To achieve the national and global climate protection objectives, a full decarbonisation of all sectors in the energy system will be necessary in the long term until the turn of the century. While the transformation towards renewable energy sources is already well advanced in the electricity sector, approaches of extensive decarbonisation exist only isolated. This is despite the fact that the energy efficiency potential of the energy intensive industry has already been largely exhausted for economic considerations and compared to other sectors disproportionate savings have been achieved.
Today the CO2 utilisation is discussed as one of the future low-carbon technologies. CO2 is separated from the flue gas stream of power plants and is prepared for further processing as raw material. Fossil resources will not only be used as fuel in the industrial sector but also as feedstock for production of different products (e.g. urea, fertilizer, polymer materials). CO2 containing gas streams from industrial processes exhibit a higher concentration of CO2 than, for instance, flue gases from power plants which contain for example a high percentage of nitrogen. On the one hand it is therefore obvious to use industrial CO2 sources as raw material for the chemical industry and for the synthesis of fuel on the output side. On the other hand, fossil resources can be replaced by substitutes of reused CO2 on the input side. If set up in the right way, this step into a CO2-based circular flow economy could make a contribution to the decarbonisation of the industrial sector and according to the adjusted potential, even rudimentarily to the energy sector.
In this study the potential CO2 sources, the potential demand and the range of applications of CO2 are analysed by the case study of North Rhine-Westphalia (NRW). Since activation energy is needed for the reuse of CO2 and the utilisation usually depends on the use of hydrogen as a source of energy, it is necessary to view also regional sources and usage possibilities of hydrogen. NRW with its high density of (energy-intensive) industry is well suited for this analysis.
At first, chapter one analyses the CO2 sources which are expected to be available in the middle-term (time frame until 2030) under the conditions of a stringent climate protection policy. Therefore, industrial point sources of the chemical industry, the iron and steel industry, the cement and lime industry, coking plants and refineries are considered as well as CO2 sources of large combined heat and power plants (hard coal and natural gas), waste incineration plants and biomethane plants. The potential CO2 streams are scrutinised quantitative (CO2 amount), qualitative (CO2 concentration) and on their regional distribution. Analogue industrial hydrogen sources are regarded concerning their available amount and their regional distribution.
Chapter two considers current and potential utilisation options of CO2 and H2. Thereby, the utilisation as a chemical raw material is discussed as well as the synthesis to gaseous (Power-to-Gas) and liquid fuels (Power-to-Fuels). Furthermore, an overview about current projects and research activities is shown.
In Chapter three the identified potentials of CO2 and H2 sources of chapter one are linked to the potential utilisation options (sinks) of chapter two. The concrete spectrum of theoretical potentials of reusing CO2 in NRW is estimated regarding a discussion about the preconditions and limits of appropriate paths of exploitation of CO2. Therefore, location issues are of crucial importance as they influence the decision of the media (flue gas, separated CO2, H2, electricity, methane, raw materials, …) which has to be carried.
To contribute to a sustainable development, CO2 value chains have to be not only technically stable, but also ecologically, economically and socially. Chapter four develops the methodological background for a systematic multi-criteria-analysis (MCA) of potential value chains of CO2 reusing. Therefore, a general overview of different approaches for an integrated sustainability assessment of technologies and processes is given. Potential criteria which can be suitable for the evaluation of CO2 value chains are identified and exemplarily explained.
Experiences of new technologies show that their successful implementation also depends on the acceptance of involved actors and the general public. Chapter five presents the results of an own qualitative survey based on freely available German and English documents, studies and publications with the subjects of awareness and acceptance of CO2 usage. Moreover specific articles, statements, party programs as well as strategy and conference papers are analysed in order to examine attitudes of political decision makers and chosen social actors (e.g. journalists). Based on this analysis, communication lacks are identified and appropriate methods and tools for a successful communication about CO2 utilisation are proposed.
The final chapter six derives recommendations for a appropriate future designing of CO2 utilisation options out of the results of the previous chapters. The requirements of projects about research and development as well as demonstration are specified. Necessary political and economical aspects about the development of technologies as well as important holistic issues about the ecological tolerance and system integration are identified.