Scientists agree the major driver behind the
rise in global greenhouse gas emissions is
human activity. How does farming fit it and,what
is the contribution of animal agriculture
and how are these values calculated?
The consuming public is more and more interested
in where their food comes from, what’s the
carbon footprint.
What’s the carbon footprint, or the what’s
the environmental footprint, of a gallon of
milk, or a pound of beef, or a pound of chicken
meat?
We want to look at the greenhouse gasses coming
off the farm and how we can change strategies.
My name is david schmidt and I’m an agricultural
engineer at the University of Minnesota and
regional coordinator for for the national
project, Animal Agriculture in a Changing
Climate. There is a significant amount of
miscommunication about the role of agriculture
in climate change. Some say that animal agriculture
is the largest contributor to greenhouse gas
emissions while others deny any contribution
from animals. The answer lies somewhere in
between. The objective of this video is to
provide you with a solid foundation of how
emission estimates are calculated and the
real contributions of animal agriculture to
US and global GHG emissions.
Carbon is all around us. It is the fourth
most abundant chemical element in the universe,
behind hydrogen, helium and oxygen.
The biggest reservoir of carbon is stored
in rocks- approximately 66,000 gigatons with
one gigaton is equal to 1 trillion kilograms.
The second biggest reservoir is the deep ocean,
and the third largest reservoir is in fossil
fuels. The atmosphere and the surface ocean
are the smallest carbon reservoirs but possibly
the most important. Carbon is moving between
these reservoirs constantly because of a variety
of chemical and biological processes. This
is known as the carbon cycle.
The total amount of carbon that cycles in
and out of the atmosphere naturally each year
is about 210 gigatons. The arrows and yellow
numbers indicate this movement, or cycling
of carbon. Plants and oceans are referred
to as net carbon “sinks” because they
absorb more carbon from the atmosphere than
they emit. These carbon emissions occur in
the form of plant respiration and chemical
exchanges with the ocean.
The red numbers indicate the human influence
in the cycle, also known as “anthropogenic
emissions.” They can be mostly be attributed
to the burning of fossil fuels and changes
in land use. Human activities contribute nine
gigatons of carbon emissions annually. About
two gigatons of that carbon gets taken up
or absorbed by the ocean. Three gigatons of
that carbon gets absorbed by plants through
photosynthesis and taken up in plant soil
system. All this movement results in an annual
net increase of about four gigatons of carbon
going into the atmosphere each year.
As you can see in this diagram, the amount
of carbon dioxide in the atmosphere was relatively
stable for hundreds of thousands of years,
at an average of around 230 parts per million.
Then about 100 years ago, the CO2 concentration
in the atmosphere began climbing to where
it is right now, about 400 parts per million.
This animated diagram more dramatically illustrates
the rise in carbon dioxide levels in the earth’s
atmosphere in more recent years, since 1979.
The numbers on the left and right indicate
the CO2 concentration in parts per million.
Again this indicates the current CO2 level
reaching up to and even beyond 400 parts per
million.
While we do not intend to focus on all of
the greenhouse gases in this lesson, it is
important to note that carbon dioxide is not
the only greenhouse gas. The most common greenhouse
gas is water vapor, followed by carbon dioxide
, methane , nitrous oxide and fluorinated
gasses. Excluding water vapor, the combined
sources of carbon dioxide, primarily from
fossil fuel use and land use change, make
up about 77% of the global greenhouse gasses.
Because these other gasses trap different
amounts of energy per molecule of gas, scientists
have normalized the data into something called
Carbon Dioxide Equivalents, or CO2 equivalents.
This “equivalent” refers to the equivalent
heating potential of the gas. This is also
known as radiative forcing or global warming
potential. For instance, a single molecule
of methane will trap approximately 25 times
the amount of energy as will a single molecule
of carbon dioxide. So methane has a CO2 equivalent
of 25. Nitrous Oxide has a CO2 equivalent
of 298. This use of CO2 equivalents allows
us to evaluate the impact of the gasses on
the environment - not just the amount of these
gasses in the atmosphere.
Anthropogenic greenhouse gases are emitted
by many sources and from every country. Together
these nations contribute a world total of
45 thousand million metric tons of CO2 Equivalents.
This graph shows percentages of greenhouse
gas emissions by country in 2012. The United
States is currently the second highest emitter
of these gases, contributing about 15% of
the world total. The highest emitting country
is China. However, this same information can
be evaluated based on emissions per capita.
This breakdown shows the US at about 19 tons
CO2e per year per person vs China at 7.5 tons
CO2e per year per person.
Taking a closer look at the sources of greenhouse
gas emissions in the United States alone by
economic sector,, we see that agriculture
contributes 9 percent of total emissions in
the US. Total emissions in the US add up to
approximately 6,673 million metric tons of
CO2 Equivalents. Agriculture’s 9% represents
about 515 Million Metric Tons of that amount.
Looking at the agricultural sector itself,
we can see that agricultural soil management
is the biggest source, it accounts for about
50% of total agricultural emissions. This
is followed by enteric fermentation at about
32% and manure management at 15%.
Now looking at the type of gases emitted,
about 55% of the agricultural emissions are
from nitrous oxide, which is produced naturally
through the the microbial process of nitrification
and denitrification of mineral nitrogen in
the soil. The remaining 45% is from enteric
methane or from methane formed during the
microbial breakdown of manure. Note that these
emissions are only the direct emissions of
greenhouse gasses occurring on the farm. Other
emissions that would occur off farm - like
emissions from fertilizer production or electricity
used on the farm are not included in these
numbers.
We can also look more closely at emissions
from animal species. In this chart you can
see the comparisons between beef cattle, dairy
cattle, swine, poultry and all other livestock.
These differences are primarily a function
of total animal numbers and the contribution
of enteric fermentation. Again these are direct
emissions for animal production and do not
include emissions from the production of things
like animal feed.
Overall if you look at all animals in the
united states for example – the beef sector
would have the greatest impact on carbon footprint
of this nation but that’s only because there
are so much more beef animals than dairy animals.
We have 90 million beef animals and 9 million
dairy animals, so 10 times more beef animals.
However, a better way to think about greenhouse
gas emissions is in terms of emissions per
unit of production. We can look at kilograms
of CO2 equivalents per kilogram of product
produced or product consumed. This evaluation
includes not only direct emissions from the
farm, but also the emissions that occur after
the products leave the farm. We will discuss
this further a little later in the video.This
graph compares the greenhouse gas emissions
of several products on per kilogram basis.
Of all the products, lamb is the highest emitter
per kilogram of product consumed, and beef
is the second highest emitter at 27 kilograms
of CO2 equivalents per kilogram of beef consumed.
Dairy is much lower in emissions, with 1.9
kilograms of CO2 equivalents per kilogram
of milk consumed.
Before getting further into attributing emissions
to different sectors of animal agriculture
or to different sources on the farm, we’ll
look at the system used to measure and calculate
these emissions.
There is a way to quantify greenhouse gasses.
This quantification method is called LCA,
life cycle assessment. It has been done for
many years and it has been done by many different
groups using different methodologies.
The Life Cycle Assessment, or LCA, is an accounting
method that tracks all of the greenhouse gas
emissions produced by a given process, product
or system. Often this is called a ‘cradle
to grave’ analysis, because it encompasses
all of the emissions in the life cycle of
the process, product or system being analyzed.
This includes anything from the extraction
of raw materials to the final disposal of
the end product.
Animal scientists, engineers and others can
further describe the scope and mission of
the LCA as it relates to animal agriculture.
Basically, the life cycle assessment looks
at the entire life cycle associated with a
product. Let’s say if McDonalds or Walmart
or some other chain were to ask me what’s
the carbon footprint or what’s the environmental
footprint of a gallon of milk or a pound of
beef or a pound of chicken meat produced by
your company.
Most producers would have no idea – but
a life cycle assessment allows you to do just
that.
It allows you to look at the entire life cycle
impact of that product. For example, the carbon
footprint of a gallon of milk includes not
just enteric gasses that come out the front
end of the cow or methane or other gasses
that come off the manure, it includes everything
– the herbicides and other chemicals applied
to crops, the crops themselves, the soils
where the crops are grown, the animals, whether
it is enteric gasses or manure gases, It includes
the cooling of the product, the transport
of product and so on. Everything from cradle
to grave of this product. The true life cycle
of this product.
Life Cycle Assessment is a systematic approach
for primarily accounting for environmental
impacts. It is a systems scale analysis of
any product or service really. In the dairy
industry. What it means is to divide the system
into supply chain stages, typically. In each
of those stages we would have what we call
unit processes that have material and energy
flows, inputs and outputs from other unit
processes as well as, inputs or outputs from
nature. So emission to the soil, water, or
air. And the process of LCA looks from cradle
to grave.
Dr. Thoma’s analysis in 2013 of greenhouse
gas emissions from the production of milk
in the United States looked at the entire
life cycle of the milk supply chain, starting
with the production of fertilizer to grow
feed for cows through the consumption of milk
and disposal of milk packaging.
So if we are talking about just the dairy
farm so that would be what we might consider
a gate to gate analysis and we would be interested
in what happens just on the farm – that
would not be considered a full life cycle
assessment. So, when we did the carbon footprint
for milk, we literally had to account for
the coal, the transportation of the coal,
the construction of the power plant, the losses
in the transmission lines to run the refrigeration
units at the retail. So all of that is accounted
for.
This table from Thoma’s LCA shows the breakdown
of greenhouse gas emissions across the milk
production supply chain. The colors represent
the four different types of gas emitted by
each stage in the cycle, from feeding the
cows, enteric fermentation, manure management
... all the way through the consumption of
milk and disposal of packaging. The pie chart
further illustrates the percentage of each
activity’s contribution to milk’s carbon
footprint.
Thoma’s analysis found that the CO2 equivalents
produced by each kilogram of milk consumed
ranged from 1.77 to 2.4. This is about 17.6
pounds of CO2 equivalents per gallon of milk
consumed.
72 percent of those emissions occurred before
the milk left the farm gate.
So from the extraction of coal, say, for the
electricity that may be used anywhere in the
supply chain all the way to the emissions
associated with wastewater treatment for wasted
milk that goes down the drain or the plastic
container that ends up in the landfill and
may generate methane. So all of those emissions
across the entire supply chain are, we attempt
to account for – tally them up then say
this is the impact.
Thoma applied the same system to an analysis
of of greenhouse gas emissions from pork production.
This study took into account all of the activities
in the pork supply chain that contribute to
emissions, from electricity and fuel to manure
and waste, across all stages of production,
from the sow barn to the consumption of the
pork products produced.
The LCA showed CO2 equivalents at an average
of 8.8 to 11.6 kilograms of CO2 equivalents
per kilogram of pork, from production to consumption.
This can also be calculated as 2.2 to 2.9
pounds of CO2 equivalents per 4 ounce serving
of pork. Approximately 60% of the emissions
occurred before the product left the farm
gate.
While the LCA is widely accepted as the most
useful and accurate tool for estimating a
farm operation’s environmental impact, there
is some interest in learning about farm specific
variables that might affect the results. Do
differences in farm size, manure handling,
farm practices and technologies, soil conditions,
regional climate systems and other farm factors
impact the emissions?
When we looked at this in various ways. . . . what
wasn’t clear was – oh small farms were
not as good as big farms. We saw small farms
that were down in the 0.8 0.9 range. We saw
large farms that were in the 1.7 1.8. Our
conclusion from that was – it is not what
you are managing but how you are managing
it so the implementation of best or beneficial
management practices and care of the animals,
care in the ration formulation, all of these
things contribute to the better performing
farms.
Dr. Thoma’s LCA for pork production found
some effect from manure management. Farms
using anaerobic lagoons had slightly higher
emissions than those using deep pit systems.
As noted in the Thoma report, a full LCA encompasses
many variables, and with each variable there
are some assumptions to be made. How was the
electricity used on the farm produced?
Was it coal based or nuclear?
Was the corn grown for feed irrigated?
If so, what energy source powered the pumps?
What was the animal diet?
How many piglets per sow?
How far away is the slaughter plant? the consumer
market?
Was the meat cooked on a gas stove or electric
stove?
How much of the final product was wasted - either
in cooking or off the plate?
All of these variables must be assessed and
generalized for this kind of study.
Scan level LCA’s are used to help pinpoint
the main emission areas of a product or process.
For swine production, about 23% of the emissions
are at the consumer level and 62% on the farm
level. These farm level emissions are split
primarily between manure management and feed
production. This information helps the industry
and individual producers target any emission
reduction strategies.
Helping farms perform better is the ultimate
goal of the LCA. International standards have
been developed for conducting an LCA, which
is important so that farmers, regulators and
others can get a clear picture of farm product
emissions and identify what could be done
to reduce these emissions.
Once you know what the LCA impact is of your
product then you really know where you are
– if you feel your too high then you can
compare to what it would be if you were to
make changes – so that you can reduce.
But if you don’t know where you are, you
have no idea whether changes would work. That
is why it is so critical to have good assessment
methods, because they help you to know where
you are. The analogy is - you driving on the
interstate – with a car that doesn’t have
an odometer. You have no clue how fast you
are going but you see speed limits everywhere.
So you have no clue – am I going to fast?
You know, what am I doing here?
That’s where the industry is right now.
There are regulations, some of them very strict
– for example in California, yet the producers
don’t know – am I complying am I not complying?
Where shall I go?
Where is the goal pole?
They don’t know, that’s a situation that
is untenable. And the public is exerting extensive
pressure, the legislature is, regulatory agencies
are.
There is nothing simple or straight forward
about tracking greenhouse gas emissions and
global carbon cycling.
It is also clear that no process or product
is entirely responsible for these emissions.
It is a combination of both natural and human
activity that can be evaluated on a global
scale or on an individual product scale.
We are all aware of the value of agriculture
as we look forward to the challenges of feeding
an every growing human population. However,
we must also understand for our role in the
production of greenhouse gas emissions.
Thanks for learning about this important topic.
