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    Taiwan's Feng Chia University has succeeded in boosting the production of hydrogen from biomass to 15 liters per hour, one of the world's highest biohydrogen production rates, a researcher at the university said Friday. The research team managed to produce hydrogen and carbon dioxide (which can be captured and stored) from the fermentation of different strains of anaerobes in a sugar cane-based liquefied mixture. The highest yield was obtained by the Clostridium bacterium. Taiwan News - November 14, 2008.

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Monday, November 10, 2008

Scientists suggest carbon dioxide levels already in danger zone - urge investments in carbon-negative energy, biochar

If climate disasters are to be averted, atmospheric carbon dioxide (CO2) must be reduced below the levels that already exist today, according to a study published [*.pdf, open access] in Open Atmospheric Science Journal by a group of 10 scientists from the United States, the United Kingdom and France. Reducing atmospheric CO2 levels is only possible by means of carbon sequestration and the production of carbon-negative bioenergy. In practise, the scientists urge us to end coal emissions and at the same time launch bioenergy with carbon sequestration systems, tree planting campaigns, anti-deforestation efforts and biochar initiatives. Ordinary renewables like wind and solar can help, but they do not suffice because they are merely 'carbon-neutral' and are incapable of actively withdrawing CO2 from the atmosphere.

The authors, who include two Yale scientists and NASA's Dr James Hansen, assert that to maintain a planet similar to that on which civilization developed, an optimum CO2 level would be less than 350 ppm — a dramatic change from most previous studies, which suggested a danger level for CO2 is likely to be 450 ppm or higher. Atmospheric CO2 is currently 385 parts per million (ppm) and is increasing by about 2 ppm each year from the burning of fossil fuels (coal, oil, and gas) and from the burning of forests.
This work and other recent publications suggest that we have reached CO2 levels that compromise the stability of the polar ice sheets. How fast ice sheets and sea level will respond are still poorly understood, but given the potential size of the disaster, I think it's best not to learn this lesson firsthand. - Mark Pagani, Yale professor of geology and geophysics
The statement is based on improved data on the Earth's climate history and ongoing observations of change, especially in the polar regions. The authors use evidence of how the Earth responded to past changes of CO2 along with more recent patterns of climate changes to show that atmospheric CO2 has already entered a danger zone.

According to the study, coal is the largest source of atmospheric CO2 and the one that would be most practical to eliminate. Oil resources already may be about half depleted, depending upon the magnitude of undiscovered reserves, and it is still not practical to capture CO2 emerging from vehicle tailpipes, the way it can be with coal-burning facilities, note the scientists. Coal, on the other hand, has larger reserves, and the authors conclude that "the only realistic way to sharply curtail CO2 emissions is phase out coal use except where CO2 is captured and sequestered."

In their model, with coal emissions phased out between 2010 and 2030, atmospheric CO2 would peak at 400-425 ppm and then slowly decline. The authors maintain that the peak CO2 level reached would depend on the accuracy of oil and gas reserve estimates and whether the most difficult to extract oil and gas is left in the ground.

The authors suggest that reforestation of degraded land and improved agricultural practices that retain soil carbon - especially biochar systems - could lower atmospheric CO2 by as much as 50 ppm. They also dismiss the notion of "geo-engineering" solutions, noting that the price of artificially removing 50 ppm of CO2 from the air would be about $20 trillion. Instead, the scientists suggest the following actions:
Desire to reduce airborne CO2 raises the question of whether CO2 could be drawn from the air artificially. There are no large-scale technologies for CO2 air capture now, but with strong research and development support and industrial scale pilot projects sustained over decades it may be possible to achieve costs ~$200/tC or perhaps less. At $200/tC, the cost of removing 50 ppm of CO2 is ~$20 trillion.

Improved agricultural and forestry practices offer a more natural way to draw down CO2. Deforestation contributed a net emission of 60±30 ppm over the past few hundred years, of which ~20 ppm CO2 remains in the air today.

Reforestation could absorb a substantial fraction of the 60±30 ppm net deforestation emission.

Carbon sequestration in soil also has significant potential. Biochar, produced in pyrolysis of residues from crops, forestry, and animal wastes, can be used to restore soil fertility while storing carbon for centuries to millennia. Biochar helps soil retain nutrients and fertilizers, reducing emissions of GHGs such as N2O. Replacing slash-and-burn agriculture with slash-and-char and use of agricultural and forestry wastes for biochar production could provide a CO2 drawdown of ~8 ppm or more in half a century.

[In the Supplementary Material Section] we define a forest/ soil drawdown scenario that reaches 50 ppm by 2150. This scenario returns CO2 below 350 ppm late this century, after about 100 years above that level.

More rapid drawdown could be provided by CO2 capture at power plants fueled by gas and biofuels [that is: carbon-negative bioenergy]. Low-input high-diversity biofuels grown on degraded or marginal lands, with associated biochar production, could accelerate CO2 drawdown, but the nature of a biofuel approach must be carefully designed.

A rising price on carbon emissions and payment for carbon sequestration is surely needed to make drawdown of airborne CO2 a reality. A 50 ppm drawdown via agricultural and forestry practices seems plausible. But if most of the CO2 in coal is put into the air, no such “natural” drawdown of CO2 to 350 ppm is feasible. Indeed, if the world continues on a business-as-usual path for even another decade without initiating phase-out of unconstrained coal use, prospects for avoiding a dangerously large, extended overshoot of the 350 ppm level will be dim.
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While they note the task of moving toward an era beyond fossil fuels is Herculean, the authors conclude that it is feasible when compared with the efforts that went into World War II and that "the greatest danger is continued ignorance and denial, which could make tragic consequences unavoidable."

There is a bright side to this conclusion. Following a path that leads to a lower CO2 amount, we can alleviate a number of problems that had begun to seem inevitable, such as increased storm intensities, expanded desertification, loss of coral reefs, and loss of mountain glaciers that supply fresh water to hundreds of millions of people. - James Hansen, lead author, Columbia University

In addition to Hansen and Pagani, authors of the paper are Robert Berner from Yale University; Makiko Sato and Pushker Kharecha from the NASA/Goddard Institute for Space Studies and Columbia University Earth Institute; David Beerling from the University of Sheffield, UK; Valerie Masson-Delmotte from CEA-CNRS-Universite de Versaille, France Maureen Raymo from Boston University; Dana Royer from Wesleyan University and James C. Zachos from the University of California at Santa Cruz.

Graph: Atmospheric CO2 if coal emissions are phased out linearly between 2010 and 2030, calculated using a version of the Bern carbon cycle model. Credit: Hansen, et al/Open Atmospheric Science Journal.

James Hansen, Makiko Sato, Pushker Kharecha, David Beerling, Robert Berner, Valerie Masson-Delmotte, Mark Pagani, Maureen Raymo, Dana L. Royer, James C. Zachos, "Target Atmospheric CO2: Where Should Humanity Aim?", Open Atmospheric Science Journal, Volume 2, 217-231 (2008), doi: 10.2174/1874282300802010217 [alternative link to the paper].

Dr James E. Hansen

Mark Pagani, Yale University: Geology and geophysics

Robert Berner


Anonymous Jan Hollan said...

Please, use the official OAS Journal site, where the paper has a corrected character spacing now. And where the important "Supplementary material" part is availale, too.

Jenik Hollan

5:55 PM  
Anonymous Jonas said...

Jan, there's no direct link to the OASJ paper. That's why we uploaded it to a separate server.

I'm sure the reader will consult OASJ if he wants to.


9:11 PM  

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