DTG profiles of bio-chars markedly differ from that of duckweed. In particular, there is no a trough at 270 °C in their DTG profiles, and the intermediate temperature trough is much more intense and shifted to lower temperatures (about 400 °C) compared to the un-pyrolyzed (virgin) duckweed sample. The high-temperature troughs are smaller and shifted to lower temperatures compared to the corresponding trough in the DTG curve of the duckweed sample. Interestingly, the bio-char sample produced at higher pyrolysis temperature (700 °C) exhibited a less intensive trough shifted to a lower temperature region (480 °C) compared to the sample produced at lower pyrolysis temperature of 500 °C (which shows a trough at about 510 °C). The troughs at 480 and 510 °C can be attributed to combustion of bio-char, whereas, nature of the rather strong trough at about 400 °C is yet to be fully understood. Most likely, this trough results from oxidative thermal degradation of non-volatile refractory organic compounds that resist pyrolysis, but are less resistant to oxidation than carbon. It should be noted that bio-chars produced by duckweed pyrolysis at the same temperature (500 °C), but different sweep gas flow rates behaved similarly, so their corresponding DTG data are not presented in this paper. TG thermograms of duckweed bio-chars are presented in the Supplementary Materials