Effect of Bone during Fixed Bed Pyrolysis of Pistachio Nut Shell

Abstract

Biomass will constitute a major part of the renewable energy matrix in the future. The large scale utilization of biomass, however, is constrained by its wide geophysical spread, low energy density and poor fuel quality. Pyrolysis-based bio-char and bio-oil production is a promising way to simultaneously achieve solid carbon sequestration and co-produced bio-oil with increased energy density and improved fuel quality. This paper provides new data on copyrolysis of 10wt% bone meal blended with pistachio nut shell and its effects on the yields of bio-char, bio-oil and non condensable gases. In particular the bio-char was found to be suitable for soil amendment. A fixed bed pyrolysis reactor was used to investigate the effect of the addition of 10 wt% bone meal (BM) to pistachio nut shell (PS) to produced bio-chars and bio-oils up to 6000C. At 350°C the char yield was 53.3wt% for PSBM10 (sample containing 90wt% of PS and 10 wt% of BM) compared to only 30.9wt% for the PS alone. This was linked with the ability of the PSBM10 to retain condensable compounds at this temperature. The formation of condensable liquids from the PSBM10 reached 48 wt% at 550°C compared to only 20 wt% for the PS alone. The H/C atomic ratio for this PS bio-oil was 1.01 which increased to 1.11 for the PSBM10 bio-oil indicating an improvement in the bio-oil quality for the co-pyrolysis with bone, where the calorific value increased from 18.5 MJ/kg for the PS bio-oil to 19.9 for the PSBM10 bio-oil The bio-char stability in terms of the ratio of volatile matter (VM) to that of fixed carbon (FC) content confirmed that at 300°C the PSBM10 char retained more condensable compounds with a VM/FC ratio of 1.60 compared to 1.10 for the PS char. At 400°C the VM/FC ratio decreased rapidly down to 0.15 for the PSBM10 compared with 0.25 for the PS alone reflecting the release of condensable liquids from the PSBM10. The PSBM10 biochar at 550°C contained 0.45 wt% nitrogen compared with 0.18 wt% for the PS char which suggest increase in nitrogen availability in the char from co-pyrolysis with bone at this temperature. From E.A, SEM-EDS and XRD analysis, the reaction mechanisms between bone mater and PS involved dehydration and decarboxylation which is promoted by CaO from the bone matter. Also, the inhibition of the depolymerization stage of pyrolysis of biomass by Ca2+ lead to high char yield at the expense of volatile release. These results indicate that a combination of bone and biomass could yield bio-chars suitable for soil amendment, and possibly carbon sequestration, while improving the production of bio-liquids for renewable energy.