Effects of pyrolysis reactor types on the bioproduct compositions of tannery fleshing waste

The discharge of huge quantities of fleshing waste by the leather industries has raised serious concerns about its impact on the environment [1]. Quantitatively, one ton of raw material yields up to 800 kg of production-related wastes and by-products [2]. This study aims to investigate the effects of pyrolysis types (slow and fast) on the bioproduct compositions. The Tannery fleshing waste was dried under air (TFW-OD) and greenhouse (TFW-GD), the dried samples were characterized using several techniques: proximate analyses (moisture, volatile matter, ash, fixed carbon), elemental analyses CHNO, HHV, FTIR, and XRD. Pyrolysis was conducted using two different reactors: a fixed bed reactor and a heated strip reactor. In the fixed bed reactor, the final temperature was 500 °C, the heating rate was 10 °C/min and the residence time 60 min. In the heated strip reactor, 1000 °C was the final temperature, 1000°C/s was the heating rate, and 3 seconds was the residence time. The produced biochars were characterized by proximate analyses, elemental analyses CHN-O, FTIR, XRD, and the bio-oils were characterized by GC/MS. As far as biochars are concerned, both slow and fast pyrolysis TFW-GD bio-chars have a comparable carbon content of around 30 wt.%, the carbon content of chars from slow and fast pyrolysis of TFW-OD is instead quite different (41.07 vs 28.12 wt. %). All chars are rich in Ca, Si, and Mg, even though differences in the mineralogical form are observed between OD and GD samples due to the occurrence of saponification reaction. On the whole, all biochars are interesting for agronomical and environmental uses (biofertilizer, bioadsorbents, or for soil remediation). Bio-oils collected by slow and fast pyrolysis are quite different in terms of share of aromatic vs. aliphatic compounds, the fast pyrolysis tars being all richer in aromatics. However, the large presence of N and O in both aliphatic and aromatic compounds calls for further upgrading before utilization of these products of TFW pyrolysis as biofuels.