Valorization of Oil Palm Empty Fruit Bunches into Biochar: A Sustainable Strategy for Soil Improvement and Carbon Management

Abstract

Oil palm empty fruit bunches are the largest solid residue stream leaving a palm oil mill, and their conversion into biochar offers a route that simultaneously addresses waste management, soil degradation, and carbon storage. This paper synthesises published evidence on empty fruit bunch biochar to establish how pyrolysis conditions govern product properties, what agronomic response can be expected under tropical soil conditions, and how large the carbon management contribution is likely to be. Peer-reviewed studies indexed in Scopus and SINTA and published between 2010 and 2025 were retrieved and screened for reporting of pyrolysis parameters, biochar characterisation, or soil and crop response, and the retained records were analysed comparatively across three domains: production conditions, material properties, and field outcomes. The evidence shows a consistent directional relationship in which increasing pyrolysis temperature raises pH, ash content, electrical conductivity, and fixed carbon while reducing yield, cation exchange capacity, and nitrogen retention, so that no single temperature optimises all functions simultaneously. Agronomically, meta-analytic evidence indicates that empty fruit bunch amendment increases crop growth and yield by approximately half relative to unamended soils, with pyrolysed material outperforming raw, composted, and ash forms. For carbon management, the aromatic structure conferred by pyrolysis confers residence times far exceeding those of raw residue returned to the field. The paper concludes that biochar production should be specified against an intended function rather than pursued as a single standardised product, and identifies the absence of national quality specifications as the principal barrier to commercial deployment.