A-8

This section presents estimates of global CH, emissions from ruminants
published in three of the above mentioned studies:

° Crutzen et al, (1986): The study by Crutzen et al. is the most
comprehensive description of CH, emissions to date.

° Blake (1984): Blake used data from Woodwell (1970) and Ritzman
and Benedict (1938) to estimate global emissions via two different

methods.

° Lerner et al, (1988): Lerner et al. gathered detailed data on
animal populations and estimated CH, emissions by latitude and
longitude.

Exhibit A-3 summarizes the estimates presented by these authors. Each
is discussed in turn.

CRUTZEN ET AL.

Crutzen et al. estimated total annual CH, emissions by: (1) estimating
the average CH, production per animal in various regions of the world; (2)
multiplying the average emissions per animal by the total population of
animals in each region; and (3) summing across the regions. The average
CH, production rates were derived from the Blaxter and Clapperton (1965)
relationship (discussed above) and other sources. The population data for
each region were taken primarily from FAO statistics. This publication by
Crutzen et al. is the most comprehensive description of CH, emissions from
ruminants to date. A copy of this publication is included as Appendix C.

Exhibit A-4 presents the Crutzen at al. estimates for CH, emissions.
Bovines, including all cattle used for beef production, milk production,
and draft animals, are the largest source, accounting for 70 percent of the
total estimate and about 75 percent of the CH, emissions from managed
ruminants.

As shown in Exhibit A-4, Crutzen et al. divided the world into developed
and developing countries for evaluating bovine emissions. The emissions
estimates for each is based on the following:

° Developed Countries. The emissions rate. for all developed
countries plus Brazil and Argentina is based on evaluations in
each of the following countries:

- United States and Canada. This region has about 114 million
cattle, which can be divided into three main groups, each

with different CH, emissions rates: dairy cows; beef cattle
on feed; and beef cattle on the range. In the U.S., these


24

(1 Tg = 10%? g) would be produced. This amounts to 20 percent of the
estimate of CH, emissions from livestock.

2.2 GLOBAL METHANE EMISSIONS FROM RUMINANTS

Crutzen et al. (1986) have performed the most comprehensive assessment
of CH, emissions from ruminants to date. Based on a review of CH, yields
and feed characteristics and consumption, Crutzen et al. estimate the

following:

° e_in developed countries, Brazil and Arge' ai: average
annual CH, emissions per head of 55 kg/yr; total annual emissions
of 31.5 Tg/yr;

° Cattle in developing countries: average annual CH, emissions per
head of 35 kg/yr; total annual emissions of 22.8 Tg/yr;

° Sheep in developed countries: average annual CH, emissions per
head of 8 kg/yr; total annual emissions of 3.2 Tg/yr;

° Sheep _in developing countries and Australia: average annual CH,

emissions per head of 5 kg/yr; total annual emissions of
3.7 Tg/yr;

° uffalo (virtua 1 e_in develo, countries): average
annual CH, emissions per head of 50 kg/yr; total annual emissions
of 6.2 Tg/yr; and

° Goats (virtually all are in dev countries): average annual
CH, emissions per head of 5 kg/yr; total annual emissions of 2.4
Tg/yr; and

° Camels (virtually all are in developing countries): average

annual CH, emissions per head of 58 kg/yr; total annual emissions
of 1.0 Tg/yr.

The total of these estimated emissions is about 71 Tg/yr, over 75 percent
of which is associated with cattle.

In addition, Crutzen et al. estimate an additional 2.9 Tg/yr of CH,
emissions associated with the digestive systems of pigs, horses, mules, and
humans.!2 Approximately 2 to 6 Tg/yr of emissions is estimated for wild
ruminants throughout the world, and emissions from large non-ruminants are
expected to be small. The overall total for these sources of CH, is on the
order of about 80 Tg/yr.

12 Note that these estimates do not include potential CH, emissions
associated with wastes.


REDUCING METHANE EMISSIONS FROM LIVESTOCK:

OPPORTUNITIES AND ISSUES

by:
Michael J. Gibbs
Lisa Lewis
John S. Hoffman

U.S. Environmental Protection Agency

August 1989


A-17

Krishna, G., M.N. Razdan, and S.N. Ray, "Effect of Nutritional and Seasonal
Variations on Heat and Methane Production in Bos indicus," Indian Journal
of Animal Science, Vol. 48, 1978, pp. 366-370.

Lerner, J., E. Matthews, and I. Fung, Methane Emissio:

f:
Global High-Resolution Database, NASA Goddard Space Flight Center.
Institute for Space Studies, Vol. 2, 1988, pp. 139-156.

Moe, P.W. and H.F. Tyrrell, "Methane Production in Dairy Cows," Journal of
Dairy Science, Vol. 62, 1979, pp.1583-1586.

NRC, Nutrient Requirements of Beef Cattle, National Academy Press,
Washington, D.C., 1984.

Odend’hal, S., "Energetics of Indian Cattle in their Environment," Human
«Ecology, Vol. 1, No. 1, 1972, pp. 3-22.

Preston, T.R. and R.A. Leng, tchin, uminant Production stems wi

Available Resources in the Tropics and Sub-tropics, Penambul Books,
Armidale, New South Wales, Australia, 1987.

Ritzman, E.G. and F.G. Benedict, "Nutritional Physiology of the Adult
Ruminant," Carnegie Institute, Washington, D.C., 1938, pp. 24-30.

Rumpler, W.V., D.E. Johnson, and D.B. Bates, "The Effects of High Dietary
Cation Concentration, on Metinanogenesis by Steers Fed Diets With and Without

Ionophores," Journal of Animal Science, Vol. 62, 1986, pp. 1737-1741.

Seiler, W., "Contribution of Biological Processes to the Global Budget of

- CH, in the Atmosphere," Current Perspectives in Microbial Ecology, M.J. Klug
and C.A. Reddy, eds., American Society of Meteorology, 1984, pp. 468-477.

Sheppard, J.C., H. Westberg, J.F. Hopper, and K. Ganesan, "Inventory of
Global Methane Sources and Their Production Rates," Journal of Geophysical
Research, Vol. 87, 1982, pp. 1305-1312.

Woodwell, G. M., "The Energy Cycle of the Biosphere," Scientific American,
Vol. 223, 1970, pp. 64-74.


B-1ll_ -
EXHIBIT B-4
PERCENTAGE OF SIMULATED EQUILIBRIUM TEMPERATURE CHANGE AVOIDED

BY A RANGE OF REDUCTIONS IN METHANE EMISSIONS
FROM RUMINANT ANIMALS

RCW scw
8 8
ZZ Rew wi 25% reduction (Z1 scww 25% reduction
ae
BB Rew w 75% reduction mY EY scw wi 75% reduction
6F 6r
i i
tet fe me gL
3 = 3
Sat Be S 4h
ae
a 4 ak
Besoted
. j 27 a I 2-
ow =
tPF Be 1h
LY Z
° °

2025 2050 2075 2100 2025 2050 2075 2100

RCW and SCW refer to Rapidly Changing World and Slowly Changing World
scenarios, respectively. Percentages estimated by dividing the reduction
in global equilibrium temperature changes estimated to be associated with
25 to 75 percent reductions in methane emissions from ruminant animals by
the globél equilibrium temperature changes anticipated for the original RCW
and SCW scenarios.

The simulated equilibrium temperature changes displayed in Exhibit B-3
above produce slightly different estimates of these percentage due to
rounding.



14

Compared to other key greenhouse gases (e.g., carbon dioxide (C02),
nitrous oxide (N20), and CFCs), this reduction is relatively modest. To
stabilize the concentrations of these other gases, the following reductions
are required from current anthropogenic emissions levels: C02: 50 to 75
percent; N20: 60 to 80 percent (WMO (1986), p. 81); and CFCs: 90 to 100
percent (Hoffman and Gibbs (1988), pp. 23-27) .°

Due ta the varied sources of CH,, it is unlikely that any single
response or intervention will be capable of reducing CH, emissions by an
amount that is sufficient to stabilize concentrations. Instead,
undertaking options that result in modest reductions in each of the various
sources of CH, will likely be the preferred approach for reducing overall
CH, emissions. Nevertheless, as one of the larger anthropogenic sources,
reductions in emissions associated with livestock could be particularly
useful. For example, a 50 percent reduction target for livestock-related
emissions would provide on the order of half the reductions needed to
stabilize concentrations.

Even without making other possible reductions to stabilize CH,
concentrations, a 25 to 75 percent reduction in CH, emissions associated
with livestock would produce a significant reduction in anticipated future
global climate change from the greenhouse effect. As described in
Appendix B, such a reduction in livestock-related CH, emissions could reduce
anticipated equilibrium warming increases on the order of one to six
percent by 2100 (depending on the assumptions used).

Because no single human-related activity accounts for a large fraction
of emissions of gases that contribute to the greenhouse effect, this impact
of reducing these CH, emissions is similar to the impacts that can be
achieved by other specific technical means, such as increasing the fuel
efficiency of automobiles, reforesting large areas, or putting emissions.
fees on the use of coal, oil, and gas (see, for example, EPA (1989)). —
Additionally, unlike many of the other options for addressing global
climate change, reducing CH, emissions from ruminants produces benefits by
improving animal productivity, particularly in developing countries.

The technical feasibility and cost of achieving emissions reductions of
this magnitude from livestock remain to be quantified. However, as
described below, a range of opportunities for reducing CH, emissions from

® Of note is that although a 90 to 100 percent reduction in CFC

emissions will stabilize CFC concentrations over the long term, such
reductions will also stimulate the use of substitute compounds (such as
HCFC-22 and HFC-134a) which will also contribute to global warming.

Because the atmospheric lifetimes of the substitutes are much shorter than
the lifetimes of the CFCs, the anticipated impacts of the substitutes on
global climate will be much smaller than what the impacts of the CFCs would
ave been.


B-6

then we are indeed in a fortunate position in that the area of ruminant
animal emissions of methane may be expected to decline without incurring
any costs.

To evaluate the benefits of reducing ruminant methane emissions (in
terms of global warming), the ruminant methane emissions incorporated into
the two key EPA Report scenarios were reduced by a range of 25 percent to
75 percent. This range of reduction is taken from the workshop discussion
and is presented in the findings. The two “reduced emissions" scenarios
are also shown in Exhibit B-1.

B.4 RESULTS

Exhibit B-2 shows the resulting methane concentrations estimated for
the four scenarios.® Both the RCW and SCW scenarios show substantial
increases in methane concentrations over the current concentrations of
about 1600 ppbv. Of note is that these increases in concentrations are
influenced not only by the increasing methane emissions themselves, but
also by reductions in concentrations | of OH associated with emissions of
carbon monoxide and other compounds.’

Because reaction with OH is the principal loss mechanism for
atmospheric methane, simulated reductions in OH concentrations result in an
increased atmospheric lifetime for methane. In the RCW scenario, for
example, the lifetime for methane increases from about 9.6 years (used for
today’s lifetime) to about 11.3 years by 2100. This increased lifetime
means that a given level of methane emissions produces larger atmospheric
methane concentrations than would otherwise be anticipated. Using the ASF
without this OH-methane lifetime relationship indicates that in the absence
of the OH feedback the atmospheric abundance of methane in 2100 is
simulated to be about 3400 and 2600 ppbv in the RCW and SCW scenarios.

respectively, or about 850 ppbv and 500 ppbv lower than the amounts shown
in Exhibit B-2.

The reductions in methane concentrations associated with the emissions
reduction scenarios are significant, about 200 ppbv to 700 ppbv in each of
the scenarios by 2100. As noted above, these simulated reductions in _
future methane concentrations are influenced by the simulated changes in
future OH levels that also occur. Without the OH-methane lifetime effect,
the emissions reductions analyzed here would reduce methane levels by
smaller amounts.

® Note 1 at the end of this appendix describes the method used to

estimate methane concentrations.
7 OH concentrations are influenced in the ASF atmospheric module by

the abundances of tropospheric ozone, nitrogen oxides (NO,), methane (CH,),

carbon monoxide (CO), and emissions of non-methane hydrocarbons (NMHC).


3. STEPS FOR REDUCING METHANE EMISSIONS FROM LIVESTOCK

To reduce CH, emissions from livestock, systematic investigations are
required in two main areas: (1) emissions characterization; and (2) option
identification, evaluation, and implementation. The final objective of
these efforts is the specification of a series of near-term and long-term
options for reducing CH, emissions from animal management systems. These
options could then be examined in conjunction with options for reducing
emissions from other sources to identify a cost-effective approach for
reducing CH, emissions globally. Each of the two areas of investigation is
discussed in turn. .

3.1 IMPROVED EMISSIONS CHARACTERIZATION

Emissions rates from various animals and animal management practices
must be better characterized. Improved emissions estimates are needed in
order to: assess anticipated changes in emissions over time; identify the
areas where emissions reductions efforts would be most promising; and
evaluate the emissions reductions that can be achieved with various.
options.

In order to improve estimates as efficiently as possible, investigations
should be targeted at the key areas of inadequate data. Several areas that
have been identified are summarized in Exhibit 3-1 and are described below.

CHARACTERIZE THE ANIMAL POPULATIONS

The population of managed ruminants throughout the world is reported by
the Food and Agriculture Organization (FAO) of the United Nations based on
reports to FAO from individual countries. These data are important for
estimating CH, emissions. The accuracy of these data, in-particular in
developing countries in Africa and Asia, remain to be examined.

Additionally, to assess adequately recent and future trends in emissions
from these animals, differences and changes in animal characteristics
throughout the world must be estimated. For example, the sizes of mature
cattle differ by a factor of at least 2 to 3 between developed and
developing countries.TM These size differences are indicative of
differences in the amount of feed consumed by the animals. An assessment
of animal sizes, amount of feed consumed, and feed characteristics would
assist in improving estimates of global CH, emissions from animals.

44 Of note is that cattle breeds found in developing countries are not
necessarily inherently smaller; instead, cattle growth is often stunted due
to inadequate nutrition.


APPENDIX D

WORKSHOP AGENDA


38

(thereby negating the emissions reduction impacts of the program) or
decrease (thereby reinforcing the emissions reduction goal). Preferred
sets of policies that reduce emissions as well as improve the production of
animal products could potentially be identified.

3.2 OPTION IDENTIFICATION AND EVALUATION

Options for reducing emissions must be identified and evaluated. Given
the obvious importance of managed ruminants throughout the world, and their
unique ability to convert low quality inputs (e.g., agriculture byproducts
that cannot be digested by humans) into useful products, potential
technical and management options for reducing CH, emissions must be
evaluated within the context of the overall agricultural and economic
systems in which they would be implemented.

Potential options for reducing emissions should be evaluated in terms
of:

° Time frame: the period when the option may become viable, such as
near term versus long term.

° Applicability: the categories of animals for which the option may
be used to reduce emissions, such as intensively managed dairy
cows on concentrate feeds.

° Emissions Reduction: the extent to which the option would reduce
emissions.

o  Impacts_on Animal Productivity: the manner in which implementing

the option would affect the production of animal products.
° Costs: capital costs, operating costs, and other relevant costs.

° Implementation: methods of implementing the option, including any
special challenges posed, such as social constraints.

Based on an initial assessment of possible options, the most promising
alternatives should be examined and their effectiveness should be
demonstrated. Exhibit 3-3 displays a partial and preliminary assessment of
several options identified to date. These options represent a rich set of
possible ways to reduce CH, emissions, increase animal productivity, and, in
some cases, produce energy. As such, some of the opportunities for
reducing CH, emissions might in fact be economically viable in their own
right, or might have very small overall costs.

As shown in the exhibit, the options range from modifying the meat
grading system in the U.S. to changing feeding strategies in developing


BLAKE

Blake
using two

°

(1984) presents two estimates of methane emissions from animals
different methods:

Estimating CH, emissions from domestic animals based on studies by
Ritzman and Benedict (1938); and

Estimating CH, emissions from all herbivores (including insects) by
multiplying estimated total dry matter consumption of herbivorous
animals and insects by the efficiency with which the plant matter
is converted to methane.

Domestic Animals. Blake estimates methane emissions from domestic
animals (cattle, horses, sheep and goats) based on chamber measurements
made by Ritzman and Benedict (1938) on these animals. Ritzman and

Benedict’

°

s findings are summarized below:

Cattle: Respiration chamber measurements performed on various
breeds of cattle (average weight of 1400 lb (635 kg)) showed.an
average CH, production rate of 200 g CH,/day/head which was found
to be directly proportional to the body weight of the animal. The
efficiency of conversion of dry matter intake (by weight) to CH,
was 2 percent.

Horses: Respiration chamber measurements performed on two horses
(one average sized trotter, weighing 900 1b (408 kg) and a
Percheron mare weighing 1500 1b (680 kg)) showed that CH,
production in horses was dependent on the amount of feed intake
rather than the animal's body weight. The average CH, production
rates for the trotter and the Percheron were found to be 28 and =
106 g CH,/day/head, respectively. The efficiency of conversion for
horses was 0.5 percent.

Sheep and Goats: Respiration chamber measurements performed on
seven sheep and three goats showed average CH, production rates of
15.1 g CH,/day/head for sheep and 14.7 g CH,/day/head for goats.
The efficiency of conversion for both sheep and goats was 1
percent.

For his estimates, Blake adjusts Ritzman and Benedict's data in the
following manner:

°

Cattle: Blake asserts that a more representative weight for
cattle would be 1000 1b (454 kg) and suggests that even this would
probably be an upper limit value. If CH, production is directly
proportional to the weight of the animal, a 30 percent decrease in
size (from 1400 1b to 1000 1b) would result in a decrease in CH,
production rate from 200 to 140 g CH,/day/head.


34

° Have measurements been performed on an adequate set of animals and
conditions? A wide range of animal types and management practices
exist. Have sufficient measurements been performed across this
entire range to provide a basis for quantifying emissions on a
global basis?

Because indirect calorimetry experiments are time consuming and costly,
other measurement techniques should be explored. In particular, techniques
for measuring CH, emissions from animals in developing countries, and
grazing animals throughout the world need to be developed and evaluated.
For each of the major categories of animals (discussed above), an
appropriate measurement technique is required.

Atmospheric sampling to estimate fluxes of CH, may be appropriate for
evaluating emissions from an entire animal management area, such as a
feedlot or a dairy. The total emissions estimated with this technique
should be divided into those portions associated with rumen fermentation,
animal waste disposal, and other sources as appropriate. Indirect
calorimetry or other methods may be appropriate for estimating the portion
associated with rumen fermentation. Alternatively, the animals could be
removed from the management area and the measurements repeated. To verify
these measurements, it would be useful to have techniques for evaluating
emissions from waste piles, waste lagoons, and soils.}5

Methods for evaluating emissions from grazing animals and small groups
of animals (e.g., one or two cows in a rural Indian household) remain to be
developed. One .option that may prove useful is to collect air samples near
individual animals over an extended period of time. In order to estimate ©
rates of CH, emissions from the animal, a method is required to adjust these
air samples for meteorological conditions. The details of such an approach
remain to be developed. ?®

45 as described in the previous section, CH, emissions have been
measured from waste lagoons. The appropriateness of these methods for
characterizing the range of animal waste management practices remains to be
defined.
© one promising method for measuring CH, emissions rates from
individual animals was suggested at the workshop. The approach, involving
the use of tracers to estimate flux rates from animals, would allow CH, and
carbon dioxide emissions rates to be measured inexpensively for individual
animals without the need to isolate the animals (i.e., without the use of a
calorimetry chamber.) Such an approach, if it proves viable, will allow
numerous CH, emissions estimates to be developed for types of animals for
which estimates are not currently available (e.g., grazing animals and
animals in developing countries). The details of the approach are
currently under development, and will be presented in subsequent reports.


A-16
A.3 REFERENCES

Baldwin, R.L. and M.J. Allison, "Rumen Metabolism," Journal of Animal
Science, Vol. 57, 1983, pp. 461-477.

“"Bolle, H.-J., W. Seiler, and B. Bolin, "Other Greenhouse Gases and
Aerosols. Assessing Their Role for Atmospheric Radiative Transfer," The

Greenhouse Effect, Climatic Change, and Ecosystems, B. Bolin, B.R. Doos, J.
Jager, and R.A. Warrick, eds., John Wiley & Sons, New York, 1986, pp. 157-

203.

Blake, D.R., Increa: Co ation of Atmospheric Methane, 1979-1983,
PhD Thesis, University of California, Irvine, 1984, pp. 44-48.

Blaxter, K.L. and J.L. Clapperton, "Prediction of the Amount of Methane

Produced by Ruminants," British Journal of Nutrition, Vol. 19, 1965, pp.
$11-522.

Crutzen, P.J., I. Aselmann, and W. Seiler, "Methane Production by Domestic
Animals, Wild Ruminants, Other Herbivorous Fauna, and Humans," Tellus, 38B,
1986, pp. 271-284.

Ehhalt, D.H., "The Atmospheric Cycle of Methane," Tellus, Vol. 26, 1974,
pp. 58-70.

Ensminger, M.E., Beef Cattle Science, The Interstate Printers & Publishers,
Inc.: ‘Danville, Illinois, 1987.

Ensminger, M.E., The Stockman’s Handbook, The Interstate Printers &
Publishers, Inc.: Danville, Illinois, 1983.

FAO, FAQ Production Yearbook, Food and Agriculture Organization of the
United Nations, Rome, selected years.

Hudson, R.D. and E.I. Reed, The Stratosphere; Present and Future, NASA Ref.
1049, 1979, p. 432.

Hutchinson, G.E., "Circular Casual Systems in Ecology," Annals of New York
Academy of Science, Vol. 50, 1948, p. 221.

Khalil, M.A.K. and R.A. Rasmussen, "Sources, Sinks, and Seasonal Cycles of

Atmospheric Methane," Journal of Geophysical Research, Vol. 88, 1983, pp.
5131-5144.

Koyama, T., "Gaseous Metabolism in Lake Sediments and Paddy Soils and the
Production of Atmospheric Methane and Hydrogen," Journal of Geophysical
Research, Vol. 68, 1963, pp. 3971-3973.


METHANE EMISSIONS FROM RUMINANTS

FEBRUARY 27-28, 1989
PALM SPRINGS, CALIFORNIA

WORKSHOP AGENDA

SESSION 1: FEBRUARY 27, 1989

LOCATION: GARDEN ROOM, SPA HOTEL AND MINERAL SPRINGS
8:30am Coffee, juice, and breakfast rolls

9:00am - 9:15am Welcome and Announcements, Michael Gibbs, ICF

INTRODUCTION AND BACKGROUND

9:15am - 9:30am Workshop Objectives, John S. Hoffman, EPA
9:30am - 9:45am Methane in the Atmosphere, Don Blake, U.C. Irvine
9:45am - 10:00am Overview of Methane from Ruminants and Key Workshop

Questions, Michael Gibbs, ICF
10:00am - 10:30am Discussion

SOURCES OF METHANE EMISSIONS

10:30am - 10:50am Indirect Calorimetry Measurements, Don Johnson, Colorado
State University

10:50am - 11:10am Rumen Processes and Models, Lee Baldwin, U.C. Davis

11:10am - 12:15pm Discussion

12:15pm - 1:00pm Lunch Brought In

1:00pm - 1:15pm Waste Fermentation as a Source of Methane,

LM. (Mac) Safley, North Carolina State University

1:15pm - 2:00pm Discussion

February 23, 1989


44

countries. These, and additional options must be described more completely
and evaluated to identify the most cost effective measures for reducing
emissions.

Of particular importance is identifying and involving the institutions
and organizations that could play a role in evaluating and implementing the
various options. Such organization would include government agencies
(e.g., the Agriculture Research Service of the U.S. Department of
Agriculture), universities, and private companies (e.g., those producing
ionophores and other feed additives). Major organizations that influence
agriculture practices in developing countries include:

° United Nations (e.g., through the Food and Agriculture
Organization and other programs) ;

° World Bank and other development banks (e.g., as a funding
source);

° Consultative Group on International Agricultural Research (e.g.,
through the International Livestock Center for Africa (ILCA), and
the International Laboratory for Research on Animal Diseases
(TLRAD) )

° Winrock International, a private philanthropic non-profit
organization providing technical assistance worldwide;

° Agricultural Cooperative Development International, focused on
assisting and developing agricultural cooperatives worldwide;

° Volunteer International Technical Assistance, focused on providing
technical agricultural assistance worldwide; and

° Programs of various national governments, such as the U.S. Agency
for International Development (AID).

Coordination among these and other key institutions is required to
ensure the timely development of options for reducing CH, emissions. The
creation of an ad hoc working group for communication of ongoing and
planned activities and tracking progress is planned.


Page 6 of Note 1 to Appendix B

percent of the benefits in terms of reduced greenhouse impacts. This
estimate of the T-0, impact is uncertain and could be larger or smaller.
The total impact of the reduction in methane emissions from ruminant
animals is the sum of the change in the equilibrium temperature change
associated directly with methane (equation 4) and associated with T-0,
(equation 8).


7
EXHIBIT 1-2

RECENTLY-MEASURED INCREASES IN ATMOSPHERIC METHANE

a

CH, (ppmvy)
a

VS

1978 79 80 81 82 83 84 8S 86 87 88
Year

Source: Blake, D.R. and F.S. Rowland, “Continuing Worldwide Increase

in Tropospheric Methane, 1978 to 1987," Science, March 4,
1988.

EXHIBIT 1-3

ATMOSPHERIC METHANE FOR THE PAST 1000 YEARS

1800
1600
= {
1200 a4
E100 o
x 00 os aa te 8,
. py
wo] sat eeteree aoa
400
200
°
-1000 -800 -800 400 -200 C)
Time Before Present
Source: Khalil, M.A.K., and R.A. Rasmussen, “Trends of Atmospheric
Methane: Past, Present, and Future," in: Proceedings of the
id e: , Brussels,

Belgium, November 1986.


EXHIBIT

EXHIBIT

EXHIBIT

EXHIBIT

EXHIBIT

EXHIBIT

EXHIBIT

EXHIBIT

EXHIBIT
EXHIBIT

EXHIBIT

EXHIBIT

1-1
1-2
1-3
1-4
1-5

1-6

2-1

2-3
3-1

3-2

3-3

LIST OF EXHIBITS

GLOBAL LIVESTOCK POPULATION ESTIMATES .

RECENTLY-MEASURED INCREASES IN ATMOSPHERIC METHANE

ATMOSPHERIC METHANE FOR THE PAST 1000 YEARS

RELATIONSHIP AMONG CH,, CO, OH, AND 0,

ESTIMATES OF METHANE EMISSIONS

METHANE IS AN IMPORTANT CONTRIBUTOR TO THE GREENHOUSE

EFFECT ..........

METHANE YIELD AS A FUNCTION OF DIGESTIBILITY AND LEVEL

OF ENERGY INTAKE

ANNUAL METHANE EMISSIONS FOR COMBINATIONS OF FEED

INTAKE AND DIGESTIBILITY LEVELS .

MILK PRODUCTION PER DAIRY COW PER YEAR IN THE U.S.

STEPS FOR IMPROVING EMISSIONS ESTIMATES

10

13

18

20
27

32

POSSIBLE FRAMEWORK FOR A LIVESTOCK-METHANE ASSESSMENT

MODEL...

PARTIAL AND PRELIMINARY IDENTIFICATION AND EVALUATION

OF CH, EMISSIONS REDUCTION OPTIONS

37

39:


41

EXHIBIT 3-3

PARTIAL AND PRELIMINARY IDENTIFICATION AND
EVALUATION OF CH, EMISSIONS REDUCTION OPTIONS

EMISSIONS REDUCTION
OPTION

(continued)

COMMENTS

Near Term Options (continued)

Modify feeding
strategies in
developing countries
(continued)

6. Reduce CH, emissions
from animal wastes.

reductions may be achieved through increases in
animal productivity (e.g., milk yield) and
reproductive efficiency (e.g., reduced inter-
calving interval). Level of emissions reductions
remains to be quantified and demonstrated.
Molasses/urea blocks may be appropriate
supplements, or chicken litter. Domestic
supplement manufacturing capability should.be
promoted.

This alternative is applicable to wastes currently
disposed of in lagoons or other anaerobic
environments. Capturing CH, emissions (e.g., for
energy) would significantly reduce emissions from
this source. Efforts are currently under way to
develop techniques for harvesting CH, from
anaerobic waste lagoons. These techniques involve
covering the lagoons with plastic covers and using
the CH, to produce electricity for use on site or.
for sale to the electric power grid. Digesters to
produce and contain CH, are also under development
and in use in the U.S. and elsewhere.

Integrated animal waste recycling facilities are
currently under development that not only produce
and capture CH, in digesters, but also use the
carbon dioxide emissions produced from burning the
CH, to "fertilize" plant growth in greenhouses
and/or algae growth in ponds. The plant and algae
products can then be marketed or used as animal
feeds on site. The electric power produced by the
system (some of which can be sold to the power
grid) replaces the need to burn other fossil fuels.

Direct burning of wastes (i.e., for energy) is also
a current waste management practice, although local
air quality impacts must also be considered.


B-5

because per capita income growth is larger in that scenario.
Because of anticipated increases in consumption per capita, one
would expect that methane emissions from ruminant animals could
increase faster than the rate of growth of population, in
particular in the RCW scenario.

° Technology. Over time one would expect that the technology for
producing animal products will change. In particular,
significant advances may be anticipated in developing countries.
In fact, such changes may be required in order for the
anticipated future demand for animal products to be met in these
regions. The question is whether such advances will
significantly reduce the level of methane emissions that may be
produced per amount of animal product produced. If the ratio of
methane per amount of product produced does not change
significantly, then methane emissions from ruminant animals will
increase due to both population increases and increased demand

per capita.

The likelihood of significant reductions in methane emissions per
amount of product produced, tion that

not taken specifically to reduce such emissions, seems remote.

In particular, if production increases in developing countries,
the animals may be expected to be on forage-type diets, which may
produce more methane per amount of product than the animals on
grain-supplemented diets in the U.S. If animals are managed
intensively in the future to increase productivity in developing
countries, methane emissions from wastes could become more
important if the wastes are decomposed anaerobically (e.g., in
lagoons). Additionally, some of the most promising technologies
for increasing animal productivity (e.g., the use of bovine
growth hormone to stimulate milk production) has only a modest
impact on methane emissions per amount of milk produced.

Although the number of animals needed to produce milk may
decline, the amount of methane produced per amount of milk
produced changes only slightly. Finally, if existing techniques
for promoting animal productivity are abandoned (e.g., the use of
growth hormones) then methane emissions per amount of product
produced may increase for a period of time in some areas.

Given these three observations, the scenarios of methane emissions from
ruminant-animals in the two scenarios in the EPA Report seem plausible.
Certainly, alternative scenarios are also possible, including scenarios
that presume significant reductions in methane emissions per amount of
product produced due to changes in technology. Of note is that efforts are
currently under way to identify and evaluate such technologies, so that
they may be factored in to future climate change policy analyses by EPA and
others. If such technologies may reasonably be anticipated-to be
implemented quickly over time due to the economic benefits that they
produce in their own right (without reference to climate change at all).


NOTE 1 TO APPENDIX B

METHODS USED TO ESTIMATE METHANE CONCENTRATIONS AND
EQUILIBRIUM TEMPERATURE CHANGE

The Atmospheric Stabilization Framework (ASF) developed by EPA was used
to estimate future methane concentrations and equilibrium temperature
change presented in this appendix. The ASF, as well as the bases for the
scenarios used in the ASF, are described more fully in EPA (1989) (the EPA
Report). The EPA Report summarizes the working of the atmospheric
composition and temperature module of the ASF as follows: .

The atmospheric composition model was developed for this
study (Prather, 1988). It estimates changes in the concentrations
of key atmospheric constituents and the global radiation balance
based on the emissions/uptake projected by the other models.
Perturbations to atmospheric chemistry are incorporated based on
first-order (and occasionally second-order) relationships derived
from more process-based chemical models and observations. The
model is essentially zero-dimensional, but it does distinguish
between the northern hemisphere, southern hemisphere, troposphere,
and stratosphere. Global surface temperature change is calculated
based on the radiative forcing of the greenhouse gases derived from
Lacis et al. (1981) and Ramanathan et al..(1985) coupled to heat
uptake by the ocean model using a specified climate sensitivity
parameter. This sensitivity parameter is set to yield a global
equilibrium temperature increase of 2 or 4°C when C02 concentration
is doubled, reflecting a central estimate of the range of
uncertainty ...7

This note summarizes the methods used in the ASF to estimate niethane
concentrations and equilibrium temperature change associated with methane.
A more detailed description is contained in Prather (1988) and the EPA
Report.

1 U.S. EPA, "Policy Options for Stabilizing Global Climate," Draft
Report to Congress, February 1989.

2 The sources cited in this paragraph include:

Prather, Michael J., ‘sessment Mode ‘°: ic OS
NASA Conference Publication, 1988.

Lacis, A. et al., "Greenhouse effect of trace gases, 1970-1980,"
Geophysical Research Letters, 8:1035-1038, 1981.

Ramanathan, V. et al., "Trace gas trends and their potential role in
climate change," Journal of Geophysical Research, 90:5547-5566, 1985.


ws

EPA

United States Ottice of Air and Radiation EPA 400/1-89/002
Environmental Protection Washington D.C. 20460 August 1989

Agency

Reducing Methane Emissions
From Livestock: Opportunities
and Issues

Printed on Recycled Paper


METHANE EMISSIONS FROM RUMINANTS

FEBRUARY 27-28, 1989
PALM SPRINGS, CALIFORNIA

Curtis Bailey
CSRS

USDA

Room 330

Aerospace Building
Washington, D.C. 20251-2200
(202) 382-1534

Lee Baldwin

Department of Animal Science
University of California, Davis
Davis, CA 95616

(916) 752-1250

Donald Blake
Department of Chemistry
University of California
Irvine, CA 92717

(714) 856-5011

Lauretta Burke

U.S. EPA

Room 3009 PM 220

401 M Street, SW
Washington, D.C. 20460
(202) 475-6632

Dan Dudek

Environmental Defense Fund
257 Park Avenue South

New York, NY 10010

(212) 505-2100

Jim Ellis

Natural Resources Ecology Lab
Colorado State University

Fort Collins, CO 80523

(303) 491-1643

WORKSHOP ATTENDEES

Jim Fadel

Department of Animal Science
University of California, Davis
Davis, CA 95616

(916) 752-1250

Michael Gibbs

ICF Consulting Associates, Inc.
10 Universal City Plaza

Suite 2400

Universal City, CA 91608-1097
(818) 509-7150

Keith Gomes

California Milk Producers
11709 E. Artesia Bivd
Artesia, CA 90701

(213) 865-1291

Thomas J. Goreau

324 North Bedford Road
Chappaqua, NY 10514
(914) 238-8768

Champ Gross

CALF News

7252 Rammet Ave

Suite 205B

Canoga Park, CA 91303
(818) 346-2068

Juan Guererro

UC Cooperative Extension Service
Courthouse :

938 9th Street

El Centro, CA 92243

(619) 339-4250


TABLE OF .CONTENTS

Page
PROLOGUE . 1. 1 ew ee ee ee ee 1
FINDINGS 2. 1 1 1 1 we ee ee ee ee 1
1. INTRODUCTION . 2 2... ee ee ee 4
1.1 SUMMARY .. ee ee 4
1.2 THE INCREASING ABUNDANCE OF ATMOSPHERIC “METHANE | wee eee 6
CAUSES OF METHANE INCREASES . . . we eee 6
OZONE EFFECTS IN THE STRATOSPHERE AND ‘TROPOSPHERE woe ee ee 11
GLOBAL CLIMATE CHANGE IMPACTS . . . we ee 12
1.3 STABILIZING THE ABUNDANCE OF ATMOSPHERIC METHANE ee ee 12
2. OVERVIEW OF METHANE FROM LIVESTOCK ........+ +e. e ee 16
2.1 SOURCES OF METHANE EMISSIONS... ... 2... eee ee eee 16
METHANOGENESIS WITHIN THE RUMEN... .... 1... ee eee 16.
MANURE AS A SOURCE OF METHANE EMISSIONS ........... 22
2.2 GLOBAL METHANE EMISSIONS FROM RUMINANTS .........-.- 24.
2.3. TRENDS IN SUPPLY AND DEMAND ... . er 25
TRENDS IN SUPPLY ...... 2... ee eee ee ee ee ee 25
TRENDS IN DEMAND... 1. 1 1 eee ee ee ee ee ee 29
3. STEPS. FOR REDUCING METHANE EMISSIONS FROM LIVESTOCK ..... . 31,
3.1 IMPROVED EMISSIONS CHARACTERIZATION .........+..-4.4. 31
CHARACTERIZE THE ANIMAL POPULATIONS . . . ce ee 31
DEVELOP AND EVALUATE MEASUREMENT TECHNIQUES se ee ee ew 33
PERFORM CH, EMISSIONS MEASUREMENTS .. . we eee 35
MODEL DEVELOPMENT: EMISSIONS AND ANIMAL MANAGEMENT wee 35
3.2 OPTION IDENTIFICATION AND EVALUATION... .......-4- 38
4. EPA OFFICE OF AIR AND RADIATION PROGRAM PLAN ......... 45
REFERENCES 2... 1 1 we ee ee ee ee ee ee 48

Appendix A: Global Methane Emissions from Ruminants

Appendix B: Impact of Reducing Livestock Methane Emissions on Global
Warming from the Greenhouse Effect

Appendix C: Crutzen, P.J., I. Aselmann, and W. Seiler,"Methane Production
by Domestic Animals, Wild Ruminants, Other Herbivorous Fauna,
and Humans," Tellus, 1986, pp. 271-284.

Appendix D: Workshop Agenda

Appendix E: List of Workshop Attendees


WORKSHOP ATTENDEES

Robert Hespell

USDA Northern Regional Research Center

1815 North University
Peoria, IL 61604
(309) 685-4011

John Hoffman

U.S. EPA

Office of Air and Radiation
401 M Street SW

Room 739 West Tower
Washington, D.C. 20460
(202) 382-4036

Don Johnson

Colorado State University
209 Animal Science Building
Ft. Collins, CO 80521
(303) 491-6672

Aslam Khalil

Oregon Graduate Center
19600 N.W. Von Newman Dr.
Beverton, OR 97006-1999
(503) 690-1078

* Ron Leng
Department of Biochemistry,
Microbiology & Nutrition
The University of New England
Armidale, N.S.W. Australia 2351

Lisa Lewis

ICF Technology

10 Universal City Plaza
Suite.2400

Universal City, CA 91608-1097
(818) 509-7150

Bob Lott

Gas Research Institute
8600 West Bryn Mawr Ave.
Chicago, IL 60631

(312) 399-8227

(Continued)

Richard Neal

National Cattlemen's Association
1301 Pennsylvania Ave., NW
Suite 300

Washington, D.C. 20004

(202) 347-0228

John A. Patterson

Department of Animal Sciences ,
Purdue University

West Lafayette, IN 47907

(317) 494-4826

R.A. Rasmussen

Oregon Graduate Center
19600 N.W. Von Newman Dr.
Beverton, OR 97006-1999
(503) 690-1078

Joseph Robinson

The Upjohn Company
7922-190-MR
Kalamazoo, MI 49001
(616) 323-4000

Robert Roffler

Department of Animal Science
University of Idaho

Moscow, ID 83843

(208) 885-7173

Pat Russell

Department of Chemistry
University of California
Irvine, CA 92717

(714) 856-5011

LM. (Mac) Safley

Biological and Agricultural Engineering
North Carolina State University

Box 7625

Raleigh, NC 27695-7625

(919) 737-2694


29

TRENDS IN DEMAND

The demand for milk and meat products are the primary factors driving
the sizes of animal populations in developed countries. In developing
countries, the needs for draft power and a mechanism for storing wealth are
also important factors.

The per capita consumption of animal products in most developed nations
has stabilized in the past 10 to 20 years in terms of calories, protein,
and calcium consumed (FAO (1986)). In some areas, for example the U.S.,
per capita poultry consumption has increased while per capita red meat
consumption has remained relatively constant (American Meat Institute
(1987)).

Future trends in demand for animal products in developed nations will
likely be driven by changes in the size and age structure of the population
and by changes in consumer preferences. For example, demand for low-
cholesterol and low-fat products are leading to developments of low-fat
meat and dairy products (Dunkley (1982)). Changes in the complex demand
for milk products (currently driven primarily by the demand for milk fat
for use in milk products like cheese and ice cream) could influence
breeding and feeding strategies, possibly affecting CH, emissions as well.

Demand for low-fat meat could influence the feeding strategies and
slaughter ages of feed-lot-finished cattle. Similarly, concerns over
antibiotics (used in therapeutic treatments of animals in feedlots) could
also influence feedlot finishing practices. Shifts to range- and pasture-
fed beef (if they occur) could increase feed requirements (e.g., ionophore
feed supplements are more difficult to administer to range-fed animals),
possibly increasing total CH, emissions.

Consumer concerns over hormone use could also affect the manner in which
meat and milk are produced, and hence, CH, emissions. The recent EEC ban on
the use of steroid implants is an example. Such concerns could also affect
the potential use of bovine growth hormone and the realization of its
benefits in terms of CH, emissions reductions (see above).

Increasing population and income among developing countries point to
increasing demand for animal products in these areas. In general, stage of
development has been found to be a good indicator of food consumption
patterns (Rojko et al. (1978)). Consequently, as development proceeds and
as incomes continue to rise in developing countries, meat and dairy product
production and consumption may be anticipated to increase as well. The
extent of these increases depends not only on rates of development, but on
regional and local tastes and customs as well.

Given that extensive animal management systems predominate in developing
countries, increasing demands for meat and milk products are expected to be
translated into increasing populations of animals. Increases in animal


Methane production by domestic animals, wild ruminants,
other herbivorous fauna, and humans

By PAUL J. CRUTZEN. INGO ASELMANN and WOLFGANG SEILER,® Max-Planck-Instuute
for Chemsiry. Department of Air Chemusjry, P.O. Box 3060, D-6500 Mainz. F.R. Germany

(Manuscript received October 22. 1985: in final form May 30. 1986)

ABSTRACT

A detatied assessment of global methane production through enteric fermentation by domestic
animais and humans is presented. Measured relations between feed intake and methane yields
for animal species are combined with population statistics to deduce a current yearly input of
methane to the atmosphere of 74 Tg (1 Tg = 10'? g), with an uncertainty of about 15%. OF
this, cattle contmbute about 74%. Buffalos and sheep each account for 8-9%, and the
femainder stems from camels, mules and asses. pigs, and horses. Human CH, production is
probably less than | Tg per year. The mean annual increase in CH, emission from domestic’
animals and humans over the past 20 years has been 0.6 Tg, or 0.75% per year. Population
figures on wild ruminants are so uncertain that calculated CH, emissions from this source may
tange between 2 Tg and 6 Tg per year. Current CH, emission by domestic and wild animals 1s
estimated to be about 78 Tg, representing 15-25% of the total CH, released to the atmosphere
(rom all sources. The likely CH, production from domestic animals in 1890 was about 17 Tg,
$o that this source has increased by a factor of 4.4.

A brief tentative discussion is also given on the potential CH, production by other

herbivorous fauna. especially insects. Their total CH, production probably does not exceed 30
Tg annually. .

1. Introduction

Methane plays a large role in the photochemis-
try of the background atmosphere. It is produced
and released by various biological processes and
is mainly decomposed in the troposphere by
reaction with hydroxyl radicals (OH). This reac-
tion initiates complicated reaction pathways
leading to the formation of various intermediates
that influence the atmosphenc concentrations of
ozone and hydroxyl (McConnell et al., 1971:
Levy,-1971: Crutzen. 1973). The hydroxyl radical.
which is present in the atmosphere at an average
volume mixing ratio of only 2 x 10", is primar-
ily responsible for the breakdown of natural and
anthropogenic trace gases in the atmosphere. As
atmospheric methane has been increasing by over

—_——.

“Current address: Fraunhofer-Institute for Atmo-
sphenc Environmental Research. Kreuzeckbahnstrasse
19, D-8100 Garmisch-Partenkirchen. -

Tellus 38B (1986), 34

\% per year over the past decade (Rasmussen
and Khalil, 1984; Blake, 1984: Seiler, 1984),
changes in the background photochemistry of the
atmosphere can be expected. Crutzen (1986) has
postulated that on the whole. global OH concen-
trations are decreasing (especially outside the
northern mid-latitude zone) and ozone concentra-
tions increasing (especially in northern mid-lat-
tudes and in the upper troposphere).

Methane production by ruminants has been
estimated in the past by several authors. The
earliest figures on world-wide production rates
were published by Hutchinson (1949), who esu-
mated the CH, emission by large herbivores to
be 45 Tgjyear for the 1940's. Ehhalt (1974)
calculated a global CH, production of 100 Tg
CH, for 1970 from domestic ruminants. This
would constitute 20-35% of the total input of
methane to the atmosphere, which is now esu-
mated by various authors to be in the range 300-
500 Tgryear (Khalil and Rasmussen, 1983:


Page 3 of Note 1 to Appendix B

The implication of this lifetime feedback is that as simulated temperatures
change and as OH levels change (due to changes in the abundance of methane,
carbon dioxide, ozone, nitrogen oxides, and non-methane hydrocarbons, and
changes in tropospheric temperature), the lifetime of methane may increase
or decrease. In the Rapidly Changing World (RCW) scenario presented in the
EPA Report, OH levels are simulated to decline, leading to an increased
lifetime for methane. However, tropospheric temperatures increase, thereby
reducing the lifetime of methane. The net effect is that by 2050 in the
RCW scenario the methane lifetime increases by about 14 percent to about
10.9 years; by 2100 the increase is to about 11.3 years.

These simulated increases in the methane lifetime cause the estimates
of methane concentrations to be larger than they would be in the absence of
the increases in the lifetime.

EQUILIBRIUM TEMPERATURE CHANGE

The impacts of increases in methane concentrations are estimated in
terms of an “equilibrium temperature change." This value describes the
manner in which the composition of the atmosphere has changed the radiative
properties of the atmosphere. For purposes of evaluating the benefits of
reducing methane emissions from ruminant animals, the anticipated impacts
that lower methane concentrations (due to lower methane emissicns) will
have on the radiative properties of the atmosphere must be assessed. In
addition, however, the impacts that the lower methane emissions and
concentrations have on the abundance of other radiatively important trace
gases must also be evaluated.

In the ASF, reductions in methane emissions from ruminant animals not
only reduce the future anticipated methane concentrations, but also have
the following impacts:

° Reduce the level of OH reductions anticipated in the future
(i.e., OH levels are higher than would otherwise- be anticipated).
Increases in OH tend to reduce the atmospheric lifetimes of other
trace gases with destruction processes dominated by OH, including
carbon monoxide (CO), methyl chloroform (MC), non-methane
hydrocarbons (NMHCs), and partially-halogenated
chlorofluorocarbons (HCFCs). These.shorter lifetimes tend to
reduce their future concentrations slightly. Because MC and
HCFCs contribute to global warming, their shorter lifetimes and
consequent lower concentrations reduce their global warming

impacts.

° Reduce the level of tropospheric ozone (T-0;) increases
anticipated in the future (i.e., T-0, levels are lower than would
otherwise be anticipated). T-03; is influenced directly by methane


11

Despite the various uncertainties regarding both sources and sinks, it
is clear from atmospheric measurements and ice core analyses that the
atmospheric abundance of CH, is increasing. Additional research and
analysis is ongoing to improve our assessment of the sources and sinks of
CH,,- including: atmospheric monitoring to evaluate CH, trends by latitude
and CH, isotope ratios; measurements of the emissions from key sources,
including tundra in the Arctic, rice paddies in Asia, ruminants, and
others.

OZONE EFFECTS IN THE STRATOSPHERE AND TROPOSPHERE

Current atmospheric models indicate that increases in the abundance of
CH, may increase the abundance of tropospheric and stratospheric ozone (WMO
(1986), pp. 730-732). Increases in tropospheric ozone, an important
component of urban "smog," are considered a threat to human health, crops,
forests, ecosystems and materials (EPA (1987), p. 14-3). The extent of
increases in tropospheric ozone due to CH, depends on the tropospheric
abundance of nitrogen oxide (NO). As shown above in Exhibit 1-4, CH,
oxidation leads to an increase in tropospheric ozone abundance when in the
presence of relatively high levels of NO, as are found over the northern
continents, including North America (WMO (1986), pp. 730-731, and Crutzen
(1987), pp. 111-114).

Based on current models, therefore, increasing levels of CH, are
expected to worsen tropospheric ozone levels in both urban and rural
locations in the U.S. Because the current understanding of the link
between the levels of CH, and tropospheric ozone is based on models of
complex trvpospheric chemistry, the quantitative relationship between CH,
and tropospheric ozone remains uncertain.

. Stratospheric ozone forms the Earth’s shield against harmful solar
ultraviolet radiation. Conventional wisdom has been that in the
stratosphere CH, may help to protect ozone by interfering with its catalytic
destruction by chlorine and nitrogen oxides (NO,) (WMO (1986), pp. 731-732).
Thus, it has been thought that such stratospheric ozone increases
associated with CH, could help to offset stratospheric ozone depletion due
to chlorofluorocarbon (CFC) emissions, thereby reducing the risks to human
health and the environment (EPA (1987), p. 18-41).

However, it has been suggested recently that CH, may in fact promote
stratospheric ozone depletion (Blake and Rowland (1988)). The water vapor
that is added to the stratosphere when CH, is oxidized may provide surfaces
for heterogeneous reactions that destroy ozone to take place. These
reactions, which have been implicated in the polar’ ozone losses that are
currently observed (i.e., the Antarctic "Ozone Hole"), would lead to
reductions in stratospheric ozone that outweigh the increases currently
anticipated to be associated with increasing levels of CH,. Consequently,
the impact of rising CH, levels on stratospheric ozone now is less of a
consensus.


A-3
EXHIBIT A-1

ENERGY UTILIZATION IN RUMINANTS

GROSS ENERGY

DIGESTIBLE ENERGY
(Roughly comparable to TDN)

,
a

Urinary and
Combustible
Energy METABOLIZABLE ENERGY

Heat Increment
NET ENERGY
Net Energy Maintenance Net Energy Production

Source: Ensminger, M.E., The Stockman’s Handbook, The Interstate
. Printers & Publishers, Inc.: Danville, Illinois, 1983, p.
245.


278

Table 3. CH, proauction by wild anumais in the Serencen

P J. CRUTZEN, I. ASELMANN AND W SEILER

Mean couy Gross cnerey CH, production CH, Production
Population wei)ent imtake Per individual —totat-
Species (© 10°] {ke} (MJ day] {kevyear} (10° kevyear}
wildebeest 72000 123 22 3 94
buffalo 10800 350 37 MM 347
Thompson's gazelle 98100 1s 3 2 2.0
giratte 1700 750 84 $0 Os
eland 2400 340 46 27 06 .
topi 5600 100 9 "W 0.6
impala 11900 40 9 $s 0.6
kongon 2100 135 2 3 03
waterbuck 300 160 26 1s 0.1
Grant's gazelle 600 40 9 $s =-
Total ruminants » 8a
zebra 240 200 uM $s 1.2
elephant 5 1725 137 6 0.13
warthog 34 45 10 1 0.03
hippopotamus 2 1000 103 17 0.03
rhinoceros 1 $20 90 1s 0.02
Total non-ruminants is
Table 4. Trends in domestic animal populations and C1, production rates
1890 192-25 19S135 1961-65, 1983
Cautie
population (10°) 310 re 1016
CH, proguction rate {ke:animat year} cs} 40.5 428
CH, proauction total (Tg-yeari " 30 33
Sheep
population {10°} $90 645 738 1007 137
CH, proauction rate (kg;animal. year] 3 S48 5.6 $9 6
CH, procuction totat (Tg year} 3 3 ry 6 -
Other domestic animals. humans etc.
CH, production total (Tg. year} 3 6 8 W 3
Total CH, proauction (Tgyearl wv 34 a2 60 “3

CH, yields from other fauna than that considered
so far couid produce substantial amounts of
methane. Ia the following. we will briefly con-
sider the possibilities.

According to Whittaker (1975). the consump-
tion of piant matter by fauna is 10-15°, of the
NPP in grasslands and 4-§°, in forest and wooc-
lands. However. only a few investigations on the
energy transter through the food webs in these
ecosystems have deen published so far. which

11975) estimated the consumption of plant m:
by small mammals. mainly voles. in the Serer:geut

to be 1.2%

‘2 Of the above-ground NPP in |
grass savanna and only 0.1°; in shores
savanna. Much more. 7.6

and 4.1°%, resoest-

$ n °
ively, is consumed by invertebrates (mainly er2ss-

hoppers). in these two grassiand sites (Bouri:

1983).

Tellus 3$B (19861, 2=


B-7

Exhibit B-3 shows the equilibrium temperature change for the scenarios .®
Both the SCW and RCW scenarios result in significant warming by 2100. The
reductions in methane emissions associated with ruminant animals reduce the
warming by about 0.1°C to 0.4°C by 2100. Of note is that the avoided
warming is driven not only by reductions in the future atmospheric
abundance of methane, but also by reductions in the anticipated increase in
tropospheric ozone (03). By reducing methane emissions, the ASF indicates
that a portion of future increases in 0, can also be avoided. Because 0, is
a greenhouse gas, part of the warming avoided by reducing methane emissions
is accounted for by this 0, relationship. The ASF indicates that about 40
percent of the avoided warming is associated with this 0, effect. However,
this estimate is very uncertain and could be larger or smaller.

As shown in Exhibit B-4, the avoided warming in the RCW scenario
amounts to about 1.7 to 5.3 percent of the warming by 2050, and about 1.1
to 3.3 percent of the warming by 2100. In the SCW scenario, the avoided
warming amounts to about 2.0 to 6.3 percent of the warming by 2050 and 2.0
to 6.1 percent by 2100. The percentages are larger in the SCW scenario
because methane emissions from ruminant animals are a larger portion of the
total anticipated warming in this scenario.

To put the benefits of these emissions reductions in perspective it is
useful to examine other methods of reducing global warming. Exhibit B-5
shows estimates of reductions in warming that may be achieved by specific
technological means in the RCW. As shown in the exhibit, measures for
reducing global warming have relatively small impacts individually. The.
impacts of reducing methane emissions from ruminant animals presented above
are within the range of impacts achieved by these measures.

B.5 CONCLUSIONS

This analysis indicates that reducing methane emissions from ruminant
animals will have an impact on future global warming. Additionally, the
analysis indicates that the benefits achieved from these emissions
reductions are comparable to other measures contemplated for avoiding
future global warming. Consequently, understanding options for reducing
methane emissions from ruminants should be pursued as part of an overall
investigation into alternatives for reducing future global warming and its
impacts.

® These equilibrium temperature change estimates are based on a
climate sensitivity of 4°C for a doubling in carbon dioxide concentrations
from pre-industrial levels. The sensitivity of the earth's climate to
changing atmospheric properties is uncertain, and a range of 1.5 to 4.5°C
has been recognized as an appropriate range of uncertainty. Recent
analyses indicate that biogeochemical feedbacks may push the range upward.
Note 1 at the end of this appendix presents the method used to estimate the
equilibrium temperature change.


35

As a complement to various techniques for measuring CH, emissions
directly from animals, techniques could be explored to correlate emissions
from the animal to gases produced by samples of rumen contents, and to the
population (and species) of methanogens found in the samples. By
developing such correlations, estimates of CH, emissions could be produced
using laboratory analyses of rumen contents. Such an approach, if
feasible, would greatly enhance the ability to estimate CH, emissions from
ruminants.

PERFORM CH, EMISSIONS MEASUREMENTS

Numerous measurements of CH, emissions from cattle -and sheep in
developed countries have been made using direct and indirect calorimetry
techniques. The representativeness of these measurements for the various
types of animal management practices must be assessed, and gaps in
measurements identified. For example, indirect calorimetry experiments
have been performed on lactating dairy cows and finishing steers on various
types and levels of diets. These data need to be consolidated and
evaluated. Additionally, emissions estimates from brood cows, pasture
animals, and range animals are also required.

The priorities for performing these measurements on various categories
of the animal population should be based on the importance of the category
in the overall population of animals and the availability and quality of
existing emissions data. One obvious area where additional measurements
are required is CH, emissions from animals in developing countries. There
is uncertainty regarding their rates of CH, production, in particular for
the types of diets they generally consume.

Additionally, measurements are required to improve our ‘understanding of
the variations in emissions among individual animals that (except for their
apparent CH, emissions rates) are similar, and the factors that influence .
these variations. The potential existence of host-animal traits that
influence methanogenesis by microbes in the rumen remains to be
investigated. Potential mechanisms via which such traits could influence
rates of methanogenesis (e.g., by influencing the populations of the
microbes) also are unknown at this time.

Emissions measurements from animal wastes are also clearly required.
MODEL DEVELOPMENT: EMISSIONS AND ANIMAL MANAGEMENT

By performing these various investigations, the basis of information
describing sources of CH, emissions from ruminants will be improved
considerably. These data could then be used to develop models for
quantifying emissions in various parts of the world and globally. For
example, assuming that each of the major categories of animals will be
characterized in terms of key factors affecting emissions, these categories
can be used as the basis for an emissions analysis model. The extent to


47 ‘

-- Identify and evaluate options for reducing or
recovering CH, emissions from animal wastes.

-- Identify promising long term approaches for reducing
CH, emissions and initiate investigations into these
approaches. Examples may include: developing
improved CH, inhibitors; identifying animal traits
that influence methanogenesis by microbes in the
rumen; modifying feed characteristics to increase
digestibility or reduce methanogenesis.

These major program elements should be implemented within the coming
year. For each, a more detailed plan will be developed that includes:
detailed descriptions of the proposed investigations; schedule for
undertaking the investigations, and approximate level of resources that is
appropriate; identification of individuals and institutions that could
perform the investigations; identification of appropriate funding sources
(e.g., EPA, Department of Agriculture (through CSRS or ARS), NASA, NSF,
and others); and methods for obtaining funding.

As soon as practicable, validations and demonstrations of the various
CH, emissions reduction alternatives will be organized. Finally,
alternatives for implementing these emissions reduction methods will be
developed through national and international institutions and international
‘forums.


A-2

Allison (1983), p. 469). Instead, the conversion of hydrogen (H2) or
formate and CO, (produced by other fermentative bacteria) is believed to be
the primary mechanism by which methanogenic bacteria produce CH, in
ruminants.

As shown in Exhibit A-1, on a “whole-animal" basis, the manner in which
the energy intake of an animal is utilized can be defined as follows:

° gross energy is the total energy intake by the animal, where the
energy content of the feed is defined in terms of its total
combustible energy (i.e., the energy it releases when it is
burned) ;

° digestible energy is the gross energy intake minus the energy
eliminated in feces;

° metabolizable energy is the digestible energy minus the energy
eliminated in urine and gas (CH,); and

° net energy is the metabolizable energy minus the increment of heat
produced by the animal.

Net energy is a measure of the extent to which feed contributes to the
maintenance and growth of an animal.’ The net energy received by an animal
from a diet will depend on the energy intake level of the diet‘ and the form
of the energy (i.e., the mix of feeds that comprise the diet). Some feeds
+(e.g., grains) are more "digestible" than others (e.g., hay), so that more
of the gross energy is converted to digestible energy (and subsequently,

net energy). Evaluations of alternative diets and diet formulation
techniques continue to be an important and active area of research in
animal management.

Of note is that the analysis of ruminant feeding practices in-terms of:
these energy quantities may not be appropriate for many animals in
developing countries whose diets are deficient in one or more important

3 Maintenance energy is the amount of energy that will result in no loss

or gain in total body energy. and is defined as the amount of energy
equivalent to the fasting heat production (NRC (1984), p. 3). For U.S. beef
cattle, maintenance energy requirements are estimated to be about 77
kilocalories times the animal weight in kilograms raised to the 0.75. power.
This requirement varies on the order of 3 to 14 percent for different breeds
and sex. For U.S. dairy cattle, the maintenance requirement is on the order
of 12 percent higher than for beef cattle.

“The energy intake level of a diet is often described as the ratio of
the metabolizable energy intake to the maintenance energy requirement. For
example, the level of the diet fed to lactating dairy cows in the U.S. may be
on the order of two to three times the maintenance requirement.


REFERENCES

American Meat Institute, Meat Facts, Washington, D.C., 1987.

Baldwin, R.L. and M.J. Allison, “Rumen Metabolism," rnal nit
Science, Vol. 57, 1983, pp. 461-477.

Baldwin, R.L., J.H.M. Thornley, and D.E. Beever, "Metabolism of the
Lactating Cow. II. Digestive Elements of a Mechanistic Model," Journal of

Dairy Research, Vol. 54, 1987, pp. 107-131.

Blake, D.R. and F.S. Rowland, "Continuing Worldwide Increase in
Tropospheric Methane, 1978 to 1987," Science, March 4, 1988.

Blaxter, K.L. and J.L. Clapperton, "Prediction of the Amount of Methane

Produced by Ruminants," British Journal of ‘Nutrition, Vol. 19, 1965, pp.
511-522.

Bolle, H.-J., W. Seiler and B. Bolin, "Other Greenhouse Gases and Aerosols:
Assessing Their Role for Atmospheric Radiative Transfer," in: Bolin, B.,
B.R. Doos, B. Warrick and D. Jager (eds.), e use Ef. atic

Change and Ecosystems, John Wiley & Sons: New York, 1986.

Crutzen, P.J., I. Aselmann, and W. Seiler, "Methane Production by Domestic
Animals, wila’ Ruminants, Other Herbivorous Fauna, and Humans," Tellus, 38B,
. 1986, pp. 271-284. :

Crutzen, Paul J., "Role of the Tropics in Atmospheric Chemistry," in:

Dickinson, R. (ed.), Geophysiology of Amazonia, John Wiley & Sons: New
York, 1987.

Dunkley, W.L., "Reducing Fat in Milk and Dairy Products - Introduction,"

Journal of Dai ry Science, Vol. 65, 1982, p. 442.

Ensminger, M.E., The Stockman's Handbook, The Interstate Printers &
Publishers, Inc.: Danville, Illinois, 1983.

Ensminger, M.E., Beef Cattle Science, The Interstate Printers & Publishers,
Inc.: Danville, Illinois, 1987.

EPA, Cc tio r Stabilizing G imate, Draft Report to
Congress, EPA: Washington, D.C., 1989.

EPA, isks ace Gases That i the Stratos:
EPA: Washington, D.C., 1987.

Fallert, R., T. McGuckin, C. Betts, and G. Bruner (1987), bST and the Dairy

Industry: A National, Regional and Farm-Level Analysis, U.S. Department of

Agriculture, Washington, D.C., p. 114.


B-10

EXHIBIT B-3

SIMULATED EQUILIBRIUM TEMPERATURE CHANGE

(Degrees C)

SCENARIO 1985 2000 2025 2050 2075 2100
RAPIDLY CHANGING WORLD SCENARIO .
Base Assumptions 1.4 2.1 3.5 5.4 7.5 9.6.
25% Reduction 1.4 2.1 3.4 5.3 7.4 9.5
75% Reduction 1.4 2.0 3.2 5.1 7.2 9.3
SLOWLY CHANGING WORLD SCENARIO
Base Assumptions 1.4 2.1 3.3 4.5 5.4 6.3
25% Reduction 1.4 2.1 3.2- 4.4 5.3 6.2
75% Reduction 1.4 2.0 3.1 4.2 5.0 5.9

_ The reduction scenarios include a 25 or 75 percent reduction in methane
emissions associated with ruminant animals starting in 1990.
emissions reductions is shown for illustrative purposes.
feasibility and costs of reducing methane emissions from ruminant animals

is currently being analyzed.

These equilibrium temperature change estimates are based on a climate
sensitivity of 4°C for a doubling in carbon dioxide concentrations from

pre-industrial levels.

This range of
The technical

Source: Estimated using the Atmospheric Stabilization Framework

developed for: U.S. EPA, "Policy Options for Stabilizing Global Climate,"

Draft Report to Congress, February 1989.


APPENDIX C

“METHANE PRODUCTION BY DOMESTIC ANIMALS, WILD RUMINANTS,
OTHER HERBIVOROUS FAUNA, AND HUMANS,"

by

Crutzen, P.J., I. Aselmann, and W. Seiler

Reprduced with permission from:

Tellus, 1986, pp. 271-284.



42

EXHIBIT 3-3

PARTIAL AND PRELIMINARY IDENTIFICATION AND
EVALUATION OF CH, EMISSIONS REDUCTION OPTIONS

EMISSIONS REDUCTION
OPTION

ons

Modify feed
characteristics or
rumen processes to
increase feed
digestibility or
reduce
methanogenesis.

Develop CH,
inhibitors as feed
additives.

Improve reproductive
efficiency to reduce
brood herd
requirements.

(continued)

COMMENTS

Alternatives under consideration include
genetically engineered bacteria to pre-treat feed
or to be introduced into the rumen. Modifications
in rumen digestion could lower emissions. This
alternative is most likely to be applicable to
intensively managed animals in developed countries.

In the past, efforts have been made to identify and
develop CH, inhibitors. Although several compounds
that effectively inhibit methanogenesis in vitro
have been identified, most have not been marketed
as a CH, inhibitor due to insufficient improvement
in feed efficiency in the whole animal. LIonophore
feed additives (discussed above) have been
demonstrated to improve feed efficiency and reduce
CH, production, and are widely used in beef animals
in the U.S.

The development of new options is uncertain, and.
possibly unlikely. The CH, inhibitor would have to
provide an additional hydrogen sink assuming that
less CH, is created. Additionally, the inhibitor
would have to be acceptable from the viewpoint of
human, animal, and environmental risks.

This alternative is applicable to areas with brood
herds. In developing countries, nutritional .
management programs to increase reproductive
efficiency (e.g., toward one cow per calf per year)
may be appropriate. In all circumstances, it is
important to ensure sufficient nutrition to new
born calves to ensure survival.


ACKNOWLEDGEMENTS*

We would like to thank the many individuals who provided insights and
information that helped to produce this paper. In particular we are
grateful to those who contributed to the workshop on Methane Emissions from
Ruminants, including: Lee Baldwin, Don Blake, Jim Ellis, Bob Hespell, Don
Johnson, Ron Leng, Mac Safley, Henry Tyrrell, and Pat Zimmerman.

Additionally, we are grateful to all the reviewers who helped to improve
the paper through their comments.

* Michael Gibbs and Lisa Lewis are employed in the Universal City,
California office of ICF Incorporated.


3
WORKSHOP AGENDA (Continued)

SESSION 2: FEBRUARY 28, 1989

LOCATION: GARDEN ROOM, SPA HOTEL AND MINERAL SPRINGS
8:30am Coffee, juice, and breakfast rolls

9:00am - 9:15am Announcements, Michael Gibbs, ICF

IDENTIFYING AND EVALUATING OPTIONS FOR REDUCING
METHANE EMISSIONS FROM RUMINANTS

9:15am - 9:30am Overview, Michac! Gibbs, ICF

9:45am - 10:00am Microbial Ecology of the Rumen, Bob Hespell, USDA

10:00am - 10:15am Productivity Enhancement and Methane Emissions, Henry

Tyrell, USDA

10:15am - 12:00 Discussion

12:00 - 12:45pm Lunch Brought In
‘NEXT STEPS FOR REDUCING METHANE EMISSIONS FROM
RUMINANTS

12:45pm - 1:00pm ARS Planning and Priorities, Lewis Smith, ARS

1:00pm - 3:00pm Discussion of:

~ Projects for improving emissions estimates

- Projects for evaluating emissions reductions
options

- Forming and Ad Hoc Group

- Others to involve

Workshop Adjourned

February 23, 1989


A-15

(U.S.), and Europa Year Book (USSR). Global animal population data
presented by Lerner et al. generally agreed with FAO statistics: 1 percent
or less variation for bovines, buffalo, sheep, pigs, camels and horses; 6
percent for buffalos; and 5 percent for goats.

Methane Production Rates. Values for methane production rates for each
type of animal are taken from Crutzen et al. (1986). These rates are as
follows:

° Cattle: 55 kg CH,/head/year in developed economies; 54 kg
CH,/head/year in Australia, Brazil, South Africa and Argentina; .and
35 kg CH,/head/year in developing economies. .

° Sheep: 8 and 5 kg CH,/head/year in developed economies and in
developing economies and Australia, respectively.

° Pigs: 1.5 and 1.0 kg CH,/head/year in developed and developing
economies, respectively.

° Others: Production rates for camels (58 kg per head per year),
water buffalo (50 kg CH,/head/year), goats (5 kg CH,/head/year),
horses (18 kg CH,/head/year) and caribou (15 kg CH,/head/year) were
constant for world populations.

Animal populations were distributed throughout a 1° latitude by 1°
longitude grid of the world. Lerner et al. multiplied the CH, production
rates by the populations in each zone to get a global distribution of CH,
emissions. Lerner et al. found that over 55 percent of emissions from
animals are concentrated between 25°N and 55°N latitude. Global CH,
production from domestic animals is estimated to be 75.8 Tg CH,, 75 Percent
of which is contributed by cattle.


APPENDIX A

GLOBAL METHANE EMISSIONS FROM RUMINANTS

This appendix summarizes several of the published estimates of methane
(CH,) emissions from ruminants. First, the primary factors affecting
methanogenesis in ruminants are discussed. Then, several of the major
estimates of emissions are summarized.

A.1 FACTORS AFFECTING METHANOGENESIS

The rumen is the unique physiological characteristic of ruminants that
allows them to digest the energy in forages that cannot be consumed by
humans. These animals (mostly cows, buffalo, sheep, goats, and camels, but
also including deer, reindeer, caribou and others) are characterized by a
large "fore-stomach" or rumen. For example, a cow’s rumen may have a
volume of 150 liters, whereas a pig (a non-ruminant monogastric animal)? has
a stomach with a size of about 6 to 8 liters.” This large "stomach" allows
large quantities of forages to be consumed, and provides a location for the
forages to be fermented. Other non-ruminant herbivores (e.g., horses,
rabbits, guinea pigs, hamsters) are able to consume forages in amounts
between ruminants and non-ruminant monogastrics due to an enlarged cecum
and large intestine (Ensminger (1983), p. 21).

Within the rumen, microorganisms play an important role in digestion.

Over 200 species and strains of organisms have been identified to date,
although a smaller number dominate (Baldwin and Allison (1983), p. 462).

. These organisms form a complex ecology that includes both competition and
cooperation. The organisms are important for fermenting the primary feed
constituents (carbohydrates, lipids, urea, and proteins) into secondary -
products that can be catabolized further and subsequently used by the
animal. The population mix of the bacteria is influenced by the diet
consumed by the animal.

Rumen methanogenic bacteria are the source of CH, produced in ruminants.
Although these bacteria are a very small fraction of the total population
of microorganisms in the rumen, they play an important role in the complex.
rumen ecology. While methanogens can convert acetate (a fermentation
product produced in the rumen) to CH, and CO, this pathway for CH,
production in the rumen is believed to be of minor importance (Baldwin and

2 Other non-ruminant monogastric animals include inter alia: dogs, cats,

monkeys, and humans.

2 A steer’s rumen is about 20 times larger than a pig’s stomach, even
though a steer weighs only about 5 times more than a full-grown pig (Ensminger
(1983), p. 216).


METHANE PRODUCTION BY ANIMALS.

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geocnemistry of carbon. Am. J. Sci. 247, 27-32.

Janzen. D. H. 1983. Food wens: Who eats what. why.
how and with what effects in a tropical forest’ In:
Ecosvstems of the world 144, Tropical rain torest
ecosystems. Structure and function, ed. F 8. Gollev.
Elsevier. Amsterdam—Oxtord—New York. p. 167-
182.

Jordan, C. F. 1983. Productivity of tropical rain forest
ecosystems and the implications for their use as
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Josens. G. 1983. The soul founa of tropical savannas {11.
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Kempton. T. J. and Leng. R. A. 1979. Protein nutntion
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302.

Khail, M. A. K. and Rasmussen. R. 1983. Sources.
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Kirchgessner. M. 1985. T-erernahrune. OLG-Veriag
Frankfurt. 6. Auflage. 488 pp (in German).

Kirk. E. 1949. The quantity and composition of human
flatus. Gastroenterotogy 12 (5), 782-794.

Klerber, M. 1961. The fire of life. An introduction to
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Krishna. G.. Razgan. M. Nand Rav. S. N. 1978
Effect of nutritional and seasonal variations on heat
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Anum. Sct. 48, 366-370.

Lamotte. M. and Bourtere. F. 1983. Energy flow and
nutrient cycling in tropics! Savannas. In: Ecosystems
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. M. D. and Bond. J. H. 1970. Volume. compo-
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Levy. I]. H. 1971. Normai atmosphere: farge radical
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Lieth. H. 19°S. Measurement of calomfic values. In:
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Martminsen. D. ana Fleming. S. E. 1982. Excretion of
‘breath and flatus gases cv humans consuming high-
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Tellus SSB (1986). 3

233

Mavnara. L. A ana Luosi. J. K. 1962. Animes murinon.
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MeConneil. J. C., McElroy. M. B. and Wofsv. S.C.
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MeKav. L. F , Eastwood. M. A. and Brydon. W G.
1985. Methane excretion in Man—a study of breath,
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Menke. K.-H. and Huss, W. 1975. Tierernohrune und
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Moen. A. N. 1973. Wildlife ecology: an analvncat ap
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11899-11605.



25

As noted by Crutzen et al., various uncertainties remain in these
estimates. Chief among them are realistic emissions rates for animals in
developing countries. Appendix A summarizes various uncertainties in the
estimates presented, and Appendix C presents a copy of the paper published
by Crutzen et al.

2.3 TRENDS IN SUPPLY AND DEMAND

Livestock provide a diverse set of products for human consumption.
Throughout the world, livestock management, processing, and product
distribution are significant economic activities, providing important
sources of nourishment to all people.

The current markets for livestock products reflect the complex
interaction of a diverse set of factors including: genetic characteristics
of animals; management practices; the availability of natural,
technological, and human resources; consumer preferences; and cultural
preferences and traditions. Government policies are used throughout the
world to influence these various factors.

As a result of these numerous factors, the markets for livestock
products vary considerably throughout the world and are constantly
changing. These changes will influence the levels of CH, emissions from
livestock, as well as the opportunities for reducing emissions.

TRENDS IN SUPPLY

Within developed nations, the technologies and methods for intensively
managing ruminants to produce milk and meat products have increased
productivity dramatically over the past 40 years. In particular, the
productivity of milk cows has increased substantially during this time.
Although feed intake per cow has increased with milk production per cow,
the increases in productivity have enabled larger quantities of milk to be
produced per amount of feed (and other) inputs. The result is that larger
amounts of milk are produced per amount of CH, emitted. This trend may be
an important factor influencing future CH, emissions from ruminants.

Several of the key trends in the supply of milk and meat products from
intensively managed cattle are as follows:

° se ‘O Vv: E Ww uy 1 ve d.
roved management. With the development of artificial

insemination techniques and methods of evaluating bulls and cows,
the systematic breeding of dairy animals has been performed in the
U.S. and elsewhere with considerable success. The high genetic
potential of Holstein dairy cows to produce milk has been
distributed throughout the dairy herd, and management methods have
improved (e.g., in the preparation of balanced rations) so that


21

byproducts with low digestibility (e.g., wheat straw, rice straw, and sugar
cane tops), with levels of intake near maintenance requirements. For these
animals on relatively poor diets, Preston and Leng (1987) indicate that CH,
yields may be in the 9 to 12 percent range, with the level influenced by
the adequacy of ammonia levels in the rumen (Preston and Leng (1987), p.

. 40). In their assessment, (based on stoichiometric considerations)
inadequate ammonia levels are related to inefficient rumen fermentation and
increased CH, production. If this is the case, supplementing diets of these
animals with urea or poultry litter (good sources of rumen ammonia) could
increase rumen fermentation efficiency and reduce CH, emissions. Such
supplements are starting to be provided to milk cows in India, for example,
as a means of increasing milk production.

Considerable uncertainty remains regarding the levels of CH, emissions
anticipated from animals in developing countries. The Preston and Leng
assessments indicate larger CH, yields than would be indicated by Blaxter
and Clapperton. Because feed costs account for a significant portion of
the costs of producing milk and beef in developed countries, considerable
data have been collected on the performance of feeds in these areas.
However, less data are available to describe feed characteristics and
performance in most developing country situations.

Anima {<5 a

The manner in which an animal population is managed will influence the
overall level of CH, emissions. In general, a population of managed animals
is maintained in order to produce some set of useful products, such as
milk, meat, wool, and (in the case of animals in developing countries)
work. The size of the population required in order to produce the desired
level of products will depend on the productivity of the animal population.

The productivity of dairy cows is primarily measured by the amount of
milk produced per cow per year. Significant increases in productivity have
been achieved in the U.S. and around the world due to selected breeding and
improvements in animal management. By increasing the amount of milk
produced per cow, the feed requirements per amount of milk produced have
declined. Concurrent with reductions in feed requirements should be
reductions in the amount of CH, generated per amount of milk produced. This
result is anticipated assuming that CH, yields per amount of feed energy
consumed remain unchanged. The possibility that CH, yields of more
productive dairy cows are in fact lower than average (possibly contributing
to the increased productivity of the cows) remains to be demonstrated
conclusively.

In addition to examining the productivity of dairy cattle on a per cow
basis, the productivity of the population as a whole can be assessed. At
any point the dairy cattle population includes not only lactating dairy
cows (i.e., those actually giving milk) but also those between lactation
cycles and those that are growing (i.e., replacement heifers that have yet
to give milk). By reducing the time between lactation cycles, increasing


WORKSHOP AGENDA (Continued)

SESSION 1: FEBRUARY 27, 1989 (continued)
LOCATION: GARDEN ROOM, SPA HOTEL AND MINERAL SPRINGS

CHARACTERIZATION OF POPULATIONS AND EMISSIONS

2:00pm - 2:20pm Demography and Ecology of Cattle in Developing Countries,
Stewart Odend’hal, University of Georgia

2:20pm - 2:40pm + Dependence on Cattle Populations in Developing Countries, Jim

- Ellis, Colorado State University

2:40pm - 3:15pm Discussion

3:15pm - 3:45pm Systems Approach to Evaluating Methane Emissions, Jim Fadel,
U.C. Davis

3:45pm - 4:30pm Discussion

5:45pm MEET IN LOBBY FOR BUS TO DINNER ON MT. SAN JACINTO

February 23, 1989


33

Similarly, animal waste management practices vary throughout the world.
The extent to which wastes are burned, spread as fertilizer, placed in
digesters, or disposed of in ponds must be evaluated. A summary of animal
waste management practices is required.

One effective approach to developing this characterization is to define
a set of “animal/management categories" that represent the range of animal
situations that exist throughout the world. Such categories might include:
intensive dairy farming in the U.S., using Holsteins and concentrate
feeding; feedlot beef cattle in the U.S. on high grain diets; stocker
cattle in the U.S. in pastures and on ranges; cow/calf operations in the
U.S.; range/pasture cattle in South America; draft bovines in developing
countries that are fed rice and wheat byproducts; cattle in developing
countries that are managed by pastoralists and graze the available forage;
etc.

The categories would differ along characteristics that influence CH,
emissions. The key characteristics of each group could include: number of
animals; typical type of animal ownership; type and quantity of feed
consumed (including key feed characteristics); animal health services
typically available; products produced from the animals.

DEVELOP AND EVALUATE MEASUREMENT TECHNIQUES

Indirect calorimetry is the laboratory technique currently used to.
perform in-depth evaluations of the performance of alternative feeding
practices. This technique involves placing an animal in confinement for a
period of several days, and measuring the amount of inputs (feed, oxygen,
carbon dioxide) and outputs (excretion, oxygen, carbon dioxide, CH,) from
the confinement chamber. Because CH, is produced during digestion, CH, is.
measured as part of this technique. :

Because indirect calorimetry is primarily used to evaluate animal
energetics, its applicability for quantifying CH, emissions must be examined
closely. Several areas that need to be addressed include:

° How representative are the CH, emissions estimates for an
individual animal of what might be expected for that individual
animal in the field? What factors could lead to the results not
being representative, and are these factors important from the CH,
point of view? Examples of experimental factors that should be
examined include: (1) restrictions to the animal’s intake to
ensure that the experiment can be reproduced; (2) stresses on the
animal from being in confinement; (3) lack of environmental
stresses on the animal (e.g., lack of heat stress); (4) lack of
exercise (this may be particularly important for evaluations of
draft animals); and (5) experiment duration.


A-7

additional factors. However, if such influences exist, they have not been
sufficiently significant to be identified to date.

Given these general factors affecting methanogenesis in ruminants, the
general approach to estimating CH, emissions from this source has been to:

° identify the average amounts of feed consumed by various types of
ruminants;
° adopt an estimate of the portion of feed energy consumed that is

converted to CH, (i.e., a methane yield);

° estimate a rate of annual CH, emissions per animal by multiplying
the methane yield by the annual feed consumption; and

° multiply, the emissions rate per animal by the number of animals.

Estimates published by various authors are presented below.

A.2 GLOBAL EMISSIONS ESTIMATES

Several authors have presented estimates of global CH, emissions from
animals®. Most estimates, however, can be traced back to only a few
sources:

° Ritzman and Benedict (1938): Hutchinson (1948) and Blake (1984)
base their estimates on CH, production rates from domestic animals
on work presented by Ritzman and Benedict (1938). Ehhalt (1974)
and Koyama (1963) cite emissions estimates from Hutchinson.
Hudson and Reed (1979) cite an emissions estimate from Ehhalt.
Khalil and Rasmussen (1983) cite an emissions estimate from Hudson
and Reed; -

° Crutzen and Seiler: Crutzen and Seiler contributed to various
estimates including: Crutzen et al. (1986); estimates by Seiler
in Bolle et al. (1986); and Seiler (1984). Lerner et al. present
estimates based on CH, production rates from Crutzen et al. (1986).
Sheppard et al. (1982) cite emission data from a personal
communication with Crutzen.

In addition, both Ehhalt (1974) and Blake (1984) cite Woodwell (1970) as
the source of total plant material consumed by herbivores.

5 See, for example: Blake (1984); Bolle, Seiler and Bolin (1986);
Crutzen, Aselmann and Seiler (1986); Ehhalt (1974); Hudson and Reed (1979);
Hutchinson (1948); Khalil and Rasmussen (1983); Koyama (1963); Lerner,
Matthews and Fung (1988); Seiler (1984); Sheppard et al. (1982).


B-8
EXHIBIT B-1

METHANE EMISSIONS ASSUMPTIONS

tare waren
Rapidly Changing World ‘Stomty Changing World
‘Tors CH4 ememons ‘Toml Cr Emissions
100 10
108 od 1190
heoed winnede me
- 00
pane weenie we
= we
~ ~
be = -
TM Fm ome
~ ba oma
~ ~
= =
= oe
- -
- 4. " o
a) = me aa nee me

‘Tow! CH4 Emesiora from Rumanern Animnaie ‘Tow CH4 Emissions trom Purunert Animate

tow
#6 &

a

RCW and SCW refer to Rapidly Changing World and Slowly Changing World
scenarios, respectively. The scenarios labeled "with reduction” show a
range of 25 percent to 75 percent reduction from the baseline rate of
emissions from ruminant animals starting in 1990. This range of emissions
reductions is shown for illustrative purposes. The technical feasibility

and costs of reducing methane emissions from ruminant animals is currently
being analyzed.

Source: Taken from: U.S. EPA, “Policy Options for Stabilizing Global
Climate," Draft Report to Congress, February 1989.


U.S. Milk Production (Lbs Milk per Cow per Year)

27

EXHIBIT 2-3

MILK PRODUCTION PER DAIRY COW PER YEAR IN THE U.S.

po

1950 1955 1960 1965 1970 1975 1980 1985

Source:

NMPF, Dairy Producer Highlights, National Milk Producer
Federation, Arlington, Virginia, 1987, p. 5.


276

body weight of 570 ke (Nowak and Paradiso.
1983). Applying the general formula (1) for basal
“metabolism, we calculate a mean minimum en-
ergy demand of 34 MJ per day. The ratio of the
mean basal metabolism of cattle in India with 3
mean body weight between 200-350 ke (H.
Steingass, personal communication) to the re-
Ported gross energy intake is about 1:3. Applying
this ratio to camels, we calculate a mean gross
energy intake of 100 MJ per animal per day.
Camels live essentially on roughage. With 9°;
methane yield as in the case of Indian cattle, we
calculate the methane production from camels to
be 58 kg per individual per year, which results in
a global yearly CH, emission of | Tg from a total
of 17 million camels. Other camelids (Llamas.
Alpaca, cte.) have populations too smail
(McDowell, 1976) to produce globally significant
amounts of CH,.

5. Methane production by non-ruminant,
domestic animals

‘Yhe methane yield from pigs on highly
digestible fattening feeds is less than 1° of the
gross cnergy intake (¢.g., Schneider and Menke.
1982). Taking data from Europe. gross encrey

* intake 1s between 12.5 MJ per day for young pigs
and about 90 MJ per day for lactating sows.
Based on age and werght-class population
staustics from West Germany, we calculate 2
mean individual gross energy intake of 38 MJ per
day. Of this. about 0.6°% is released as methane
(Schneider and Menke, 1982), yielding 1.5 ke
CH, per year. We assume that this number
applies to developed countries. In developing
countries, the animals are smaller and less well
nourished. with diets consisting commonly of
kitchen refuse or green fodder. With these foods.
methane yields might reach 2% (H. Steingass.
personal communication). Assuming the eross
energy intake to be + of that in the developed
world and adopting a methane yield of 1.3°,, we
calculate a yearly CH, production rate of 1.0 kg
in the developing world. Multiplied with the pig
populations in the developed and developing
world, this yields atout | Tg CH, per year from
pigs.

Methane yields for horses are between those
for pigs and rummmants. They equal 34°; of the

P. J. CRUTZEN, I. ASELMANN AND W SEILER

digestible energy or 2-3°% of the gross energy
imtake (Kirchgessner, 1985). The energy demang
for norses with a mean body weight of 550 ke.
executing medium work loads for 2 h a day, is
about 78 MJ of digestible energy or 110 MJ of
gross energy (National Academy of Sciences,
1973). Similar values are given by Kirchgessner
(1985). If 2.5%3 of the gross energy intake is
released as methane, we calculate a mean yearly
CH, production of 18 kg per animal. The world
Population of 64 million horses therefore pro-
duces a total of 1.2 Tg CH, per year. Similarly,
we deduce a mean production rate of 10 kg per
animal per year for the global mule and donkey
population of 54 million, leading to a total emis-
sion of 0.5 Tg of CH, per year.

6. Methane production by humans

Methanogenic bacteria in the large intestine of
humans produce amounts of methane which vary
greatly between individuals. The percentage of
healthy humans who produce methane ranges
from about 30%, to more than 50% (Bond et al.,
1971; Bjorneklett and Jensen. 1982: McKay et
al.. 1985). The methane produced in the large
intestine is partly absorbed by the blood within
the colon wall and exhaled through the lungs, and
partly excreted in flatus gas. :

Measured CH, mixing rauos in exhaled air
from methane-producing individuals vary widely.
trom only a few ppm above ambient air ratios to
more than 70 ppm. with an average of 14.8 ppm
from 280 healthy individuals (Bond et al., 1971).
Levitt and Bond (1970) reported a mean value of
21 ppm CH,. In a series of experiments on 120
healthy humans. Bjorneklett and Jensen (1982)
observed a medium methane mixing ratio in
exhaled air of 16.3 ppm. This leads to mean
individual CH, exhalation rates of 40-50 g per
year. assuming a mean breathing volume of 7
1.mun (Schulz. 1972). The methane exhalation by
the human population of 4.7 x 10° is therefore.
equal to about 0.2 Tg per year. This surprisingly
small quantity 1s totally negligible in the global
CH, budget.

Kirk (1939) measured 2-8°% methane in the
Matus gases trom a group of 20 individuals. The
average production of flatus gas from this group
was 1.3 mi'min. Extrapolating this information to

Tellus 38B (1986), :~


8

relationship among CH,, CO, OH, and 0,. Although trends in the emissions
and abundance of CO remain to be established, large anthropogenic sources
of CO have been identified, adding support to the assumption that CO
emissions and abundances have increased substantially.

Unfortunately, time trends for OH are not sufficiently well defined in
order to establish its relative importance in the measured increase in CH,.
It is likely, however, that decreases in OH are not sufficient to explain
completely the observed increases in CH, (Bolle, Seiler and Bolin (1986).
p. 166). The relative importance of changes in emissions and OH levels
continues to be investigated.

Emissions estimates for CH, remain somewhat uncertain. The primary
anthropogenic sources of CH, emissions include: ruminant animals (primarily
cattle, buffalo, and sheep); rice paddies; biomass burning (e.g., forest
fires); termites from disturbed forests (e.g., deforested areas); venting
and incomplete flaring of gas during oil exploration and extraction;
-leakage of natural gas during natural gas extraction and distribution; coal
mining; and landfills. Current estimates indicate that these sources
account for about 60 percent of current CH, emissions, with ruminant animals
accounting for nearly one fourth of this, or about 15 percent of the total.
The remaining emissions, from natural sources, are associated with
wetlands, marshes, lakes, and oceans.

In order for the atmospheric abundance of CH, to be increasing at the
observed rates, it is believed that CH, emissions must be increasing.
Increasing populations of ruminants, increasing area planted to rice (and
increases in the “double cropping" of rice; i.e., planting two crops a
year), increasing production and distribution of natural gas, and
increasing production of coal have been cited as evidence of increasing CH,
emissions from these sources. Some of the key natural sources (e.g.,
wetlands and marshes), have reduced in area due to development pressures in
various parts of the world. Consequently, increasing emissions from :
anthropogenic sources are believed to be the primary cause of increasing
emissions .”

Exhibit 1-5 presents estimates of the time trend of emissions and
estimates of recent emissions. As shown in the exhibit, the time trend
estimated by Seiler indicates that total emissions are increasing at an
average annual rate of over 1.0 percent per year. The estimate of current
emissions rates by source shows the relatively large uncertainties that
remain regarding the allocation of total emissions among source categories.

1 Large anthropogenic sources include fossil fuel and biomass

combustion as well as oxidation of CH, and other anthropogenic hydrocarbons.
See: WMO (1986), pp. 104-106.

2 It has also been mentioned that warming in the Arctic may be leading
to increased CH, emissions from tundra, see WMO (1986), p. 99.


B-9
EXHIBIT B-2

SIMULATED METHANE CONCENTRATIONS

FCW Methane Concentration ‘SCW Methane Concentration
4500 4500,

ROW

w/ 25% reduction 00

wi 75% reduction 3500}
scw
wi 25% reduction
wi 75% reduction

2100

1985 2000 2025 2050 2075 2100

RCW and SCW refer to Rapidly Changing World and Slowly Changing World
scenarios, respectively. The scenarios labeled "with reduction" include a
25 to 75 percent reduction in methane emissions associated with ruminant
animals starting in 1990. This range of emissions reductions is shown for
illustrative purposes. The technical feasibility and costs of reducing
methane emissions from ruminant animals is currently being analyzed.

Source: Estimated using the Atmospheric Stabilization Framework
developed for: U.S. EPA, "Policy Options for Stabilizing Global Climate,"
Draft Report to Congress, February 1989.


Page 2 of Note 1 to Appendix B

METHANE CONCENTRATIONS

Methane concentrations are modeled with the following simple annual
integration:

CONC, = CONC,., + EMIT, - LOSS, q)
where: CONC = methane concentration (e.g., in ppmv);

EMIT = methane emissions (converted to the units of
concentrations); and

LOSS = destruction of atmospheric methane.

The initial concentration (circa 1985 atmosphere) is taken as 1.6 ppmv. A
variety of emissions scenarios may be used, reflecting varying assumptions
about the known sources of methane emissions.

The LOSS term reflects the processes that destroy methane in the
atmosphere. The dominant process is oxidation by the hydroxyl radical
(OH). The overall destruction process is modeled using an atmospheric
"lifetime" as follows:

LOSS, = CONC,., / LIFE,.; (2)
where: LIFE = the atmospheric lifetime for methane.

The initial lifetime (circa 1985 atmosphere) for methane is taken as 9.6
years. This implies that about 10 percent of the methane in the atmosphere
is destroyed by natural processes each year.

Of note is that the methane lifetime is modeled to change over time in
response to modeled changes in OH and tropospheric temperature. The
following equation is used:

LIFE, = LIFE, * (1 - (0.95 * 50H) - (0.02 * 6T)) (3)
where: LIFE, = initial lifetime of 9.6 years;

60H = calculated perturbation to OH (estimated as the
average of the northern and southern hemispheric
perturbations) relative to the reference atmosphere (as a
fraction, e.g., -0.10 is a 10 percent reduction in OH); and

6T = perturbation in global average tropospheric
temperature relative to the reference atmosphere (in
degrees).


1. INTRODUCTION

1.1 SUMMARY

It is well documented that the global atmospheric abundance of methane
(CH,) is increasing. Recent rates of increase are on the order of one
percent per year, or about 0.017 ppmv per year (ppmv is parts per million
by volume). This increased abundance of CH, will have important impacts on:
the stratospheric ozone layer; background levels of tropospheric (i.e.,
ground-based) ozone; and global climate.

Managed livestock, and in particular, ruminants, are important
contributors to the increasing abundance of atmospheric CH,, accounting for
on the order of 15 to 20 percent of annual CH, emissions. As shown in
Exhibit 1-1, the population of managed ruminants has been increasing
globally for over 30 years. According to FAO statistics, the numbers of
managed ruminants in 1987 included: 1.3 billion cattle; 1.2 billion sheep;
0.5 billion goats; 0.1 billion buffalo; and 19 million camels (FAO, 1988).
In recent years, animal numbers have steadied or declined in the U.S. and
Europe; however, growth continues among developing nations.

CH, production is part of the normal digestive activity of ruminants.
The primary mechanism producing CH, in these animals is methanogenic
bacteria in the rumen converting fermentation products (primarily carbon
dioxide plus hydrogen or formate) into CH,. CH, is also produced and
emitted to various degrees from livestock wastes. Reducing CH, emissions
from livestock-agriculture systems alone will help to reduce the rate of
increase in the abundance of CH,. In concert with reductions from other
sources, it could help to stabilize the CH, abundance in the atmosphere at
roughly current levels.

At this time, numerous questions and uncertainties remain regarding
sources of CH, emissions and options for reducing emissions. Two points are
clear, however: -

° With its relatively short atmospheric lifetime (on the order of 10
years), CH, is a good candidate for stabilization. An overall
emissions reduction on the order of 10 percent is required in
order to prevent the CH, abundance from continuing to increase (see
WMO (1986), pp. 92).

° Given the diverse nature of the sources of CH, emissions, _
addressing emissions from one or two sources will not be
sufficient to stabilize the abundance of CH, in the atmosphere.
Instead, opportunities for reducing emissions from all sources
must be identified and evaluated.


B-13
EXHIBIT B-5

REDUCTION IN GLOBAL WARMING ACHIEVABLE
THROUGH VARIOUS TECHNOLOGICAL MEANS IN THE RCW SCENARIO

Explanation of Scenarios:

1.

e Gas: Assumes that economic incentives accelerate
exploration and production of natural gas, reducing the cost of
locating and producing natural gas by an annual rate of 0.5% relative
to the RCW scenario. Incentives for gas use for electricity generation
increases gas share by 5% in 2025 and 10% thereafter.

25% Reduction in Ruminant Animal Emissions: 25% reduction in ruminant

animal emissions from the baseline levels in the RCW. The baseline RCW
emissions do not include emissions associated with manure handling.
Consequently, assuming that methane emissions from manure can be
reduced, this estimate is biased downward.

Emissions Control: Stringent NO, and CO controls on mobile and
stationary sources.

75% Reduction in Ruminant Animal Emissions: 75% reduction in ruminant

animal emissions from the baseline levels in the RCW. The baseline RCW
emissions do not include emissions associated with manure handling.
Consequently, assuming that methane emissions from manure can be
reduced, this estimate is biased downward.

Reforestation: Rapid reforestation so that the terrestrial biosphere

becomes a net sink for CO, by 2000. This requires reforesting 565x10®
hectares (2.1x10° square miles) by 2015 and 1,185x10® hectares (4.4x10%
square miles) by 2100. .

Nuclear Power: Promote nuclear power. Assumes that technological
improvements in nuclear design reduce costs by about 0.5% per year.

Emissions Fees: Emissions fees on fossil fuel production and
consumption in proportion to carbon content. Production fees of
$0.50/GJ for coal, $0.36/GJ for oil, and $0.23/GJ for gas (GJ = giga-
joule). Consumption fees of 28%, 20%, and 13% for coal, oil, and gas,
respectively. Production fees implemented fully by 2050, consumption
fees by 2025. °

Transportation: Fuel efficiency of new cars in the U.S. increases to
40 mpg by 2000. Global fleet average fuel efficiency reaches 50 mpg by
2050.

Source: U.S. EPA, "Policy Options for Stabilizing Global Climate,"

Draft Report to Congress, February 1989.


APPENDIX E

LIST OF WORKSHOP ATTENDEES


24

For heirers and steers with body weights of 450
ke ana 600 kg. mean gross energy intakes are
125 MJ and 165 MJ per animal per day
(Kirchgessner, 1985), respectively, of which 7°%
1s lost as methane (e.g., Wainman et al. 1978).
This converts to a yearly methane production of
65 kg per animal as a weighted mean for heifers
and steers.

Within the age class younger than 24 months,
about 10% of the animal population is kept for
veal production. These animals are fed liquid,
milky food which strongly limits CH, production.
Calves younger than 6 months are also fed pri-
marily on milk and other highly digestible feed
which do not promote methane production.

Adopung a mean body weight of 340 kg in the
age class 6-24 months, the gross energy intake is
about 120 MJ per animal per day (Kirchgessner,
1985). As the quality of the feed changes during
animal growth from highly digestible to mixtures
including more roughage, we adopt a mean CH,
yield of 6.5%. Consequently, we estimate a
Production of $1 kg of methane per animal per
year in this ag? class.

Combining che derived methane yields with
the cattle populations in the given age classes in
West Germany. an average, annual methane
Production of 57 kg per head is calculated. As
other European countries have relatively more
beef than dairy cattle and thus slightly lower feed
intakes (H. Steingass. personal communication),
we will adopt a mean annual CH, production of
55 kg per bovin for the developed world by extra-
polation of the data derived for the US and West
Germany. This figure may have an uncertainty
factor of about 15°, mainly due to remaining
uncertainties in the methane yields.

Similar methane production rates apply for S.
Africa. Australia, Argentina and Brazil. These
countries have cattle which are kept mainly on
range and fed on roughage (D. E. Johnson,
personal communication). For these countries. we
assume the CH, production rate to be equivalent
to that of US cattle on range, i.e.. $4 kg per
animal per year.

Despite higher methane yields. individual
methane production rates from cattle in the
developing world are lower, because feed intake
is near to. or only slightly above. maintenance,
consisting mostly of roughage or kitchen refuse.
Pancev (1981) Getermined the average daily gross

P. J. CRUTZEN, I. ASELMANN AND W. SEILER

energy intake for grazing cattle in Varanasy
(India) to be equal to 52.8 MJ for cows. 19 MJ
for calves and 73.5 MJ for bullocks. Odend‘hai
(1972) estmated the mean daily gross energy
intake in a cattle population of 3800 individuals
in a West Bengal district to be 60.3 MJ per
animal. In this population. 14% of the cattle were
dairy cows. This is close to the mean for all of
Asia (15.6%) and Africa (12.6%) according to the
FAO (1984). Adopting an average feed consump-
tion of 60.3 MJ for cattle in the developing world
and a CH, yield of 9% for low quality feed
(Krishna et al, 1978. H. F. Tyrrell, Personal
communication), we calculate a mean annual
CH, production rate of 35 kg per animal in the
developing world.

According to the FAO (1984), the world cattle
Population in 1983 was 1.2 x 10°. Of this, 533%
was kept in the developing and 47% in the
developed world, Brazil. and Argentina. Adopt-
ing the annual methane production rates of 35 kg
and 55 kg, respectively, for these fegions, we
calculate a global mean annual CH, production
of about 45 kg per head of cattle, which is
considerably less than the 73 kg adopted by
Ehhalt (1974). The global methane release to the
atmosphere from cattle totals 54 Tg annually
(Table 1). Of this about 40°; is produced in the
developing world. .

4. Methane production by other domestic
ruminants

Buffalos are kept in some Third World coun-
tries for milk production and for farm work.
Body weight and feed demand are higher than for
cattle. so that buffalos require a gross enerzy
intake of 85 MJ per animal per day (Pandey.
1981). We again assume a CH, yield of 9°% and
therefore estimate a production of 50 kg CH, per
animal per year. Given a total population of 124
million. the production of CH, from buffalos
equals about 6.2 Tg per year.

Adult sheep. which weigh 60-70 kg, have a
gross energy diet of 30-40 MJ per day in
Germany and the US, while immatures are fed
20-25 MJ daily (Kirchgessner. 1985: Nationz!
Academy of Science, 1975). In West Germany.
more than 40° of the sheep population is less
than L-year-old, so that a gross energy intake of

Tellus 38B (1986), 3-3


AUTHOR

Crutzen et al.

Blake

Lerner et al.

A-9

EXHIBIT A-3

SUMMARY OF GLOBAL METHANE EMISSIONS

EMISSIONS
(Te/yr)

77.7

71-160

75.8

COMMENTS

Includes: domestic ruminants (cattle, buffalo,
sheep, goats, camels); domestic pseudoruminants
(horses, pigs); wild ruminants and large
herbivores; and humans. Approximately 95%
associated with domestic ruminants, of which
about 75% is associated with cattle. Reported
uncertainty of +15% for domestic animal and
human total. Average estimate of CH,
production from wild herbivores is 4 Tg,
ranging from 2 to 6 Tg. Animal population data
from FAO. Feed energy intake and methane yield
from bovines vary for the following regions:
U.S. dairy cows; U.S., Argentine and Brazilian
range cattle; other developed countries; and
developing countries.

Includes: domestic ruminants (cattle, sheep,
goats); domestic pseudoruminants (horses); wild
ruminants and large herbivores; and he:bivorous
insects (i.e., termites). Lower estimate based
only on domestic ruminant measurements. Upper
limit based on 10% of total dry plant matter
produced consumed by all herbivores, assuming
43% is eaten by cattle and converted to CH, |
with a 2% efficiency, and the remaining 57% is
converted to CH, with a 1% efficiency. Animal
population data from FAO.

Includes: domestic ruminants (cattle, buffalo,
sheep, goats, camels); domestic pseudoruminants
(horses, pigs); and wild ruminants (caribou).
Global animal population density on a 1°
latitude by 1° longitude grid from data
compiled from FAO and individual country
statistics. Methane emissions by latitude and
longitude based:on emissions rates per animal
from Crutzen et al. (1986). Over 75% of
emissions are associated with cattle. About
55% of total emissions is concentrated from
25°N to 55°N latitude.


A-S

EXHIBIT A-2
METHANE YIELD AS A FUNCTION OF

DIGESTIBILITY AND LEVEL OF GROSS ENERGY INTAKE
(percent)

Level of Intake

1.0 1.5 2.0 2.5 “ 3.0
Digestibility
50 6.8 6.7 6.6 6.6 6.5
60 7.4 71 6.8 6.4 6.1
70 8.0 7.4 6.9 6.3 5.8
80 8.6 7.8 7.0 6.2 5.4
90 9.2 8.2 71 6.1 5.0

Estimates based on an analysis of 391 experiments on sheep. Methane
yield is the percent of feed energy that is converted to methane. Level of
intake is measured as the ratio of total gross energy intake to total gross
energy intake needed to meet maintenance energy requirements (e.g., total
gross energy intake equals two times maintenance requirements) .
Digestibility in percent.

Source: Blaxter, K.L. and J.L. Clapperton, "Prediction of the Amount of

Methane Produced by Ruminants," British Journal of Nutrition, Vol. 19,
1965, pp. 511-522.


U

percentage of the gross food energy intake of the animal. Most CH, yield
estimates for ruminants are in the range of 4 to 9 percent.”

Using an estimate of the CH, yield for an animal, its total annual CH,
emissions can be estimated by multiplying its annual gross energy intake by
the appropriate percentage (e.g., six percent) and then converting the
energy value (e.g., in megajoules, or MJ) to a mass basis (i.e.,
kilograms). For example, if a cow consumes 60,000 MJ per year, and has a
CH, yield of 6 percent, the total CH, emissions for the animal would be the

_ equivalent of about 3,600 MJ, or about 65 kilograms.

Methanogenesis occurs within individual animals, and various factors
affect the rate of methanogenesis on the individual animal level. In‘
addition, however, the total amount of CH, produced by a population of
animals can be evaluated in terms of the amount of CH, emitted relative to
the amount of useful product produced by the population. The manner in
which the population is managed will influence the size of the population
required in order to produce the useful products desired, and consequently
the total level of CH, emissions. Factors affecting methanogenesis in
individual animals and populations are described in turn.

Individual Animals

The level and type of diet a ruminant consumes has a strong influence on
an animal's CH, yield and on the amount of CH, produced by the animal.
Blaxter and Clapperton (1965) examined the results 7f 391 experiments on
sheep and found that the CH, yield is primarily a function of two factors:
(1) the digestibility of the feed; and (2) the level of energy consumed in
relation to the maintenance energy requirements of the animal. Exhibit 2-1
shows Blaxter and Clapperton’s CH, yield estimates for a range of values for
these factors .®

As shown in Exhibit 2-1, animals with low intake levels (e.g., 1.0: times‘
maintenance energy requirements) eating low digestibility feed (e.g., 50 to
60 percent) have CH, yields in the 6.8 to 7.4 percent range. Such
conditions may be anticipated among animals in many developing countries.
Alternatively, animals with high intakes (e.g., 3.0 times maintenance)
eating highly digestible feed (e.g., 70 to 80 percent) have CH, yields in
the 5.4 to 5.8 percent range. Such conditions may be anticipated among
highly productive dairy cows in the U.S., for example.

7 See for example: Blaxter and Clapperton (1965) and Moe and Tyrrell

(1979) and Rumpler, Johnson, and Bates (1986).

® Care must be exercised in using the results presented in Exhibit
2-1. One would not expect to find animals consuming highly digestible feed
(e.g., 70 percent or higher) at levels near maintenance. Similarly, one
would not expect to find animals consuming low digestible feed (e.g., 50 to
60 percent) at 3.0 times maintenance.


46

Characterize the current and potential future
populations of animals along dimensions that
influence CH, emissions and opportunities for
reducing emissions, such as: quantity and quality of
feed consumed; waste management practices used;
trends in population size and characteristics;
ownership characteristics; and products produced.

Develop data on the current and anticipated methods
of managing animal wastes in the U.S. and around the
world. Evaluate existing measurements of CH,
emissions from animal wastes, and identify gaps in
measurements. Develop and employ measurement
techniques to fill these gaps. It is likely that
most waste management systems should be measured.

In conjunction with field measurement efforts, develop
and employ modeling approaches for assessing CH,
emissions from animals and animal wastes. In
particular, existing data on CH, yields and kinetics in
wastes should be examined to improve estimates of
potential emissions.

Option Identification and Evaluation. Both near-term and long-

term options for reducing CH, emissions must be examined. These
-assessments must include evaluations of: emissions reduction
potential; costs; social and other barriers or constraints; and
impacts on the quality and safety of the food supply. Activities
will include the following.

Develop and employ modeling techniques to evaluate fully
alternative approaches for reducing methane emissions.
Analysis of the implications for animal populations will
be included in this analysis, as well as assessments of
emissions from individual animals.

Evaluate the potential advisability, effectiveness,
and cost of modifying feed practices and/or the meat
grading system in the U.S. to reduce CH, emissions.

Evaluate the potential advisability, effectiveness,
and cost of using nutrient supplements as a means of
reducing CH, emissions among populations of animals
in developing countries.

Evaluate the implications of emerging technologies
for CH, emissions, such as bovine growth hormone.


50

Rojko, A.S., et al., Alternative Futures for World Food i 985, Foreign
Agricultural Economic Report No. 146, GPO: Washington, D.C., April 1978.

Rumpler, W.V., D.E. Johnson, and D.B. Bates, "The Effects of High Dietary
Cation Concentration on Methanogenesis by Steers Fed Diets With and Without

Ionophores," Journal of Animal Science, Vol. 62, 1986, pp. 1737-1741.

Safley, M.L., and P.W. Westerman, "Biogas Production from Anaerobic
Lagoons," Biological Wastes, Vol. 23, 1988, pp. 181-193.

Seiler, W., "Contribution of Biological Processes to the Global Budget of
CH, in the Atmosphere," in: Klug, M. and C. Reddy (eds.), Current
erspectives i lic 1 ology, 1984.

WMO (World Meteorological Organization), Atmospheric Ozone 1985, NASA:
Washington, D.C., 1986.


B-12
EXHIBIT B-5

REDUCTION IN GLOBAL WARMING ACHIEVABLE
THROUGH VARIOUS TECHNOLOGICAL MEANS IN THE RCW SCENARIO

ESTIMATES FOR 2050

a
é

% Rea'n In Equil. Global warming by 2050
a

°
Promote Natura! Gas Fapid Reforestation
‘Z5N Rea‘n Ruminams: nuclear Power
Emisuiora Contre! Emissions Fees
‘75% Red'n Runinants Trarapertation
2 =

ESTIMATES FOR 2100

B10
nN
=
? or
i er
= ak
i
- 2e
£
|
Promote Natura! Gas Rapia Reforestation
‘23% Reon Runinemts wuclear Power
Galesiona Control falesionn Fees
‘73% fea 'n Ruminants ‘Traraporteation

Note: Scenarios explained on the following page.


12
GLOBAL CLIMATE CHANGE IMPACTS

By changing the radiative properties of the atmosphere, CH, will
contribute to the greenhouse effect (WMO (1986), pp. 873-874). In fact, on
a molecular basis CH, is a more potent greenhouse gas than is carbon dioxide
(CO,). Of note is that the potency of CH, as a greenhouse gas may be
amplified by associated increases in tropospheric ozone (because
tropospheric ozone is also a greenhouse gas) and stratospheric water vapor
(see Exhibit 1-6).° Assuming that the growth rate of global atmospheric
concentrations of CFCs is reduced considerably as the result of future
reductions in the production and use of these compounds , ‘ model calculations
indicate that the CH, contribution to potential future global warming from
human-related emissions will be second only to CQ.

1.3 STABILIZING THE ABUNDANCE OF ATMOSPHERIC METHANE

The current imbalance in the sources and sinks of CH, must be corrected
in order to stabilize CH, concentrations at approximately current levels.
Using estimates of current concentrations and rates of emissions in WMO
(1986), it is estimated that about a 7 to 14 percent reduction in current
annual CH, emissions is required in order to stabilize its current
atmospheric concentration. The range is driven by uncertainties in the
atmospheric lifetime of CH,.> Because some emissions are from natural (and
presumably uncontrollable) sources, the reductions in anthropogenic sources
required to stabilize concentrations are about 10 to 20 percent.

3 The amount of global warming in Exhibit 1-6 is reported in terms of
equilibrium temperature increases associated with a "direct radiative
forcing," which is a measure of the extent of the change in the radiative
properties of the Earth's atmosphere. The actual warming of the Earth's
surface will lag behind the changed radiative properties of the atmosphere
because it takes time for the Earth to come into thermal equilibrium. In
addition, the amount of warming anticipated will be larger than the amounts
shown in the exhibit because the direct radiative forcing is expected to be
amplified by positive feedbacks in the Earth’s climate system.

“ Significant reductions in the future use and emissions of CFCs are
anticipated as the result of the current.and expected future provisions of
the "Montreal Protocol on Substances That Deplete the Ozone Layer," which
has entered into force. t

5 The higher the CH, destruction rate (primarily by OH), the shorter
its atmospheric lifetime. The range of destruction and accumulation rates
presented in WMO (1986) implies a range of lifetimes of about 7.4 years to
15.1 years, with a middle value of about 10 years.


A-4

nutrients (such as nitrogen). In these cases, the efficiency of the
fermentation in the rumen may be reduced significantly, so that the animal
may derive much less useful energy from the feed than would be indicated by
the feed's physio-chemical properties. Due to the nutrient deficiencies,
increasing feed intakes (without correcting the nutrient deficiencies)
would not necessarily increase the amount of useful energy "delivered" to
the animal. Correcting the nutrient deficiencies would improve rumen
fermentation efficiency so that current levels of feeding would provide
more useful energy to the animal. The use of this approach for animal
feeding in developed countries has been suggested as well, although its
applicability has not been demonstrated.

The extent of methanogenesis in individual ruminants has been estimated
by various authors.5 Blaxter and Clapperton (1965) reviewed the results of
615 closed-circuit respiration indirect calorimetry experiments on sheep
and cattle performed over a period of 10 years. Based on an analysis of
the results for 48 different diets in 391 different experiments on 4-5
sheep for various levels of feeding, Blaxter and Clapperton identified feed
digestibility and level of intake to be important factors influencing the
extent of methanogenesis in the rumen, and developed the following equation
to describe CH, production:

Ym = 1.30 + 0.112 D + L (2.37 - 0.050 D)

where Ym is the CH, yield (megajoules (MJ) of CH, produced per 100 MJ of
_ Bross energy feed intake), L is the ratio of net energy intake to
maintenance energy requirements (e.g., two times maintenance), and D is the
percent digestibility of the feed (e.g., 50 percent). The CH, yield
estimated with this equation can be interpreted as the percent of gross
energy intake that is converted to CH, within the animal. The digestibility
of the diets examined ranged from poor hay (54 percent digestible at :
maintenance) to sugar-beet pulp (87.2 percent digestible at maintenance).
The levels of the diets ranged from one to three times maintenance.

Exhibit A-2 presents estimates of CH, yield using the Blaxter and
Clapperton equation. CH, yield increases with increasing digestibility for
feed levels near maintenance. Conversely, at feed levels greater than 2.4
times maintenance CH, yield decreases with increasing digestibility. Of
note is that the results for diets exceeding 2.5 times maintenance are
based on relatively fewer observations, and may be less certain. Based on
a comparison of methanogenesis in cattle and sheep for seven diets, Blaxter
and Clapperton state that these results (based on data for sheep) may also
be appropriate for evaluating methanogenesis in cattle.

5 See for example: Blaxter and Clapperton (1965) and Moe and Tyrrell
(1979) and Rumpler, Johnson, and Bates (1986).


PROLOGUE

A workshop entitled "Methane Emissions From Ruminants" was held on
February 27-29, 1989 to identify and discuss issues relating to the role
that ruminants and other managed animals play in the global methane (CH,)
budget. A draft version of this paper was presented and discussed at that
workshop. This revised version reflects the comments and discussion at the
workshop. A list of the workshop attendees is presented in Appendix E.

The following are the findings that were adopted by consensus by the
workshop attendees. These findings indicate that there are promising
opportunities for reducing CH, emissions from ruminants. Such opportunities
remain to be assessed and demonstrated in the field. Undertaking such
assessments and demonstrations is a recognized priority.

FINDINGS ,

1. Methane is increasing and will affect tropospheric air quality and
global climate.

1.1 The concentration of CH, in the atmosphere is currently
increasing at a rate of approximately 1.0 percent per year.
This rate of increase is well characterized for the recent
past. Additionally, the atmospheric concentration of CH, has
approximately doubled in the past 200 to 300 years.

1.2 Increasing emissions of CH, are the primary cause of increasing
CH, concentrations. Reduction in the rate of CH, destruction
in the atmosphere (possibly associated with increasing
emissions of carbon monoxide) is also a factor.

1.3 Continued increases in the concentration of CH, in the
atmosphere will lead to increases in tropospheric ozone
formation (a component of smog) which is considered a threat to
human health and the environment. Additionally, increasing CH,
concentrations directly and indirectly change the radiative
properties of the atmosphere, contributing to the greenhouse
effect. One other hypothesis raises the concern that
increasing CH, concentrations could contribute to polar
stratospheric ozone depletion.

2. Animals, and in particular ruminants, are an important source of CH,
emissions on a global scale.

2.1 Although uncertainty exists regarding the global sources of
CH,, it is clear that the major anthropogenic sources include:
ruminant animals (primarily cattle, buffalo, and sheep); animal
wastes; rice paddies; biomass burning (e.g., forest fires);
termites from disturbed forests (e.g., deforested areas);


B-4

two scenarios, with the emissions in the SCW scenario being larger in the
later years. The larger emissions in the SCW scenario are driven by the

.. larger population growth in that scenario. A larger human population
requires more food, leading to a larger animal population and larger
methane emissions from animals. Of note is that these emissions estimates
do not include methane emissions from animal wastes.

These scenarios imply that methane emissions from ruminant animals may
increase by a factor of 2.4 between 1985 and 2100. The question is
appropriately asked, is such an increase reasonable, or might there be
important constraints that will prevent such increases from occurring. The
following observations describe why the scenarios adopted for the analysis
may be reasonable.

°

Population Growth. Between 1985 and 2100 the global population
will grow considerably. Precise forecasts over 115 years are not
possible, however. The range of the population scenarios used in
the analysis are based on demographic projections by various
groups and include population growth ranging from a factor of 2.0
(Rapidly Changing World, RCW) to 2.6 (Slowly Changing World,
SCW). If the intensity of animal products produced and consumed
per capita throughout the world did not change over time, and if
technology did not change, then in the absence of physical and
economic constraints, one could expect that methane emissions
from ruminant animals would increase by a factor of 2.0 to 2.6
over this period. é

nomic Growth and Per Capita Consumptior ma
The RCW and SCW scenarios reflect a range of future GNP per
capita growth assumptions. Although GNP per capita is simulated
to grow throughout the scenarios (reflecting continued economic
growth) these growth rates of GNP per capita decline (by .
assumption) over time, and are lower than recent historical
experience. Nevertheless, based on existing estimates of the
anticipated increased demand for animal products that have
historically been associated with increases in income, and
including adjustments for cultural factors and increased prices.
that would be expected, the intensity of consumption of animal
products per capita is generally expected to increase in the
future.> This conclusion is particularly appropriate because the
largest increases in population are anticipated in areas of the
world that would be expected to increase the consumption of
animal products per capita with increases in income, The
increase in consumption per capita is larger in the RCW scenario

5

If, in general, the world population moves away from the consumption

of animal products, then the future will be quite different than that
described here.


26

the value of the genetic potential has been realized in terms of
"on-the-farm" performance. Exhibit 2-3 displays estimates of milk
produced per cow in the U.S. since 1950.

° ased_ repro: ve efficiency of beef bro: ows. In the U.S.
(unlike in Europe) dairy cows are not the primary source of calves
that are grown into beef.1° Instead, a separate set of cows,
usually referred to as "brood" cows, produce calves that are grown
into beef. The productivity of these brood cows are measured in
terms of the number of offspring produced (reproductive
efficiency) and their meat characteristics (such as weaning weight
and carcass quality). The reproductive efficiency of brood cows
in the U.S. is about 0.75 calves per cow per year. Increased
reproductive efficiency reduces the size of the brood herd needed
to produce a given amount of meat, and hence reduces CH, emissions
per amount of meat produced.

° Increased feed efficiency of beef animals. The cost of feed is a

major cost of growing meat. Consequently, improvements in weight
gain per amount of feed consumed are desireable (i.e.,
improvements in feed efficiency). Two technologies that have been
adopted to promote feed efficiency are ionophore feed additives
and steroid implants. Each of these techniques increases feed
efficiency about 5 to 10 percent (Ensminger (1987), p. 859).
Ionophores are used widely in the U.S. among finishing cattle
(i.e., in feedlots), and among some growing cattle in pasture
situations. Implants are used in growing range, pasture, and
feedlot animals throughout the world. Implants have recently“been
banned in the EEC, however.

These various advances in animal management, combined with a relatively
saturated demand for animal products in developed nations has lead to the
stabilization or decline of animal numbers in the U.S., Europe, and other
developed nations, while milk and meat production continue to increase.
Declining animal numbers in these areas likely indicates reduced CH,
emissions from this source, although changes in animal management
characteristics (such as level and type of feed consumed and waste
management practices used) must also be considered.

13 In Europe, most of the beef (70 to nearly 100 percent, depending on
the country) is derived from the dairy cow population through the calves
Produced by these cows and through the slaughter of older cows. As such,
the cows in Europe are referred to as "dual purpose," i.e., they supply
both milk and meat. In the U.S., most of the beef is derived from calves
produced by beef brood cows. These brood cows are separate and distinct
from the population of cows used to produce milk. As such, the U.S. cows
are referred to as "single purpose," i.e., they produce either milk or
meat.


B-2

would have been produced by the energy production that the
harvested methane replaces will be avoided.”

Given that these benefits may be substantial, it must be recognized that

the analysis that follows includes only a portion of the benefits
associated with reducing me om_ruminant
B.2 APPROACH

This analysis was conducted with the atmospheric module of the
Atmospheric Stabilization Framework (ASF), recently developed by EPA for
its report "Policy Options for Stabilizing Global Climate," (the EPA
Report) .° For the EPA Report, the EPA developed several scenarios of
potential future emissions of greenhouse gases and other gases that will
influence global climate. The approach used here is to:

1. estimate the impacts on global climate for two of the key
scenarios developed for the EPA Report (these impacts are
reported in the EPA Report);

2. for each of the two key scenarios estimate reductions in methane
emissions associated with steps taken to reduce methane emissions
from ruminant animals;

3. create two new emissions scenarios by reducing the methane
emissions by the amounts estimated in step two;

4. for each of the two new scenarios (with reduced methane
emissions) estimate the impacts on global climate using the ASF;
and

5. compare the estimated impacts from the new scenarios with the

impacts from the original scenarios to assess the implications of
reducing methane emissions from ruminant animals.

The differences in the global warming estimates between the new scenarios
and the original scenarios are taken here as the benefits of reducing
methane emissions from ruminant animals.

2 The burning of the harvested methane produces the same amount of

carbon dioxide that the methane would have produced had it been allowed to
be emitted directly and oxidized to carbon dioxide in the atmosphere.
Consequently, the burning of the harvested methane does not add to the
carbon dioxide emissions burden. The avoided carbon dioxide emissions are
associated with the burning of coal, oil, or gas that would have been
required to produce the energy derived from the harvested methane.

3 U.S. EPA, "Policy Options for Stabilizing Global Climate," Draft
Report to Congress, February 1989.


A-12

° Developing Nations. Developing nations (excluding Argentina and
Brazil) have over half the world’s population of cattle. FAO
reports a 1984 population of 642.7 million. The nations that
dominate this population in 1984 include: India: 195.6 million;
China 71.2 million; Mexico: 30.5 million; and Bangladesh: 21.9
million (FAO, 1988). These nations’ populations of cattle account
for nearly 50 percent of the total in this region.

Unlike the cattle in developed nations, the cattle in developing
nations are not used solely for meat and dairy production, but
also are used as draft animals (Odend’hal, 1972). These cattle
are generally fed by-products of the production of food for human
consumption.

Crutzen et al. estimated CH, emissions for cattle in this region

based on a study of Indian cattle performed by Odend’hal (1972).

This study estimated that the daily gross energy intake of cattle
in rural West Bengal was 60.3 MJ per head per day.

To translate the daily gross energy intake into CH, emissions per
head, Crutzen et al. used a CH, yield of 9 percent from a study on
nine lactating cows in India (Krishna et al., 1978). This study
used face-mask-based gas samples taken once daily to estimate the
9 percent CH, yield, which translates into CH, emissions of 35 kg
per year. Of note is that this 9 percent estimate is much higher
than what would be anticipated based on the Blaxter and Clapperton
relationship. For feeds of low digestibility (e.g., 45 to 60
percent), the CH, yield is expected to be on the order of 6.5 to
7.5 percent. Alternatively, it is at the low end of the range
reported by Preston and Leng (1987) (based on stoichiometric
considerations) for animals on diets that are deficient in
nitrogen. Considerable uncertainty remains regarding the
contribution of animals in developing countries to global CH,
emissions.

The estimates for other animals by Crutzen et al. are based on similar
considerations. As shown in Exhibit A-4, Crutzen et al. estimate emissions
from bovines and other domestic animals to be 73.7 Tg per year +15 percent.
Emissions from wild ruminants and large herbivores are estimated to be 2 to
6 Tg per year.


19

These CH, yield estimates can be used to estimate expected CH, emissions
per year by multiplying the rates by the associated levels of intake.
Exhibit 2-2 displays these estimates for a 500 kg beef steer. The
emissions rates reflect both the CH, yield and the influence that feed
digestibility has on required energy intake. For example, at 2.0 times
maintenance, the CH, yield (as a percentage of total feed energy intake)
increases with increasing feed digestibility (see Exhibit 2-1). However,
CH, emissions (e.g., in kilograms per year) decline (see Exhibit 2-2)
because the increasing digestibility reduces the energy intake required in
order to meet the 2.0 times maintenance level.®

Others have also examined CH, emissions rates. For example, Moe and
Tyrrell (1979) report on a total of 404 total energy balance trials on
Holstein dairy cows. Unlike the Blaxter and Clapperton model, Moe and
Tyrrell estimate CH, emissions as a function of the amounts of the following
feed constituents consumed: soluble residue, hemicellulose, and cellulose.
Feeds vary in their content of these constituents. CH, production was found
not to be correlated with the intake of other feed characteristics such as
crude protein, ether extract, and lignin.

Using concentrate and hay feeds typically fed to U.S. dairy cows, and
the feed characteristics reported in NRC (1988), the Blaxter and Clapperton
CH, estimates were compared to the Moe and Tyrrell estimates. For the
chosen diet,?° the Moe and Tyrrell equation results in an estimate of about
120 kg per year of CH, emissions, for an implied CH, yield of about 5.7
percent. The analogous estimate based on Blaxter and Clapperton is 135 kg
per year (for a 600 kg dairy cow), or about 12.5 percent larger than the
Moe and Tyrrell estimate. Given that the two methods for estimating
emissions are based on different data (in fact, different types of
animals), such similar estimates are in reasonably close agreement.

Most ruminants in the world are in developing countries where levels of —
intake and feed characteristics are very different from the diet of U.S.
dairy cows. In general, ruminants in developing countries eat agricultural

® -as with Exhibit 2-1, the results in Exhibit 2-2 must be examined
with care. One would not expect to find animals consuming highly
digestible feed at levels near maintenance or animals consuming low
digestible feed at 3.0 times maintenance.

10 Twenty pounds of concentrate per day containing barley, hominy,
rolled corn, beet pulp, millrun wheat, and cotton seeds, and fifteen pounds
of alfalfa hay per day. This diet is estimated to provide about 2.3 times
the maintenance energy requirement for a 600 kg dairy cow, with a
digestibility of about 65 percent. The diet is also estimated to contain
about: 4 kg/day of soluble residue; 2 kg/day of hemicellulose; and 3.3
kg/day of cellulose.


36

which each of the categories is found throughout the world, and the likely
rates of emissions from each can be used to estimate emissions.

For example, Baldwin, Thornley, and Beever (1987) present the results of
a dynamic simulation model of rumen digestive functions. This model can be
used to evaluate the anticipated level of CH, emissions for a wide. range of
diets. Using the model with data describing the populations of animals
throughout the world and the diets they consume, estimates of global CH,
emissions from animals could potentially be improved. Of note is that the
suitability of the model for analyzing animal diets in developing countries
remains to be assessed.

In addition to improving estimates of global CH, emissions from animals,
the rumen digestion model could be integrated into, or used in conjunction
with an economic model of the livestock sector. Such a combined tool would
be useful for evaluating the implications of undertaking actions (such as
improving the nutrition of animals in developing countries) to reduce CH,
emissions. For example, the alternative diets would be evaluated with the
model of rumen digestion to estimate CH, emissions and animal productivity
(e.g., amount of milk produced over time). The economic portion of the
model would evaluate the costs of changing the diets and the implications
of changes in animal productivity (e.g., increases in milk production) on
the profitability of the livestock sector, prices, and animal numbers.

A possible framework for such a model is presented in Exhibit 3-2. As
shown in the exhibit, policies for reducing CH, emissions would be specified
(e.g., subsidizing the use of certain feeds or feed supplements). The
implications of these policies for animal management decision at the farm
level would be assessed using estimates of prevailing input prices (e.g.,
prices for feed) and output prices (e.g., prices for milk and meat), as
well as estimates of animal productivity (i.e., the amount of inputs
required to produce the outputs).

Based on the simulation of representative production decisions at the
farm level, aggregate levels of production would be simulated, including
the anticipated size of the animal populations. The extent to which these
aggregate levels indicated changes in the anticipated input and output
prices would also have to be evaluated (e.g., if milk production increased
substantially, the price of milk could decline, depending on government
pricing policies). If prices were anticipated to change, then the
simulated farm level decision would have to be revised based on the new
level of input and output prices. Such adjustments would be required until
convergence upon a solution was achieved. .

Such a model could be used to examine the implications of various
policies under a wide variety of assumptions. For example, if feed
supplements were to be provided in developing countries to reduce CH,
emissions and increase animal productivity, the model could be used to
assess the conditions under which animal populations would likely increase


A-6

In reviewing the estimates in Exhibit A-2, care must be taken because it
is unlikely that animals eating near maintenance will be eating highly
digestible feed. Animals near maintenance (e.g., draft animals in
developing nations) would most likely be eating crop residues, such as rice
stalks, which have low levels of digestibility (e.g., less than 50
percent). Similarly, it is unlikely that animals eating at high levels of
intake would be eating low digestible feed. The animal would be unable to
consume enough low digestible feed in order to reach three times

maintenance.

Another model that predicts CH, emissions was derived by Moe and Tyrrell
(1979). A total of 404 total energy balance trials based on indirect
calorimetry were performed on Holstein dairy cows. Unlike the Blaxter and
Clapperton model, Moe and Tyrrell estimate CH, emissions as a function of
the amounts of the following feed constituents consumed: soluble residue,
hemicellulose, and cellulose. Feeds vary in their content of these
constituents. CH, production was found not to be dependent on the intake of
other feed characteristics such as crude protein, ether extract, and
lignin. Based on their experiments Moe and Tyrrell estimated the following

“equation:

CH, (MJ/day) = 3.406 + 0.510 soluble residue (kg fed)
+ 1.736 hemicellulose (kg fed)
+ 2.648 cellulose (kg fed).

The analysis by Moe and Tyrrell is distinguished from the earlier work by
Blaxter and Clapperton in that it relates methanogenesis to feed
+ characteristics in addition to level of intake and digestibility.

Most ruminants in the world are in developing countries where levels of
intake and feed characteristics are very different from the diet of U.S.
dairy cows. In general, ruminants in developing countries eat agriculture
by-products with low digestibility (e.g., wheat straw, rice straw, and
sugar beet tops), with levels of intake near maintenance requirements. For ~
these animals on relatively poor diets, Preston and Leng (1987) indicate
that methane yields may be in the 9 to 12 percent range, with the level
influenced by the adequacy of ammonia levels in the rumen (Preston and Leng
(1987), p. 40). In their assessment, based on stoichiometric
considerations, inadequate ammonia levels are related to inefficient rumen
fermentation and increased CH, production. If this is the case,
supplementing diets of these animals with urea or poultry litter (good
sources of rumen ammonia) could increase rumen fermentation efficiency and
reduce CH, emissions.

It is clear from these various assessments, that CH, emissions from the
digestive tracts of ruminants depends on the amounts and types of
consumed by the animals. Because energy requirements for maintenance and
growth depend on additional factors (e.g., breed, sex, stage of lactation,
heat stress), the extent of methanogenesis may also be influenced by


22

the rate of maturity of replacement heifers, reducing losses due to
disease, and increasing the success rate of replacement heifers (some
replacements are not productive), the total population of dairy cows and
heifers can be reduced while still maintaining the same level of milk
production. Along with such reductions in the population size would come
reductions in the generation of CH,.

Similar analyses of beef cattle populations are applicable. The primary
measures of productivity of beef cattle are rate of weight gain and feed
efficiency. Although beef cattle breeding has not been as successful as
dairy cattle breeding in improving productivity, hormone-based growth
stimulants have been developed that increase feed efficiency about 5 to 10
percent during finishing. These implants are used widely in the U.S. and
other countries, although they have been banned in the EEC.

_As with dairy cows, the total size of the beef cattle population can be
reduced by: reducing losses from disease (antibiotics are currently used);
increasing the birth rate and decreasing the inter-calving interval of cows
used to produce calves for meat production (current birth rates are about
75 calves per 100 producing cows per year in the U.S., and possibly lower
in other countries); and increasing the success rate of replacement
heifers.

In developing nations, cattle, buffalo, horses, donkeys, mules, and
camels are used as draft animals, and cattle, buffalo, camels, goats, and
sheep are used for meat, milk, fertilizer, fuel, wool, and hide production.
In some cases, the animals also form the basis for storing wealth in many
economies that are not based on a "cash" currency. The successful
implementation of realistic methods of increasing the productivity of these
animals within the context in which they are managed remains a challenge.

MANURE AS A SOURCE OF METHANE EMISSIONS

The amount of CH, generated and emitted from manure depends on the
manner in which the manure is handled. If aerobic conditions exist (i.e.,
if the manure is in contact with oxygen) then CH, generation should be
minimal. If the manure is maintained under anaerobic or anoxic conditions
(i.e., in the absence of oxygen), then some portion of the organic matter
in the manure may be converted to CH,.

In many locations, manure is used as fertilizer. If manure is spread on
dry soils, and if it decomposes aerobically, it may produce little or no
CH,. However, spreading manure as fertilizer on anoxic soils (e.g., flooded
rice paddies) will likely produce CH,, possibly in large amounts. Good
field measurements are lacking in this area and need to be undertaken.

In addition to fertilizer, manure is used as an energy source. The
manure may be gathered and dried, and subsequently burned. This method of
handling manure should produce very little CH, as the organic material is
oxidized directly to CO,. Alternatively, the manure may be collected and


Crutzen and Gidel. 1983: Seiler. 1984). Crutzen
(1983) and Seiler (1984) estsmated the giobal CH,
production from ruminants in 1975 to have been
about 60 Tg and 70-100 Tg. respectively. Similar
values have also been reported by Khalil and
Rasmussen (1983) and Sheppard et al. (1982).
None of these papers, however, present a
thorough analysis of the derivation of these esu-
mates. In this paper, we will give a detailed
account of the worldwide methane production by
domestic livestock and wild ruminants. and by
humans, using the extensive information which

has now become available on methane
Production by animal species.

2. Energy utilization and methane production
in animals

The energy content in food is transformed in
the process of digestion and partly lost as chemi-
cal compounds in faeces, urine and fermentation
gases. The rest is used to produce heat, to,
perform body work or to build new body tissue
(Fig. 1). The magnitude of the various losses of
energy depends on the animal species and on the

Fig. 1. Flow aiagram of enerey intake and uulization
by anmais. The magnituce of the vanous losses of
energy cepenas on the animal species ang utilization,
and on the king anc auauty of the reea stuff. Basea on
Kleiber (1961) anc Maynaro anc Loos (1962).

P. 3. CRUTZEN. I. ASELMANN AND W. SEILER

kind and quality of the feedstuff. Measures of
teed quality are digestibility and metabolizabilire,
which are the fractions of the gross energy intake
that are converted to digestible energy and
metabolizable energy, respectively.

In adult homeotherms, base/ metabolion
defines the minimum energy demand under
conditions of thermoneutrality and total rest. The
daily basal metabolism, expressed in megayoules
(MJ), is roughly proportional to the 2 power of

the body weight ' (kg) and is given by the
formula:

basal metabolism = 0.293W/*", a
with an uncertainty of about 14°, (Menke and
Huss, 1975, p. 91). In practice. the energy de
mand to prevent breakdown of body ussue is
higher than the basal metabolism and the actual
gross energy uptake is often expressed in terms of
units of maintenance, that is, the minimum of
food needed to prevent any loss of body tissue
(Maynard and Loosli, 1962). This quantity varies,
depending on utilization and kind of livestock.

Both quality and quantity of the feed. togetber
with the individual performance of the animais.
have been found to determine the amount of
energy that is lost by methane production
Methane 1s a byproduct of microoial breakdown:
of carbohydrates (mainiy cellulose) in the diges-
tive tracts of herbivores. Highest CH, losses are
reported for ruminants. which host large popula-
ions of bacteria and protozoans in their rumens
(e.g., Blaxter and Czerkawsk:. 1966: Wolin.
1981).

In the following, the loss of energy throueb
methane generation will be expressed as a frac-
tion of the gross energy intake. For this. we will
use the term methane yield. Food quanuties. often
given in weight units. were converted to gross
energy intake by using an average conversion
factor of 17.5 MJ‘kg dry matter (Leith. 1975).
The energy content of | kg methane 1s equal to
35.65 MJ.

Early data on methane vieids by cows. sheep.
goats. horses, and one eiephant were publishec
by Ritzman and Beneaict (1938) who found CH.
yields ranging between 33°) ana 7°) fer
ruminants (cows. sheep. goats! fed on main-
tenance level. The methane relezse rates ty
ruminants were lower when fed witn crotein-nce>
diets and higher wnen ted with cruce fder. Te

Tellus 338 (1986). ++


43

EXHIBIT 3-3

PARTIAL AND PRELIMINARY IDENTIFICATION AND
EVALUATION OF CH, EMISSIONS REDUCTION OPTIONS

EMISSIONS REDUCTION
OPTION

(continued)

COMMENTS

Long Term Options (continued)

10. Breed animals that
are low CH,
producers.

The objective of this alternative is to identify
whether there are heritable genetic characteristics
that account for variability in CH, emissions among
individual animals, and to breed animals that are
low CH, producers by taking advantage of these
characteristics. The existence of such traits
remains to be demonstrated, although preliminary
data indicate that such traits may exist.

In order for such an approach to work, the relevant
animal characteristics and the mechanisms via which
the characteristics influence methanogenesis by
microbes in the rumen would have to be identified.
If such characteristics could be identified, and if
they were not undesirable for other reasons (e.g.,
also being associated with low rates of digestion),
animals could be selected for the "low CH,"
characteristics. If the characteristics were
undesirable for other reasons, the mechanisms via
which the characteristics influenced methanogenesis
by microbes could potentially -be exploited.

This approach remains speculative at this time
because host-animal characteristics and mechanisms
that influence methanogenesis by microbes in the
rumen have not yet been identified. One avenue for
initiating such research may be to take advantage
of the considerable amount of existing data on the
breeding histories of dairy cows and some beef
animals in the U.S. These data may enable
hypotheses about heritability to be tested by
measuring CH, emissions from a large number of cows
and examining whether lineage explains any of the
variance that exists among the individuals. In
order to be successful, reliable methods for
inexpensively measuring CH, emissions from large
numbers of animals are required.


Page 4 of Note 1 to Appendix B

concentrations in the ASF such that lower future methane
concentrations result in smaller increases in T-0;. Additionally
T-0, is influenced indirectly by methane concentrations through
the modeled impacts of methane concentrations on CO and column
ozone, reinforcing the direct impacts of methane on T-0,. Because
T-0, contributes to global warming, its lower abundance reduces
its global warming impact.

The reductions in anticipated future global warming associated with the
reduced methane concentrations associated with lower emissions from
ruminant animals accounts for the majority of the global warming benefits.
However, the reductions in future T-0, levels are also significant, thereby
amplifying considerably the global warming benefits of reducing methane
emissions from ruminant animals.* The impact of the reduced lifetimes of MC
and the HCFCs is simulated to have a small impact on global warming under
the scenarios examined in this analysis.‘

The global warming impacts of methane concentrations are modeled using
equations that reflect the "overlapping" effects that methane has with
nitrous oxide (N20), and are as follows:

ETC, = (T, / 1.26) * [DRF(CH4,) - DRF(CH4,) - OVERLAP,] (4)
where: ETC = equilibrium temperature change due to methane;

T, = temperature sensitivity of the atmosphere to a doubling
of carbon dioxide in degrees C (e.g., 4°C);

DRF() = a function that estimates the direct radiative
forcing of a given methane concentration;

CH4, = the initial (i.e., pre-industrial) concentration of
methane (1.02 ppmv); and

OVERLAP, = the overlapping effect of methane with NO.
Equation (4) is used each year to estimate the equilibrium temperature

change associated with the concentration of methane in the atmosphere. The
equation used to estimate the direct radiative forcing is:

> Of note is that T-0;, a component of urban "smog," is recognized as
a threat to human health, crops, and the environment. The non-greenhouse
warming benefits of reducing the extent of future increases in T-0, are not
considered here.

‘ The importance of the MC and HCFC OH-lifetime feedback could
increase if, for example, the use of these compounds increases
significantly in the future.


A-11

groups represent about 10 percent, 12.5 percent and 77.5
percent of the total respectively.’ Canada is assumed to
have approximately the same distribution.

Crutzen et al. estimate the gross energy intake and CH,
production for dairy cows in the U.S. and Canada to be about
230 MJ per day and 84 kg per year (based on a methane yield
of 5.5 percent). For cattle on feed and on range the
estimates are 150 and 110 MJ/day of gross energy intake,
respectively, and 65 kg and 54 kg of CH, emissions per head
per year, respectively, (based on methane yields of 6.5 and
7.5 percent, respectively). Given the distribution of
animals, these values imply and average of about 58 kg per
head per year in the U.S.

-- Brazil, Argentina, Australia, and South Africa. This group
of countries has about 214 million cattle. Crutzen et al.
examined these nations as a region because they have well-
developed beef industries that rely primarily on range
feeding. Crutzen et al. therefore assume that energy intake
and CH, emissions for these cattle will be similar to the
estimates derived for range cattle in the U:S.: feed
consumption of 110 MJ/head/day, a CH, yield of 7.5%, and CH,
emissions of 54 kg/head/year.

-- West Germany. The average CH, emissions for the entire West
German population of cattle is estimated at about 57 kg per
head per year. This estimate is based on the following: (1)
dairy cows -- average intake of 260 MJ/day; 5.5 percent
methane yield; 94 kg CH, emissions per head per year; (2)
heifers and steers between 450 and 600 kg in body weight -+- 7
percent methane yield; 65 kg CH, emissions per head per year;
and (3) 6-24 month old animals -- average intake of 120
MJ/day; 6.5 percent methane yield; 51 kg CH, emissions per
head per year.

Based on these estimates for West Germany, the estimate for the
U.S. and Canada of 58 kg per year, and the estimate of 54 kg per
year for South Africa, Argentina, Australia, and Brazil, Crutzen
et al. adopted a value of 55 kg of CH, emissions per head per year
as an average for all the developed nations.

7? This estimate was reported by Crutzen et al. (1986). Data in FAO

(1987) suggests that the dairy population in the U.S. has remained at 10
percent of the total cattle herd for several years. Ensminger (1987) states
that 26.1 million head or 24 percent of total U.S. cattle population are on
feed, leaving 66 percent of total U.S. cattle population on range. This does
not compare well with the Crutzen et al. values.


Page 5 of Note 1 to Appendix B

DRF = (0.394%CONC-®© + 0.16*CONC#e‘?-6°C°N")) 7(1 +0.169*CONC?-®2) (5)
where: CONC is the methane concentration in ppmv.

Because methane and NO absorb infrared radiation at similar
wavelengths, the use of equation (5) overestimates the implications of
increases in methane concentrations. Consequently, the following "overlap"
equation is used to reduce the estimates of the impacts of methane and N,0:

OVERLAP, = OVL, - OVL, (6)

where: OVL() = a function that estimates the overlap effect, once
with the current concentrations (subscripted with a "t")
and once with the pre-industrial concentrations
(subscripted with an "i"). ’

The overlap function is:

OVL = 0.14*1n(1 + 0.636%(CH4#N20)°-75 + 0.007*CH4* (CH4*N20)?-52) (7)

where: CH4 = the methane concentration; and

N20 = the nitrous oxide concentration.

In interpreting the overlap term in equation (4), one must keep in mind
that the overlap is due to both methane and N,0, and should not be allocated
entirely to methane. For purposes of the analysis performed in this
appendix, the change in the overlap term caused by the reduction in methane
emissions from ruminants (and the subsequent reduction in the future |

increase in methane concentrations) is attributable to the change in the
methane emissions.

A separate equation is used to evaluate the equilibrium temperature
change of increases in T-0;:

ETC, = (T, / 1.26) * 0.00293 * 6(T-05) (8)
where: ETC = equilibrium temperature change due to T-03;

T, = temperature sensitivity of the atmosphere to a doubling
of carbon dioxide in degrees C (e.g., 4°C); and

6(T-03) = perturbation to tropospheric ozone levels relative
to the reference atmosphere (circa 1985) in percent.

In the analyses of reductions in methane emissions from ruminant animals
presented in this appendix, the change in the anticipated future increase
of T-0; associated with the reduced methane emissions account for about 40


30

‘productivity could reduce the rate of animal population growth, and the
possibility of such increases being large enough to allow consumption to
increase while holding animal populations constant remains to be
investigated.

The demand for draft power also has an important influence on animal
populations in developing nations. Virtually all buffalo are in developing
nations, and many of these are used for draft power. An increasing human
population will likely increase the need for draft power, while
mechanization could reduce the demand for animal draft power. However, the
costs of equipment, maintenance, and fuel limit the potential impact that
mechanization will have in the short term.

The combined influence of these various trends in supply and demand on
CH, emissions is unclear. Although animal numbers in developed nations are
not growing and productivity is continuing to increase, animal management
practices may be leading to increased energy consumption per animal and
increased disposal of animal wastes in lagoons. The net effect on CH,
emissions from these animals is therefore ambiguous and remains to be
assessed, Animal numbers and feed consumption are increasing in developing
nations, leading to increased CH, emissions. The rate of increase, however,
remains to be assessed.

In its recent analysis of options for stabilizing global climate, EPA
(1989) estimated future CH, emissions from livestock under a variety of
assumptions. Assuming that policies are not pursued to reduce these
emissions, EPA estimated that CH, emissions from animals could increase by a
factor of about 2.4 by 2100. In light of anticipated population growth: (by
a factor of about 2.0 to 2.6 by 2100) and economic growth (historically,
the consumption of animal products per capita (meat and milk) have risen
along with income per capita), such emissions growth seems plausible.
However, such emissions growth will not be possible if important resource
constraints prevent the supply of animal products from increasing along
with population and income. Such constraints have not been proposed to
date.


6

This investigation of livestock-related emissions is only one part of the
diverse set of analyses required to identify and evaluate options for
stopping the increasing abundance of CH, in the atmosphere.

This paper summarizes the issues associated with reducing CH, emissions
from livestock-agriculture systems. For those involved in addressing
global change, it provides a framework for addressing CH, emissions from
ruminants and as such is a foundation upon which additional data collection
and analysis can be built. The challenge is to build upon existing data in
a manner that identifies preferred opportunities for reducing CH, emissions
as quickly and as efficiently as possible.

For those involved in animal sciences and animal management, this paper
identifies important gaps in understanding and data that require research
and analysis. Additionally, it demonstrates that there are opportunities
to apply expertise and develop options for reducing emissions. Finally, it
highlights that coordination is required among domestic and international
institutions of many types. .

1.2 THE INCREASING ABUNDANCE OF ATMOSPHERIC METHANE
CAUSES OF METHANE INCREASES

The level of CH, in the Earth’s atmosphere is defined by emissions (from
natural and anthropogenic sources) and natural destruction processes. It
is well documented that the atmospheric abundance of CH, is currently
increasing (see for example: Khalil and Rasmussen (1986) and Blake and
Rowland (1988)). Recent rates of increase are on the order of about 0.017
ppmv per year, or about one percent of the current average global level of
abundance of about 1.7 ppmv (see Exhibit 1-2).

Based on analyses of air trapped in the ice sheets of Greenland and
Antarctica, long term CH, trends have been established. The data indicate
that the abundance of atmospheric CH, has increased primarily in the last
300 years, with relatively stable levels prior to that time at about one-
half the current levels (see Exhibit 1-3). This increase in abundance must
be caused by an imbalance in the sources (i.e., emissions) and sinks (i.e.,
destruction) of CH,. The mechanisms leading to these observed increases in
CH, are believed to be: (1) increases in emissions; and (2) possibly
decreases in its rate of destruction.

The destruction of atmospheric CH, is driven primarily by its oxidation
in the troposphere (i.e., the lower atmosphere) and stratosphere by the
hydroxyl radical, OH. Relatively smaller amounts of atmospheric CH, are
consumed by aerobic soils. It has been postulated that the observed
increase in atmospheric CH, may be in part due to a decline in the rate of
CH, déstruction by OH. Such a decline could be caused by a decrease in the
abundance of OH, which could occur as the result of increasing emissions of
both CH, and carbon monoxide (CO). Exhibit 1-4 displays a simplified


4. EPA OFFICE OF AIR AND RADIATION PROGRAM PLAN

This chapter presents a plan for undertaking analyses to: (1) improve
current estimates of CH, emissions from animals, and in particular
ruminants; and (2) identify, evaluate, and implement options for reducing
emissions from this source. The outline for this plan is based on the
findings presented at the beginning of this document.

The following program elements are planned:

° Ad Hoc Group. An Ad Hoc group would track and coordinate’ the .
analyses and investigations needed to better quantify CH, emissions
from animals and options for reducing the emissions. The Ad Hoc
group: should include researchers and practitioners in the fields
of animal science, animal management, atmospheric science, and
others as appropriate; different people would participate at
different times. The mission of the Ad Hoc group should include:

-- develop a plan for various nations and international
institutions for solving the problem of CH, emissions
from animals;

-- provide peer review on analyses and investigations
performed;

-- identify parties who may be appropriate funding
sources for these investigations;

-- identify organizations who may be able to perform
investigations.

° Emissions Characterization. A series of investigations will be
identified that will improve our understanding of the rates of CH,
emissions from animals. These investigations will include the
following.

-- Identify those animals for which emissions estimates
are particularly uncertain. For these groups of
animals, develop and employ techniques for measuring
their emissions within the next year. It is likely
that animals in developing countries will fall into
this category.

-- Develop and implement techniques for measuring CH,
emissions from animals under field conditions.
Opportunities include atmospheric measurements near
animal management facilities as well as techniques
for measuring emissions from individual animals.


5
EXHIBIT 1-1

GLOBAL LIVESTOCK POPULATION ESTIMATES

1300 4

1200 +

1100 +

1000 =

Livestock Units (Millon)

T T “T T
1955 1960 1965 1970 1975, 1980 1985,

These data are suggestive of the recent changes in the global population
of managed animals. The recent data obtained from the FAO for this exhibit
are updated versions of data previously-published by FAO in their
production yearbook series. Although these animal population data must be’
viewed as uncertain due to difficulties in counting animals (particularly
in developing countries), the data are suggestive of a trend of increasing
animal populations globally.

The total population of cattle, buffalo, goats, and sheep are combined
into “Livestock Units" using the following population multipliers: cattle =
0.8; buffalo = 1.0; sheep = 0.1, goats = 0.1.

Sources: Data through 1960 from: FAO, FAQ Production Yearbook, Food

and Agriculture Organization of the United Nations, Rome,
Italy, selected years.

Data after 1960 from: FAO, Livestock Numbers Database
Printout, Food and Agriculture Organization of the United
Nations, Rome, Italy, 1988.


39

EXHIBIT 3-3

PARTIAL AND PRELIMINARY IDENTIFICATION AND
EVALUATION OF CH, EMISSIONS REDUCTION OPTIONS

EMISSIONS REDUCTION
OPTION

Near Term Options

1.

Adopt alternative
feeding practices to
reduce methane
emissions from
animals in developed
countries.

COMMENTS

The use of alternative feeding practices is
applicable primarily to confined animals on
controlled rations, such as dairy cows and feed-lot
animals. (The diets of grazing animals probably
cannot be modified easily in the short term.)

Given that methanogenesis is influenced by feed
characteristics, opportunities for reducing methane
emissions exist by modifying feeding practices.

For example, based on preliminary data it has been
suggested that CH, emissions associated with a
range of commonly used rations in the U.S. may vary
by as much as 50 percent. If the "low CH," rations
were emphasized in place of the "high CH," rations,
CH, emissions could be significantly reduced. Such
an emphasis would, in all likelihood, increase
feeding costs.

This approach may be attractive in the near term
because it does not require a major departure from
the feeding systems currently in use. The .
implications of the modified feeding regimes for
animal productivity and feed costs remain to be
examined, however. It is anticipated that
appropriate "low CH," diets can be identified that
do not sacrifice animal productivity. A systematic
evaluation of CH, emissions associated with
commonly used feeds would provide a basis for
selecting "low CH," feeds. Additional avenues that
may be explored include the use of: (1) "by-pass"
nutrients; (2) defaunation; and (3) oils as feed
supplements. Depending on the costs involved and
the impacts on productivity, government-sponsored
research or research subsidies may be required in
order to promote the development and use of these
feeding techniques.


18
EXHIBIT 2-1
METHANE YIELD AS A FUNCTION OF

DIGESTIBILITY AND LEVEL OF ENERGY INTAKE
(percent)

Level of Intake

1.0 1.5 2.0 2.5 3.0
Digestibility
50 6.8 6.7 6.6 6.6 6.5
60 7.4 7.1 6.8 6.4 6.1
70 8.0 7.4 6.9 6.3 7° 5.8
80 8.6 7.8 7.0 6.2 5.4
90 9.2 8.2 7.21 6.1 5.0

Estimates based on an analysis of 391 experiments on sheep. Methane
yield is the percent of feed energy that is converted to CH,. Level of
intake is measured as the ratio of total gross energy intake to total gross
energy intake needed to meet maintenance energy requirements (e.g., total
gross energy intake equals two times maintenance requirements) .
Digestibility in percent.

Source: Blaxter, K.L. and J.L. Clapperton, "Prediction of the Amount

of Methane Produced by Ruminants," British Journal of Nutrition, Vol. 19,
1965, pp. 511-522.


13
EXHIBIT 1-6

METHANE IS AN IMPORTANT CONTRIBUTOR TO THE GREENHOUSE EFFECT

0.10 —————
L Decadal Increments of Greenhouse Forcing |
0.08 te
o,
T] fee
i
oor 0, =n te |
£ at. u
2 Tf Cat Me? 5 |
qq Fu CO, Fa
004 4
N
Pr G Fe bal 1
8.6
0.02 ppm
| CH,
| Ld
° 1850 -1960 1960's - 970s . 1980's

(per decade)

Decadal additions to global mean greenhouse forcing of the climate
system. The No Feedback Warming is the computed temperature change at
equilibrium for the estimated decadal increase in trace gas abundances, -
with no climate feedbacks included. Based on current models, global :
warming (including feedbacks) is expected to be larger, depending on the
feedbacks assumed.

Note: 0, = tropospheric ozone
Str. H,0 = stratospheric water vapor
Fy, = CFC-11
Fy, = CFC-12

Source: Hansen, J., et_al., "The Greenhouse Effect: Projections of
Global Climate Change," in: Titus, J.G. (ed.),
, U.S. EPA and UNEP: Washington,
D.C., August 1986, p. 206.


2

venting and incomplete flaring of gas during oil exploration
and extraction; leakage of natural gas during natural gas
extraction and distribution; coal mining; and landfills.

2.2 Current estimates indicate that anthropogenic sources account
for about 60 percent of current CH, emissions, with the
remaining emissions, from natural sources, being associated
with swamps, marshes, lakes, and oceans.

2.3 Animals, and in particular managed ruminant animals, produce ,
significant quantities of CH, as part of their digestive .
processes. Based on laboratory estimates of CH, production by
individual animals, and estimates of total animal populations,
ruminant animals are estimated to account for nearly one fourth
of the total anthropogenic emissions, or about 15 percent of
total emissions. These estimates do not include CH, emissions
from animal wastes, which may be significant.

Reductions in CH, emissions from animals will assist in reducing the
rate of CH, increases, and may be one important component in attempts to
stabilize atmospheric CH, concentrations.

3.1 Based on the current imbalance of CH, emissions and destruction
in the atmosphere, a 10 to 20 percent reduction in
anthropogenic CH, emissions is required to stabilize
atmospheric concentrations at their current levels.

3.2 Given the diversity of CH, emissions sources, reducing
emissions from one or two sources will not be sufficient for
stabilizing atmospheric concentrations. Instead, small
reductions in each of the major sources will likely be
preferred.

3.3 A 50 percent reduction in CH, emissions from ruminants will
contribute about 50 to 75 percent of the emissions reductions
needed to stabilize atmospheric CH, concentrations.

3.4 While many uncertainties exist, it would appear that with adequate
resources and appropriate policies, emissions of CH, from livestock
could be reduced from 25 to 75 percent with current resources
directed toward raising livestock. These reductions could be
decreased if significantly larger amounts of resources were
devoted toward growing livestock. Reductions in CH, emissions
would ordinarily contribute to higher animal productivity.

In order to take rational steps to reduce CH, emissions from ruminants,
current emissions must be better characterized and options for reducing
emissions must be identified and evaluated.


WORKSHOP ATTENDEES

(Continucd)

Lewis Smith Henry Tyrrell
ARS-NPS USDA Ruminant Nutrition Lab
B-005 R 204 BARC-East
BARC-W Beltsville, MD 20705
Beltsville, MD 20705 (301) 344-2409
(301) 344-2737

Patrick Zimmerman
Don Torell NCAR
American Sheep Industry Association P.O. Box 3000
7950 Sanel Dr. Boulder, CO 80307
Ukiah, CA 95482 (303) 497-1000

(707) 462-9002


APPENDIX B

IMPACT OF REDUCING LIVESTOCK METHANE EMISSIONS ON
GLOBAL WARMING FROM THE GREENHOUSE EFFECT

B.1 OBJECTIVE

The objective of this analysis is to estimate the potential benefit of
reducing methane emissions from ruminant animals in terms of avoiding
future global warming. By reducing these emissions, the concentration of
methane in the atmosphere will not rise as quickly as it otherwise would,
thereby delaying, and possibly avoiding future global warming.

As is commonly done, the amount of avoided global warming is measured
in this analysis in terms of reductions in equilibrium temperature change .*
In this appendix the equilibrium temperature change is estimated for a
range of assumptions for the period 1985. to 2100.

Of note is that this analysis addresses only the global warming
benefits of reducing methane emissions from ruminant animals. Additional
benefits of reducing these emissions may include:

° Animal Productivity. One of the most promising options for
reducing methane emissions from ruminant animals is to increase
animal productivity, in particular in developing countries.
Promising approaches for achieving this objective include
providing supplements to animals with important dietary
deficiencies (e.g., non-protein nitrogen supplements for animals
with diets that are nitrogen deficient). Not only would the
supplements modify the animal’s rumen fermentation patterns to
reduce methane emissions, the increased animal productivity would
reduce the population of animals needed to produce a given amount
of milk, meat, or work. Overall, the improved animal performance
would be a substantial benefit.

° Animal Wastes. Animal wastes may be contributing significant
quantities of methane emissions. To the extent that this methane
can be harvested for energy, the methane emissions will be
reduced. The value of the energy derived from the methane is a
benefit. Additionally, carbon dioxide and other emissions that

1 Equilibrium temperature change is a measure of the change in the
radiative properties of the atmosphere. This measure is used to describe
the extent to which the atmosphere is trapping additional energy (like a
greenhouse), thereby warming the earth’s surface. The actual realized
temperature increase that will occur will lag behind the equilibrium
temperature change because it takes time for the feedbacks to occur in
response to changes in the earth’s atmosphere and because it takes time for
the oceans to warm and reach an equilibrium with the atmosphere.


23
used in a biogas (i.e., CH,) generator. In this case the organic material
in the manure is deliberately converted to CH,, which is subsequently
collected and used as fuel. The use of biogas generators would result in
CH, emissions only to the extent that CH, leaked from containment or was
“incompletely burned.

In locations where large numbers of animals are managed in a confined
location (e.g., dairies in the U.S. and Europe, feedlots in the U.S., swine
and poultry farms in the U.S.) manure is a waste product that requires
proper handling and disposal. The waste manure may be piled up until it
can be hauled away, or it may be washed into ponds. In either case,
anaerobic conditions are likely to exist, which would allow a portion of
the manure to be converted into CH, and emitted.

The extent of CH, emissions from piles of manure remains to be
quantified. Such emissions may be limited by the acids that are produced
in the wastes during anaerobic decomposition, however. CH, emissions from
waste lagoons and digesters have been measured, and were found to be on the
order of 0.14 to 1.0 cubic meter of CH, per kilogram of volatile solids
added to the lagoon, although in at least one case, emissions were much
higher (Safley and Westerman (1988), p. 187, Hill (1984)). This rate of CH,
emissions translates into about 12 to 85 cubic meters of CH, per metric ton
of manure (wet weight) added to the lagoon, or about 8 to 55 kilograms of
CH, per ton of manure. Because a 600 kilogram dairy cow produces about 15
tons of manure per year (wet weight, Ensminger (1983), p. 737), the
disposal of manure wastes in an anaerobic lagoon could result in about 120
to 825 kilograms of CH, emissions per head per year. This lev2l of
emissions is on the order of one to 10 times the level of CH, emissions
originating in the dairy cow’s rumen. Additionally. swine and poultry
wastes produce similar amounts of CH, emissions per ton of waste, although
CH, emissions directly from these animals‘ digestive systems is relatively
small.

Although the potential for CH, emissions from waste manure is large, ‘it
is unlikely that this potential is fully realized. Most manure is either
spread as fertilizer, burned (a common practice in developing countries) or
‘allowed to remain in pastures or on ranges. The CH, emissions resulting
from these practices remain to be quantified.4! Manure is probably only
piled up and/or washed into ponds at intensively managed dairy farms and
feed lots where there is no market for manure fertilizer. Even if these
animals are a small fraction of the total animals, the emissions from these
wastes would be significant. For example, if 10 percent of the manure
produced by cattle were to decompose anaerobically, and if these wastes
were converted to CH, at a rate of 0.14 m® per ton of volatile solids added
(a lower bound conversion rate) then on the order of 15 Tg per year of CH,

11 Most manure in pastures and on ranges may decompose aerobically.

However, at least one researcher has detected CH, emissions from this type
of manure (Goreau and Mello (1985)).


9
EXHIBIT 1-4

RELATIONSHIP AMONG CH,, CO, OH, AND 0,

CH4 Emissions
+1.0 CO per CH4 +1.0 CO per CH4 .
-3.5 OH per CH4 +0.5 OH per CH4
0.7 03 per CH4 +2.7 03 per CH4
+1.0 CO2 per CO +1.0 CO2 per CO
-1.0 03 per CO +1.003 per CO

TL CO Emissions —iT

Based on current models, the implications of CH, and carbon monoxide
(CO) emissions appear to differ for areas of low and high nitrogen oxide
(NO) concentrations. In low NO environments (mostly over oceans), CH,
oxidation to CO results in a loss of OH and tropospheric ozone (03). .
Oxidation of CO to carbon dioxide (CO,) further destroys 0,. In high NO
environments (mostly over continents), CH, oxidation to CO increases OH and
0,. CO oxidation further increases 03.

Based on current models, the atmosphere appears to be divided
approximately equally between the two NO environments. Therefore,
increasing CH, abundance will lead to reduced levels of OH and increased
levels of 0,. Additionally, CO oxidation reduces the abundance of free OH
that can enter into reactions, effectively reducing the level of OH.
Finally, a heterogeneous CO oxidation reaction cycle (not shown above) can
also reduce OH levels; the heterogeneous reaction cycle is not well
quantified, however.

Source: Crutzen, Paul J., "Role of the Tropics in Atmospheric

Chemistry," in: Dickinson, R. (ed.), Geophysiology of
Amazonia, John Wiley & Sons: New York, 1987.


28

These trends may be anticipated to continue into the foreseeable future.
Selective breeding continues to produce productivity gains, and techniques
(such as embryo transplantation) are being developed that could improve the
rate of improvement. New methods of improving animal productivity (such as
the use of synthetic bovine growth hormone, BGH) hold the promise of making
significant improvements. Cows injected with BCH produce 10 to 25 percent
more milk than cows injected with a placebo (Fallert et al. (1987) and Mix
(1987)). If the use of BGH is approved, the population of dairy cows
required to produce a given amount of milk will decline. Whether this
decline is realized, for example in the U.S., depends on how the pricing
and subsidy system for milk changes in response to (or in anticipation of)
the use of BGH (Fallert et at. (1987)). Whether the use of BGH reduces CH,
emissions (as opposed to just animal numbers) also remains to be examined,
because feeding practices will also likely change with the use of BGH.

While methods of intensively managing livestock have improved
productivity in developed countries, the productivity of "extensive" animal
management systems (such as village conditions in developing countries and
range animals), has not changed significantly in recent years. Many, if
not most, animals in developing countries continue to be managed in small
herds (1, 2, or 3 head per household) with traditional practices. Animal
nutrition and health remain well below the levels seen in developed
countries, and hence productivity (measured by intensive management
standards; i.e., in terms of the amount of milk and/or meat produced per
animal) remains low. Consequently, increases in the demand for animal
products in some developing nations have been met through increases in
animal numbers. These increases probably imply increased CH, emissions from
this source.

In many developing countries animal feed resources are constrained. In
such situations, animal numbers in the countries cannot increase, even as
human populations have increased. The growing demands for animal products.
(mostly milk products) in these countries are partially met through imports
(which are limited by available economic resources), and largely go unmet.

Development projects undertaken by the World Bank and others have among
their objectives improvements in animal productivity in developing
countries. For example, the largest ongoing dairy development project is
"Operation Flood" in India. Funded through the sale of EEC-donated dairy
products and World Bank loans, this program has among its objectives to:
improve transportation links between rural milk producing areas and urban
population centers; improve storage and processing facilities; establish
marketing cooperatives; develop cattle feed plants; and improve genetic
characteristics of dairy cattle. .

To the extent that projects such as Operation Flood are successful in
increasing animal productivity, they likely reduce the rate of CH, emissions
per amount of product (e.g., milk) produced. Whether they reduce total CH,
emissions is less clear.


280

are much more abunaant than commoniy
assumed. due to inadequate counting methoas.
Consequently, more work on the potential CH,
Production by invertebrates 1s certainiy justified.

Our upper estimate of 28 Tg for inverteprate
Primary consumers overiaps to some degree with
global production estimates for termites «includ:
ing herbivorous species, wood- sna dung feeders.
soil feeders and others), which range trom 2-5 Te
(Seiler et al.. 1984) up to 150 Tg (Zimmerman et
al., 1982). The most recent study by Fraser et al.
(1986) suggests an annual production of 6-42 Tg
with an average of maybe |4 Te.

So far we have primanily been concerned with
Primary consumers. Most of the piant material
Produced each year by vegetation 1s lost to the
litter layer and subsequently decomposed by a
large variety of organisms. A survey through the
literature on sou biology has given no hint on
methane production in soils apart from anaerobic
environments and termite mounds. Swift et al.
(1979) report that certain cockroaches and dung
beetles rely upon symbiotic bacteria and
Protozoans for the digestion of structural
Polysaccharides. This could imply possible
methane production as in the case of termites.
Generally, methane can most propably only be
Produced by macrofauna consumers of plant de-
“Uritus (primary saprotrophs) as these are the only
ones with true anaerobic digestive tracts. Organ:
tsms beloneine to mesalauna sre probably too
mail in size to develop anserobic conditions in
their guts (Grewe. personal communication). The
macrofauna plays 3 major réle in the tropics and
declines in importance towards the poles. In
colder climates. major breakdown of organic
compounds 1s accomplished by microfauna and
fungi (Switt et al. 1979), which implies a gradi-
ent of decreasing methane production potential
from soil fauna from the tropics to the poles.

Earthworms have 2ttained special interest in
the past for their ameliorating effect on sails.
These animuls feea on detritus together with
mineral particles and attain huge turnover rates
of matter within the soil. Their guts produce 2
Tavourable environment for a diverse population
of micro-organisms. However. ce:lulose 1s very
badly digested (Brauns. 1968) cad methano-
zenesis 1s Not reportes. Measurements on acrocic
souls of temperate anc tropical zrassland sites

P. J. CRUTZEN, 1. ASELMANN. AND W SEILER

(Seiler et al.. 1984,

decomposition in the

soul-dwelling organisms Produce methane. i:

seems likely that this 1s teadily decomposed with-
1m the soil and does not escape to the atmosphere.

1986) all indicate methane
soul and no production. If

9. Current and past CH, production from
domestic animais

Data on the estimated global methane
Production by domestic animals and humans in
1983 ure summanzed in Table |. Total methane
release to the atmosphere 1s about 74 Tgyyear
with an esumated uncertainty of about 15°. By
far the largest contnibution. about $4 Tg, comes
from cattle. About 40°; of this emission occurs in
the developing world. Next in importance come
buifalo and sheep, which produce about 6 Tg and
7 Tg CH, per year. fespectively. Goats and
camels produce 2.4 Tg CH, and | Tg CH,
annually. Non-ruminant, domestic animals each
year emit about 2.6 Tg CH, to the atmosphere.
The human contribution 1s only about 0.2 Tg
CH, per year. In comparison with the estimated,
global methane emission of 73 Tg by domestic
animals in the year 1983. the input by wild
ruminants of 2-6 Tg 1s relatively smail.

Because of the growing world population of
humans and ts growing food demand. the
Populstion of domesuc animals has ulso in- :
creased considerably during the list century.
leading to an increase in global methane
Production rates. According to data published by
Muthail (1892) tor the end of the last century and
data for the first half of this century (US
Department of Agriculture. - 1936-1970). the
world cattle population has increased from 310
Mullion in 1890 to 640 million in 1920-1925. and
740 million in 1930-1945. The corresponding
figures for sheep are 590 million. 645 mullion. and
TES mullion. Fespectively (Table 4). According to
the available statistics. the sheep and cattle popu-
lations show similar trends for tne period 1920-
1960. bur large duferences for 1390-1920. which
'8 Prodably inurcative of less reliable statistical
information trom the early period. |

More Cetailed staustical information 1s avail:
able tor the me gered ater 1930, paruculariy
due to the work by the Foua 2nd Agneultural
Organization ot the Cited Nations (FAQ, 1973,

Tellus 5B 19N@), Sot


METHANE PRODUCTION BY ANIMALS 273

horses and the elephant showea CH, yreids in the
range of 1.5%5-3%,.

Blaxter and Clapperton (1965). in analysing
numerous data on methane proauction by cows
and sheep have shown that at maintenance.
methane yields increased from 7.5°% to 9°% when
the digestibility of the feed was raised from 65°%
to 95%. The methane yields (6.5-7°,) were inde-
pendent of the digestibility at a feeding level of 2
x maintenance and decreased from 0°; to 5° at
3. x =maimtenance when the feed digestibility
changed from 60°; to 90°. Similar results were
reported by Van der Honing et al. (1981) who
observed methane yields on 5-6.5°; for dairy
cows fed on 3.1-3.5 x maintenance. Wainman et
al. (1978) measured CH, yields of 7.9°% from
steers fed on 1.5 x maintenance and a 77°;
digestible diet. Krishna et al. (1978) estimated
higher CH, yields of 9°, in Indian cattle fed on a
slightly above maintenance diet and low quality
feed.

Published methane yields from sheep show a
somewhat larger range of values. Murray et al.
(1978) found CH, yields to mse from 3.5°%% to
5.6% with increasing feed intake in Merino ewes
fed on protemerich lucerne chaff with a
digestibility of 63°%. Kempton and Leng (1979)
observed methane yields of 5.4-6.4°, in growing
lambs. being highest on low protein diets. while
Seeley et al. (1969) measurea 8.2-9.7°% in adult
sheep ted on ryegrass hay at maintenance level.

Non-ruminating, well-nourshed pigs have
much lower methane yields (0.4-0.9°,) which
seem to be indepencent of feed mixture
(Schneiaer and Menke. 1982), but pigs given low
Quality feeds may be expected to show CH, yields
between 1°, und 2°, (H. Stemngass. personal
communication).

From these data. 1 becomes apparent that the
calculation of the global methane release trom
domestic animais requires consideration of differ-
ent animal management ana feeding schemes.
Published information 1s scarce. We have there-
Tore also mage considerable use of information
which was kindly provided to us by experts
througn personai communications.

3. Methane production by cartle

In the US. there sre 3 types of cattle: cairy
-ows, beet cattle on reed. ana cattle on range. In

Tellus 33B (1986). 3

Europe and in the USSR. range cattle are rare.
ina the rearing of dual-purpose cattle for dairy
=na beef proauction ts common practice. In other
sountnies like Australia or Argenuna. cattle are
Kept primaniy on range and dairy cows are
reiauvely less numerous.

Because cattle are fed at different levels of
energy intake and quality of food in different
Parts of the world. we will next present some
detailed analyses for the US. West Germany and
India. From these data. we will extrapolate to
other pasts of the world to armve at global
estimates of methane production.

The average number of feed units (1 feed unit is
the digestible energy contained in | pound of
corm) consumed in the US by milk cows (includ-
ing heifers), cattle on feed. and cattle on range
sre 10150. 6650 and 4800 per animal per year,
respectively (G. Allen. personal communication).
With an energy content of 6.57 MJ per teed unit.
this converts to 230 MJ. 150 MJ and 110 MJ of
daily gross energy intake, which corresponds to
about 2-3, 1.75 and 1.3 = maintenance. Using
Blaxter and Clapperton’s (!965) methane yields
of 5.5%, 6.5%2 and 7.5%% of gross energy intake
for these categories. and an energy content
ot $5.65 MJ/kg CH, the annual methane
Production per individual in the atoremenuoned
categories arc 84 kg. 65 kg ana $4 ke. respective-
ly. The US cattle population is made up of 10°
dairy cows, 12.5°, beet cattle on teed ana 77.5°%
cattle on range (Food and Agricultural Organiza-
uion of the United Nauons (FAQ). 1984). The
mean methane production by cattle in the US is
theretore equal to 58 kg per animal per vear.

In West German staustics (Statstisches
Bundesamt. 1984), cattle are grouped in age
classes: younger than 6 months (2.7 million), 6 to
24 months (6.2 million) and older than 24 months
(6.5 million). The latter are subdivided into dairy
cows (5.4 muilion), and hetfers or steers (1.1
mullion).

The feeding level for dairy- cows in highiv
Proguctive stages 1s 3 to 3.5 = maintenance.
equivalent to 300-320 MJ per day te.g., Van ger
Honing et al.. 1981. Kircheessner. 1985), but
mean gross energy intake over a year's period. 1s
around 260 MJ per day (H. Steingass. personal
communicauon). With a methane yteld of $.3°%,
se caiculate a yearly CH, proauction of 95 ke per
vairy cow.



10;
EXHIBIT 1-5

ESTIMATES OF METHANE EMISSIONS
(Tg of CH, per year)*

Time Trend of Emissions -- Seiler:

CHA Production Rates (Te CHM per Your)

30

CG] wpe scroes:
iemaas tasting, com ming,

300 ed natal ges Garbutcn
TERE ote ogee

ao fh
(TI) swore

200 F
Paddy Fiekie

we

100

or fe

° :

1980 1080

[RQ Atioperic sources: 121-177 Tp
Biomass buming, co! mining,
‘and natural gas dissibuten,

HEB ote spore: 15:35 15
[[l) Seema ntarines: 25-7079

RNY Paddy Feiss: 70-170 Tg

Puminanes: 70-100 Tg,

* 17g = 10% grams

Sources:

Seiler, W., "Contribution of Biological Processes to the
Global Budget of CH, in the Atmosphere," in: Klug, M. and C.
Reddy (eds.), Curre: erspectiv icrol Ke! .
1984, pp. 468-477.

Bolle, H.-J., W. Seiler and B. Bolin, "Other Greenhouse Gases
and Aerosols: Assessing Their Role for Atmospheric Radiative
Transfer," in: Bolin, B., B.R. Doos, B. Warrick and D. Jager
(eds.), e_Greenhouse Ef; imatic e Eco: ,
John Wiley & Sons: New York, 1986, p. 163.


METHANE PRODUCTION BY ANIMALS

In the paim savanna at Lamto. Ivory Coast.
the main consumers are fungus-growing termites
(0°, of NPP). followed by grasshoppers (0.4°;)
anu small rodents. mainiy voles (0.25°%). Large
herotvorous ungulates play no major role
(Lamotte and Bourliére. 1983). Certain ants ana
caterpillars are also important consumers but
quanutatve information on their réle is not
avatiable.

In the Féeté Olé savanna in Senegal. termites
have also been found to be major harvesters of
plant ussue. consuming 10°; of the NPP (Josens.
1983). Gillon (1983) states that at this site. grass-
hoppers and caterpillars may consume as mucn as
grazing mammals, but gives no data on their
plant consumption.

In undisturbed temperate grassiand sites,
pmmary consumpuon by invertebrate herbivores
18 0.5-9°, of the above ground NPP, being lowest
in poor. unproductive sites and increasing with
productivity (Andrzejewska and Gyillenberg,
1980). Wiegert and Evans (1967) determined an
upper limit of 12%% for plant consumption by
herbivores in an old grass field site in South
Carolina. mainly by invertebrates. Only 1°; was
consumed by vertebrates. mainly ficld mice and
savanna sparrows.

In tropical forests. Janzen (1983) considers
defoliating animals as the most important plant
consumers. mainly moth larvac. caterpillars.
beetles and other invertebrates. Jordan (1983)
sites data. indicating that usually no more than
3+3°, of the teaf biomass is harvested by insects.
In nutrient deficient. low-production forests. the
consumption may drop to 2°;.

Herbivorous vertebrates are not important as
primary consumers in tropical forests. Owen
(1983) gives a very low figure of only 72 ke:km:
for the density of herbivorous mammals at the
Tano Nim Forest (Ghana). consisung of 3
ungulates and 7 pnmates. These low figures are
also confirmed for South Eastern tropical rain
forests (Whitmor, 1984). In contrast. in some
South American forests. larger populations of
siotns and t2pirs may be founa that may consume
4a considerable fraction of slant production with-
in the forests (Janzen. 1983). Rodents are also
present in tropical forests but apart from some
Population figures. no energy intake data ure
available.

In temperate forests. Frimary consumption by

Teius 35B (1996). 54

x9

‘Msects 1s at most 10-15%, of the above-ground
NPP (Remmert. 1980). Franklin (1970) cues
some figures tor broad-leaved trees. which range
trom 3-8°,. However, these data contradict those
trom an intensively investigated forest site in the
North-east US. in which Gosz et al. (1978) found
less than 1°; of the total NPP, including roots. to
be consumed by herbivores. In Approximate or-
der of importance. these are chipmunks, mice.
foliage-eatng insects. birds. deer and hares.

Consumption figures from boreal forests or
tundra sites are not available. Remmert (1980)
gives a rough figure of 1-2°% for consumption by
vertebrates at Spitzbergen (Norway), but gives no
estimates for invertebrates.

Summarizing the above widely different data.
it appears that mayor consumers in natural habi-
(ats are invertebrates, mainiy insects. and to 3
much lesser degree small herbivores. If we as-
sume that small herbivores (mainly rodents and

lagomorphs. i.e.. hares, rabbits, etc.) in natural
habitats consume less than 1°%

“e Of the global
NPP, with a CH, yield of 1.5%¢ Giohnson. person-

al communication), we calculate for this Group of
animals an upper tims of methane production of
2-3%% Tg per year. :

An estimate for methane Production by
mvertebrates 1s even more speculative. So fur.
methane production has only been measurea mn
termites (Zimmerman et al.. 1982; Rasmussen:
and Khalil, 1983: Setler et al.. 1984: Fraser et al:.
1986) und in wood-boring lurvae of beettes
(Bayon. 1980) which utlize symbiotic micro-
organisms in their digestive tract to break down
Cellulose. According to Swift et al. (1979). most
insects harbour flagellates in their guts for cellu:
lose digestion. Thus it is likely that insects and
Probably other invertebrate primary consumers
also harbour methanogenic Muicro-oreanisms.

Measurements trom different genera of ter-
mites indicate methane yields of less than 0.01
to 1.5% (Zimmerman et al.. 1982: Khalil and
Rasmussen. 1983: Seiler et al.. 1984). If we agoot
this range for all invertebrate primary consumers.
the consumption of 6°; of the global NPP ty
herbivorous invertebrate Probably couid proauce
at most 23 Tg annually. However, this upper
limit estate 1s speculative as long as no data on
Possible CH, production yields by insects other
than termites are available. According to Owen
(1983), Plant-teeding insects in tropical forests


184

Rasmussen. R. A. and Khahl. M.A. K. 1983. Giobal
Production of metnane by termites. Vuture 301, 700-
702.

Remmert. H. 1980. Ecolugy. 4 textbook. Springer.
Berlin—Heidelberg—New York. 289pp.

Ritzman. E. G. and Benearct. FG. 1938. Nutrinonal
physiology of the adult ruminant. Carnegie Instuution.
Washington D.C.. p. 14-30.

Sadlew. R. M. F. S. 1982. Energy consumption ana
subsequent parutioning in lactating black-tailed deer.
Can. J. Zovl. 60. 382-386.

Schnerder, W. and Menke. K. H. 1982.
Untersuchungen uber den energetischen Fuuterwert
von Melasse-Schnitzein in Rationen tur Schweie. Z.
Tierphysiologee, Tierernahrung und Futtermutetkunde
48, 233-240 in Germani.

Schulz, E. 1972. Phrnologie. Urban and
Schwarzenberg. Miinchen—Beriin—Wien. p. 84 (in
German).

Seeley. R. C.. Armstrong, D. G. and MacRae. J. C.
1969. Feed carbohydrates—the contnbution of the
end-products of their digestion to energy supply in
the ruminants. In: Energy metabolism of farm anumals.
Proc. 4th Symp. Warsaw., Poland. Sept. 1967, eds.
K. L. Blaster. J. Kiclanowski. G. Thorbek. Onel
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Sealer, W. 1983. Contribution of biological processes to
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Current perspectives in microbial ecoloey, eds. M. J.
Klug and C. A. Reddy. Amencan Society for Micro-
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Setier, W. Conrad. R. and Schartfe. D. 1984 Field
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the atmosphere ang measurements of methane up-
take by tropicai sosis. J. Atmos. Chem. 1, 171-186.

Seiler, W. Conrac. R.. Scharrfe. 0. ana Giehl. H.
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March 16-21. 1986.

Sheppard. J. C.. Westberg. H.. Hopper. J. F.. Ganesan.
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P. 3. CRUTZEN, 1. ASELMANN AND W. SEILER

Sinciawr, A. R. E. 1975. The resource timitation of
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Staususches Bundesamt. 1984. S:ausnsches Jahrbuch
der Bundesrepublik Deutschiand. Kohthammer. Swuu-
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Teilus 35B 11986), 3S


A-14

° Horses: The CH, production rate for horses cited most often from
Ritzman and Benedict's study is for the 1500 1b (680 kg) Percheron
mare (106 g CH,/day/head). Blake asserts, however, that a
Percheron is 50 percent larger than the average horse and consumes
more than twice as much organic material. Blake suggests that the
900 1b (408 kg) trotter, with a much lower CH, production rate of
28 g CH,/day/head, is a better representative of the average horse.

° Sheep and Goats: CH, production rates for sheep and goats is taken
directly from Ritzman and Benedict's study.

Blake multiplied population data from the 1970 FAO Production Yearbook
(1971) by the adjusted emissions rates to get yearly world CH, production.
Blake estimates CH, production in cattle, sheep, goats and horses to be 62,
5.5, 1.5, and 1.2 Tg, respectively. The sum of these, 71 Tg, is assumed to
estimate the lower limit for CH, production by herbivores.

Herbivorous Animals and Insects. Woodwell (1970) reports that

approximately 1.1 x 10!” g/year dry plant matter is produced on land, about
10 percent of which is eaten by domestic animals, herbivorous insects
(i.e., termites) and wild herbivores. Ehhalt (1974) asserts that an upper
limit estimate of CH, production by animals may be. determined by assuming
that all of the 1.1 x 107° g/year dry Plant matter consumed is converted to
CH, with the same efficiency as cattle, 2 Percent, to give 220 Tg CH, per
year. Blake asserts that of the 1.1 x 10’ g/year dry plant matter
consumed, 43 percent is utilized by cattle. Therefore, a better estimate
of CH, production would assume that 43 percent of the dry plant matter is
converted to CH, with a 2 percent efficiency and the remaining 57 percent is
* converted with a 1 percent efficiency. These assumptions result in Blake's
upper limit estimate of CH, production from herbivores of 160 Tg, 95 Tg from
cattle plus 63 Tg from other herbivores. Note that Blake's 95 Tg per year
estimate for cattle using this method is larger than Blake’s 62 Tg estimate
based on the data from Ritzman and Benedict. :

LERNER ET AL.

Lerner et al. (1988) present a global database of animal population
densities and associated CH, emissions. Population statistics were compiled
from FAO Production Yearbooks and other sources. Published CH, production
rates were applied to the animal populations to obtain a global —
distribution of annual CH, emissions by animals.

Animal Population Statistics. Data on animal populations in each

country were obtained from FAO Production Yearbooks. In addition, data on
animal populations for the political subdivisions of the seven largest

countries were obtained from other publications: Australian Encyclopedia,
as Austr. esou: , Anuario Estatistica do Brasil, Livestock and

Anim odus tatistics (Canada), Agricultural Statistics of the People's
Republic of China, Agriculture in Brief (India), Agricultural Statistics


B-3

B.3 SCENARIOS

To examine future global warming, estimates and assumptions are
required regarding future emissions of greenhouse gases. These emissions
will necessarily be very uncertain due to uncertainties in the main driving
factors of the future emissions, including: global economic growth,
population growth, fuel prices, land use, and technological change.
Therefore, the Atmospheric Stabilization Framework (ASF) was developed by
EPA to represent the structural relationships among the key activities that
result in important emissions. By using plausible estimates and
assumptions in this framework, reasonable scenarios of greenhouse gas
emissions can be produced.

The two scenarios used here were developed for the EPA Report and are
referred to as the Rapidly Changing World (RCW) and Slowly Changing World
(SCW) scenarios. These two scenarios provide a range of assumptions about
the future activities that will affect global warming. The main
assumptions associated with these scenarios include the following:‘

SLOWLY _C! IGING W RAPIDLY CHANGING WORLD
Slow Economic Growth Rapid Economic Growth
Continued Rapid Population Growth Modest Population Growth
Minimal Energy Price Increases Modest Energy Price Increases
Slow Technological Change Rapid Technological Change
Carbon-intensive Fuel Mix Very Carbon-intensive Fuel Mix :
Increased Deforestation Modest Deforestation

Of interest for this analysis is that although the SCW scenario has overall
lower projected emissions of key greenhouse gases than the RCW scenario, it
has larger methane emissions from ruminant animals. Exhibit B-1 shows the
methane emissions from the two scenarios, and methane emissions from
ruminant animals.

As shown in the exhibit, total methane emissions are larger in the RCW
scenario. The larger emissions are driven primarily by emissions from fuel
production and other energy-related activities. As also shown in the
exhibit, methane emissions from ruminant animals are quite similar in the

‘ The interested reader is referred to the full EPA Report for

additional details on these scenarios.


15

livestock have been identified, indicating that some reductions, and
possibly large reductions may be feasible. A major goal of this
assessment, therefore, is to identify options for achieving such a
reduction in livestock-related emissions. These options could subsequently
be evaluated.

Such an evaluation would include:

°

Improved Characterization of Emissions. Emissions rates from
various animals and animal management practices (particularly in
developing countries) must be better characterized. Improved
emissions estimates will enable emission reduction options to be
better evaluated.

Evaluation of Impacts. Options for reducing emissions must be
evaluated in terms of: impact on emissions; cost; ease of
implementation; and impact on agricultural productivity. Given
the obvious importance of managed ruminants throughout, the world,
and their unique ability to convert low quality inputs (e.g.,
agriculture byproducts that cannot be digested by humans) into
useful products, potential technical and management options for
reducing CH, emissions must be evaluated within the context of the
overall agricultural, social, and economic systems in which they
would be implemented. .

Assessment of Methods of Implementation. Institutions and
organizations involved with agriculture and agriculture products.
must be involved in implementing emissions reduction options.

_ Similar analyses are required for the other sources of CH, emissions.
For example, improved estimates of CH, emissions are required in order to
evaluate whether additional gas recovery during coal mining is warranted.
Continued improvements in our understanding of the global sources and sinks
of CH, are required in order to have confidence that the levels of emissions
reductions achieved over time are sufficient for stabilizing atmospheric
concentrations.


METHANE PRODUCTION BY ANIMALS

1982 and 1984). According to these data. during
Jast (wo decades. the world’s cattle ana sheep
pupuiations have grown by 0.8%; and 0.6°, per
year. respectively, reaching figures in 1983 of
{22S x 10° for cattle and 1137 x 10° for sheen.
Similar annual increases in global population
numbers are found for pigs (1.4°%), butfalos (1°,),
goats (1.2°,) and camels (0.5%). The Population
of mules and asses stayed about constant. while
that of horses showed a slight decline of 0.25°,
per year. According to the available staustics.
since 1960. the growth rates of the cattle and
sheep populations have slightly declined.

The temporal trends of global CH, emission by
ruminants are not only dependent on their Popu-
lations but ulso on quality and quanuty of feed
intake. In the developed countries. the average.
individual feed intake has increased during the
fast 20 to 30 years, although the corresponding
increase in CH, emission may have been com-
Pensated to some extent by declining CH, yields
due to higher teed quality. In the developing
world, both feed intake and quality may have
dechned.

To estimate individual methane production
fates priur to 1983. we assume that in 1890.
average methane yields in the world were about
equal to current yields in the developing world.
anile between 1890 and 1980. we adopt 4 linear
srowth in individual CH, emission rates. With
$ ussumation. the CH, release trom cattle has
more tnan uuadrupied during the lust century
trom It Tz in 1890 to $4 Ty in 1983. CH,
emission by sheep has grown from 3 Tg to 7 Ty
during the same period (Table 4). Information on
dechining Populations of wild ruminants ts not
avaiable. but they can certainiy not have been
suificient to compensate substanually for the
growth im methane emissions by domestuc
ammals. Altogether. our analysis inaicates that
tne total unnual CH, emission from all animals.
including wiid ruminants. has increased trom 2!
Tz 1n 1890 to soout 73 Tg in 1983.

10. Conciusions

Methane 1s produced by the amucrobic fermen-
‘aon of orgamie matter in the rumen and lower
tof domestic and wild animals. The CH,
rission rate fer animal 1s depenuent on yuauty

i381

and amount of feed intake. Bused on data that
#f€ presentiy available. we estimate that about 5-
‘1, of the gross energy intake by ruminants 1s lost
to methane production. Lower methane yields in
the range U.S-3%, are derivea for other comestic
animals such as pigs. horses. etc.

The current global CH, emission by domestic
and wild unimals is estimated to be 78 Teyear.
From this. almost 80°, or about 60 Teg-year.
somes trom cattle und butfalos. The rest is pro-
duced by sheep (7 Tg-year), wild ruminants (2-6
Tw-year). and others. About 40°; of the total CH,
Produced by domestic animals is emitted in the
developing countries, mostly in Asia. followed by
South ‘America and Africa. The main source
region for methane trom cattle in the developed
world 1s North Amenica (11 Tg year) followea by
Europe (3 Tg year) and the USSR (7 Tg year).

Methane production by domestic and wid
animals constitutes about 15-25°; of the total
tropospheric CH, input. recently estimated by
various authors to be in the range of 300-500
Tyiyear (Khalil and Rasmussen. 1983; Crutzen
and Gidel. 1983: Seiler, 1984). Production by
animals represents one of. the most important
individual sources within the tropospheric CH,
sycle. It 1s about two times larger than the
Production trom coal mining and natural yas
leaks (Setier, 1984. Crutzen. 1986: Bolle et al.
1986). The oniy emissions which could be lareer
are those trom the anaeroore cecay ot organic
matter in rice fields snd natural wetlanus.
Methane retease trom rice paddies May be aoout
70-130 Ty year. if information obtained in
Itahan rive nelds can be extrapolated to tropical
conditions (Holzaptel-Pschorn and Seiler. 1986)

The total emission of CH, by domestic and

wild animals has increased from about 21 Tein
1990 ty 46 Ty in 1940 ana 78 Ty in 1983. mainiy
due to crowing populations of cattle. burfalos and
sheep. Accoraing to these figures. the mean rate
of increase in CH, emission by Comestc and wild
animals curing the last 43 years has teen | 1°,
per vear.
We have estimated a tentative upper limit ot
about }) Tz CH, emission ger vear trom other
Tauna. especially insects. However. this topie
requires -aditional = researcn. Finally. the
Prouuction of CH, in humans sppears to be
negugreiy low. much less than 1 Tz year.



20
EXHIBIT 2-2
ANNUAL METHANE EMISSIONS FOR COMBINATIONS

OF FEED INTAKE AND DIGESTIBILITY LEVELS
(kilograms per year per animal)

Level of Intake

1.0 1.5 2.0 2.5 3.0
Digestibility
50 57. 97. NA NA NA
60 52. 85. 117. NA NA
70 NA 77. 102. 123. NA
80 NA NA 91. 105. 114.
90 NA NA 82. 92. 94.

Estimates are based on CH, yield estimates from Blaxter and Clapperton
(1965) and feed characteristics from NRC (1984). Estimates are for a 500.”
Kilogram animal with feed energy maintenance requirements similar to that
described in NRC (1984) for U.S. beef cattle. Energy requirements vary by
breed, sex, and climate. Smaller animals (such as those found in many
parts of developing countries) would have lower energy requirements, and
consequently lower CH, emissions for any given combination of level of
intake and digestibility.

NA = Not Applicable. One would not normally expect to observe animals
at these combinations of feed intake levels and feed digestibility.


49

FAO, FAO Production Yearbook, Food and Agriculture Organization of the
United Nations, Rome, selected years.

FAO, Livestock Numbers Database Printout, Food and Agriculture Organization
of the United Nations, Rome, Italy, 1988.

Goreau, T. and W.Z. Mello, "Effects of Deforestation on Sources of
Atmospheric Carbon Dioxide, Nitrous Oxide, and Methane from Central
Amazonian Soils and Biota During the Dry Season: A Preliminary Study,"
Proceeding of the Workshop on Biogeochemistry of Tropical Rain Forests:
Problems for Research, Sao Paulo, Brazil, World Wildlife Fund-U.S., Centro
de Energia Nuclear na Agricultura (CENA), and Universidade de Sao Paulo,
1985, pp. 51-66.

Hansen, J., et_al., "The Greenhouse Effect: Projections of Global Climate

Change," in: Titus, J.G. (ed.), Effects of Changes in Stratospheric Ozone
and Global Climate, U.S. EPA and UNEP: Washington, D.C., August 1986, p.
206.

Hill, D.T., "Methane Productivity of the Major Animal Types," Transactions
of ASAE, 1984, p. 530.

Hoffman, J.H., and M.J. Gibbs, Future Concentrations of Stratospheric
Chlorine_and Bromine, U.S. Environmental Protection Agency: Washington,
D.C., EPA 400/1-88/006, August 1988.

Khalil, M.A.K., and R.A. Rasmussen, "Trends of Atmospheric Methane: Past,

Present, and Future," in: din, of t S: d_Other
Greenhouse Gases, Brussels, Belgium, November 1986.

Mix, L.S., "Potential Impact of the Growth Hormone and Other Technology * ‘on
the United States Dairy Industry by the Year 2000," Journal of Dairy”. ~
Science, Vol. 70, 1987, pp. 487-497.

Moe, P.W. and H.F. Tyrrell, "Methane Production in Dairy Cows," Journal of
Dairy Science, Vol. 62, 1979, pp. 1583-1586.

NMPF, Dairy Producer Highlights, National Milk Producer Federation,
Arlington, Virginia, 1987. .

NRC, Nutrient Requirements of Beef Cattle, National Academy Press:
Washington, D.C., 1984.

NRC, Nutrient Requirements of Dairy Cattle, National Academy Press:
Washington, D.C., 1988.

, Preston, T.R. and R.A. Leng, Matchin, minant Product: th
Available Resources _in the Tropics and Sub-tropics, Penambul Books,

Armidale, New South Wales, Australia, 1987.


METHANE PRODUCTION BY ANIMALS

the global human population. ihe reizase of
methane in flatus gas is estimat-a to be about 0.1
Telyear. These small me:aane production
numbers are in agreement with other stugies
(Steggerda, 1968; Marthr:sen and Fleming.
1982).

7. Methane release from wild ruminants and
other large herbivores

The global procuction of CH, from wild
ruminants is diffict to estimate due to lack of
sufficient data or animal populations and feed
intake. Some opulation assessments exist.
however. for ce*tain regions of the world and can
be extrapolated to global conditions. McDowell
(1976) gives = population figure of 27 million for
wild ruminants in the northern temperate regions
(except China). These ruminants are comprised
mostly of deer and moose. In Table 2, we have
listed theie mean body size (Nowack and
Paradiso, 1983) and feed intake (c.g. Nystrom,
1980: Sadieir, 1982). As wild ruminants live
entrcly on roughage and herbs near maintenance
leve.s, we assume a CH, yield of 9%. Using these
figures. we obtain a total release of 0.4 Tg of
rethane by wild ruminants in the temperite
egions, mostly from deer.

Information on populations and mean body
weights of wild ruminants in the Serengeti is
summarized in Table 3 (Houston, 1979: Western.
1979). The total population of about 2 million
mainly consists of gazelle and wildebeest. Data
on gross energy intake in Table 3 have been
calculated from formula (1) for the basal meta-
bolic rate. multiplied by a factor of 2 to give the

17

likely gross energy requirement of free living
ungulates (Moen, 1973; Eltringham, 1974).
Agiin, 9° of the gross energy intake is assumed
to be released as methane. With this informauon,
the CH, production in the Serengeti from
ruminants is estimated to be about 0.02 Tg per
year. Assuming the CH, production in the
Serengeti to be representative of global
conditions, the total CH, production by the wild
ruminant population of 100-500 million in the
subtropical and tropical regions (McDowell.
1976) may be estimated to be of 1-5 Tg per year.
Together with the contribution from ruminants in
the northern temperate regions, the annual CH,
Production from wild ruminants in the world
may, therefore, be equal to 2-6 Tg per year which
is small compared to the CH, production by
domestic animals.

Statistics on methane production by other
large, non-ruminating herbivores in the Serengeti
are likewise listed in Table 4. The most important
contributions come from zebras and elephants.
The total methane production is less than 10% of
that by the ruminants. Altogether, non-
ruminating large herbivores are a negligible
source of atmospheric methane.

8. Methane emission by other fauna

. The consumption of plant matier by the large.

wild herbivores considered so far. sums up to 50-
200 Tg dry matter. The average consumption of
plant matter by herbivorous fauna is estimated to
be 7% of the net primary productivity (NPP) of
natural ecosystems. or about 7000 Tg dry matter
(Whittaker. 1975). Consequently, relatively small

Table 2. CH, production by wild ruminants in temperate northern regions

Mean body Gross energy CH, production CH, production
Populations weight intake per individual total -

Species (x 107] (ke) (MJ/day)} {kg year] (Tg-year}
Moose. elk 8.5 350 33 3 0.03
white and black-tailed

deer. mule deer, red

deer. reindeer. caribou 220 90 6 5 0.33
toe deer +0 13 5 3 0.01
Total 268 - - - 0.37

Tellus 38B (1986). 3-3


32

EXHIBIT 3-1

STEPS FOR IMPROVING EMISSIONS ESTIMATES

AREA OF
INVESTIGATION

Characterize animal
populations along
characteristics that
affect CH, emissions.

Develop and evaluate
measurement
techniques.

Perform CH, emissions
measurements.

Model Development.

COMMENTS

Good animal population data are required. Defining
categories of animals with similar characteristics
will facilitate subsequent analysis. The numbers
of animals are well described for most developed
countries. However, the majority of ruminants are
in developing countries where animal numbers are
least well quantified. Additionally, data on
animal characteristics (including animal waste
management systems) are also required. These data
have not been collected in a comprehensive form for
the major populations of animals in the world.

Existing methods of measuring CH, emissions
directly from animals and from related sources need
to be evaluated. New techniques are required to
measure emissions rates from grazing animals and
animals in developing countries.

Adequate measurements of emissions rates from
animals in developing countries appear to be
lacking. Additionally, measurements from some
categories of animals in developed countries and
from animal wastes are lacking. The differences in
CH, emissions among individual animals, and the |
factors that contribute to these differences (such
as differences in the rumen microbial environment)
remain to be measured and understood.

The animal population characteristics and the
emissions measurements may be used for purposes of
developing a model of regional and global
emissions. The model may also be a useful tool for
identifying the implications of alternative
approaches for reducing emissions.


2. OVERVIEW OF METHANE FROM LIVESTOCK

2.1 SOURCES OF METHANE EMISSIONS

Among livestock, the ruminants (i.e., cattle, buffalo, sheep, goats, and
camels) are the major emitters of CH,. The rumen, a large "fore-stomach,"
is the unique physiological characteristic of ruminants that provides the
opportunity for CH, to be created within the animal. Within the rumen, over
200 species and strains of microorganisms have been identified, although a
smaller number (10 to 20 species) are believed to play an important role in
digestion (Baldwin and Allison (1983), p. 462). Rumen methanogenic
bacteria are the source of CH, produced within ruminants.

‘To date, methanogenesis within the rumen of ruminants has been the
primary focus of discussions regarding CH, production related to livestock.
However, ruminants are generally managed as part of an overall systen,
which may have other parts that also contribute to CH, emissions. The
principal system component identified that may contribute the CH, emissions
is the disposal of manure. Significant CH, emissions have been measured
from lagoons used to dispose of animal wastes, including non-ruminants,
such as swine and poultry (Safley and Westerman (1988)).

METHANOGENESIS WITHIN THE RUMEN

Rumen methanogenic bacteria are generally a very small fraction of the
total population of microorganisms in the rumen. Although they can convert
acetate (a fermentation product produced in the rumen) to CH, and C02, this
pathway for CH, production in the rumen is believed to be of minor
importance in animals fed adequate and balanced diets (Baldwin and Allison
(1983), p. 469). Instead, the conversion of hydrogen (H,) or formate and
CO, (produced by fermentative bacteria) is believed to be the primary
mechanism by which methanogenic bacteria produce CH, in ruminants.

The creation of CH, in the rumen represents energy which is subsequently
not available to the host animal for maintenance or growth. Methods of
reducing methanogenesis in ruminants have been investigated as part of the
overall attempt to improve the efficiency of rumen metabolism. However,
methanogenic bacteria play an important role in the complex ecology of the
rumen, so that simply eliminating or suppressing the activity of
methanogens in the rumen will not "free up" energy that can be used by the
animal. . °

The extent of methanogenesis in individual ruminants has been estimated
by various authors. The rate of methanogenesis can be described in terms
of a “methane yield," which is defined as the amount of CH, produced as a


A-10
EXHIBIT A-4

ESTIMATES OF METHANE EMISSIONS FROM ANIMALS
REPORTED BY CRUTZEN ET AL.

ANIMAL TYPE AND REGIONS POPULATION CH, PRODUCTION CH, PRODUCTION BY
(Million) PER INDIVIDUAL TOTAL POPULATION
(kg/year) (Tg/year) **
Cattle in developed countries, 572.6 55° 31.5
Brazil and Argentina
Cattle in developing 652.8 35 22.8
countries:
Buffalos 1462.1 50 6.2
Sheep in developed countries 399.7 8 3.2
Sheep in developing countries 737.6 5 3.7
and Australia
Goats 476.1 5 2.4
Camels 17.0 58 1.0
Pigs in developed countries 328.8 1.5 0.5
Pigs in developing countries 444.8 1.0 0.4
Horses 64.2 18 1.2
Mules, Asses 53.9 10 0.5
Humans 4669.7 0.05 0.3
Wild ruminants and large 100-500 1-50 2-6
herbivores

TOTAL 75.7-79.7

** Total estimate for emissions from domestic animals (cattle, ‘buffalo, sheep,
goats, camels, pigs, horses, mules and asses) has an uncertainty of +15 percent.

Source: Crutzen, P.J., I. Aselmann, and W. Seiler, "Methane Production by Domestic
Animals, Wild Ruminants, Other Herbivorous Fauna, and Humans," Tellus, 38B, 1986, pp.
271-284.


4.1

4.2

4.3

4.4

3

Emissions from animals in developing countries remain
uncertain. Techniques for measuring these emissions must be
developed and undertaken.

Emissions from animal wastes have not been adequately
quantified. Animal waste management practices must be
characterized, and emissions rates for various practices must
be estimated.

Although potential options for reducing emissions may be
promising, they must be demonstrated and evaluated. Research
for identifying long term options must be undertaken.

The scientific infrastructure exists to greatly increase levels of
research to find solutions to limiting CH, emissions from
livestock.


METHANE PRODUCTION Av vstytats 278

Table |. Methane production ov domestic anumats Gra iy

enviar SSC! Te = 10' g)
tl, prouucton CH, production Production

animal (ype Population ‘total population grand total
ind regions [x 10°} ‘ (Telyeari
Cattle
Developed countries, Brazil

and Argentina $72.6 HS
Developing countries 652.3 22.8
Total 1225.4 54.3
Buffatos 141 30 62
Sheep 5
Developed countries 399.7 Ss 3.2
Developing countries and

Australia 737.6 3 3.7
Total 4137.3 69
Goats 476.1 3 Re 2s
Camels 17.0 8 1.0 1.0
Pigs .
Developed countries 328.8 13 0s
Developing countries 1448 1.0 0.3
Total 773.6 09
Horses 64.2 18 12 12
Mules. Asses 53.9 10 os 0.5
Humans 4669.7 0.05 0.2 0.3
Total 73.7

25 MJ per day be taken as an average. Murray et
al. (1978) give smaller values of 15-19 MJ per day
for adult Merino ewes in Australia, which may be
partly due to a smailer body weight of about 40
ke. Similar values are given by Mathers and
Walters (1982) for England. Adopung a mean
daily energy intake of 20 MJ in the developed
countries and 13 MJ in Australia and in the
developing world and applying a mean CH, yield
of 6°; (Kempton and Leng, 1979; Murray et al..
197), we calculate production rates of 8 and 5 kg
CH, per animal per year for the developed and
less developed world, respectively. The world
sheep population in 1983 was estimated by the

Teligs 38B (1986), 3+

FAO (1984) to be 1.1 x 10°, about equally
divided between the developed countries and the
developing world. including Australia. Sheep
therefore produce about 6.9 Tg of CH, annually,
worldwide.

The individual. average gross energy intake of
goats in India was measured by Pandey (1981) to
be 14 MJ per day. This leads to a methane
production of about 5 kg per goat per year,
similar to that for sheep. The world goat
population of about 476 million produces a total
of 2.4 Tg methane per year.

Data on feed intake by camels were not avail-
able but may be estimated from their average


37

EXHIBIT 3-2

POSSIBLE FRAMEWORK FOR A

LIVESTOCK-METHANE ASSESSMENT MODEL

Policy Specifications
Subsidies
Pricing
Trade

Technology Assumptions

Output Prices

Farm Type 1
Farm Type 2
etc.

!

Aggregate Results
National
Regional

Farm Level Decision Model | |“*—

ee

Global ——

Major Outputs:
Animal Population
Animal Preducts
Methane Emissions
Costs of Policies ©



232
Il. Acknowledgements

Dr. G. Allen (US Department of Agnicuiture.
Economic Research Service. Washington DC),
Dr. H. F. Tyrreil (US Department of Agriculture.
Science and Education Administration. Beltsville
Agricultural Research Center. Beltsville), Dr.
D. E. Johnson (Michigan State University.
Department of Animal Husbandry, East Lansing.

P. J. CRUTZEN. I. ASELMANN AND W SEILER

Michigan). Dipi. rer. nat. U. Grewe. Institut fur
Angewanate Bodenbiologie, Hamourg. ana
especially Dr. H. Steingass (Universitat of
Hohenherm. Insutut fir Tierernahrung, Stutt-
sart. F.R.G.) supplied much information through
Private communications. This work was partly
supported by the Ministry for Research and
Technology of the Federal Republic of Germany
through grant BMFT KBF 68.

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Sinctarr sad M. Norton-Grifiith. Cawersty cf
Chicago Press. Chicago—Loncon. zp. 253-236.

Tellus 358 (1986). 2-3


40

EXHIBIT 3-3

PARTIAL AND PRELIMINARY IDENTIFICATION AND
EVALUATION OF CH, EMISSIONS REDUCTION OPTIONS

EMISSIONS REDUCTION
OPTION

(continued)

COMMENTS

Near Term Options (continued)

2.

Increase animal
productivity with
hormones.

Increase animal
productivity with
intact males.

Modify the meat
grading system in the
U

Modify feeding
strategies in
developing countries
by using supplements
to correct nutrient
deficiencies.

Hormone implants are currently available for non-
lactating beef animals (these implants were
recently banned in the EEC). Emissions reduction
is achieved through faster weight gain and
increased feed efficiency. Bovine growth hormone
(currently under development) may increase milk
production in lactating animals significantly,
thereby reducing the size of the animal population.
Food safety must, of course, always be considered.

The use of intact males (foregoing castration) has
been identified as giving similar performance to
the use of hormone implants. The use of intact
males would reduce CH, emissions by promoting
faster weight gain and increased feed efficiency.
Issues associated with using intact males include
managing more aggressive animals, changes in meat
quality, and changes in taste.

The current meat grading system in the U.S.
attaches a premium to finishing practices that
produce a given amount of fat. It has been
suggested that finishing practices that produce
less fat may also produce less methane per amount
of meat produced by reducing slaughter weights and
finishing time. Consequently, modifying the
current grading system so that leaner meats were
not given relatively lower grades could produce
reductions in methane emissions. This alternative
should be examined within the context of the
overall issues associated with meat grading.

This alternative is applicable to animals in
developing nations with nutrient deficiencies (such
as inadequate nitrogen). Emissions reductions
associated with increased fermentation efficiency
are anticipated at the individual animal level.

For a population of animals, significant emissions