Sustainable transformation of palm oil mill waste into organic fertilizer through vermicomposting.

Abstract

Crude palm oil production is one of the major industries in Malaysia and this country is one of the major exporters of palm oil globally. The increasing global demand for edible oils has resulted in the increase of oil palm cultivation. The rapid expansion of the oil palm industry inevitably contributes to the growth and development of the national agriculture industry but there are concerns over the large amount of waste that are being generated. Among the by-products generated from crude palm oil processing that are of interest in this study are palm oil mill effluent (POME) and decanter cake (DC). The most typical method for managing POME is the ponding system while DC is usually left for natural degradation in most mills. Ponding system is the most common treatment method for POME in Malaysia whereby it is used in more than 91% of the mills. This method is economically viable but it produces large amount of sludge, releases CH4 and CO2 into the atmosphere and requires large areas of land. As DC is left for natural degradation, its accumulation over time could pose some environmental issues. The application of non-stabilized waste could lead to immobilization of plant nutrients and cause phytotoxicity. Thus, vermicomposting process was presented as an alternative treatment technology to manage POME and DC. The ability of vermicomposting process to utilize organic waste and bio-convert them into higher value added products makes it an attractive treatment option. Vermicomposting is the natural conversion of organic waste into organic fertilizer, i.e. vermicompost with the help of earthworms. The vermicomposting process is known to have a much higher rate of organic waste decomposition than composting and its product is rich in nutrients with finer texture. Vermicompost can be used for agricultural application. Thus, the vermicompost produced needs to be evaluated for its maturity to ensure that it is safe for a particular end use. Vermicompost maturity can be determined using chemical, biological and instrumental analysis. Generally, it is recommended to use several different maturity tests to ascertain the feasibility of the vermicompost produced. The land application after vermicomposting is regarded as the most beneficial waste disposal option in terms of the agronomic potential and environmental benefits of vermicompost. Therefore, in this study the feasibility of managing POME and DC through vermicomposting process was investigated.