Optimization the specific energy consumption in compost manure extrusion process using response surface methodology

Document Type : Research Paper


1 Former Graduate Student University College of Abureihan, University of Tehran, Iran

2 Associate Professor, University College of Abureihan, University of Tehran, Iran


Densification of biomass material that usually has a low density is proper way to increasing density,
reduce transportation cost and simplify storage and distribution of these materials. Pellet production
using extrusion process is a common method for densification. The goal of this research is
optimization of specific energy consumption for extrusion process considering its effect on pellet
density. Compost was extruded into cylindrical pellets utilizing open-end dies under axial stress
from a vertical piston applied by a hydraulic press. The effects of independent variables, including
the raw material moisture content (35, 40 and 45% (w.b.)), particles size (0.3, 0.9 and 1.5 mm),
speed of piston (2, 6 and10 mm/s), and die length (8, 10 and 12 mm) on specific energy
consumption and pellet density, were determined. The experiments were designed using response
surface methodology based on Box Behnken design (BBD) in order to optimize. The results
revealed that all independent variables have significant effects on studied responses in this research
at Pwere: moisture content between 40-45%, speed of 2 mm/s, particle size from 0.8 to 1 mm and die
lengths of 10 to 12 mm.