Greenhouse Gas Emissions: Quantifying Methane Emissions from Livestock

Problem statement: The rearing of animals for domestic consumption an d export invariably lead to the production of methane as a p roduct of digestion. This study investigated the emission of methane from Malaysian livestock betwee n 1980 and 2008. Approach: Seven categories of animals identified were camel, buffalo, sheep, g oats, horse, pigs and poultry. The estimation of methane was based on the IPCC Tier 1 and Tier 2 met hods. Methane emission from cattle rose by 44% within the period from 45.61-65.57 Gg. Results: Buffalo recorded a drop in methane emission by 54% from 17.12-7.86 Gg while the methane emission from sheep initially rose by 350% in 1992 only to drop by another 56% by 2008. Goats emission only de clined by 17% from 1.79 Gg in 1980-1.49 Gg by 2008. Methane emission from horse has been consiste t a around 0.14 Gg. The decreasing stock of pigs has led to a drop in methane emission from the se s t of animals with most of the emission coming from manure management. Conclusion: The healthy export market for poultry has seen a r ise in methane emission by 274% from 2.18 Gg in 1980-8.17 Gg by 2008. The overall increase in methane emission from all the livestock is 20% from 81.83 G g in 1980-98.76 Gg in 2008. With the aggressive drive of government to boost cattle and goat produc tion, there is the likelihood of an increase in methane emission in the future and mitigation optio ns will have to be applied.


INTRODUCTION
The world is experiencing an unprecedented rise in surface temperature (Ominski and Wittenberg, 2004;Petersen andAmbus, 2006 Kaufmann et al., 2006;Smith et al., 2008;Clark and Huybers, 2009;Domingues et al., 2008;Milne et al., 2009, Trenberth, 2010. This rise is attributed to the increased rate of emission of greenhouse gases into the atmosphere and is said to be caused by the activities of human beings, hence the anthropogenic nature of the problem. Six gases have been identified as constituting the greenhouse gases. Chief among the greenhouse gases being touted as responsible for the rise in global surface temperature are carbon dioxide and methane with trace amounts of other gases (Hansen et al., 2006;. The devastating effects of this temperature rise on human beings and the environment have been extensively reported (Calabro, 2009).
Concerns about the devastating effects of uncontrolled release of hydrocarbons in gaseous forms on ozone depletion and global warming have warranted investigation into animal waste production systems (Dong et al., 2011;Masse et al., 2011). A significant source of atmospheric methane is from animal husbandry (Lascano and Cárdenas, 2010;Nusbaum, 2010). The emission of methane by livestock is part of their natural digestive processes and is produced in the rumen of livestock due to the methanogens found in the reticulo-rumen and large intestine of the livestock (Alemu et al., 2011). The gastrointestinal of all animals generate some microbial activities that lead to the production of gases which are combustible. This microbial activity is very extensive in ruminants (Alemu et al., 2011). Globally, methane emission from ruminants is said to be 15% of global production (Takahashi, 2011).
The current method in animal husbandry is either to increase the productivity of the animal through improved nutrition in order to produce less methane per unit of meat or milk or to alter the rumen fermentation process so as to reduce the volume of methane produced (Iqbal et al., 2008). Despite all these efforts, 15% of global methane emissions come from enteric fermentation by ruminants (Houghton et al., 2001;Takahashi, 2011) gave methane emission breakdown from enteric fermentation as 12% of global, 19% of anthropogenic and 36% of agricultural while Naqvi and Sejian (2011) reported that 18% of greenhouse gas emission comes from animal husbandry.
The contribution of methane emission from ruminants is becoming alarming as EC, (2010) reported that methane emission from livestock was 83% of the greenhouse gases emitted within the agricultural sector. Kebreab et al. (2008) posited that 287 m tonnes of methane is released globally and yearly from anthropogenic sources, of which 50% is from agriculture and enteric fermentation from ruminants is said to be the largest biogenic source USEPA, 2006. Aluwong et al. (2011) gave global anthropogenic methane emission from enteric fermentation and manure management as 35-40% of total emission.
Methane emission from ruminants is affected by feed intake level, digestability of feeds, feed processing and addition of lipids (unsaturated fatty acid) (Enishi, 2007). Other factors include the quality of the diet, level of stress the animals undergo and their genetics (Hegarty et al., 2007) as well as feed efficiency (Zhou et al., 2009). Cattle is said to produce between 250-500 l of methane daily (Johnson and Johnson, 1995) while it is said to lose 2-15% of its ingested energy as eructated methane (Giger-Reverdin and Sauvant, 1998). This loss serves two purposes: lower emission of methane leads to a lowering of greenhouse gas concentration in the atmosphere and increased efficiency in livestock production leads to increased revenue for livestock farmers (Giger-Reverdin and Sauvant, 1998). Cattle and buffaloes contribute about 84% of animal methane that is produced enterically (Johnson and Ward, 1996) because of their huge body sizes, large appetites and their rumens having extensive enteric fermentation.

Livestock practices in Malaysia:
The Malaysian government has initiated strategies that will make agriculture the third machine of economic growth. This effort was highlighted in the ninth Malaysian Plan. To achieve this objective, various forms of support and schemes that will encourage investments have been provided. Some of these attractive incentives provided by government include the setting up of some financial institutions specifically entrusted with the provision of capital facilities for interested investors. These institutions include Bank Pertanian Malaysia (Agrobank Malaysia). The bank is responsible for organising, providing, supervising and coordinating credit facilities for agriculture in Malaysia. Agrobank Malaysia offers financing packages to develop the agricultural, livestock and fishery sectors in Malaysia. Others are Bank Pembangunan dan Infrastruktur and Professional Services Export Fund. The government has also formulated legislations that relate to agriculture and agro-based industries. These legislations are meant to regulate activities in fisheries, livestock and food processing and also include activities like animal farming, animal health, slaughtering, processing and marketing. Through the Department of Veterinary Services, government issues licences and permits that relate to the importation of animals into Malaysia as livestock or pets.
Under the National Meat Policy (ruminant sector), Malaysia aims to increase cows and buffaloes from the present 1.0-1.6 m in 2015. This will increase Malaysia's self-sufficiency in meat products to 40% from the present 25%. The plan also wishes to increase the stock of goats from the present 9-35% by 2015 necessitating an increase of the goat population to 1,500,000 MAHA, 2008. It has also been reported (Boo, 2010) that a unit in the Federal Land Development Authority (FELDA) is going into a joint venture to invest RM688 m on livestock projects in its palm oil estates at Kuala Lumpur, Penang, Johor and Sabah.
Another area of government intervention is the Malaysian Goat Industry Development Programme, a bilateral cooperation with Western Australia, in the areas of marketing, production and support services.
The government has also established the National Boer Breeding Centre (NBBC) which is expected to be the catalyst for the development of the goats in the form of production of quality boer breeders. The aim is to produce 6,000 and 1,200 heads of female and male breeders yearly respectively MAHA, 2008. The East Coast Economic Region (ECER), whose aim is the development of cattle and goat breeding for the states of Kelantan, Pahang, Terengganu and the district of Mersing in Johor MAHA, 2008.
In addition to all these is the proposed use of about 2 m hectare of oil palm plantation for cattle rearing as a means of optimizing land use and to increase breeding stock MAHA, 2008.

Methane emissions estimation from livestock:
Estimation of methane emissions from livestock was based on the multiplication of the heads of the livestock by emission factors provided by IPCC (1997). This estimation is carried out at the Tier 1 and Tier 2 levels. The Tier 1 method uses default emission factors and hence only the livestock population data are required for estimation. It is suitable for most animal species in countries like Malaysia where enhanced characterization data are not available. The Tier 1 method can be applied for the livestock except cattle where Tier 2 is recommended by IPCC (1997). Some default values for emission from enteric fermentation and manure management are summarized in Table 1 ( IPCC, 1997).
Emission data for the livestock was obtained from the Department of Statistics and Department of Veterinary Services of the Ministry of Agriculture and Agro-based Industries. The estimation distinguished between enteric fermentation and manure management. Methane emissions were separately calculated for sub-categories of cattle, buffalo, sheep, goats, horses, pigs and poultry. Since Malaysia currently imports most of the livestock feed concentrate, changes in emission due to change in diet will not be captured in enteric fermentation calculation.
Methane emissions from enteric fermentation is expressed as shown in Eq. 1 (IPCC, 1997): where: EF = Emission factor (kg/head/year): GE = Gross energy intake (MJ/head/day) Y m = Methane conversion factor, percent of gross energy in feed converted to methane = 6.5±1.0% for cattle 55.65 = Energy content of methane (MJ/kg CH 4 ) Methane estimation from manure management is given by Eq. 3: The total methane emission is the sum of the emission from enteric fermentation and manure management for each category of livestock.

RESULTS AND DISCUSSION
Results: Methane emissions from the animals in 1980 and 2008 are provided in Table 2.   (Latif and Mamat, 2002) with the bulk of the balance being imported from India due to competitive pricing. If the objective of the government is realized and cattle production increases there is a very high tendency for the emission of methane to more than double the present level unless serious mitigation measures are adopted.

Emissions from buffalo:
Emissions from buffalo are shown id Fig. 2. There is a sharp reduction (54%) in methane emission from the 1980 level of 17.12-7.86 Gg in 2008 with emission from manure management remaining below 1.5 Gg. This is so because the stock of buffalo has been on the decline since 1980 when the stock was 285,339 whereas the stock by the end of 2008 was 131,000. The total present stock of cattle and buffalo is about 1.0 m and this value is projected to be 1.5 m by 2015 although the focus of government is to increase the stock of cattle to the detriment of the other livestock. This expected increase in stock population will be accompanied by a proportional increase in methane emission.
Emissions from sheep: Emissions from sheep rose by 350% from 0.32 Gg in 1980 and peaked at 1.44 Gg in 1992 and dropped by 56% to the present level of 0.63 Gg in 2008 Fig. 3. The emission from sheep has been consistent for almost a decade now indicating that the stock of sheep has been steady and almost the same for the last few years since 2001. Emission from manure management has been almost non-existent as the highest emission was 0.06 Gg in 1992. Figure 4 shows methane emission from goats and it is not following any pattern. It has shown fluctuating tendencies but has been steady in the last six years starting from 2005. Emission in 1980 was 1.8 Gg and reached its peak a year later at 1.9 Gg. Since then the emission of methane from goats has been swinging up and down with the lowest value of 1.22 Gg recorded in the year 2000. As with sheep, emissions from manure management have been virtually nil with the bulk of emissions coming from enteric fermentation. The lack of any appreciable increase in methane emission from goats might not be unconnected with government policy to focus its attention on increasing the stock of cattle. This apparent stagnation is curious bearing in mind the drive of government to boost the production of goats. Emissions from horses: The emissions of methane from horses are shown in Fig. 5. The emission trend has been consistent except in the last five years (from 2004) when emission has been the same at 0.14 Gg. Emissions from manure management has been consistent all through at 0.01 Gg. The increase in emission noticed in the last few years was as a result of sudden increase in the stock of horses from 4000-4500-7000 since 2004 (a 75% increase), maybe an indication of affluence and a strong economy. Horses are used by the royal families and some affluent personalities in the society. Overall the emission of methane from horses, which has never gone beyond 0.14 Gg, is quite negligible when compared to the other ruminants.

Emissions from goats
Emissions from pigs: Figure 6 shows methane emission from pigs in Malaysia. Enteric methane emission from pigs is not as pronounced as with the other ruminants because they are monogastric. Nonetheless, emissions from pigs rose by 74% to a peak value of 25.6 Gg in 1994 from the 1980 value of 14.7 Gg. The emission then dropped by 42-14.9 Gg in 2008. There was a sharp drop in emission between 1998 and 1999 when the stock level dropped from 2.9 -1.9 m.
Since then emission has been almost steady in the last decade while government is encouraging the rearing of cattle instead of pigs. Being an Islamic country Malaysia has found it extremely difficult and near impossible to stop the consumption of pork which has found favor with the Chinese population.
Emissions from poultry: Figure 7 shows methane emission from poultry. This is the fastest growing of all as the stock of poultry rose from 51 m in 1980 to the present value of 190 m, an increase of 274%. Hence emission also rose from 2.18 Gg in 1980 to the present 8.17 Gg in 2008. There are indications that this will still continue to rise in the future. Both enteric fermentation and manure management have almost equal contribution to the emission. Because of the exportdriven and thriving poultry industry, there is all possibility that this increasing trend will continue.
Overall emission: When all the emissions are summed up the overall emissions are shown in Fig. 8. Emission from manure management peaked at 45 Gg in 1994 whereas the highest emission from enteric fermentation was 60 Gg in 2004. The overall picture that is emerging is that emission from livestock is hovering around 100 Gg. This value will rise when all the efforts of the Malaysian government to increase livestock production begin to yield dividend.

Mitigation options:
Enteric methane emissions are said to be more amenable to mitigation (Aluwong et al., 2011). Methane reduction strategies have been grouped into three which are management (DeRamus et al., 2003), nutritional (Lovett et al., 2005) and advanced biotechnology . There have been many reported cases of methane emission reductions after modification of the dietary feed (Beauchemin et al., 2008;Martin et al., 2009;Shibata and Terada, 2010) while alteration of the fermentation process of the rumen is another option (Christopherson et al., 2008;Iqbal et al., 2008). Land use change is another effective way of emission reduction (Vellinga and Hoving, 2011). The proposed integrated use of palm oil mill plantation to rear cattle, improved cropland and grazing land management and selection of grasses with high concentration of water-soluble carbohydrates, forage legume with secondary metabolites like tannins (Lascano and Cardenes, 2010) will reduce methane emissions. High digestability of pasture for grazing is another option to consider (Hart et al., 2009).

CONCLUSION
The emission of methane from livestock has stabilized in the past few years. This is expected to rise with the aggressive nature of government intervention in the agricultural sector with the special emphasis on expansion of cattle and goat population. To stem this expected increase in methane emission requires the formulation and adaptation of appropriate mitigation measures. The aim of the government to make agriculture the third machine of economic growth, as enshrined in the ninth development plan, points to a massive increase in livestock population and an increasing threat to the environment due to the potential increase in methane emission. This calls for further investigation of the factors affecting enteric fermentation and manure management.