Emission factors of industrial boilers burning biomass-derived fuels

Figures & data

Table 1. Summary of data sources obtained in this research for biomass boiler combustion as compared to AP-42 for wood residue combustion. Timeframe refers to the time when the data were collected, not the years in which the boiler was set up.

EPA’s AP-42 Database	Data Obtained and Compiled in This Research
EPA’s AP-42 Chapter 1.6: “Wood Residue Combustion in Boiler” (published 2003) Timeframe: 1975–1995 Source emission testing and sampling records from various wood-fired combustion units	Stack Test Data POET Biorefining (Project Liberty, Iowa) stack test data (published 2015, 2016, 2017, 2019) Timeframe: 2015–2019 Wisconsin Electric (We) Energies stack test data and air permit application (published 2019) Timeframe: 2019
	Air Permits Abengoa Bioenergy Biomass of Kansas (ABBK) air permit and application (published 2011 and 2014) Timeframe: 2011 and 2014 We Energies stack test data and air permit application (published in 2019) Timeframe: 2019
	NCASI Technical Reports Comprehensive compilation and review of wood-fired boiler emissions (published 2013) Timeframe: 2009–2012 Comprehensive compilation and review of wood-fired boiler emissions (published 2015) Timeframe: 2012 and later Compilation of “air toxic” and total hydrocarbon emissions data for pulp and paper mill sources: a second update (published 2010) Timeframe: 2004 and before Methane and nitrous oxide emissions from biomass-fired boilers and recovery furnaces (published 2012) Timeframe: 2009
	EPA’s CEDRI database
	○ Timeframe: Unknown
	CORRIM survey on emission factors from wood-fired boilers (published 2017)
	○ Timeframe: 2012

Figure 1. Summary of emission factors for aerosol, gaseous, and hazardous air pollutants from stack testing data.

Table 2. Summary of operating information from stack test data sources.

Data Source	Boiler Capacity (MMBtu/hr)	Boiler Feed	Control Technology	Year of Stack Test
POET Biorefining	267	Biomass, biogas, digester sludge, filter cake, syrup, biomass fines, and net wrap	Selective non-catalytic reduction (SNCR), flue gas desulfurization, baghouse	2016, 2017, 2019
	125			2015
We Energies	500	Logging residue, wood, bark, wood waste, forest residues, wastewater sludge (NG at startup)	SNCR, baghouse	2019

Figure 2. Emission factors used for air permits and air permit applications for selected pollutants.

Table 3. Summary of operating information from air permit data sources.

Data Source	Boiler Capacity (MMBtu/hr)	Boiler Feed	Control Technology	Year of Permit
Abengoa Bioenergy Biomass of Kansas	500	Lignin, hydrolysis residual stillage syrup, biomass, biogas, and sludge	Selective non-catalytic reduction (SNCR), scrubber, baghouse	2011
We Energies	800	Logging residue, wood, bark, wood waste, forest residues, wastewater sludge (NG at startup)	SNCR, baghouse	2019

Figure 3. Emission factors for selected pollutants based on the data reported in NCASI technical bulletins. Data for “MACT testing” and the “pulp and paper” do not indicate feed type because these emission factors are based on data from several boilers where the feed composition is not uniform.

Figure 4. Emission factors for PM₁₀, PM_2.5, selected HAPs, and gaseous pollutants that are calculated from data reported by CORRIM. Y-axis units are lb/MMBtu. The data sources refer to 12 individual wood mills (wood production facilities) surveyed by CORRIM in the Pacific Northwest and Southeast United States. (Note that details about individual mills are not available since these were considered business confidential information.)

Figure 5. Distribution of biomass-fueled boiler emission factors from collected data sources for each pollutant and inclusive of all fuels. Whiskers correspond to 5^th and 95^th percentiles, with means shown as black squares, medians as horizontal lines, and emission factors from EPA’s AP-42 as red dots. The number of data points used for each pollutant are also shown (n). These box plots report uncontrolled emission factors and thus do not include the CORRIM data.

Table 4. Range and median emission factors (lb/MMBtu) from data sources collected herein including air permits, stack test data, and industry research reports as compared to EPA’s AP-42 values, disaggregated by fuel type.

Pollutant	EPA’s AP-42 (lb/ MMBtu)	Emission Factors (lb/MMBtu)
		Wood and Wood Residues^[a]		Sludge^[a]	Wood Residues and Sludge		Biomass Waste^[a]
		Range^[b]	Median	Point Estimate^[c]	Range^[b]	Median	Range^[b]	Median
PM^f	0.56	0.33–0.56	0.40	0.26	0.40–4.36	0.41	0.73–7.5	7.39
PM10	0.5	0.30–0.36	0.36	n/a	0.40–4.36	0.40	6.0–7.0	6.89
PM2.5	0.43	0.25–0.43	0.30	0.19	0.40–4.36	0.38	5.8–6.0	6.0
PM^c	0.017	0.009	0.009	0.006	0.018–0.06	0.04	0.005–0.02	0.017
SO2	0.025	0.13	0.13	n/a	0.02–0.51	0.02	0.49–2.65	2.35
NOx	0.22	0.79	0.79	n/a	0.12–0.67	0.37	0.08–0.76	0.70
CO	0.6	0.72	0.72	n/a	0.02–0.39	0.10	0.002–0.22	0.22
VOC	0.017	0.004	0.004	0.003	0.017	0.017	0.013–0.019	0.017
H2SO4	n/a	n/a	n/a	n/a	0.002	0.002	0.10–0.16	0.15
NH3	n/a	n/a	n/a	n/a	n/a	n/a	0.013	0.013
CO2	195	n/a	n/a	n/a	210–225	218	216	216
Acetaldehyde	8.3E-04	2.7E–04–2.8E-04	2.7E-04	n/a	n/a	n/a	8.3E–04–2.0E-03	1.3E-03
Formaldehyde	4.4E-03	1.0E–03–4.4E-03	2.5E-03	1.3E-04	3.0E–05–5.8E-04	1.3E-04	2.0E–04–4.4E-03	2.3E-03
HCl	1.9E-02	1.6E–03–1.2E-02	6.9E-03	6.7E-02	1.5E–03–2.7E-01	1.6E-02	2.6E-01	2.6E-01
HF	n/a	1.4E-04	1.4E-04	6.4E-04	8.5E–04–1.0E-03	9.2E-04	3.0E-04	3.0E-04

lb/MMBtu = pounds per million British Thermal Unit, PM^f = particulate matter (filterable), PM₁₀ = PM with diameter less than or equal to 10 micrometers, PM_2.5 = PM with diameter less than or equal to 2.5 micrometers, SO₂ = sulfur dioxide, NO_x = nitrogen oxides, CO = carbon monoxide, VOC = volatile organic compounds, H₂SO₄ = sulfuric acid, NH₃ = ammonia, CO₂ = carbon dioxide, HCl = hydrogen chloride, HF = hydrogen fluoride, n-a = not available.

^[a]Wood and wood residues include bark, dry/wet wood, logging residue, and wood waste, whereas sludge refers to wastewater treatment sludge. Biomass waste includes biomass, biogas, digester sludge, biomass fines, and lignin stillage.

^[b]For several pollutants, the range is not reported due to lack of emission factor data from multiple sources. In this case, only a point estimate is included.

^[c]A point estimate is included where only one data source is available.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.