More on carbon capture and storage

In a lecture at UC, Berkeley, a spokeswoman from the UK showed graphs of either the UK or EU in 2050. Most of the electricity was from coal and natural gas with carbon capture and storage. The audience seemed to feel the proposal overdid it on CCS, but that it would be part of our future.

There may be several reasons to use CCS along with nuclear power. According to Carbon Capture And Its Storage: An Integrated Assessment by Simon Shackley and Clair Gough, the UK is building a demonstration project, collecting CO2 from a natural gas plant and injecting it into North Sea oil fields to increase the recovery. Indeed, the first use of CCS is for this purpose; timing is important because delay would lead to shutting down the wells and then making CO2 available.

Enhanced oil recovery
Enhanced oil recovery

EOR produces more oil and more CO2. On the other hand, the more North Sea oil we use, the less tar shale we need. If the study confirms cost estimates and feasibility, this technology will be used to increase oil recovery elsewhere.

Nuclear power is the main competitor in the UK and elsewhere to reducing GHG emissions from electricity with CCS and either coal or natural gas.

How do the sources compare?

The company E.ON UK plc provided the following cost estimates for different generation options [today 1 British pound = $2].
Coal using CCS: 3.9 – 5.1 p/kWh
Nuclear: 2.5 – 4.0 p/kWh
Onshore wind: 4.2 – 5.2 p/kWh
Offshore wind: 6.2 – 8.4 p/kWh

Clearly wind and solar are not important energy resources in the UK.

Why might CCS be the better choice (sometimes)?
1. Construction and planning timescale: It should be possible to construct and operate a fossil fuel CCS in 4 to 6 years from the decision to proceed. This appears to be faster than nuclear though no one has built either a CCS plant or a modern nuclear plant. [Estimates of nuclear plant construction times come in at below 4 years to 6 years, eg, The Future of Nuclear Power.]

2. Modularity: with either coal or nuclear, the plant needs to be large for economy of scale. If gas is used, modular units of 350 MW can be used.

3. Capital costs: Transportation and storage costs will be substantial. These might decrease when 10 Mt/y CO2 are piped through the system, but this is more than one source would produce (a 1 GW coal plant produces 5 – 6 Mt/y).

Fossil CCS therefore demonstrates some of the limitations of nuclear with respect to ‘lumpiness’ [of investment] and inflexibility, but probably to a lesser extent than nuclear.

4. Fossil CCS plants may be cheaper than nuclear, if nuclear comes in at the high estimate and CCS at the low. [Plants with CCS don’t capture 10% or more of the CO2 emitted, and they need more energy and produce more CO2, so plants are expected to reduce GHG emissions only by 80-90%. That will increase the price of CCS plants if, as expected, GHG cap and trade or/and tax policies are implemented soon.]

5. It isn’t nuclear. Many in the UK public prefer “not nuclear” plants. Members of Parliament perceive opposition to nuclear power as greater than it actually is.

On the other hand, relying on natural gas as a fuel, an energy source where costs are volatile and an important part of the cost, is risky for society. [Uranium costs don’t have much effect on the cost of nuclear power.]

Other reasons I’ve heard:
• Put the energy eggs in as many baskets as possible.
• Anyone operating a relatively modern coal power plant a decade from now will be able to retrofit it for CCS. This will cost utilities dearly, but may be cheaper than dismantling a relatively new power plant.
• Biopower (using plants to make electricity) releases (ideally) just a little more CO2 than it absorbed from the atmosphere (more because you don’t walk it from the field to the plant). With CCS, most of the CO2 absorbed from the atmosphere would be stored, making biopwer potentially GHG negative.

According to Shackley and Hough, several questions still have to be answered about CCS viability:

• Is CCS viable from a geological perspective? Is there a strong and solid case for safe and secure long-term storage?

• What is the capacity for CO2 storage? It is important to narrow estimates for the ability of aquifer pores to store supercritical CO2 (temperature and pressure are above thermodynamic critical point), now ranging from 0 – 100%.

• What are the risks and potential impacts of leakage?

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