Particulate matter pollution from open burning of sawdust in Southwestern Nigeria

Figures & data

Figure 1. Typical heap of sawdust at a sawmill in southwestern Nigeria

Figure 2. Map of Nigeria showing the study area.

Table 1. Estimated annual quantity of sawdust generated and burnt in southwestern Nigeria

State	Number of sawmills^a	Sawdust generated^a (ton/year)	Sawdust burnt^b (ton/year)	Estimated PM loading (ton/year)
Lagos	700	186.567	179104.32	8.2925
Ogun	300	79.957	76758.72	3.5539
Oyo	320	85.287	81875.52	3.7908
Ondo	311	82.889	79573.44	3.6843
Osun	245	65.298	62686.08	2.9024
Ekiti	100	26.652	25585.92	1.1846
Southwest	1976	526.650	505584.00	23.4085

^a Okedere (2016).

^b Based on 96% open burning of sawdust (Ogunbode et al., 2013).

Table 2. Concentrations and emission factors of PM from the samples

Sample	W2 − W1 (g)	W2 − W1 (g)	Mean (g)	Time (s)	PM (mg/m^3)	Emission factor (g/kg)
1	0.0009	0.0011	0.001	100	1000.0000	0.0100
2	0.0013	0.0017	0.0015	95	1578.9474	0.0150
3	0.001	0.0101	0.00555	105	5285.7143	0.0555
4	0.0001	0.0106	0.00535	110	4863.6364	0.0535
5	0.0001	0.0136	0.00685	110	6227.2727	0.0685
6	0.0001	0.0028	0.00145	95	1526.3158	0.0145
7	0.0002	0.0153	0.00775	94	8244.6809	0.0775
8	0.0025	0.0012	0.00185	105	1761.9048	0.0185
9	0.0008	0.0047	0.00275	85	3235.2941	0.0275
10	0.0008	0.0012	0.001	96	1041.6667	0.0100
11	0.0004	0.0101	0.00525	95	5526.3158	0.0525
12	0.0002	0.0105	0.00535	100	5350.0000	0.0535
13	0.0093	0.0101	0.0097	95	10210.5263	0.0970
14	0.0101	0.0061	0.0081	85	9529.4118	0.0810
15	0.0013	0.0012	0.00125	80	1562.5000	0.0125
16	0.0004	0.0104	0.0054	90	6000.0000	0.0540
17	0.0007	0.0101	0.0054	91	5934.0659	0.0540
18	0.0005	0.0106	0.00555	100	5550.0000	0.0555
19	0.0005	0.0108	0.00565	100	5650.0000	0.0565
20	0.0007	0.0109	0.0058	100	5800.0000	0.0580
Mean				96.55	4793.913	0.0463

Table 3. Mean elemental emissions obtained by AAS

Sample	Mean elemental composition of PM (mg/kg)
	Na	K	Ca	Mg	Mn	Fe	Zn	Cu	Ni	Pb	Cr	Hg
1	30.125	25.241	0.009	0.013	0.007	0.018	0.042	0.008	0.010	0.000	0.007	0.000
2	30.214	35.322	0.035	0.009	0.016	0.036	0.030	0.011	0.019	0.002	0.002	0.000
3	20.341	40.241	0.041	0.022	0.027	0.046	0.003	0.022	0.003	0.008	0.013	0.001
4	10.245	20.422	0.025	0.018	0.039	0.022	0.022	0.016	0.007	0.004	0.017	0.000
5	35.125	30.912	0.017	0.026	0.014	0.024	0.020	0.007	0.027	0.002	0.009	0.004
6	20.217	20.272	0.013	0.017	0.027	0.028	0.006	0.019	0.024	0.002	0.005	0.002
7	15.321	10.123	0.022	0.031	0.034	0.042	0.049	0.023	0.008	0.002	0.002	0.010
8	30.243	20.712	0.031	0.022	0.029	0.03	0.015	0.015	0.03	0.009	0.019	0.005
9	12.422	10.134	0.033	0.015	0.032	0.033	0.024	0.032	0.023	0.005	0.025	0.000
10	20.134	20.124	0.005	0.011	0.025	0.014	0.013	0.009	0.029	0.002	0.022	0.000
11	15.412	25.151	0.012	0.025	0.036	0.011	0.007	0.025	0.032	0.004	0.028	0.000
12	14.391	30.333	0.029	0.007	0.021	0.050	0.016	0.012	0.036	0.004	0.034	0.003
13	25.124	10.342	0.032	0.033	0.033	0.047	0.044	0.017	0.025	0.000	0.03	0.001
14	20.323	10.426	0.024	0.029	0.012	0.044	0.033	0.029	0.006	0.006	0.036	0.006
15	12.427	20.512	0.037	0.005	0.023	0.048	0.041	0.034	0.021	0.008	0.029	0.000
16	10.114	10.125	0.039	0.012	0.037	0.035	0.017	0.018	0.034	0.003	0.033	0.002
17	20.235	20.812	0.043	0.035	0.042	0.043	0.039	0.021	0.038	0.004	0.024	0.000
18	25.125	12.613	0.038	0.037	0.039	0.029	0.032	0.013	0.02	0.007	0.037	0.004
19	18.404	15.823	0.027	0.019	0.045	0.032	0.047	0.016	0.028	0.003	0.013	0.000
20	14.235	20.347	0.036	0.024	0.048	0.036	0.045	0.022	0.026	0.006	0.026	0.002
Mean	20.0089	20.4994	0.0274	0.0205	0.0293	0.0334	0.0273	0.0185	0.0223	0.0041	0.0206	0.0020

Table 4. Estimated annual elemental loading from burning of sawdust

State	Ton/year
	Sawdust burnt	Na	K	Ca	Mg	Mn	Fe	Zn	Cu	Ni	Pb	Cr	Hg
Lagos	179104.32	3.5837	3.6715	0.0049	0.0037	0.0052	0.0060	0.0049	0.0033	0.00399	0.00073	0.00369	0.0004
Ogun	76758.72	1.5359	1.5735	0.0021	0.0016	0.0022	0.0026	0.0021	0.0014	0.00171	0.00031	0.00158	0.0002
Oyo	81875.52	1.6382	1.6784	0.0022	0.0017	0.0024	0.0027	0.0022	0.0015	0.00183	0.00034	0.00169	0.0002
Ondo	79573.44	1.5922	1.6312	0.0022	0.0016	0.0023	0.0027	0.0022	0.0015	0.00177	0.00033	0.00164	0.0002
Osun	62686.08	1.2543	1.2850	0.0017	0.0013	0.0018	0.0021	0.0017	0.0012	0.0014	0.00026	0.00129	0.0001
Ekiti	25585.92	0.5119	0.5245	0.0007	0.0005	0.0007	0.0009	0.0007	0.0005	0.00057	0.0001	0.00053	0.0001
Southwest	505584	10.1162	10.3642	0.0139	0.0104	0.0148	0.0169	0.0138	0.0094	0.01127	0.00207	0.01042	0.0010

Table 5. Per capita and land distributions of PM

State	Per capita	Land distribution
	g/capita	g/km^2
Lagos	0.910	2258.921
Ogun	0.947	216.701
Oyo	0.679	143.049
Ondo	1.065	232.889
Osun	0.849	321.560
Ekiti	0.494	217.958
Southwest	0.844	304.592

Figure 3. Electricity generation capacities of southwestern Nigeria States from sawdust.

Okedere, O. B. (2016) An assessment of air emissions from open burning of some common southwestern Nigeria wood dust in the country’s energy mix (Unpublished PhD Thesis). Department of Chemical Engineering, Obafemi Awolowo University, Ile-Ife, Nigeria.

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Ogunbode, E. B., Fabunmi, F. O., Ibrahim, S. M., Jimoh, I. O., & Idowu, O. O. (2013). Management of Sawmill wastes in Nigeria: Case study of Minna, Niger State. Greener Journal of Science, Engineering and Technology Research, 3, 34–41.10.15580/GJSETR

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