Advanced Characterization and Novel Waste Management for Drill Cuttings from Marcellus Shale Energy Development

摘要

Millions of tons of drill cuttings generated from Marcellus shale gas development are currently disposed of in landfills, buried in-situ, or reused as road fill. This study conducted advanced solids characterization and leaching tests to allow consideration of more diverse disposal environments. Drill cutting samples with different mineralogical traits (e.g., high in pyrite and carbon, or high in calcite) from the lateral portion of Marcellus shale well in WV were studied. Solid characterization (e.g., elemental distribution and mineral composition) and geochemical leaching experiments (e.g., rainfall vs. landfill, wet vs. dry conditions) were conducted to evaluate trace metal mobility under different disposal scenarios. The effects of added drill cuttings on soil quality, plant germination and long-term plant growth were determined in the laboratory and on a building green roof. Results showed that although drill cuttings passed the regulatory short-term leaching tests for landfill disposal, long-term release of Ba in all samples and release of As, Ni, and Sb in high pyrite and low calcite samples were of environmental concern under simulated rainfall conditions. Selected trace metal release (e.g., Ba, V, Mo, Sr and Sb) increased 2-10 times when waste was first air-dried and subsequently underwent simulated rainfall leaching. Residual salt content in drill cuttings inhibited plant seed germination, but plant growth on green roofs in cuttings- amended soil was not inhibited once soluble salts were leached by rainfall. Our characterization better informs waste managers of the different geochemical factors that control trace metal release from drill cuttings and improves the ability to assess proposed methods of solid waste characterization and handling. Novel commercial uses, such as the addition of drill cuttings to green roof soils to offset costs, can be considered if the long-term safety of the material can be demonstrated.