Verifying the Methane Conversion Factor for Manure Storages in Abbotsford

Based on our climate and manure management practices, methane emission from dairy manure storages is 5-10% of the potential emissions, and ranges from 3000 to 10,000 tonnes of carbon dioxide equivalents per year.

It is important to estimate the baseline methane emissions from manure storages in order to calculate any potential greenhouse gas emissions savings gained by implementing anaerobic digestion.

We have reviewed the science on methane emissions from manure stored at cooler temperatures based on both Canadian and European research. We have reviewed manure management systems on dairy farms in Abbotsford. A key factor in estimating actual methane emissions from dairy manure storages in Abbotsford is the methane emissions factor (MCF).

Baseline methane emissions from manure storages are calculated using internationally accepted protocol. They are estimated by measuring the number of animals, the amount of volatile solids excreted by each animal, the potential methane production per kg of volatile solids, and the methane conversion factor (MCF). This MCF is a percentage between 0 and 100%, where 100% is equal to the potential methane production per kg of volatile solids. The MCF is primarily a function of manure storage temperature and the length of time that manure is stored.  There are a wide range of MCF values used, ranging from 39% used for the Vanderhaak digester in Lynden WA (Washington State 2008), to 25.8% used in British Columbia (Verge et al. 2007, Janzen 2009, Government of Alberta 2010). The internationally accepted IPCC protocols (IPCC 1996, IPCC 2006) use an MCF value of 10% for liquid manure storage in cool climates.

It is important to note here that IPCC (2006) suggests a MCF of 68% for unovered anaerobic lagoon (Table 10.17). Table 10.18 of (IPCC 2006) has additional important information on the definition of uncovered anaerobic lagoon:  “A type of liquid storage system designed and operated to combine waste stabilization and storage. Lagoon supernatant is usually used to remove manure from the associated confinement facilities to the lagoon. Anaerobic lagoons are designed with varying lengths of storage (up to a year or greater), depending on the climate region, the volatile solids loading rate, and other operational factors. The water from the lagoon may be recycled as flush water or used to irrigate and fertilise fields.” While there are a number of uncovered anaerobic lagoons in Abbotsford, the storage capacity in most cases is less than 6 months as per a review in a previous post. The higher MCF for anaerobic lagoons also assumes a signficant effect of inoculation of methane forming bacteria during long term storage. Sommer et al. (2007) reported that methane production from stored cattle manure was not significant at 10 C, even when the manure was inoculated.

Washington State used an MCF of 39% (Washington State 2008). “Using the Intergovernmental Panel on Climate Change (IPCC) Tier 2 methodology for estimating methane emissions from liquid/slurry manure storage facilities and a methane conversion factor of 39 percent for cool climates” (Washington State 2008). This number comes from IPCC (2000) Table 4.11 MCF values for manure management systems not specified in the IPCC Guidelines (Judgement by Expert Group). However, if we go to manure management systems actually specified in the IPCC (1996) Guidelines, Table 4.8 clearly identifies the MCF factor for liquid manure systems in cool climates at 10%, not 39%. So, where did the MCF of 39% come from? It came from a supporting paper for the IPCC (1996) by Zeemans and Gerben (1997), which includes information by Zeemans (1994). Its interesting to note that Zeemans (1994) concludes: “when continuously 15% of the storage is filled, no gas production is produced, at a temperature of 15°C and a storage capacity < 100 days and at a temperature of 10°C and a storage capacity < 150 days.” We have to conclude based on this information, that the MCF of 10% may even overestimate actual methane emission from manure storages under conditions in Abbotsford.  Soliva (2006) also considered the 39% and 10% default MCF values reported in IPCC (2000) and made the same conclusion that 10% was the more realistic value for manure management in Switzerland.

The MCF factor of 25.8% for manure storages in British Columbia came originally from a paper by Verge et al. (2007). They state that this value was based on a US paper that extrapolated optimal methane emission at various temperatures using the van’t Hoff-Arrhenius equation. There was no experimental data used in this calculation, and differential temperature response by various microbes was not taken into account.  We know from previous posts that the methane producing bacteria are more sensitive to temperature than the acid formers and that VFA and ammonia accumulation may inhibit the methane producting bacteria in a manure storage. Based on the fact that this MCF value of 25.8% is theoretical only, and is not supported by actual data either in Canada or in Europe, there is no evidence that this value is relevent to manure management in British Columbia.

Based on actual measurements of methane emissions at low temperatures and our manure storage management in British Columbia, and using the rule of conservancy, a realistic MCF factor is 5%. This also fits with our actual measurements of methane emission from manure storages in 2004.  However, I suggest that we could potentially accept the IPCC (1996) and IPCC (2006) MCF value of 10%. Rodhe et al. (2009) estimated that the MCF for dairy manure in Sweden was 3%, based on shorter manure storage periods, and frequent manure applications during the summer. Karimi-Zindashty et al. (2012) concluded that obtaining parameters specific to regions and animal subcategories is very important in order to estimate GHG emissions more accurately and to reduce the uncertainties in agricultural GHG inventories.

Understanding the actual methane emissions from manure storages becomes important when estimating any methane emission reduction resulting from anaerobic digestion. The estimated 3000 to 10,000 tonnes CO2 equivalent of methane emission from manure storages is significantly lower than the 55,000 tonnes CO2 equivalent emitted directly from the dairy cattle (to be reviewed in a following post).

We have to be careful not to misunderstand where the methane comes from with animals and animal manure, and how much can be recovered.

References

Government of Alberta. 2010. Quantification Protocol for Emission Reductions from Dairy Cattle. Specified Gas Emitters Regulation. Version 1.0

IPCC. 1996. Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories. Reference Manual Volume 3. Chapter 4. Agriculture. http://www.ipcc-nggip.iges.or.jp/public/gl/guidelin/ch4ref2.pdf

IPPC. 2000. Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories.  J. Penman, D. Kruger, I. Galbally, T. Hiraishi, B. Nyenzi, S. Emmanul, L. Buendia, R. Hoppaus, T. Martinsen, J. Meijer, K. Miwa, and K. Tanabe (Eds). Institute for Global Strategies, Japan.

IPCC. 2006. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Volume 4. Agriculture, Forestry and Other Land Use. Chapter 10. Emissions from Livestock and Manure Management. http://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/4_Volume4/V4_10_Ch10_Livestock.pdf

Janzen, R. 2009. Science Discussion Paper – Certification of a Greenhouse Gas Protocol and Calculator for the Canadian Dairy Industry. http://www.adfiresearch.org/GHG/Appendix_B.pdf

Karimi-Zindashty, Y., J.D. MacDonald, R.L. Desjardins, D.E. Worth, J.J. Hutchinson, and X.P.C. Verge. 2012. Sources of uncertainty in the IPCC Tier 2 Canadian livestock model. Journal of Agricultural Science 150:556-559.

Mangino, J., D. Bartram and A. Brazy. 2001. Development of a methane conversion factor to estimate emissions from animal waste lagoons. Technical Report 14 pp. http://www.epa.gov/ttnchie1/conference/ei11/ammonia/mangino.pdf

Rodhe, L., Ascue, J. and Nordberg, Å. 2009. Emissions of greenhouse gases (methane and nitrous oxide) from cattle slurry storage in Northern Europe. IOP Conference Series: Earth and Environmental Science 8.

Soliva, C.R. 2006. Report to the attention of IPCC about the data set and calculation method used to estimate methane formation from enteric fermentation of agricultural livestock population and manure management in Swiss agriculture. Federal Office for the Environment, Berne, Switzerland.

Sommer, S.G., S.O. Petersen, P. Sorensen, H.D. Poulsen and H.B. Moller. 2007. Methane and carbon dioxide emissions and nitrogen turnover during liquid manure storage. Nutrient Cycling in Agroecosystems  78: 27-36.

Verge, X.P.C., J.A. Dyer, R.L. Desjardins and D. Worth. 2007. Greenhouse gas emissions from the Canadian dairy industry in 2001. Agricultural Systems 94: 683-693.

Washington State. 2008. Climate Action Team. Draft Development of Potential Offsets Related to Anaerobic Digestion. Agricultural Sector Carbon Market Workgroup.

Zeeman, G., and S. Gerbens. 1997. CH4 Emissions from Animal Manure. In Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories.

Zeeman, G. 1994. Methane production/emission in storage’s for animal manure. Fertilizer Research 37: 207-211.