High-grade activated carbon from pyrolytic biochar of Jatropha and Karanja oil seed cakes—Indian biodiesel industry wastes

Most of the commercially available pyrolysis plants use fluidized bed technologies where bio-oil is the major product and the biochar produced is combusted for process heat. However, auger-based technologies are now gaining importance because of their small to medium scale of operation and decentralized nature where biochar is obtained as a by-product. One of the factors which may greatly influence the techno-economic viability of such decentralized plants is making high-grade carbon from pyrolytic biochar. In the present study, Jatropha and Karanja oil seed cake-based biochar is obtained as a by-product in a pilot-scale (20 kg/h) direct gas-fired auger pyrolysis process at 500 °C under fast pyrolysis conditions that is originally aimed at maximizing the bio-oil yield. The biochar has low surface area and porosity. To value add to this carbon, downstream physical and chemical activation are carried out in an externally heated laboratory-scale reactor. CO 2 activation resulted in the formation of activated carbon with BET surface area up to ~ 200 m 2 /g with marginal improvement in porosity, while K 2 CO 3 activation enhanced the surface area to as high as 2400 m 2 /g along with substantial enhancement of porosity.