Energy and Electricity - Introduction to Carbon Capture and Sequestration - page 9

we borrow from these chapters the concern that rising CO 2 levels cause
climate change.
Let us look again at the CCS process. One may wonder whether it is
really a good idea to dig up coal, burn it, capture the resulting CO 2 and
subsequently store the CO 2 in the ground. All scientific challenges for
CCS would be solved if we were to simply leave the coal in the ground;
indeed, coal is one of nature's own efficient ways of capturing and stor-
ing carbon for millions of years. Perhaps one could capture CO 2 from the
air and use sunlight to convert it back to fuel. Alternatively, the world
could stop using fossil fuels altogether as an energy source. Implementing
these scenarios, however, requires the development of alternative energy
sources or significant new technologies.
In this context Pacala and Socolow have developed a very useful con-
cept for thinking about reducing CO 2 emissions [1.4]. Their starting point
is the business as usual scenario; if we do not take any additional action,
the increase in our energy consumption will result in a doubling of the 2006
CO 2 emissions by 2056 (see Figure 1.2.3 ). Suppose we set as a target that
over the next 50 years the increase in our energy consumption should not
increase our CO 2 emissions above 2006 levels. This target implies that we
need to have the technologies in place to avoid the emission of 7 billion
tonnes of carbon a year by 2056, compared to the business as usual sce-
nario. Pacala and Socolow argue that we need a realistic scenario to
achieve this. For example, in theory one can achieve this aim by imposing
a policy that all energy above 2006 levels can only be generated using
nuclear energy. Such a scenario, however, would require the construction
of new nuclear power plants at an unrealistic pace — one every other
month or so for the coming 50 years (see also Section 1.5). Pacala and
Socolow analyze many different scenarios and argue that it might be pos-
sible to achieve a lower target, on the order of 1 billion tonnes of avoided
carbon per year by 2056, with a single existing technology. Then, Pacala
and Socolow identify 15 technologies, each of which has the potential to
achieve 1 billion tonnes of avoided carbon per year by 2056 (see
Figure 1.2.4 ). By combining any 7 of these “wedges” one can achieve the
overall reduction target while maintaining energy growth and avoiding
economic disruption. It has now been 10 years since Pacala and Socolow
published their article; Box 1.2.1 gives an update by Davis et al. [1.5].
From our perspective it is nearly impossible to envision a scenario
that limits total carbon emission in the atmosphere without relying on
CCS (see Figure 1.2.5 ).