Greenhouse Gas and Odour Emissions from Pig Production Buildings and Manure Storage and Treatment Facilities

Transcription

1 Greenhouse Gas and Odour Emissions from Pig Production Buildings and Manure Storage and Treatment Facilities Claude Laguë, P.Eng., Ph.D., Professor and Dean 1 ; Adjunct Research Scientist Engineering 2 Stéphane Godbout, ing., agr., Ph.D., Research Scientist 3 Stéphane P. Lemay, P.Eng., Ph.D., Research Scientist Engineering 2 and Adjunct Professor 1 Alfred Marquis, ing., agr., Ph.D., Professor 4 Terrance A. Fonstad, P.Eng., M.Sc., Assistant Professor 1 Paper No Department of Agricultural and Bioresource Engineering, College of Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 2 Prairie Swine Centre, Inc., P.O. Box 21057, th Street East, Saskatoon, SK, S7H 5N9 3 Institut de recherche et de développement en agroenvironnement, 120A, Chemin du Roy, Deschambault, QC G0A 1S0 4 Département des sols et de génie agroalimentaire, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec, QC, G1K 7P4 Written for presentation at the CSAE/SCGR 2003 Meeting Montréal, Québec July 6-9, 2003 Abstract: It is estimated that agriculture contributes for about 10% of the total anthropogenic greenhouse gas (GHG) emissions in Canada. About 40% of the agricultural emissions of GHG originate from livestock production. In addition, odour emissions from production buildings and manure storage facilities often constitute an important source of nuisances in livestock production, especially in the pig industry. In 2001, a collaborative research effort between the Institut de recherche et de développement en agroenvironnement du Québec inc. (IRDA), Prairie Swine Centre Inc. (PSCI), Université Laval and the University of Saskatchewan was initiated with the objective of evaluating GHG (CH 4, CO 2 and N 2 O) and odour emissions for swine operations under liquid manure management. This paper presents the results obtained during the 2001 and 2002 seasons. Expressed on a basis of gram of CO 2 -equivalent per day per kilogram of live pig mass, average emissions from production buildings ranged from 21 to 145 (CO 2 ), 1 to 41 (CH 4 ), and N 2 O emissions were found to be negligible. Expressed on a basis of gram of CO 2 -equivalent per day per square meter of surface area, average emissions from manure storage facilities ranged from 31 to 265 (CO 2 ), 99 to 1,697 (CH 4 ), and N 2 O emissions were found to be negligible. Expressed on a basis of gram of CO 2 - equivalent per day per cubic meter of manure volume, average emissions from manure treatment facilities ranged from 309 to 313 (CO 2 ), 143 to 515 (CH 4 ), and 40 to 233 (N 2 O). Odour emissions from swine production buildings ranged from 2.1 to 7.3, odour units per second per square meter of floor space. Odour emissions from manure storage facilities ranged from 1.1 to 8.7 odour units per second per square meter of surface area. Odour emissions from manure treatment facilities ranged from 2.0 to 7.3 odour units per second per cubic meter of manure treated. Keywords: Concrete tank, Earthen manure storage basin, Greenhouse gas emissions, Manure treatment facility, Odour emissions, Pig production buildings, Swine housing Papers presented before CSAE/SCGR meetings are considered the property of the Society. In general, the Society reserves the right of first publication of such papers, in complete form; however, CSAE/SCGR has no objections to publication, in condensed form, with credit to the Society and the author, in other publications prior to use in Society publications. Permission to publish a paper in full may be requested from the CSAE/SCGR Secretary, PO Box 316, Mansonville, QC J0E 1X0. Tel/FAX The Society is not responsible for statements or opinions advanced in papers or discussions at its meetings.

2 CSAE/SCGR Paper page 2 The SaskPork Chair in Environmental Engineering for the Pork Industry is a joint research initiative funded and supported by: University of Saskatchewan Sask Pork Prairie Swine Centre Inc. College of Engineering Department of Agricultural & Bioresource Engineering

3 CSAE/SCGR Paper page 3 GREENHOUSE GAS AND ODOUR EMISSIONS FROM PIG PRODUCTION BUILDINGS 1. Introduction Claude Laguë, P.Eng., Ph.D. Stéphane Godbout, ing., agr., Ph.D. Stéphane P. Lemay, P.Eng., Ph.D. Alfred Marquis, ing., agr., Ph.D. Terrance A. Fonstad, P.Eng., M.Sc. After four decades of scientific efforts, the Kyoto Protocol to the United Nations Framework Convention on Climate Change was adopted in 1997 (Grubb et al. 1999). The protocol targets six different greenhouse gases: CO 2, CH 4, N 2 O, HFCs (hydrofluorocarbons), PFCs (perfluorocarbons) and SF 6 (sulphur hexafluoride) that are determinant in the global warming phenomenon. In 1990, mass emissions for the first three of these gases accounted for almost 99% of the total GHG emissions (Grubb et al. 1999). On a molecular basis, the global warming potential (GWP) of CH 4 is 21 times that of CO 2 and N 2 O has a GWP 310 times greater than CO 2 (Grubb et al. 1999). The lifetimes of these three gases once emitted into the atmosphere are approximately 100, 12 and 120 years for CO 2, CH 4 and N 2 O, respectively (Grubb et al. 1999). According to Subak et al. (1993), Canada s annual emissions amounted to 32,250 kt of CO 2, 3,218 kt of CH 4 and 37 kt of N 2 O, which represented respectively 0.5, 0.9 and 1% of the total anthropogenic world emissions. As part of the Kyoto Protocol agreement, Canada committed itself to reduce its GHG emissions during the period at a level corresponding to 94% of the 1990 emissions (AAFC 2000). Although Canada has yet to ratify the agreement, the federal government has clearly indicated that it intends to take measures aimed at reducing Canadian GHG emissions. Agriculture in general accounts for 9.5% of the total Canadian GHG emissions, with N 2 O and CH 4 contributing for 61 and 38%, respectively (AAFC 2000). It is also estimated that 42% of the agricultural GHG emissions originate from livestock operations and that one third of these are associated with manure management (AAFC 2000). There exists a need to better determine the relative contributions of the different stages of livestock production and manure management to the GHG emissions caused by this agricultural sector. The establishment of a database for the accurate assessment of current GHG emissions on the basis of livestock management systems and region has therefore been identified as an important short term need for the Canadian livestock industry (AAFC 2000). Another important emission issue for livestock operations, particularly in swine production, is odours (Schulte 1997). O Neill and Phillips (1992) have identified almost 200 compounds associated with odour emissions from animal production systems and nearly all of them are produced under anaerobic conditions that are also prone for emissions of CH 4 and CO 2. As for GHG emissions, there is a need to better assess the effects of the different components of livestock operations (animal housing and diet, manure management) on the overall operation emissions. In January 2001, the Institut de recherche et de développement en agroenvironnement du Québec inc. (IRDA), Prairie Swine Centre Inc. (PSCI), Université Laval and the University of

4 CSAE/SCGR Paper page 4 Saskatchewan have initiated a collaborative research project aimed at determining benchmark values for GHG and odour emissions from pig production buildings and manure storage and treatment facilities. Funding for this project is provided by the Climate Change Funding Initiative in Agriculture (CCFIA) program of Agriculture and Agri-Food Canada, the Centre de recherche industrielle du Québec (CRIQ), the Fédération des producteurs de porcs du Québec (FPPQ) and Sask Pork. 2. Objectives and Expected Benefits The general objective of the research project is to evaluate GHG (CH 4, CO 2 and N 2 O) and odour emissions for swine operations in two provinces (Québec and Saskatchewan) under liquid manure management. More specifically, the study is targeted at: 1. determining the GHG and odour emissions from different types of swine production buildings and building floor designs during a 2-yr period; 2. determining the GHG and odour emissions from different types of manure storage (covered and uncovered) and treatment facilities over a 2-year period, and 3. determining the GHG and odour emissions associated with the agitation and emptying of manure storage facilities. This paper follows up on work reported upon by Laguë et al. (2002) and Savard et al. (2002) and it presents experimental GHG and odour emission results obtained during the 2001 and 2002 seasons. 4. Methodology Laguë et al. (2002), Savard et al. (2002) and Godbout et al. (2003) have presented the experimental sites, methods and equipment used for determining GHG and odour emissions from production buildings, manure storage facilities and manure treatment facilities. The reader is refereed to these papers for more details on the experimental methodology. 5. GHG and Odour Emissions from Production Buildings Table 1 presents GHG emissions from the two different sites for four sampling days between December 2001 and October Carbon dioxide is the most important contributor to GHG emissions from swine buildings. When averaged over the four sampling days, CO 2 emissions varied from 21.0 to g/day-kg pig depending on the room type. These results are higher than most of the data published in the literature. Converting CO 2 emission data for grower-finisher pigs as measured by Gallman and Hartung (2000), Jeppson (2000) and Hinz and Linke (1998a,b) to the same units than those in this study yielded values of 0.18, 21.0 and 31.0 g/day-kg pig respectively. On a mass basis, CH 4 emissions were much lower than CO 2 emissions ranging from 0.07 to 1.96 g/day-kg pig. Nitrous oxide production was practically negligible. Even when CH 4 and N 2 O emissions are expressed in terms of mass of CO 2 -equivalent by considering their respective GWP, CO 2 emissions remain much larger than those for CH 4 and N 2 O.

5 CSAE/SCGR Paper page 5 Table 1. GHG emissions from different room types in two swine production buildings. Room type GHG emission (g/day-kg pig ) GHG emission CO 2 equivalence (g CO 2 equivalent/day-kg pig ) CO 2 CH 4 N 2 O CO 2 CH 4 N 2 O Site 1 Farrowing Gestation Nursery Grower-Finisher Site 2 Farrowing Gestation Nursery Grower-Finisher (Partially slatted floor) Grower-Finisher (Fully slatted floor) Canada s current annual emissions of GHGs stand at 694 Tg of CO 2 equivalent (CPC 2002a). Considering there were 13.2 millions pigs on Canadian farms in 2002 (CPC 2002b) and using the average emissions for sows (farrowing and gestation) and other pigs (nursery and grower-finisher) measured over this project so far (Table 1), swine building CO 2 emissions only would be estimated at 27.1 megatonnes per year (4% of total Canadian GHG emissions). Based on AAFC (2000), agriculture as a whole accounts for 9.5% of Canada s GHG emissions. Although the data collection of the current project should be completed before any strong concluding statements could be made, the comparison between CO 2 calculated emissions from this study and previous references illustrates one more time the importance and urgency of getting reliable baseline GHG emissions from the swine industry in Canada. The lowest CO 2 production was measured in gestation rooms while the largest emissions occurred in grower-finisher rooms. As most of the CO 2 is produced by the animal respiration, these results are to be expected and were consistent between both sites. In the same way, the floor design did not affect CO 2 production. However, the CH 4 production rate was higher with the fully slatted floor room (0.43 g/day-kg pig ) than with the partially slatted floor room (0.24 g/day-kg pig ). The larger contact area between the manure and the air likely promotes higher methane emissions. The various types of room in these buildings emitted between 2.1 and 7.3 O.U./s-m 2 (Table 2). Nursery pigs in site 1 produced the highest odour emission with 7.3 O.U./s-m 2 followed by the grower-finisher rooms of site 2 at 6.2 and 7.1 O.U./s-m 2. The nursery room of site 1 is based on an older design where more manure accumulates on the floor compared to the nursery room at site 2. However, the gestation room produced the most important odour emissions. On a site basis, considering the number of grower-finisher rooms required with a farrow-to-finish production system, these rooms constituted the largest source of odours.

6 CSAE/SCGR Paper page 6 Heber et al. (1998) and Godbout et al. (2001) reported odour emissions of 5 O.U./s-m 2 and 10 O.U./s-m 2 for grower-finisher pigs, respectively. Odour emissions measured in this study, especially for site 2, are very similar to what was published before (6.2 and 7.1 O.U./sm 2 ). Considering the same units, the results from Verdoes and Ogink (1997) for farrowing sows would vary between 3.5 and 5.4 O.U./s-m 2 for farms 1 and 2 compared to the 2.8 and 3.5 O.U./sm 2 that was measured. Odour emissions observed in this study so far may be slightly different that the values published by previous authors but they are certainly within the same order of magnitude. Odour emissions from farrowing and gestation rooms are fairly similar at both sites. Emissions from the nursery are slightly different but the floor space allowance and the room design are not the same. Grower-finisher rooms at site 2 produced approximately three times more odour on a square meter basis than the grower-finisher room at site 1. More investigations will be required to explain this variation. Table 2. Odour emissions from different room types in two swine buildings. Room type Floor space allowance (m 2 /pig) Odour emission (O.U./s-m 2 ) Total odour emission (O.U./s-room) Site 1 Farrowing Gestation Nursery Grower-Finisher Site 2 Farrowing Gestation Nursery Grower-Finisher (Partially slatted floor) Grower-Finisher (Fully slatted floor) GHG and Odour Emissions from Manure Storage Facilities Table 3 summarizes the GHG emission results from manure storage facilities and manure treatment systems observed in Québec (QC) and Saskatchewan (SK) in 2001 and Two types of manure storage facilities have been monitored: earthen manure basins (EMB) and concrete tanks. The stored manure in some of the monitored EMB (covered EMB) was covered with a layer of chopped barley straw blown on the surface of the manure. Emission data for storage facilities are reported by unit area of manure storage surface and those for treatment systems are reported by unit volume of manure contained in the treatment systems. The CO 2 emissions from manure storage facilities varied from 30.6 to g/day m 2. Measured CH 4 emissions in this study (4.7 to 80.8 g/day-m 2 ), when converted (1.6 to 28.0 g/day m 3 ) are more important than those measured by Phillips and al. (1997) that ranged

7 CSAE/SCGR Paper page 7 between to 0.39 g/m 3 day. However, they are similar to the emissions measured by Husted (1994) for pig slurry (12 g /m 3 day). As mentioned by many authors, N 2 O emissions from manure storage facilities are insignificant. Table 3. GHG emissions from manure storage facilities and treatment systems Storage and treatments facilities GHG emission g / day-m 2 CH 4 CO 2 N 2 O CO 2 -equivalent Uncovered EMB Covered EMB Uncovered concrete tank (SK) Uncovered concrete tank (QC) Low aerated EMB g /day-m 3 Bio-filtration Aerobic and anoxic manure treatment The CH 4 and CO 2 emissions from the manure treatment facilities ranged from 6.8 to 24.5 g/day m 3 and from 309 to 313 g/day m 3 respectively. The emissions of CO 2 are very high because both systems use a high airflow. In contrast to storage, both manure treatments produce N 2 O emissions: these ranged from 0.13 to 0.75 g/day m 3. Table 3 also shows that the bio-filtration unit produces more emissions than the aerobic and anoxic manure treatment unit. The production of CH 4 during the bio-filtration process is responsible for this difference. Further analyses have been completed on the GHG emission data from manure storage facilities in Saskatchewan during the 2001 and 2002 seasons and the results are presented on Figures 1 to 4. On each of these bar graphs, the height of the bars corresponds to the average emissions while the height of the vertical lines corresponds to the range of experimental values observed (i.e. minimum to maximum). The following observations can be made: The variability of GHG emission data was very high; observed minimum and maximum values, all expressed in g CO 2 -equivalent / m 2 - day, were and for carbon dioxide, and 10,180 for methane, and and for nitrous oxide; GHG emissions were lower between the hours of 10:00 and 18:00 than during the rest of the day; GHG emissions were higher during the summer and lower during the spring seasons; The presence of a blown chopped straw cover on manure storage facilities did reduce GHG emissions; and

8 CSAE/SCGR Paper page 8 Overall, average methane emissions were four times larger than those of carbon dioxide (659.9 vs g CO 2 -equivalent / m 2 - day) while nitrous oxide emissions ( g CO 2 -equivalent / m 2 - day) were negligible CO2 CH4 N2O Unit Gas Emissions (g of CO2-equivalent / m2 - day) :00-06:00 06:00-10:00 10:00-14:00 14:00-18:00 18:00-22:00 22:00-02:00 Time of Day Figure 1. Effect of time of day on GHG emissions from pig manure storage facilities in Saskatchewan. (bar = average; vertical line = minimum to maximum range)

9 CSAE/SCGR Paper page CO2 CH4 N2O Unit Gas Emissions (g of CO2-equivalent / m2 - day) Spring Summer Fall Season Figure 2. Effect of season on GHG emissions from pig manure storage facilities in Saskatchewan. (bar = average; vertical line = minimum to maximum range)

10 CSAE/SCGR Paper page CO2 CH4 N2O Unit Gas Emissions (g of CO2-equivalent / m2 - day) Uncovered EMS Covered EMS Uncovered Tank Type of Storage Facility Figure 3. Effect of type of storage facility on GHG emissions from pig manure storage facilities in Saskatchewan EMS = earthern manure storage Covered EMS = EMS covered with a layer of chopped barley (bar = average; vertical line = minimum to maximum range)

11 CSAE/SCGR Paper page CO2 CH4 N2O Unit Gas Emissions (g of CO2-equivalent / m2 - day) Overall Emissions Figure 4. Overall GHG emissions from pig manure storage facilities in Saskatchewan by type of GHG. (bar = average; vertical line = minimum to maximum range)

12 CSAE/SCGR Paper page 12 Odour emissions from manure storage facilities measured in this study varied from 1.1 to 8.7 O.U./s-m 2 (Table 4). These values are of the same order of magnitude that those found in the literature (1 to 18 O.U./s-m 2 ) for liquid manure storage facilities. The addition of a blown chopped straw cover over earthen manure storages allowed for a reduction of 83 % of the odour emissions. The uncovered tank was the most odorous storage system (8.7 O.U./s-m 2 ). The biofiltration treatment system produced more odour emissions than the aerobic and anoxic treatment system. Table 4. Odour emissions from manure storage facilities and treatment systems. Storage and treatment facilities Odour emissions Storage O.U./s-m 2 Treatment O.U./s-m 3 Uncovered EMB Covered EMB Uncovered tank Biofiltration Aerobic and anoxic manure treatment Summary Based on two seasons of GHG and odour emission measurements from swine production buildings and manure storage and treatment facilities, the following conclusions can be drawn: 1. Expressed on a basis of gram of CO 2 -equivalent per day per kilogram of live pig mass, carbon dioxide emissions from production buildings ranged from a low of 21 (gestation rooms) to a high of 145 (grower-finisher rooms), methane emissions varied between 1 (gestation rooms) and 41 (nursery rooms), and nitrous oxide emissions were found to be negligible. 2. Odour emissions from the two swine production buildings ranged from a low of 2.1 to a high of 7.3 odour units per second per square meter of floor space. 3. Expressed on a basis of gram of CO 2 -equivalent per day per square meter of surface area, average carbon dioxide emissions from manure storage facilities ranged from a low of 31 (low aerated earthen manure basin) to a high of 265 (uncovered earthen manure basin), average methane emissions varied between 99 (covered earthen manure storage basin) and 1,697 (uncovered manure storage basin), and average nitrous oxide emissions were found to be negligible. 4. Expressed on a basis of gram of CO 2 -equivalent per day per cubic meter of manure volume, average carbon dioxide emissions from manure treatment facilities ranged from a low of 309 (bio-filtration) to a high of 313 (aerobic and anoxic treatment), average methane emissions varied between 143 (aerobic and anoxic treatment) and 515 (bio-filtration), and average nitrous oxide emissions were comprised between 40 (aerobic and anoxic treatment) and 233 (bio-filtration). 5. Odour emissions from manure storage facilities measured in this study ranged from a low of 1.1 to a high of 8.7 odour units per second per square meter of surface area.

13 CSAE/SCGR Paper page Odour emissions from manure treatment facilities measured in this study ranged from a low of 2.0 to a high of 7.3 odour units per second per cubic meter of manure volume. A final series of experiments will be completed during the 2003 season. 7. Acknowledgments The authors acknowledge the financial support provided by the Climate Change Funding Initiative in Agriculture (CCFIA) program of Agriculture and Agri-Food Canada, the Centre de recherche industrielle du Québec (CRIQ), the Fédération des producteurs de porcs du Québec (FPPQ) and Sask Pork. Strategic funding to the Sask Pork Chair in Environmental Engineering for the Pork Industry by the Agri-Food Innovation Fund of Saskatchewan, Prairie Swine Centre Inc. and Sask Pork is also gratefully acknowledged. Thanks are extended to Alberta Pork, the Manitoba Pork Council and Sask Pork for the strategic funding provided to Prairie Swine Centre Inc. The following individuals provided scientific and technical assistance for the completion of this project: L. Jaulin (Centre de recherche industrielle du Québec); R. Joncas (Institut de recherche et de développement en agroenvironnement du Québec); L. Chénard, R. Fengler and K. Stewart (Prairie Swine Centre Inc.); C. De Foy, R. Lagacé and L.-O. Savard (Université Laval); J. Agnew, M.T. Alam and É. Gaudet (University of Saskatchewan). 8. References Agriculture and Agri-Food Canada (AAFC) Reducing Greenhouse Gas Emissions from Canadian Agriculture. Options report prepared by the Agriculture and Agri-Food Canada Climate Change Table. Publication no. 2028/E. Agriculture and Agri-Food Canada. Ottawa, ON. 72 pages. Canadian Pork Council (CPC). 2002a. Greenhouse gas mitigation strategy for the Canadian hog industry. Discussion Paper, June. Available online: Accessed on February 6, Canadian Pork Council (CPC). 2002b. Description of Canadian hog farms, statistic page. Available online: Accessed on June 24, Gallman, E. and E. Hartung Evaluation of the Emission Rates of Ammonia and Greenhouse Gases from Swine Housings in: Proceedings of the 2 nd International Conference on Air Pollution from Agricultural Operations, Des Moines, IA, USA: ASAE. Godbout, S., C. Laguë, C, S.P. Lemay, A. Marquis, T.A. Fonstad Greenhouse gas and odour emissions from swine operations under liquid manure management in Canada. Conference presented at the CIGR Section II Symposium on "Gaseous and Odour Emissions from Animal Production Facilities". Bonn, Germany. Godbout, S., S. P. Lemay, R. Joncas, J.P. Larouche, D.Y. Martin, J.F. Bernier, R.T. Zijlstra, L. Chénard, A. Marquis, E.M. Barber and D. Massé Oil sprinkling

14 CSAE/SCGR Paper page 14 and Dietary Manipulation to Reduce Odour and Gas Emissions from Swine Buildings Laboratory Scale Experiment. International Livestock Environment VI, Louisville, Kentucky, May 2001, ASAE, pp Grubb, M., C. Vrolijk and D. Brack The Kyoto Protocol A Guide and Assessment. Royal Institute of International Affairs, London, UK. 342 pages. Heber, A., T.T.Lim, J. Ni and A.L.Sutton Odor and gas emission form anaerobic treatment of swine manure. Final report presented to the Office of the Commissioner of Agriculture, Indianapolis, Indiana, USA, 41 p. Hinz, T. and S. Linke. 1998a. A comprehensive experimental study of aerial pollutants in and emissions from livestock buildings - Part 1: Methods. Journal of Agricultural Engineering Research 70 (1): Hinz, T. and S. Linke. 1998b. A comprehensive experimental study of aerial pollutants in and emissions from livestock buildings - Part 2: Results. Journal of Agricultural Engineering Research 70 (1): Husted, J Seasonal variation in methane emission from stored slurry and solid manure. Journal of Environmental Quality 23: Jeppson, K.-H Carbon Dioxide Emission and Water Evaporation from Deep Litter Systems. Journal of Agricultural Engineering Research 77 (4): Laguë, C., S.P. Lemay, T.A. Fonstad, L. Chénard, É. Gaudet and R. Fengler Greenhouse gas and odour emissions from pig production buildings and manure storage facilities. CSAE Paper Conference presented at the Annual Meeting of the Canadian Society of Agricultural Engineers. Saskatoon, SK. O Neill, D.H. and V.R. Phillips A Review of the Control of Odour Nuisance from Livestock Buildings: Part 3, Properties of the Odourous Substances which Have Been Identified in Livestock Wastes or in the Air Around Them. Journal of Agricultural Engineering Research 53: Phillips, V.R, R.W. Sneath, A.G. Williams, S.K. Welch, L.R. Burgess, T.G.M. Demmers and J.L. Short Measuring emission rates of ammonia, methane and nitrous oxide from full-sized slurry and manure stores, in: Ammonia and odour control from animal production facilities, Proceedings of the International Symposium, AB Rosmalen, The Netherlands: NVTL. Savard, L.O., A. Marquis and S. Godbout Greenhouse gas production from swine manure storage and treatment facilities. CSAE/SCGR Paper Conference presented at the Annual Meeting of the Canadian Society of Agricultural Engineers. Saskatoon, SK. Schulte, D.D Critical Parameters for Emissions, in: Ammonia and Odour Control from Animal Production Facilities, Proceedings of the International Symposium, AB Rosmalen, The Netherlands: NVTL. Subak, S., P. Raskin and D. Von Hippel National Greenhouse Gas Accounts: Current Anthropogenic Sources and Sinks. Climatic Change 25: Verdoes, N. and N.W.M. Ogink Odour emission form pig houses with low ammonia emission. Proceedings of the international symposium, Ammonia and odour control form animal production facilities. CIGR, EurAgEng and NVTL, Vinkeloord, The Netherlands, October 1997, Vol. 1,