Princeton University

School of Engineering & Applied Science

CO2 Capture and Storage Technologies and Strategies for Power Generation: Toward Getting the Faltering Global CCS Enterprise Back on Track

Dr. Robert H. Williams, Princeton Environmental Institute
Friend Center, 109
Tuesday, February 11, 2014 - 7:30pm

Concerned about climate change, political leaders of all major economies agreed in the Copenhagen Accord[1] to the aspirational (legally non-binding) goal of limiting the global temperature increase to 2.0°C. Realization of this goal would require reducing worldwide greenhouse gas (GHG) emissions to about ½ the present level by midcentury. Fossil fuels account for 4/5 of global energy and 2/3 of power generation.  Reaching this aspirational goal requires limited CO2 emissions to ~ ¼ of the CO2 that would result from combustion of remaining fossil fuel reserves.  Aggressive pursuit of CO2 capture and storage (CCS) for fossil energy conversion systems would enable using much more of these fossil fuel reserves.
The three approaches to CCS (post-combustion capture, pre-combustion capture in conjunction with coal gasification, and oxy-combustion capture) are described in the context of coal and natural gas power generation from both technological and economic aspects when captured CO2 is stored in deep saline formations.
An ambitious “roadmap” for CCS was created in 2009 by the International Energy Agency for launching CCS technologies in power markets in support of the goal of limiting the global temperature increase to 2.0°C. What has been accomplished to date is described—far less than what was called for in the 2009 roadmap. The reasons for the slow progress are both economic and political. “Early-mover” CCS projects are turning to be much more costly than had been anticipated and are difficult to finance.
A strategy for getting the global CCS enterprise back on track is discussed. This strategy involves: (a) shifting the focus to gasification plants that make simultaneously synthetic liquid transportation fuels and electricity from coal, and (b) selling captured CO2 for enhanced oil recovery. Such plants offer much better economic prospects than plants that make only electricity both because: (a) CO2 capture costs are inherently much lower for plants that make synthetic fuels from coal via gasification than for power plants, and (b) the revenue streams from selling the transportation fuel and CO2 coproducts facilitate paying off the huge capital investments for these plants.
But for such systems deep reductions in GHG emissions are not possible because the carbon from coal that ends up in the synthetic fuels enters the atmosphere as CO2 when the synthetic transportation fuels are burned.  This challenge can be addressed by coprocessing lignocellulosic (non-food) biomass grown on a sustainable basis with coal. In these systems ½ to ⅔ of the carbon in the biomass and coal is captured as CO2 for underground storage. For these systems the negative CO2 emissions associated with photosynthetic CO2 storage offset the positive CO2 emissions that arise from coal-derived carbon in the synthetic fuels when these fuels are burned.  Such systems enable realization of deep reductions in GHG emissions with relatively modest biomass fractions and offer the prospect of attractive economics under relatively modest carbon mitigation policies.  The needed technologies are proven technically and are ready to be demonstrated at commercial scale.
The lecture concludes with a discussion for strategies for financing costly early mover projects so as to facilitate cost reduction via experience (learning by doing).

[1] Adopted in 2009 at the 15th Meeting of the Conference of Parties (COP 15) to the United Nations
Framework Convention on Climate Change.