## 2 Literature Analysis about the Life Cycle Assessment of Carbon Supply Chains
### Life Cycle Assessment of Carbon Capture Utilization and Storage Supply Chains  
CCUS supply chains not only reduce carbon dioxide emissions but also produce valuable compounds. In the literature, the 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 [PERSON] et al. [12], the CCUS supply chain with carbon dioxide-enhanced oil recovery in Mexico has an environmental impact of 250.6 kg\({}_{\text{CO2 eq}}\)/bbl. [PERSON] et al. [13] 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 [PERSON] et al. [14], [PERSON] et al. [15], [PERSON] et al. [16] [PERSON] and [PERSON] [17], and [PERSON] et al. [18] showing the environmental advantages of this system. Among these studies, [PERSON] et al. [15] 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 [PERSON] et al. [16], 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 [PERSON] and [PERSON] [17], 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. [PERSON] et al. [19] 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\({}_{\text{CO2 eq}}\)/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 [PERSON] et al.