Waste valorization as an example of circular economy in extremadura (Spain)

Abstract

Abstract This work demonstrates the possibility of implementing clean, renewable technologies that allow profitable value to be drawn from the highly contaminant waste of a broiler industry. An anaerobic digestion (AD) process can significantly reduce the overall chemical oxygen demand (COD), and the digestate's COD is also reduced to within legal limits by the process of separating its liquid and solid phases. The resulting liquid phase complies with regulations regarding discharge into the sewerage network or irrigation of crops with whose fruit it does not come in contact. The solid phase can be subjected to composting, obtaining an agricultural amendment of good quality. The materials used in the construction of the plant (steel, iron, concrete, paints, polyurethane, and PVC and HDPE plastics) are easily reusable or recyclable using standard technologies once the AD plant has reached the end of its service life (25–30 years). The study of the economic feasibility of the industrial plant, based on previous results, showed that the period of return on investment (PRI), net present value (NPV), and internal rate of return (IRR) economic parameters are highly favourable. In particular, with the use of this technology, a PRI of 7 years and IRR of 14% are achieved. That the plant is economically viable shows that the use of conventional materials would not represent any significant economic savings compared with the use of materials that have standardized protocols for their recycling, with the consequent reduction in negative environmental impacts.