Emission factors of fine particulate matter, organic and elemental carbon, carbon monoxide, and carbon dioxide for four solid fuels commonly used in residential heating by the U.S. Navajo Nation

Figures & data

Figure 1. Navajo homestove with firebox dimensions.

Table 1. Reported characterization and heating values of fuels tested (% dry-basis and BTU/lb).

	Volatile matter		Fixed carbon		Ash		Higher heating value		Lower heating value^a
Fuel	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD^b	Source(s)^c
Ponderosa pine	82.2	0.42	16.8	0.64	1.0	1.0	8630	26	6430	50	1, 2
Utah juniper	82.8	na	15.1	na	2.0	na	8660	na	6430	10	3
Black Mesa	43.3	2.3	48.8	1.2	8.0	2.5	11,100	380	8880	10	4, 5
Fruitland	39.3	2.7	43.6	2.8	17.3	5.2	10,620	790	8420	10	4

^aThe relationship between lower heating values (LHVs) and higher heating values (HHVs) was defined by the Intergovernmental Panel on Climate Change (2006) and based on reported fuel hydrogen and oxygen contents (Table S2) and measured moisture contents.

^bThe variability (i.e., standard deviations) reported for LHVs was from variation in measured fuel moisture contents. LHV standard deviation (SD) was lower than HHV SD for the coal types, since LHVs were based on reported mean HHVs. That is, the mean HHVs were from numerous sources and varied for coal, whereas LHVs varied solely on the moisture contents determined in this study.

^cSources: 1, Gaur and Reed (1998); 2, Overend et al. (2012); 3, Chen et al. (2012); 4, Affolter (2000); 5, Arizona Bureau of Mines (1977).

Figure 2. Schematic of CUEST experimental facility.

Figure 3. Overview of phases and equations for mEF_i and eEF_i, where i = PM_2.5, OC, EC, CO, and CO₂.

Table 2. Test phase conditions.

	Ponderosa pine		Utah juniper		Black Mesa		Fruitland
Parameter	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Replicates (n)	5	na	4	na	4	na	4	na
Fuel load (kg)	1.29	0.01	1.29	0.01	0.65	0.01	0.64	0.01
Duration (min)	28	6	44	10	98	20	77	19
Stove flue temperature (°C)	480	94	353	90	165	65	202	91
Fuel load remaining at end (%)	0	na	0	na	52	20	55	20

Table 3. Mass emission factors, mEF_i (in g/kg), for PM and other compounds emitted during the test phase.

	PM2.5		OC		EC		CO		CO2
Fuel	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Ponderosa pine	1.09	0.578	0.538	0.325	0.206	0.178	27.2	13.1	1470	234
Utah juniper	1.68	0.207	1.04	0.278	0.183	0.072	40.4	10.9	1540	131
Black Mesa	14.1	7.08	9.30	5.09	0.471	0.366	226	67.8	2424	368
Fruitland	13.3	2.18	7.07	0.757	0.451	0.285	204	22.7	2484	210

Notes. Bold indicates statistically higher mEF_i (i = PM_2.5, OC, EC, CO, and CO₂) for coal fuels (Black Mesa and Fruitland) compared with wood (Ponderosa pine and Utah juniper) at a significance level (α) of 0.05.

Table 4. Energy emission factors, eEF_i (in mg/MJ) for cycle.

	PM2.5		OC		EC		CO		CO2
Fuel	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Ponderosa pine	105	50.3	54.5	28.5	15.5	8.8	2108	897	105,710	8760
Utah juniper	163	12.5	100	10.8	11.6	3.1	2849	567	105,040	6660
Black Mesa	320	89.4	201	66.6	18.3	6.8	5195	813	117,740	8800
Fruitland	323	13.6	174	20.5	18.2	5.6	5123	871	122,860	6040

Note. Bold indicates statistically higher eEF_i (i = PM_2.5, OC, EC, CO, and CO₂) for coal fuels (Black Mesa and Fruitland) compared with wood (Ponderosa pine and Utah juniper) at a significance level (α) of 0.05.

Figure 4. PM_2.5 and CO EFs for (a) Test phase with natural log–transform and linear fit for mEFs, and (b) Pre-burn and Test phases combined (Cycle) with linear fit for eEFs. The shaded region in (a) is EPA-suggested PM₁₀ and CO mass emission factors for a conventional residential wood stove (EPA, 1996). The vertical dashed lines represent mEFs and eEFs previously reported for these fuels and summarized in Tables S3 and S5.

Figure 5. Elemental and organic carbon profiles during Test phase for (a) ponderosa pine, (b) Utah juniper, (c) Black Mesa, and (d) Fruitland.

Figure 6. Real-time Test phase (a, b) CO and (c, d) TSP concentrations and (e, f) MCE: mean concentration (solid line) or percent efficiency (dashed line). Standard deviation of all Test phases for each fuel is plotted as shaded region. Dotted line in each MCE plot represents transition from flaming to smoldering combustion (90%).

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