Cement kiln dust (CKD) and digestate for improving soil quality and crop yield and reducing greenhouse gas emissions

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Industrial processes can produce a large quantity of by-products that are often treated as wastes. The disposal of such by-products in landfills can be costly and is environmentally unfriendly. Many industrial waste types can be recycled or beneficially used. Cement kiln dust (CKD) from the cement industry and digestate from the biogas production process are two such industrial by-products. The Canadian cement industry generates about 670,000 tonnes of CKD annually. The CKD contains nutrients such as calcium (Ca), magnesium and sulfur and is a material with an alkaline pH and can be used to neutralize the pH of acidic soils. The digestate has high soluble organic matter and nitrogen (N) content, and when it is applied to the soil, nitrous oxide emissions may increase. However, there has been no study on the soil fertility or agronomic benefits of the application of CKD alone or in combination with digestate in croplands in Canada. The research team will collaborate with the industrial partner (Norstar Industries Ltd) to develop a project to study the effect of CKD, digestate and a humic acid product on soil properties, greenhouse gas emissions, and crop yield and quality in a wheat-canola rotation in a Gray Luvisol that has low soil pH. Soil properties to be assessed include soil bulk density, total N, phosphorus (P) and potassium (K) contents, available NPK and Ca, pH and electrical conductivity, total carbon (C, both organic and inorganic, if any) and N, and the light fraction of organic C, and dissolved organic C and N. The effect of the treatments on extractable heavy metal contents in the soil and crop will also be assessed to evaluate the potential risk of heavy metal contamination. This four-year study will train one PhD student, two part-time postdoctoral fellows and four undergraduate research assistants. The research team and the partner organization will work together to disseminate the research findings to farmers across the country, in western Canada in particular, and provide policy input for the proper management of CKD and digestate.