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National Emissions from Lawn and Garden EquipmentJamie L Banks, PhD, MS*Quiet Communities, Inc., PO Box 533, Lincoln, MA 01773Robert McConnell, Environmental EngineerUS Environmental Protection Agency, Region 1, 5 Post Office Square, Boston, MA 02109AbstractBackground: The contribution of gasoline-powered lawn and garden equipment (GLGE) to air pollutantemissions in the United States has not been extensively studied. Goal: Our goal is to provide annual USand state-level emissions estimates of volatile organic compounds (VOC): criteria pollutants (carbonmonoxide [CO], nitrogen oxides [NOx], particulate matter [PM] 10 microns, including PM 2.5microns [PM 10, PM2.5]; and carbon dioxide (CO2) from GLGE, with a focus on 2-stroke engines.Methods: Pollutant emissions data were extracted from the Environmental Protection Agency’s (EPA)2011 and 2018 modeling platform (version 6), for GLGE (Source Code Classifications2260004021 2265004071), and equipment population data were obtained from the EPA’s nonroadmodel. Data were sorted by equipment type and characteristics. Aggregate and equipment-specificemissions were calculated and compared with emissions from all gasoline-fueled nonroad equipment.Results are presented as descriptive statistics. Results: In 2011, approximately 26.7 million tons ofpollutants were emitted by GLGE (VOC 461,800; CO 5,793,200; NOx 68,500, PM10 20,700;CO2 20,382,400), accounting for 24% 45% of all nonroad gasoline emissions. Gasoline-poweredlandscape maintenance equipment (GLME; leaf blowers/vacuums, and trimmers, edgers, brush cutters)accounted for 43% of VOCs and around 50% of fine PM. Two-stroke engines were responsible for thevast majority of fine PM from GLME. State data (California, New York, Texas, Illinois, and Florida),2018 projections, and additional comparisons are presented. Methodological issues are discussed.Conclusions: GLGE accounts for a major portion of US nonroad gasoline emissions. Two-strokeengines are an important source of VOCs and criteria pollutants.*Corresponding Author: [email protected]

INTRODUCTIONGasoline-powered lawn and garden equipment (GLGE) ranging from string trimmers to stumpgrinders and tractors is a source of high levels of localized emissions that includes hazardous airpollutants, criteria pollutants, and carbon dioxide (CO2).1-4 Workers using commercial equipment areexposed when they are close to the emitting sources several hours each day, several days a week inseasons of use. Other members of the public, including children, may also be exposed to high levels ofemissions from commercial landscape maintenance equipment (GLME) such as leaf blowers, trimmers,and mowers, used routinely around residential neighborhoods, schools, parks, and other public spaces.The commercial landscape maintenance industry has experienced strong growth over the last 15 yearsand depends largely on gasoline-powered equipment for most tasks once performed manually. Thesefactors are raising concerns about the health impacts of GLGE emissions on workers and the public.Extensive evidence exists on the adverse health effects of exhaust emissions and other fineparticulates which include cardiovascular disease, stroke, respiratory disease, cancer, neurologicalconditions, premature death, and effects on prenatal development.5-13 Short term and long termexposures are implicated. However, GLGE as a source of these emissions has received little attention.Understanding the characteristics of GLGE and GLME emissions can help estimate potential healthimpacts of these close-to-the-source emissions.The goal of this study was to characterize annual emissions from GLGE at the national level andin selected states and to estimate the contribution of GLME to those emissions. Special attention is paidto 2-stroke GLME engines. The emissions contributions from the four of the five most populated statesare derived from the NEI, and for California, from the emissions inventory of the California AirResources Board (CARB).METHODSStudy DesignThe GLGE emissions analyzed are total volatile organic compounds (VOC) and individualVOCs (benzene, 1,3 butadiene, acetaldehyde, formaldehyde); criteria pollutants (carbon monoxide[CO], nitrogen oxides [NOx], particulate matter [PM] 10 microns, including PM 2.5 microns [PM10, PM2.5]); and carbon dioxide (CO2). Equipment pollutant data were extracted from SCC summaryreports from the EPA’s 2011 and 2018 modeling platform (version 6), and equipment population datawere obtained from the Nonroad model. GLGE included the equipment in TABLE 1 and identified bySource Code Classifications 2260004021 2265004071. The GLME subset is defined as leafblowers/vacuums; trimmers/edgers/brush cutters; and mowers. Groupings of equipment, eg, leafblowers/vacuums, were predefined by the NEI.“All Emissions” are defined as all emissions from stationary and mobile sources, excludingbiogenic and naturally occurring emissions. “All Nonroad Emissions” are defined as all emissions fromthe equipment types accounted for within the Nonroad model; note that this does not include emissionsfrom commercial marine, rail, and aircraft sources. “Gasoline Nonroad Emissions” are defined asemissions from gasoline fueled equipment accounted for within the Nonroad model. National emissionswere analyzed by type of equipment and engine configuration as shown in TABLE 1. All results arepresented as descriptive statistics.2

Table 1. Categorization scheme for analysis of GLGE emissionsType of EquipmentEngine ConfigurationGLMELeaf Blowers/Vacuums2 stroke, 4 strokeTrimmers/Edgers/Cutters2 stroke, 4 strokeMowers4 strokeOther GLGEChain Saws2 stroke, 4 strokeRotary Tillers2 stroke, 4 strokeSnowblowers2 stroke, 4 strokeTurf Equipment2 stroke, 4 strokeChippers/stump grinders4 strokeTractors4 strokeShredders4 strokeOther4 strokeAnalysesAll analyses except for the 2018 projections represent 2011 estimates.Equipment PopulationsThe national populations of all types of GLGE were obtained from the Nonroad model. Thecontribution of each type to the whole population was determined.Contributions of All Nonroad and GLGE SourcesAll Nonroad Emissions were compared to All Emissions. GLGE emissions were then calculatedand compared with All Nonroad Emissions and All Emissions.Contribution of Landscape Maintenance Equipment to GLGE EmissionsGLME emissions and their contribution to GLGE and All Nonroad Emissions were analyzed.Additional analyses were conducted to examine the relative contributions of 2-stroke GLME engineemissions.Projected Growth of GLGE Emissions: 2011 2018GLGE emissions projected for 2018 were obtained from the EPA’s 2018 modeling platform,version 6, and compared with 2011 emissions.GLGE Emissions in the Five Largest StatesState level emissions data from the five most populated states (US Census) – California, Florida,Illinois, New York, and Texas – were extracted and analyzed. Estimates of GLGE emissions forFlorida, Illinois, New York, and Texas were based on 2011 data from the EPA’s 2011 modelingplatform, version 6. Estimates of GLGE emission for California were based on data from the CARB’sOFFROAD2007 Model and estimated for 2012. No adjustments were made for potential differences inannual emissions between 2011 and 2012 California data. The program structure of the OFFROAD2007Model provides a general overview of the methodology used to estimate emissions from off-roadsources (http://www.arb.ca.gov/msei/offroad/pubs/offroad overview.pdf).3

Each state’s contribution to national GLGE Emissions was calculated and compared with itscontributions to the US landscape maintenance labor force and the US population. Labor force statisticswere sourced from the Bureau of Labor Statistics, May 2013 reports (www.bls.oes) and population datafrom the 2011 US Census.Nonroad Air Emissions ModelEPA developed a nonroad air emissions model in the 1990s to provide estimates of emissionsfrom most types of nonroad equipment, including construction equipment, recreational marine vessels,and lawn and garden equipment (LGE). The model is referred to simply as the “Nonroad” model, and ithas been updated a number of times since its creation. Documentation for the model exists as a numberof technical reports available on EPA’s website (http://www.epa.gov/otaq/nonrdmdl.htm). Totalemissions are determined by summing the exhaust and evaporative emission components.14, 15 Thepreponderance of emissions from Nonroad equipment occurs as exhaust emissions due to thecombustion of fuel. The methodologies for determining exhaust emissions are summarized below.Exhaust Emissions from Nonroad EnginesThe Nonroad model uses the following equation to calculate exhaust emissions from nonroadengines (ref: Median):Emissions (Pop) x (Power) x (LF) x (A) x (EF)Where Pop Engine populationPower Average Power (hp)LF Load factor (fraction of available power)A Activity (hrs/yr)EF Emission factor (g/hp-hr)The derivation of the default model data for each factor from the above equation is discussedbelow.a.Equipment populations and average power (horsepower)The technical report titled “Nonroad Engine Population Estimates”16 indicates that equipmentpopulation data for most types of equipment were obtained from Power Systems Research, anindependent marketing research firm, although in some instances other data source were used. Ofinterest for this analysis, for many LGE categories EPA used sales data obtained from equipmentmanufacturers during the development of its Phase 1 emission standards for small (less than 25 hp)gasoline fueled nonroad engines. This was done for the following LGE categories: lawn mowers,trimmers/edgers/brush cutters, leaf blowers/vacuums, and chainsaws. The report notes that anequipment population base year of either 1996 or 1998 was used for the LGE types.Once estimates of equipment populations were derived, information obtained by the state ofCalifornia was used to divide the equipment between the residential and commercial sectors. This stepwas needed because of the large difference in usage patterns between these two sectors. TABLE 2below contains an extract of data from Table 3 of the Nonroad Engine Population report mentionedabove, and illustrates how the split between residential and commercial equipment was apportioned for anumber of LGE types.4

Table 2. Percentage split between residential and commercial equipmentSCC codeApplication22xx004010 Lawn mowers22xx00401122xx004025 Trimmers/edgers/cutters22xx00402622xx004020 Chainsaws22xx00402122xx004030 Leaf ential(% of equipmentpopulation)All96.30-1 hp1-3 hp 3 hp0-1 hp1-3 hp 3 hp0-1 hp1-3 hp 3 hp10085.3010097.0010092.50Commercial(% ofequipmentpopulation)3.7014.71000310007.5100i. Geographic allocation of residential LGE Populations (except snowblowers)The Nonroad model uses US Census data on one and two unit housing to allocate nationalequipment populations to the county level. The population documentation report mentioned above notesthat other variables are likely to also affect the distribution of LGE population, such as average yardsize. However, no consistent, reliable data surrogates could be found to apportion the national levelequipment populations based on these alternative factors, and so the model relies solely upon US Censusdata on one and two unit housing to allocate national LGE population data to the county level.ii. Geographic allocation of commercial L&G Equipment Populations (except snowblowers)The Nonroad model uses the number of employees in the landscaping services industry to disaggregate national level LGE population data to the county level. This was accomplished using datafrom the North American Industry Classification System (NAICS); specifically, for NAICS code561730, landscaping services.iii. Equipment population projectionsThe Nonroad model enables the user to obtain estimates of emissions for years other than thebase year used for equipment populations. This is accomplished by the development of processes tohandle the growth in equipment populations due to the purchase of new equipment as years pass, andadjustments made to account for the scrappage of old equipment. The reader is referred to the EPAtechnical reports “Nonroad Engine Growth Estimates,”17 and “Calculation of Age Distributions in theNonroad Model – Growth and Scrappage”18 for further information on these topics. Both of thesereports are available on the EPA website (http://www.epa.gov/otaq/nonrdmdl.htm).b.Activity levels and load factors.Equipment populations and horsepower levels alone are not sufficient for determining emissionsfrom nonroad equipment; assumptions about frequency and patterns of use must also be made. TheEPA report, “Median Life, Annual Activity, and Load Factor Values for Nonroad Engine EmissionsModeling”19 describes how the Nonroad model assigns default activity levels, in hours per year, and5

load factors in performing its calculations. Load factors are needed to account for the fact thatequipment is not typically used at full power 100% of the time; load factors reflect that and arepresented in terms of average percent of full power for the equipment as it is used. The activity levelsand load factors for small ( or to 25 hp) spark-ignition engines for many LGE types was taken fromdata supplied to EPA during the comment period for the regulation of these engines. TABLE 3 belowcontains an extract of the default activity data, in annual hours of equipment use, and load factor data,expressed as fraction of full power, taken from Table 6 of the above mentioned report.Table 3. Example default activity levels and load factors for LGEEquipment typeUseLawn dgers/CuttersLeaf blowers\VacuumsChainsawsActivity level(Annual hours)2540691371028213303Load factor(fraction of fullpower)0.330.330.910.910.940.940.700.70c. Emission