A thermo-economic analysis of a circular economy model for biomass in South America producing biofertilizers and biogas from municipal solid waste

The linear economy model has caused many impacts associated with increased urban population and municipal solid waste generation worldwide. Through anaerobic digestion, the circular bioeconomy of biomass (methanogenic) provides a fuel (biogas) and an environmentally sustainable biofertilizer. This theoretical-descriptive research proposes a circular economic model based on the design of biorefineries using recycled biomass in urban areas. The model considers a minimum of 1.8 million people to generate approximately 650 tons/day for its application. The biorefinery configuration of the model consists of 12 biodigesters of 5400 m3 unit capacity and a spark ignition engine of 2 MW. The model is validated by employing a case study in the main urban cities of South America. Brazil with about 161,000 m3/day of biogas and 3100 tons/day of biofertilizer, and Paraguay, with 10,000 m3/day of biogas and 500 tons/day of biofertilizer, are the ones with the highest and lowest energy potential, respectively. The internal rate of return on investment in the case study is around 69%. The proposed circular economy model reduces greenhouse gas emissions and environmental impacts of municipal solid waste; Also, the environmental impact was estimated using different equivalence indicators between green electricity energy and carbon footprint avoided.