Co-composting of palm empty fruit bunch and palm oil mill effluent: microbial diversity and potential mitigation of greenhouse gas emission

Abstract

The identification of microbial diversity is important to speed up the co-composting process of EFB and POME from the palm oil mills, as an effective and cost-efficient way, to treat the residues and reducing the greenhouse gas emission. This study was conducted to identify the microbial diversity from EFB-POME co-compost and to evaluate its potential mitigation of greenhouse gas emission. The physiochemical properties such as temperature (°C), pH and moisture content of the EFB-POME co-compost were measured. The microbial diversity was identified by 16S rRNA and 18S rRNA gene metagenomic sequencing analysis. The temperature, pH and moisture content recorded for the surface compost and inside compost were 30 °C, 7.43 and 58.76%, and 45 °C, 7.94 and 60.56%, respectively. Based on the 16S rRNA gene sequencing for the identification of bacteria, the dominant genera in the surface compost were Nitriliruptor, Delftia, Filomicrobium, Steroidobacter, and Ohtaekwangia; the dominant genera in the inside compost were Steroidobacter, Nitriliruptor, Anaeromyxobacter, Filomicrobium, and Truepera; and the dominant genera in the POME were Parabacteroides, Bellilinea, Levilinea, Smithella, and Prolixibacter. Based on the 18S rRNA gene sequencing for the identification of fungal, the dominant genera in the surface compost were Remersonia, Inonotus, Kluyveromyces, Chaetomium, Thermomyces, and Candida; the dominant genera in the inside compost were Remersonia, Inonotus, Saccharomycopsis, Chaetomium, and Saccobolus; and the dominant genera in the POME were Kluyveromyces, Inonotus, Kazachstania, Candida, andCystofilobasidium. The co-composting of EFB-POME is estimated to reduce up to 76% of greenhouse gas emission by avoiding the methane gas emission from the EFB open dumping and POME treatment ponds, as well as from the replacement of chemical fertilizers. The microbial diversity identified from EFB-POME compost and POME may enhance the effectiveness of co-composting due to the ability to synthesize ligninolytic and cellulolytic enzymes and reduce the emission of greenhouse gases from the oil palm plantations.