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Bio fuel ash in a road construction: impact on soil solution chemistry
R T Thurdin1, P A W van Hees, D Bylund
1Department of Natural Sciences, Mid Sweden University, SE-851 70 Sundsvall, Sweden. rikard.thurdin@swepro.se
Waste Management (New York, N.Y.)
|October 11, 2005
Summary
Biofuel ash used in road construction can impact soil chemistry. While some elements increased, others decreased, with cadmium posing a potential groundwater contamination risk.
Area of Science:
- Environmental Science
- Geotechnical Engineering
- Waste Management
Background:
- Increasing ash production from biofuel and municipal solid waste incineration necessitates sustainable disposal solutions.
- Road construction presents a viable application for utilizing ash, mitigating landfill burdens.
- Limited natural resources further drive the need for alternative construction materials like ash.
Purpose of the Study:
- To evaluate the environmental impact of a biofuel ash layer in experimental road construction.
- To monitor changes in soil solution chemistry within and below the ash layer over time.
- To assess potential risks associated with ash application in road infrastructure.
Main Methods:
- Construction of an experimental road with a 40 cm biofuel ash layer on National Road 90, Sweden.
- Collection of soil samples from the ash layer, below the ash layer (two depths), and the ditch on four occasions (2001-2003).
- Analysis of soil solutions for pH, conductivity, dissolved organic carbon (DOC), and total cation/anion concentrations using centrifugation.
Main Results:
- Significant increases in K, SO4, Zn, and Hg concentrations within the ash layer after two years.
- Significant decreases in Se, Mo, and Cd concentrations within the ash layer.
- Elevated pH and increased concentrations of K, SO4, Se, Mo, and Cd below the ash layer; decreased Cu and Hg.
- Cadmium (Cd) identified as a potential groundwater contaminant.
- Calcium (Ca) concentrations indicated ongoing hardening of the ash layer, relevant for road strength and leaching.
Conclusions:
- Biofuel ash application in road construction alters soil solution chemistry both within the ash layer and in underlying soil.
- While some elements mobilize, others are retained or decrease, suggesting complex interactions.
- Careful monitoring for potential groundwater contamination, particularly from elements like cadmium, is crucial.
- The hardening observed in the ash layer suggests potential benefits for road structural integrity and controlled leaching.