Yields and characteristics of bio-oil and biochar from fast pyrolysis and co-pyrolysis of oil palm biomass using innovative twin screw reactor for bio-circular-green economy approach

Biomass pyrolysis is a challenging but promising approach to a bio-circular-green economy, converting organic waste into valuable products such as bio-oil, biochar, and biochemicals. Therefore, the aim of this study was to investigate the yields and properties of bio-oil and biochar produced from the fast pyrolysis and co-pyrolysis of palm kernel shells (PKS), empty fruit bunches (EFB), and palm mesocarp fibers (PMF) using a twin-screw reactor with an omega-shaped vessel. Continuous fast pyrolysis and co-pyrolysis were conducted at 450–550 °C for 60 min under an inert atmosphere. The results showed that the yields of total liquid products ranged from 38.91 to 48.28%. Pyrolysis of PKS produced the highest yield of a major fraction of bio-oil (38.39%), followed by PMF (35.61%) and EFB (29.06%). The major fraction of bio-oil from PKS exhibited the lowest water content (22.15%) and the highest heating value (19.58 MJ/kg). With co-pyrolysis, a combination of PKS and PMF at 475 °C led to the maximum bio-oil yield (33.70%) and energy content (18.58 MJ/kg). GC–MS analysis indicated that co-pyrolysis influenced the bio-oil’s chemical composition. Biochar derived from PKS or PKS-based mixtures demonstrated superior bulk density, energy content, fuel ratio, and atomic ratios over the biochars from PMF or EFB. However, the biochar samples from EFB and PMF had high silicon (Si) and potassium (K) contents, as indicated by X-ray fluorescence spectrometry (XRF). Based on these results, the PKS should be the main feedstock for fast co-pyrolysis with PMF or EFB to enhance the yields and characteristics of products for use as biofuels or for upgrading to high-value products. This co-pyrolysis helps the utilization of oil palm biomass to support the bio-circular-green economy by optimizing resources and reducing waste.