Recycling of oil palm empty fruit bunch as potential carrier for biofertilizer formulation

Abstract

The palm oil industry generates large amount of biomass waste such as oil palm empty fruit bunch (EFB) and palm oil mill effluent (POME). This biomass would be typically recycled to produce EFB compost that is a valuable agricultural input. This study was conducted to evaluate the suitability of using EFB compost as carrier for nitrogen fixing bacteria (NFB) and phosphate solubilizing bacteria (PSB). Mixture (50-60% moisture) between EFB (shredded short fibres) and POME (anaerobic pond) were added with Effective Microorganisms (EM) to accelerate the composting process. The EFB compost reached thermophilic phase after 4-6 weeks with consistent temperature between 50- 60°C. After 7 weeks of composting, EFB compost reached the mesophilic phase with continuous reduction of temperature to 35-40°C at week 8. The maturity of the compost is supported from the reduction of the C/N ratio from 36 (initial) to 20 (after 6 weeks). Mature EFB compost was sun-dried and ground into fine particle size (1 mm) prior to be used as carrier. Dried EFB compost carrier has the following characteristics (dry weight); average pH at 7.5, C/N ratio - 13.5, moisture - 17.4%, organic matter – 74.5%, total N - 3.06%, P - 0.37%, K - 4.74%, Ca - 3.32% and Mg - 0.79%. The inoculation of NFB and PSB into the EFB compost carrier from single cultures of Serratia marcescens and Enterobacter cloacae showed high viable cell count at 4.05 × 109 CFU/g and 2.75 × 108 CFU/g respectively at day three after inoculation. Meanwhile, the mixed culture of Burkholderia cenocepacia with Serratia marcescens showed 2.45 × 108 CFU/g and 4.31 × 109 CFU/g respectively. This clearly indicates the potential of using EFB as a useful alternative for bacterial immobilization prior to application in the oil palm industries.