Effects of temperature and aeration rate on composting of empty fruit bunches (EFB) from oil-palm

Abstract

Composting is a biochemical process in a controlled aerobic environment where thermophilic microorganisms stabilize organic waste substrates into valuable humus-like products. With the aim to enhance the efficiency of composting and yield high quality compost, a modified composting technique known as co-composting had been introduced and widely used in the past decades. This technique utilizes other biodegradable wastes as well as addition of chemical substances to increase the rate of degradation and optimize the carbon to nitrogen (C:N) ratio. With the right application, co-composting has a great potential for high economic return. Two parameters which are known to affect the composting process include temperature and aeration rate. This research aimed at developing a model to describe the relative influence of different temperatures and aeration rates on the composting process and how it affects the final quality of EFB compost produced. EFB samples were mixed with urea as a source of nitrogen and young compost as inoculum. The composting process was carried out in a composting test bench with a hot water jacket to manipulate the temperature and an air flow meter to manipulate the aeration rate for a total of 42 days. Moisture contents of samples were monitored over time; pH and conductivity tests were carried out for analyzing purposes. Samples obtained weekly were also tested for elements such as carbon, nitrogen, phosphorus, potassium, calcium, iron, magnesium, manganese and zinc to determine the C:N ratio and amount of ions being released. The release of ions over time showed a positive correlation with the value of conductivity whereas the largest reduction in C:N ratio (from 30.2:1 to 17.6:1) was obtained at temperature 40°C and aeration rate of 0.4 L/min kg. The results of this study could form a basis for palm oil mills to improve the quality of EFB composts produced within a short maturation period and with low C:N ratio.