Greenhouse gas emissions from piggery and biogas digesters in the north of Viet Nam

Vietnam Journal 
of Agricultural 
Sciences 
ISSN 2588-1299 VJAS 2020; 3(4): 843-853 
https://doi.org/10.31817/vjas.2020.3.4.07 
843 Vietnam Journal of Agricultural Sciences 
Received: August 3, 2020 
Accepted: January 20, 2021 
Correspondence to 
phamdung86@gmail.com 
Greenhouse Gas Emissions from Piggery 
and Biogas Digesters in the North of 
Vietnam 
Pham Van Dung1, Duong Cong Hoan2, Jacobo Arango3, Tran 
Dai Nghia4, Nguyen Tri Kien1, Ashly Arevalo3 & Sabine 
Douxchamps1 
1Alliance of Bioversity International and International Center for Tropical Agriculture 
(CIAT), Hanoi 143330, Vietnam 
2Department of Livestock Production, Ministry of Agriculture and Rural Development, 
Hanoi 124332, Vietnam 
3Alliance of Bioversity International and International Center for Tropical Agriculture (CIAT), 
Apartado Aéreo 6713, Cali, Colombia 
4Institute of Policy and Strategy for Agriculture and Rural Development (IPSARD), Hanoi 
124332, Vietnam 
Abstract 
Increases in pig farm densities have caused great pressures on waste 
management systems and produce massive manure and urine 
quantities in Vietnam. This study aimed to identify the role and 
contributions of biogas digesters to better manage the sources of 
greenhouse gas (GHG) emissions from pig wastes for different types 
of pig farms in the north of Vietnam. Four provinces, namely Thanh 
Hoa, Phu Tho, Thai Binh, and Vinh Phuc, were identified. A total of 
24 farms were purposively selected including 16 small-size farms 
and 8 larger-size farms. The findings showed that GHG emissions 
from small-size farms (154.8 t CO2-eq.yr
-1) did not significantly 
differ from the amounts measured in larger-size farms (139.1 t CO2-
eq.yr-1) in the four surveyed provinces. The sampling position did 
not significantly affect the GHG emission rates, with 173.9 t CO2-
eq.yr-1 inside piggeries and 120.8 t CO2-eq.yr
-1 outside the outlet of 
the biogas digesters (p-value = 0.09). N2O emissions require further 
measurements at different farm sizes and sites. These results 
confirmed that the pig waste management of biogas digesters for 
both small-size and larger-size pig farms is not completely efficient 
and that efforts need to be invested in to mitigate GHG emissions in 
pig production. Reducing pig density per piggery is highly 
recommended. The application of other alternative aerobic or 
anaerobic digestion technologies like vermicompost, effective 
microorganisms, and composting should also be encouraged and 
promoted. 
Keywords 
Biogas digester, emission rate, greenhouse gas, pig production, 
Northern Vietnam 
Greenhouse gas emissions from piggery and biogas digesters in the North of Vietnam 
844 Vietnam Journal of Agricultural Sciences 
Introduction 
Livestock is one of the fastest-growing sub-
sectors of agriculture in Vietnam. In the past, 
livestock raising activities based on feeding 
agricultural by-products were popular in 
smallholder farms in all agro-ecological zones. 
However, these have been sharply shifting from 
small-size to larger-size or industrial levels 
during the last decade. Under the orientations of 
the livestock production development strategies 
of the Ministry of Agriculture and Rural 
Development of Vietnam (MARD) from 2008 to 
2020, the herd size and growth rate of livestock 
in general has quickly advanced towards 
industrial productions in areas where appropriate 
conditions for livestock raising, such as types of 
animals, housing systems, location, farm size, 
land for waste disposal, and policy support, are 
met. Consequently, animal populations have 
remarkably increased, especially pig herds, 
which reached 27.4 million heads in 2017 at an 
annual growth rate of 2.3% between 2013 and 
2017. More than 14,858 intensive pig farms at 
different production levels are nationally listed 
(General Statistical Office of Vietnam, 2019). 
Two-thirds of the intensive farms are in the Red 
River Delta and Northern provinces and the rest 
are in the South. 
Manure management is one of the mitigation 
components of agriculture under the Nationally 
Determined Contribution (NDC)'s framework that 
the Vietnam government is undertaking to 
implement during the period of 2020-2030. 
To achieve its mitigation goals, the 
Vietnamese government has planned specific 
actions to develop an additional 300,000 biogas 
digesters, which are expected to mitigate 1.92 
million tons of CO2-equivalent (CO2-eq), and 
improve animal feeds, which are anticipated to 
mitigate 0.13 million tons of CO2-eq. These plans 
are essential contributions to the Vietnamese 
government's policy implications and international 
commitments on climate change prevention, global 
warming, and GHG mitigations. Previous reports 
have shown that manure management practices 
contributed to 15.1% of the total agricultural 
emissions between 1992 and 2012 (Misselbrook et 
al., 1996; USAID, 2012). I ...  before and after the 
use of biogas digesters remained high. Several 
gaps in knowledge could be addressed by future 
studies. The study initially evaluated the 
efficiency of GHG emission reduction in biogas 
digester systems. Comparisons with other waste 
management technologies are needed, such as 
composting technology, solid and liquid manure 
separation technology, EM technology, etc. This 
knowledge will be helpful to target interventions 
for different manure management technologies 
and prioritize them for government programs. 
Care should be taken when extrapolating 
research results to other regions, and more 
Pham Van Dung et al. (2020) 
https://vjas.vnua.edu.vn/ 851 
assessments are needed in larger-size and small-
size pig farms in different geographical zones to 
consolidate findings of emission levels at 
different production scales. Feed sources play an 
important role in total GHG emitted. Most 
households currently use concentrated feed, and 
the comparative emissions following feeding 
with alternative products should be investigated. 
This study analyzed emissions at the time of 
sampling, but did not evaluate emissions over a 
longer time period, especially changes in 
seasonal emission rates. Future studies could 
focus on the impact of seasonal environmental 
changes, such as the fluctuation of temperature 
and humidity, on emission rates over time. These 
results were restricted to specify which type of 
pig (market pig, sow, and piglet) had high GHG 
emission rates per pig head. Similarly, the results 
did not identify GHG emission rates for the 
specific type of feed input. Further research is 
needed to provide additional data on GHG 
emission and feed intakes to confirm these 
results. 
Conclusions 
Overall, the consequences of this inefficient 
process were poor GHG emissions mitigation, 
the lack of organic matter in the digestates, poor 
quality of biogas, spreading smells of biogas, and 
loss of nutrients to the environments. The study 
confirmed that the biogas digesters were 
overloaded and the quality of manure 
decomposition was not optimal. The GHG 
emission amounts (tCO2-eq.yr
-1) from pig wastes 
inside and outside of the biogas digesters had 
great potential to cause greenhouse effects and 
global warming. However, the GHGs emission 
rate did not significantly differ between the 
small-size and larger-size farms in the four 
surveyed provinces. Sampling position (between 
inside piggeries and outside the outlet of the 
biogas digesters) did not significantly affect the 
GHG emission rate. These results confirmed that 
the pig waste management of biogas digester 
systems for both small-size and larger-size pig 
farms was not efficient and that efforts need to be 
invested in to mitigate GHG emissions in pig 
production. This case study suggested that 
adjustments in pig population numbers and the 
density of pig heads per piggery floor area unit 
during a pig production cycle are highly 
recommended. Modifications to the biogas 
digester structure are also necessary to separate 
solid pig manure and urine. Otherwise, the 
application of other alternative aerobic or 
anaerobic digestion technologies like 
vermicompost, effective microorganisms, and 
compost should also be encouraged and 
promoted when economic, income, and 
environmental benefits are met. Biogas digesters 
in pig production have a significant role to play 
in the Vietnam government’s mitigation 
strategies, as well as from the perspective of 
biosafety and animal husbandry policies. 
Acknowledgments 
The authors would like to gratefully 
acknowledge anonymous local supporters, the 
People’s Committees, and the Department of 
Agriculture and Rural Development of the 
surveyed provinces for approving the interviews 
and arranging the site visits. Special appreciation 
and thanks also to the farmers in the visited sites 
for their invaluable contributions and openness in 
sharing with us their experiences and insights. 
This study was funded by the Livestock and 
Environment flagship of the CGIAR Research 
Program on Livestock, which is carried out with 
support from CGIAR Fund Donors and bilateral 
funding agreements. 
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