# Fewer Dimensions for Higher Thermal Performance: A Review on 2D Nanofluids
## 5 Life Cycle Assessment
### Graphene  
The study performed by Beloin-Saint-Pierre and Hischier [170] compared the previous Gr nanomaterial LCA studies with new results associated with ball milling of few-layer Gr. This study consisted of a reliable overview of the actual knowledge on the environmental sustainability of the Gr nanomaterials through three different life cycle impact assessment (LCIA) analyses. The international life cycle data (ILCD) midpoint method was chosen first since it provides the EI evaluation according to the general recommendations of the European Commission. This methodology enables the comparative examination of Gr nanomaterials in various EI categories by determining the involved extraction of the resources and emission of pollutants as a function of the equivalent effects of the polluting substances of reference for each category. The LCIA method IMPACT 2002+ was used at the endpoint or damage level. This approach advances one step and regroups the EI at midpoint into their effects on the climate change, human health, the ecosystem, and available natural resources. The ILCD and IMPACT 2002+ methods were chosen mainly because of their enhanced representativeness within the European context. The cumulative energy demand (CED) method returns the global cumulative energy needs. These LCIA methods were taken from the current Ecoinvent package. The results from the IMPACT 2002+ method were translated from points to kg of CO\({}_{2}\) equivalent (eq.) for the categories CC, PDE:m\({}^{2}\)-year for EQ, DALY for HH, and MJ primary for Res to facilitate the comparison with the ILCD and CED methods. The initial general finding is the major influence of the chemical products and electricity consumption in a Gr nanomaterial life cycle. Their relevance varies according to the type of Gr nanomaterial and manufacturing procedure. As an example, the EI from the GO synthesis mainly comes from the employment of chemical substances, whilst the impacts of Gr nanomaterial production are largely connected to the electricity consumption required, except for the ultrasonication procedure which is dominated by diethyl ether usage. These points highlight the main overall inputs on which the technology should be focused for EI mitigation in future manufacturing processes of Gr nanomaterials. Two general recommendations should be respected: the use of chemical products should be reduced (mainly in GO synthesis), and energy efficiency in production for all manufacturing processes should be pursued. These general recommendations are compliant with the green chemistry principles that provide the guidelines to decrease EI in the production of Gr nanomaterials. The contribution study confirmed that the usual discrepancy between the published works can be interpreted based on the different aggregation of the different system models rather than by the input dissimilarities for the considered manufacturing processes. This demonstrates the need for a study based on a harmonized framework, given that it clarifies that previous works exhibited a general agreement on the main contributors of the EI from the synthesis of Gr nanomaterials. The analyzed impacts for the solution of dry material offered new insights on the important meaning of the output state for Gr nanomaterials. Keeping Gr nanomaterials under solution may be environmentally benevolent if it can be directly employed as an input to the system. These findings also indicate that the recycling processes for chemical substances may cause a significant increase in the EI from Gr nanomaterial products if they require dialysis of their solutions. The selection of energy sources or country of production could bring a meaningful reduction in the potential impacts. Energy efficient recycling options to diminish the utilization of chemical substances may be pivotal to ensure the environmental benevolence of Gr nanomaterials.