1. Life Cycle Assessment of Carbon Capture Utilization and Storage Supply Chains
Carbon capture utilization and storage (CCUS) supply chains not only reduce carbon dioxide emissions but also produce valuable compounds. In the literature, the life cycle assessment (LCA) of carbon capture utilization and storage supply chains is mainly regarding systems that have enhanced oil recovery in the utilization section. The environmental burden and benefits of this carbon supply chain have been reported. According to Lacy et al.
[1], the CCUS supply chain with carbon dioxide-enhanced oil recovery in Mexico has an environmental impact of 250.6 kg
CO2eq/bbl. Hertwich et al.
[2] carry out a hybrid life cycle assessment analysis for the supply chain with enhanced oil recovery in the utilization section, set in Halten (Norwegian sea). In the system, carbon dioxide from a combined cycle power plant is captured by post-combustion amine absorption, and then an emission reduction of 80% is obtained. Aspen Hysys is used for the environmental analysis evaluating the global warming and acidification impact.
Other studies about the life cycle assessment of supply chains with enhanced oil recovery in the carbon dioxide utilization section are carried out by Rhodes et al.
[3], Cooney et al.
[4], Hussain et al.
[5] Hornafius and Hornafius
[6], and Laude et al.
[7] showing the environmental advantages of this system. Among these studies, Cooney et al.
[4] develop a life cycle assessment for the carbon supply chain with enhanced oil recovery considering different system boundaries: gate to gate, cradle to gate, and cradle to grave. In the first case, impacts associated with carbon dioxide sources and the use of the produced crude oil are not considered. In the second case, natural carbon dioxide sources and transportation to the utilization sites are considered. In the last case, anthropogenic carbon dioxide sources, transportation of crude oil to the refinery, the refining step to produce gasoline, and its combustion are considered inside the boundaries. The results show that the crude recovery ratio (how much crude is recovered for a fixed amount of purchased carbon dioxide) is a critical parameter, and a reduction in emissions only for natural carbon dioxide is ensured when this parameter is increased. In Hussain et al.
[5], different sources of carbon dioxide are considered for enhanced oil recovery. The results show that all sources of carbon dioxide derived from the integrated gasification combined cycle or natural gas combined cycle plants have about 25% and 60% lower net carbon dioxide emissions per barrel of oil recovered compared to the natural carbon dioxide source. Better performances of a CCUS supply chain for oil recovery are suggested by Hornafius and Hornafius
[6], where the system could be carbon neutral or negative if the used carbon dioxide is from the fermentation emissions from an ethanol plant. However, in these studies, the life cycle assessment is not fully integrated.
Abotalib et al.
[8] develop a life cycle assessment evaluating greenhouse gas emissions for a carbon supply chain with enhanced oil recovery in the utilization site in the United Nations. Three different carbon dioxide sources are considered: ethanol, coal-fired, and natural gas-fired power plants. In this analysis, system boundaries include carbon dioxide capture and compression, carbon dioxide transportation, carbon dioxide injection (including the recovery and the transportation to a refinery), oil treatment in the refinery, and its combustion end use and displacement credit. The results show that the supply chain using carbon dioxide from ethanol plants is the best alternative that could ensure a reduction in carbon intensity up to −1.6 ton
CO2eq/bbl compared to the conventional crude recovery. Also, the authors find that the environmental analysis depends on a specific crude recovery rate. Different carbon dioxide sources are also considered in the work of Jiang et al.
[9] developing a life cycle assessment for a carbon capture utilization and storage supply chain with enhanced oil recovery. In particular, the following sources of carbon dioxide are considered: integrated gasification combined cycle, pulverized coal plants, and oxyfuel plants. The results show, respectively, the following emissions: 114.69–121.50 Mton
CO2eq, 222.95–236.19 Mton
CO2eq, and 49.09–51.96 Mton
CO2eq.
A reduction in carbon dioxide emissions in a supply chain for enhanced oil recovery is obtained in the work of Thorne et al.
[10]. Here, the carbon dioxide is captured in an oxyfuel power plant located in Poland and transported in an oil field located on the Norwegian Continental Shelf in the North Sea. The results show that the system is able to reduce 71% of emissions compared to the conventional production of oil and electricity. Environmental benefits obtained by using a CCUS supply chain for oil recovery are also suggested by Liu et al.
[11]: the net carbon dioxide emissions of producing one metric ton of crude oil are −1675.15 kg
CO2eq, suggesting how the use of this technology is important for China’s contributions to climate change. In Zhang et al.
[12], the carbon supply chain for oil recovery and carbon dioxide storage is able to reduce emissions by 50% compared to the reference system, although the framework emits 37.108 Mton
CO2eq/year. In the analysis, carbon dioxide capture and transportation stages are the major contributors, contributing to 42% and 38%. Carbon dioxide capture and transportation have the highest impact on total emissions of the supply chain also in the work of Zhang et al.
[13].
Different utilization routes are considered for carbon dioxide in the literature. In the utilization section, carbon dioxide can be used also for algae cultivation. Yue et al.
[14] develop a mathematical model to conduct an environmental analysis of the carbon supply chain with algae cultivation for biofuel production. The analyzed supply chain is set in Texas. In particular, environmental and economic analyses are developed by using a mixed integer non-linear programming model. The results show that with the system, 64% of greenhouse gas emissions can be avoided and carbon dioxide can be captured and sequestered at a cost of $45.52/ton
CO2.
A life cycle assessment for carbon capture utilization and storage supply chain in refineries producing dimethyl ether and polyol is developed by Fernandez-Dacosta et al.
[15]. Overall, a comparison with a carbon capture utilization supply chain shows that the carbon capture utilization and storage system allows a higher carbon dioxide reduction compared to conventional production.
Other products could be produced in a carbon supply chain. An interesting LCA for a CCUS supply chain in Italy and Germany was developed by Leonzio et al.
[16] with GaBi software. In the supply chain in Italy, carbon dioxide is used to be stored or to produce methane while, in the CCUS of Germany, carbon dioxide is used to produce concrete, wheat, lignin, calcium carbonate, polyurethane, methanol, and urea, or to be stored. The results show that the annual global warming potential for these supply chains in Italy and Germany are, respectively, 9.62 × 10
10 kg
CO2-eq and 1.94 × 10
11 kg
CO2-eq, which would help enable these countries to achieve the carbon dioxide reduction target fixed by European environmental policies.
Environmental advantages of a CCUS supply chain where the captured carbon dioxide is used for mineralization are found by Ostovari et al.
[17]. The system is able to avoid up to 130 Mton
CO2eq/year in Europe even with the current energy supply system. Moreover, combining the direct air capture technology and low energy emission supply, the framework can provide negative emissions at a rate of 136 Mton
CO2eq/year. However, the critical steps toward achieving the large potential of carbon dioxide mineralization in Europe are (1) scaling up the carbon dioxide mineralization technology to the industrial level and (2) exploiting large-scale mineral deposits.
An important product obtained from carbon dioxide is methanol, and a CCUS supply chain producing this compound is analyzed by Nie et al.
[18]. The results show that for each ton of carbon dioxide-derived methanol produced, the supply chain has 1.05 ton of carbon dioxide emissions and requires 1.375 ton of carbon dioxide in input. Consequently, the net emission per carbon dioxide-derived methanol produced is −0.325 ton
CO2.
From the above analysis, it is evident that the LCA of CCUS supply chains has been conducted in the literature: a benefit of this framework is reported, although the global warming potential is the main investigated impact category. Other impact categories should be analyzed in future research.
2. Life Cycle Assessment of Carbon Capture and Utilization Supply Chains
Life cycle assessment has been developed also for carbon capture and utilization supply chains, finding some environmental benefits for the produced compounds and potential hot spots.
Pan et al.
[19] carry out an environmental analysis of a carbon capture and utilization supply chain producing calcium carbonate used as a green cement material in Taiwan. In the system, basic oxygen furnace slag and alkaline cold-rolling mill wastewater, produced by the steelmaking manufacturing process, are used as the sources of calcium that is carbonated by carbon dioxide captured from flue gas, thus producing calcium carbonate. The analysis is developed by using Umberto 5.6 software including the stage of raw material extraction, capture, mineralization, transportation, and use of produced compounds. The results show that by removing 97–98% of carbon dioxide from flue gas, the energy consumption is 345 kWh/ton
CO2. From the perspective of environmental benefits, carbon dioxide emission from the cement industry could be indirectly avoided by roughly one ton of CO
2-eq/ton of slag due to the utilization of carbonated products. The results show also that the proposed supply chain can reduce not only carbon dioxide emissions but also environmental impacts on ecosystem quality, human health, and resource depletion.
Other products can be obtained from carbon dioxide. Han and Lee
[20] develop an environmental analysis for a carbon capture and utilization supply chain, where carbon dioxide is used to produce polymers and bio-butanol. The system is located in Korea and should satisfy the reduction target established for 2020. In particular, a multiple optimization problem is analyzed considering different levels: techno-economic, environmental, and technical safety. Uncertainties in input data regarding emissions, costs, and technical accidents are also considered in a stochastic model. The results show that in order to reduce environmental impact and technical loss, it is better to reduce gas monoethanolamine capture systems. The use of carbon dioxide to produce polymers is also considered by Kaiser et al.
[21]: the whole supply chain, from the carbon dioxide source to the market-ready product has a significant reduction in emissions for every considered product (i.e., high-density polyethylene, low-density polyethylene, polypropylene, polyvinylchloride, polyoxymethylene). Compared to the fossil-based production route, for polyethylene and polypropylene, a reduction of 73% is possible, while the maximum values for polyvinylchloride and polyoxymethylene are 61% and 56%.
In previous studies, only a mathematical model is developed to carry out the environmental analysis. A more detailed study should be developed. In this context, Von der Assen and Bardow
[22] conduct a life cycle assessment for a carbon capture and utilization supply chain, where carbon dioxide is used for polyol production in the polyurethane industry. Gabi software is used for this scope, in the cradle-to-gate analysis. Carbon dioxide is captured by lignite power plants. This sustainable process is compared with one producing polyols in a conventional way. In particular, in the sustainable process, it is supposed that polyol is produced at 10% wt, 20% wt, and 30% wt by carbon dioxide. Global warming impacts, fossil resource depletion, eutrophication, ionizing radiation, ozone depletion, particulate matter formation, photochemical oxidant formation, and terrestrial acidification are considered categories of impact. The results show that greenhouse gas emissions are mainly due to the production of epoxides. Also, the production of polyols at 20% wt of carbon dioxide can reduce greenhouse gas emissions by 11–19% and save fossil resources by 13–16%. A reduction is obtained for the other impact categories.
Environmental benefits for a CCU supply chain are also reported by Khoo et al.
[23], where carbon dioxide is captured from flue gas and converted into solid carbonates or sand, which can then be used for purposes such as land reclamation in Singapore. The results show that the carbon dioxide mineralization technology abates 115.78 kg
CO2-eq per ton of CO
2 in input. The results also indicate that the major sources of emissions are from the land and sea transportation of serpentine mineral feedstock, the thermal activation of the feedstock, and carbon capture processes. However, despite the use of fossil fuel-based energy for the transportation of serpentine and ammonia, and the generation of electricity consumed by the carbon dioxide mineralization processes, the technology still has a net positive carbon abatement.
In addition to these works, Cuellar-Franca and Azapagic
[24] review different utilization systems already analyzed. The life cycle assessment analysis is developed for carbon capture and utilization supply chains, where carbon dioxide is used to produce diesel from microalgae
[25][26][27][28][29][30][31][32][33], to produce dimethyl carbonate
[34] or formic acid
[35] and it is used for mineral carbonation
[19][36][37][38]. However, the authors show that global warming potential values are lower for a carbon capture and storage supply chain, characterized on average by 276 kg
CO2eq/ton
CO2 removed, even if they could have higher values for other categories of impact. This consideration about the better performance of a CCS in terms of carbon dioxide reduction is also reported in Aldaco et al.
[35]. However, compared to CCS systems, CCU has a better economic potential and lower fossil consumption.
Worse conditions for a CCU supply chain are on the other hand suggested by Passell et al.
[31]. where carbon dioxide is used to produce diesel from microalgae: the global warming potential is in fact higher compared to the conventional petroleum-based route (2.9 kg
CO2eq/1 MJ of combusted fuel compared to the petroleum diesel with 0.12 kg
CO2eq/1 MJ of combusted fuel). However, the environmental analysis is conducted considering a very low algal productivity (3 g/m
2/day), while a much higher productivity (20–30 g/m
2/day) is reported in other sources.
From the above analyses, it can be seen that CCU supply chains could reduce not only carbon dioxide emissions but could ensure the reduction in other impact categories. However, the good scale of the production plant should be considered.
3. Life Cycle Assessment of Carbon Capture and Storage Supply Chains
A first picture of the environmental analysis developed for carbon capture and storage supply chains is presented by Nie
[39], considering the power generation site, carbon dioxide capture technology/material, carbon dioxide transportation, and making some considerations about carbon dioxide storage and life cycle inventory.
It is evident that a few works consider a complete carbon supply chain, also with a carbon dioxide storage and transportation section. Some aspects that should be considered within the storage are wells, carbon dioxide storage geological formations, geological zones surrounding the carbon dioxide storage formations, and potential carbon dioxide leakages from the storage. Geographical differences of power plants have not always been considered.
In another work, Khoo and Tan
[40] (2006) develop a life cycle assessment for a carbon capture and storage supply chain, considering different capture technologies (chemical absorption, membrane separation, cryogenic, pressure swing adsorption). In addition, different storage options in ocean and geological sequestration are evaluated. SimaPro software is used to analyze the following eight environmental impact categories: global warming potential, acidification, human toxicity to air, human toxicity to water, eutrophication, ecotoxicity, wastes, and fossil fuels. The condition with a lower environmental impact is ensured by using chemical absorption as the capture technology.
A comparison of different capture technologies is also reported by Pehnt and Henkel
[41] The authors develop a life cycle assessment of the carbon capture supply chain located in Germany (Lausitz region), storing carbon dioxide in a depleted gas field. A lignite power plant is a carbon dioxide source. Post-combustion, pre-combustion, and oxyfuel capture technologies are compared and analyzed. The results show that in the carbon capture and storage supply chain with post-combustion capture technology, there is a sharp increase in all categories of impact, except for acidification. In the carbon capture and storage supply chain with pre-combustion capture technology, there is a decrease in all categories of impact. In the carbon capture and storage supply chain with oxyfuel capture, there is a near-zero emission if carbon monoxide is captured. The considered categories of impact are the following: cumulative energy demand, global warming, summer smog, eutrophication, acidification, and health impact. The environmental advantages of a CCS supply chain are reported in other works in the literature. Koornneef et al.
[42] consider a life cycle assessment for a carbon capture storage supply chain. The author considers three pulverized coal power plants with/without post-combustion capture and storage. This capture system allows a reduction in global warming potential of about 70%, but an increase in human toxicity, ozone layer depletion, and freshwater ecotoxicity is obtained. Other analyses with similar results are carried out by Corsten et al.
[43] and Gładysz and Ziebik
[44]. In Corsten et al.
[43], a CCS results in a net reduction in the global warming potential of power plants through their life cycle in the order of 65–84% (pulverized coal-fired power plant), 68–87% (integrated gasification combined cycle), 47–80% (natural gas-fired combined cycle), and 76–97% (oxyfuel). The benefits of a CCS framework in the transition to net-zero energy systems beyond emission reduction are reported by Shu et al.
[45] considering the German (as a representative highly-developed economy) energy system until 2045. Through a mathematical optimization evaluating the cost and environmental impact of the supply chain, the authors find that increasing carbon dioxide storage beyond the minimum amount significantly lowers cost and environmental impacts in up to 13 out of 16 impact categories (only resource use minerals and metals, land use, and ozone depletion increase while climate change, particulate matter, ionizing radiation, photochemical ozone formation, acidification, terrestrial eutrophication, aquatic freshwater eutrophication, aquatic marine eutrophication, human toxicity cancer effects, human toxicity noncancer effects, ecotoxicity freshwater, water scarcity, and resource use energy carriers decrease).
A first more detailed life cycle assessment for these supply chains is proposed by Petrescu et al.
[46], considering a cradle-to-grave analysis with Gabi software. Carbon dioxide is captured with different systems from a supercritical pulverized coal process, using amine, aqueous ammonia, and calcium looping. Then, the considered supply chains are compared. The system boundaries include (a) power plant feed by coal; (b) upstream processes such as extraction and processing of coal, limestone, and solvents used in capture technology, as well as power plant, coal mine, and carbon dioxide pipeline construction and commissioning; (c) downstream processes: carbon dioxide compression, transport, and storage as well as power plant, carbon capture and storage units, coal mine, and carbon dioxide pipeline decommissioning. The results show that amine technology has a lower value for global warming potential but not for all environmental categories: acidification potential, eutrophication potential, or other categories related to human toxicology are better for aqueous ammonia technology. Other impact categories such as ozone depletion potentials are better for calcium looping.
Cuellar-Franca and Azapagic
[24] (2015) propose a review of the life cycle assessment works for these kinds of systems. The results suggest that carbon dioxide emissions in a power plant can be decreased by 63–82% per unit of produced electricity. However, there is an increase in acidification and human toxicity. A reduction in global warming potential is also reported by Volkart et al.
[47]: it is 68–92% for fossil power plants and 39–78% for cement plants.
From the above analyses, it is evident that LCAs of CCS supply chains have been conducted in the literature considering different impact categories and not only the global warming potential. However, in this case, a CCS is not able to ensure a reduction in all impact categories and a trade-off should be achieved.
This entry is adapted from the peer-reviewed paper 10.3390/app14010385