How BiocharFilters Stormwater
Understanding the science behind biochar's exceptional performance in stormwater management systems.
Cross-section showing biochar's porous structure trapping contaminants at the microscopic level
Physical Properties
High Surface Area
300-500
m²/g surface area
Biochar's highly porous structure provides extensive sites for contaminant adsorption—comparable to activated carbon but at a fraction of the cost.
Porous Structure
60-80%
porosity by volume
Interconnected macro- and micropores create pathways for water infiltration while physically trapping pollutant particles and providing habitat for beneficial microbes.
Stable Carbon
1000+
years stability
Biochar's aromatic carbon structure resists decomposition, providing long-term performance without the need for frequent replacement.
Three Filtration Mechanisms
Biochar removes stormwater contaminants through complementary physical, chemical, and biological processes.
Physical Adsorption
Contaminant molecules bind to biochar's vast internal surface area through van der Waals forces and electrostatic attraction. Heavy metals (copper, zinc, lead) and hydrocarbons are particularly susceptible to this mechanism.
Performance Data:
- • Copper: >95% removal
- • Zinc: >97% removal
- • Lead: 80-90% removal
Chemical Binding
Biochar's surface functional groups (carboxyl, hydroxyl, phenolic) form covalent bonds with metal ions and organic pollutants. This creates stable complexes that prevent contaminant mobility and bioavailability.
Key Benefits:
- • Irreversible binding
- • pH buffering capacity
- • Nutrient retention (N, P)
Microbial Degradation
Biochar's porous structure provides protected habitat for beneficial bacteria that degrade organic contaminants. Enhanced microbial activity accelerates the breakdown of hydrocarbons and blocks pathogen movement (E. coli, Salmonella).
Biological Action:
- • Increased microbial biomass
- • Pathogen filtration
- • Organic matter breakdown
Performance vs. Traditional Media
Biochar Media
- Cost: $200-400/ton (bulk)
- Metal Removal: 90-97%
- Lifespan: 10-20+ years
- Water Holding: 6x its weight
- Carbon Impact: Net negative (sequestration)
Activated Carbon
- Cost: $500-1200/ton
- Metal Removal: 85-95%
- Lifespan: 3-5 years (requires replacement)
- Water Holding: 2-3x its weight
- Carbon Impact: Energy-intensive production