Food Production: [Livestock] Climate Change

Building on the previous overview of food production and how it causes pollution, today, we would like to specifically focus on livestock production in this post!

As mentioned, livestock production increases greenhouse gases (GHG) emissions and causes environmental degradation. With the rising global population and changing food preferences across the globe, there is a greater need to meet meat consumption’s rising demands (UN, 2017). Hence, livestock production has undergone evident expansion. Also, increasing competition for resources resulted in the concentration of livestock production near residential areas (Smit & Heederik, 2017). As such, these changes resulted in more significant impacts on our natural environment and even our health.

How does livestock production cause air pollution?

The expansion of livestock production activities contributes heavily to air pollution, either directly or indirectly, by releasing GHG such as methane (CH4) or nitrous oxides (N2O) into the atmosphere. Direct sources of emissions could include enteric fermentation and manure management, while indirect sources of emissions include land-use changes, livestock-induced desertification. (Sejian et al., 2016).

Fig. 1 Agriculture emissions by sub-sector, 2001-2011, FAO Statistics Division (2014)

The major contributors to GHG emissions are enteric fermentation and manure management.

Enteric fermentation accounts for about 40% of overall agricultural GHG emissions (Fig. 1). It is a digestive process whereby microbes in cattle’s stomach break down plant materials into nutrients and release gaseous CH4 and CO2 as waste products by ‘burping’ (Grossi, Goglio, Vitali & Williams, 2019). This process serves as a main source of energy for these animals while also contributing heavily to GHG emissions.

Fig. 2 Cow Manure. Obtained from: https://extension.psu.edu/should-i-use-my-beef-manure-as-fertilizer

Another direct emission source is manure management, responsible for about 7% of agricultural GHG emissions (Fig. 1). Manure, easier known as animal dung, emits both CH4 and N2O (Fig. 2). Under anaerobic (without oxygen) conditions, organic matters undergo decomposition by bacteria, producing CH4 and CO2. This process is further facilitated when liquid manure is being stored or treated in lagoons or tanks that often promote anaerobic conditions, speeding up CH4 production (Grossi, Goglio, Vitali & Williams, 2019). Nitrous oxide is also generated through the nitrification and denitrification of nitrogen in manure, which requires aerobic and anaerobic conditions. This collaborative process of nitrification converts ammonia to nitrates, and denitrification converts nitrates to N2O, leading to an increase in N2O production (IPCC, 2001).

Impacts on climate change

Fig. 3 Global Warming Potential (GWP) values. Obtained from: https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf

According to Sejian et al. (2016), we see that global livestock production accounts for about 18% of global GHG emissions. 18% may not seem like the most striking number. However, the release of potent GHG such as CH4 and N2O is particularly of concern given their more considerable global warming potential (GWP) values than that of carbon dioxide (CO2). GWP is a metric used to measure and compare the ability of each GHG to trap heat in the atmosphere relative to other gases (IPCC, 1990). With GWP values of CO2, CH4, and N2O at 1, 28, and 265 respectively (Fig. 3), CH4 and N2O are no doubt of more significant concern given their higher potency to retain heat in the atmosphere and exacerbate global warming (IPCC, 1990).

In the next post, we will find out more about the health implications of livestock-induced air pollution!

With that, I will end today’s post here!

Detective Out,

Linying

References

FAO Statistics Division. (2014, Mar). Agriculture, forestry and other land use emissions by sources and removals by sinks. FAO. Retrieved from http://www.fao.org/3/i3671e/i3671e.pdf

Grossi, Goglio, Vitali & Williams. (2019, Jan). Livestock and climate change: impact of livestock on climate and mitigation strategies. Animal Frontiers, 9(1), 69-76. Retrieved from https://academic.oup.com/af/article/9/1/69/5173494

IPCC. (1990). Climate Change 1990: The Intergovernmental Panel on Climate Change Scientific Assessment. Cambridge, UK: Cambridge University Press. Retrieved from https://www.ipcc.ch/site/assets/uploads/2018/03/ipcc_far_wg_I_full_report.pdf

IPCC. (2001). Good practice guidance and uncertainty management in national greenhouse gas inventories. IPCC. Retrieved from https://www.ipccnggip.iges.or.jp/public/gp/bgp/4_2_CH4_and_N2O_Livestock_Manure.pdf

Sejian et al. (2016, Mar 30). Livestock as sources of greenhouse gases and its significance to climate change. IntechOpen. Retrieved from https://www.intechopen.com/books/greenhouse-gases/livestock-as-sources-of-greenhouse-gases-and-its-significance-to-climate-change

Smit, L. A. M. & Heederik, D. (2017, Sep 27). Impacts of intensive livestock production on human health in densely populated regions. Geohealth, 1(7), 272-277. Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GH000103

UN. (2017). World population prospects: key findings and advanced tables. United Nations. Retrieved from https://population.un.org/wpp/publications/files/wpp2017_keyfindings.pdf