Biochar, Bioremediation and Bioenergy

Dear Colleagues,

Heavy metal contamination is a major concern in today’s world. Both geogenic and anthropogenic activities are responsible for the increase in the metal concentration in the environment. These activities also negatively influence the beneficial microbiota of the soil. Plant growth-promoting rhizobacteria (PGPR) were found to be a promising additive for reducing contaminants by bioabsorption, biotransformation, bioaccumulation, and biomineralization, minimizing the transfer of these contaminants to plants. In addition, the charring of biomass under limited oxygen at a high temperature results in the generation of a carbonaceous material called “biochar”. With a high porosity and water holding capacity, as well as a wide range of pH values with multiple micro- and macro-nutrients, biochar is a promising additive in bioremediation. Moreover, the presence of various functional groups aid in the sorption of heavy metals, and thus, stabilizes their mobility. They provide shelter, nutrients and hydration, making the best place for the extensive growth of microorganisms, which helps in plant growth. Utilization of a high lignocellulosic and extensive shoot biomass of plants could be a great alternative for the production of biochar and bioenergy production, and thus, could help in carbon sequestration.

The aim of this Special Issue is to address all the above reported aspects including, but not limited to:

• Metal contamination assessment;
• Metal bioavailability and bioaccessibility;
• Plant and/or microbe-assisted bioremediation;
• Application of biochar in metal decontamination;
• Identification of high lignocellulosic biomass;
• Bioenergy production using biomass;
• Carbon sequestration, etc.

Dr. Adarsh Kumar
Dr. Dariusz Latowski
Guest Editors

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• heavy metals
• plants
• bioremediation
• biochar
• carbon sequestration

Title: Fate of Heavy Metals in Industrially Relevant Pyrolysis of Diverse Contaminated Organic Wastes: Phase Partitioning and pH-dependent Leaching
Authors: Erlend Sørmo 1,2,*; p Gabrielle Dublet Adli 1; Gladys Menlah 2; Gudny Flatabø 3,4; Valentina Zivanovic 2; Per Carlsson 3; Åsgeir Almås 2; Gerard Cornelissen1,2
Affiliation: 1. Geotechnics and Environment, Norwegian Geotechnical Institute (NGI), Oslo, Norway; 2. Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences (NMBU), Ås, Norway; 3. Scanship AS, Asker, Norway; 4. University of South-Eastern Norway (USN), Porsgrunn, Norway; *. corresponding author.
Abstract: Pyrolysis is a promising alternative for sustainable handling of contaminated organic waste, as it yields energy rich gas, oil, and a carbon-rich biochar product. However, low volatility compounds such as heavy metals (HMs, As, Cd, Cu, Cr, Ni, Pb and Zn) typically accumulate in biochars, limiting the application potential, especially for soil improvement. HM-distribution across the various pyrolysis products, however, depends on treatment temperature as well as metal and feedstock properties. The fate of HMs in the pyrolysis (500 – 800 °C) of seven contaminated feedstocks was therefore compared to a clean wood feedstock. Most of the HMs investigated accumulated in the biochar, but As, Cd, Pb and Zn were partly volatilized into the flue gas at temperatures ≥600 °C. As the fixation of certain HMs is unavoidable, their mobility was investigated, through pH-dependent leaching tests at pH-values of 4, 5.5 and 7. It was revealed that increasing pyrolysis temperature led to stronger incorporation in the sludge-based biochar matrix: after pyrolysis at 800 °C, at pH 4, <1% of Cr, Cu, Ni and Pb and < 10% of As and Zn were leached. Generally, HMs were observed to be more mobile in biochars produced from wood-based feedstocks than from sewage-sludge-based ones. This effect was so pronounced that biochar produced from a clean wood feedstock potentially could release more HMs than sewage sludge biochars upon application in an acidic soil in the short term.