Biogas, hydrogen, green ammonia and electricity production from canned peach processing residues: Aspects of the circular economy for the Brazilian agroindustry

Growing environmental concerns have led several countries to seek renewable energy sources, such as bioenergy. Bioenergy is generated from biomass, but, its viability depends on its availability. Waste from the food sector is generated in large quantities, an example is the solid waste generated in the processing of peaches in syrup. The state of Rio Grande do Sul is one of the largest peach producers in Brazil. Peaches are part of the state's economy, and are processed in the candy and juice industries, generating employment and income for the producing municipalities. Waste from this activity sometimes end up being discarded, used as fertilizer or used as animal feed. However, this biomass could be converted into biofuels, bioenergy and biofertilizer, filling energy deficiencies in the industries themselves and in the region. However, there are no studies in the scientific literature addressing the conversion of waste from the canned peach industry to generate biofuels. Therefore, this study aimed to estimate the energy potential of generating biogas, hydrogen, ammonia, chemical and electrical energy from the peach canning industries residues in the state of Rio Grande do Sul/BR, as well as to propose sustainable models of production, since these residues have little explored energy potential and the fruits are of paramount importance in the Brazilian food chain. For the generation hydrogen, the steam reforming process of purified biogas was applied as methodology. The results obtained indicated the generation of around 6.3 thousand tons/year of waste, with a generation capacity of 5.16E+05 m³/year of biogas, 3.10E+06 kWh/year of energy and 9.29E+ 05 kWh/year of electricity from biogas. With the use of biogas produced in steam reforming processes, it was estimated the production of 88.6 tons of H₂ per year, 2337.96 m³ of compressed H₂ and the generation of 3.5E+03 kWh of electrical energy using a PEMFC, which is a type of fuel cell that generates electrical energy from hydrogen and oxygen. The economic analysis showed a cost of 132 895 USD for ammonia production and a sales profit of 101 611 USD. The investment for biogas treatment was estimated at 904 million dollars in total for proven industries. The estimated costs for hydrogen production were around $407,000. The creation of an industrial park for these industries was proposed, through industrial symbiosis. Therefore, the biological treatment of waste could promote the mitigation of environmental impacts and generates renewable energy, as a sustainable pathway for the country based on the concepts of circular economy.