Development of passive evaporative cooling systems for tomatoes Part 1: construction material characterization

Abstract

The management of large volumes of agroforestry residues constitutes one of the global environmental challenges today.  These residues tend to accumulate in the environment, resulting in water, air and land pollution.  In response to rising costs associated with waste disposal and increasing environmental demands, the sustainable conversion of wastes into useful products is becoming increasingly important.  In the same vein, the quality and shelf life of tomatoes are compromised within a few days if not properly stored and preserved.  Although, a number of researchers have worked extensively on the development of evaporative cooling systems in an effort to tackle this menace, finding durable construction materials remains a challenge.  The broad objective of this study, therefore, was to develop passive evaporative coolers for tomatoes, using cement and clay-bonded composites from eggshell and sawdust as fabrication materials.  In phase one of the study herein reported, relevant engineering properties of laterite-sawdust, cement-sawdust and cement-eggshell ash-sawdust at mixing ratios of 9:1, 4:1 and 16:4:5 respectively were investigated, with laterite alone and concrete serving as the controls.  The results obtained showed a significant reduction (p<0.05) in density (36.1%-46.8% for clay-bonded and 53.5%-54.8% for cement-bonded samples), a significant increase in porosity (p<0.05), and a significant decrease in thermal conductivity of the composite materials as a result of the sawdust and egg shell ash incorporation.  There were, however, slight increase in moisture absorption and decrease impact energy absorption capacity of the composite materials.  These minor issues notwithstanding, sawdust and burnt egg shell are considered to be suitable potential construction materials for the fabrication of evaporative coolers for tomatoes.