Tag Archives: carbon emissions

A Look at Carbon Capture and Storage

Global warming has become an accepted phenomenon in the scientific community.  The consensus is that anthropogenic activities are dominant factors in this rapid climate change.  An increase in violent storms and severe droughts are becoming a normal occurrence on a global scale.  The impacts of one species have never before induced global changes in climate.  Limiting global temperature rise to 2 °C above preindustrial temperatures has become an accepted broad political consensus worldwide (1, 3).  The combustion of fossil fuels has been identified as the major contributor to climate change (1, 5, and 7).  Climate change predictions set a deadline of 2020 to significantly reduce greenhouse gases in order to mitigate anthropogenic effects on global warming (3).  Urgent action is needed.

world CO2 by fuel typeworld CO2 emissions per capita

Carbon capture and storage (CCS) has the potential to play a significant role in limiting climate change.  Future global emissions from the combustion of fossil fuels can potentially be reduced by 20% with the implementation of CCS (4).   Currently 3 megatons of CO2 (MtCO2) per year by pilot plants is already being captured from the emissions caused by natural gas cleanup and power plants.  The CO2 is then being stored in geologic formations (3).  Unfortunately, at the present there is a serious lack of funding to provide for new construction of CCS.  This fact will push the learning from these first pilot projects well beyond the year 2020 (3).  Additionally, another drawback to CCS will be the inevitable incremental costs incurred.  For example in the U.K., additional costs per year per household may be increased as much as 10% as a result of CCS implementation (3).

There are three methods of CCS currently under investigation.  Pre combustion capture is a process that chemically strips off the carbon leaving only hydrogen to burn.  Oxyfuel combustion burns coal or gas in the presence of denitrified air to yield only CO2 and water.  Post combustion uses chemical solvents to capture the CO2 from the flue gases (1, 2, and 3).   Captured CO2 is then fluidized by pressurizing to 70 bars.  This liquefied CO2 is next transported to a storage site where it can be injected to depths greater than 800m (2, 3).  The selection of storage sites is critical and will require monitoring for leakage for many decades to come.  Additionally, methods to re-mediate deficient storage will need to be readily put into place (1, 2, and 3).  Many of the techniques already being practiced by the oil and gas industry will function quite well as modeling and monitoring tools for CO2 storage.  However, as learning progresses these techniques will need to be evaluated for strengths and weaknesses.  Some examples of these techniques are: horizontal drilling to provide for cost effective storage, modeling techniques to predict groundwater displacement, CO2 migration, CO2 distribution and immobilization, seismic monitoring to image location of underground CO2, and borehole monitoring to heed early warnings of seepage (2, 3).   Teng et. al (2005) have analyzed some theoretical outcomes to physical and economic outcomes of carbon storage with leaking.  Their research highlights the need for critically essential decisions in reservoir selection, project design, and plant operation to avoid project failure (6).

At the moment the largest barrier to deployment of more CCS pilot plants is not a technological barrier but a market barrier.  Current demonstration coal plants have required additional capital in the range of $1.5 billion to complete construction.  Demonstration plants also have the barrier of recovering the operational costs of producing decarbonized electricity (3).  Critical commercial help and subsidies are needed for large scale up of CCS.  Haszeldine (2009) points out that price supports currently used to support renewables are actually supporting a more expensive option per energy unit than it would if it supported the deployment of CCS.  Rapid deployment of CCS is needed to promote learning.  Additionally, the sharing of detailed commercial information instead of tightly controlled company secrets commonly associated with competitive development will be help to straighten the learning curve of a much needed technology (3).

My colleagues seem to have mixed views on the practice of CCS.   The reliability of CO2 available to inject for enhanced oil recovery is a serious dilemma.  How can we implement CCS on a grand scale without the Co2 delivery infrastructure in place?  It is my opinion that this is only a reality because we have not been able to convince investors or the public that CCS is a reliable and safe science for us to be practicing.   It is true.  Until a CO2 distribution network is constructed, a reliable source of CO2 will be a pressing concern.  The practice of CO2 injection for enhanced oil recovery (EOR) has been going on for decades.  EOR is being practiced in areas where we have already disturbed the natural development of the earth.  It seems to me that one of the biggest fears for my colleagues is what will be the consequences of this CO2 injection?  This is also a concern of mine.  It perplexes me that some are so willing to accept similar risks with hydraulic fracturing, but they are not willing to trust the science behind CCS.

Another fascinating topic raised by one of my colleagues was the idea of pore space ownership.  Just like many battles have been fought over the ownership of groundwater, I foresee the same thing happening with CO2 sequestration.  Who will really own the pore space underground?  On the borders of conflicting countries it’s not so simple.  If you use Texas as an example, the wise governing bodies of Texas legislature have given the landowners the right to the resources below them, unless they have sold them off.

1Environmental Non-Government Organisation (ENGO) perspectives on Carbon Capture and Storage (CCS)., 2012.  http://cdn.globalccsinstitute.com/sites/default/files/publications/55041/engo-perspectives-carbon-capture-storage.pdf

2Gibbins, J., and Chalmers, H., 2008, Carbon capture and storage: Energy Policy, v. 36, p. 4317–4322.

3Haszeldine, S.R., 2009, Carbon capture and storage: how green can black be?: Science, v. 325, p. 1647–1652.

4International Energy Agency, 2010, Energy Technology Perspectives: , p. 458.

5Metz, B., Davidson, O., Coninck, H. de, Loos, M., and Meyer Leo, 2005, IPCC special report on carbon capture and storage: Cambridge University Press,, p. 443.

6Teng, F., and Tondeur, D., 2007, Efficiency of carbon storage with leakage: physical and economical approaches: Energy, v. 32, p. 540–548.

7U.S. Energy Information Administration; International Energy Outlook, 2011.  Pg. 6

http://www.eia.gov/forecasts/ieo/pdf/0484%282011%29.pdf

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by | 17 February 2013 · 6:28 pm

Solar Panels: A True Carbon-Free Source of Energy?

“Today I challenge our nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years.”

-Al Gore, 2008

Our political leaders have a huge influence in how our population views technologies.  The former statement, while laudable, is distilled to the point of necessitating further analysis.  While the goal of ubiquitous carbon-free energy sources is certainly worth pursuing, it is vital that we do not discount the carbon footprint entailed in the adoption of those sources.

Let’s just take a look at solar photovoltaic (PV) systems. According to [1] and [2], the energy required to make a solar panel (by Siemens-like processes in 2007) was 4354 MJ/m2, which equates to 1210 kWh/m2 of panel produced. If this panel produces about 168 kWh/m2 in a year, then the estimated energy payback time (EPBT*) is about 2.2 years. This is great news.  However, if you then consider the carbon footprint of creating this solar panel and divide it over the panel’s lifetime (~30 years), the aggregate carbon emissions amount to 32 g/kWh produced. Fortunately, given improvements in technology, this value was expected to drop to 24 g/kWh by the end of 2011. So even though solar panels do not release CO2 during their normal operation (because they don’t need fuel to operate), the manufacture of solar panels does have a nontrivial carbon footprint. The upside of the story is that this footprint is still dwarfed by those of coal, oil, and natural gas (see table III below).

Image

Source: [2]

So far, I’ve spoken only of the carbon emissions from the manufacture of PV arrays.  This is only one side of the CO2 payback time equation.  Another vital consideration is the carbon that is displaced by using solar energy in lieu of dirtier energy sources from the existing energy infrastructure — namely, coal and natural gas.  To quantify this carbon offset, one must consider both the energy source that would have been used were it not for the solar panel, as well as the amount of power being displaced by the solar panel.  Furthermore, the amount of power provided by a panel is a function of both its efficiency (largely driven by technology) as well as the solar panel’s environment. For example, according to [3], it would take twice as much time for a panel in the UK than in California to offset the energy used for its production. This is due to California’s favorable sunshine conditions of about 1,700kWh/m2 per year, compared to the UK’s less favorable 700-900 KWh/m2 of solar energy per year.

So, in the end, solar power is a lot cheaper in terms of CO2 emissions and this is why I support their adoption. But it is at times appropriate to recall the famous quip from science fiction author Robert Heinlein: “there ain’t no such thing as a free lunch.”

*“EPBT is defined as the number of years a PV system must operate before it generates sufficient energy to equal the amount it consumed in manufacturing” [1]

References:

[1] P. Zhai and E.D. Williams, “Dynamic Hybrid Life Cycle Assessment of Energy and Carbon of Multicrystalline Silicon Photovoltaic Systems,” accepted for publication by Environmental Science & Technology (Sept.3, 2010).
[2] Y. Jiao, A. Salce, W. Ben, F. Jiang, X. Ji, E. Morey, and D. Lynch, “Siemens and Siemens-like Processes for Producing Photovoltaics: Energy Payback Time and Lifetime Carbon Emissions” JOM, 63 (1) (2011), pp. 28–31. Can be accessed here: http://www.springerlink.com/content/93h4wh6718251270/fulltext.pdf
[3] http://info.cat.org.uk/questions/pv/what-energy-and-carbon-payback-time-pv-panels-uk


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by | 15 April 2012 · 9:35 pm

E-readers vs. books? Which are the better option?

With the recent technological boom of e-reader devices over the last couple of years, we have all heard the question being asked: “Which is the better option? E-readers or books?” We have listened to the pro-book population speak in favor of the sentimental value, the economic feasibility, and, in some cases, the simplicity and carefree nature with which books can be handled.  There is no fear of dropping a book, getting a little sand on it, or even wrinkling a page or two.  E-reader supporters, on the other hand, advocate the convenience of being able to carry around thousands of books in a small device that is virtually weightless. With the internet, almost any e-book becomes accessible within seconds and there is no hassle in having to actually go to the store to buy a book. Consequently, both parties provide good reasons that make the choice of adopting an e-reader over a book a difficult one. However, for those of us who still cannot decide, there is an important difference between both options that makes the decision a simple one: carbon emissions.

With the paper and publishing industry together producing more than 35.2 million metric tons of carbon emissions per year (more than 9% of the carbon emissions for the manufacturing industry) and responsible for the harvesting of 125 million trees in 2008, e-readers offer a more energy-friendly alternative to books, magazines and newspapers.  According to a study carried out by Cleantech Group on the Amazon Kindle, the “carbon emitted in the lifecycle of a Kindle is fully offset after the first year of use”. In addition, the report indicated that “any additional years of use result in net carbon savings, equivalent to an average of 168 kg of CO2 per year (the emissions produced in the manufacture and distribution of 22.5 books). The Cleantech Group forecasts that e-readers purchased from 2009 to 2012 could prevent 5.3 billion kg of carbon dioxide in 2012, or 9.9 billion kg during the four-year time period.”

Overall, e-readers seem to be better option when evaluated from an energy efficiency perspective. And if the previous data wasn’t enough to convince us, there are more and more energy efficient devices hitting the market, such as LG’s solar powered e-reader. With this device, a solar panel less than a millimeter thick placed on the front of the inside cover provides enhanced battery efficiency. If exposed to the sun for 5 hours the solar panel will provide a day’s worth of charge.

All in all, it still seems like the conversion to e-readers will take some time and an actual impact on decreasing carbon emissions will depend heavily on a decreasing market demand for the amount of physical books published.  However, if the decision still lies between the sentimentality of books versus the efficiency of e-readers, we must ask ourselves, at a cost of 5.3 billion kg of carbon emissions that could be saved over three years, couldn’t we just learn to hug a teddy bear instead of a book?

Sources:

http://www.treehugger.com/files/2010/01/what-does-apples-tablet-really-mean-for-our-society.php?campaign=TH_rotator

http://cleantech.com/news/4867/cleantech-group-finds-positive-envi

http://www.eia.doe.gov/emeu/efficiency/carbon_emissions/allsic1994.html

http://www.eia.doe.gov/emeu/efficiency/carbon_emissions/paper.html

-http://www.wired.com/gadgetlab/2009/10/lgs-solar-powered-e-book-reader/#ixzz0gEFfAnV1

-http://blog.scholastic.com/ink_splot_26/2009/12/ereader-vs-books.html

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