Engineered (bioretention) media organic material properties and specifications.
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Property Biochar Coir Compost Peat Wood chips
Phosphorus leaching No [1] No to slight [2] Yes [3] No
Phosphorus retention No to slight [4] No [5] No No
Handling concerns Potential explosive concerns in closed space situations; volatile compounds (depending on pyrolysis temperature) [6] Dust [7] None Possibly dust [8]
Soil hydraulic properties Significant improvement [9] Significant improvement [10] Significant improvement [11] Improvement if incorporated [12]
Soil physical properties Significant improvement [13] Moderate improvement [14] Significant improvement [15] Improvement if incorporated [16]
Plant/microbial effects Beneficial but varies with feedstock [17] Beneficial [18] Beneficial if not fresh [19]; [20] Beneficial for fungi
Availability Multiple distributors [21] Widely available [22] Widely available Widely available
Specifications/standards available Limited due to variability with feedstocks [23] Yes [24] Yes [25] Yes for chips used for energy production [26]
Cost
Research needs Feedstocks suitable for stormwater applications Phosphorus fate in stormwater applications Identifying compost-containing media mixes that do not leach phosphorus but provide other benefits Extensive needs since there are limited studies in stormwater applications.
Applications [27] [28] [29] [30]
Chemical properties [31] [32] [33] [34]
Sustainability Sustainable, but has current market constraints [35] Sustainable [36] Sustainable Sustainable
Potential contaminants Minor risk - metals and polycyclic aromatic hydrocarbons (PAHs) [37] Low risk - possible chloride depending on preparation method [38] Low risk; avoid CCA and creosote-treated sources [39]
Test methods Not standardized but International Biochar Initiative widely used [40] Not standardized but multiple methods available [41] [42]; [43] [44]
Effects of aging/Life expectancy Varies with production method [45] Decomposes slowly unless nutrients are added [46] Ages relatively rapidly; aging generally benefits stormwater function by reducing nutrient loss and reducing microbial competition for nutrients [47] Slow to moderate depending on source and application conditions [48]
Notes Characteristics vary with feedstock and pyrolysis temperature Coir must be composted or incorporated with compost, lime, fertilizer, and/or microbes