This document provides an overview of enteric methane production in ruminants and techniques for measuring methane emissions. It discusses how methane is produced in the rumen and hindgut of ruminants as a byproduct of microbial fermentation. The document summarizes several techniques used to measure methane emissions, including respiration chambers, sulfur hexafluoride tracer, and the GreenFeed system. It provides details on how the GreenFeed system works and factors that can influence methane measurements using this technique, such as animal visitation patterns and head movement during measurements.

1. DEPARTMENT OFANIMAL NUTRITION
COLLEGE OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY
DUVASU, MATHURA (U.P)

2. INTRODUCTION
¢ The last decade has seen an increasing international interest into
global warming and climate change.
¢ Greenhouse gases (GHG) absorb and re-emit radiation back to
the earth surface, trapping energy and warming environment.
(Le Treut et al., 2007)
¢ The principal GHG are: CH4, CO2, N2O, HFC, PFC and SF6.
(IPCC, 2007b)
¢ The contribution of CO2, CH4 and N2O to global GHG
emissions are 75, 15 and 10% respectively. (IPCC, 2007a)
¢ CH4 has 25 times more warming potential than CO2.

3. ¢ Livestock contribution to the global GHG emission vary from 7
to 18% , depending on the boundaries of analysis and method
used. (Steinfeld, et al., 2006)
¢ Enteric methane contributes 17 and 3.3% of global methane and
GHG emission respectively. (Knapp et al., 2014)
¢ Abatement of enteric methane emission is required to minimize
the liability of livestock production for GHG emission.
¢ An accurate, cost effective and repeatable measurement
technique of enteric methane production from ruminants is
required to evaluate a methane mitigation technology.

4. METHANOGENESIS
¢ The primary source of methane is digestive fermentation in the
rumen, which is released by eructation and exhalation.
(Murray et al., 1976)
¢ Bacterial conversion of methanogenic substrates [acetate,
formate, H2, CO2] into methane and carbon dioxide.
(Leverenz , 2002)
¢ Rumen is the predominant site of methane production (87-94%
of total production) and 6-13% derived from hindgut
fermentation.
(Torrent and Johnson, 1994)
¢ Routes of total methane release were eructation (83%),
exhalation (16%) and flatulence (1%).
(Murray et al., 1976)

5. (Schink, 2012)

6. Rumen
(87% of total)
Hindgut
(13% of total)
Flatus
(Anus)
(1% of
total)
Eructation and
exhalation
(mouth and nose)
(99% of total)
Sites of Methanogenesis and release in a dairy cow
(Torrent and Johnson, 1994)

7. A model of the production and movement of methane in sheep
(Murray et al.,1975)

8. EXPRESSING METHANE EMISSION
¢ Methane emissions can be expressed in several ways depending
on its end-use, whether it be inventory, feed utilisation efficiency
or losses due to digestion. (Hammond, 2011)
Methane
emission
Absolute daily
production
g CH4/d
Yield g CH4/kg DMI,
g CH4/kg OMI
Relative to gross energy intake % GEi
Per unit of digestible portion of feed g CH4/kg DDMI,
g CH4/kg DOMI
Emission intensity g CH4/production
(Waghorn and Clark,2016)

9. CH4 Emission Measurements
¢ Major agricultural research initiatives are in progress to
mitigate enteric CH4 emissions from ruminants.
¢ Capacity is needed to measure daily CH4 production (DMP;
g/d) from large numbers of animals for:
•Inventory verification and mitigation options
•Animal screening/breeding purposes
•Assessment of management strategies

10. Appropriate CH4 Methods for Cattle
Will depend on the objectives
•Measurements with minimal human interference
•Applicability under commercial/grazing conditions
•Required accuracy and precision
•A lower requirement for specialist knowledge
•Capability to measure a high throughput of animals
•Animal ranking/detection of treatment effects
•Emissions at different times of the day

11. Measurement methods of methane emission
Long term measurement methods
1 Respiratory chamber technique (RC) Armsby, 1903
2 Sulfur hexafluoride tracer technique (SF6) Zimmerman, 1993
3 Ventilated hood chamber or head box system Takahashi et al, 1999
Short term measurement methods
1 Face mask method Washburn and Brody, 1937
2 Portable accumulation chamber Goopy et al, 2011
3 CH4/CO2 ratio technique Madsen et al, 2010
4 GreenFeed System Zimmerman, 2011
5 Sniffer Method Gransworthy et al, 2012

12. 6 Hand laser methane detector Chagunda et al, 2013
7 Methane hood system Troy et al, 2016
Herd scale measurement techniques
1 Polytunnel method Lockyer and Jarvis, 1995
2 Micrometeorological technique Harper et al, 2011
Indirect measurements
1 Invitro measurement Menke and Steingass, 1979
2 Modeling enteric methane production Kebreab et al, 2008
3 Proxy measures of methane emissions Dijkstra et al, 2011
Other potential technology
1 Intraruminal gas sensor CSIRO. System, 2014
Continue…

16. RESPIRATION CHAMBER TECHNIQUE (RC)
¢ It is a well-established technique for determining methane emissions
from individual animals and can be either closed-circuit or open-
circuit.
¢ The RC method for measurement of enteric methane production is
often considered as the “gold standard” technique.
(O’ Hara et al., 2003)
¢ The principle of this technique is to measure the concentrations of
methane (coming from enteric fermentation) in gas samples and total
volume of air removed from the RC.
(Broucek, 2014)

17. Respiration chamber for cattle
(Pinares-Patino et al., 2012b)

18. Limitations of RC
¢ Costs of the facilities as well as operation.
¢ Restriction in number of animals/ Not applicable for pasture fed
animals
¢ Artificial environment within chamber which affects animal
behavior, feed intake and movement ability

19. SULPHUR HEXAFLUORIDE TRACER TECHNIQUE (SF6)
¢ Method usually involves the release of SF6 from a permeation
tube at a constant rate in the rumen.
(Johnson et al., 1994)
¢ Gas chromatography is used to determine the CH4 and SF6
concentrations in collection and background samples.
(Lassey et al., 1997)
¢ The SF6 technique is used to provide estimates of daily CH4
emissions for individual animals, and estimates are usually made
over 2-4 days.

21. Limitations of SF6
¢ Release rate of the permeation tube can affect CH4 production
¢ Losses of methane in the flatus
¢ Requires training of the animals to wear the equipment
¢ Interfere with an animal’s ability to eat and drink

22. GREENFEED SYSTEM (GF)
¢ Technique has been developed to overcome the limitations of
respiration chambers and SF6 technique.
¢ GreenFeed (GF) system (C-Lock Inc., Rapid City, SD, USA) was
introduced to estimate methane production by measuring gas
concentrations and airflow when cattle visit a GF unit.
(Zimmerman, 2012)
¢ The device may be used indoors or at pasture to estimate DMP of
individual cattle.

24. ¢ The GreenFeed system is a static short-term
measurement device.
¢ It measures CH4 emission from individual cattle by
integrating measurements of airflow, gas concentration,
and detection of head position during each animal’s visit
to the unit.
¢ The system measures emission using an extractor fan
and sensors which induce airflow past the animal’s head,
allowing emitted air to be collected and sampled.

25. Cow using the GreenFeed in feedlot system

26. Cow using the GreenFeed in Pasture system

27. ¢ A portable “baiting” station that measures real-time methane (CH4)
and carbon dioxide (CO2), mass fluxes from a herd/flock of
animals, several times per day.
¢ It communicates real-time over the internet, anywhere in the world
to authorized users, allowing them: To review system performance,
To control operation parameters, To review results.
¢ Head sensors; if head position is not correct the data is filtered out
¢ Cows visit three to five times each day by programming the food
reward

28. How the GreenFeed System Works
¢ Cows visit GreenFeed for controlled pellet release
¢ Pellets dropped at intervals so cows head is in hood for 3-7 min
¢ Air is drawn past the cow in the hood; flow is measured and
[CH4] and [CO2] with O2 and H2 also options
¢ Analysis of gas flux includes adjustments for background
concentrations, head position, etc.
¢ The system is calibrated and drift checked
¢ The operator can (remotely) control the system
¢ Data includes g CH4/d estimated for each 3-7 min, records time
of visits, etc.

29. THE GREENFEED SYSTEM (Zimmerman, 2012 )

30. CONCENTRATION MEASUREMENTS
CO2 is used as the key indicator to determine if a local animal is
influencing the feeder concentration measurements
¢ If CO2 levels are not changing fast = background measurement
¢ If CO2 levels are changing fast = not a background
¢ Background are determined from the CO2 sensor feedback.
The key assumptions
¢ Background concentrations don’t change unpredictably during a
visit
¢ Background during a visit is determined by using the “just before”
and “just after” visit concentrations

31. GF vs RC or SF6
¢ Uses repeated short term measurements
¢ Can be completed for many animals each day
¢ Can be operated over extended time periods
¢ No human interference
¢ Circadian pattern of methane production determined
¢ User friendly web based controls allow the user to adjust the
settings
¢ No laboratory equipment required
¢ Low “cost” per animal

32. ¢ The number, proportion and representation of animals visiting
the GF are important, with variations between individuals in
their frequency and consistency of GF visitation.
¢ All animals are not frequent GF users, and whereas some
animals can be trained to visit GF, some will not, especially at
grazing and in feedlots.
¢ A high animal use of GF resulted from training 3 weeks before
starting the trial. (Velazco, 2015)
GreenFeed visitation

33. (Garnett, 2012)
The mean number of visits per day to the Greenfeed unit

34. No of
Animals
Cattle
Physiological
state
Environment/
Diet
No. of animal
visits
Animal
visit/day
Source
24 Lactating Grazing 14/24 3.2 Garnett, 2012
14 Heifers Grazing N/A 2.7 Gunter and
Bradford, 2015
12 Heifers Grazing
pasture
12/12 2.3 Hammond et al,
2015a
10 Adult Steers Feedlot
(Silage)
8/10 1.8 Velazco et al, 2014
24 Heifer and Steers Feedlot (TMR) N/A 2.0 Cottle et al, 2015
53 Lactating Feedlot (TMR) N/A 2.0 Huhtanen et al,
2015
Summary of GreenFeed (GF) cattle visitation data

35. HEAD POSITION AND EMISSIONS
(A) One feeding period and low head movement
(Huhtanen et al., 2015)

36. (B) One feeding period and significant head movement
(Huhtanen et al., 2015)

37. Filtering data in a feed period
(Huhtanen et al., 2015)

38. ¢ There is a strong relationship between enteric methane emission
rate and the time after feeding in animals fed infrequently.
(Robinson et al., 2015)
¢ Emission pattern is affected by diet, feed allowance and feeding
patterns. (Jonker et al., 2014)
¢ Rates of methane emission are highest during and after a meal
and usually lowest before the first meal of the day.
(Laubach et al., 2013)
¢ Variation in DMP estimates associated with GF system can be
minimized if data analysis accommodates a circadian pattern
rather than random animal visits. (Hegarty, 2013)
Methane Emission Pattern

39. CH4 and CO2 Emission pattern
(Grainger et al., 2015)

40. Continuous Methane Emissions pattern from a
Cow Over 2 Days
(Laubach et al., 2013)

41. CALCULATED BASELINE EXAMPLES
(Cottle et al., 2013)

42. Chamber/GreenFeed hourly emissions herd comparison,
restricted intake
(Waghorn et al. 2011)

43. No of
Animals
Cattle
Physiologi
cal state
Diet Feeding
allowance
&
meals/day
Measur
ement
Method
Methane (g/h)
Min. Max.
Source
20 Lactating Pasture Ad lib, 2
breaks/day
GF 11 16 Waghorn et al,
2016
14 Lactating Pasture Ad lib, 2
breaks/day
GF 10 17 Garnett, 2012
12 Lactating TMR Ad lib,
once daily
RC 8 22 Crompton et al,
2011
12 Lactating TMR Ad lib,
twice daily
RC 12 21 Crompton et al,
2011
8 Heifers Silage Restricted,
twice daily
RC 4 12 Jonker et al, 2014
4 Heifer Silage Restricted,
once daily
RC &
GF
4 15 Hammond et al,
2015a
Circadian methane pattern (g/h) from cattle fed a range of diets

44. Comparison of GF with SF6
(Beef cows on pasture)
(Zimmerman et al., 2013)

45. No of
Animals
Cattle
Physiological
state
GF RC SF6 Source
6 Non Lactating 146 133 130 LEARN, 2012
4 Growing Heifer 208 209 - Hammond et al,
2015a
8 Lactating 212 207 - Velazco, 2015
48 Lactating 374 - 396 Hristov et al,
2015b
8 Lactating 468 - 467 Dorich et al, 2015
4 Growing Heifer 164 - 186 Hammond et al,
2015
Validation of GreenFeed methane estimates against other
techniques (DMP g/day)

46. GreenFeed vs Chambers vs Tracers

48. CONCLUSION
¢ There are a number of methods being used to determine CH4
emission from ruminants, all of which have strengths, weaknesses,
advantages and disadvantages for specific purposes, depending on
their conditions of use.
¢ No one method is appropriate for all conditions and objectives.
¢ GreenFeed can be quite accurate, repeatable, and produce low
variability with care in collecting and analyzing data.

49. CHALLENGES
¢ The GF method is still new but rapidly becoming established,
although it does require training and expertise to obtain good
data.
¢ Some animals need training to use the feeder, and individual
animal behaviour influences how often animals use the system.
¢ The accuracy for individual animals has been found to be
influenced by the number and duration of visits to the feeder.
¢ Intake is also not known accurately if used with grazing animals
as for other field based methods.

50. RECOMMENDATIONS
¢ Avoid analyzing GreenFeed data with low numbers of samples
(animals with low visitation).
¢ Gather 20-30 samples over two weeks per animal if individual
animal data is required. In some cases, fewer samples may be
needed if variably is lower.
¢ Use GreenFeed software to check for visit distribution over the
day.
¢ Over sampling has marginal benefits.

51. THANK YOU

53. Cow using the GreenFeed in Pasture system

55. A Greenfeed unit for use by feedlot cows

57. (Yuan, 2015)

58. Main source on inaccuracy :
¢ Measurements only when animals are present at the bin
¢ Estimation of daily emission from spot emissions is
necessary
Main limit :
¢ Only for animals fed significant amounts of concentrates
Main interest :
¢ Measurements are possible on a large number of
animals, in field conditions

59. ¢ Studies with beef cattle and sheep indicate CH4 estimated
with the SF6 tracer technique is 5 -10% lower than chambers.
(McGinn et al., 2006)
¢ Within-and between-animal variation has been considerably
larger than chamber technique. (Grainger et al., 2007)
Accuracy of SF6 Technique

60. METHANE EMISSION FROM DIFFERENT SECTORS (EPA, 2009)

63. Conversion of CH4 production (L/d) to CH4 production (g/d)
Methane production (L/d) x 10-3 = Methane volume (m3)
Methane volume (m3) x Methane density (kg/ m3)* = Methane
weight (kg)
Methane weight (kg) x 1000 = Methane production (g/d)
*Density of methane: 0.668 kg/ m3

65. Methane production (g CH4/d) from individual cows measured in
respiration chambers and the SF6 technique ( ) and the respiration
chambers and Greenfeed unit( ). The correlation coefficients (r),
associated probability values (P) and relationships are indicated.
(Garnett, 2012)

69. Diurnal CH4 emissions from a dairy cow fed once daily
measured using GF (Hristov et al., 2015)

85. DATA FILTERING
Why?
– Animals are allowed to freely move in and out of
GreenFeed
– Capture rates of gas into GreenFeed change as
the animal’s nose moves in and out of GreenFeed
– Consider the periods when the animal’s nose is
close to the manifold for flux quantification.
– Use sensor data to determine the proper periods

86. Tracer (SF6) Technique
(McGinn, 2005)

87. A cow fitted with the SF6 apparatus (Johnson et al., 2007)

88. Advantages of RC
¢ Measure accurate and reliable methane values.
¢ Individual animal feed intakes can be measured, allowing
accurate CH4 yield (g CH4/kg DMI ) to be calculated.
¢ Complete control of gas exchange
Disadvantages of RC
¢ Costs of the facilities as well as operation.
¢ Restriction in number of animals/ Not applicable for pasture fed
animals
¢ Artificial environment within chamber which affects animal
behavior, feed intake and movement ability

89. RESPIRATION CHAMBER TECHNIQUE (RC)
¢ It is a well-established technique for determining methane emissions
from individual animals and can be either closed-circuit or open-
circuit.
¢ The RC method for measurement of enteric methane production is
often considered as the “gold standard” technique due to high
accuracy and repeatability, and low animal-to-animal variations of
methane measurement using this technique.
(O’ Hara et al., 2003)
¢ The principle of this technique is to measure the concentrations of
methane (coming out through all avenues, i.e., mouth, nostrils, and
rectum from enteric fermentation) in gas samples and total volume
of air removed from the RC. ( Broucek, 2014)

90. Advantages of SF6
¢ Estimate CH4 from grazing animals
¢ Method can be employed on large numbers of animals
Disadvantages of SF6
¢ Release rate of the permeation tube can affect CH4 production
¢ Losses of methane in the flatus
¢ Requires training of the animals to wear the equipment
¢ Interfere with an animal’s ability to eat and drink