[Scpg] The Dirt on Climate Change By Peter Friederici Miller-McCune Jan/Feb 2010

[Wesley Roe and Santa Barbara Permaculture Network]

The Dirt on Climate Change
Could soil engineered specifically to maximize 
carbon storage dampen some effects of climate 
change? Very possibly.
By Peter Friederici
http://www.miller-mccune.com/science-environment/the-dirt-on-climate-change-6524/

"Imagine all the organic stuff that comes into a 
city - and then imagine putting all that carbon 
into the soil," said William Woods, University of 
Kansas geographer.
RELATED STORIES
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Conflicts tend to scatter people, and ideas, in 
unexpected ways. After the American Civil War, a 
flood of so-called Confederados fled the 
devastated South and set up farms in the 
Brazilian Amazon. They planted rice and sugar 
cane and tobacco, and they prospered. But the 
lands they settled - primarily high bluffs along 
rivers - weren't any more pristine than Alabama 
or the Carolinas had been. As they plowed, the 
settlers unearthed vast quantities of potsherds 
that showed the land had been inhabited before. 
And the ceramics weren't the only sign of 
previous human cultivation: The deep black earth 
itself, very different from the pale, 
nutrient-poor soils of much of the Amazon, 
quickly revealed that people had been 
indispensable in creating its fertility.

"The rich terra preta, 'black land,'" of one 
settlement was "the best on the Amazon. Š a fine, 
dark loam, a foot, and often two feet thick," 
wrote an American naturalist named Herbert Smith 
in 1879. "Strewn over it everywhere we find 
fragments of Indian pottery. Š The bluff-land 
owes its richness to the refuse of a thousand 
kitchens for maybe a thousand years."
Though they have always been prized by farmers, 
the dark soils of the Amazon were largely 
forgotten by science for a century after their 
discovery. They are now re-emerging as an 
important topic of study, not because

they're an ethnographic or historical curiosity, 
but because they show an exceptional ability to 
store carbon, which in the form of carbon dioxide 
has rapidly turned into one of humanity's most 
pernicious waste products. As a result, they're 
joining the rapidly growing roster of tactics 
that might be used to combat climate change. 
Researchers around the world are considering 
whether people may, by engineering soils 
specifically to maximize carbon storage, be able 
to absorb substantial amounts of our emissions, 
increase the fertility of agricultural areas and 
dampen some of the effects of climate change.
Sound utopian? Maybe. But as the long aftermath 
of the Civil War shows, solutions to deeply 
ingrained social problems often do emerge - 
though not always quickly and certainly not 
without enormous and sustained effort.

"We could gear up for this with something like 
the Manhattan Project," says William Woods, a 
University of Kansas geographer and expert on 
terra preta. "Imagine all the organic stuff that 
comes into a city - and then imagine putting all 
that carbon into the soil. It works, though we 
aren't there yet. So far no one seems to have the 
will do it."

Carbon is the essential building block of all 
life, the bustling captain of industry, the stuff 
at the core of diamonds. Carbon has long starred 
quietly in virtually everything that goes on in 
human lives, but now its blandly essential air 
has been eclipsed by a new role: that of villain 
in the long-running drama of climate change. As 
the key component of carbon dioxide, element 12 
has now firmly moved in the public mindset from 
good guy to a problem that threatens the future 
of the very lives it has made possible.
Carbon dioxide isn't the only greenhouse gas out 
there - methane, the nitrogen trifluoride used in 
the manufacture of flat-panel televisions, and 
others contribute to global climate change, too - 
but it is the most widespread and the one most 
directly associated with the industrial 
revolution. Combustion begets CO2, simply, and as 
that extra gas accumulates in the atmosphere, it 
causes the Earth to retain more heat. The litany 
of effects that result from that warming is 
becoming increasingly well known: rising oceans, 
more severe heat waves, irregular precipitation, 
greater threat of drought. So is the precise 
concentration of carbon dioxide in the 
atmosphere, which has been rising steadily since 
humans started burning a lot of coal in the 19th 
century - and which is currently rising at a rate 
faster than anticipated by most of the 
predictions made by the Intergovernmental Panel 
on Climate Change.
Carbon helps form the organic molecules that 
comprise pansies and panthers, redwood trees and 
blue whales. When these organisms die, the carbon 
in them eventually returns to the environment, 
often by oxidation as carbon dioxide. How much 
carbon a given ecosystem stores, then, is a 
matter of dynamic flux that can be measured on a 
variety of different time scales. Some ecosystems 
can store carbon effectively enough that 
scientists refer to them as "carbon sinks" - that 
is, they hang onto carbon for decades or 
centuries, long enough that they contribute to 
lowering atmospheric concentrations of CO2 and 
perhaps reduce the impacts of climate change. 
Grow a forest, and it accumulates carbon slowly, 
perhaps for centuries. Burn it down in a severe 
fire, and most of its carbon goes up in smoke. 
Cut it down for lumber and the carbon in that 
wood may lie undisturbed for centuries, while 
that in the leaves, unharvested branches and 
disturbed soil is quickly released into the 
atmosphere. Other ecosystems follow the same 
pattern but so much more quickly that no one 
refers to them as carbon sinks: In June, an Iowa 
cornfield rapidly sequesters carbon as the crop 
plants grow; in November, it releases the element 
as the chopped stalks degrade.

But it's not just plants and animals that hold 
carbon. Soils do, too, a lot of it - an estimated 
2.5 trillion tons worldwide, or more than three 
times the amount floating around in the 
atmosphere and about four times as much as in all 
the world's living plants. About 60 percent of 
the soil's carbon is in the form of the organic 
molecules that compose living things, while the 
other 40 percent is in inorganic forms such as 
calcium carbonate, the crusty salt common in 
desert soils. Unfortunately, people have not been 
very kind to the soil's pool of organic carbon, 
at least not since the dawn of agriculture. 
According to the IPCC, human beings were 
responsible for the emission of about 270 billion 
tons of carbon from the burning of fossil fuels 
between 1850 and 1998. During the same period, 
they caused the loss of about half that much 
carbon from terrestrial ecosystems through such 
activities as logging and plowing; all told, 
disturbances to soils during that century and a 
half caused the emission of about 78 billion tons 
of carbon. In other words, though the burning of 
fossil fuels is the main culprit in climate 
change, our land uses have played an important 
supporting role.

"If you convert from prairie or forest to 
agriculture, the soil's organic carbon decreases 
very rapidly," says Rattan Lal, the director of 
the Carbon Management and Sequestration Center at 
Ohio State University. "It can decrease by as 
much as 30 to 50 percent in a relatively short 
time. Most soils in Ohio have lost between 10 and 
40 tons per acre of carbon because of blowing, 
drainage, erosion, removal of crops for feeding 
cattle, removal for biofuels and other factors. 
The carbon storage capacity of these soils is 
like a cup that's now only half full."
To soil scientists such as Lal, humanity's recent 
history with dirt constitutes a triple whammy. 
All the carbon that's been removed from soils has 
helped to push up carbon concentrations elsewhere 
in the biosphere, whether in water, where it 
contributes to the acidification of the oceans, 
or in the air, where it contributes to the 
baleful effects of climate change. As soils have 
lost carbon, they also have lost a good deal of 
their productivity. They store less water, harbor 
fewer microorganisms, are less able to transfer 
nutrients to plant roots, require more 
fertilizer. In their impoverished form, they're 
also less able to store carbon than they once 
were. They've gone from sink, in many cases, to 
source.
That's a big problem, Lal says, but he is one to 
see soil's cup as half full, rather than as half 
empty: Saving the planet's soils, he says, may 
also mitigate at least some of the impacts of 
climate change. And it's vital, too, for the most 
visceral of reasons.
"We have 6.7 billion people now," he says. "We'll 
have 10 billion in a few more decades. How are we 
going to feed them if we don't take care of our 
soils?"
Plants have countless benefits, but to 
climatologists they're basically pumps that 
channel carbon from the atmosphere as they 
photosynthesize. They use much of it in 
constructing their own lasting tissues, but they 
also transmit a lot of it as they absorb 
nutrients from soil. According to David Manning, 
a soil scientist at the University of Newcastle, 
plants move about as much carbon underground as 
they do into wood and leaves.
"When we normally think about fixing carbon by 
plants, we think about forests," he says. "But 
when you see the carbon stored in a forest, you 
have to think that there's as much underground as 
there is aboveground. It comes out through the 
roots as a complex cocktail of compounds, such as 
citric acid, that break down the nutrients in the 
soil."
This function of plants happens to connect the 
organic and inorganic roles of carbon. Most of 
the carbon in soils is in organic material - it's 
the rich brown stuff that makes a vegetable 
garden thrive. But many soils also contain a lot 
of carbon in highly stable, inorganic forms such 
as calcium carbonate. That's well known to 
farmers and ranchers in the western United States 
and other arid regions, where a hard white crust 
known as caliche often forms on or within soil. 
These carbonates form readily where insufficient 
rain falls to wash them away, but Manning has 
found that they also form, often at greater 
depths, even in climates as wet as Britain's. All 
that's needed is a source of calcium, and the 
right plants to emit carbon through their roots.

As it happens, people have inadvertently been 
putting calcium into British soils for hundreds 
of years. When buildings are demolished and their 
bricks, mortar or concrete debris discarded, 
calcium is freed up. Manning's research team has 
found that urban sites in that country can 
sequester as much as 10 tons of carbon per acre 
each year, not by the creation of organic 
material but rather by the formation of 
long-lasting carbonates.
"It's fascinating," he says. "We bring up old 
house bricks, and they're covered with lumps of 
calcium carbonate. Typically we find that the 
urban soils we look at contain up to about 20 
percent calcium carbonate."

Though this process takes place on its own, 
Manning thinks that careful planning could help 
speed it up. For example, choosing the right 
sorts of plants for urban landscaping could 
maximize the production of carbonates. He notes, 
though, that this sort of carbon sequestration in 
urban soils is a zero-sum game. The manufacture 
of cement produces huge amounts of carbon 
dioxide, and waste construction or demolition 
debris in soil can never bind to more carbon than 
has been produced in its manufacture.

"The scale of production of cement is so great 
that you could never do more than compensate for 
the production process," he says. "But this can 
help close the loop. It may help get rid of the 
word 'waste,' which is a horrible word. And if 
carbon trading really takes off, then to be able 
to demonstrate that the carbon on your site has 
ended up as carbonate might have a value."

In theory, people may be able to remove large 
amounts of carbon from the atmosphere by taking 
advantage of the caliche formation that goes on 
naturally in the world's vast arid areas. Calcium 
is readily available in natural form in seawater, 
so why not simply put a lot of it on desert soils 
to form lots of carbonate and remove CO2 from the 
atmosphere?
"We could probably sequester vast amounts of 
carbon by adding calcium to desert soils," notes 
Curtis Monger, a soil scientist at New Mexico 
State University who studies carbonate formation. 
"But at what point do we become concerned about 
turning our desert soils to stone? Whenever we 
talk about global-scale geoengineering, we don't 
mean to, but we tend to mess things up."

It's difficult to discuss the modification of 
desert soils as a carbon-sequestration strategy 
in much detail because these soils are little 
understood at this point. Several teams of desert 
researchers, including Monger's, have been 
surprised in recent years to find that tracts of 
arid land seem capable of absorbing far more 
carbon dioxide than can be explained according to 
standard models of how these ecosystems work. He 
remembers one experiment in which his team was 
measuring CO2 being emitted from soil, only to 
find that the gas was suddenly sucked back down 
into the earth.

"We wondered whether our instruments were 
screwy," Monger says. He thinks that light 
precipitation may have caused a sudden surge in 
carbonate formation, removing the gas. But he 
notes that the study of desert soils, especially 
of their link to the global carbon cycle, is in 
its infancy.
"It's the quiet before the storm," he says. "The 
IPCC still hasn't recognized desert soils and 
calcium carbonate as a big player. But it will."
If the soils of desert areas are a wild card in 
the high-stakes game of climate change, biochar 
is increasingly coming to look like a royal flush 
- a reliable winner. The idea behind it is very 
simple: To get rid of unwanted carbon, put it 
directly into the soil. Farmers do this all the 
time, of course, when they till the harvested 
parts of crop plants back into a field - but 
under typical agricultural conditions some 90 
percent of the carbon in these residues quickly 
winds up back in the atmosphere. The idea behind 
biochar, instead, is to convert that carbon 
before plowing it under by first turning it into 
durable charcoal.
That's exactly what the native peoples of the 
Amazon were doing for many centuries before 
Spanish and Portuguese explorers arrived. 
According to geographer Woods, the large-scale 
use of biochar in South America probably arose 
some two-and-a-half millennia ago, at about the 
time that corn was becoming a widespread food 
crop. This ready source of food led to increased 
human populations, centralized villages and 
pressure to increase yields. It could not have 
taken long before farmers observed where the 
lastingly fertile soils were: namely, in the 
places where charcoal and organic wastes were 
discarded.
"They're seeing that this stuff is fertile; 
they're putting their gardens there; and it's not 
a big step from there to creating it 
deliberately," Woods says. "The carbon in the 
form of charcoal is an integral part of these 
soils, and it happens to take a great deal of 
carbon out of the atmosphere."

Those farmers didn't need to worry about climate 
change, but they were taking advantage of a 
fundamental property of carbon in the form of 
charcoal: It has a complicated structure, and it 
lasts a long time. That's why charcoal does such 
a good job as a filter. Its complex structure 
provides many places where other molecules can 
linger, whether they're impurities in whiskey or 
nutrients that plants need. As a result, soil 
fertility can increase a great deal when charcoal 
is combined with organic materials that provide 
nutrients. Those terra preta soils in the Amazon 
don't just contain much more organic material 
than other soils; they also hold onto potassium, 
phosphorus and numerous trace minerals much more 
readily and provide much better microhabitats for 
such important organisms as bacteria and fungi. 
And because charcoal takes so long to break down, 
terra preta soils retain their fertility much 
longer than those of other tropical areas.
Robert Brown began thinking about biochar as a 
side effect of working on gasification, which is 
a means of converting organic materials into 
energy with great efficiency by first turning 
them into a gas, then burning them. Brown, an 
engineer at Iowa State University, was struck by 
how difficult it is to burn the last small bits 
of charcoal even in the hottest and cleanest of 
fires. Fine, he thought - the charcoal, after 
all, is a carbon sink, and because it's itself a 
filter, it is not a pollutant.

"My notion was we had to put it in old coal mines 
to get rid of it," he says. "But in fact it's so 
recalcitrant that you can just bury it in soil to 
get rid of it."
Brown and colleagues are currently working on a 
small pilot plant that will convert unneeded 
organic material from Iowa cornfields into 
ethanol and charcoal. The idea is that farmers 
wouldn't harvest only ripe ears of corn come 
fall; they'd also harvest about half of the 
remaining plant fiber - which farmers call 
stover. Then they'd drive the stover to a nearby 
plant, where gasification and a reaction with a 
catalyst would turn the biomass into ethanol and 
some fine particles of leftover charcoal - about 
300 pounds of it for every ton of stover. The 
latter could then be applied to fields, where it 
would both enhance soil fertility and act as a 
carbon sink. The corn stalk-based ethanol, 
meanwhile, wouldn't compete with food production 
in the way that ethanol produced from corn 
kernels does.
If charcoal would increase the health of Iowa's 
soils, Brown says, think of how much more it 
would help generally nutrient-poor tropical 
soils: "I think this could be a revolution for 
agriculture. It could dramatically increase the 
efficiency especially of tropical agriculture. If 
you were to establish a farm and sequester carbon 
there, you'd not only produce crops but improve 
the soil, too. So you wouldn't have to burn down 
another tract of forest a few years down the 
road."

Still, there a lot of kinks to be worked out 
before what manifestly works in the lab can be 
put into action in an Iowa cornfield, or in the 
Brazilian jungle. A number of researchers and 
entrepreneurs are trying to resolve some of those 
issues, by designing and testing the gasification 
burners that would be required, or calculating 
what other nutrients would need to be applied 
along with biochar to maximize soil productivity. 
But it's likely that some of the thorniest issues 
will play out on the ground. Some observers worry 
that biochar will become such a promising means 
of combating climate change that its production 
will trump other values; they envision nightmare 
scenarios in which huge tracts of forest are axed 
only for the value of the charcoal they can 
produce. As Monger points out, large-scale 
geoengineering always seems to bring out a new 
set of problems.
"You have to think about it from a sustainability 
perspective," says Johannes Lehmann, a leading 
biochar expert at Cornell University. "It makes 
no sense to use pristine rainforest for biochar 
production, or to produce biochar in Iowa and 
ship it to West Africa. Biochar should not be 
seen as an alternative to best management 
practices, but in addition to them."
If biochar is beginning to seem like a sort of 
silver bullet that would allow us to shoot our 
way out of our climate quandary, then it's time 
to take a deep breath. It's not. Though many 
questions about it remain to be answered, its use 
may indeed prove a relatively inexpensive way to 
improve soil fertility, to find a productive use 
for many products - especially agricultural 
leftovers - that are currently considered waste 
and to sequester some carbon. But the harsh 
reality of the carbon cycle, and of climate 
change, is that there is no single solution that 
can get humanity out of its self-inflicted crisis.
A number of scientists have tried to estimate how 
much carbon people may be able to pump out of the 
atmosphere through the application of biochar. In 
a recent paper, James Hansen, the NASA scientist 
who has been a prominent voice on climate change 
for many years, and colleagues estimated that 
large-scale adoption of biochar sequestration 
could reduce atmospheric CO2 by about 8 parts per 
million by 2050. Ohio State's Rattan Lal claims 
that widespread use of biochar, in conjunction 
with other wise agricultural stewardship such as 
erosion control and no-till farming, could 
sequester some 1.25 trillion tons of carbon a 
year. By itself, that could cause atmospheric CO2 
levels to drop about 50 ppm over the next century.

That's a lot, but still far from enough, given 
that the current level of CO2 is 387 ppm - up 
from about 315 in the late 1950s - and rising at 
the rate of about 2 ppm per year. Climatologists 
point out that the global carbon cycle appears to 
be experiencing some feedback loops through which 
warming begets more warming. As ice in the Arctic 
and on mountain glaciers melts, the newly exposed 
water or land surface is darker and absorbs more 
energy from the sun. As Arctic tundra warms, 
frozen peat decomposes, releasing both carbon and 
methane - itself a potent greenhouse gas. As 
once-lush forests dry out, they're more subject 
to large-scale fires that release enormous 
amounts of carbon dioxide. As the oceans warm, 
they become less able to absorb CO2 from the 
atmosphere. And so on - the list is dispiriting.

Hansen and a number of his colleagues have called 
for a target CO2 concentration of 350 ppm to 
avoid some of the worst effects of runaway 
climate change. As the human population and its 
energy demands both grow, there will be no way to 
get there without a widespread embrace of 
numerous conservation and sequestration tactics. 
It's politically tricky to both reduce emissions 
and increase carbon sequestration at the same 
time; embracing a solution with the potential to 
store lots of carbon may reduce the imperative to 
reduce carbon emissions in the first place. As 
Lehmann told the U.S. House Select Committee for 
Energy Independence and Global Warming in June, 
"Biochar must not be an alternative to making 
dramatic reductions in greenhouse gas emissions 
immediately, but it may be an important tool in 
our arsenal for combating dangerous climate 
change."
About a week after Lehmann testified, the House 
passed a climate bill that includes a 
cap-and-trade system giving polluters incentives 
to pay to offset their carbon emissions.

Though many environmentalists criticized the bill 
as far too little, far too late, it at least 
opens the door to valuing projects that sequester 
carbon as an offset to emissions and dovetails 
nicely with the potential for finding money to 
pay for the widespread application of biochar.

It may be, then, that future farmers - much like 
those of the ancient Amazon - will ultimately be 
judged not only on what they can extract from the 
soil but also on what they put in. To biochar 
advocates such as Rattan Lal, that's a step in 
the direction of good stewardship - and good 
economics.

"Let us pay farmers for ecosystem services," he 
says. "If they improve the quality of their 
soils, if it's good for erosion control, for 
biodiversity, for climate mitigation - let us pay 
them for those services."
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