Design and economic analysis of a pre-treatment process of coffee husks biomass for an integrated bioenergy plant

The beneficiation of coffee produces a large amount of bio-waste, indicating that new policies need to be put into place to address the residues efficiently. Recent studies have shown that coffee husk, particularly, has significant potential for generating electricity but requires a pre-treatment step for efficient thermochemical conversion. Since information about the viability of a pre-treatment process is urgent and necessary and remains insufficient, this study aims to design and perform the economic analysis of a pre-treatment plant of coffee husks, which includes drying, comminution, and densification stages. Drying kinetics experiments were conducted at the laboratory scale to estimate the drying time for the dryer design. A methodology was proposed to encompass equipment design, use of utilities, investment, and total plant costs toward a definition of the optimal operating condition. The economic decision criteria were the net present value (NPV), the payback time (P), and the internal rate of return (IRR). The influence of the drying conditions was analyzed through the leveled cost of production per mass of the briquette (LCM). The results show that the bed height and air inlet temperature were the drying variables with the greatest influence on the design and economics of the plant. The lowest LCM values were obtained for higher values of air temperature, bed height, and biomass flow rate. Economic decision criteria indicated that the project is viable, with an NPV in the range of 28 to 98 million dollars, 166%–574% IRR, and a payback period of 7 months and 7 days. © 2023 The Author(s)