Long-term developments in residues from the processing of alum shale and possible remedies

In large parts of the world, the gas market has changed dramatically due to the fracking of rock, including shale. It is also anticipated that significant changes will take place in the oil market due to the rapid introduction of the processing of shale for the purpose of oil and gas generation. Many fear that there will be substantial consequences for the environment, especially in the long term. The purpose of the present paper is to share some experiences from related historical activities in Sweden where alum shale has been used for oil extraction, burning of lime, alum production and uranium beneficiation. Legacies exist in terms of shale ash and fines as well as residues from the leaching of uranium, in quantities of a total of tens of millions of tonnes, and at various stages of remediation. The long-term integrity of these residues is analyzed with regard to the possibility of development of acid mine drainage, and in view of the low Ca and high S content. It is found that such developments cannot be excluded for the cases in which the alum shale had not been (properly) combusted. Waste materials having appropriately high pH acid buffering capacities to inhibit acidification are identified together with injection as a promising method of application. The need for mixing on a local scale is discussed together with the possible influence of the injection of slurry on ongoing fires. It is found that further knowledge is needed on a number of issues.Godkänd; 2014; 20140424 (andbra