## 2 Literature Analysis about the Life Cycle Assessment of Carbon Supply Chains
### 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. [PERSON] et al. [30] 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 Unbretto 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 \(\mathrm{kWh/ton_{CO2}}\). From the perspective of environmental benefits, carbon dioxide emission from the cement industry could be indirectly avoided by roughly one ton of CO\({}_{2\text{-eq}}/\)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. [PERSON] and [PERSON] [31] 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 [PERSON] et al. [32]: 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, [PERSON] and [PERSON] [33] 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 [PERSON] et al.