Improving Mechanical Coffee Drying with Recycled Insulating Materials: A Thermal Efficiency and Economic Feasibility Analysis

TL;DR

This study shows that using recycled polystyrene insulation in coffee dryers improves energy efficiency and reduces costs, making coffee production more sustainable.

Contribution

The study introduces expanded polystyrene as a cost-effective and sustainable insulation material for mechanical coffee drying.

Findings

EPS insulation reduced drying time by 7.82% and fuel consumption by 13.9%.

EPS increased overall efficiency by 6.7% and reduced wall heat losses by 37.7%.

EPS provided annual savings of USD 81.5 with a 0.45-year payback period.

Abstract

Mechanical coffee drying is an energy-intensive stage of postharvest processing that directly affects product quality and production costs. This study evaluated the technical and economic feasibility of using expanded polystyrene (EPS) as a thermal insulation material to improve the performance of a mechanical coffee dryer and to demonstrate its potential for sustainable reuse. Experiments were conducted using a total of 210 kg of wet parchment coffee (Coffea arabica L. var. Cenicafé 1) per treatment, corresponding to three experimental replicates of 70 kg each, dried at 50 ± 2 °C, comparing an EPS-insulated dryer (0.02 m thickness) with a non-insulated control. A theoretical model based on steady-state heat transfer through series resistances estimated energy losses and system efficiency for different insulating materials. Theoretical results indicated that EPS, polyethylene foam, and cork reduced heat losses by 58.1%, 54.3%, and 50.9%, respectively. Experimentally, EPS reduced drying time by 7.82%, fuel consumption by 13.9%, and energy demand by 9.5%, while increasing overall efficiency by 6.7% and reducing wall heat losses by 37.7%. Improved temperature stability enhanced heat retention and moisture migration behavior. Economically, EPS reduced operating costs, yielding annual savings of USD 81.5, a 0.45-year payback period, and an annual return on investment (ROI) of 10.86, confirming its viability as a cost-effective and sustainable solution for improving energy efficiency in mechanical coffee drying.

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