India is a country rich in geographical diversity, having all kinds of weather and surplus in huge variety of flora and fauna out of which livestock plays a vital role in India’s economy. India being world’s second largest populated country has to face a continuous pressure of job production so people can earn their livelihood, here agriculture and allied sector contributes the most i.e. more than 70 percent population of India earn their livelihood from agricultural and animal husbandry sector. Livestock sector comes as a boon for people who have small land holdings or even no land therefore marginal and small farmers as well as landless labourers hold 70 per cent of the total livestock population as the absorption capacity of other economic sectors is are low in rural areas.
Livestock forms the livelihood of two thirds of the rural population. It also provides employment for about 18.8% of the Indian population. India has huge livestock. The livestock sector contributes 4.11% of GDP and 25.6% of total agricultural GDP. But along with all the advantages livestock rearing creates a great amount of threat to environment, livestock rearing produces methane and nitrous oxide are the two main gases which are a major threat form the environment and comes under greenhouse gases. The livestock sector contributes directly / indirectly to GHG emissions, inclusive of via animal physiology, manure storage, manure treatment, soil application, chemical fertilizers and more.
The main greenhouse gas emissions from livestock are CO2, CH4 and N2O. CH4 is the largest contributor to anthropogenic greenhouse gas emissions at 44%, followed by N2O (29%) and CO2 (27%) has a global warming effect 28 times greater than carbon dioxide. Nitrous oxide, which is produced during manure storage and the use of organic/inorganic fertilizers, is a molecule with a global warming potential 265 times greater than carbon dioxide. Apart from greenhouse gases produced directly from livestock, crop production for livestock rearing also intensify the production of greenhouse gases on a larger extent.
45% of greenhouse gases produced in livestock rearing comes from feed production and its processing, enteric fermentation 39% of GHG which stands as the second largest source of emissions. Manure storage accounts about 10% of the total GHG from livestock rearing and remaining 6% is contributed by the processing and transportation of animal products. Apart from this livestock contribute also 80% of all agricultural non-CO2 emissions which makes them responsible for about 12% of all anthropogenic greenhouse gas (GHG) emissions.
Causes of increase in GHG through livestock rearing:
- Enteric fermentation by livestock: Enteric fermentation is a natural part of the digestive process of ruminants where bacteria, protozoa, and fungi contain in the fore-stomach of the animal (rumen), ferment and break down the plant biomass eaten by the animal. Livestock farming contribute to 44% of the global anthropogenic CH4 emissions via their normal digestive processes (enteric fermentation) and manure management and in animal production sector, as much as 95–97 % of CH4 comes from ruminants. During the digestion process of animals, enteric fermentation transforms eaten food into digestible feed. A methane by-product through exhalation is released by enteric. Feed composition and feed consumption can vary enteric fermentation and therefore methane emissions.
- Feeding high concentrate diet to animals can lead to less methane production compared to the dry feed or roughage. Unfortunately, India is the leading methane producing country in livestock rearing system along with China, Brazil, and the United States. India’s leading position in methane emission could be due the its vast livestock population. Small ruminants, buffaloes, pig and poultry contribute about 7 to 10%. If the GHG emissions are estimated on the basis of commodities, beef cattle are the main sources of emissions in the sector with 41%, followed by dairy cattle (20%), pigs (9%), buffalo (8%), poultry (8%) and small ruminants (6%).
3. Nitrous oxide is generated through both the nitrification and denitrification processes of the nitrogen contained in manure, which is mainly present in organic form (e.g., proteins) and in inorganic form as ammonium and ammonia. It is estimated that 1.7 million tonnes of manure soil N2O are released per year. N2O emissions from applied manure are 40% higher in mixed crop-livestock systems than the N2O emissions from excreted manure deposited on pasture systems. Industrial production systems have 90% less N2O emissions than mixed crop-livestock systems. Indirect N2O emissions from livestock production include emissions from fertilizer use for feed production, emissions from leguminous feed crops, and emissions from aquatic sources following fertilizer application. Due to primarily anaerobic conditions of rice production globally, CH4 production indirectly associated with animal manure application to irrigated rice fields is considered a significant source of emissions.
Feed production for livestock consumption: Almost 60% of the global biomass harvested worldwide enters the livestock subsystem as feed or bedding material. Livestock sector contributes markedly to greenhouse gas emissions through the production of nitrogen fertilizers used to grow crops as fodder for livestock. Greenhouse gas emissions from feed production represent 60–80% of the emission coming from eggs, chicken and pork, and 35–45% of the milk and beef sector. Livestock feed consumes nearly 43 % of the food energy (kilocalories) produced by the world’s total harvest of edible crops after postharvest losses. Considering the number of fertilizers used, packaging, transport and application in the animal husbandry sector, the manufacturing process of fertilizers contributes more than 40 million tonnes of CO2 annually.
As growth in fertilizer and manure use continues, a 35–60% increase of N2O emissions (0.9 to 1.1 million tonnes per year of total N2O-N emissions) is expected by 2030. Even the meat industry is a big contributor in this feed production associated GHG pollution, to produce 1 kg of edible meat by typical industrial methods requires 20 kg of feed for beef, 7.3 kg of feed for pig meat, and 4.5 kg of feed for chicken meat. Apart from the above-mentioned livestock related causes of environmental pollution there are other causes which also create load on the environment, like processing and transportation of animals and their products, land use change for livestock raring which causes deforestation and even soil erosion, on-farm fossil fuel usage, release of CO2 due to cultivation of soil etc.
Mitigation strategies to reduce greenhouse gases created due to livestock production:
There is no single magic process for reducing the livestock associated pollution, multiple preventive measures need to be applied in single flow to reduce the cause. Mitigation may occur directly by reducing the amount of greenhouse gases emitted, or indirectly through the improvement of production efficiency. Decreasing methane emissions from ruminants is one pressing challenge facing the ruminant production sector, Forage quality and digestibility affect enteric methane production. Lignin content increases during plant growth, consequently reducing plant digestibility. Therefore, harvesting forage (especially grass) for ensiling at an earlier stage of maturity increases its soluble carbohydrate content and reduces lignification. Improving feed digestibility by increasing concentrate is another effective mitigation strategy, reducing methane emissions by 15% per unit of milk adjusted to fat and protein.
A one percent increase of dietary fat can decrease enteric methane emissions between 4 to 5%, therefore addition of fats or fatty acids to the diets of ruminants can decrease enteric methane emissions by both decreasing percentage of energy supplied by fermentable carbohydrates; and changes in rumen microbial population. Feed additives (electron receptors, ionophore antibiotics, chemical inhibitors, etc.) have also been tested for their ability to decrease methane emission, increase weight gain and reduce feed intake per metric ton of meat produced by using feed additives can reduce enteric fermentation GHG production from manure of livestock is associated with its storage in aerobic environment for long time, therefore if we reduce the time of manure storage and instead of using aerobic method of storage and shift to anaerobic storage technique like lagoons and tanks the produced methane can be converted into methane. Removing bedding from manure by using a solids separator is a way to reduce the quantity of waste.
By removing the solids from manure streams methane emissions are reduced, the time between storage systems cleaning is increased, and crust formation is prevented. Even change in diet of animals can reduce the amount of nitrogen in the faeces, if protein intake is reduced, the nitrogen excreted by animals can also be reduced. Supplements such as tannins are also known to have the potential to reduce emission. To avoid greenhouse gases emission in feed production timing, quantity, and method of fertilizer application is very important factor that influence the soil nitrous oxide emissions. The nitrogen fertilizer applied is susceptible to loss by leaching and de-nitrification before crop uptake. Therefore, ensuring that appropriate amounts of nitrogen get to the growing crop and avoiding application in wet seasons or before major rainfall events. Using organic fertilizers, regular soil testing, using technologically advanced fertilizers, and combining legumes with grasses in pasture areas may decrease GHG emissions in feed production. Intensive rotational grazing systems are being promoted as a good way to increase forage production and reduce nitrous oxide emissions.
Conclusion
Methane emission contribution from Indian livestock is the largest as compared to several other subsectors from agriculture, viz. rice cultivation and open burning of crop leftovers. The biggest biogenic sources of CH4 are enteric fermentation from ruminant animals and rice production. Animal production-related greenhouse gas emissions from the agricultural sector include CH4 emissions from domestic animals, CH4 and N2O emissions from manure and grazed areas, and N2O emissions from soils. In India, there is an urgent need to lower livestock-related GHG emissions. Methane emissions are influenced by animal feed composition and the ratio of various feeds, including soluble residue, hemicellulose, and cellulose content. Reduced feed input per unit of output strategies are the most efficient means of reducing methane emissions from livestock. Application of fermented manures like biogas slurry in the place of unfermented farmyard manure can help in reducing GHG emissions. Balanced agricultural methods are necessary to be adopted for limiting greenhouse gas emissions at acceptable level.
Varsha Vihan*1, Chirag Singh1, Ahmad Fahim2, Anuj Kumar3 and Rohit Kumar4
1Ph.D. Research Scholar, Department of Livestock Product Technology, 2Assistant Professor, Department of Livestock Production Management, 3Ph.D. Research Scholar, Department of Livestock Production Management, 4Ph.D. Research Scholar, Department of Animal Nutrition, College of Veterinary and Animal Sciences, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, 250 110, India
Corresponding author:
Email- *varshavihan16495@gmail.com
