Methane from herbivores: Impact on modern and ancient climate change.
Dr Fiona Gill (SEE), Prof Martyn Chipperfield (SEE), Dr Daniel Hill (SEE)Project partner(s): Professor Marcus Clauss (University of Zurich), Professor Juergen Hummel (Georg-August University, Goettingen)Contact email: firstname.lastname@example.org
Methane is the second most important anthropogenic greenhouse gas and as such makes a major contribution to climate change. It has been increasing in the atmosphere for the past 5000 years, but the reasons for both past increases (Ruddiman, 2003) and recent increases (Nisbet et al., 2014) are not fully understood. In addition, predictions of future atmospheric methane levels require an accurate knowledge of all sources.
Figure 1. Global methane cycle (from Encyclopaedia Britannica).
Herbivorous animals, particularly ruminants and other foregut fermenters, make a significant contribution to global methane emissions (Figure 1), but estimates of this contribution are poorly constrained for the present (Ciais et al., 2013) and the archaeological past ( Fuller et al., 2011). Existing methods can be used to measure the amount of methane produced by domesticated ruminants such as cows and sheep. However, these methods cannot be readily applied to wild animal populations, for animal welfare and logistical reasons.
Archaeol is a lipid produced by archaea including the methane-producing methanogens, such as those found in the digestive tract of herbivores. Previous studies have shown that archaeol is present in the faeces of foregut-fermenting herbivores (Gill et al., 2010) and that for cows on contrasting diets, the concentration of archaeol in the faeces co-varies with the amount of methane produced (Figure 2, Gill et al., 2011; McCartney et al., 2013; Schwarm et al., 2015). However, details of the quantitative relationship between archaeol and methane production are currently poorly understood (e.g. McCartney et al., 2014). This project seeks to address this knowledge gap by quantifying archaeol and measuring methane in several key suites of samples. This will improve understanding of the controls on faecal archaeol concentration, allowing a quantitative proxy for methane emissions in herbivores to be developed. Such a proxy could be used to generate methane estimates to be incorporated into existing atmospheric models of methane sources. This project will also produce new estimates of the impact of livestock on prehistoric methane levels, through the use of the global climate models with changes in atmospheric methane levels across the last 5000 years.
Figure 2, modified from Gill et al. (2011), showing that faecal archaeol and methane emissions co-vary for cattle on contrasting diets.
In this project, you will work with leading scientists at the University of Leeds and elsewhere to:
1. Carry out in vitro fermentation experiments on a range of herbivore feeds and quantify the methane and archaeol produced.
2. Quantify archaeol in samples from the digestive tract of goats, cattle, llamas, horses and rabbits and compare with PCR data on methanogens where available.
3. Quantify archaeol from an extensive range of herbivore faecal samples, spanning multiple taxa and digestion types, and compare with methane emission data where available.
4. Integrate results to develop a faecal lipid proxy for methane emissions.
5. Test the proxy at a local (University of Leeds farm) and regional scale.
6. Simulate the dispersion of methane from herbivores in the atmosphere using numerical models, and compare the simulations with recent in-situ CH4 observations.
7. Assess the role of herbivore CH4 emissions in present-day climate change and test its potential role in climate changes of the past 5000 years.
Potential for high impact outcome
This interdisciplinary project brings together scientists with a wide range of expertise to address the issue of quantifying herbivore methane emissions. Results will contribute to global greenhouse gas inventories and provide novel insights into the carbon budget, to aid understanding of past and present climate change and future changes. This project has the potential generate several publications and given the topic, at least one is likely to be suitable for submission to a high impact journal.
The student will work under the supervision of Dr Fiona Gill within the Earth Surface Science Institute and Professor Martyn Chipperfield and Dr Daniel Hill within the Institute of Climate and Atmospheric Science in SEE. The project provides training in:
(i) Organic geochemistry – extraction of archaeol and other lipids from faeces and fermented feed samples and analysis by gas chromatography-mass spectrometry (SEE).
(ii) Dissections of the digestive tract of cattle, llamas, rabbits and horses. To be carried out under the supervision of Prof. Marcus Clauss at the University of Zurich, Switzerland.
(iii) In vitro fermentation experiments and quantification of methane using gas chromatography. To be carried out under the supervision of Prof. Jürgen Hummel, Georg-August University, Göttingen, Germany.
(iv) Development and use of atmospheric models. Existing 3-D models, available within ICAS, will be used to simulate the dispersion of methane emissions in the atmosphere. Comparison of the models with recent ground and aircraft borne CH4 observations will be use to evaluate the new estimates of emissions from herbivores.
(v) The use of global climate models and the simulation of climate change over the last 5000 years under alternative greenhouse gas forcing scenarios. These simulations will be run on high performance computing at the University of Leeds, under the supervision of Dr. Daniel Hill. They will give the student hands on experience of the use of computer models and in the processing and analysis of large data sets.
The successful PhD student will be a member of both the Cohen Geochemistry research group and the Atmospheric Chemistry research group and will receive excellent hands-on training in both experimental techniques and computer modelling. The student will also have access to a wide range of training courses for both project specific and general skills (http://www.emeskillstraining.leeds.ac.uk/).
Applicants should have a background in a relevant subject, such as biology, chemistry, Earth or environmental science, with an interest in global environmental problems.
Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, R. DeFries, J. Galloway, M. Heimann, C. Jones, C. Le Quéré, R.B. Myneni, S. Piao and P. Thornton, 2013: Carbon and Other Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter06_FINAL.pdf
Fuller, D.Q., van Etten, J., Manning, K., Castillo, C., Kingwell-Banham, E., Weisskopf, A., Qin, L., Sato, Y-I. and Hijmans, R.J. (2011) The contribution of rice agriculture and livestock pastoralism to prehistoric methane levels: An archaeological assessment. doi: 10.1177/0959683611398052
Gill, F.L., Dewhurst, R.J., Dungait, J.A.J. Evershed, R.P., Ives, L., Li, C.S,; Pancost, R.D., Sullivan, M., Bera, S., Bull, I.D. (2010) Archaeol - a biomarker for foregut fermentation in modern and ancient herbivorous mammals?, Organic Geochemistry, 41, pp.467-472. DOI: 10.1016/j.orggeochem.2010.02.001
Gill, F.L., Dewhurst, R.J., Evershed, R.P., McGeough, E.; O'Kiely, P.; Pancost, R.D.; Bull, I.D. (2011) Analysis of archaeal ether lipids in bovine faeces, Animal Feed Science and Technology, 166-67, pp.87-92. http://dx.doi.org/10.1016/j.anifeedsci.2011.04.006
McCartney, C.A., Bull, I.D., Yan, T., Dewhurs,t R.J. (2013) Assessment of archaeol as a molecular proxy for methane production in cattle. Journal of Dairy Science 96 1211-1217 http://dx.doi.org/10.3168/jds.2012-6042
McCartney, C.A., Bul,l I.D., Dewhurst, R.J. (2014) Using archaeol to investigate the location of methanogens in the ruminant digestive tract. Livestock Science 164:39-45, http://dx.doi.org/10.1016/j.livsci.2014.02.020
Ruddiman, W.F., 2003. The anthropogenic greenhouse era began thousands of years ago. Climatic Change, 61, 261-293. doi 10.1023/B:CLIM.0000004577.17928.fa
Schwarm, A., Schweigel-Röntgen, M., Kreuzer, M., Ortmann, S., Gill, F., Kuhla, B., Meyer, U., Lohölter, M., Derno, M. (2015) Methane emission, digestive characteristics and faecal archaeol in heifers fed diets based on silage from brown midrib maize as compared to conventional maize. Archives of Animal Nutrition 69:159-176, doi: 10.1080/1745039X.2015.1043211
Related undergraduate subjects:
- Earth science
- Environmental science