Carbon Capture and Storage
Sustainability Aspects of Carbon Capture and Storage - An Approach to a holistic CCS Assessment
Around 80 % of the world’s energy mix are currently covered by the use of oil, natural gas and coal (hard coal and lignite). More than 50 % of the global annual anthropogenic greenhouse gas (GHG) emissions are induced as CO2 by the use of fossil fuels. The energy supply sector provides more than 25 % of the total GHG emissions. Hard coal and lignite cover about half of the German electrical power consumption. The German coal industry currently emits an annual total of about 300 mill. t/a of CO2, which is more than 30 % of the total German CO2 emissions. German coal fired power plants offer huge potentials for CO2 emission reduction by CCS due to their high emissions and their structure as large point sources.
Carbon Capture and Storage is expected to become one of the main technological instruments for mid-term reduction of CO2 emissions into the earth’s atmosphere. CCS technology bases on capturing CO2 from large point sources, such as power plant or industrial processes flue streams, and permanently storing it away from the earth’s atmosphere. The German energy supply sector offers huge potentials for CCS.
The CCS technology chain basically consists of three process steps: capture, transport, and storage. Concerning the process of CO2 capture from flue gas streams, three main technologies are available and currently being investigated: post-combustion, pre-combustion, and oxy-fuel combustion. They all differ regarding their implementation into the power generation process chain, their process conduct and their costs and efficiency. If the prospected storage option is not very near the emission source, the CO2 has to be transported to the storage location after the capture process. Transport in pipelines is considered to be the cheapest and most feasible form of transport. Various options for the long-time storage of CO2 are being discussed. The storage of CO2 in underground geological formations is currently regarded to be the most feasible alternative for long-term CO2 storage. The basic prerequisite for geological CO2 storage is the existence of permeable formations at appropriate depths overlain by impermeable cap rock formations that will permanently prevent leakage.
The Concept of Sustainable Development
The concept of ’sustainable development‘ introduced by the WCED has become a model for western-oriented development and environmental policy. Implementing this concept of SD into applicable standards has spawned a variety of approaches for applying manageable methods for assessing sustainable development. Many methods apply a conceptual division of the field of SD into three constituent parts, also known as dimensions of ‚pillars‘: environmental sustainability, economic sustainability and social sustainability.
It can be regarded as a generally acknowledged fact, that power generation from fossil fuels at today’s development state of power generation technologies is a vital and essential component of current society’s existence, as large parts of today’s economic system and standard of living rely on stable and high-level power supply. Thus, in order to be consistent with the demand for SD, the energy industry has to adapt the principles of SD in the way that power generation operations and adjacent processes have to be ecologically justifiable, economically feasible and socially acceptable.
In the context of the interdisciplinary and multilateral research initiative COURAGE (CO2 Underground Storage in Western Germany on behalf of RWE Power AG), basic structures for a sustainability assessment methodology of CCS have been developed.
Integration of CCS into the process chain of energy generation from lignite would have: ecologic effects, e.g. higher demand for combustible fuel, faster depletion of reserves, risks of leakage (transport, storage), and higher land and water use (caused by higher lignite production); economic effects, e.g. additional costs for capture and storage processes, lower system efficiency in power plants due to high energy requirements of CO2 capture, and; social effects, e.g. the provision of jobs along the CCS technology chain.
The BBK I developed a methodology for a holistic CCS sustainability assessment based on the MADM (multiple criteria decision making) method AHP (analytical hierarchy process). MADM assessment methods apply computerized algorithms to calculate the most favorable solution to a given problem. The methodology allows the assessment of the technology option CCS against the background of the sustainability discussion in a manageable and implementable system.