Performance Evaluation of a Developed Dried Grass Shredding Machine for Composting

Abstract

In Nigeria Arable land covers approximately 745,000km2 of the total land area and at present organic farming is not prevalent, encouraged or facilitated despite its sustainability advantages. The anaerobic digestion process produces two main outputs (biogas and digestate). The digestate when properly harnessed can be used as a substitute for inorganic fertilizer. The digestate retains a high content of organic matter such as Nitrogen, Phosphorous and Potassium (K), as well as a range of other macro-and micronutrients like Calcium, Magnesium, Iron, Manganese, Zinc and ammonium. In this research work, a developed grass shredding machine for the composting of a digestate was evaluated for performance. Preliminary studies were undertaken to determine the liquid absorbability of non-shredded grass vise-visa dry shredded grass, the moisture content of fresh elephant and spear grass. An internal combustion powered shredding machine was developed to shred dry and sieve crushed grasses to be used as absorbent of digestate. The machine was evaluated for performance using different samples of properly dried elephant and spear grass. The shredded grasses samples were mixed with discharge digestate collected from a bio-digester to produce organic fertilizer. The shredding time, machine throughout capacity efficiency, mass of fibre and liquor were determined. The results of performance evaluation with elephant grass sample revealed that an average value of efficiency (90.97%), machine through put capacity (1.225g/sec), shredding time (126.54seconds), percentage loss (8.393%), fibre (288.58g) and liquor (119.83g) were established. Similar result were obtained with spear grass; efficiency (90.50%), machine through-put capacity (1.225g/sec), shredding time 126.54 seconds), percentage loss (8.32%), fibre (294.12g), and liquor (118.85g). The outcome of the results revealed that both solid fertilizer (fibre) and liquid fertilizer (liquor) were extracted from the digestate, and an average mass of 138.86g dried grass can absorb 269.55g of liquid digestate to produce organic fertilizer.