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
Soil hydraulic properties Significant improvement [8] Significant improvement [9] Significant improvement [10] Improvement if incorporated [11]
Soil physical properties Significant improvement [12] Moderate improvement [13] Significant improvement [14] Improvement if incorporated [15]
Plant/microbial effects Beneficial but varies with feedstock [16] Beneficial [17] Beneficial if not fresh [18]; [19] Beneficial for fungi
Availability Multiple distributors [20] Widely available [21] Widely available Widely available
Specifications/standards available Limited due to variability with feedstocks [22] Yes [23] Yes [24] Yes for chips used for energy production [25]
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 Limited studies in stormwater applications
Applications [26] [27] [28]
Chemical properties [29] [30] [31] [32]
Sustainability Sustainable, but has current market constraints [33] Sustainable [34] Sustainable Sustainable
Potential contaminants Minor risk - metals and polycyclic aromatic hydrocarbons (PAHs) [35] Low risk - possible chloride depending on preparation method [36] Low risk; avoid CCA and creosote-treated sources [37]
Test methods Not standardized but International Biochar Initiative widely used [38] Not standardized but multiple methods available [39] [40]; [41]
Effects of aging/Life expectancy Varies with production method [42] Decomposes slowly unless nutrients are added [43] Ages relatively rapidly; aging generally benefits stormwater function by reducing nutrient loss and reducing microbial competition for nutrients [44] Slow to moderate depending on source [45]
Notes Characteristics vary with feedstock and pyrolysis temperature Coir must be composted or incorporated with compost, lime, fertilizer, and/or microbes