Journal of Environmental Protection, 2013, 4, 83-98
http://dx.doi.org/10.4236/jep.2013.48A1011 Published Online August 2013 (http://www.scirp.org/journal/jep)
83
Air Quality Impacts of Smallholder Oil Palm Processing in
Nigeria
Elijah I. Ohimain1*, Sylvester C. Izah1, Stephen O. Abah2
1Bioenergy and Environmental Biotechnology Research Unit, Department of Biological Sciences, Faculty of Science, Niger Delta
University, Wilberforce Island, Nigeria; 2Department of Community Health, Faculty of Clinical Sciences, College of Medicine,
Ambrose Alli University, Ekpoma, Nigeria.
Received May 18th, 2013; revised June 26th, 2013; accepted August 2nd, 2013
Copyright © 2013 Elijah I. Ohimain et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Air emissions during palm oil processing by smallholders are issues of public health concern demanding urgent inter-
vention by environmentalist. In this study, six smallholder oil palm processing mills were studied in Elele, Nigeria. Air
emission parameters (NO2, NH3, CO, H2S, SO2, VOC), noise and meteorology (wind speed, temperature, relative hu-
midity and pressure) were determined at three distances (10 ft, 25 ft and 50 ft) in both wind ward and lee ward direc-
tions from the mills covering boiling and digestion activities. The emissions from biomass were found to be signifi-
cantly higher than that from fossil diesel, while noise was higher during digestion. The health implications of air emis-
sions were discussed. The study concluded by directing attentions of regulatory agencies to monitor the activities of
smallholder oil palm processing to ensure the environmental sustainability of their operations. In summary, evidence
during boiling activity revealed that:
 H2S ranged from <0.01 - 2.400 ppm at 10 ft, <0.01 - 2.067 ppm at 25 ft and <0.01 - 0.833 ppm at 50 ft from the
mills in the wind ward direction, and <0.01 - 1.167 ppm at 10 ft, <0.01 - 0.567 ppm at 25 ft and <0.01 - 0.367 ppm
at 50ft distance from the mills in lee ward direction and was significantly lower during digestion.
 SPM ranged from 1634 - 7853 µg/m3 at 10 ft, 657 - 1110 µg/m3 at 25 ft and 81 - 854 µg/m3 at 50 ft from the mills in
the wind ward direction, and 46 - 236 µg/m3 at 10 ft, 44 - 120 µg/m3 at 25 ft and 30 - 58 µg/m3 at 50 ft from the
mills in lee ward direction. SPM was significantly lower during digestion.
 VOC ranged from 67 - 13.933 ppm at 10 ft, 1.033 - 13.133 ppm at 25ft and 0.500 - 9.467 ppm at 50 ft from the mills
in the wind ward direction, and 0.300 - 3.200 ppm at 10 ft, 0.133 - 6.733 ppm at 25 ft and 0.100 - 4.773 ppm at 50 ft
from the mills in the lee ward direction, but was significantly lower during digestion..
Keywords: Air Emissions; Noise; Oil Palm Processing; Pollutant Gases
1. Introduction
Within the last few years, environmental issues are in-
creasingly becoming relevant in economic activities and
public health [1,2] in Nigeria and the rest of the world.
Of particular concern is the atmospheric environmental
problems, which had previously received scanty attention
in Nigeria but have become a subject of increasing Na-
tional significance, particularly over the last two years
[3].
Air pollution is a major threat to human life and most
people inhale pollutants while at home or commuting to
work irrespective of the mode of transportation [4]. De-
pending on the dose and the exposure time, these pollut-
ant gases have the potential to cause far reaching adverse
health effects in man, but principally affect the respira-
tory and cardiovascular systems. The World Health Or-
ganization (WHO) estimates that about 2.4 million peo-
ple worldwide (including about 93,700 Nigerians) die
each year from causes directly attributable to air pollu-
tion [5].
Oil palm (Elaeis guineensis) is an indigenous plant to
West Africa [6]. It is the most productive oil crop in the
world [7-15], accounting for 33% of global vegetable oil
production [16]. In Nigeria, over 80% of oil palm culti-
vation and production are controlled by smallholders [17,
18], who typically harvest semi wild plants and use
*Corresponding author.

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
84
manual processing techniques [19,20].
Unlike large oil palm processing mills, smallholders’
operations are done manually and in batches, which de-
pend on biomass fuel during boiling and diesel powered
energy input during digestion (Figures 1 and 2). The
increasing levels of oil palm cultivation and commercial
processing in Nigeria thus raises serious environmental
concerns due to air emissions generated during local oil
palm production.
A hectare of oil palm produces 10 - 35 tonnes of fresh
fruit bunch (FFB) per year [21-23]. The cultivation and
processing of oil palm is a source of livelihood for many
rural dwellers in Nigeria [18]. Oil palms are of multiple
values and are crops of high economic importance that
are often underscored [24]. The plantations cover a range
of 1 - 5 hectares of land and are characterized by mixed
cropping to maximize the usage of the land [25].
There are at least eleven steps in the processing of oil
palm fruits (Figure 1). In smallholder processing opera-
tions, all the steps are carried out manually without any
external energy input except boiling and digestion. Dur-
ing oil palm processing activities, biomass such as Palm
press fiber, empty fruit bunch, palm kernel shells and
chaff are mainly used as boiler fuel, generating smoke.
Emissions are also generated from the diesel engine
during digestion activity (Figure 2), releasing gaseous
pollutants such as carbon monoxide (CO), sulphur diox-
ide (SO2), nitrogen dioxide (NO2), volatile organic com-
pounds (VOCs) and particulate matter [26,27].
These emissions can be injurious to the environment
[2] as well as humans [5,28-30]. H2S and NH3 may also
be emitted in minute quantities by the combustion of
biomass and diesel fuel. The emission from diesel en-
gines depends on the quality of the test fuels used [31,32].
Fossil diesel compositions include 40% paraffin, 35% of
aromatic and <10% of olefin [33]. NO2 is usually gener-
ated during combustion at high temperature [34], and its
concentration increases with the engine combustion effi-
ciency [35], while most SO2 from diesel engines is pro-
duced by the high-temperature oxidation of the sulfates
Figure 1. A schematic chart of palm oil processing by smallholders in Nigeria (* = air quality sampling phas e; POME = palm
oil milling effluents; PPF = palm press fibre; PPFO = palm press fibre oil; CPO = crude palm oil).

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria 85
Boiling activity Digestion activity
Figure 2. Emission processes during oil palm processing by smallholders in N i ge r i a.
in petroleum diesel [34].
After they are emitted into the atmosphere, NO2 and
SO2 become nitrates and sulfate aerosols respectively
that detrimentally affect the environment. SO2 combined
with water vapor in the atmosphere in the presence of a
catalyst (NO2) forms H2SO4, and causes acid rain. When
these acids are consumed, they cause acidosis in human
body, and excess accumulation in the human body can
lead to death [36].
This underlies concerns over the environmental impact
of the use of these fuels as power sources during palm oil
processing by small holders. Emissions of smoke, hy-
drocarbon etc from burning of biomass (such as wood,
crops) and fossil fuels (such as diesel engines and other
transportation engines) have received much concern from
the general public and environmentalists [28,37-44], and
are one of the major environmental problems confronting
Nigeria especially the Niger Delta Area, yet information
regarding this is very scarce. Apart from data collected
by a few individuals and corporate organizations at scat-
tered locations, there is no comprehensive and empirical
database on the magnitude of the hazard and its deleteri-
ous effects on the ecosystems and the people of the re-
gion [30,45].
Noise is generated during all the phases of oil palm
processing especially during digesting and oil extraction
activity. The meteorological indicators (wind speed, rela-
tive humidity, temperature and pressure) of climate are
important considerations during oil palm processing. Air
humidity conditions, among other factors, may affect
human comfort, and could lead to weather-related mor-
tality [46,47] and influences air pollution, which induces
respiratory diseases [48]. Although Relative humidity
(RH) has an effect on the formation and size of secon-
dary aerosols and therefore on the deposition, it is gener-
ally under investigated in urban climate research [49].
This may be related to the fact that humans have difficul-
ties perceiving changes of the relative humidity [50] due
to lack of sensory receptors for humidity [51].
In advanced oil palm producing countries, the sector is
aware of the pollution associated with the processing
activities and they are striving towards quality, environ-
mental conservation through sustainable development
and cleaner technology [52]. With the increasing uses of
oil palm products, its production increases. So the sector
must prepare for the potential challenges associated with
it. Environmental pollution is a critical issue that requires
attention on a dynamic basis despite the existence of en-
vironmental laws and regulations [53].
Air quality studies in Nigeria and particularly the Ni-
ger Delta area are still in its infant stage and faced with
numerous challenges [30,45]. Apart from the issue of too
few air pollution studies, a secondary problem is that
they are often independently carried out, and government
is not involved in systematic and consistent air quality
assessment programmes as is being done in other parts of
the world such as that carried out by the Environmental
Protection Agency (EPA) in the United States [54].
Hence self regulatory environmental management tools
like the ISO 1400 and life cycle assessment (LCA) have
been adopted by the palm oil industries where systematic
assessment checklists on the whole operation and unit
processes and pollution prevention strategies could be
effectively formulated and implemented in most ad-
vanced oil palm processing countries [52].
The self-regulatory approach by the sector will be es-
sential to protect the environment. Improved air quality
could serve as a single health promotion strategy that

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
86
could be beneficial to all, since everybody commute and
breathe air and air pollution is ubiquitous and widespread
[4]. Therefore, it becomes pertinent to investigate the air
emissions from smallholders’ oil palm processing in Ni-
geria.
2. Materials and Methods
2.1. Field Sampling
Six (6) smallholder oil palm processing mill were visited
in Elele, Rivers State, Nigeria from the 13th of April
through the 22nd of April 2012. All the oil palm proc-
essing mills use similar processes and triplicate samples
were collected from each mill specifically during boiling
and digestion operations (Figures 1 and 2). The envi-
ronmental components studied include: Air quality,
Noise and meteorology.
2.2. Air Quality/Meteorological Measurement
The Air quality/meteorological parameters monitored
include total Suspended Particulate, CO, SO2, NO2, NH3,
VOCs Noise, Wind speed, Atmospheric temperature,
Pressure, and Relative humidity. Parameters such as CO,
SO2, NO2, NH3, H2S, VOCs and noise were measured
using in-situ pre-calibrated portable air analyzers. Meas-
urement was made at three (3) different distances from
the mills (10, 25 and 50 ft) in both the windward and
lee-ward directions. The methodologies used for the air
quality indicators are discussed below:
2.2.1. Pollut an t Gases
Portable environmental air analyzers were employed for
the air quality measurement of the pollutants and includ-
ing: NO2 (Model number: Z-1400), SO2 (Model number:
Z-1300), NH3 (Z-800), H2S (Z-900), CO and VOCs
(model ZDL-500). All the above equipment is product of
Environmental Sensors Co, Boca Raton, Florida, USA)
except VOC which is a product of met-one instrument,
USA.
2.2.2. Noise L evel
An Extech instrument (China), model 407730 Sound
level meter with measuring range of 40 - 130 dB (A),
was used to measure the noise level at all the processing
mills visited. Measurements were done by directing the
probe towards the direction of the prevailing sound and
the reading recorded from the digital meter in decibels
dB.
2.2.3. Suspended Particulate Matter (SPM)
A Mini-volume air sampler (model: AEROCET 531,
Manufactured by Met-one instrument, USA) with a pre-
weighed membrane filter (45 µm) was used to collect
particulate matter. With the aid of a pump and a flow-
regulating device, air samples were pumped at a flow
rate of 5 LPM at ambient conditions. Particle size separa-
tion was achieved by impaction and an impactor of 10-
micron cut-point was employed. A quartz filter of 47 mm
diameter was used for trapping and a sensitive analytical
microbalance was used for weighing.
2.2.4. Meteorological Parameters
The Kestrel (model: 4500 NV) manufactured by Nielsen-
Kellerman CO, Boothywn, USA meteorological station
were used to measure temperature, relative humidity,
wind speed and pressure.
2.3. Statistical Analysis
SPSS software version 17 (SPSS Inc., Chicago) was used
to carry out the statistical analysis. A one-way analysis of
variance was carried out at α = 0.05, and Duncan’s mul-
tiple range test was used to discern the source of the ob-
served differences.
3. Results and Discussion
The results of the air quality analysis during boiling and
digestion of oil palm is presented in Tables 1 and 2 re-
spectively, while noise/meteorology are respectively
presented in Tabl es 3 and 4. NO2 concentration was gen-
erally below the equipment detection limits (<0.01 ppm)
in most of the mills, though with few exceptions.
During boiling, NO2 was recorded in few mills; at 10
ft from mill A (0.233 ± 0.033 ppm) and mill D (0.267 ±
0.033 ppm) in the wind ward direction, At mill E, NO2
was recorded at 25 ft (0.133 ± 0.033 ppm) in the wind
ward direction and 10 ft (1.167 ± 0.033 ppm) in the lee
ward direction (i.e. off wind direction). In mill C, NO2
was not recorded in the wind ward direction, but only at
50 ft (0.167 ± 0.033 ppm) in the lee ward direction. The
may be attributed to sudden change in wind direction as
was observed in the particular mill during the study.
During digestion, NO2 was not recorded at any of the
mills in the lee-ward direction but only in mill A, B and
C in the wind ward direction. In these mills, NO2 was
consistently higher at the 10 ft distance from the mills
and least at 50 ft. Since the permissible limits of NO2 in
Nigeria are 0.04 - 0.06 ppm [55] (Table 5), it therefore
follows that the limits were exceeded in some of the
mills during boiling. However, the levels during the di-
gestion process were within the Nigerian ambient air
quality standards.
NO2 is acidic gas and an important indicator of air pol-
lution as it correlates well with other air pollutant con-
centrations. NO2 is emitted during the combustion of
fossil diesel and biomass and the variation in the concen-
tration detected in this study is likely to be associated

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
87
Table 1. Air quality during boiling activity of oil palm processing in the wind and lee ward directions.
Mill # Distance (ft) Emission
direction NO2, ppm NH3, ppmCO, ppm H2S, ppm SO2, ppm SPM, µg/m3 VOC, ppm
10 0.233 ±
0.033c <0.01a 0.133 ± 0.033ab
0.333 ±
0.033bcde <0.01a 1634.0 ± 3.0j
13.933 ±
0.291m
25 <0.01a <0.01a 0.133 ±
0.033ab
0.433 ±
0.088 bcdef<0.01a 768 ± 13.0fg
13.133 ±
0.504l
A
50 <0.01a <0.01a <0.01a 0.567 ±
0.033defg <0.01a 443.0 ± 8.0e
9.467 ±
0.260k
10 <0.01a 0.267 ±
0.033bc
1.867 ±
0.318ef
0.500 ±
0.058cdef
0.167 ±
0.067ab
7853.0 ±
23.0n
4.333 ±
0.203h
25 <0.01a <0.01a 0.500 ±
0.058abc
1.800 ±
0.208j
0.167 ±
0.067ab
712.0 ±
21.0f
1.400 ±
0.115e
B
50 <0.01a <0.01a <0.01a 0.433 ±
0.033bcdef <0.01a 442.0 ± 10.0e
0.500 ±
0.115ab
10 <0.01a <0.01a 6.467 ±
0.338j <0.01a <0.01a 2292.0 ± 30.0k
4.700 ±
0.208hi
25 <0.01a <0.01a 5.767 ±
0.145i <0.01a <0.01a 657.0 ± 24.0f
3.833 ±
0.260g
C
50 <0.01a <0.01a 0.233 ±
0.067ab
0.167 ±
0.067ab <0.01a 105.0 ± 5.0abc
2.867 ±
0.033f
10 0.267 ±
0.033c
0.300 ±
0.058cd
5.700 ±
0.100i
2.400 ±
0.351k
2.033 ±
0.088e
1089.0 ±
10.0i
1.167 ±
0.088de
25 <0.01a 0.267 ±
0.033bc
3.067 ±
0.384g
0.367 ±
0.033bcde <0.01a 684.0 ± 6.0f
2.900 ±
0.058f
D
50 <0.01a <0.01a 0.833 ±
0.088bcd <0.01a <0.01a 81.0 ± 2.0abc
1.067 ±
0.088cde
10 <0.01a <0.01a 27.167 ±
0.273m
0.733 ±
0.267fg
0.433 ±
0.285cd
3555.0 ±
99.0l
3.233 ±
0.145f
25 0.133 ±
0.033b <0.01a 9.700 ± 0.833k <0.01a <0.01a 922.0 ± 15.0h
1.067 ±
0.088cde
E
50 <0.01a <0.01a 7.033 ±
0.639j <0.01a <0.01a 170.0 ± 16.0bcd
0.600 ±
0.058abc
10 <0.01a 0.667 ±
0.033e
26.700 ±
0.208m
1.100 ±
0.115hi
0.333 ±
0.033bc
4354.0 ±
183.0m
4.800 ±
0.115i
25 <0.01a 0.433 ±
0.285d
15.233 ±
0.441l
2.067 ±
0.120j
0.633 ±
0.088d
1110.0 ±
26.0i
1.033 ±
0.088cde
F
50
Wind ward
<0.01a <0.01a 9.133 ±
0.167k
0.833 ±
0.033 gh
0.467 ±
0.267cd
854.0 ±
27.0gh
0.533 ±
0.088ab

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
88
Continued
10 <0.01a <0.01a <0.01a <0.01a <0.01a 236.0 ±
6.0d
3.200 ±
0.173f
25 <0.01a 0.167 ±
0.033abc <0.01a 0.367 ± 0.033bcde
0.167 ±
0.033ab
120.0 ±
1.0abc
6.733 ±
0.176j
A
50 <0.01a <0.01a <0.01a 0.367 ±
0.033bcde <0.01a 58.0 ± 2.0abc
4.733 ±
0.088hi
10 <0.01a <0.01a 0.133 ±
0.033ab
0.600 ±
0.100efg <0.01a 68.0 ± 32.0abc
1.067 ±
0.145cde
25 <0.01a <0.01a <0.01a 0.567 ±
0.033defg <0.01a 95.0 ± 2.0abc
0.200 ±
0.058a
B
50 <0.01a <0.01a <0.01a 0.233 ±
0.033abc <0.01a 36.0 ± 1.0a
0.333 ±
0.033a
10 <0.01a 0.300 ±
0.058cd
4.267 ±
0.145h <0.01a <0.01a 78.0 ± 3.0abc
0.433 ±
0.033ab
25 <0.01a <0.01a <0.01a <0.01a <0.01a 51.0 ±
1.0abc
0.333 ±
0.088a
C
50 0.167 ±
0.033b <0.01a 2.467 ± 0.145fg <0.01a <0.01a 39.0 ± 1.0a
0.167 ±
0.067a
10 <0.01a <0.01a 1.067 ±
0.088cd
0.567 ±
0.088defg <0.01a 46.0 ± 2.0ab
0.867 ±
0.033bcd
25 <0.01a <0.01a 0.400 ±
0.058abc <0.01a <0.01a 47.0 ± 3.0ab
0.400 ±
0.100ab
D
50 <0.01a <0.01a <0.01a <0.01a <0.01a 40.0 ±
7.0a
0.200 ±
0.058a
10 1.167 ±
0.088d
0.133 ±
0.033ab
1.267 ±
0.145de
1.167 ±
0.088i <0.01a 50.0 ± 12.0abc
0.300 ±
0.058a
25 <0.01a <0.01a <0.01a 0.267 ±
0.067abcd <0.01a 60.0 ± 4.0abc
0.133 ±
0.033a
E
50 <0.01a <0.01a <0.01a 0.133 ±
0.033ab <0.01a 54.0 ± 4.0abc
0.100 ±
0.058a
10 <0.01a <0.01a 2.867 ±
0.088g
0.300 ±
058abcde <0.01a 174.0 ± 12.0cd
0.300 ±
0.058a
25 <0.01a <0.01a <0.01a <0.01a <0.01a 44.0 ±
7.0ab
0.133 ±
0.033a
F
50
Lee ward
<0.01a <0.01a <0.01a 0.133 ±
0.033ab <0.01a 30.0 ± 7.0a
0.200 ±
0.058a
Each value is expressed as mean ± standard error (n = 3). Different letters in each column indicate significant differences at P < 0.05 according to the Duncan
Statistics.

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria 89
Table 2. Air quality during digestion activity of oil palm processing in the wind and lee ward directions.
Mill # Distance (ft) Emission
direction NO2, ppm NH3, ppmCO, ppm H2S, ppm SO2, ppm SPM, µg/m3 VOC, ppm
10 0.167 ±
0.033c
0.167 ±
0.067d
0.700 ±
0.115hi
0.300 ±
0.058b <0.01 163.0 ± 2.01pq
4.700 ±
0.153i
25 0.033 ±
0.033ab
0.067 ±
0.033bc
0.300 ±
0.100abcde
0.033 ±
0.033a <0.01 30.0 ± 6.0abcde
1.100 ±
0.153cde
A
50 0.067 ±
0.033b
0.033 ±
0.033ab
0.200 ±
0.058abcd
0.033 ±
0.033a <0.01 46.0 ± 2.0defghi
0.433 ±
0.067ab
10 0.133 ±
0.033c <0.01a 0.733 ± 0.088hi
0.033 ±
0.033a <0.01 57.0 ± 3.0fghijk
8.633 ±
0.219m
25 0.067 ±
0.033b <0.01a 0.433 ± 0.033defg <0.01a <0.01 26.0 ± 3.0abcd
2.100 ±
0.289f
B
50 <0.01a <0.01a 0.167 ±
0.067abcd
0.033 ±
0.033a <0.01 17.0 ± 7.0a 0.500 ± 0.115ab
10 0.233 ±
0.067d <0.01a 0.733 ± 0.088hi <0.01a <0.01 77.0 ± 3.0klmn
10.167 ±
0.410n
25 0.067 ±
0.033b <0.01a 0.267 ± 0.088abcde <0.01a <0.01 30.0 ± 4.0abcde
2.367 ±
0.273f
C
50 <0.01a <0.01a 0.167 ±
0.067 <0.01a <0.01 59.0 ± 3.0fghijkl
0.533 ±
0.067ab
10 <0.01a 0.100 ±
0.058c
0.700 ±
0.100hi <0.01a <0.01 117.0 ± 3.0o
5.767 ±
0.285k
25 <0.01a 0.067 ±
0.033bc
0.333 ±
0.088abcde
0.033 ±
0.033a <0.01 84.0 ± 6.0mn
1.567 ±
0.285e
D
50 <0.01a <0.01a 0.267 ±
0.088abcde <0.01a <0.01 70.0 ± 4.0ijklm
0.400 ±
0.058ab
10 <0.01a <0.01a 0.867 ±
0.088i <0.01a <0.01 78.0 ± 6.0klmn
6.233 ±
0.145l
25 <0.01a <0.01a 0.600 ±
0.058fgh <0.01a <0.01 34.0 ± 7.0abcdef
1.267 ±
0.273de
E
50 <0.01a <0.01a 0.300 ±
0.100abcde
0.033 ±
0.033a <0.01 18.0 ± 1.0ab
0.500 ±
0.058ab
10 <0.01a <0.01a 0.633 ±
0.067ghi <0.01a <0.01 68.0 ± 9.0hjklm
4.800 ±
0.115ij
25 <0.01a <0.01a 0.333 ±
0.088abcde
0.033 ±
0.033a <0.01 53.0 ± 2.0efghijk
1.067 ±
0.088cd
F
50
Wind ward
<0.01a <0.01a 0.133 ±
0.033abc <0.01a <0.01 20.0 ± 5.0abc
0.533 ±
0.088ab

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
90
Continued
10 <0.01a <0.01a 0.267 ±
0.088abcde <0.01a <0.01 28.0 ± 4.0abcde
4.167 ±
0.219h
25 <0.01a <0.01a 0.200 ±
0.058abcd <0.01a <0.01 14.0 ± 4.0a
0.367 ±
0.067ab
A
50 <0.01a <0.01a 0.067 ±
0.033a <0.01a <0.01 540.0 ± 15.0s
0.367 ±
0.033ab
10 <0.01a <0.01a 0.267 ±
0.067abcde <0.01a <0.01 51.0 ± 6.0defghij
5.233 ±
0.145j
25 <0.01a <0.01a 0.200 ±
0.058abcd <0.01a <0.01 43 ± 2.0bcdefg
0.733 ±
0.088abc
B
50 <0.01a <0.01a 0.200 ±
0.058abcd <0.01a <0.01 97.0 ± 25.0no
0.233 ±
0.033a
10 <0.01a <0.01a 0.367 ±
0.120bcdef <0.01a <0.01 177.0 ± 3.0q
6.500 ±
0.153l
25 <0.01a <0.01a 0.233 ±
0.033abcd <0.01a <0.01 28.0 ± 3.0abcde
0.567 ±
0.033ab
C
50 <0.01a <0.01a 0.100 ±
0.058ab <0.01a <0.01 53.0 ± 1.0efghijk
0.400 ±
0.058ab
10 <0.01a <0.01a 0.400 ±
0.058cdefg <0.01a <0.01 63.0 ± 6.0ghijklm
5.133 ±
0.088ij
25 <0.01a <0.01a 0.133 ±
0.033abc <0.01a <0.01 43.0 ± 1.0bcdefg
0.467 ±
0.033ab
D
50 <0.01a <0.01a 0.133 ±
0.088abc <0.01a <0.01 74.0 ± 2.0jklmn
0.233 ±
0.033a
10 <0.01a <0.01a 0.500 ±
0.153efgh <0.01a <0.01 82.0 ± 3.0lmn
4.233 ±
0.145h
25 <0.01a <0.01a 0.333 ±
0.088abcde <0.01a <0.01 36.0 ± 1.0abcdef
0.800 ±
0.058bcd
E
50 <0.01a <0.01a 0.167 ±
0.033abcd <0.01a <0.01 44.0 ± 2.0cdefgh
0.233 ±
0.033a
10 <0.01a <0.01a 0.367 ±
0.033bcdef <0.01a <0.01 148.0 ± 14.0p
3.500 ±
0.208g
25 <0.01a <0.01a 0.200 ±
0.058abcd <0.01a <0.01 15.0 ± 0.0a
0.233 ±
0.033a
F
50
Lee ward
<0.01a <0.01a 0.067 ±
0.033a <0.01a <0.01 220.0 ± 5.0r
0.200 ±
0.058a
Each value is expressed as mean ± standard error (n = 3). Different letters in each column indicate significant differences at P < 0.05 according to the Duncan
Statistics.

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria 91
Table 3. Noise & meteorology during boiling activity of oil palm processing in the wind and lee ward directions.
Mill # Distance
(ft)
Emission
direction Noise, db Wind Speed, m/s Relative Humidity RH, % Temperature, ˚C Pressure, hpa
10 50.70 ± 0.346abc 0.400 ± 0.058bcdefgh79.967 ± 0.203f 28.03 ± 0.260abcde 1008.50 ± 0.058efg
25 52.87 ± 1.093bc 0.267 ± 0.033abcde84.900 ± 0.346kl 27.43 ± 0.088ab 1008.50 ± 0.058efgA
50 50.73 ± 0.837abc 0.167 ± 0.067ab 83.200 ± 1.159hij 27.53 ± 0.033abc 1008.43 ± 0.033efg
10 68.90 ± 0.416f 0.133 ± 0.033ab 69.500 ± 0.737cd 34.20 ± 0.513kl 1006.43 ± 0.088abc
25 63.50 ± 0.300e 0.233 ± 0.067abcd 68.367 ± 0.145c 32.97 ± 0.393hi 1006.43 ± 0.067abcB
50 52.77 ± 0.285bc 0.200 ± 0.058abc 70.233 ± 0.233d 32.27 ± 0.233gh 1008.27 ± 0.088e
10 52.70 ± 0.265bc 0.533 ± 0.033efghijk60.900 ± 0.265a 35.80 ± 0.058m 1006.63 ± 0.088c
25 49.27 ± 0.837a 1.567 ± 0.176m 62.433 ± 0.260a 35.40 ± 0.173m 1006.63 ± 0.088c C
50 61.77 ± 0.338de 0.233 ± 0.067abcd 65.600 ± 0.643b 34.03 ± 0.581jkl 1007.27 ± 0.186d
10 62.93 ± 0.546e 0.767 ± 0.033jk 62.400 ± 0.173a 34.57 ± 0.260l 1006.13 ± 0.145ab
25 49.53 ± 0.617ab 0.633 ± 0.328ghijk64.533 ± 0.176b 33.57 ± 0.186ijk 1006.07 ± 0.088a D
50 49.47 ± 0.437ab 0.733 ± 0.033ijk 64.500 ± 0.265b 33.23 ± 0.240ij 1006.10 ± 0.115a
10 62.43 ± 0.788de 0.800 ± 0.058k 81.800 ± 0.451gh 29.10 ± 0.493f 1008.63 ± 0.088efg
25 61.30 ± 0.493de 0.800 ± 0.058k 83.667 ± 1.081ijk 28.50 ± 0.173def 1008.70 ± 0.000fg E
50 61.53 ± 0.524de 0.167 ± 0.033ab 85.167 ± 0.769klm28.67 ± 0.133ef 1008.73 ± 0.033g
10 62.87 ± 0.524e 0.633 ± 0.033ghijk73.033 ± 0.674e 27.93 ± 0.145abcde 1008.47 ± 0.033efg
25 61.87 ± 1.037de 0.700 ± 0.058ijk 86.467 ± 0.784lm 28.30 ± 0.153cdef 1008.63 ± 0.067efgF
50
Wind
ward
62.43 ± 0.788de 0.600 ± 0.058ghijk72.500 ± .351e 27.73 ± 0.088abcd 1008.43 ± 0.033efg
10 50.50 ± 0.231abc 0.467 ± 0.033cdefghi80.300 ± 0.153fg 28.17 ± 0.203bcde 1008.33 ± 0.186efg
25 52.20 ± 1.050abc 0.133 ± 0.033ab 84.833 ± 0.433jkl 27.27 ± 0.088a 1008.43 ± 0.176efgA
50 50.73 ± 0.736abc 0.167 ± 0.033ab 83.033 ± 1.087hi 27.33 ± 0.167ab 1008.33 ± 0.186efg
10 66.77 ± 2.046f 0.567 ± 0.067fghijk70.333 ± 0.186d 33.90 ± 0.458jkl 1006.23 ± 0.088abc
25 62.50 ± 0.755de 0.300 ± 0.058abcdef68.733 ± 0.120cd 33.03 ± 0.145i 1006.27 ± 0.088abcB
50 53.17 ± 0.433c 0.100 ± 0.000a 69.800 ± 0.306cd 32.00 ± 0.058g 1008.37 ± 0.219efg
10 53.33 ± 0.348c 0.633 ± 0.120ghijk61.133 ± 0.384a 35.63 ± 0.120m 1006.53 ± 0.067bc
25 50.43 ± 0.696abc 0.500 ± 0.058defghij62.600 ± 0.153a 35.50 ± 0.173m 1006.53 ± 0.120bc C
50 59.23 ± 2.697d 0.267 ± 0.088abcde65.66 ± 0.6067b 33.93 ± 0.533jkl 1007.33 ± 0.219d
10 62.30 ± 0.458de 1.200 ± 0.115l 62.533 ± 0.233a 34.60 ± 0.252l 1006.07 ± 0.133a
25 52.73 ± 3.000bc 1.367 ± 0.088lm 64.467 ± 0.145b 33.53 ± 0.233ijk 1006.10 ± 0.153a D
50 49.47 ± 0.291ab 0.667 ± 0.088hijk 64.433 ± 0.145b 33.30 ± 0.200ij 1006.10 ± 0.115a
10 63.43 ± 1.235e 0.667 ± 0.088ghijk81.767 ± 0.467gh 29.07 ± 0.088f 1008.50 ± 0.173efg
25 62.87 ± 1.450e 0.567 ± 0.067fghijk83.733 ± 1.035ijk 28.57 ± 0.186def 1008.57 ± 0.145efgE
50 60.90 ± 1.153de 0.367 ± 0.067abcdefg85.133 ± 0.745klm28.60 ± 0.058ef 1008.30 ± 0.115ef
10 62.67 ± 0.328e 0.267 ± 0.033abcde73.033 ± 0.584e 27.93 ± 0.088abcde 1008.60 ± 0.173efg
25 61.87 ± 0.801de 0.367 ± 0.067abcdefg86.600 ± 0.361m 28.40 ± 0.153def 1008.70 ± 0.115fg F
50
Lee
ward
63.50 ± 0.351e 0.200 ± 0.058abc 72.2 ± 0.20333e 27.73 ± 0.033abcd 1008.40 ± 0.153efg
Each value is expressed as mean ± standard error (n = 3). Different letters in each column indicate significant differences at P < 0.05 according to the Duncan
Statistics.

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
92
Table 4. Noise & meteorology during digestion activity of oil palm processing in wind and lee ward direction.
Mill # Distance
(ft)
Emission
direction Noise, db Wind Speed, m/s RH, % Temperature, ˚C Pressure, hpa
10 80.70 ± 0.346de 0.533 ± 0.033abcdefg79.933 ± 0.267h 28.03 ± 0.291abc 1008.67 ± 0.088ef
25 74.47 ± 0.145c 0.267 ± 0.033abcd 84.733 ± 0.285kl 27.23 ± 0.088a 1008.37 ± 0.120ef A
50 64.07 ± 2.652a 0.167 ± 0.067ab 83.100 ± 1.277ijk 27.43 ± 0.088ab 1008.40 ± 0.153ef
10 88.90 ± 0.416f 0.200 ± 0.058abc 69.500 ± 0.666def 33.90 ± 0.252ghij 1006.43 ± 0.145abc
25 73.50 ± 0.300c 0.167 ± 0.067ab 68.433 ± 0.067de 33.00 ± 0.451f 1006.20 ± 0.058abcB
50 66.10 ± 3.508a 0.200 ± 0.058abc 70.200 ± 0.351f 32.10 ± 0.300e 1008.17 ± 0.088e
10 82.70 ± 0.265e 0.533 ± 0.033abcdefg60.767 ± 0.348a 35.70 ± 0.058l 1006.57 ± 0.033cd
25 75.93 ± 2.652cd 0.933 ± 0.186g 62.533 ± 0.088b 35.37 ± 0.088kl 1006.50 ± 0.100bc C
50 63.10 ± 1.002a 0.567 ± 0.067abcdefg65.500 ± 0.529c 34.07 ± 0.570hij 1007.00 ± 0.306d
10 83.60 ± 1.206e 0.867 ± 0.233fg 62.467 ± 0.088b 34.67 ± 0.273jk 1006.07 ± 0.448abc
25 76.20 ± 2.757cd 0.633 ± 0.328bcdefg64.600 ± 0.100c 33.57 ± 0.088fghi 1005.90 ± 0.100a D
50 66.80 ± 2.425ab 0.667 ± 0.033cdefg64.400 ± 0.058c 33.17 ± 0.203fg 1006.00 ± 0.115ab
10 82.43 ± 0.788e 0.633 ± 0.067bcdefg81.800 ± 0.252ij 29.03 ± 0.481d 1008.37 ± 0.176ef
25 74.63 ± 2.948c 0.800 ± 0.058efg 83.367 ± 0.974jkl 28.47 ± 0.033cd 1008.50 ± 0.153ef E
50 64.53 ± 1.369a 0.600 ± 0.200abcdefg84.967 ± 0.902lm 28.57 ± 0.033cd 1008.70 ± 0.115ef
10 82.87 ± 0.524e 0.767 ± 0.067efg 73.100 ± 0.709g 27.87 ± 0.267abc 1008.27 ± 0.088ef
25 71.87 ± 1.037c 0.700 ± 0.058defg 86.467 ± 0.612m 28.53 ± 0.120cd 1008.60 ± 0.115ef F
50
Wind
ward
64.43 ± 1.178a 0.733 ± 0.088defg 72.300 ± 0.300g 27.40 ± 0.058ab 1008.27 ± 0.088ef
10 80.57 ± 0.418de 0.533 ± 0.033abcdefg79.900 ± 0.361h 28.13 ± 0.120bc 1008.73 ± 0.033f
25 74.20 ± 0.058c 0.267 ± 0.033abcd 84.500 ± 0.351kl 27.53 ± 0.145ab 1008.57 ± 0.145ef A
50 63.97 ± 2.674a 0.133 ± 0.033a 83.067 ± 1.161ijk 27.30 ± 0.153ab 1008.63 ± 0.033ef
10 88.90 ± 0.351f 0.267 ± 0.033 69.267 ± 0.498def 34.03 ± 0.348hij 1006.43 ± 0.145abc
25 73.60 ± 0.252c 0.333 ± 0.145abcd 68.200 ± 0.058d 33.10 ± 0.404fg 1006.20 ± 0.058abcB
50 62.90 ± 0.351a 0.400 ± 0.100abcde69.967 ± 0.338ef 31.90 ± 0.252e 1008.17 ± 0.088e
10 82.53 ± 0.285e 0.533 ± 0.033abcdefg60.667 ± 0.318a 35.40 ± 0.100kl 1006.30 ± 0.058abc
25 75.57 ± 2.696cd 0.933 ± 0.186g 62.233 ± 0.088ab 35.60 ± 0.058l 1006.50 ± 0.100bc C
50 63.33 ± 0.984a 0.667 ± 0.260cdefg65.267 ± 0.521c 34.30 ± 0.557ij 1006.30 ± 0.058abc
10 83.53 ± 1.284e 0.700 ± 0.100defg 62.400 ± 0.058b 34.67 ± 0.273jk 1006.07 ± 0.448abc
25 75.90 ± 2.762cd 0.700 ± 0.265defg 64.300 ± 0.058c 33.43 ± 0.145fgh 1006.23 ± 0.120abcD
50 66.67 ± 2.153ab 0.667 ± 0.033cdefg64.200 ± 0.058c 33.27 ± 0.491fgh 1006.17 ± 0.088abc
10 82.33 ± 0.636e 0.700 ± 0.265defg 81.633 ± 0.240i 29.10 ± 0.321d 1008.37 ± 0.176ef
25 74.67 ± 2.928c 0.667 ± 0.033cdefg83.267 ± 1.017ijkl 28.70 ± 0.153cd 1008.50 ± 0.153ef E
50 64.33 ± 1.485 0.600 ± 0.200abcdefg84.967 ± 0.865lm 28.53 ± 0.120cd 1008.70 ± 0.115ef
10 82.50 ± 0.300e 0.667 ± 0.033cdefg72.933 ± 0.644g 27.90 ± 0.252abc 1008.37 ± 0.145ef
25 71.60 ± 0.945bc 0.400 ± 0.208abcdef86.433 ± 0.521m 28.60 ± 0.173cd 1008.60 ± 0.115ef F
50
Lee
ward
64.13 ± 1.214a 0.467 ± 0.186abcdefg71.967 ± 0.384g 27.17 ± 0.088a 1008.60 ± 0.208ef
Each value is expressed as mean ± standard error (n = 3). Different letters in each column indicate significant differences at P < 0.05 according to the Duncan
tatistics. S

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
93
Table 5. Air quality, noise and meteorology recommenda-
tion guideline.
NigerianAmbient Air Quality Standard [55]
Parameter
Time of average Limits
Ambient
Temperature ˚C * 30˚C
Noise (dB)A * 90
NO2 (ppm) Daily average of hourly
values (range)
0.04 ppm - 0.06 ppm
(75.0 µg/m3 - 113 µg/m3)
NH3 (ppm) * *
SO2 (ppm) Daily average of hourly
values 1 hour
0.01 ppm (26 µg/m3)
0.1 ppm (260 µg/m3)
H2S (ppm) * *
CO (ppm) Daily average of hourly
values 8-hourly average
10 ppm (11.4 µg/m3)
20 ppm (22.8 µg/m3)
VOC (ppm) * *
SPM (µg/m3) Daily average of hourly
values 1 hour
250 µg/m3
600 µg/m3
*No stated limit.
with combustion temperature [56]. NO2 emission from
digestion activity is dependent upon the speed of the en-
gine and the load [57]. NO2 poses important environ-
mental and public health concerns as it contributes to
greenhouse gas levels and high levels of NO2 is associ-
ated with increased risk of respiratory diseases and con-
tributes to heart, lung, liver and kidney diseases [30].
Ammonia was not generally detected in most of the
mills during boiling and digestion activities, except in
few instances. During boiling, ammonia was highest at
10 ft (<0.01 - 0.667 ppm), followed by 25 ft (<0.01 -
0.267 ppm) and not detected at 50 ft in the wind ward
direction. Whereas in the lee ward direction ammonia
was only recorded (0.133 - 0.300 ppm) at 10 ft distance
from only 3 mills (A, C and E), and was not detected at
other distances in the mills. Ammonia was generally ab-
sent during digestion both in the lee ward and wind ward
directions except in mill A, B, C where it was recorded in
the wind ward direction at 10 ft (0.133 - 0.233 ppm), 25
ft (0.033 - 0.067 ppm) and 50 ft (<0.01 - 0.067 ppm).
Though, Nigeria does not have permissible limits for
ammonia, the difference between the lee ward and wind
ward concentration can be used to assess the impact. The
result show that the concentration of ammonia released
during boiling activity is significantly higher (P < 0.05)
than that released during the digestion activity indicating
that biomass fuel contribute higher levels of ammonia to
the atmosphere than fossil fuel.
CO was detected at all the mills, during boiling and
digestion activities at the 3 distances (10 ft, 25 ft and 50
ft) from the mills in both wind ward and lee ward direc-
tions. During boiling, CO was 0.133 - 27. 167 ppm at 10
10 ft, 0.133 - 15.233 ppm at 25 ft and <0.01 - 9.133 ppm
at 50 ft in the wind ward direction, whereas in the lee
ward direction it was significantly lower (P < 0.05)
ranging from <0.01 - 4.267 ppm at 10 ft, <0.01 - 0.567
ppm at 25 ft and <0.01 - 2.467 ppm at 50 ft from the
mills. The higher emission generated at 25 ft could be
associated to the addition of more biomass/boiler fuel
during measurement. During digestion, CO ranged from
0.633 - 0.867 ppm at 10 ft, 0.267 - 0.600 ppm at 25 ft and
0.133 - 0.300 ppm at 50 ft from the mils in the wind ward
direction, whereas in the lee ward direction it ranged
from 0.267 - 0.500 ppm at 10 ft, 0.133 - 0.333 ppm at 25
ft and 0.067 - 0.200 ppm at 50 ft from the mills. CO was
significantly higher during boiling than during digestion.
In all cases CO was highest in the 10 ft distance and
least at 50 ft distance from the mills, the values recorded
in the wind ward direction is significantly higher than
those recorded in the lee ward direction. CO was higher
than the Nigerian permissible limit of 10 ppm (daily
hourly average) and 20 ppm (8-hourly average) [55]
(Table 5) only during boiling activities thus indicating
superiority of fossil fuel and higher combustion effi-
ciency of the diesel generator compared to direct biomass
burning. Typically, CO gas is produced by the incom-
plete combustion of carbonaceous materials or fossil fu-
els-gas, oil, coal and wood. The variation in the emission
of CO is associated with the load, because the higher the
load, the richer fuel mixture is burned, and thus produces
more CO [56]. CO is of health concern as it inhibits the
bloods ability to carry oxygen to vital organs such as the
heart and brain.
The severity of the health effects is dose dependent.
Typical sickness symptoms include headache, dizziness
and nausea. CO is associated with reduced exercise tol-
erance, particularly in people with coronary artery dis-
ease, because of the formation of carboxyhaemoglobin
[29,58].
During boiling activity, H2S ranged from <0.01 - 2.400
ppm at 10 ft, <0.01 - 2.067 ppm at 25 ft and <0.01 -
0.833 ppm at 50 ft from the mills in the wind ward direc-
tion, whereas at the lee ward direction it was <0.01 -
1.167 ppm at 10 ft, <0.01 - 0.567 ppm at 25 ft and <0.01
- 0.367 ppm at 50 ft distance from the mills. During di-
gestion activity, H2S concentration ranged from <0.01 -
0.300 ppm at 10 ft, <0.01 - 0.033 ppm at 25 ft and <0.01
- 0.033 ppm at 50 ft in the wind ward direction, and was
not detected in any of the mills in the lee ward direction.
Nigeria has no permissible limit for H2S, hence impact
shall be established based on the differences between the
values recorded in the wind ward direction relative to the
lee ward direction. The pattern of variation in H2S is
similar to that observed in other air quality parameters,

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria
94
being highest during boiling activity than digestion and
values recorded at the wind ward direction was signifi-
cantly higher than the lee ward direction. In most of the
mills, H2S was lowest at 50 ft from the mills i.e. the con-
centration decreases with increasing distance from the
mills. These results also show the superiority of fossil
fuel combustion over biomass in the processing of oil
palm.
SO2 was recorded only in few instances during boiling
activity only. During boiling, SO2 ranged from <0.01 -
2.033 ppm at 10 ft, <0.01 - 0.633 ppm at 25 ft and <0.01
- 0.467 ppm at 50 ft from the mills in the wind ward di-
rection, whereas at the lee ward direction, it was <0.01
ppm in all the mills except at 25 ft from mill A where a
value of 0.167 ± 0.033 ppm was recorded. SO2 was not
detected at any distance during digestion activity. SO2
exceeded the permissible limits of 0.01 - 0.10 ppm [55]
(Table 5) during boiling activity, thus indicating the su-
periority of fossil fuel combustion over direct biomass
combustion. Basically SO2 are produced by the combus-
tion of fossil fuels containing sulphur.
SPM was very high especially during boiling activity
ranging from 1634 - 7853 µg/m3 at 10 ft, 657 - 1110
µg/m3 at 25 ft and 81 - 854 µg/m3 at 50 ft from the mills
in the wind ward direction, whereas in the lee ward di-
rection, it was 46 - 236 µg/m3 at 10 ft, 44 - 120 µg/m3 at
25 ft and 30 - 58 µg/m3 at 50 ft from the mills.
During digestion, SPM ranged from 57 - 167 µg/m3 at
10 ft, 14 - 84 µg/m3 at 25 ft and 17 - 70 µg/m3 at 50ft
from the mills in the wind ward direction, whereas in the
lee ward direction it was 28 - 177 µg/m3 at 10 ft, 14 - 43
µg/m3 at 25 ft and 44 - 540 µg/m3 at 50ft from the mills.
SPM was significantly higher (P > 0.05) during boiling
activity than during digestion.
The highest value of SPM was recorded at 10ft dis-
tance to the mills in the wind ward direction, which de-
creased at increasing distance to the mills. The results
also indicated that lower SPM was generated during di-
gestion using diesel fossil fuel, again, showing that the
diesel fossil fuel emit lesser SPM than wood fuels. While
the SPM recorded during digestion activity were within
the permissible limits of 250 - 600 µg/m3 [55] (Table 5)
but SPM release during the boiling activity was signifi-
cantly higher than this limit. The mass, size, number and
particle composition are affected by combustion proc-
esses, condensation, adsorption, coagulation, agglomera-
tion and collision of hydrocarbon in the engine exhaust
[59,60] Diesel exhaust (DE) is a major contributor to
combustion derived particulate matter air pollution. The
particulate matter generated is in the form of carbon
black, soot and fly ash which are major components of
smoke and are often within 10 μm size range [45].
SPM exposure affects the lungs and heart, although the
patho-physiological mechanism is not fully understood,
due to the chemically heterogeneous nature of SPM [29].
Generally, however, it has been associated with decrease
in lung function in children and adults, premature deaths
from respiratory and cardiac causes and increased hospi-
tal admissions for asthma-like conditions [28]. Ossai et al.
[61] and Efe [36] asserted that high rate of particulate
matter causes respiratory diseases such as emphysema,
pneumonia, bronchitis, asthma and respiratory tuberculo-
sis. Also it can lead to eyes, teeth, and bones damage,
increased susceptibility to disease and other stress-related
environmental hazards, and reduces the reproduction
potential in some species [62-65]. Other diseases associ-
ated with particulate matter include acute vascular dys-
function, increased thrombus formation pulmonary edema,
etc. [45].
During boiling activity VOC ranged from 1.167 -
13.933 ppm at 10 ft, 1.033 - 13.133 ppm at 25 ft and
0.500 - 9.467 ppm at 50 ft from the mills in the wind
ward direction, while at the lee ward direction it was
0.300 - 3.200 ppm at 10 ft, 0.133 - 6.733 ppm at 25 ft and
0.100 - 4.773 ppm at 50 ft from the mills. During diges-
tion, VOC ranged from 4.700 - 10.167 ppm at 10 ft and
1.067 - 2.367 ppm at 25 ft and 0.400 - 0.533 ppm at 50 ft
from the mills in the wind ward direction, whereas in the
lee ward direction, it was 3.500 - 6.500 ppm at 10 ft,
0.233 - 0.800 ppm at 25 ft and 0.200 - 0.400 ppm at 50 ft
from the mills. VOC was significantly higher during
boiling activity than digestion, and in the wind ward than
lee ward direction. The concentration of VOC was high-
est at 10 ft to the mills and decreased with increasing
distance to the mills. The low molecular weight organic
fractions are highly volatile and with short atmospheric
life-time.
Although the Nigerian ambient air quality standards
does not specify any limit for VOC, health effects from
these chemical compounds depend on the type, level and
length of exposure. Short term exposure is likely cause of
sensory irritation, particularly of the eyes, nose and throat
[50] while long term exposure may lead to liver, kidney
damage and cancer. However, VOCs could be affected
byrelative humidity recorded in some mills [66,67].
During boiling activity noise ranged from 50.70 -
68.90 dB at 10 ft, 49.27 - 63.50 dB at 25 ft and 49.47 -
62.43 dB at 50 ft from the mills in the wind ward direc-
tion, whereas in the lee ward direction it was 50.50 -
66.77 dB at 10 ft, 50.43 - 62.87 dB at 25 ft and 49.47 -
63.50 dB at 50 ft from the mills. During digestion, noise
ranged from 80.70 - 88.90 dB at 10 ft, 71.87 - 76.20 dB
at 25 ft and 63.10 - 66.80 dB at 50 ft from the mills in the
wind ward direction, whereas in the lee ward direction, it
was 80.57 - 88.90 dB at 10 ft, 71.60 - 75.90 dB at 25 ft
and 62.90 - 66.67 dB at 50 ft from the mills.
There were no significant difference (P > 0.05) in the
noise levels recorded at the wind ward and lee ward di-

Air Quality Impacts of Smallholder Oil Palm Processing in Nigeria 95
rection, indicating that the intensity of noise is unaffected
by wind direction. From these results it will appear that
noise pollution is not of serious concern during local
processing of palm oil. Unlike in the other parameters,
noise do not follow wind direction and was significantly
higher (P < 0.05) during digestion than during boiling.
This is expected because the Lister engine generates
noise during digestion. Noise level was below the FEPA
stipulated limit of 90 dB [55] (Table 5) during boiling
and digestion activities.
During boiling activity, atmospheric temperature
ranged from 27.93˚C - 35.80˚C at 10 ft, 27.43˚C -
35.40˚C at 25 ft and 27.53˚C - 34.03˚C at 50 ft from the
mills in the wind ward direction, whereas it was 27.93˚C
- 35.63˚C at 10 ft, 27.27˚C - 35.50˚C at 25 ft and 27.33˚C
- 35.93˚C at 50 ft from the mills in the lee ward direction.
During digestion, temperature ranged from 27.87˚C -
35.70˚C at 10 ft, 27.23˚C - 35.37˚C at 25 ft and 27.40˚C -
34.07˚C at 50 ft to the mills in the wind ward direction,
whereas in the lee ward direction it was 27.93˚C -
35.40˚C at 10 ft, 27.53˚C - 35.60˚C at 25 ft and 27.17˚C -
34.30˚C at 50 ft from the mills. The temperature was
found to be greater that the permissible limit of 30˚C [55]
(Table 5). Though temperature decreased at increasing
distances from the mills, there were no significant dif-
ferences between the values recorded at the wind ward
and lee ward wind directions and between boiling and
digestion processing activities.
The wind speed ranged from 0.100 - 1.567 m/s during
boiling and 0.133 - 0.933 m/s during digestion, which is
classified as light air in the Beaufort scale. The wind
speed and direction affected the concentration of air
quality parameters but did not influence noise and tem-
perature significantly. Relative humidity ranged from
62.40% - 86.60% during boiling and 60.79% - 86.43%
during digestion, while pressure ranged from 1006.07 -
1008.73 hpa during boiling and 1006.00 - 1008.87 hpa
during digestion. It does appear that relative humidity
and pressure has no differential effects on the air quality
parameters. The high values obtained in some mills and
the distance from the processing activity may be attrib-
uted to reduced cloud cover and the influence of moisture
laden tropical maritime air mass. However, RH appears
to enhance particle deposition [67,68].
The occasional increase in the emission from the
longer distance as compared to short distance in some of
the parameters is associated to the fueling of boiler fuel
during measurement while the digestion activity was
enhanced by the loading rate. Other factors are changes
in wind speed and direction. This basically influenced
both direction (lee and wind ward) measurements.
4. Conclusion
This study investigated the air quality during palm oil
processing by smallholders in Nigeria. The air quality
parameters (NO2, NH3, CO, H2S, SO2, VOC, SPM) dur-
ing boiling activity were found to exceed the threshold
limits. Emissions during digestion activity were however
within the threshold limits. Therefore, emissions during
the boiling process could pose serious environmental and
public health concern which portends negative implica-
tions for environmental sustainability. We recommend
the use of improved burners that could emit fewer pol-
lutants. Also, government should develop environmental
quality guidelines for smallholder oil palm processing
activities to ensure environmental sustainability of their
operations.
5. Acknowledgements
The authors gratefully acknowledges the following un-
dergraduates students of Niger Delta University that par-
ticipated in the field sampling exercise; Eke Rita, Inatimi
Sampson, Obieze Francis, Jeremiah Ikakita, Okonkwo
Amaka, Oghenegueke Ejiroghene, Alaka Evelyn, Ereke
Samuel, Kakiri Gift, Perewarebo Glory, Biriduba Wo-
yengitonyokopa, Clarke Ebisine and Eretinghe Dorcas.
The authors also wish to thank Ally Bedford of IDC Ltd.
for reviewing the manuscript.
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