For certain industrial processes such as ammonia production, the CO2 emitted is very pure and capture requires only small additional efforts (IEA 2011 and UNIDO 2011). Therefore, these processes yield relatively cheap CO2 as an output. These high-concentration sources represent only approx. 2 % of the 12.7 Gt capturable point source emissions (see Fig. 1). Today, capture of CO2 is an established process predominantly in hydrogen, ammonia, and natural gas purification plants as they allow for comparatively cost efficient CO2 separation (Wilcox 2012). While raw natural gas can contain CO2 in different concentrations depending on the respective source, the processing of the gas to achieve pipeline quality often includes carbon dioxide separation (Baker and Lokhandwala 2008).
Chemical Engineering Plant Cost Index 2013 Pdf
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Large industrial CO2 emitting processes together currently make up for approx. 22 % of the 12.7 Gt capturable emissions from point sources (see Fig. 1). They include the production of industrial materials such as iron and steel, cement, aluminum as well as refineries. As these processes emit CO2 in different quantities and qualities, CO2 capture at such plants is also connected to varying efficiency penalties and benchmark costs. Moreover, a large number of other industrial manufacturing plants are potential candidates for CO2 capture. Often, they are comparatively smaller than power plants (Bennaceur et al. 2008; Faulstich et al. 2009; Weikl and Schmidt 2010). Thus, economies of scale can be more difficult to achieve. For example, waste incineration so far has barely been analyzed in regard to CO2 capture although reusing such CO2 would conceptually close resource cycles. The comparatively small size of the incinerators however entails higher capture costs per tonne than those of other CO2 sources (Faulstich et al. 2009).
Since the expected near-term status of CO2 utilization does not involve large volumes of CO2 smaller regional solutions gain importance. When new plants are set up that reuse CO2 emissions these can be planned next to a convenient source of CO2 at sufficient quality and a competitive cost. Emissions from fossil-fired power plants are not required to meet the potential CO2 utilization demand. Even large-scale visions for CCU can therefore not serve as an argument to prolong fossil-fired power generation. When implementing large-scale CO2 utilization scenarios involving synthetic fuels based on power-to-liquid or -gas technologies a broader infrastructure especially for renewable energy but also for CO2 supply will be needed. Until then, from a mitigation perspective, differentiating recovered CO2 by source can even be misleading as in sum it does not play a role to the environment where the reused CO2 comes from. Instead, market mechanisms will balance supply and demand. Nevertheless, sustainability aspects always need to be considered when further deploying CCU technologies for example by conducting lifecycle analysis and considering alternative technologies based on renewable energy and raw materials.
Since the utilized CO2 in most cases is reemitted at a later point in time a simple aggregation of the used volumes of CO2 is not an indicator of ecologic performance (von der Assen et al. 2013). Instead, a detailed environmental analysis is necessary to calculate the real carbon footprint of a certain CCU technology compared to a conventional technology (von der Assen et al. 2015). Indeed, the same principle applies to the business case of CO2 utilization. In some cases, using comparatively cheap CO2 as a feedstock and replacing more costly and volatile priced fossil-based raw materials can lead to a cost reduction which sets the business case for CCU. However, for those production processes that use CO2 still inefficiently or are not competitive to conventional fossil-based production, there is no business case until further research and development or political incentives prove otherwise. While CO2 can generally be used in many processes, this paper focuses on potential commodity CO2 from industrial capture and does not include biological fixation and conversion via the cultivation of crops or algae for example for making biofuels.
The potential sources of waste CO2 emissions are numerous. Industrial plants emit CO2 in different quantities and at diverse qualities. Several capture technologies can be applied, for example adsorption, absorption, cryogenic separation, or membranes (de Coninck and Benson 2014). The costs of capturing CO2 at a certain source depend on the technological efforts that must be undertaken to collect the CO2 in the required quality from the industrial exhaust gas. Thus, the costs are largely influenced by the concentration of CO2 in the exhaust gas. Moreover, the CO2 needs to be purified and any toxic or hazardous chemicals removed (Aresta and Dibenedetto 2010). Furthermore, a larger plant size can lower the investment and operating costs per captured tonne of CO2 through economies of scale (Faulstich et al. 2009; Möllersten et al. 2003). Consequently, despite technical feasibility, not all emitting sources represent economically viable options at current conditions.
Today, CO2 capture is technologically feasible and industrial practice on a small scale around the world. However, due to a lack of incentives, large-scale capture is currently not economically viable. Hence, the costs of capture are essential when considering potential sources and technologies for recovering CO2 emissions. Capture costs are generally defined as the costs of CO2 separation and compression at a single facility (e.g., an industrial plant), disregarding any costs of transport, storage, or further conversion steps (Metz et al. 2005). They are usually derived from comparing a system with CO2 capture to a reference system without capture. In the literature, two main measures for CO2 capture costs exist: costs of capture and costs of avoidance of CO2. According to the IPCC (Metz et al. 2005), the two measures are clearly defined as follows:
In a cross-technology comparison, meeting these standards is often not possible. Especially, when emerging technologies and future scenarios are evaluated, reliable and consistent data can be scarce. Instead, a more heuristic approach must be adopted and the best available data analyzed. Thus, this paper summarizes the recent techno-economic literature on carbon capture in order to establish a large-scale picture of CO2 supply in the near-term. A secondary database for the largest industrial CO2 emitting sources is established in Table 2 that gathers the most recent and reliable cost data available. The presented measures and assumptions are heterogeneous and the data should be considered as estimates and benchmark values for best practice processes. To maximize cost data quality, recent peer-reviewed as well as broader government studies were preferably selected. Other studies were included to fill data gaps. The origin and relative assumptions of the capture cost studies are detailed in Table 2 as far as they were disclosed. Since capture from coal- and natural gas-fired power plants has been discussed the most extensively in the literature, the summarized average costs from the IEA study seem a reliable data source. Moreover, the capture costs for the higher concentrated sources of ammonia, hydrogen, and natural gas as well as cement production derived from the annually updated assumptions of US Energy Information Agency (EIA) seem a reliable data source for the purpose of analysis even though the data regionally cover only the USA. For the other potential sources of CO2, less research has been performed and average cost data are not available. Thus, recent peer-reviewed techno-economic studies have been included for capture from iron and steel, refineries, bioenergy, fermentation, and aluminum production. For capture from ethylene production a non-governmental, non-peer reviewed data source was included.
CO2 can either be used directly or as feedstock for a variety of products. Overall, approx. 222 Mt of the commodity are used in industrial applications worldwide (see current est. volumes in Table 3). Firstly, direct utilization of liquid or gaseous carbon dioxide usually requires a very high purity especially in the food and beverage industry which currently consumes approx. 11 Mt CO2 per year. Furthermore, around 6 Mt CO2 are used as process gas in various industrial applications (IHS 2013). The largest direct use of 25 Mt of CO2 can be found in EOR/EGR which represent a borderline case, as they combine a utilization and storage function (Global CCS Institute 2014). Largely, they are attributed to CCS rather than CCU since after the extraction of additional fuels through CO2, the CO2 can potentially be stored permanently in the depleted oil and gas fields. As EOR/EGR is a potential market for recovered CO2, it needs to be included when analyzing market volumes of CO2 (see Table 3). Secondly, the conversion of CO2 to materials still is limited to few applications at a smaller scale, except for urea synthesis which globally currently consumes approx. 130 Mt CO2 per year. Indeed, urea and ammonia production are often combined, so that an estimated half of the high purity CO2 from ammonia production is used for urea synthesis while the rest is often vented (IEA 2013; Metz et al. 2005). Apart from that, a marginal amount of CO2 is used for the production of several specialty chemicals, e.g., of salicylic acid used for making aspirin pills. Commercial plants producing CO2-based fuels currently can be found only at demonstration scale of several thousand tonnes, e.g., by the companies Carbon Recycling International (CRI) in Iceland and Audi and Sunfire in Germany (CRI 2016; Strohbach 2013; Sunfire 2014). As R&D on CCU technologies continues and some important breakthroughs have been observed further CO2-based products are expected to enter global markets soon as depicted in the near-term (up to 10 years) estimates in Table 3. Thus, the demand for CO2 as a commodity might increase in the future. 2ff7e9595c
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