There is perhaps no other greenhouse gas as prolific as CO2, which is produced by a myriad of anthropogenic sources, from large scale burning of fossil fuels to something as simple as breathing. For us, we shall be briefly discussing the role of agriculture in CO2 emissions.
Food systems from production to consumption, contribute 19%–29% of global anthropogenic greenhouse gas (GHG) emissions. Within that, agricultural production, including indirect emissions such as emissions associated with land-cover change, accounts for 80%–86% of total food system emissions. It is important to note that the 80%–86% figure from Vermeulen et al., (2012) is for all forms of agriculture, both animal and plants and all forms GHG emissions represented in terms of CO2 equivalents.
Interestingly, while GHG emissions are measured in metric tonnes of CO2 equivalents, the net flux of CO2 alone in agricultural soils is small, because agricultural soils may variably act as a sink or source and growing plants may also act as a sink for atmospheric carbon as plants utilise CO2 for photosynthesis. In the UK, agricultural production of CO2 through fossil fuel combustion and lime use accounts for less than 1% of the total released into the atmosphere each year which may mistakenly give the impression that direct emissions of CO2 by agriculture is insignificant. However, there is more carbon in the world’s soils than in plant biomass and the atmosphere put together (Merrington et al., 2005). Paustian et al., (1997) estimates that agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity, with global estimates of this sink capacity in the order of around 20-30 Petagrams of carbon over the next 50-100 years. To give you an idea of how much 1 petagram is, it’s equal to 1*10^12 kilograms.
However, this is not to say that agriculture does not contribute to CO2 emissions, the indirect emissions associated with growing these crops, such as clearing land, fertiliser production etc. are significant contributors. In 2005, agriculture covered 37% of the earth’s land area. and-cover change is a major contributor of CO2, with approximately 80% of this new land for crops and pastures derived from replacing forests, especially within the tropics. Additionally, there are other sources of CO2 emissions associated with agriculture post-production emissions from processing, packaging, refrigeration of agricultural products.
Sources:
- https://www.nature.com/news/one-third-of-our-greenhouse-gas-emissions-come-from-agriculture-1.11708 (One-third of our greenhouse gas emissions come from agriculture)
- Vermeulen, S. J., Campbell, B. M., & Ingram, J. S. I. (2012). Climate change and food systems. Annual Review of Environment and Resources, 37, 195–222. https://doi.org/10.1146/annurev-environ-020411-130608
- Paustian, K., Andren, O., Janzen, H. H., Lal, R., Smith, P., Tian, G., Tiessen, H., Van Noordwijk, M. and Woomer, P. L. 1997. Agricultural soils as a sink to mitigate CO2 emissions. Soil Use and Management. 13 (4), pp. 230-244. https://doi.org/10.1111/j.1475-2743.1997.tb00594.x
- https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions
- Merrington, G., Winder, L., Parkinson, R., & Redman, M. (2005). Agricultural Pollution Environmental: Environmental problems and practical solutions. Spon Press.