Accelerated aggregation in mine waste deposits by co-pyrolysis of tailings and organic feedstocks

Mineral (neutral mine tailings, quartz sand) and organic (sawdust, hay) mixes were subjected to a slow co-pyrolysis process (400~C, 30 minutes) to produce biochar-mineral mixtures with the intent of accelerating granular structure formation which is beneficial to the establishment of vegetation. Resulting products were examined for pH, CEC, water holding capacity and IR spectra, and compared to non-pyrolized samples. The changes in these soil properties with temperature of pyrolysis (200~C, 300~C and 400~C) were also examined. Differences were found in samples resulting from organic type, mineral type, temperature of pyrolysis, and the pyrolysis process. Aggregates formed in all samples containing organics. Aggregates were examined by scanning electron microscope and thin section microscopy revealing mineral particles embedded in an organic matrix. The results suggest a role of phase changes of carbon products (into bio-oil and bio-gas) during pyrolysis in the closed reactor system, rather than a biochar coating creating organo-mineral complexes.