DOI QR코드

DOI QR Code

Measurement of Methane Production from Ruminants

  • Bhatta, Raghavendra (National Institute of Animal Nutrition and Physiology) ;
  • Enishi, Osamu (National Institute of Livestock and Grassland Science) ;
  • Kurihara, Mitsunori (National Institute of Livestock and Grassland Science)
  • 발행 : 2007.08.01

초록

On a global scale agriculture and in particular enteric fermentation in ruminants is reported to produce about one fourth (21 to 25%) of the total anthropogenic emissions of methane ($CH_4$). Methane is produced during the anaerobic fermentation of hydrolyzed dietary carbohydrates in the rumen and represents an energy loss to the host besides contributing to emissions of greenhouse gases into the environment. However, there appears to be uncertainty in the $CH_4$ estimation from livestock due to the limited availability of data to document the variability at the farm level and also due to the significant impact of diet on the enteric $CH_4$ production. The methane mitigation strategies require robust prediction of emissions from rumen. There are many methods available which would be suitable for measuring $CH_4$ produced from the various stages of animal production. However, several factors need to be considered in order to select the most appropriate technique like the cost, level of accuracy required and the scale and design of the experiments to be undertaken. Selection of any technique depends on the accuracy as each one has its advantages and disadvantages. Screening of mitigation strategies may be evaluated using individual animal before large-scale trials on groups of animals are carried out. In this review various methods for the estimation of methane production from ruminants as well as for the determination of methane production potential of ruminant feeds are discussed. The advantages and disadvantages of the methods starting from respiration chamber, ventilated hood, facemask, sulphur hexafluoride ($SF_6$) tracer technique, prediction equations and meteorological methods to in vitro methods are detailed.

키워드

Methane;Measurement Technique;Ruminant

참고문헌

  1. Murray, P. J., A. Moss, D. R. Lockyer and S. C. Jarvis. 1999. A comparison of system for measuring methane emissions from sheep. J. Agric. Sci. Cambridge. 133:439-444. https://doi.org/10.1017/S0021859699007182
  2. Pinares-Pantino, C. S., M. J. Ulyatt, K. R. Lassey, T. N. Barry, C. W. Holmes and D. E. Johnson. 2003a. Methane emission by alpaca and sheep fed on lucerne hay or grazed on pastures of perennial ryegrass/white clover or birdsfoot trefoil. J. Agric. Sci. Cambridge. 140:215-226. https://doi.org/10.1017/S002185960300306X
  3. Pinares-Patino, C. S., M. J. Ulyatt, K. R. Lassey, T. N. Barry and C. W. Holmes. 2003. Persistence of differences between sheep in methane emission under generous grazing conditions. J. Agric. Sci. Cambridge. 140:227-233. https://doi.org/10.1017/S0021859603003071
  4. Pinares-Patino, C. 2000. Rumen function and digestion parameters associated with differences between sheep in methane emissions when fed chaffed lucerne hay. J. Agric. Sci. Cambridge. 140:205-214.
  5. Beswick, K. M., T. W. Simpson, D. Fowler, T. W. Choularton, M. W. Gallagher, K. J. Hargreaves, M. A. Sutton and A. Kaye. 1998. Methane emissions on large scales. Atmos. Environ. 32 (19):3283-3291. https://doi.org/10.1016/S1352-2310(98)00080-6
  6. Benchaar, C., J. Rivest, C. Pomar and J. Chiquette. 1998. Prediction of methane production from dairy cows using existing mechanistic models and regression equations. J. Anim. Sci. 76: 671-672.
  7. Beck-Friis, B., U. Sonesson, M. Pell, H. Jonsson and H. Kirchmann. 2000. Formation and emission of $N_2O$ and $CH_4$ from small and large compost heaps of organic household waste. Environ. Monitor. Assess. 62:317-331. https://doi.org/10.1023/A:1006245227491
  8. Bhatta, R., K. Tajima and M. Kurihara. 2006a. Influence of temperature and pH on fermentation pattern and methane production in the rumen simulating fermenter (RUSITEC). Asian-Aust. J. Anim. Sci. 19(3):376-380. https://doi.org/10.5713/ajas.2006.376
  9. Beuvink, J. M. W., S. F. Spoelstra and R. J. Hogendorp. 1992. An automated method for measuring time-course of gas production of feedstuff incubated with buffered rumen fluid. Neth. J. Agric. Sci. 40:401-407.
  10. Blummel, M., D. I. Givens and A. R. Moss. 2005. Comparison of methane produced by straw fed sheep in open-circuit respiration with methane predicted by fermentation characteristics measured by an in vitro gas procedure Anim. Feed Sci. Technol. 123-124:379-390. https://doi.org/10.1016/j.anifeedsci.2005.06.001
  11. Blaxter, K. L. 1962. The Energy Metabolism of Ruminants. London, Hutchinson.
  12. Blummel, M. and E. R. Orskov. 1993. Comparison of gas production and nylon bag degradability of roughages in predicting feed intake in cattle. Anim. Feed Sci. Technol. 40:109-119. https://doi.org/10.1016/0377-8401(93)90150-I
  13. Blake, D. R. and F. S. Rowland. 1988. Continuing worldwide increase in tropospheric methane, 1978 to 1987. Sci. 239:1129-1131. https://doi.org/10.1126/science.239.4844.1129
  14. Blaxter, K. L. and J. L. Clapperton. 1965. Prediction of the amount of methane produced by ruminants. Br. J. Nutr. 19:511. https://doi.org/10.1079/BJN19650046
  15. Bhatta, R., O. Enishi, N. Takusari, K. Higuchi, I. Nonaka and M. Kurihara. 2007. Diet effects on methane production by goats and a comparison between measurement methodologies. J. Agric. Sci. Cambridge (in press).
  16. Bhatta, R., K. Tajima, N. Takusari, K. Higuchi, O. Enishi and M. Kurihara. 2006b. Comparison of sulfur hexafluoride tracer technique, rumen simulation technique and in vitro gas production techniques for methane production from ruminant feeds. International Congress Series (Elsevier) 1293C: 58-61.
  17. El-Shazly, K and R. E. Hungate. 1965. Fermentation capacity as a measure of net growth of rumen microorganisms. Appl. Microbiol. 13:62-69.
  18. Eun, J. S., V. Fellner and M. L. Gumpertz. 2004. Methane production by mixed ruminal cultures incubated in dual-flow fermenters. J. Dairy Sci. 87:112-121. https://doi.org/10.3168/jds.S0022-0302(04)73148-3
  19. France, J., D. E. Beever and R. C. Siddons. 1993. Compartmental schemes for estimating methanogenesis in ruminants from isotope dilution data. J. Theor. Biol. 164:207-218. https://doi.org/10.1006/jtbi.1993.1149
  20. Greatorex, J. M. 2000. A review of methods for measuring methane, nitrous oxide and oudour emissions from animal production activities. JTI- Institutetet for jordbruks-och miljoteknik, Uppsala, Sweden. p. 19.
  21. Getachew, G., M. Blummel, H. P. S. Makkar and K. Becker. 1998. In vitro gas measuring techniques for assessment of nutritional quality of feeds: a review. Anim. Feed Sci. Technol. 72:261-281. https://doi.org/10.1016/S0377-8401(97)00189-2
  22. Getachew, G., P. H. Robinson, E. J. DePeters, S. J. Taylor, D. D. Gisi, G. E. Higginbotham and T. J. Riordan. 2005. Methane production from commercial dairy rations estimated using an in vitro gas technique. Anim. Feed Sci. Technol. 123-124:391-402. https://doi.org/10.1016/j.anifeedsci.2005.04.056
  23. Freibauer, A. 2000. New approach to an inventory of $N_2O$ and $CH_4$ emissions from agriculture in Western Europe. In: (Ed. J. van Ham, A. P. M. Baede, L. A. Meyer and R. Ybema): Non-$CO_2$ Greenhouse Gases: Scientific Understanding, Control and Implementation. Kluwer Academic Publishers, Dordrecht - Boston - London, pp. 147-148.
  24. Blummel, M., H. Steingass, K. Becker and M. Koppenhagen. 1993. Production of SCFA, $CO_2$, CH_4$ and microbial cells in vitro. Proc. Soc. Nutr. Physiol. 1, 9.
  25. Devies, D. R., M. K. Theodorou, J. Baughan, A. E. Brooks and J. R. Newbold. 1995. An automated pressure evaluation system (APES) for determining the fermentation characteristics of ruminant feeds. Ann. Zootech. 44:36. https://doi.org/10.1051/animres:19950506
  26. Edwards, G. C., H. H. Neumann, G. den Hartog, G. W. Thurtell and G. Kidd. 1994. Eddy correlation measurements of methane fluxes using a tunable diode laser at the Kinosheo Lake tower site during the Northern Wetlands Study (NOWES). J. Geophy. Res. 99:1511-1517. https://doi.org/10.1029/93JD02368
  27. Denmead, O. T., R. Leuning, I. Jamie and D. W. T. Griffith. 2000. Nitrous oxide emissions from grazed pastures: measurements at different scales. Chemosphere: Global Change Sci. 2:302-312.
  28. Denmead, O. T., L. A. Harper, J. R. Freney, D. W. T. Griffith, R. Leuning and R. R. Sharpe. 1998. A mass balance method for non-intrusive measurements of surface-air trace gas exchange. Atmos. Environ. 32:3679-3688. https://doi.org/10.1016/S1352-2310(98)00091-0
  29. Czerkawski, J. W. and G. Breckenridge. 1970. Small scale apparatus for studying rumen fermentation. Lab Practice 19:717-728.
  30. Czerkawski, J. W. and G. Breckenridge. 1977. Design and development of a long-term rumen simulation technique (Rusitec). Br. J. Nutr. 38:371-383. https://doi.org/10.1079/BJN19770102
  31. Czerkawski, J. W. and G. Breckenridge. 1969. The fermentation of sugar-beet pulp and sucrose in an artificial rumen, and the effect of linseed oil fatty acids on the fermentation. Br. J. Nutr. 23:51-66. https://doi.org/10.1079/BJN19690009
  32. Cone, J. W., A. H. Gelder, G. J. W. Visscher and L. Oudshoorn. 1996. Influence of rumen fluid and substrate concentration on fermentation kinetics measured with fully automated time related gas production apparatus. Anim. Feed Sci. Technol. 61:113-128. https://doi.org/10.1016/0377-8401(96)00950-9
  33. Boadi, D., C. Benchaar, J. Chiquette and D. Masse. 2004. Mitigation strategies to reduce enteric methane emissions from dairy cows: update review. Can. J. Anim. Sci. 84:319-335. https://doi.org/10.4141/A03-109
  34. Boadi, D. A., K. M. Wittenberg and A. D. Kennedy. 2002. Validation of the sulphur hexafluoride ($SF_6$) tracer gas technique for measurement of methane and carbon dioxide production by cattle. Can. J. Anim. Sci. 82:125-131. https://doi.org/10.4141/A01-054
  35. Harper, L. A., O. T. Denmead, J. R. Freney and F. M. Byers. 1999. Direct measurement of methane emission from grazing and feedlot cattle. J. Anim. Sci. 77:1392-1401. https://doi.org/10.2527/1999.7761392x
  36. Hegarty, R. S., A. Machmueller and G. C. Waghorn. 2004. Can tracers other than $SF_6$ be used to measure enteric methane emissions from individual animals. Clarkson, T. S. (comp.) Proceedings of the workshop on the Science of Atmospheric Trace gases, 2004. NIWA Technical Report 125. p. 139.
  37. Griffith, D. W. T., R. Leuning, O. T. Denmead and I. M. Jaomie. 2002. Air-land exchanges of $CO_2$, $CH_4$ and $N_2O$ measured by FTIR spectrometry and micrometeorological techniques. Atmos. Environ. 36:1833-1842. https://doi.org/10.1016/S1352-2310(02)00139-5
  38. IPCC. 1992. Climate Change 1992. The Supplementary Report to the Scientific Assessment (Ed. J. T. Houghton, B. A. Callander and S. K. Varney). Cambridge: Cambridge University Press.
  39. IPCC. 2001. Climate Change 2001. The Scientific Basis. Contribution of working group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge Press.
  40. Howden, S. M. and P. J. Reyenga. 1999. Methane emissions from Australian livestock: implications of the Kyoto Protocol. Aust. J. Agric. Res. 50:1285-1291. https://doi.org/10.1071/AR99002
  41. Hungate, R. E., D. W. Fletcher, R. W. Dougherty and B. F. Barrennentine. 1955. Microbial activity in the bovine rumen: its measurement and relation to bloat. Appl. Microbiol. 3:161-173.
  42. Kawashima, T. 2001. Measurement of methane production from ruminants by ventilated flow-through method with a face mask. Tsukuba workshop on 'Development of new monitoring method for methane emission from ruminants', NILGS, Japan pp. 16-19.
  43. Kajikawa, H., H. Jin, F. Terada and T. Suga. 2003. Operation and characteristics of newly improved and marketable artificial rumen (Rusitec), Mem. Natl. Inst. Livest. Grassl. Sci. Japan, N0. 2.
  44. Johnson, K. A., M. T. Huyler, H. H. Westberg, B. K. Lamb and P. Zimmerman. 1994. Measurement of methane emissions from ruminant livestock using a $SF_6$ tracer technique. Environ. Sci. Technol. 28:359-362. https://doi.org/10.1021/es00051a025
  45. Judd, M. J, F. M. Kelliher, M. J. Ulyatt, K. R. Lassey, K. R. Tate, I. D. Shelton, M. J. Harvey and C. F. Walker. 1999. Net methane emissions from grazing sheep. Global Change Biol. 5:647-657. https://doi.org/10.1046/j.1365-2486.1999.00264.x
  46. Kaharabata, S. K. and P. H. Schuepp. 2000. Estimating methane emissions from dairy cattle housed in a barn and feedlot using atmospheric tracer. Environ. Sci. Technol. 34:3296-3302. https://doi.org/10.1021/es990578c
  47. Johnson, K. A., H. H. Westberg, B. K. Lamb and R. L. Kincaid. 2001. The use of sulphur hexafluoride for measuring methane emissions from farm animals. In Proc. 1st international conference on greenhouse gases and animal agriculture, Obihiro, Hokkaido, Japan, pp. 72-81.
  48. Johnson, K. A. and D. E. Johnson. 1995. Methane emissions from cattle. J. Anim. Sci. 73:2483-2492. https://doi.org/10.2527/1995.7382483x
  49. Johnson, D. E., K. A. Johnson, G. M. Ward and M. E. Branine. 2000. Ruminants and other animals. In: Atmospheric Methane: Its role in the global environment, (Ed. M. A. K. Khalil), Springer-Verlag, Berlin Heidelberg, pp. 112-133.
  50. Lassey, K. R., M. J. Ulyatt, R. J. Martin, C. F. Walker and I. D. Shelton. 1997. Methane emissions measured directly from grazing livestock in New Zealand. Atmos. Environ. 31:2905-2914. https://doi.org/10.1016/S1352-2310(97)00123-4
  51. Lassey, K., D. Lowe and M. Manning. 2000. The trend in atmospheric methane and dgr; 13C and implications for isotopic constraints on the global methane budget. Global Biogeochemical Cycles 14:0886-6236. https://doi.org/10.1029/1999GB900094
  52. Sitaula, B. K., J. Luo and L. R. Bakken. 1992. Rapid analysis of climate gases by wide bore capillary gas chromatography. J. Environ. Quality. 21:493-496. https://doi.org/10.2134/jeq1992.00472425002100030030x
  53. Pelchen, A. and K. J. Peters. 1998. Methane emissions from sheep. Small Rumin. Res. 27:137-150. https://doi.org/10.1016/S0921-4488(97)00031-X
  54. Pell, A. N. and P. Schofield. 1993. Computerised monitoring of gas production to measure forage digestion. J. Dairy Sci. 76:1063-1073. https://doi.org/10.3168/jds.S0022-0302(93)77435-4
  55. Moate, C. P., J. L. Dunn, C. A. Bates and Y. M. Liu. 1997. An analytical model for the H X (h+g) Jahn-Teller system. J. Phys. Condens. Matter. 9:6049-6060. https://doi.org/10.1088/0953-8984/9/28/004
  56. Moe, P. W. and H. F. Tyrell. 1979. Methane production by dairy cows. J. Dairy Sci. 62:1583-1586. https://doi.org/10.3168/jds.S0022-0302(79)83465-7
  57. Murray, R. M., A. M. Bryant and R. A. Leng. 1975. Measurement of methane production in sheep. In: Tracer studies on nonprotein nitrogen for ruminants II. International Atomic Energy Agency. Vienna.
  58. Menke, K. H., L. Raab, A. Salewski, H. Steingass, D. Fritz and W. Schneider. 1979. The estimation of the digestibility and metabolizable energy content of ruminant feedingstuffs from the gas production when they are incubated with rumen liquor. J. Agric. Sci. 93:217-222. https://doi.org/10.1017/S0021859600086305
  59. Mills, J. A. N., J. Dijkstra, A. Bannick, S. B. Camel, E. Krebreab and J. France. 2001. A mechanistic model of whole-tract digestion and methanogenesis in the lactating dairy cow: model development, evaluation and application. J. Anim. Sci. 79:1584-1597.
  60. Menke, K. H. and H. Steingass. 1988. Estimation of the energetic feed value obtained from chemical analysis and gas production using rumen fluid. Anim. Res. Dev. 28:7-55.
  61. McCourt, A., T. Yan, C. S. Mayne and M. G. Porter. 2005. Prediction of methane output in beef cattle from indirect respiration calorimetry data. 2nd International Conference on Greenhouse Gases and Animal Agriculture, Zurich. pp. 405- 408.
  62. McLean, J. A. 1972. On the calculation of heat production from open-circuit calorimetric measurements. Br. J. Nutr. 27:597-600. https://doi.org/10.1079/BJN19720130
  63. Mbanzamihigo, L., V. Fievez, C. da Costa Gomez, F. Piattoni, L. Carlier and D. Demeyer. 2002. Methane emissions from the rumen of sheep fed a mixed grass-clover pasture at two fertilisation rates in early and late season Can. J. Anim. Sci. 82:69-77. https://doi.org/10.4141/A01-042
  64. Machmuller, A. and R. S. Hegarty. 2005. Alternative tracer gases for the ERUCT technique to estimate methane emission from grazing animals. 2nd International Conference on Greenhouse Gases and Animal Agriculture, Zurich. Pp. 365-368.
  65. Makkar, H. P. S., M. Blummel and K. Becker. 1995. Formation of complexes between polyvinyl pyrrolidones or polyethylene glycols and tannins, and their implication in gas production and true digestibility in in vitro techniques. Br. J. Nutr. 73:897-913. https://doi.org/10.1079/BJN19950095
  66. Lockyer, D. R. and S. C. Jarvis. 1995. The measurement of methane losses from grazing animals. Environ. Pollut. 90:383-390. https://doi.org/10.1016/0269-7491(95)00009-G
  67. Lockyer, D. R. 1997. Methane emissions from grazing sheep and calves. Agricult. Ecosys. Environ. 66:11-18. https://doi.org/10.1016/S0167-8809(97)00080-7
  68. Wilkerson, V. A., D. P. Casper and D. R. Mertens. 1995. The prediction of methane production of Holstein cows by several equations. J. Dairy Sci. 78:2402-2414. https://doi.org/10.3168/jds.S0022-0302(95)76869-2
  69. Wilkins, J. R. 1974. Pressure transducer method for measuring gas production by micro organisms. Appl. Microbiol. 27:135-140.
  70. Wratt, D. S., N. R. Gimson, G. W. Brailsford, A. M. Bromley, K. R. Lassey and M. J. Bell. 2001. Estimating regional methane emissions from agriculture using aircraft measurements of concentration profiles. Atmos. Environ. 35:497-508. https://doi.org/10.1016/S1352-2310(00)00336-8
  71. Ulyatt, M. J., S. K. Baker, G. J. McCrabb and K. R. Lassey. 1999. Accuracy of SF6 tracer technology and alternatives for field measurements. Aust. J. Agric. Res. 50:1329-1334. https://doi.org/10.1071/AR99003
  72. Waghorn, G. C. and K. J. Stafford. 1993. Gas production and nitrogen digestion by rumen microbes from deer and sheep. NZ. J. Agric. Res. 36:493-497. https://doi.org/10.1080/00288233.1993.10417750
  73. Terada, F. 1999. Methane emission from ruminant animals. In: Studies on the evaluation of estimation of anthropogenic sources and sinks of greenhouse gases. Final report of global environment research fund, Environment Agency. 157-162 (Jpn).
  74. Theodorou, M. K., B. A. Williams, M. S. Dhanoa, A. B. McAllan and J. France. 1994. A simple gas production method using a pressure transducer to determine the fermentation kinetics of ruminant feeds. Anim. Feed Sci. Technol. 48:185-197. https://doi.org/10.1016/0377-8401(94)90171-6
  75. Tilley, J. M. A. and R. A. Terry. 1963. A two stage technique for the digestion of forage crops. J. Br. Grassl. Soc. 18:104-111. https://doi.org/10.1111/j.1365-2494.1963.tb00335.x
  76. Shibata, M., F. Terada, M. Kurihara, T. Nishida and K. Iwasaki. 1993. Estimation of methane production in ruminants. Anim. Sci. Technol. (Jpn). 64:790-796.
  77. Shibata, M., F. Terada, K. Iwasaki, M. Kurihara and T. Nishida. 1992. Methane production in heifers, sheep and goats consuming diets of various hay-concentrate ratio. Anim. Sci. Technol. (Jpn). 63:1221-1227.
  78. Yan, T., R. E. Agnew, F. J. Gordon and M. G. Porter. 2000. The prediction of methane energy output in dairy and beef cattle offered grass silage-based diets. Livest. Prod. Sci. 64:253-263. https://doi.org/10.1016/S0301-6226(99)00145-1
  79. Leuning, R., S. K. Baker, I. M. Jamie, C. H. Hsu, L. Klein, O. T. Denmead and D. W. T. Griffith. 1999. Methane emissions from free-ranging sheep: A comparison of two measurement methods. Atmos. Environ. 33:1357-1365. https://doi.org/10.1016/S1352-2310(98)00365-3
  80. Liang, J. B., F. Terada and I. Hamaguchi. 1989. Efficacy of using the face mask technique for the estimation of daily heat production of cattle. In: (Ed. Y. Van Der Honing and W. H. Close). Energy Metabolism of farm Animals. Pudoc, Wageningen, the Netherlands.
  81. Baldwin, R. L., J. France, D. E. Beever, M. Gill and J. H. M. Thornley. 1987. Metabolism of the lactating cow. III. Properties of mechanistic models suitable for evaluation of energetic relationships and factors involved in the partition of nutrients. J. Dairy Res. 54:133-145. https://doi.org/10.1017/S0022029900025243
  82. Crill, P. M., J. H. Butler, D. J. Cooper and P. C. Novelli. 1995. Standard analytical methods for measuring trace gases in the environment. In: (Ed. P. A. Matson and R. C. Harriss): Biogenic trace gases: Measuring emissions from soil and water. Methods in ecology series. Oxford, Blackwell Sci. pp. 164-205.
  83. McBee, R. H. 1953. Manometric method for the evaluation of microbial activity of rumen with application to utilization of cellulose and hemicellulose. Appl. Microbiol. 1:106-110.
  84. McLean, J. A. and G. Tobin. 1987. Animal and human calorimetry. Cambridge university press. New York.
  85. Takenaka, A., K. Tajima, M. Mitsumori, H. Kajikawa, T. Osada and M. Kurihara. 2004 The measurement of hydrogen and methane gas using a semiconductor chip sensor. Clarkson, T. S. (comp.) Proceedings of the workshop on the Science of Atmospheric Trace gases, 2004. NIWA Technical Report 125. p. 139.
  86. Gimson, N. R., K. R. Lassey, G. W. Brailsford, A. M. Bromley and M. Uliasz. 2002. The determination of agricultural methane emission fluxes based on air sampling and advanced modelling techniques. In: (Ed. J. Van Ham, A. P. M. Baede, R. Guicherit and J. G. M. Williams-Jacobse). Non-$CO_2$ greenhouse gases: scientific understanding, control options and policy aspects, pp. 559-564. Millpress, Rotterdam.
  87. IPCC. 1990. Climate Change: The IPCC Impact Assessment. Canberra, Australia: Australian Government Publishing Service.

피인용 문헌

  1. Effects of encapsulated nitrate on enteric methane production and nitrogen and energy utilization in beef heifers1,2 vol.93, pp.5, 2015, https://doi.org/10.2527/jas.2014-8845
  2. Analytical methods for quantifying greenhouse gas flux in animal production systems1 vol.94, pp.8, 2016, https://doi.org/10.2527/jas.2015-0017
  3. Comparative Analysis of the Microbiota Between Sheep Rumen and Rabbit Cecum Provides New Insight Into Their Differential Methane Production vol.9, pp.1664-302X, 2018, https://doi.org/10.3389/fmicb.2018.00575