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Abstract The CarbOn pilot plant is a continuous biomass carbonization system, rated for a capacity of up to 50 kg h−1 and based on open top, downdraft technology, operating in oxidative pyrolysis in the temperature range of 500–650 °C and equivalence ratio (ER) between 0.1 and 0.2. In the reported validation tests, carried out on small size chestnut woodchips, charcoal mass yield in excess of 22.4 ± 0.7 wt% (dry base) has been achieved, with a fixed carbon content higher than 85 wt% (dry base). The fixed carbon yield (FCy) was 18.2 ± 2.2 wt% (dry base), the char carbon yield (CCy) 38.3 ± 1.6 wt% (dry base) and the net energy conversion efficiency to char (ε) equal to 41.2 ± 2.2% (wet base). Volume concentration of permanent gases in the pyrolysis vapors and condensable species were also measured before incineration and critically compared against literature data. The organic condensate from oxidative pyrolysis was obtained as 4.9 wt% of the dry biomass, and around 58 wt% of its constituents have been identified; in order of decreasing abundance, the organic fraction of condensate was composed of organic acids, aromatics, furans, anhydrous sugars, phenols, methanol, PAHs, acetaldehyde, ketones. Measured and calculated performance data shows that the pilot unit can produce high quality charcoal, meeting and exceeding the product specifications set by standard EN 1860-2 for BBQ lump charcoal as well as those set forth by international voluntary standards on biochar quality for soil application. Graphical abstract Image 1 Highlights • Charcoal yield in excess of 22 wt% were obtained in autothermal carbonization. • Yield of condensable organics was 4.91 wt% of the dry biomass. • Attained energy yield in autothermal carbonization exceeding 41%. • Lower stack emission than traditional carbonization process, high T heat as co-product. • Charcoal has FC = 80.8 wt%, VM 17 wt%, Ash 2.2 wt%, BET 135.4 m2 g−1, PAH <2.5 mg kg−1. [ABSTRACT FROM AUTHOR]

The presence of contaminants considerably restricts the application of sewage sludge for the fertilisation and reclamation of soils. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and vary widely in sewage sludge depending on the input of industrial effluents. The objective of the study was the investigation whether the pyrolysis affect (reduces or adds) the total quantity of PAHs in sewage sludge-derived biochars and whether the pyrolysis changes the PAHs spectrum in terms of relative contributions of more hazardous components. Additionally, the trace metal content was determined before and after pyrolysis as well as the ecotoxicological parameters test towards plant ( Lepidium sativum ), bacteria ( Vibrio fischeri ) and crustacean ( Daphnia magna ). Sewage sludges conversion to biochar significantly reduced the content of PAHs (from 8- to 25-fold depending on pyrolysis temperature and kind of sludge). The exception was the content of naphthalene. Naphthalene was predominant in sewage sludge-derived biochars. However the concentration of the most hazardous 5- and 6-rings PAHs in sewage sludge-derived biochars was much lower compared to sewage sludge. The pyrolysis of sewage sludges caused also a significant reduction of their toxicity towards the test organisms. Only in the case of crustacean it was observed that the extracts from some biochars, obtained at higher temperatures (600 °C and 700 °C) were more toxic to D. magna than extracts from sewage sludge. In turn, after pyrolysis an increase was noted for trace metals content (Pb, Cd, Zn, Cu, Ni and Cr). [ABSTRACT FROM AUTHOR]