Taking a look at the creation of greenhouse gasses

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Cows in a field.
The owners of Misty Valley Farm, in Carrollton, Ohio, milk 43 cows and sell the milk to Horizon Organic. (Sarah Donaldson photo)

It’s that time of the year during family gatherings and the consumption of a lot of food when everyone in the room is trying to avoid the stench that just overpowered the space. The smell becomes so strong that some individuals try to gently move to other areas of the house in hope of finding more appealing inhalable air. 

Then, one of the most outspoken family members, unless it was caused by them, says, “OK, who passed the gas?” Everyone stops and looks at each other and the guilty one tries to fake the shame of the call out. 

This is somewhat how those of us connected with agriculture feel at times from accusations of large contributions to greenhouse gas production. GHG and climate change are constantly before us in the news, political agendas and environmental sustainability discussions. The three primary GHG are carbon dioxide, methane (CH4), and nitrous dioxide. 

It has been estimated that agriculture contributes about 10% to the total GHG production in the U.S. 

Based on life cycle assessment, reduction in CH4 production from enteric fermentation and manure provides the greatest opportunity for reducing GHG production from the dairy industry. 

In the December 2022 issue of the Journal of Dairy Science, Karen Beauchemin from Agriculture and Agri-Food Canada, Lethbridge, Alberta, and co-authors published an article on the “Current Enteric Methane Mitigation Options” for ruminant livestock. 

In the article, the following options were discussed:

1. Increased animal productivity: Increased output per unit of input can lead to reduced CH4 per unit of product. This efficiency has been achieved through improved feeding practices, animal management, improved animal health and comfort, genetic advancement and better reproductive performance. 

2. Selection of low-methane-producing animals: Individual differences in CH4 production exist among animals within the same herd and with the same feeding management, but heritabilities of CH4 production are low to moderate in dairy cattle. The use of this strategy to lower CH4 production is challenging because of the difficulty in measuring methane production or developing practical proxies for prediction of CH4 production and the possible existence of undesirable associations between CH4 production and animal productivity. 

3. Diet reformulation: a) It is well established that levels, source and processing of feeds can affect CH4 production by changes in rate of feed passage from the rumen, digestibility and impact microbial populations; however, the result is not always positive, especially when viewed in context of a LCA. b) Dietary lipid supplementation has been shown to decrease CH4 production by the replacement of starch and with direct impacts on the microbial population. However, the impact on CH4 and the animal’s performance varies with level and source of fat supplementation. 

4. Forage system: Forage production systems are highly variable and dependent upon farm site conditions (e.g., soil type and fertility, water and climate) and management practices. Factors focused on in the article included digestibility; use of perennial legumes, high-starch (e.g. corn or small grain) forages or high-sugar grasses; pasture management, and forage preservation and processing. These factors may affect forage yield and nutritive value, carbon storage in soils, animal performance, manure excretion and ultimately, GHG emissions. 

Therefore, in all cases, a change in forage management to decrease enteric CH4 emissions needs to be assessed using regionally specific farm-level LCA that account for changes in forage and animal productivity, as well as emissions and sinks from all components of the farming system, including soil carbon. 

5. Action on the ruminal fermentation: Research with various additives have revealed some promise of reducing CH4 production or intensity, including ionophores, 3-nitrooxypropanol, macroalgae (seaweeds), alternative electron acceptors (e.g. fumarate, malate and nitrate), essential oils, tannins and saponins, and direct-fed microbials. 

Research continues on various approaches for reducing CH4 production, capturing CH4 on the farm and effectively utilizing the captured CH4. Mitigation strategies for CH4 production yet in early developmental stages include immunization against methanogens, early-life interventions to modify the microbiota in a manner that decreases CH4 emissions later in life, feeding enzymes with activity against methanogen cell walls, elimination of ruminal protozoa, and using a device that attaches to animals to collect CH4 and oxidize it. 

All of the aspects discussed in this article have potential interest to farmers as they strive to reduce the carbon footprint of dairy production and gain financially from carbon credits.

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