Waste to Value Added Products: Graphene

Abstract

Globally, approximately 2 billion tons of solid waste is generated annually, of which 34-53% is composed of biodegradable organic materials (Abad et al. 2019). Organic fractions of municipal solid wastes (OFMSW); It consists of waste from food production, household residues from food preparation, leftovers, expired food, waste from restaurants and food outlets. While more than 100 billion tons of resources are transferred to the economy every year, more than 60% of them are waste and result in an increase in greenhouse gas emissions, which is one of the triggers of the climate crisis. EU; to improve sustainability in solid waste management, it has promoted some directives (1999/31/EC) to reduce production, encourage recycling, encourage resource selection and reduce biodegradable waste sent to landfill. The EU's aim for 2050 is to be the carbon neutral first continent, and in this direction, it plans all its policies under the name of "Green Deal". The Green Deal describes a framework that includes emission reduction, circular economy, zero pollution, transformation of agriculture and rural areas, sustainable transport, energy transition and financing all of these. In this context, the circular economy plays an important role in providing a conceptual way to minimize environmental impact and maximize resource (energy and material) recovery from solid waste. The anaerobic digestion (AD) process metabolizes the OFMSW to energy-rich biomethane and carbon dioxide by several microbial steps. The intermediates of AD can be transformed into value-added products, such as biofuels, biogas, bioethanol, etc. This review presents alternative value-added products such as "graphene" using biomethane from biogas by anaerobically digested OFMSW. This will close the loop of the life cycle of OFSMW via attaining a sustainable circular economy with a product with higher added value than biomethane. With this respect, the separation route of biomethane in transforming OFSMW into value-added products and graphene production techniques from biomethane are briefly assessed.