Palm kernel shell (PKS) biochars with different levels of carbon conversion were initially prepared using a tube furnace, after which the reactivity of each sample was assessed with a thermogravimetric analyzer under a CO2 atmosphere. The pore structure and carbon ordering of each biochar also examined, employing a surface area analyzer and a Raman spectroscopy. Thermogravimetric results showed that the gasification index R s of the PKS biochar decreased from 0.0305 min(-1) at carbon conversion (x) = 20% to 0.0278 min(-1) at x = 40%. The expansion of micropores was the dominant process during the pore structure evolution, ad mesopores with sizes ranging from 6 to 20, 48 to 50 nm were primarily generated during gasification under a CO2/H2O mixture. The proportion of amorphous carbon in the PKS biochar decreased significantly as x increased, suggesting that the proportion of ordered carbon was increased during the CO2/H2O mixed gasification. A significantly reduced total reaction time was observed when employing a CO2/intermittent H2O process along with an 83.46% reduction in the steam feed, compared with the amount required using a CO2/H2O atmosphere. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.