Is Biochar from the Torrefaction of Sewage Sludge Hazardous Waste?
| Autor: | Andrzej Białowiec, Ewa Felis, Joanna Kalka, Marcelina Jureczko, Jakub Pulka, Jacek A. Koziel, Piotr Manczarski, Marzena Styczyńska |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
020209 energy
Daphnia magna Biomass 02 engineering and technology 010501 environmental sciences engineering.material Raw material 01 natural sciences lcsh:Technology Article leachability Biochar 0202 electrical engineering electronic engineering information engineering General Materials Science lcsh:Microscopy heavy metals 0105 earth and related environmental sciences Roasting lcsh:QC120-168.85 hydrophobicity waste to carbon biology lcsh:QH201-278.5 Chemistry lcsh:T toxicity Torrefaction biology.organism_classification Pulp and paper industry lcsh:TA1-2040 engineering lcsh:Descriptive and experimental mechanics Fertilizer lcsh:Electrical engineering. Electronics. Nuclear engineering lcsh:Engineering (General). Civil engineering (General) lcsh:TK1-9971 thermal treatment Sludge |
| Zdroj: | Materials Materials, Vol 13, Iss 3544, p 3544 (2020) Volume 13 Issue 16 |
| ISSN: | 1996-1944 |
| Popis: | Improved technologies are needed for sustainable management of sewage sludge (SS). The torrefaction (also known as biomass &ldquo roasting&rdquo ) is considered a pretreatment of SS before use in agriculture. However, it is not known whether the torrefaction has the potential to decrease heavy metals&rsquo (HMs) leachability and the SS toxicity. Thus, the aim of the study was to evaluate the influences of the SS torrefaction parameters (temperature and process time) on HM contents in biochar, HM leachability, and biochar toxicity, and compare them with raw SS. The experiments were designed in 18 combinations (six temperatures, 200, 220, 240, 260, 280, and 300 ° C and three process times&mdash 20, 40, 60 min). Standard tests were used to determine HMs content, leachability, and toxicity. Results indicated that the torrefaction did not increase (p < 0.05) the HM content in comparison to the raw SS. The leachability of Zn, Ni, Cu, Cr, and Mn from SS biochars was similar to raw SS. However, the degree of leachability varied significantly (p < 0.05) from as low as 0.1% for Cu to high as 16.7% for Cd. The leachability of Cd (< 16.7%) and Pb (< 11.9%) from biochars was higher than from raw SS (< 6.1% and < 2.4%, respectively). The leachability of Cd from SS biochar, in five torrefaction combinations, was higher than the threshold value for hazardous waste. It is recommended that site-specific decisions are made for torrefaction of SS with respect to its HM content, as the resulting biochar could be considered as hazardous waste, depending on the feedstock. Moreover, the biochar produced under the whole range of temperatures during 20 min retention time significantly (p < 0.05) increased the Daphnia magna Straus mobility inhibition by up to 100% in comparison to the biochar obtained during 40 and 60 min torrefaction. Taking into account the increased leachability of specific HMs and D. magna Straus mobility inhibition, biochar should be considered a potentially hazardous material. Future research should focus on biochar dosage as a fertilizer in relation to its toxicity. Additional research is warranted to focus on the optimization of SS torrefaction process parameters affecting the toxicity. |
| Databáze: | OpenAIRE |
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