Overview

Biochar sits within a family of filtration and polishing media including sand, gravel, reedbeds, geotextiles, membranes and constructed wetlands. This article compares biochar with these alternatives and explains where each fits into a treatment train.

Sand and gravel

Pros: Cheap, widely available.

Cons: Poor adsorption of dissolved pollutants; easily blinded; minimal microbial structure.

Fit: Good for bulk sediment control, not polishing.

Reedbeds and constructed wetlands

Pros: Excellent for primary treatment; strong biological processes.

Cons: Large land footprint; seasonal performance; limited fine polishing.

Fit: Best as primary stage; biochar excels directly downstream.

Membranes and fine filtration

Pros: High removal efficiency; predictable performance.

Cons: Expensive; prone to fouling; high-pressure or power requirements.

Fit: Useful where regulatory limits are strict; biochar as a pre-polish reduces fouling.

Geotextile socks and mats

Pros: Simple and deployable.

Cons: Rapid clogging if used as primary filtration; external biofilm/sediment crust forms.

Fit: Useful for flow diversion or baffle functions; biochar performs better inside deliberately permeable housings.