News out yesterdayDundee Sustainable Technologies Inc.NEWS RELEASEDST ANNOUNCES POSITIVE RESULTS FROM GIANT MINE FLUE DUSTS USING GLASSLOCK PROCESSTM AND APPOINTMENTSMONTREAL, QUEBEC, April 22, 2021 – Dundee Sustainable Technologies Inc. (“DST” or the “Corporation”) (CSE: DST) is pleased to announce that it has completed a metallurgical testing program with the Giant Mine Oversight Board (“GMOB”) to apply its GlassLock ProcessTM(“GlassLock” or the “Technology”) on arsenic trioxide material from the Giant Mine site located in Yellowknife in the Northwest Territories. The testing program was done on samples received from GMOB from the 237,000 tonnes of legacy arsenic trioxide stored on site. GMOB has a mandate to support research that will identify a permanent solution for the management of arsenic trioxide stored underground at Giant Mine. Working with NSERC-TERRE-NET (a consortium of researchers specializing in the management of mine wastes), GMOB is currently evaluating multiple arsenic trioxide stabilization techniques, one of which is vitrification.DST produced kilogram scale, arsenical glass samples using GlassLock on arsenic trioxide provided by GMOB. Based on analyses by DST, glass samples containing over 12% arsenic successfully met the requirements of the U.S. Environmental Protection Agency’s (“EPA”) Toxicity Characterization Leaching Procedure (“TCLP”, Method 1311). The vitrified samples will be assessed by GMOB and NSERC-TERRE-NET to evaluate the amenability of the Technology to provide a viable remediation solution to the situation prevailing at the Giant Mine site. “The management of DST is very pleased with the results to date and look forward to continuing its collaboration with GMOB and NSERC-TERRE-NET. The Giant Mine site is an important Canadian remediation project and DST supports GMOB in its objective of developing a long- term and permanent remediation process for the Giant Mine site and local communities.” stated Mr. David Lemieux, the President and CEO of the Corporation. As previously reported (DST Press Release dated September 13, 2017 and DST Press Release dated May 26, 2020), a State of Knowledge Review report prepared by Arcadis Canada Inc., released on September 11, 2017 on behalf of GMOB concluded that vitrification “ranked first in the scoring matrix for stabilization/treatment methods” based on the potential for long-term stability, moderate overall costs, and potential for gold recovery. GMOB is currently in the process of verifying the accuracy of that initial assessment.The GlassLock Processis designed for the sequestration of arsenic in a stable glass form. DSThas successfully demonstrated its Technology at laboratory, pilot and industrial level, wherearsenical material was processed to generate vitrified arsenical glass, containing up to 20%arsenic while meeting the United States Environmental Protection Agency's (EPA) toxicitycharacterization leaching procedure (TCLP, Method 1311)