Methane is one of the greenhouse gases that has a much higher effect on global warming than CO2. 1 tonne of methane is equivalent to 28 to 36 tonnes of CO2. Agriculture is considered the largest methane emitter among all anthropogenic sources. Other sources of methane emissions are depicted below -
80% of methane emissions from agriculture comes from livestock. Methane is produced by enteric fermentation in livestock that involves the digestion of carbohydrates with archaebacteria. There is so much methane production during fermentation it passes into ruminant's blood and comes out in the form of multiple burps. There are various strategies proven by research to reduce methane emissions in livestock mainly focusing on feed management, manure management, and animal management. Some of the strategies mentioned in this article are sustainable and also cost-effective.
Improving digestibility of feed
11. Forage quality - If the animal consumes more matured plants, it will emit more methane during enteric fermentation than less matured plants. The main reason behind this is lignin content, more lignin makes the forage less digestible as less soluble carbohydrates are difficult to digest. Feeding animal grasses at an early stage of maturity reduces methane emission by 5% per unit of fat protein-corrected milk. ( what is fat protein-corrected milk?)
2. Physical processing - Physical processing of feed using shear forces or grain size reduction makes it easier to digest. It reduces methane emission by up to 2% per unit of fat protein-corrected milk.
3. Concentrate feeding - With rates of 35-40% concentrate inclusion in feed can reduce methane emission by up to 15% per unit of fat protein-corrected milk.
Reduction of carbohydrates
Methanogens mainly feed on carbohydrates in feed, replacement of carbohydrates with lipids can reduce methanogen action in the gut and hence further reduce methane emission. Only 5-8% of lipids can be included replacing carbohydrates in the diet as more amount can lead to impairment of digestion of fiber because of changed microbial population. 5-8% replaced lipids can potentially reduce 15% per unit of fat protein-corrected milk.
Seaweeds
The introduction of seaweeds in cows' diets can reduce methane emissions by up to 12%. In one study on red seaweed, the introduction of 0.5% (dry matter of feed) of Chondrus crispus in feed has resulted in reduced methane emission of up to 12%.2 Research from the University of Pennsylvania has shown promising results with red algae in reducing cattle methane emissions. In the study, Asparagopsis taxiformis reduced methane up to 55% in cows by reducing Methanosphaera - a microbe that uses hydrogen to reduce methanol to methane, in the rumen 3
Secondary metabolites or bioactive compounds
Secondary metabolites from plants such as tannins, essential oils, and saponins have shown lower methane emission in livestock animals. These compounds are also readily available and are safe for animal consumption. 4
Manure handling
1. Manure storage - Storing manure at low temperatures can reduce methane emissions by 30-50%. However, maintaining that low temperature costs extra and is not environmentally friendly.
2. Anaerobic digestion - Making biogas out of manure or animal waste has been a clever invention and is still considered one of the efficient processes to reduce methane emissions.
3. Impermeable covers - In this model, manure is covered with an impermeable cover made of plastic or similar material that can trap released gases like methane which can be used later on as biogas. 5
Management of animals
1. Breeding to improve fertility - Breeding of animals, especially cows, can help maintain herd size without too much replacement of animals which causes an increase in methane emissions. Although an increase in reproductivity increases nutrition requirements and also extreme stress can cause metabolic disorders
2. Maintaining proper hygiene - Hygienic conditions enhance the chances of healthy animals which in turn emits lesser methane than animals fighting with infection.
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