cc >> I'd like to thank you all
for coming. My name is Tim Donahue.
And again I'd like to thank you for coming to a special seminar
that's sponsored by the Great Lakes Bioenergy Research Center.
For those of you who don't know what the Great Lakes Bioenergy
Research Center is, it's a new DoE funded research center,
housed at the UW-Madison, but functioning as a virtual
center across the country to help develop and rollout
technologies for the conversion of cellulosic biomass
into fuels. One critical part of that
center's activity is the topic of today's lecture,
in particular, in addition to work going on in the center
on the improvement of plants, and microbes
and chemical activities to make it easier to convert
plant biomass into fuels, there are significant activities
in the center worrying about the days when we take those
observations from the lab bench out into the field.
And that's under the broad brush of our sustainability
activities. So there's been a lot
of legitimate discussion in the free press lately about how
biofuel activities can and will be sustainable in the future.
And so it is very timely that several months ago,
Phil Robinson, who's the leader of the sustainability program
in the GLBRC agreed to come over and visit with people at Madison
and give a talk on those aspects of the program.
As I said, Phil is the leader of those activities.
And he's the perfect person in our mind to do that.
He's a professor of Ecosystem Science in the Department of
Crop and Soil Science at Michigan State University.
And he's been there since 1981. Since 1998, he's directed the
Long-term Ecological Research Program in Agricultural Ecology
at the Kellogg Biological Station, the experiment station
in the state of Michigan. So he brings to the center
and to the table in this activity, a large and productive
and internationally-known research program, in thinking
about and dealing with issues related to sustainability.
So with that, I will shut up and introduce Phil.
I thank him for coming today. ( applause )
Well thanks, Tim, and thanks everyone for showing up
this morning. It's a pleasure to be here.
And it always amazes me that I'll be talking about a topic
that wasn't on most of our radar screens only two years
ago. And it's a fun topic to talk
about in many respects, partly because it's controversial.
But more importantly, because it integrates a lot of what we know
about agricultural ecosystems in a way that helps to inform
the sustainability of these systems, and perhaps the birth
of a new agricultural industry across the U.S.
and across the world. Well, let me start
by explaining a little bit about why I phrased my talk this
morning this particular way. That is,
the "Biogeochemical Challenge." There are, of course,
a lot of different aspects to the sustainability of
biofuel cropping systems and cropping systems in general.
We have to think about economic sustainability,
profitability of these systems. If they're not profitable,
of course, they're not going to be sustained.
We have to think about the environmental sustainability
of which biogeochemistry is a part.
We have to think about the social sustainability
of these systems, the potential for these systems to contribute
to rural development and the sustenance of rural communities.
And, of course, we have to think about food security.
A part of this has been in the press a lot in the
past few weeks and causing some people to doubt the overall
sustainability of biofuels in general, for good reason.
And I'll talk about that a little bit.
We're considering all aspects of sustainability in the GLBRC,
but I want to focus on biogeochemistry in the main part
of my talk today. First, because
if we can't get this part right, then biofuels lose
a lot of their attraction. We're in this business,
apart from the issues of energy security, we're in this business
for an environmental standpoint, largely because of their
potential for helping to stabilize climate.
So climate stabilization with respect to CO2 content
of the atmosphere is a biogeochemical issue.
And second, while the biochemistry is not complex,
there are aspects of it that are quite simple, in fact,
there are a lot of pieces that have to be understood if we're
really to design sustainable systems, and to get the most out
of these systems in the future. So I think it's important
for all of us to understand at least most of those pieces.
So as you'll see, we're not talking simply about carbon
balance, we're talking about other greenhouse gases and
perhaps some other co-benefits, some biochemical co-benefits
of these systems as well, on nitrogen cycling, for example,
and the potential for cellulosic systems to ameliorate
some of the nitrate issues and some of the nitrous oxide issues
that we now face with agriculture as it's done today.
And I'll talk in detail about the biogeochemical needs then
in relation to our ongoing research effort.
And then I'll describe, I'll take a few minutes at the end,
actually more than just a few minutes, to describe the
overall sustainability research that we anticipate will be
a major part of the GLBRC in the years to come.
It's a major part now, but the GLBRC as many of you know,
is just getting started. So much of this research is
still in its very nascent part. From the outset, the promise of
biofuels is a win-win situation for a lot of reasons.
It's a win-win situation from the standpoint of farmers
in many respects. It's a win-win situation from
the standpoint of the environment in many respects.
It's a win win situation from the standpoint of some key
social issues, as well, for society, I would argue.
But that really is the case only if it's done right.
There are a lot of opportunities for doing it wrong.
We need to be aware of those pit falls from the outset.
And that's one of the reasons that we're extremely pleased
to be part of the GLBRC from the outset to try to anticipate
some of these problems as cellulosic biofuels become
a major part of the biofuel economy in the years to come.
So it might be helpful to start at the top
and close to first principles, simply because given
the controversial nature of what we're about, and I have
colleagues on both sides of the various disputes
that have arisen, in some cases yelling at each other in print.
It could be useful to think for a moment about what we're
trying to achieve with this. And at one level,
what we're trying to do is to reduce the flow of petroleum
into the economy to a trickle. You're not going to be able
to read the pieces on this, I'm not so much interested
in that, as you're seeing the size of the arrows.
This is a description, a DoE description of energy flow for
the most recent year available, or petroleum flow for the most
recent year available, 2006. And we have on the order
of 15 million barrels a day coming into the U.S. economy.
Around 10 million barrels that are coming in as imports,
and the remainder as produced here.
And I'm not going to take you through all of these pieces,
the important part is this bit down here,
these 14 million barrels of transportation fuel, which
translates to about nine million barrels of gasoline.
And it's that that we're trying to reduce to a trickle
from a societal standpoint. We want to reduce this fat arrow
here, which is the biggest petroleum user in the economy
to something akin to what electric power
is currently using. So the EPA released a couple
of months ago an analysis, a wedge analysis
of the transportation sector petroleum use.
And a wedge analysis is simply a way of taking Steve and Bob's
wedges for stabilizing climate at some background level,
2006, in this case. What technologies would need
to be brought to bear to keep CO2 concentrations
in the atmosphere at levels that are 2006 levels.
And this is specifically for the transportation part
of the CO2 burden in the atmosphere.
And the EPA divided this stabilization triangle into
nine different wedges. It's just a way of approaching
the issue of asking what different technologies
can contribute, how much to solving
the stabilization problem. And the wedges that they
identified, that would be potentially available,
and needed to stabilize 2050 CO2 levels in the atmosphere
at 2006 levels are these listed here.
And the values here are the size of the wedges that are needed.
And so, gasoline hybrids are expected to contribute
somewhere on the order of .8 to 1.0 wedges
to the solution, which requires nine wedges.
Plug-in hybrids, 1 to 2. You can read down here all
the various technologies that are thought to be necessary
to bring us to this point. The biofuels plays a role
in this. And a role in all other
different scenarios that EPA presented.
And the thinking is that biofuels can provide somewhere
on the order of 1.3 to 2.7, depending on the scenarios
that are presented. Wedges to contribute to a total
of six to 13 wedges, which would be enough to stabilize
the transport sector's contribution to CO2
stabilization at 2006 levels. And this 1.3 to 2.7 translates
to about 40-80 billion gallons of ethanol per year.
So that's one analysis of the target we're heading for, is
that amount of quantity of fuel. Now this taken by itself,
I wouldn't necessarily believe the EPA's analysis
without some additional support. And the NRDC, it turns out,
did a similar sort of analysis, a year or so ago, and came to
basically the same conclusion. That is, by 2050, if we can
divide the total transportation, expected transportation needs
in terms of today's million barrels of oil.
So something on the order of 17 million barrels of oil
per day, projected to be needed by 2050, some portion of that,
a large portion of that, we ought to be able to achieve
with efficiency and smart growth policies and behaviors.
But some portion of it is going to still be,
we're still going to be reliant on liquid transportation fuel.
That liquid transportation fuel could be biofuel.
Some part is still going to be gasoline.
There's no issue there. But they came to a similar
number, somewhere on the order of 80 billion gallons
of ethanol that's needed. So there's a considerable
legislative momentum starting to set the trajectory
for this as well, as I'm sure most of us are aware.
In December, the U.S. passed the U.S. Energy Policy Act
of 2007, which aims to produce 22% of transportation fuel mix
in 2022, which means 36 billion gallons of ethanol
that's projected to be available in only 14 years,
which is not very far from now. And 21 billion gallons of that
is expected to be, by target, cellulosic ethanol.
And 15 billion gallons of grain-based ethanol.
The EU is close behind. The EU recently set a target
of 20% renewable energy by 2020. And 10% of that, or half
of that target, is targeted to be transport fuel.
So there's also a big push in Europe for the quick development
of these fuels. We're pretty close to
the capacity that was already identified by the Energy
Security Act, which currently, we have a capacity in the U.S.
of about 13.5 billion gallons. So we call that, we're talking
about 80 billion gallons or 60 billion gallons
as a total need. And if 15 billion gallons
targeted for 2022, we're just about there
for grain alcohol. So we're effectively, I won't
say maxed out, but we're very rapidly getting there,
more rapidly than many of us would like.
But in any case, just to put in perspective where we are
versus where we're aiming to get as a society, as the legislative
society, we're well on our way to developing this economy.
So the next question is how much biomass is needed
to satisfy this quantity of ethanol.
If we take as a target a midpoint of the EPA range,
some 60 billion gallons, we're looking at a need for
grain biomass using today's technology that translates
to about 2.6 gallons of ethanol per bushel of corn.
We're look at about somewhere around the order
of 23 billion bushels of corn needed to satisfy that demand.
And you can compare that to 13 billion bushels of corn
that were produced in 2007. If you look at future
technology, this is a fairly mature technology.
In the near future, it's likely to produce only an increase
of around 10%, up to 3 gallons per bushel,
mainly due to higher starch varieties coming into the
processing stream and grain cellulose conversion.
We're likely to see a need for somewhere on the order
of 20 times ten to the ninth bushels, which is still well
over the capacity of the U.S. corn market to satisfy.
So, clearly there are limits to what we can do with grain
ethanol. And we have to turn to
cellulose ethanol. And we then have to ask, well,
how much biomass do you need for cellulosic ethanol.
And again, we can look at today's technology where
pilot plants are producing on the order of .3 liters of
ethanol per kilogram of biomass. And it's an easy calculation
to make. Figure out, well, how many
kilograms of biomass does one need to produce
that much ethanol. And it comes out to somewhere
around 776 million metric tons of biomass.
Well that's a big number. What do you do with that number?
How do you compare that number to what is available?
Well, one way to think about that is to think about all of
the corn stover that is produced in the U.S., which is an easy
number to calculate, because there's about the same mass of
stover produced in above ground residue in a corn field
as is produced in grain. And so, we know that based on
the overall yields of corn, actually this is an analysis
that covered the period, 1995-2000, that around
196 million metric tons of corn stover were produced
and Graham, and others, who produced this analysis
also suggested that about half of that, about 110 metric tons,
could be removed in a sustainable manner.
That is, if these corn fields were grown under a no-till
situation, so that some proportion of the litter was
left in place, not harvested, in order to protect against
erosion, and in order to provide enough biomass
for carbon sequestration, then we're probably thinking about
more on the order of 110 times ten to the sixth
metric tons that could be sustainably removed.
We could also think about the amount of biomass that's
available from industrial waste, both from the pulp industry,
as well as from the wood products industry.
Material that is readily harvested, simply because it's
in an industrial setting in point source
in effect already. And so it would be fairly easy
to pull together and put into the stream.
So we can think about needing 776 million metric tons of
biomass for today's technology. And it's likely that we will get
some improvement in that technology-based on GLBRC
research in large part, so that we might be looking at something
on the order of .43-liters of biomass yield in the future,
which would bring us to the need for 530 metric tons of biomass.
So the stover and the wood waste are low hanging fruit.
Those are readily available now in today's technology
without harming the productivity of the current cropping systems.
I'm not suggesting that if we moved to a continuous
corn system that would be a way to satisfy part of that need,
but just with existing technology, existing economies,
this is a kind of biomass that we could divert now
to a cellulosic biomass stream. So taking these numbers then,
you can ask, well how much land is necessary to satisfy this.
And if we subtract off the low hanging fruit, then we can
come up with 560 million metric tons needed for today's
technology, 314 for tomorrow's technology.
And we can think about how many millions of hectors are needed
to bring into production to do that.
But if we take switch grass at today's yields, and these are
realistic field-based yields, not experiment station yields,
somewhere around 7.5 metric tons per hector, then we can easily
calculate that we need somewhere around 75 million hectors
of land, on which to grow switch grass in order to satisfy
100% of this ethanol need. Some time in the future, we
might be able to increase that yield, we might be able
to get away with only 42 million hectors.
If we were to use human grasslands, native prairie
perhaps, then we would need, which has lower productivity
than a switch grass system, we would need somewhere on the
order of 112 with today's technology, and somewhere
on the order of half of that with future technology.
So the basic answer here is we need somewhere between 40
and 100 million hectors of land on which to put this technology.
Well how much is that? It's a lot, because if you
consider that we only have 180 million hectors of land
currently cropped in the U.S., we're not going to divert
a large portion of that to cellulosic biofuel production
without having severe impact on food security.
We also have, however, a large number of grasslands.
Some of those are arid range lands, but a fair proportion
of it is grasslands that are classified as grasslands,
because they're not currently used as production.
They're marginal land, perhaps former farmland that has been
abandoned and is now in landscapes as successional
systems. We also on the order of
15 million hectors of CRP land, which could be harvested if
the rules were changed and added to the stream.
And so we have this need for somewhere on the order of
40-100 million hectors of land. It could be satisfied if
we think about land that, especially land that is not
currently used for food. And that's one of the promises,
I think, of a cellulosic bioenergy economy, as opposed to
the current grain-based economy, which by definition, as we
all know from recent spikes in grain prices certainly,
has a big impact on food production.
So there's another aspect of this, too, and that is that
we also have a fair proportion of abandoned agricultural land,
especially in the Great Lakes region, which I'm sure that
any of you, and certainly in Michigan, driving across
the Michigan landscape, there's an awful lot of marginal land
that was taken out of agriculture in the past,
and has been reverted to successional systems on the
order of anywhere from recently abandoned to 50-100 years old
at this point. And that land could also be
reconverted. As far as I know, I'm not aware,
at least of any comprehensive analysis of the availability
of those lands. But at least an analysis
that was done over the period of 1982-1997 showed that there was
somewhere on the order of 12 million hectors of land
that had reverted from cropland to forest.
And forest is defined as 10% cover, so in Michigan,
it takes about 20 years for a 10% cover of trees
to come into an abandoned agricultural field, so this
is, I think, a big underestimate of what's actually available
and could be converted to cellulosic crops,
perhaps to native systems, perhaps to planted switch grass,
perhaps to a variety of cellulosic feed stocks
that we'll have to think about as we think about these issues.
So the problem, of course, with grain ethanol is that
as we think about the impacts of ethanol, in a sense,
it's simply business as usual but larger, with all of the
attendant environmental problems that are associated with
today's agriculture, ranging from growth hypoxia
to various pesticides that enter waterways, to impacts
on the trace gas content of the atmosphere,
and biodiversity issues. So there are also some huge
sustainability issues that most of us recognize
with respect to grain ethanol, that may not be the case,
should not be the case with cellulosic systems.
So cellulosic systems we have the opportunity to add
perennially to U.S. cropping systems in a much bigger way
than we currently have. So the perenniality simply
meaning planting crops that are not tilled every year,
not planted every year, not nurtured every year in the
same way that annual crops are, and so we have the potential
to install these grasslands or woody crops in places
that are now farmed marginally, and that can provide
a lot of benefits that we're not now seeing.
Those benefits including those that come from landscape
diversity, such as effects on insects, beneficial insects
in particular, effects on water quality,
effects on wildlife and effects on climate stabilization.
And that's what I'm going to talk about in much of this
next portion of the talk-- what is the role of agriculture
in adding to the mitigation portfolio for global strategies?
So I want to take a big picture here first, and then I'll
zero in on some research that we've been undertaking for the
past 20 years, or so, at the biological station.
But to set the stage, I need to talk first about--
This is a graph that everyone is familiar with.
It shows the long-term rise of atmospheric CO2 and
our game plan, ultimately, is to keep CO2 levels stabilized
at somewhere in this range here, with this projected 2100 range
at the midpoint, IPCC scenario, one of the conservative
scenarios, showing that where the trajectory is to be
way outside of those bounds. So in order to keep current
levels stabilized, whatever current level we're at the time
that stabilization is effective, it requires thinking about
the global CO2 balance. So if we think about the
contemporary global CO2 budget, we can categorize different
sinks and sources as are done here.
So we have sources as being emissions from fossil fuel,
emissions from deforestation, as the two principle sources
of CO2 to the atmosphere. So we have somewhere on the
order of 9.1 pentagrams of CO2 being added to the atmosphere,
CO2 carbon, being added to the atmosphere annually.
That carbon is being removed from the atmosphere at a rate
of 2.2 pentagrams, by ocean, mainly by chemical processes
in the ocean, and 2.8 pentagrams being taken up
by terrestrial vegetation and soils, and staying
in the terrestrial vegetation and soils, which leaves
a difference of 4.1 pentagrams, that is the atmospheric
loading rate for CO2 in the atmosphere.
And when we think about stabilizing CO2, what we need
to think about is how do we bring this term to zero,
so that we're not longer adding CO2 to the atmosphere
that stays there. We'll be adding CO2
to the atmosphere, of course, but we'll expect that CO2 to
be removed from the atmosphere on an annual basis, so that
stabilization ultimately results in this term, the atmospheric
increase going to zero. As you can see, we're going the
wrong direction at this point. Just in the past decade,
we've increased this term by over 25%.
No surprise. So what is agriculture's role
in all of this? Well, agriculture has several
roles to play. If you classify the strategies
for stabilizing atmospheric CO2 into three broad strategies,
we can think about reducing fossil fuel consumption
by improving efficiency, by developing renewable energy
sources, such as biofuels, we can think about identifying
CO2 sinks and sequestration rates.
And, of course, many geologists think it's possible to store CO2
in geologic reservoirs, perhaps in aquatic reservoirs.
But the more practical sequestration that's certainly
is possible now, or that agriculture can help with
is that sequestration of carbon that was lost at some point
in the past, into soils and into long-lived plants.
And then the third major strategy is reducing the non-CO2
greenhouse gases. There are other greenhouse gases
other than CO2 that are in the atmosphere that are biogenetic,
that are naturally occurring, and that agriculture,
as I'll show in a few minutes plays a huge role in regulating.
So let's think about carbon loss and the basis
for sequestration in ag systems. And the potential for carbon
sequestration in agriculture basically stems from the loss
of carbon when agricultural lands were initially converted.
The exact same processes that are going now when we
clear tropical rain forests. We lose carbon from soils, and
we lose carbon from the trees and above-ground vegetation.
And that occurs universally, across the globe, at a rate
of about 40-60% is lost over 40-60 years.
This is known from the 1950s. It seems to be one of these
rules of thumb that doesn't diverge
much no matter where you are. It's possible to calculate.
There is some 54 pentagrams from an original 220, or so,
pentagrams that was lost in this way.
So that means that there's a potential for recovering
that carbon and taking it out of the atmosphere and storing it
in soil, if we can develop the technology to do that.
And the no-till technology is, of course, one of those main
strategies. And the calculations,
the conservative calculations, is that we can remove somewhere
on the order of .3 to .5 pentagrams of carbon per year.
Somewhere around 10% of the current carbon loading rate in
the atmosphere is possible to, as a mitigating contribution
from the development of soils that store more carbon.
But there's a 54 pentagram cap. That is, we're not going to be
able to recover more than was originally lost, and probably
we're only going to be able to recover some proportion
of that, maybe 50% of that. Eventually this soil saturates.
That saturation occurs somewhere on the order of 50-100 years
after the technology is implemented.
Now CO2 is not the whole story, of course.
We also have these other gases. The other biogenic gases,
those gases that are produced by microorganisms in soil
in native, as well as managed ecosystems, include
nitrous oxide and methane. And those are also adding
to the radiative forcing to the atmosphere.
Those also offer an opportunity to stabilize the radiative gases
in the atmosphere. Those two gases in particular,
methane and nitrous oxide, are also increasing
exponentially now, as is CO2. This is a 2,000 year history,
mainly from ice forests for carbon dioxide, which is in red
here, and you can see that the methane, which is in blue,
as well as the nitrous oxide, which is in black,
are both tracking the same sort of trend.
Now why are those interesting? Those are trace gas that are
in quantities in the atmosphere that are a fraction of those
quantities that are represented by CO2, but they have
an interesting feature. They have a much greater impact
on a molecule by molecule basis than does CO2.
So the global warming potential, which is an atmospheric
chemist's way of comparing the radiative impact of a molecule
of any gas against some reference gas is much higher
for methane and nitrous oxide than it is for CO2.
So by definition, the global warming potential of CO2 is one.
The usual IPCC way of calculating the impact of these
is over a 100-year time horizon. These have different atmospheric
lifetimes, so you have to consider the amount of time
you're making this impact estimate.
Methane has 23 times the impact of CO2.
Nitrous oxide has 300 times the impact of CO2.
So what that means is that avoiding the emission of
one kilogram of nitrous oxide into the atmosphere
is equivalent to avoiding the emission
of 300 kilograms of CO2. So avoiding a little bit of
nitrous oxide has a big impact on the CO2, or I should say
the CO2 equivalent burden of the atmosphere.
So if you think about where nitrous oxide or methane
come from and how they get into the atmosphere,
we can define that the major anthropic sources of these gases
are agriculture. And in the case of methane,
about 55% of the methane that is currently produced by humans
is from agricultural activities, and about 45% from industry.
Nitrous oxide, about 80% comes from agriculture
and a much smaller percentage from industry.
That becomes interesting when you total up
in carbon equivalents what the total impact of these are.
It's possible to calculate then that there's somewhere
on the order of 3.2 pentagrams of carbon equivalents
being emitted to the atmosphere from human activities, a large
part of this is agricultural, which suggests that agriculture
could play a strong role in mitigating the buildup
of these radiative gases with the proper management.
And it gives us the opportunity then to think about the CO2
budget of cropping systems, not just in terms of energy balance,
as is more common in bioenergy systems, but also in terms
of the total CO2 equivalent accounting, which includes these
other gases, as well as carbon. And so, we can think about
sources of global warming potential and a cropping system
that's not just the carbon balance, not just carbon
sequestration into the soil or carbon decomposing and
releasing its CO2 in a bio-refinery, or once
it's burned in a vehicle, but also the other greenhouse
gases that are involved. It allows us to count that
as a benefit, if you will, on that side of the ledger.
So what are the major sources of global warming impact
and fuel crop ecosystems? There's fuel use, of course,
that's a no brainer. There's also soil carbon change,
which is the basis for carbon sequestration.
There's also nitrogen fertilizer.
Nitrogen fertilizer takes a fair amount of energy to produce.
It takes, in fact, a fair amount of methane to produce.
And the process of producing by the Haber-Bosch process
releases CO2. So there's a CO2 cost
for nitrogen fertilizer that's a burden on the ecosystem's
carbon balance. There's also a lime.
The agricultural lime that we add to cropping systems
is a carbonate, and that carbonate, as it's attacked
by acid over the course of the cropping season,
turns into CO2. So there's another source
of CO2 in the system. And then, of course,
there's also nitrous oxide flux and the methane flux.
So I want to use as an example some research that we've been
conducting at KBS over the past 20 years and bring you up.
Some of you may have seen some of this before, most of you,
I'm sure haven't. But I want to present
some updated data. We had, in place, at KBS
as part of the LTER site there, a series of cropping systems
that are arranged along a management intensity gradient,
ranging from annual grain crops, which we would consider
high intensity, through perennial biomass crops,
which would be the equivalent of the cellulosic biofuel system.
Through unmanaged communities, including an early successional
old field, which is simply a field that we let go in 1988
when the plots were established. And so while it's not native
prairie per se, about 50% of the species are exotics.
The native plants are plants are grown in an unmanaged setting.
And we also have midsuccessional old field, a field that was
abandoned 50 or 60 years ago, and then an old growth forest.
We have some postage stamp-sized wood lots that have never been
cut, so allow us to use these for reference points
for what was probably the pre-European settlement fluxes
for these gases. So we can think about soil
carbon change over the first ten years of this experiment.
As you would expect, there was no gain of carbon in the annual
conventionally tilled system, and some 30 grams per meter
squared per year was gained in the no-till, which is
actually the median rate at which carbon is sequestered
in no-till systems. But the interesting piece here
is that the poplar and alfalfa systems both sequestered carbon
as well. Which makes good sense, simply
because they're also no-till, right?
You plant these things and you don't go back
and till them every year. They're also adding woody roots
to the system that the herbaceous systems are not,
so we might expect them to be at least in some cases,
to add more to the soil carbon sequestration rate.
But more interesting is this early successional system,
which is adding almost twice as much carbon to the soil
than is either of the other perennial biomass systems
and twice as much as a no-till system.
And here is a probably an effect of diversity, that is we have
more diverse plant material coming into the system, and
the microbes are having a tougher time of breaking it
down on annual basis. Now here we have an example
of the saturation of this, in that the sequestration goes
from 60 in the first ten years down to somewhere less than
11, or so, in the midpart of the century.
And then it goes to zero in the old growth forests.
Old growth forests are by definition at equilibrium.
Their carbon balance is not changing much.
As a result, we have no sequestration potential
in a like successional forest. We can expect soil carbon
sequestration to disappear after about 100 years of
whatever kind of perennial crop we're putting in
without tillage. I want to talk about the
nitrous oxide portion of this for a couple of minutes as well.
And nitrous oxide is measured in a very simple minded way.
It's very labor intensive. There are no better ways
to do this at this point, but it simply is a matter of putting
a box on the soil surface and collecting the gases
that are emitted by that soil over the next 30 minutes
to two hours, and then plotting a flux
based on the concentration change in that box over that
one to two hour period. When you do this, and we've
had the luxury of being able to do this for almost 20 years now.
I think we have the longest continuous record of N2O fluxes
from cropping systems now in the world.
But when we do this, we see that there are very strong patterns,
and that the annual cropping systems are producing N2O at
equivalent rate that are about three to four times the rates
in the unmanaged systems. So even the reference system
in the native forest, which is slightly higher than the early
and mid-successional systems have rates that are on the order
of a 1/3 to 1/4 of those that are in the annual
cropping systems. Perennial crops are different,
based on whether nitrogen is available.
Alfalfa, which is a legume, has N2O fluxes that are equivalent
to those from the annual cropping systems, which makes
sense if you think about what are the major controls
on nitrous oxide production. This is a bacterial process
called de-nitrification that results in the microbes
producing N2O from nitrate. There's a lot of nitrate
circulating in these systems. So there's a lot of
available substrate for the denitrifying bacteria.
Poplars on the other hand are extremely efficient
from a nitrogen utilization stand point.
You would expect it, therefore you might predict
that nitrous oxide fluxes would be low.
In fact, they're even lower than they are in the unmanaged
systems, which suggests that there's a real potential
for a cellulosic perennial biomass crop to provide
this service to a landscape in which it's planted.
That is, to avoid the emission of nitrous oxide, as opposed
to a crop that was there prior to it's being grown.
Early successional system is similar to a prairie system,
if you will. It also has very low
nitrous oxide fluxes that aren't much different than the poplars.
Now CH4 oxidation, and this is a process whereby methane
is taken out of the atmosphere and -- by methanatrophs
in soil, about another class of bacteria that in this case
use methane as an energy source. Methane oxidation is interesting
globally because about 30 terograms of methane per year
are removed from the atmosphere by soils.
And that removal occurs mainly in undisturbed ecosystems,
mainly in forests. It turns out that when
you convert these native systems to agricultural use,
you effectively shut off methane oxidation.
And that is important globally, because of the
atmospheric burden of methane in the atmosphere.
We're adding about 44 terograms per year from all sources.
Soils are taking out 30 terograms.
So if soils were not taking out 30 terograms, we would have
an atmospheric burden that would be 44 plus 30.
And so the soils are responsible for keeping the atmospheric
concentration of methane at a much lower level than
it would be otherwise. Now what are we
doing to it though? We're shutting it off
with conventional agriculture. So we're asking the question,
is there a potential for cropping systems to be managed
somewhat differently, perhaps cellulosic crops could
play a role in this to produce a soil microbial community
that would be good at pulling methane out of the atmosphere.
And we see that there isn't much here that suggests that
we have that capacity with most cropping systems.
And it's not until we enter our midsuccessional system,
native vegetation, 50 or 60 years old, that we start
to get significant recovery of that methane oxidation.
So there is a potential for using cellulosic crops to
also lessen the methane burden. Okay, so how do you put this
together in a total system context at the field scale
in any case, to ask what are the different potentials across
these different cropping systems for doing this mitigation.
It's possible to build tables. I'm going to go quickly through
five or six similar tables here, and build a table that has
all of these systems in it. But I want to spend just
a minute talking about the first entry so you'll be able to track
better the next set of numbers. So in a conventionally tilled
system, a corn, soybean, wheat rotation, there's no change
in soil carbon, so there's no soil carbon contribution.
There is no contribution to either mitigation
or the CO2 burden in atmosphere from soil carbon changes in
a conventionally tilled system. There's about 27 grams of
CO2 equivalent per meter squared per year added to
accountable to that system based on the nitrogen fertilizer
that's applied. About the equivalent amount
based on the agricultural lime that's applied.
This is over a ten year period, actually over 20 year periods
now. There's a fuel cost of around
16 grams of CO2. And there's an N2O cost
of around 52. And a net mitigation,
a net credit for CH4 oxidation. There's a little bit going on,
but that gives us a total value of around 100 units
of CO2 equivalents being produced by this system.
So far it's at equilibrium. There's no annual change and
nitrous oxide is the largest source of CO2e in this system.
So if we switch to a no-till system, we can reduce this
net increase, this net contribution of cropping systems
to radiative forcing in the atmosphere by almost 100 units,
based almost entirely on the soil carbon sequestration.
And we count this as a negative, because it's pulling carbon
out of the atmosphere and storing it in soil.
There's a little bit of savings on fuel because no-till systems
use a little bit less fuel. But importantly, there's no
differences in nitrous oxide. The organic system has a net
somewhere in between the no-till and the conventional,
largely because we're getting a little bit of soil carbon
sequestration, which is a surprise, for other reasons.
But we have no inputs from fertilizer or lime.
But interestingly, the same burden of nitrous oxide as I
showed in the earlier bar graph. Now the perennial biomass crops
change this to a more favorable mitigation scenario, where we're
actually getting mitigation in this case, as a net effect.
So the alfalfa is sequestering a lot of soil carbon,
no doubt because it's perennial and the roots are in the system
and decomposing in place. They're not replanted each year.
No nitrogen fertilizer. We are adding a fair amount
of lime to counteract acidity. Only a little bit of fuel
compared to the annual crop existence, but again the same
amount of N2O leading to some mitigation.
The poplar trees bring this to a very substantial
net mitigation potential in these systems.
Minus 105, so we've got almost a 200 gram CO2 per meter squared
difference between the poplars and the conventional
tillage system. So that tells us that
we're on the right track here with providing some mitigation
services that are not available in the annual grain systems.
And again, it's partly because of the no-till
or restoring in carbon. But also notice in here,
we've cut down the N2O burden by almost a factor of six.
The successional communities are the ones that really provide
the most power for net mitigation here,
with almost a minus 200 twice out of the poplar.
So this is effectively a native prairie.
You could also think of this as a perennial grass.
That is, there's no reason to think functionally that
this shouldn't be any different from a C3, C4 grass mixture,
or even a complete single species mixture.
That's one of the questions we're investigating in
the center is, does it matter that this is a mixed species
community versus a monoculture switch grass community.
Switch grass is a native prairie grass, but just planting
a single species, may have some effects, as well as some risks,
that we wouldn't see in a mixed system.
But importantly here, the net effect drops off,
as you might predict, because of the soil carbon sequestration
to some midpoint here. And it disappears entirely
by the time you redevelop the late successional forest.
Okay, so it's possible to reconstruct a graph that looks
something like this for a total. These are effectively
the cellulosic biomass crops. These three systems
here in the middle. The alfalfa, the poplar and
the early successional systems. So quite apart from any benefit
that is obtained from substituting the carbon
from these systems for fossil fuel in the fuel mix,
there's this other aspect to their carbon economy
that needs to be kept in mind as we think about what's
the best design for these cropping systems in the future.
There is also a co-benefit. And this is one of the
interesting, and I think very potentially valuable aspects
to these cellulosic systems, as well, and that is because
these systems are perennial, they have roots in the ground
the whole year. They're growing the whole year,
in effect, whenever the temperatures are above
a certain point, there's still photosynthesis going on, which
means that there's still the potential for nitrogen uptake,
which means that any nitrate that might be in the soil, that
might otherwise wash through the system, would be available
for plant uptake. And in fact, we see that.
This is nitrate leaching over an 11-year period, where
we've had monitors in the ground beneath these crops, pulling
nitrate out and measuring the water flux by modeling,
and showing that conventional systems are leaching somewhere
on the order of 500 kilograms of nitrate over this period
per hector. But the cellulosic systems
are very low. In the case of the poplars,
we can't detect any leaching under the poplars.
We don't have the data yet for the native systems.
This is a paper that's just now being assembled.
So there's this other benefit that might also accrue
from building a landscape that includes not just annual crops,
but also some mixture of perennial crops that will
provide services that we're not getting now with these
almost monoculture and biculture landscapes.
And that's what we're aiming for.
We're aiming to design these systems.
So I want to take five or six minutes to just to review
what we're doing in the GLBRC with respect to sustainability.
And some of this ties into what I've been talking about,
but others of it is quite different.
So our overall objective is to support the biomass
and bioenergy pipeline by developing practices
that are economically viable and environmentally
responsible. And we're particularly
interested in carbon neutrality and greenhouse gas mitigation,
and also in quantifying the ecosystem services that could be
provided by biofuel landscapes. Now the way we're approaching
this is from a hierarchy of levels.
At the first level, we're looking at the development
of novel production systems. That is production systems based
on crops that now exist, or that will be developed as part
of the GLBRC activities in other research areas.
So eventually, we'll be having additional crops to think about
then, this wheat that we have now or improved varieties
of this wheat that we have now, that we'll be able to enter it
into the system. But we have two aspects
to production goals. One of them is defining what are
the novel production systems that will be the most
productive, that will provide the suite of services
that we want to encourage from these systems.
We can also think about what are the improved microplant
interactions that might lead to the improved performance
of these novel systems. All of these systems have
environmental responses and economic responses.
The environmental responses are the biogeochemical responses
that I've already described through the statisticians
at KBS, nitrogen and carbon cycling in particular.
There are also biodiversity responses.
That is what is the response of an insect community,
or a microbial community to 20 years of switch grass
or 20 years of poplar, versus 20 years of corn soybean
rotation. So there's going to be some
responses there that will be important to quantify.
Then, of course, there are economic responses also,
as the economy of these systems will be very different
depending upon a whole host of attributes.
So we'll take these responses and use them to inform models
at different geographic scales to eventually provide us
with information on what are the potential farm and landscape
designs that we could put out into these future agricultural
landscapes, and think about what are the regional and national
impacts of these designs. And that will help to inform us
as to what sort of additional changes we need to make
to the production systems in order to tweak the outcomes.
And eventually, it should provide us the information
needed to design the optimal configuration of landscapes,
who, as Pete Nowak was speaking to me this morning about,
how do we paint these landscapes in a way that optimizes
the ecosystem services that can be provided by these systems.
So a quick word about the approach we're taking to examine
all of these processes. As we've arranged a series
of ecosystems and series of cropping systems
along a gradient of high input low diversity,
to low input high diversity. With one end of the spectrum
being continuous corn, mainly for grain, but also for
the total biomass of the crop to a restored prairie, at
the other end of the spectrum. But also a number of other
systems, including poplars, early successional switch grass
systems, as well as a more environmentally benign--
It's not benign, but a more environmentally responsible
system than continuous corn. And then within each of these
different portions of the project, each of those
different circles that I had up on the previous slide were
examining specific hypotheses. And I'm not going to read
through all of these, but rather just quickly summarize that.
With any improved microbial plant interactions program,
we're looking at both organismic level, as well as
genomic level responses to improving the plant,
improving the ability of plants to take up nitrogen, to be more
nitrogen efficient, for example, or perhaps even more carbon
sequestering by manipulating the microbial community
in that system. Biogeochemical responses
are not just looking at the carbon cycle, but also
water use and nutrient loss, as I've already eluded to.
Biodiversity responses are looking at several targets,
including microbial biodiversity, but from the
standpoint of what we see, thinking also about
predatory and parasitic insects and their control in landscapes.
Bees, which provide pollination services, of course.
Game and song birds, as well as the microbes.
And all of these provide very quantifiable, and in some
respects, ecosystem services. And part of our challenge
in the economic portion of this is to quantify those ecosystem
services in ways that can inform policy a bit better than they're
currently being informed. And so in the economic arena,
we're interested in thinking about crop area change forecast
and the implications of that for the landscapes that we're
going to be seeing, so that if we build scenarios in which
we favor grain based alcohol, for example, that's going
to have a very different effect on land change, than one
in which we build policies that incentivize
cellulosic landscapes. We'll be able to look at that
in terms of ecosystem service valuation, in particular.
And then, the modeling component is at several different scales.
The objective is to build a framework that allows us
to run scenarios to forecast, what are the outcomes of these
different policy decisions, these different behavioral
decisions that we're making as a society, and how that
will effect, eventually, the CO2 concentration
in the atmosphere. That runs from the modeling.
This is my last slide. The modeling runs from the site
level, where we're using biophysical models to predict
carbon and nitrogen and plant growth.
All the way through landscape, regional, national and
global levels, where we're using integrated assessment models
to ask what does putting this much cellulosic biofuel
into the landscape, what effect does that have
on climate stabilization on CO2 stabilization,
knowing what we know about land use change,
about population growth, about technology innovation
and about climate change during that period, and so on.
So the integrated assessment models are those models that are
used to build the IPCC scenarios that predict CO2 concentrations
over the next century. And we have a group involved
in the center, who has built these IPCC models, and will be
using those models to predict the eventual outcome.
So I'm going to stop there and would be happy to take questions
in whatever time is available. I just want to summarize
very briefly by the comment that what we're talking about
with cellulosic systems is very different
from what we have now with our current generation
of ethanol plants. In that, we're not talking about
continuing the business as usual grain ethanol production,
but we're trying to shift the discussion and
shift the potential scientific understanding of the outcomes
to the cellulosic arena, because they're vastly different.
The environmental impact of cellulosic systems in the future
are just orders of magnitude different than they are for
grain-based alcohol production systems, which, to a very large
extent, are business as usual. Yes, we can make improvements
to those systems. You saw that in the conventional
systems that I had up there, in fact, the no-till system
was better, the organic system had specific attributes
that were good. So the low input
could improve those. But none of them send those
systems to net mitigation. The only systems
that send them to net mitigation are mainly the systems that are
perennial and produce above-ground biomass,
as opposed to seeds. So I'll stop there.
Thank you very much. ( applause )
Thank you, Phil. We do have time for questions.
But the other thing I'll say before I forget to say it later,
is we have some treats and goodies outside afterwards
to give people some more time to meet each other and to
talk to Phil or anyone else who's here.
So questions for Phil. And I need to run around.
Thanks for the very interesting talk.
You've got a slide in there that showed that emissions
from deforestation are actually declining and, of course,
we've been reading Science Magazine about concerns
about that with biofuel. And then, some of your other
charts with your early successional forests, I mean,
it seems like we might want to minimize carbon,
actually manage some of our forests for early succession.
And what you hear from a lot of folks is we need old growth.
What are some of your thoughts on that?
And what are the next steps to getting from the corn economy
to the biomass economy, in your eyes?
Your last question is the hardest, of course, and I don't
know if I'll be able to address that effectively.
But it's one that we need to think about
addressing effectively. Your first question about the
deforestation adding less CO2 to the atmosphere now
than it did in the 1990s. I was also surprised by that.
It doesn't take into account the additional deforestation
that's currently happening because of higher food prices.
This is a 2000-2006 period of analysis.
It was published in PNAS last year.
My expectation is that when we do the total 2000-2010 budget,
that it will probably show the same or an increase,
because of the clearing that's now happening,
because, in particular, because of the oil palm clearing
that's going on in Indonesia. We have peat soils
being exposed to oxidation with their very large carbon
contents, because they're being cleared for the oil palm
production. So I wouldn't put a lot of stock
in that small decrease in deforestation at this point.
The issue with respect to the successional vegetation.
You know, we have a lot of successional vegetation in
the Great Lakes region largely because of marginal lands
that are no longer, at least under 2005 grain prices, were
not considered profitable enough to clear and plant.
Now that may well change. And we're seeing more marginal
land coming under production this year I understand,
just because of the double grain prices.
And you might predict that. But there should be, and one of
my hopes, is that we can inform policy to the point that
eventually those systems that while they may be possible
with higher grain prices, still be profitable for the
standpoint of producing grain, they could be equally profitable
from the standpoint of providing above-ground
cellulosic material as feed stock.
And it might be even more desirable and profitable
if we figure out a way to provide incentives to farmers
to pay for those services that those systems now not crediting
for those services, the pollination services,
the clean water services, the carbon sequestration
services, and so on. A lot of those services
will stay, regardless of whether those systems
are cropped annually, that is, harvested annually,
if they're done right. That means you've got to harvest
them probably in the fall, and you've got to harvest them
with enough cover left over for the wildlife, the birds
in particular, over winter. But there are ways to do that
in a sustainable way, I'm convinced.
Now, I'm not sure that gets at your question with respect
to that. >> Do turning the poplars
over time with harvesting and replanting, do the emission
and sequestration approach those of a mature forest,
or do they stay higher as the initial planting?
Yeah, that's a great question.
Did everybody hear that? With respect to the poplars,
do you expect a decline in their mitigation potential
over time in the same way that you lose that mitigation
potential with a natural forest, with an old growth forest.
And the quick answer is, we don't know.
I would expect the N20 levels to stay just as low
as they are now. Simply because they're also low
in the old growth forest. Whether we can build
methane oxidation capacity in those systems
is yet to be determined. That is, those systems have only
been in place for 20 years. We haven't seen that capacity
yet, but we know that a 50-year-old field
has half of the capacity of an old growth forest.
So maybe in another 30 years, that poplar stand will provide
the additional oxidation, methane oxidation capacity
that is not now showing. With respect to carbon
sequestration in soil, we would expect it to plateau
at some point. It's certainly not
going to build up higher than the old growth forest, which
in our case around 3% carbon. We've got around 1.4% carbon
in the poplars now. Probably it will max out
at 2.0% is my guess. Again, there are no ecosystem
studies of biomass poplars that are longer than the ones
that we've got here. So we're really at the edge
of learning what those saturation periods are.
( inaudible ) >>...is not including,
especially an old forest, the both above ground
and below ground carbon pools. It seems like the most
you talked about the grades, but the very large carbon pools,
( inaudible ) >> So the question was, why
aren't we including the pools of carbon in the forest that
are now in place as part of the accounting.
And the answer is that we're interested in changes
in pools to calculate the impact on CO2 emissions
or CO2 sequestration. Now, it's not to diminish
the value of those old forests for storing the carbon
that they have. And this is the whole basis
for deforestation being a flux. Were we to cut those forests,
then they would turn into a flux and they would increase
the atmospheric burden of CO2. But as they are, at equilibrium,
there is no net change on a year-to-year basis
in carbon storage. That's the definition
of old growth. And so, there is no net,
either positive or negative impact on mitigation
or on the CO2 burden in the atmosphere.
So we don't count it for that reason.
Would you speculate what you think the possible feedback
from climate change might be on those balances across systems?
Is it likely that it will just move things up and down
or that they'll be differentially affected?
Yeah, that's another tough question.
And that's what we're hoping the modeling will help inform.
Climate change in the Great Lakes region is happening.
We're seeing an increase frequency in droughts
on the east side of the lake. We're also seeing changes
in snowfall duration or snowpack duration.
Of course, we're seeing the early onset of spring
relative to recent history. And understanding the impacts
of those changes on the future capacity of these
biofuel landscapes to produce as much as they could produce
in today's climate, it's an open question.
And the different models are showing, as I'm sure you're
aware, the different GCM models are showing different
precipitation changes, depending on which model you're using.
It's very difficult to predict the regional climate changes.
We see warming, for sure, and that's going to have
a big impact on lake level and groundwater flows, simply
because there will be a lot more transpiration happening,
so a lot more water vapor that would otherwise have ended up in
the groundwater and in the lakes will actually end up
back in the atmosphere. But beyond that prediction,
I don't know if we can go very far.
Certainly, however climate change effects cropping systems
in general, they're going to have a similar effect
on these cellulosic systems, with one exception.
And that is mid-growing season droughts, as we've had at KBS
for two of the last five years, will have a much lesser impact
on a perennial system than they will on our corn
and soybean systems. And so in that sense,
that's a good point. In that sense, the biofuel
systems, the cellulosic systems should be buffered from at least
that kind of variability, the intra-annual variability
in climate. >> So maybe we should take one
more and go out and have some coffee.
Two more. >> Two more, go ahead.
Sorry. >> I have read Tillman's
much publicized study about prairie biomass, and also have
seen your results, and wondered, those systems seem to offer
global impacts and net benefits in terms of global warming
impact, but they just aren't very productive.
And I wondered if at Kellogg or elsewhere, other work
you're familiar with, if people have tried fertilizing
either the poplars or say the early successional
old fields to see if you can still get most of those
benefits, but also greatly increase production?
Yeah, great question. So the question was
with native prairie systems, the data that's been published
thus far, and the advocates for those systems
are advocating systems that aren't as productive
as the monoculture, or even biculture grass systems.
And, it's true. On one of those initial slides,
I had productivity values for grasslands.
And those are grasslands that one might find in central Kansas
or in the Great Lakes region, which are on the order
of three to four metric tons per hector per year,
which is about half of what you could get, probably.
We don't know this for a fact, because we're doing
the experiment now. But probably, if we were to get
the same switch grass productivity that others have
found in a recent PNS paper in farms across South Dakota,
and Nebraska and so on, we would get about half
the productivity in an unfertilized grassland.
Now we do have fertilized old fields at KBS, and we
can show that we can boost the productivity of those
to around seven metric tons per hector.
So we can get equivalent yields from the old fields
as we can from the monoculture switch grass,
which is really interesting. Now the down side of that,
is that interest have been a lot of experiments all over
the U.S., all over Europe, as well, in the past 15 years
looking at the impact of fertilization on biodiversity.
And in general, fertilizing reduces plant biodiversity
in native prairie. And so the trade off there
would be greater productivity, but less plant biodiversity.
And that's why those who are proponents of native grasslands
haven't gone the next step, in saying, well what happens if
we fertilize those grasslands. Yes, you can boost productivity.
We know that. But at what cost.
If the aim is to increase biodiversity at the same time,
you're increasing cellulosic feed stocks, then you have to
ask how do you balance the biodiversity against
the increased productivity. That's one of these trade offs
that are going to be true in any kind of analysis
and important to understand. One final question, I hear?
Sort of two parts. One is just with your KBS
research, I'm just curious, how generalizable that is?
You showed at the beginning all these marginal lands
that could be utilized with different soil types in
the eastern U.S., for example. Also, I'm just kind of wondering
if in your analysis, you're going to be looking at, and
making comparisons to sort of second growth forests
as long-term sinks, sort of these general land uses
versus the biomass production, because I'm kind of imagining
from that first map you showed, abandoned lands
that could be reincorporated, you know, south eastern Ohio.
I'm from Ohio, so I'm picturing kind of poplar plantations
harvested every 20 years there, versus the second growth forest
that's probably there now. That's a really different
landscape, and if those are getting converted, you might be
gaining, you know, you can store extra carbon in the soil,
but the above ground processes and the ecosystem
has really changed. >> You might have
equivalent productivity for either of those two systems,
poplar or secondary forests, depending on how their managed.
I should say unfertilized poplar.
Right now, our unfertilized poplar, and our poplar is
unfertilized, because we put it in as a biofuels crop
back in 1988, when the thought what is that we would
only be growing biofuel crops on marginal land, and farmers
would only be interested in them because they didn't require
any inputs. That is to say that they
didn't really have much value, economic value.
So we decided at the outset to manage these
as effectively unmanaged, but initially planted poplars.
And the productivity in those stands is quite high.
It's about 10 metric tons per hector per year.
But a successional forest, once it gets to a certain point,
you might expect a similar sort of productivity,
some fraction of that. There again, you have to ask,
you know, what trade offs are you willing to make.
Do you really want monoculture poplar stands across
south eastern Ohio versus successional forests that might
be a little less productive, but might provide all of those
other biodiversity services that a monoculture poplar can't.
So I think those are exactly the kind of questions
we need to consider, as we think about what are the
optimal landscapes for biofuels. I mean there's no question--
I shouldn't say there's no question.
There's little question that we're going to be moving
into this economy, we've already started.
And we now need to make choices. Well, we really don't want the
equivalent of Iowa corn fields covering all of what is now
in successional forests across the U.S., planted
to a similar woody monoculture. So we need to be having
the discussions and be thinking about how to quantify
the biodiversity benefits in addition to the strict
biofuel benefits. As far as KBS being
generalizable, we're looking at ecological processes
in these systems. And these processes occur
everywhere. Because we're comparing systems
we would expect the same sort of comparisons to hold,
the same sort of differences to hold, no matter whether
you're on a KBS alpha soil with a rainfall
of about a meter per year, or you're in south eastern Iowa
on less soil with a little bit less precipitation.
The relative differences should be the same.
So not exact, of course. >> I want to thank Phil again,
and invite everyone to come on outside to have some coffee
and talk for a while. ( applause )