A novel method that CaO was modified with the by-product of biodiesel by the combustion was proposed to improve its CO2 capture capacity at calcium looping conditions. The CO2 capture performance of CaO modified with the by-product of biodiesel during the calcium looping cycles was investigated in a twin fixed-bed reactor and a thermogravimetric analyzer. The effects of ratio of by-product of biodiesel to CaO, combustion duration and temperature on the CO2 capture performance of CaO modified with the byproduct of biodiesel were studied. When the ratio of by-product of biodiesel/CaO is 25 mL/g, the modified CaO achieves the highest CO2 capture capacity during the cycles. The feasible combustion temperature and duration are 800 degrees C and 60 min, respectively. CO2 capture capacity of the modified CaO can retain 0.5 g CO2/g sorbent after 20 cycles (carbonation at 700 degrees C for 20 min in 20% CO2/80% N-2, calcination at 850 degrees C for 10 min in N-2), which is higher than that of the modified CaO with the various organic solutions. The modified CaO still shows much higher CO2 capture capacity than original CaO under the severe calcination condition. The by-product of biodiesel modification greatly improves CO2 capture rate of CaO in the chemical-controlled stage, but shows a little effect on rate in the diffusion-controlled stage. The cyclic CO2 capture capacity of the deactivated CaO is significantly reactivated after the by-product of biodiesel modification. The modified CaO exhibits more porous structure and higher sintering resistance during the CO2 capture cycles. (C) 2017 Elsevier B.V. All rights reserved.