Martín-Gamboa, Mario; Dufour, Javier; Iribarren, Diego

Systems based on biogas generation from waste and subsequent upgrading to renewable natural gas (RNG) have gained attention as a relevant option in the path towards a global sustainable energy system. This has gone hand in hand with the development of technical, economic and environmental evaluations to measure the performance of those systems. In contrast, social analysis of RNG has not yet been thoroughly addressed. This work uses the Social Life Cycle Assessment (S-LCA) methodology along with a robust supply chain protocol to evaluate the social performance of RNG from a system including manure fermentation and biogas methanation with electrochemical hydrogen in Spain. The product system encompasses three supply-chain tiers built by a combined use of life cycle inventory and trade databases, and evaluated by using the PSILCA database and method. Four social hotspots were identified: construction and maintenance of the facility in Spain (regarding e.g. women in the sectoral labour force and gender wage gap, respectively), production of titanium plates in Senegal for electrolyser manufacturing (regarding e.g. child labour), and crude oil extraction in Russia associated with diesel as a heat source in methanation reactor assembly (regarding e.g. drinking water coverage). When comparing the social life-cycle profile of RNG with that of fossil natural gas produced in Algeria, the identification of the most appropriate system was found to be highly dependent on the specific indicators under consideration. For instance, RNG would involve a better social performance in terms of child labour and illiteracy, but worse in terms of health expenditure and gender wage gap. This suggests a high potential for a favourable social performance of RNG once measures oriented to increase overall process efficiency are implemented.