IJERD – International Journal of Environmental and Rural Development (2023) 14-2

Research article
erd

Environmental Impact Assessment of Air Emission from
Fertilizer Utilization and Rice Straw Burning from Rice
Production in Cambodia
LEAKHENA HANG*
Faculty of Hydrology and Water Resources Engineering, Institute of Technology of Cambodia,
Phnom Penh, Cambodia
Email: leakhena.hang@itc.edu.kh

SREYNEANG THEY
Faculty of Chemical and Food Engineering, Institute of Technology of Cambodia,
Phnom Penh, Cambodia

SELA KONG
Faculty of Chemical and Food Engineering, Institute of Technology of Cambodia,
Phnom Penh, Cambodia

CHENDA LAIFaculty of Hydrology and Water Resources Engineering, Institute of Technology of Cambodia,
Phnom Penh, Cambodia

DALIN UM
Research and Innovation Center, Institute of Technology of Cambodia, Phnom Penh, Cambodia

RAKSMEY YIM
Department of Air Quality, Noise, and Vibration Management, Ministry of Environment,
Phnom Penh, Cambodia
Received 1 August 2023

Accepted 10 November 2023(*Corresponding Author)

Abstract Rice is the most important staple food for feeding nearly half of the world’s
population, and almost the entirety of the population of Asia. An increase in food demandleads to an increase in agricultural residues, resulting in impacts on human health andenvironmental consequences. The current study aimed to estimate the emission of primaryand secondary fine particulate matter attributable to fertilizer from the open burning or ricestraw in Cambodia in terms of country-specific characterization factors (CFs), and to estimate
the human health and ecosystem impact of particulate matter formation and terrestrial
acidification. Additionally, the study aimed to propose an alternative scenario to reduce thenegative impact on human health and the ecosystem. Three scenarios were set to conduct the
study’s assessment, including a baseline scenario representing current farmer practices,
including typical fertilizer application rates and open burning of rice straw after harvest (S0);a scenario reducing fertilizer use to 60% while still allowing open rice straw burning (S1);and a scenario with no open rice straw burning and a 60% reduction in fertilizer use (S2).
Human health damage was calculated in units of Disability Adjusted Life Year (DALY), andecosystem impact was expressed in the units of Potentially Disappeared Fraction of species(PDF/m2/yr) presented under the scenarios. The total human health impact of S0 was
5.35E+01 DALY, S1 was 5.27E+01 DALY, and S2 was 3.75E-01 DALY, while the total
ecosystem impact of S0 was 4.38E-02 (PDF/m2/yr), S1 was 3.60E-02 (PDF/m2/yr), and S2
was 4.85E-03 (PDF/m2/yr). The results of this study indicated that minimizing the use ofchemical fertilizer and zero open burning of agricultural waste can reduce the number ofpollutants that affects human health and ecosystem soil acidification. It showed that reducing
burning straw waste can reduce the toxins that affect human health by 99% and reduce theincrease of soil acidity by 94%.
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Keywords air pollution, DALY, LCA, particulate matter (PM2.5), rice production

INTRODUCTION
Rice has now become a foreign exchange earner for several countries and plays an important role intheir economies (Kumar et al., 2017). In the case of Cambodia, rice production has increased
significantly in the last decades, particularly since the major economic reforms in 1989. The plantedareas of rice increased from 1.9 million hectares (ha) in 1990–1991 to about 2.6 million hectares in
2009–2010 (ASEAN Development Bank, 2012). Favorable weather conditions, an increase in theavailability of rural credit and private investment, technology improvement, new high-yield rice
varieties, application of chemical fertilizer and other inputs are the factors of the increasing rice yield(The World Bank, 2015). Excessive fertilization and mindless use, obviously caused soil salinity,
heavy metal accumulation, water eutrophication, and accumulation of nitrate, considered in terms of
air pollution in the air of gases containing nitrogen and sulfur, which can lead to problems such as
the greenhouse effect (Savci, 2012; Chandini et al., 2019). In the United States, uncontrolled
agricultural emissions will influence states' ability to satisfy global environmental impacts. Despite
recent progress to reduce sulfur oxide (SOx) and nitrogen oxide (NOx) emissions, NH3 plays asubstantial role in PM2.5 formation, and increasing ammonia may increase PM2.5 (aerosols withaerodynamic diameters less than or equal to 2.5 µm) concentrations (Clappier et al., 2021). The
compound of these pollutants such as criteria pollutants of known tropospheric O3, SO2, and PM2.5
affects human health and the environment. Animal production, chemical fertilizer application, land
use land changes, biomass burning, and other agricultural practice is a primary producer of increased
gases and particulate matter (Clappier et al., 2021). Particulate Matter of air pollution is an airsuspended mixture of solid and liquid particles that vary in number, size, shape, surface area,
chemical composition, solubility, and origin. The size distribution of total suspended particles (TSPs)
in the ambient air is tri-modal, including coarse particles, fine particles, and ultrafine particles (Chow,
1995). Agricultural residue open burning in Southeast Asia accounts is up to 43% of the total open
biomass burning (BB) which contributes significantly to air pollution. BB is a source of global air
pollution that typically contains PM2.5 sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide(CO), carbon dioxide (CO2), ammonia (NH3), methane (CH4), and other air pollutants (Le et al.,2020). It is estimated that in developing countries approximately 300,000 to 700,000 people can besaved from premature death if aerosol levels are reduced to a safe level (an Air Quality Index (AQI)
under 100 signifies good or acceptable air quality) (Seinfeld and Pandis, 2016). Thus, this study aims
to investigate the impact assessment of air pollutants emitted from chemical fertilizer and rice straw
open burning from rice production in Cambodia and to analyze human health impact assessment andecosystem impact terrestrial acidification using an analytical tool called Life Cycle Assessment(LCA). Also, to provide a recommendation on negative impact reduction under three scenarios are
set to conduct the study’s assessment.
METHODOLOGY
Data Collection
The chemical fertilizer application data was collected from the survey questionnaires of threeprovinces known as Prey Veng, Svay Reing, and Kampong Thom province. The practical applicationof chemical fertilizer (Urea; DPA; KCl) from the farmers is 27 kg/1ton of rice production; it wasconsidered as scenario S0 and from a lab-scale experiment at Cambodia Agriculture Research
Development Institute (CARDI) which was carried out by the plantation in the column-based
experiment of a known diameter by Lai et al. (2022) based on the soil type used in the experimentwith the application of 11kg chemical fertilizer/1ton of rice production (Chemical fertilizer
application was recommended by CARDI); represent the scenario S1, and the scenario S2 is thecondition of combination chemical fertilizer application recommendation by CARDI with ZeroⒸ ISERD

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burning after harvesting.
Emission Inventory Assessment
Emission of NH3 and NOx from chemical fertilizer and PM2.5, NOX, NH3, and SO2 from rice straw
open burning were estimated according to the methodology of the EMEP guidelines 2016 (EEA
(European Environment Agency) 2016) and Tier1 of the EMEP/EEA guidebook 2019, respectively.
Emission from fertilizer:
𝑀

NH3 = 17/14 ∑𝑚−1(EF𝑎𝑚 × 𝑃 + 𝐸𝐹𝑏𝑚 × (1 − 𝑃))𝑁𝑚𝑖𝑛,𝑚(1)

where NH3 is ammonia emission after mineral fertilizer application [kg NH3]; m is fertilizer type; M
is the number of fertilizer types; EFam is the emission factor on soil with pH ≤ 7 [kg NH3-N/kg N];
EFbm is the emission factor on soils with pH > 7 [kg NH3-N/kg N]; P is the fraction of soils with pH≤ 7 [%/100]; Nmin is mineral fertilizer application [kg N]; 17/14 is the conversion factor from N to
NH3 (NH3 = 17 g/mol and N = 14 g/mol).
Emission from rice straw open burning:
E = Activity data × Emission factor (EF)(2)

where E is the emission of the pollutant; EF is the emission factor obtained from EMEP/EEA tier 1
The EF of PM2.5 140 g/GJ, NOx 91 kg/GJ, SO2 11 g/GJ table 3.5 page 17 in 1.A.2 EMEP/EEA 2019;
Activity data is the amount of burnt source categories.
Where the total amount of rice straw from rice production was calculated following the formuladeveloped by (Shrestha et al., 2013).
Life Cycle Impact Assessment
The human health impact assessment was estimated from particulate matter formation (PM2.5, NOx,
NH3, and SO2), while the Ecosystem impact assessment was estimated from the terrestrial
acidification (NH3, SO2, and NOx).
Human Health Impact Assessment
The human health impact is expressed as DALYs (disability-adjusted life years), the years of life lost
due to death + years of lived with disability, was calculated by applying the ReCiPe 2016 v1.1 (Aharmonized life cycle impact assessment method at midpoint and endpoint level by (Huijbregts et al.,2017).
HI = E × CFs(3)

where HI is human health impact expressed in DALYs; E is the emission of pollutants; CFs is
endpoint characterization factors of human health (yr. kton-1) level in Cambodia.
Ecosystem Impact Assessment (Terrestrial Acidification)
Ecosystem impact = E × CF

(4)

where E is the emission of the pollutant; Ecosystem impact is the potentially disappeared fraction of
species (PDF/m2/yr); CF is the endpoint characterization factors of an ecosystem (species/kg) levelin Cambodia.
To propose a scenario to reduce air pollution that affects human health and ecosystem impact,
the estimation was carried out under three scenarios. First scenario S0; the baseline is the conditionof using chemical fertilizer (Urea, DAP, KCl) and rice straw open burning by farmers practiced fromthe survey. The second scenario (S1), is the application of chemical fertilizer (Urea, DAP, KCl)Ⓒ ISERD

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recommended by CARDI with the practice of rice straw open burning by column based-experimental(Lai et al., 2022). The third scenario (S2); the optimization is the application of chemical fertilizer
NPK recommendation by CARDI with zero burning of rice straw.
RESULTS AND DISCUSSION
Emission Inventory
The estimation of air pollutants NH3, NOx, PM2.5, NOx, and SO2 from chemical fertilizer and ricestraw open burning is expressed as kg/1ton of rice production. Figure 1 reveals the concentration ofemissions released from chemical fertilizer and rice straw open burning under the three studied
scenarios. It is noticed that the pollutants released from the application of fertilizer by farmers
practiced (S0) are higher than the pollutants emitted from the reducing fertilizer application
recommended (S1) by 76%. In addition, the result showed that rice straw open burning is the majorityof source of PM2.5 and SO2 (Fig. 1) of scenario S2. The study by (Lorn et al., 2022) investigatingPM2.5 from fertilizer usage, fuel combustion, and straw residue burning revealed that 51.56% of thetotal emission in the study is generated by rice straw open burning and 24.10% generated fromfertilizer.

Fig. 1 Emission of pollutants of the studied scenarios from 1 ton of rice production
Life Cycle Impact Assessment
Life cycle impact assessment from two endpoint categories, human health impact (the particulatematter formation) and ecosystem impact (terrestrial acidification) are estimated from the emission ofchemical fertilizer and rice straw open burning, is represented as kg/ton of rice production, areexpressed as DALYs and PDF/m2/yr, respectively. The human health impact estimation revealed thehighest value in scenario S0 (5.35E+01 DALYs) if compared to scenario S1 (5.27E+01DALYs) andS2 (3.75E-01DALYs).
Figure 2 showed that the human health impact is contributed majority from PM2.5 and SO2 which
contributed from rice straw open burning, following by NOx, and NH3. It is also noticed that thehighest value of ecosystem impact estimation is found in scenario S0 (4.38E-02 PDF/m2/yr), while
S1 and S2 are 3.60E-02 PDF/m2/yr and 4.85E-03 PDF/m2/yr, respectively (Fig. 3). Based on thefinding result, SO2 is the most contributor to ecosystem impact following by NH3, and NOx,
respectively. As can be seen in the result, a great negative impact on both human health impact andthe ecosystem impact happened under scenario S0. The particulate matter formation from bothprimary and secondary sources of rice straw open burning practiced and excessive application ofchemical fertilizer are seriously affecting both human health and the ecosystem. In the case of easternand north-central China, regions with large population densities and high levels of PM2.5,
approximately 4% of all-cause mortality in the country can be avoided (95% confidence interval: 17%) by reducing emissions of primary particulate matter and gaseous particulate matter precursors,
and thus lower ambient concentrations of PM2.5 (Zhao et al., 2011). Mahmood and Gheewala, (2020)Ⓒ ISERD

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stated that rice straw open burning which emitted the majority of PM2.5, exhibited significant impacts
on the environment, terrestrial acidification, freshwater eutrophication, and human damage to ozone
formation. To reduce the amount of particulate matter formation and terrestrial acidification emitted
to the environment which affects greatly human health and the ecosystem, it is suggested to stop theactivity of open burning and excessive use of chemical fertilizer so it can prevent damage to humanhealth by 99% and to the ecosystem by 94%.
In Asia, managing rice straw remains a challenging matter. The available information andknowledge are scattered and either cannot reach the target practiced (farmers, and rural people) (Van
Hung et al., 2020). The common management practice of rice straw is to leave straw to integrate into
the soil known as rice straw incorporation. The incorporation practice can improve soil fertility yetadequate time must be allowed to ensure the effectiveness of the decomposition, thus it may not be
considered by a short cycle of crop growing practice (Zhang et al., 2021). Cattle feed and mushroom
cultivating are other alternatives to rice straw management (Gummert et al., 2020), andrecommended rice straw used in biochar studies is suggested (Ly et al., 2015; Chandra andBhattacharya, 2019). However, positive and effective results can be obtained unless all parties must
involve (farmers and government) and recognize the serious effect of the uncertain method ofmanaging rice straw.

Fig. 2 Human health impact from particulate matter formation

Fig. 3 Ecosystem impact from terrestrial acidification
CONCLUSION
Chemical fertilizer and rice straw open-burning activity emitted pollutants that are harmful to bothhuman health and the ecosystem. Rice straw open burning released the majority of PM 2.5 and SO2
while the most pollutant emitted from chemical fertilizer is NOx. Emissions released from rice straw
open burning alone cause great effects on both human health and the ecosystem. It is suggested tostop the activity of open burning and the excessive practice of applying chemical fertilizer, therefore
it can reduce 99% of human health impact and 94% of ecosystem impact.
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To tackle this issue, educating people about the harmful effects of burning rice straw and otheragricultural waste is crucial. Additionally, implementing improvements in straw utilization rates andminimizing open-field burning are vital steps towards establishing a circular bio-economy thatutilizes agricultural straw as a valuable resource. Moreover, it is important to invest in improving
technology for mushroom and ruminant farming. Lastly, promoting the elimination of agricultural
waste and open burning is crucial for a sustainable future.
ACKNOWLEDGEMENTS
This paper was funded by Cambodia Higher Educational Improvement Project (credit No.6221-KH).
The author would like to thank the Institute of Technology of Cambodia for all its facilities.
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