## 4 How Should We Treat the Multifunctionality of a Carbon Supply Chain in the LCA? Before starting a life cycle assessment for a carbon supply chain, it is recommended to have in mind some important considerations where, generally, the aim of this analysis is to find the contribution of different single processes to the overall environmental impact (finding hot spot points with a higher impact); in the case of different products, it is possible to find the route or product process with the lowest environmental impact, compare \begin{table}
\begin{tabular}{c c} \hline
**Methodology** & **Impact Category** \\ \hline MEEup & Energy consumption, water consumption, materials in use, waste and to incinerator), hazardous waste generation, emissions to air \\ \hline BEES & Global warming, acidification, eutrophication, fossil fuel depletion, indoor air quality, habitat alteration, water intake, criteria air pollutants, smog, ecotoxicity, ozone depletion, and human health \\ \hline Ecological footprint & Five types of direct land occupation are considered: cropland, pasture, forest, built-up area, and hydropower area, and two indirect land occupations: fossil fuels and nuclear energy \\ \hline USEtox & Ecotoxicity \\ \hline EDP & Land occupation, land transformation, and biodiversity \\ \hline IPCC & Climate change \\ \hline CED & Fossil resources, such as hard coal, lignite, peat, natural gas, and crude oil, and for nuclear and other renewable resources as well such as biomass, water, wind, and solar energy \\ \hline CExD & Fossil resources, such as hard coal, lignite, peat, natural gas, and crude oil, and for nuclear and other renewable resources as well such as biomass, water, wind, and solar energy. Non-energetic resources such as water, minerals, and metals. \\ \hline Energy & Renewable and non-renewable resources, waste, soil loss, human labor, and water use \\ \hline CExC & Fossil resources, such as hard coal, lignite, peat, natural gas, and crude oil, and for nuclear and other renewable resources as well such as biomass, water, wind, and solar energy \\ \hline CEENE & Fossil resources, such as hard coal, lignite, peat, natural gas, and crude oil, and for nuclear and other renewable resources as well such as biomass, water, wind, and solar energy. Non-energetic resources such as water, minerals, and metals. Land use. \\ \hline \end{tabular}
\end{table} 
Table 4: Other LCA methodologies [65] (MEEup = Methodology study for Ecodesign of Energy-using Products; BEES = Building for Environmental and Economic Sustainability; EDP = Environmental Product Declaration; IPCC = Intergovernmental Panel on Climate Change; CED = Cumulative Energy Demand; CExC = Cumulative Exergy Consumption; CEENE = Cumulative Exergy Extracted from the Natural Environment). different carbon dioxide sources, and compare processes with and without carbon dioxide capture with equivalent products. In a carbon supply chain, if the compressed carbon dioxide is used as a feedstock, then it is a relevant input flow (process flow that remains inside the technosphere) that must be distinguished from carbon dioxide emissions. According to this, the carbon dioxide capture process can be considered as the production process for the feedstock carbon dioxide that is the product of a human transformation. For this reason, system boundaries should contain all upstream processes starting at the carbon dioxide sources that are the production center of the feedstock carbon dioxide. Together with the feedstock carbon dioxide, considered as the main valuable product, another product such as electricity or ammonia or similar is always co-produced. As shown in Figure 6, different kinds of carbon dioxide sources (non-biogenic, biogenic, air) exist. Power plants and industrial processes are non-biogenic point sources. On the other hand, plants for the production of biogas or bio-ethanol using biomass sources are biogenic point sources.