An integrated strategy targeting drying and cooling unit operations to improve economic viability and reduce environmental impacts in a mango processing plant

Abstract

An integrated strategy of replacing boiler fuel and vapour compression cooling technology in dried mango chips processing plant powered on-grid and off-grid was investigated. Three scenarios for each power setting were studied: on-grid: coal as boiler fuel and conventional vapour compression chiller (CVCC) for cooling (scenario 1), mango seed as boiler fuel and CVCC for cooling (scenario 2) and mango seed as boiler fuel and adsorption cooling system (ACS) for cooling (scenario 3). Off-grid scenarios 4, 5 and 6 corresponded to on-grid scenarios 1, 2 and 3, respectively. Greenhouse gas (GHG) emissions and economic viability for each scenario were based on material and energy balances and South African economic conditions, respectively. On-grid scenario 3 showed the greatest potential for reducing emissions, emitting 7.10 × 105 kg CO2eq per annum and had best internal rate of return (IRR) of 25.33% compared to scenarios 2 and 1 with 7.21 × 105 kg CO2eq and 7.89 × 105 kg CO2eq emissions per annum and IRR of 20.33% and 17.48%, respectively. In off-grid, scenario 6 emitted the least GHG of 6.90 × 105 kg CO2eq and had the highest IRR of 24.84% compared to scenarios 5 and 4 with 6.98 × 105 kg CO2eq and 7.67 × 105 kg CO2eq emissions per annum and IRR of 18.88% and 16.09%, respectively. However, scenarios 3 and 6 had the highest energy demand due to mango seed drying. Nevertheless, the integrated intervention shows a great potential of reducing environmental impacts and improving the economic viability of a dried mango chips processing plant by using renewable biomass fuel and ACS that utilizes boiler waste heat. Mango seed can be solar dried to reduce increased energy demand.