The contribution of Indonesian livestock to global greenhouse gas emissions

Sutawi¹, Aris Winaya¹, Indah Prihartini¹, Nugroho Tri Waskitho¹, Elfi Anis Saati¹, Oman Sukmana², Juli Astutik², Mohamad Syahri³ and Marsudi⁴

¹ Faculty of Agriculture and Animal Science, University of Muhammadiyah Malang, Malang 65144, East Java, Indonesia
sutawi@umm.ac.id
² Faculty of Social and Political Science, University of Muhammadiyah Malang, Malang 65144, East Java, Indonesia
³ Faculty of Education and Teacher Training, University of Muhammadiyah Malang, Malang 65144, East Java, Indonesia
⁴ Faculty of Economic and Business, University of Muhammadiyah Malang, Malang 65144, East Java, Indonesia

Abstract

Agriculture emissions contribute a large portion of total global emissions. Agriculture accounts for an estimated 45% of total CH₄ emissions. About 80% of agricultural CH₄ emissions are from livestock production, including enteric fermentation and manure management. This study aims to calculate the contribution of Indonesia's livestock sector to world greenhouse gas emissions during the period 2017-2021. Calculation of GHG (CH₄ and N₂O) emissions from the livestock using the Tier-1 method according to 2006 IPCC Guidelines for National Greenhouse Gas Inventories Volume 4. The average GHG emissions from the livestock sector in Indonesia during the 2017-2021 period amounted to 26,826 Gg CO₂-e per year. CH₄ emissions from enteric fermentation contribute 85.71% to livestock sector emissions. Beef cattle contributed 64.32% to the GHG of the livestock sector and 73.22% to the enteric CH₄ emissions of the digestive system.

Key words: enteric fermentation, livestock emission, manure management, methane gas

Introduction

Global warming is the phenomenon of increasing average air temperatures near the surface of the earth over the past one to two centuries (Britannica 2022). In 2013 the Intergovernmental Panel on Climate Change (IPCC) reported that the interval between 1880 and 2012 saw an increase in global average surface temperature of approximately 0.9 °C (1.5 °F). It predicted that the global mean surface temperature would increase between 3 and 4 °C (5.4 °F and 7.2 °F) by 2100 relative to the 1986-2005 average should carbon emissions continue at their current rate (IPCC 2018). The 2018 report by the IPPC, makes clear that a "rapid and far-reaching" transition is required to limit the impact of climate change to 1.5 °C. The major cause of global warming is the greenhouse gas (GHG) emissions (Shahzad 2015). The types of gases and their contribution that have an effect on greenhouses are water vapor (H₂O) by 65%, carbon dioxide (CO₂) by 33%, and others, namely methane (CH₄), nitrous oxide (N₂O), and ozone (O₃) by 2% (IPCC 2014).

Agriculture emissions contribute a large portion of total global emissions. For the past 20 years, agriculture accounts for approximately 20% of global GHG emissions, while forestry and land-use change account for around 7% (Ahmed et al 2020). Agriculture accounts for 80% of total N₂O emissions, mainly from the application of fertilizers, both synthetic nitrogen and manure added to soils or left on pastures (Reay et al 2012). Agriculture accounts for an estimated 45% of total CH₄ emissions (FAO 2016a). About 80% of agricultural CH₄ emissions are from livestock production, including enteric fermentation and manure management (FAO 2016b). Enteric fermentation produces methane as a natural part of digestion in ruminant animals (Magomedov et al 2020). Ruminant livestock are a notable source of atmospheric methane, with an estimated 17% of global enteric methane emissions from livestock (Bell 2019). It accounts for 33% of the total GHG emissions in agriculture and 71% of all agricultural sources of methane (Seresinhe 2021). Activities related to the storage and land application of manure release 12% of the total agricultural CH₄ emissions and represent 25% of all agricultural sources of methane (Seresinhe 2021). Globally, the livestock sector emits circa 5.6-7.5 Gt CO₂-eq year^-1, most of which is attributed to enteric methane (CH₄) from ruminants (33%), while CH₄ and nitrous oxide (N₂O) emissions from manure management account for another 10% of global agricultural emissions (Leitner et al 2021).

The livestock sector is the essential for livelihoods of millions of people in Indonesia. The livestock sector plays an important role in the economy and food security. The livestock sector contributes 1.58% of GDP (MoA 2021a) and provides jobs for 13.56 million households in Indonesia (BPS 2019). The livestock sector has an important role in providing animal food such as meat, eggs, and milk. Indonesians consume beef, chicken, eggs, and milk, 2.20 kg, 6.05 kg, 6.92 kg, and 16.27 kg per capita per year, respectively (MoA 2021b). Population growth, urbanization, changing consumer preferences, and economic progress are boosting the demand for livestock products in Indonesia. Indonesia is seen to have an emerging economy with a high population growth and economic progress which turned out to be a driving force for the growing demand for animal foods. In addition to this positive role, Indonesia's livestock sector also plays a negative role in global warming. This study aims to calculate the contribution of Indonesia's livestock sector to world greenhouse gas emissions.

Materials and Methods

The calculation of GHG (CH₄ and N₂O) emissions from the livestock using the Tier-1 method according to 2006 IPCC Guidelines for National Greenhouse Gas Inventories Volume 4 Agriculture, Forestry, and Other Land Use (Table 1 and Table 2). This method requires data on livestock populations (Table 3), CH₄ emission factors for enteric fermentation, CH₄emission factors for manure management, and default N excretion rate (Table 4). CH₄ and N₂O emissions are then converted to the equivalent of CO₂ per year (Gg CO_2^-e year^-1).

Results and Discussion

CH₄ Enteric Emission

The largest CH₄ emissions from enteric fermentation were produced by beef cattle at 73.22%, while other livestock species each contributed below 10% methane gas (Table 5). Enteric fermentation is fermentation that occurs in the digestive systems of ruminant animals such as cattle, goats, sheep, and camel. Fermentation of feeds in the rumen is the largest source of methane from enteric fermentation (Moss et al 2000). Methane in the rumen is produced by methanogenic bacteria and protozoa (Seresinhe 2021). It has been established that virtually all of the bacteria attached to protozoa are methanogens (Vogels et al 1980) and that these bacteria are responsible for between 25% and 37% respectively of the total methane produced (Newbold et al 1995). The process by which ruminants digest plant material through rumen fermentation into useful products results in the loss of energy in the form of methane gas from consumed organic matter. Methane is produced during the anaerobic fermentation of hydrolyzed dietary carbohydrates in the rumen and represents an energy loss to the host besides contributing to emissions of greenhouse gases into the environment (Bhatta et al 2007).

About 2-15% of the energy in the feed consumed by ruminants cannot be utilized and is released again in the form of methane gas (Haryanto and Thalib 2009). The ruminant animal removes the methane building up in its rumen by repeated eructations of gas through its mouth and nostrils. CH₄ gas formed in the rumen will be removed through 83% eructation, 16% exhalation, and 1% anus (Vlaming 2008). The production of CH₄ gas from enterics is a waste that harms livestock because it is a form of energy loss from the feed consumed. The proportion of gross feed energy converted to CH₄ gas is 6-12% (McCrabb and Hunter 1999). Methane accounts for a significant energy loss to the ruminants, amounting to about 8% of gross energy at the maintenance level of intake and falling to about 6% as the level of intake increases (France et al 1993). Poor feed efficiency is also represented by the high production of enteric fermented CH₄ (Bhatta et al 2007).

Methane emissions from enteric fermentation are influenced by species, maintenance system, and feed type. Methane gas production from a cow reaches 7.53 MJ per day, while goats and sheep 1,255 kJ per day (Haryanto and Thalib 2009). The beef cattle rearing system in Indonesia is divided into three systems, namely 75.97% grounded, 17.13% grounded and released, and 6.90% released (BPS 2017). Types of beef cattle feed in Indonesia are grass, forage, agricultural waste, and concentrates. Feed from agricultural waste contains low crude protein and dissolved organic matter and high crude fiber (Barati 2023). Fibrous feed produces acetic acid and methane (CH₄) higher than grain feed (Prayitno et al 2014). When used as feed for beef cattle, it encourages the formation of more methane gas (CH₄) (Bamualim et al 2008).

Diets containing highly digestible fiber tend to lead to an increase in digestibility and consequently promote CH₄ production (Seresinhe 2021). Factors such as forage maturity and its physical form also influence CH₄ production (Moss et al 2000). CH₄ production is lower in animals fed milled and pelleted forages compared with chopped forages (Hironaka et al 1996). The conversion of feed nutrients into CH₄ gas is produced from secondary products during the rumen fermentation process, namely volatile fatty acids (VFA) and free hydrogen (H₂). VFA consisting of acetic acid, propionic acid, and butyric acid, is a source of energy for ruminants. Acetate and butyrate promote methane production, while propionate formation can be considered as a competitive pathway for hydrogen use in the rumen (Moss et al 2000). The H₂ gas produced will be used by methanogenesis bacteria to form CH₄ gas in the rumen (Rofiq and Anggraeni 2019).

CH₄ Manure Emission

Most methane emissions from manure management were produced by poultry (42.06%) and pigs (32.24%), while other types of livestock each contribute methane gas below 10% (Table 6). Poultry and pigs include non-ruminants that do not have a rumen, so methane gas from enteric fermentation was very low. Enteric fermentation in pigs and poultry occurs only in the post-gastric gastrointestinal tract, such as the caecum and colon. In both digestive organs, there was fermentation of crude fiber and carbohydrates by microorganisms. Such livestock was called hindgut fermenters, which was a type of livestock that ferments feed assisted by microorganisms in the back digestive tract (Suarez-Belloch et al 2013). Carbohydrate consumption has a major influence on the emissions produced by pigs and poultry. Fermentation of carbohydrates in the hindgut was one of the causes of gas formation in livestock manure (Wang et al 2004).

Livestock manure is a source of methane (CH₄) and nitrous oxide (N₂O), two potent GHGs with a 100-year global warming potential (GWP100) 34 and 298 times more powerful than that of CO₂ (IPCC 2013). Manure management determines the high and low greenhouse gas emissions produced by livestock manure. There are three categories of manure management: (a) systems collecting liquid manure (slurry) from animals kept on slatted or solid floors regularly swept clear of any excreta, sometimes with some dilution from washing water; (b) systems producing solid manure (farmyard manure) from animals kept on bedding material, which is collected together with all excreta; and (c) systems producing mixed manure from animals kept on bedding material, but with drainage and separate collection of liquids (Burton and Turner, 2003). Pigs and poultry produce greenhouse gas emissions from manure decomposition processes under anaerobic conditions. This condition occurs when pig and poultry manure is stored in large piles of wet manure. Some of the factors that affect the production of CH₄ manure are the simultaneous presence of high ambient temperatures, high levels of manure organic matter, and anaerobic conditions (Amon et al 2006). Methane is produced by methanogenic archaea under anaerobic conditions (Conrad 2009). If oxygen (O₂) is available, CH₄ is oxidized by methanotrophic bacteria, reducing net manure CH₄ emissions from manure heaps (Petersen et al 2005). In addition to moisture and O₂ availability, CH₄ formation is controlled by temperature, with higher temperature promoting CH₄ production (Chadwick 2005).

N₂O Manure Emission

The most N₂O emissions were produced by beef cattle (49.11%), goats (15.52%), sheep (12.56%), and poultry (12.36%), while other livestock species each contribute N₂O gas below 5% (Table 7). Ruminants were poor nitrogen converters because only 5-30% of ingested nitrogen was taken by the animal and the remaining 70-95% was excreted via feces and urine (Luo et al 2010). Therefore, nitrogen loads in animal excreta, often exceed plant demands and are vulnerable to losses via gaseous emissions and leaching (Selbie et al 2015). This was more critical as the proportion of nitrogen in animal urine has increased with increasing nitrogen intake; although it has remained relatively constant in feces (Rivera and Chará 2021).

The majority of the N₂O emissions from animal agriculture come from manure management, which is the second largest N₂O emitter in the agricultural sector (Seresinhe 2021). Deposition of animal feces and urine is the biggest source of N₂O emissions per year in grasslands (54%), followed by manure application (13%), and nitrogen fertilizers (7%) (Dangal et al 2019). Nitrification and denitrification are the main responsible mechanisms for the production of N₂O in soils, although nitrification-denitrification, codenitrification, and chemodenitrification can also lead to the formation of N₂O given a microbial community and suitable environmental conditions (Hallin et al 2018).

Nitrous oxide in manure is produced primarily via nitrification and denitrification (Chadwick et al 2011). The two main processes that generate N₂O, namely nitrification and denitrification, are strongly influenced by climate and soil factors (Chen et al 2008). The production of N₂O depends on the availability of substrates for both processes, i.e., NH⁺₄ for nitrification and NO^-₃ for denitrification (Zaman et al 2007). The most important factors are the presence of oxygen, temperature, pH, humidity, salinity, and soil management; in the case of denitrification, it also depends on the carbon available for heterotrophic processes (Dalal et al 2003). N₂O emissions are usually highest under moist but not water-saturated conditions, when both aerobic (for nitrification) and anaerobic (for denitrification) microsites prevail (Butterbach-Bahl et al 2013).

GHG emissions 2017-2021

The average GHG emissions from the livestock sector in Indonesia during the period 2017-2021 amounted to 26,826 Gg CO₂-e per year (Table 8). The largest contributor to livestock emissions is CH₄ emissions from enteric fermentation at 85.71%, followed by CH₄ from manure management at 13.82%, and N₂O from manure management at 0.46%. Beef cattle contributed the most to GHG from the livestock sector at 64.32%, followed by goats at 7.66% and sheep at 7.22%. The largest emissions from beef cattle come from CH₄ emitted from the enteric digestive system. Cattle farming is the single most significant contributor to global methane emissions. As the demand for quality meat and milk products rises, methane emissions and global temperatures increase. One of the most effective strategies to ameliorate climate change is to subdue ruminant methane emissions. Feed manipulation remains the most cost-effective approach, attaining a substantial 60% reduction in methane just by meticulously selecting the type or quality of forage and optimizing the concentrate-to-forage ratio in feed (Tseten et al 2022). Adding feed supplement to subsequently increase feed quality and efficiency emerges as a viable strategy in mitigating GHG emissions (Zahra et al 2024).

Conclusion

The average GHG emissions from the livestock sector in Indonesia during the 2017-2021 period amounted to 26,826 Gg CO₂-e per year. CH₄ emissions from enteric fermentation contribute 85.71% to livestock sector emissions. Beef cattle contributed 64.32% to the GHG of the livestock sector and 73.22% to the enteric CH₄ emissions of the digestive system.

Acknowledgments

The project was implemented using a 2022 Research Grant from the University of Muhammadiyah Malang.

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