IJERD – International Journal of Environmental and Rural Development (2021) 12-1

Research article
erd

Assessment of Biogas Production Potential from Commercial
Pig Farms in Cambodia I7de
LYHOUR HIN*nBiogas Technology and Information Centerand Faculty of Agricultural Engineering,t

Royal University of Agriculture, Phnom Penh, Cambodia
Email: hlyhour@rua.edu.kh
4.
7
Royal University of Agriculture, Phnom Penh, Cambodia
2

BUNTHAN NGO
LYTOUR LORw
Biogas Technology and Information Centerand Faculty of Agricultural Engineering,
Royal University of Agriculture, Phnomo Penh, Cambodiard
SUYHEANG SORNs
Biogas Technology and Information Centerand Faculty of Animal Science,

Royal University of Agriculture, Phnom Penh, Cambodia

DYNA THENG
Biogas Technology and Information Center and Faculty of Agricultural Engineering,
Royal University of Agriculture, Phnom Penh, Cambodia

CHANPHAKDEY DOK
Biogas Technology and Information Center, Royal University of Agriculture, Phnom Penh,
Cambodia

SOKHOM MECH
Biogas Technology and Information Center, Royal University of Agriculture, Phnom Penh,
Cambodia

CHAN MAKARA MEAN
Biogas Technology and Information Center, Royal University of Agriculture, Phnom Penh,
Cambodia

SOVANNDY YUT
Biogas Technology and Information Center, Royal University of Agriculture, Phnom Penh,
Cambodia

MAKARA LAY
Biogas Technology and Information Center, Royal University of Agriculture, Phnom Penh,
Cambodia; Laboratory of Organic Electronic, Department of Science and Technology,
Linköping University, Norrköping, Sweden

BART FREDERIKS
Independent Bioenergy Consultant and Biogas Technology and Information Center,
Royal University of Agriculture, Phnom Penh 12401, Cambodia
Received 28 December 2020

Accepted 30 June 2021

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IJERD – International Journal of Environmental and Rural Development (2021) 12-1

Abstract Commercial pig farms in Cambodia are increasing, representing 30% of the overall
pig production in 2018. To run the farms, huge quantity of water is used on daily basis, and its
large proportion ends up being wastewater that can cause air and water pollution, fly-related
illnesses, and methane emissions. In response, anaerobic digestion (AD) is applied to convert
waste into energy. Covered lagoons are an anaerobic biodigester that has long been used forcommercial biogas plants in Cambodia due to acceptable investment cost and favorable climaticconditions for biogas production. However, lack of local technical data and technicalassessment is a barrier to wider implementation of biogas systems in the country. Therefore, thestudy was conducted to explore the characteristics of commercial pig farms and wastewater use;
to analyze the quality of biogas compositions from different covered lagoons; and to estimate
biogas production, electricity generation, and CO2 reduction equivalent from the collected data.
The study was started from January to October 2020, selecting 9 farms with evaporative
cooling systems for in-depth interviews, along with direct observations, biogas analysis, andpower analysis. The findings indicate that all the studied farms were fattening farms operated
under purchase contract with private companies. Pig production varied from 2,800 to 7,200
head per cycle, with two cycles per year. Moreover, daily wastewater was 0.033 m3 d-1 head-1,
with dry matter (DM) accounting for 0.9%. Annual biogas production and electricity generation
were 32.7 m3 y-1 head-1 and 42.5 kWh y-1 head-1, respectively. Biogas quality was 59.5% CH4,
31.5% CO2, 1.3% O2, and 2,256 ppm H2S. With biogas systems, individual farms could reduce
CO2 emission by 0.676 tCO2eq y-1 head-1, which is economically and environmentally
beneficial. However, a business model should be taken into account for successful
implementation.
Keywords CO2 reduction, covered lagoon, methane emission, pig manure

INTRODUCTION
Pork is considered an important protein source for daily Cambodian diets. In this country, an average
person eats 17.6 kg of meat per year, of which 9.29 kg is pork. Likewise, annual domestic demands formeat in 2018 was estimated at 285 thousand tons, and pork alone accounted for 52.8%. This highdemand led to a 126% increase in local pig production between 2014 and 2017, from 2.44 million toapproximately 3.18 million heads. A tendency toward large-scale production has emerged, as
commercial pig farms rose by 30% in 2018 (MAFF, 2019). Commercial pig farms in Cambodia arefarms with more than 100 fattening pigs, or more than 50 sows. There are around 500 farms inoperation across 10 provinces, with 30-40% concentrated in Kampong Speu Province (NBP, 2019).
Commercial pig farms in Cambodia are operated similarly with Thailand because they use evaporative
cooling systems to maintain optimal temperatures inside the barns from 25 to 27 0C (Thanapongtharm,2018). Such operation is vital for pig growth and disease prevention. For secure market and prices,
farms turn to contract farming with private companies, such as C.P. Cambodia Co., Ltd., that provide
both technical and financial support. Farm operation differs by pig type. In Cambodia, pig farms areclassified into breeding farm and fattening farm. Among them, fattening farms are more popular.
Fattening farms have three categories: small-sized (100 - 1,000 heads), medium-sized (1,001 - 5,000
heads), and large-sized (>5,000 heads) (MAFF, 2018).
Pig farms normally use large amounts of water for pig drinking, pig bathing, and barn cleaning.
Daily water use rates vary by production type and pig weight. It is reported that average daily required
water rates for breeding farms, fattening farming, and nursery farms are 92, 48, and 32 L d -1 head-1,
respectively. However, a large proportion (50-70%) ends up being wastewater (Nokyoo, 2016).
Improper treatment of wastewater is associated with odor, flies, water pollution, and greenhouse gas
emission. Some key elements used as pollutant indicators include chemical oxygen demand (COD),
biological oxygen demand (BOD), total Kjedahl nitrogen (TKN), and total suspended solid (TSS). A
study by Tokhun (2010) indicates that untreated wastewater from large-scale pig farms in ThailandⒸ ISERD

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contains 4,889 mg L-1 COD, 3,555 mg L-1 BOD, 481 mg L-1 TKN, and 2,317 mg L-1 TSS. These
parameters are too high to be directly discharged into natural lakes. In the Cambodian wastewater
standards for public water areas and sewers, COD, BOD, TSS, and nitrate (NO3) must be no more than100, 80, 80, and 20 mg L-1, respectively (Council of Ministers, 1999). Thus, sound waste management
is strongly required, as it is important for the sustainable operation of pig farms. One of the mosteffective wastewater treatment methods is the adoption of anaerobic digestion (AD). AD is known as aprocess under which organic matters, mainly in the form of fine particles, are fermented with theabsence of air. The process consists of four stages: hydrolysis, acidogenesis, acetogenesis , andmethanogenesis, with biogas produced as a final product and convertible into energy (Deublein andSteinhauser, 2011). Biogas is a gas mixture that contains 50-70% methane (CH4), 30-40% carbon
dioxide (CO2), and other trace elements (EESI, 2017). CH4 contained in biogas is the only source ofenergy such as heat and electricity. Nevertheless, it is harmful to the environment, if released into theatmosphere, because it is 28 times more powerful than CO2 in terms of global temperature potential(GTP) for 100 years (IPCC, 2014). In contrast, converting biogas into electricity or upgrading it into
bio-methane can reduce its harmfulness.
To promote manure management, the National Biodigester Program (NBP) was established in
Cambodia in 2006 to turn cow manure into biogas for cooking and lighting. The program has built
nearly 30 thousand biodigesters for smallholder farmers nationwide. In recent years, attention has been
turned to large-scale biogas systems, which are covered lagoons. Covered lagoons are an AD
technology, commonly used in commercial pig farms in Cambodia. It is reported that there are 44
covered lagoons in operation across the country (NBP, 2019). This number is still considered low incomparison to the potential pig farms and other biogas resources. This is due to lack of necessary
documents and knowledge, or biogas skills. Therefore, in-depth studies on commercial pig farms are
deemed vital for solving problems with wastewater and for economic profitability through energy
generation.
OBJECTIVE
The objectives of this study were (1) to explore the characteristics of commercial pig farms andwastewater use; (2) to analyze the quality of biogas from covered lagoons; and (3) to estimate methane
production, electricity production, and CO2 reduction equivalent.
METHODOLOGY
The selection criteria for pig farms were farms that had thousands of pigs, used evaporative coolingsystems, and were interested in setting up biogas systems. However, the scope of this research was
based on a one-year study period only, from January to October 2020. To represent diverse pig farmcharacteristics, 9 commercial farms were selected from 6 different provinces: 5 from Kampong Speu
and 1 each from Kampong Chhnang, Kampong Cham, Kampong Thom, Siem Reap, and Kratie. Morefarms were selected from Kampong Speu, as this province had the greatest farm number in the country.
The study procedure was arranged by face-to-face interviews with farm owners on the site, direct
observation, biogas analysis, and power analysis.
Materials
Biogas quality is an important indicator to determine generator efficiency. A 5000 gas analyser,
supplied by Geotech, UK, was used to analyze biogas quality based on the percentage of CH4, CO2, O2,
and H2S in ppm with the maximum of 5,000 ppm.
Peak load is considered a vital indicator to determine the generator size for the farm. A HiokiⒸ ISERD

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PW3365-20-01/5000 power logger was used to measure daily peak loads. It is capable of measuring
three-phase voltage with high electrical current of up to 5,000 A.
Sampling Methods and Data Analysis
In the study, a set of questionnaire was used to collect information on pig type, business type, pig
number, barn number, cycle number, and duration within a cycle, as well as plans to increase farm size
within the next few years. Moreover, information on sources of farm power supplies, existing biogas
systems, biogas system type, generator type, and operation was also gathered. Annual electricity
demand was estimated based on collection of electricity bills from the farms. All the information wasverified by direct observation.
In the sampling process, biogas was directly measured before and after desulfurization—a process
for removing hydrogen sulfide from the biogas systems. As desulfurizing systems did not function,
biogas quality was only measured in the outlet pipe from covered lagoons. The measurement lasted 2min, and average values were plotted from at least 3 different measurements. Before measuring new
samples, the biogas analyzer was flushed. In the sampling process, peak loads were measured byattaching the power logger to the electricity panels of the farms for 1 hour. Night load was not recorded
due to low electricity demand. Nevertheless, peak load recording was possible for a few farms only due
to blackouts.
Total daily wastewater production from pig farms was estimated by combining daily water use forindividual pigs, daily manure, and urine rate. In Thailand, daily wastewater left from cleaning, bathing,and drinking is estimated at 24 L d-1 head-1 for fattening farms (Kulpredarat, 2016). Because Thai pig
farms share similarity with Cambodia, wastewater rate used in this study was assumed to be 30 L dhead-1, about 20% more for conservative estimation. In this study, manure production used forindividual pigs was 1.5 kg d-1 head-1 (Mek et al., 2018), and urine rate was assumed to be 2.5 L d-1
head-1. These estimated values were roughly similar to the data in Thailand, where daily manure andurine production for typical fattening farms are 1.2-1.4 kg d-1 head-1 and 3.0-3.2 L d-1 head-1,
respectively (Nokyoo, 2016). Besides that, the evaporation rate was also included and assumed to be
0.5 m3 d-1 barn-1.

Fig. 1 Diagram of full biogas systems in a typical pig farm, but in Cambodia,
desulfurizing systems, gas meter, and flare are missing
Daily biogas production was estimated by multiplying manure dry matter (DM) with biogas yield.
It is reported that average pig manure contains 20% DM (DEFRA, 2011), and that biogas yield is 0.33
Nm3 kg-1 DM based on the experimental result by the Biogas Technology and Information Center(BTIC). Electricity production potential was calculated by multiplying biogas production with theconversion factor that varies from 1 to 1.7 depending on scale and average loading rate of the generator.
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From biogas systems, CO2 emission can be reduced in two ways: reduction by not emitting CH4
directly into the atmosphere and reduction by using it to run biogas generators instead of gridelectricity. In this regard, CO2 reduction by avoidance of CH4 release is equal to CH4-to-CO2 equivalentx CH4 density x Annual CH4 production. Meanwhile, CO2 reduction by avoidance of grid electricity isequal to electricity-to-CO2 equivalent x annual electricity demand met by methane production.
Descriptive statistics and frequency distribution were applied to analyze the data using MS Excel.
To determine relations between CH4 and O2, or CH4 and H2S, a simple linear regression was used at α
= 0.05 probability level using R program 4.0.4, available for free online.
RESULTS AND DISCUSSION
Table 1 Characteristics of commercial pig farms in the studied areas (N = 9)
Variable description
Fattening farm
Yes
No
Contract farming
Yes
No
Production cycle (cycle/year)
Barn Number<5≥5
Production size (head/cycle)< 10001000 – 3000
3001 – 4999
≥ 5000Plan to increase production
Yes
No
Sources of Energy supply
Electricity grid
Other Energy sources
Existing covered lagoons (m3)YesNo
Biogas systems in operation
Yes
No
Generator range (kVA)< 100
100 – 200
> 200
Generator typeNew
Modified
Pig number per barn (head/barn)
working days (d/y)
Daytime peak load (kW)Max peak load (kW/barn)

Frequency(N = 9)Percentage
(%)

9
0

100%
-

9
0

100%
-

3
6

33%
67%

0
2
5
2

22%
56%
22%

4
5

44%
56%

5
4

56%
44%

4
5

44%
56%

3
6

33%
67%

0
2
1

67%
33%

0
3

100%

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Mean ± SE

Min

Max

2
5.6 ± 0.6

4

94,194 ± 470.4

2,800

7,200

4,085 ± 564

2,965

4,761

186 ± 49.1

100

375

749 ± 11.8
330
59.8 ± 9.4
9.1 ± 0.4

740

800

32
7.8

97
10

IJERD – International Journal of Environmental and Rural Development (2021) 12-1

Pig Farm Characteristics and Wastewater Use
The studied farms were all fattening farms operated under official contract with private companies(Table 1). The farms had two cycles per year, 5.5 months each. In early production, the farms were
given piglets and had to sell back pigs to the contracting companies at the end of the cycle, also known
as all-in/all-out batch operations. The number of barns varied from 4 to 9, with an average of 5.6 barns
per farm. Average production size was 4,194 heads per cycle, but varied from 2,800 to 7,200 heads per
cycle. No farms had pigs less than 1,000 heads per cycle. Of all the farms, 7 were medium-sized farms(1,000 to 5,000 heads); 2 were large-sized farms (>5,000 heads).
In Table 1, when asked about plans to increase production within the next few years, about 44%of the farm owners said yes. The main electricity supplies came from the local electricity grid. Of all
the interviewees, 5 depended solely on EDC, while 4 also used biogas as an alternative. The biogas
systems in the farms were simple covered lagoons that had different sizes, but the average value was
4,085 m3. Only 3 farms had the systems in operation, while another one just stopped due to problems
with the biogas generator. In addition, the farms that had biogas systems preferred to second-hand,modified diesel generators for economic reasons.
Farm electricity was mainly consumed by evaporative cooling systems and to some extent bypumping and lighting (Table 1). Average maximum daytime peak load the farms was 59.8 kW, butvaried from 32 to 97 kW according to the production size. Maximum peak load per barn was alsomeasured with full operation of evaporative cooling systems. It was 9.1 kW and varied from 7.8 to 10
kW. However, peak loads were low at night, in cold seasons, and in early production.
Table 2 Estimated total wastewater production in the fattening farms (N = 9)
SourceWater
Dung (fresh)
Urine
Evaporation
Total waste water
DM content
Total DM
BiogasUnit
m3 d-1
t d-1
m3 d-1m3 d-1m3 d-13 -1
m d head-1%
t d-1
Nm3 d-1
Nm3 y-1
Nm3 y-1 head-1

Average ± SE
125.8 ± 14.1
6.3 ± 0.7
10.5 ± 1.2
2.8 ± 0.3
139.8 ± 15.7
0.033 ± 0.004
0.9%
1.3
415
137,033
32.7

Wastewater rate produced from pig bathing and barn cleaning was 125.8 m3 day-1 in each farm
(Table 2). Fresh manure and urine production was 6.3 t d-1 and 10.5 m3 d-1, respectively. Evaporation
rate was estimated at 2.8 m3 d-1, so total wastewater produced by individual farms was 139.8 m3 d-1, or
0.033 m3 d-1 head-1. DM accounted for 0.9%, so average daily biogas production in each farm wasestimated to be 415 Nm3 d-1, or equivalent to 137,033 Nm3 y-1. Thus, biogas production rate per pig
was 32.7 m3 y-1 head-1. However, this calculated value was just an average because swine growth stage
affects biogas production yield (Amara et al., 2015).
Biogas Quality
In Table 3, CH4, CO2, O2, and H2S were 59.5%, 31.5%, 1.3%, and 2256 ppm, respectively. O2
measured in this study might come from air that had entered the biogas system. Its presence suggeststhat there is also N2 in the biogas, in a ratio of approximately 4:1. So 1.3% O2 will mean 5.2% N2,
possibly more. Biogas also contains water vapor, which may then lower CH4 content. So, less air needsⒸ ISERD

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to be mixed for the generator. High H2S content may reduce the generator lifespan through corrosion.
Thus, desulfurizing systems are needed to lower its content before running any biogas generator.
Nevertheless, the measured biogas quality was similar to a study by Sweeten, Fulhage, and Humenik(1981), who reported 50-60% methane, 40-50% CO2, and H2S <10,000 ppm. Dumont (2015) reported
higher methane content (60-70%), lower CO2 content (30-40%), and H2S (10-20,000 ppm) for biogas
produced from organic waste.
Table 3 Biogas quality measured on the pig farms that had biogas systems (N = 9)
Biogas quality
CH4
CO2
O2
H2S

Unit
%
%
%
ppm

Mean ± SE
59.5 ± 3.0
31.5 ± 2.8
1.3 ± 0.7
2,256 ± 504

Min
52.0
26.9
0.1
818

Max
64.5
40.0
3.0
3,295

Fig. 2 Relationships between CH4 and H2S (left); CH4 and O2 (right); sample size ( N = 9)
In Fig. 2, CH4 had a negative relationship with both H2S and O2, meaning that increased
concentrations of H2S or O2 may lower CH4 content. H2S reduction is made possible by desulfurization
through the use of desulfurizing systems, and O2 reduction by preventing air from entering the systemthrough proper sealing. However, Siripat (2019) and Deublein and Steinhauser (2011) reported that
increased H2S content reduces biogas quantity, not CH4 directly.
Methane Production, Electricity Generation and CO2 Reduction
In table 4, annual electricity production in each farm was estimated to be 178,142 kWh y-1, but varied
by farm size. Pig weight varies by month, or by age, so does daily manure production. Daily biogas
production also varies accordingly, but tends to increase constantly from early production to the end of
the cycle. At the same time, electricity demands at the farms also showed variations, as the need forbarn cooling varied with pig age and daily outside temperature. Thus, not all biogas could be used to
produce electricity. In the study, the estimated average annual electricity demand for each farm was
166,667 kWh y-1, and electricity produced from biogas could meet only an average of 75%, or 127,700
kWh y-1. This estimation may vary according to farm production size.
Biogas systems also contribute to reduction in greenhouse gas emissions. In this study, the annual
CO2 reduction equivalent was estimated to be 2,832 tCO2eq y-1 in each farm. This amount was huge,and further reduction could be achieved when more and more farms turn to using biogas systems. In
short, about 0.676 tCO2eq y-1 head-1 could be reduced per pig. This CO2 reduction equivalent was
higher, when compared to Peerapong and Limmeechokchai (2017), whose estimatin was 0.469 tCO2eqⒸ ISERD

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y-1 head-1 for a typical pig farm in Thailand. Thus, a business model should be considered for wider
adoption of biogas systems for farm benefits and for the environment.
Table 4 Estimation of electricity demand potential and CO2 reduction (N = 9)
Description
Potential electricity production
Estimated electricity for farm coverage
Estimated farm demand
Percentage of farm coverage from biogas
CO2 reduction
From CH4 reduction equivalent
From grid electricity equivalent
Total
CO2 reduction per head/year

Unit
kWh y-1
kWh y-1
kWh y-1%
Unit
tCO2eq y-1
tCO2eq y-1
tCO2eq y-1 head-1

Value
178,142
124,700
166,667
75
2,751
82
2,832
0.676

CONCLUSION
Commercial pig farms in Cambodia were studied in terms of pig production, wastewater use for biogas
systems, electricity demands and contribution to CO2 reduction. It can be seen that these farms are
typical, and some already used covered lagoons to produce biogas. The farm size is huge, and there is ahigh potential for further development of biogas systems that may benefits socially, economically, andenvironmentally. However, further studies shall be made on profitability of actual biogas investment asa model for farm investment and policy making.
ACKNOWLEDGEMENTS
The study was made possible thanks to the project “Reduction of Greenhouse Gas Emission throughPromotion of Commercial Biogas Plant in Cambodia” implemented by United Nations Industrial
Development Organization (UNIDO) that not only provided funding, but also continuously assisted instrengthening the research team. Many thanks may also go to the farm owners that allowed for theinterviews and site visits and to local authorities that helped facilitate the connections among us.
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