The effect of raw material moisture and particle size on agri-pellet production parameters and physical properties: A case study for greenhouse melon residues

Abstract

There are many agricultural residues that can be considered as biomass raw materials according to the region where it grows. Due to the physical and chemical diversity of agricultural residues, pelleting conditions and pellet properties need to be determined for effective use. Aim of this study is to determine the pelletizing conditions and pellet properties of melon stalks from greenhouse residues that can be biomass raw materials. In this study, the stalks obtained after harvest operations in greenhouse melon cultivation were milled with two different sieve hole diameters as 4 mm (M4) and 6 mm (M6). The ground material was pelleted at two moisture content, 10% (M4-10; M6-10) and 15% (M4-15; M6-15). During the pelletizing process, the highest pellet production capacity (103.86 kg/h) and the lowest specific energy consumption (73.92 kWh/ton) were obtained in M4-15 pellets. Regarding pellet physical properties, the effect of pelletizing moisture on pellet moisture content, bulk density, single pellet density and durability index were statistically significant, while particle size only affected the bulk density (p < 0.05). Pelletizing moisture caused a decrease in durability index and bulk density for both particle sizes. At the end of the study, it was observed that the melon stalk pellets met ENplus pellet standards in terms of pellet moisture, bulk density and durability. Although the pelletizing process is easy and efficient, the high ash content (20.73%) and low calorific value (11.92 MJ/kg) of melon stalks may prevent it from being used as solid fuel in domestic heating systems.