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PESD releases new working paper on potential for CCS technology to capture greenhouse gases in electricity sector

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Focusing on capture systems for coal-fired power plants until 2030, a sensitivity analysis of key CCS parameters is performed to gain insight into the role that CCS can play in future mitigation scenarios and to explore implications of large-scale CCS deployment.
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Role of Carbon Capture Technologies in Greenhouse Gas Emissions Reduction Models: A Parametric Study for the U.S. Power Sector

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This paper analyzes the potential contribution of carbon capture and storage (CCS) technologies to greenhouse gas emissions reductions in the U.S. electricity sector.  Focusing on capture systems for coal-fired power plants until 2030, a sensitivity analysis of key CCS parameters is performed to gain insight into the role that CCS can play in future mitigation scenarios and to explore implications of large-scale CCS deployment.  By integrating important parameters for CCS technologies into a carbon-abatement model similar to the EPRI Prism analysis (EPRI, 2007), this study concludes that the start time and rate of technology diffusion are important in determining the emissions reduction potential and fuel consumption for CCS technologies. 

Comparisons with legislative emissions targets illustrate that CCS alone is very unlikely to meet reduction targets for the electric-power sector, even under aggressive deployment scenarios.  A portfolio of supply and demand side strategies will be needed to reach emissions objectives, especially in the near term.  Furthermore, the breakdown of capture technologies (i.e., pre-combustion, post-combustion, and oxy-fuel units) and the level of CCS retrofits at pulverized coal plants also have large effects on the extent of greenhouse gas emissions reductions.

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Program on Energy and Sustainable Development, Working Paper #85
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Varun Rai
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Bioelectricity promises more 'miles per acre' than ethanol, Science study finds

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[See video interview with Chris Field and David Lobell here].

Biofuels such as ethanol offer an alternative to petroleum for powering our cars, but growing energy crops to produce them can compete with food crops for farmland, and clearing forests to expand farmland will aggravate the climate change problem. How can we maximize our "miles per acre" from biomass?

Researchers writing in the May 7, 2009, edition of the journal Science say the best bet is to convert the biomass to electricity rather than ethanol. They calculate that, compared to ethanol used for internal combustion engines, bioelectricity used for battery-powered vehicles would deliver an average of 80 percent more miles of transportation per acre of crops, while also providing double the greenhouse gas offsets to mitigate climate change.
 
"It's a relatively obvious question once you ask it, but nobody had really asked it before," said study co-author Christopher B. Field, director of the Department of Global Ecology at the Carnegie Institution. "The kinds of motivations that have driven people to think about developing ethanol as a vehicle fuel have been somewhat different from those that have been motivating people to think about battery electric vehicles, but the overlap is in the area of maximizing efficiency and minimizing adverse impacts on climate."
 
Field, who is also a professor of biology at Stanford University and a senior fellow at Stanford's Woods Institute for the Environment, is part of a research team that includes lead author Elliott Campbell of the University of California-Merced and David Lobell of Stanford's Program on Food Security and the Environment.

Bioelectricity vs. ethanol

The researchers performed a life-cycle analysis of both bioelectricity and ethanol technologies, taking into account not only the energy produced by each technology, but also the energy consumed in producing the vehicles and fuels. For the analysis, they used publicly available data on vehicle efficiencies from the U.S. Environmental Protection Agency and other organizations.
 
Bioelectricity was the clear winner in the transportation-miles-per-acre comparison, regardless of whether the energy was produced from corn or from switchgrass, a cellulose-based energy crop. For example, a small SUV powered by bioelectricity could travel nearly 14,000 highway miles on the net energy produced from an acre of switchgrass, while a comparable internal combustion vehicle could only travel about 9,000 miles on the highway. (Average mileage for both city and highway driving would be 15,000 miles for a biolelectric SUV and 8,000 miles for an internal combustion vehicle.)
 
"The internal combustion engine just isn't very efficient, especially when compared to electric vehicles," said Campbell. "Even the best ethanol-producing technologies with hybrid vehicles aren't enough to overcome this."

Climate change 

The researchers found that bioelectricity and ethanol also differed in their potential impact on climate change. "Some approaches to bioenergy can make climate change worse, but other limited approaches can help fight climate change," said Campbell.  "For these beneficial approaches, we could do more to fight climate change by making electricity than making ethanol."
 
The energy from an acre of switchgrass used to power an electric vehicle would prevent or offset the release of up to 10 tons of CO2 per acre, relative to a similar-sized gasoline-powered car.  Across vehicle types and different crops, this offset averages more than 100 percent larger for the bioelectricity than for the ethanol pathway. Bioelectricity also offers more possibilities for reducing greenhouse gas emissions through measures such as carbon capture and sequestration, which could be implemented at biomass power stations but not individual internal combustion vehicles.
 
While the results of the study clearly favor bioelectricity over ethanol, the researchers caution that the issues facing society in choosing an energy strategy are complex. "We found that converting biomass to electricity rather than ethanol makes the most sense for two policy-relevant issues: transportation and climate," said Lobell. "But we also need to compare these options for other issues like water consumption, air pollution, and economic costs."
 
"There is a big strategic decision our country and others are making: whether to encourage development of vehicles that run on ethanol or electricity," said Campbell. "Studies like ours could be used to ensure that the alternative energy pathways we chose will provide the most transportation energy and the least climate change impacts."
 
This research was funded through a grant from the Stanford Global Climate and Energy Project, with additional support from the Stanford Program on Food Security and the Environment, UC-Merced, the Carnegie Institution for Science, and a NASA New Investigator Grant.

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Carbon Capture and Storage: An Assessment of Required Technological Growth Rates and Capital Investments

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In this new working paper PESD research affiliate Danny Cullenward studies the required rates of growth and capital investments needed to meet various long-term projections for CCS. Using the PESD Carbon Storage Database as a baseline, this paper creates four empirically-grounded scenarios about the development of the CCS industry to 2020. These possible starting points (the scenarios) are then used to calculate the sustained growth needed to meet CO2 storage estimates reported by the IPCC over the course of this century (out to 2100).

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Program on Energy and Sustainable Development, Working Paper #84
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Hubbert's Peak, The Coal Question, and Climate Change

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Abstract
An accurate estimate of the ultimate production of oil, gas, and coal would be helpful for the ongoing policy discussion on alternatives to fossil fuels and climate change. By ultimate production, we mean total production, past and future. It takes a long time to develop energy infrastructure, and this means it matters whether we have burned 20% of our oil, gas, and coal, or 40%. In modeling climate change, the carbon dioxide from burning fossil fuels is the most important factor. The time frame for the climate response is much longer than the time frame for burning fossil fuels, and this means that the total amount burned is more important than the burn rate. Oil, gas, and coal ultimates are traditionally estimated by government geological surveys from measurements of oil and gas reservoirs and coal seams, together with an allowance for future discoveries of oil and gas. We will see that where these estimates can be tested, they tend to be too high, and that more accurate estimates can be made by curve fits to the production history.

Bio
Professor Rutledge is the Tomiyasu Professor of Electrical Engineering at Caltech, and a former Chair of the Division of Engineering and Applied Science there.  He is the author of the textbook Electronics of Radio, published by Cambridge University Press, and the popular microwave computer-aided-design software package Puff.  He is a Fellow of the IEEE, a winner of the IEEE Microwave Prize, and a winner of the Teaching Award of the Associated Students at Caltech.  He served as the editor for the Transactions on Microwave Theory and Techniques, and is a founder of the Wavestream Corporation, a manufacturer of high-power transmitters for satellite uplinks.

This talk is part of the PESD Energy Working Group series.

Richard and Rhoda Goldman Conference Room

Dave Rutledge Professor of Electrical Engineering Speaker Caltech
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