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20 figures, 7 tables.-- Supplementary information available.-- © 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/, Clean water is an essential resource for life, and its demand is continuously increasing with the rapid growth in population, while the freshwater reserves are also depleting. A large amount of wastewater is released by different industries, which is affecting the environment as well as polluting the freshwater reserves. Recycling and treatment of wastewater are highly essential to meet the demand for clean water and to protect the environment. Activated carbon can be used in primary, secondary and tertiary wastewater treatment steps. It can be used to capture pollutants which stop microbial activity or to produce clean water with high purity. About 3 million tons of activated carbon are produced per year and it is mainly used for fluid purification. The objective of this review is to investigate the preparation and production of biochar from lignin which is an important resource available in great quantities (about 100 Million tons per year) and the practical application of it for wastewater treatment. Biochar can be produced through pyrolysis (at temperatures of 600-700 °C) and hydrothermal carbonization (at temperature between 180-300 °C). Subsequent activation can be performed in two ways (physical and chemical), usually at temperatures between 600-800 °C. The quality of biochar and activated carbon produced from lignin-rich residue can be very high, even though the costs also are higher respect to other fossil derived materials (carbon black, lignite and pet coke)., The contribution of COST Action LignoCOST (CA17128), supported by COST (European Cooperation in Science and Technology), in promoting interaction, exchange of knowledge and collaborations in the field of lignin valorization is gratefully acknowledged. This work was developed during an STSM promoted by the e-COST European Cooperation in Science and Technology, among the UK Biochar research center at Edinburgh University UK, the BioCarbUp project at SINTEF Energy Research and the Biomass research center at Perugia University Italy. The Marie Curie GTCLC-NEG project that has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 101018756 is gratefully ackowledged. The 2014 Surfoly project: SUstainable Ruminants Feed with OLive pomace and polYphenols enriched charred olive stone, funded by the PRIMA program of the European Union is gratefully acknowledged.

Swine and chicken manures are abundant solid wastes that can be converted into carbonaceous materials through hydrothermal carbonization (HTC). Owing to their unique biochemical compositions, co-HTC of these two types of manures may have significant implications for the generated products. We investigated the co-HTC of swine manure and chicken manure to understand the influence of the interaction between contrasting manures on the properties of the derived products. The results indicated that co-HTC treatment enhanced the formation of solid product and improved the C and N contents, heating value, and energy yield of the resulting hydrochar. Regarding the ignition temperature and comprehensive combustion index, the combustion properties of the hydrochar were enhanced owing to the mutual effect of the HTC intermediates. Additionally, the interaction of the intermediates significantly impacted the transfer of nitrogenous species and generation of organic acids and organic polymers with fused-ring structures. Therefore, co-HTC processing of animal manures could potentially provide a sustainable pathway for the conversion of animal waste into solid products with improved characteristics compared to those produced by treating the two feedstocks separately Refereed/Peer-reviewed