Sweeping Carbon Dioxide Under The Carpet  

WorldChanging has an interesting post up on carbon dioxide sequestration. I think its fair to say these schemes are not going to be a solution to global warming.

"Carbon Sequestration" is sometimes suggested as a parallel process alongside a significant shift away from carbon-producing technologies. The logic is straightforward: carbon dioxide is still produced, but rather than remaining concentrated in the atmosphere for a century, it is extracted. This extraction can take place at the point of production (so-called "carbon capture") or more generally, using CO2-loving plants. Although some may hope to use carbon sequestration as an excuse to delay or ignore a move towards non-carbon-emitting technologies, the reality is that the planet is close enough now to a potential climate tipping point that we should not rule out any effort that might help us forestall disaster. Moreover, as much as we would like to see all manner of CO2-producing industries (such as power production or cement manufacturing) move to cleaner technologies, even in the best likely scenario it's going to take decades for the transition to be complete. In principle, if CO2 output can be reduced from those industries during the transition, we're all better off.

But the IPCC (Intergovernmental Panel on Climate Change) wondered just what kind of effort would be required to make a real difference in CO2 output. The IPCC commissioned a study, and the preliminary results are now in. Read on for a discussion of our sequestration options.

The summary report runs a brief 25 pages, and it makes for sobering reading. Under best case scenarios, carbon capture and storage wouldn't make a significant difference in CO2 levels until the mid-point of this century; in addition, the current available sequestration options all pose significant challenges, including the possibility of actually exacerbating the global environmental situation rather than ameliorating it. That said, under some scenarios the addition of carbon capture and storage to the overall mitigation mix could reduce the overall costs of reducing greenhouse emissions by as much as 30%.

It's notable, however, that the greatest reduction of CO2 output from fossil-fuel-based power plants comes from new systems built with scrubbing and capture technologies built-in, perhaps as much as a 80-90% reduction in emissions. Bolt-on retrofits provide "significantly reduced overall efficiencies" of CO2 reduction. How the costs of new CCS-equipped power plants compare to the costs of carbon-free renewable systems appears to be outside the scope of this document, but stands as a key research question; moreover, it will be important to project the degree to which those costs will decline over time.

The other big question is just where the captured and compressed CO2 will be stored. Several options are presented in the report: deep storage in saline formations and depleted oil and gas fields (with deep injection in order to increase oil production or coal bed methane recovery as a variant); deep water "dissolution" and sea floor dispersal; and locked up in metal oxides (such as serpentine). Leaving aside the irony of using industrial CO2 output as a means of increasing carbon-based fuel production, each of these options has serious drawbacks...

Jim at The Energy Blog also has a couple of excellent posts up on "clean coal", carbon sequestration and IGCC (Integrated gasification combined cycle) power plants. I remain very skeptical about sequestration schemes in particular, but I would concede that building new IGCC plants is better than building new convential coal fired plants (but nowhere near as good as putting a lot more investment into wind, solar and tidal distributed generation) - especially if they are replacing existing coal fired stations.

The following are the characteristics of an IGCC plant:

* SOx, NOx and particulate emissions are much lower in IGCC plants than from a modern coal plant. Its VOC emissions and mercury emissions are comparable.
* IGCC plants emit approximately 20% less CO2 emissions than a modern coal plant.
* IGCC plants use 20-40% less water than a modern coal plant.
* IGCC plants operate at higher efficiencies than conventional coal fired power plants thus requiring less fuel and producing less emissions. Current efficiency is 42% with efficiencies as high as 60% expected in the very near future using a high efficiency turbines and some other process improvements.
* Costs for electricity, without CO2 capture, is about 20% higher than in a modern coal plant. Electricity costs are 40% lower than from a natural gas IGCC plant with natural gas at $6.50 per MMbtu.
* CO2 can be captured from an IGCC plant much more easily that from a conventional coal plant at an an additional cost increase of 25-30% for capture and sequestration, without transportation charges.
* IGCC offers the possibility to capture the hydrogen that is part of the syngas stream, in an economic manner.

Elsewhere on WorldChanging they have an item on a new design for capturing tidal energy - the "Manchester Bobber".

Power generation based on the "motion of the ocean" offers significant long-term value, and arguably could eventually displace solar and wind generation for large-scale renewable energy projects. Hydrokinetic power (encompassing wave, current and tidal power) doesn't have the "intermittency" problems facing solar and wind, nor are there as many issues about ruined views and overrun landscape. Costs remain high, however. There are numerous ocean power projects in testing, and while most show promise, I don't believe we've yet seen the real breakout project putting ocean power at the front of the renewable energy race. The latest contender is the "Manchester Bobber," an ocean power platform design from the University of Manchester.

Some other gems on WorldChanging today is Alan Atkisson's touching story about a woodpecker and the cold war tale of Stanislav Petrov.