbon-rich material produced by heating biomass under low-oxygen 58 conditions (pyrolysis), which preserves carbon in a stable solid form rather than converting 59 it to carbon dioxide through combustion. When amended to soil, it increases nutrient 60 availability while improving water retention and soil structure. However, from my 61 understanding, creating biochar from ACI would require significant changes to their 62 operation, including reducing oxygen supply and interrupting the combustion process. 63 Biochar production requires low-oxygen conditions and controlled temperatures (typically 64 750-1,300°F), whereas air-curtain incinerators operate at higher temperatures (1,500– 65 2,000°F) with forced airflow to achieve complete combustion. Producing char would 66 therefore require restricting oxygen, controlling burn temperatures, and removing material 67 before full combustion, which can reduce efficiency, increase smoke emissions, and 68 introduce additional operational and safety constraints. As a result, air-curtain incinerators 69 are not typically used as a reliable or controlled method for biochar production. 70 3 Producing biochar from air-curtain incinerators would also increase operational complexity 71 and staffing requirements, as it would require continuous monitoring of burn conditions, 72 removal of partially charred material, and controlled cooling to prevent re-ignition. These 73 steps go beyond typical ACI operation, which is generally designed for continuous 74 combustion and minimal handling of residual material. 75 4 Air Quality Impacts 76 Air quality is the primary environmental issue associated with vegetative debris burning and 77 often determines whether communities accept or oppose burn operations. Smoke plumes 78 from debris burning can affect areas approximately 0.2 to over 1 mile downwind depending 79 on wind speed and atmospheric conditions. 80 The most important pollutant associated with vegetative burning is fine particulate matter 81 (PM2.5). EPA has established health-based air quality standards, including 35 µg/m³ over 82 24 hours, and 9 µg/m³ annually. 83 Health impacts associated with PM2.5 exposure include: 84 • Short‑term: 85 • asthma attacks 86 • respiratory irritation 87 • eye irritation 88 • increased emergency room visits 89 • Long‑term: 90 • cardiovascular disease 91 • chronic respiratory disease 92 • increased mortality risk 93 • Monitoring methods commonly include: 94 • EPA Method 9 smoke‑opacity monitoring (10–20% limits) 95 • portable PM2.5 monitors downwind of burn sites 96 Vegetative burning also produces nitrogen oxides (NOx) and volatile organic compounds 97 (VOCs). In sunlight these gases can react to form ground‑level ozone, which can be 98 dangerous if they exceed certain EPA thresholds (EPA 8‑hour ozone standard: 70 ppb). 99 However, ozone formation typically occurs on regional scales, whereas PM2.5 exposure 100 occurs locally near burn sites. For vegetative debris burning, PM2.5 is usually the dominant 101 local air‑quality concern. 102 Air‑quality impacts depend strongly on wind speed and atmospheric stability. Lower wind 103 speeds reduce pollutant dispersion and can increase smoke accumulation if burning 104 occurs frequently. Typical debris‑burn permits require a minimum wind speed of 105 approximately 5 mph, and burning suspended if winds exceed 15–20 mph 106 4 Large states such as Texas and Florida often operate burn sites in rural areas with large 107 buffer distances from homes. 108 Wind observations in the territory frequently show very low wind speeds (<1 m/s) overnight 109 and early morning, followed by stronger winds during the afternoon sea‑breeze period. 110 Furthermore, Caribbean trade winds weaken during August–October, which are also the 111 hottest months of the year. This means that burning during these months may increase the 112 likelihood of smoke accumulation and exposure for nearby communities. 113 5 EPA Regulation Updates 114 Air-curtain incinerators that burn clean vegetative debris are regulated under U.S. EPA rules 115 (40 CFR Part 60), which establish limits on emissions and operating conditions. These rules 116 require that units burn only clean vegetative material, comply with visible emission 117 (opacity) limits (typically around 10% using EPA Method 9), and maintain operational 118 records, including the type of material burned and periods of operation. 119 Under the Clean Air Act, facilities that emit more than approximately 100 tons per year of 120 criteria pollutants, or 10 tons per year of a single hazardous air pollutant (or 25 tons per year 121 combined), are classified as “major sources” and are subject to more stringent permitting 122 requirements. Emissions are typically estimated based on the total amount of material 123 burned per year using standard emission factors. 124 In 2024, EPA updated its rules to remove certain federal permitting requirements 125 (specifically Title V permits) for air-curtain incinerators that burn only clean vegetative 126 debris and operate below these thresholds. However, these units must still comply with 127 opacity limits, material restrictions, and recordkeeping requirements. If non-vegetative or 128 contaminated materials are burned, the unit may be subject to more stringent federal 129 standards. 130 EPA has also established provisions that allow expanded use of debris burning during 131 declared emergency conditions, such as hurricane recovery, where permitting 132 requirements may be streamlined to facilitate rapid debris removal. These provisions are 133 specific to emergency situations and differ from routine, ongoing operations. 134 6 Cost and Operational Considerations 135 This method requires both upfront capital investment and ongoing operational and 136 maintenance costs. 137 Typical costs associated with air‑curtain burning include equipment purchase ($70,000 – 138 $300,000 per unit), operational costs (e.g., blower fuel, trained operators, maintenance) as 139 well as insurance. Some programs have reported insurance premiums exceeding $100,000 140 per year due to wildfire and liability classifications. 141 5 Furthermore, burn pits must be attended continuously during operation. Ash (5–10% of 142 original debris mass) must still be transported to landfills. 143 7 Other Considerations 144 The bill establishes setback distances for private burning (50 ft from structures, 15 ft if 145 using an approved closed‑top burner). However, other jurisdictions often include additional 146 details, such as setback distances in the range of 50–100 ft. Furthermore, the bill does not 147 currently define maximum pile size or burn volume for private burning. Other jurisdictions 148 have typical guidelines of: 149 • maximum pile diameter: 3–8 ft 150 • maximum pile height: 3–6 ft 151 • maximum burn volume: <1 cubic yard 152 • burn duration limited to same‑day burning 153 Also, I noted that the bill specifies vegetative debris but does not describe procedures to 154 ensure burn material is free of non‑vegetative contaminants. If vegetative debris becomes 155 mixed with treated wood, plastics, painted materials, or household waste, combustion can 156 release additional toxic pollutants including dioxins, and heavy metals. 157 It may also be important to clarify whether marine biomass such as sargassum is included 158 in the definition of vegetative debris. Unlike terrestrial vegetation, sargassum can 159 accumulate trace metals from seawater, particularly arsenic, with measured 160 concentrations in Caribbean samples often ranging from 30–120 mg/kg (dry weight). When 161 biomass containing metals is burned, these elements do not disappear but instead 162 concentrate in the remaining ash or may be emitted in fine particulate matter. Sargassum 163 also contains high levels of salt (sodium and chloride), which can affect combustion 164 processes and increase corrosion in equipment. For these reasons, several Caribbean 165 jurisdictions treat marine biomass separately from land-based vegetative debris when 166 evaluating disposal or processing options. 167 Many jurisdictions therefore require debris inspection and separation procedures before 168 burning. 169 Furthermore, the bill authorizes controlled burning but does not specify: 170 • setback distances for WMA or landfill operations 171 • meteorological operating limits 172 • air‑quality monitoring requirements 173 • contamination control procedures 174 Many jurisdictions address these issues through operational permits or regulations. 175 8 Alternative Green‑Waste Management Programs 176 Many jurisdictions manage routine vegetative debris through grinding, mulching, and 177 composting. 178 6 These methods produce materials used for landscaping, soil improvement, erosion control, 179 or agriculture. The thinking is that composting preserves biomass and produces a usable 180 soil product, whereas burning converts biomass into ash. 181 Puerto Rico has established composting and mulching programs. After Hurricane María, 182 mulching operations processed approximately 5,000–6,000 cubic yards of vegetative debris 183 per day. In the rest of the Caribbean, St. Lucia promotes household composting and 184 organic waste diversion, Barbados operates green‑waste composting facilities, the 185 Cayman Islands have grinding and mulch distribution programs. Other islands have or 186 promote similar programs. However, they do burn when volumes exceed the capacity of 187 their operations. 188 9 Conclusion 189 Air‑curtain incinerators are effective at rapidly reducing large volumes of vegetative debris, 190 particularly after storms or land‑clearing operations. At the same time, combustion 191 produces particulate emissions that can affect nearby communities under certain 192 meteorological conditions. 193 For this reason, many jurisdictions combine debris burning with other methods such as 194 grinding, mulching, and composting, and establish operational safeguards including 195 setback distances, monitoring, and debris separation procedures when burning occurs 196 near populated areas. 197