Fig. 3: Life cycle assessment of various flash graphene (for one gram graphene production).

a Contribution analysis on the GHG emissions derived from 1 g of flash graphene produced by the five production systems in terms of pyrolytic volatiles release, structure optimization, and carbon black utilization. Asterisk note: for the FG system of path A, quartz tubes phase contributes 11.1% to the total climate change impact. Quartz tubes consumed in Paths B-E make negligible contributions (less than 1%). b Material flow of five different biomass flash graphene production paths from biomass (Path A) and biochar (Path B-E) to flash graphene. “Loss1” refers to the pyrolytic volatiles (bio-oil as the main composition) and depletion in AC-FJH. “Loss2” refers to the pyrolytic volatiles (probably bio-oil or gas) and depletion in DC-FJH. *Note: for 1 gram graphene production, 92 times AC-FJH reactions are required in Path A, while only 11 times in Path C-E. Therefore, a high accumulated depletion value is formed in Path A. Overall, a high loss value in path A is formed. ^#Note: for 1 gram of graphene produced, 11- and 12-times DC-FJH reactions are required in Path A and B, while only 6 times in the Path C-E. Therefore, a high accumulated depletion and loss value in paths A and B is formed. c Comparison of the energy requirement of biomass-based flash graphene production path by FJH with biochar-based flash graphene by pyrolysis-FJH nexus. The green-highlighted area represents the energy gap between the two paths. The flash graphene fabrication process is divided into carbonization, graphitization, and exfoliation. d Comparison of life cycle GHG emissions between biomass-based flash graphene system and biochar-based flash graphene systems. e Life cycle environmental impacts of biomass-based flash graphene system (Path A) and biochar-based FG systems (Path B-E). For each impact category, the highest impact value is set to be 100%, and the value of other paths equals the percentage shares of each product system based on this highest impact. FD fossil depletion, TA terrestrial acidification, FEP freshwater eutrophication, MD metal depletion, PMF particulate matter formation, POF photochemical oxidant formation, WD water depletion.