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! Benefit !! Effectiveness !! Notes
 
! Benefit !! Effectiveness !! Notes
 
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| Water quality || <font size=6><center>&#9681;</center></font size> || Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
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| Water quality || <font size=4><center>&#9681;</center></font size> || Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
 
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| Water quantity/supply || <font size=4><center>&#9684;</center></font size> || Bioinfiltration helps mimic natural hydrology. Some rate control benefit.
 
| Water quantity/supply || <font size=4><center>&#9684;</center></font size> || Bioinfiltration helps mimic natural hydrology. Some rate control benefit.

Revision as of 01:34, 18 November 2019

Warning: This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.
Benefit Effectiveness Notes
Water quality
Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
Water quantity/supply
Bioinfiltration helps mimic natural hydrology. Some rate control benefit.
Energy savings
Climate resiliency
Provides some rate control. Impacts on carbon sequestration are uncertain.
Air quality
Habitat improvement
Use of perennial vegetation and certain media mixes promote invertebrate communities.
Community livability
Aesthetically pleasing and can be incorporated into a wide range of land use settings.
Health benefits
Economic savings
Generally provide cost savings vs. conventional practices over the life of the practice.
Macroscale benefits
Individual bioretention practices are typically microscale, but multiple bioretention practices, when incorporated into a landscape design, provide macroscale benefits such as wildlife corridors.
Level of benefit: ◯ - none; ; - small; - moderate; - large; - very high




Biochar

Overview and description

Biochar is a charcoal-like substance that’s made by burning organic material from biomass in a controlled process called pyrolysis. Biomass waste materials appropriate for biochar production include crop residues (both field residues and processing residues such as nut shells, fruit pits, bagasse, etc), as well as yard, food and forestry wastes, and animal manures. Clean feedstocks with 10 to 20 percent moisture and high lignin content must be used. Examples are field residues and woody biomass. Using contaminated feedstocks, including feedstocks from railway embankments or contaminated land, can introduce toxins into the soil, drastically increase soil pH and/or inhibit plants from absorbing minerals. The most common contaminants are heavy metals—including cadmium, copper, chromium, lead, zinc, mercury, nickel and arsenic, and Polycyclic Aromatic Hydrocarbons (PAHs).

Biochar is black, highly porous, lightweight, fine-grained and has a large surface area. Approximately 70 percent of its composition is carbon. The remaining percentage consists of nitrogen, hydrogen and oxygen among other elements. Biochar’s chemical composition varies depending on the feedstocks used to make it and methods used to heat it.

Biochar benefits for soil may include the following.

  • enhancing soil structure
  • increasing water retention and aggregation
  • decreasing acidity
  • reducing nitrous oxide emissions
  • improving porosity
  • regulating nitrogen leaching
  • improving electrical conductivity
  • improving microbial properties

Biochar is also found to be beneficial for composting, since it reduces greenhouse gas emissions and prevents the loss of nutrients in the compost material. It also promotes microbial activity, which in turn accelerates the composting process. Plus, it helps reduce the compost’s ammonia losses, bulk density and odor.

Variants

The properties of biochar depend on the feedstock and the conditions under which the biochar is produced.

  • biochar yield and contents of N, hydrogen and oxygen decrease as pyrolysis temperature increased from 400˚C to 700˚C
  • contents of ash, pH and carbon increase with greater pyrolysis temperature
  • The ability of biochars to adsorb NH4+-N is a funtion of cation exchange capacity. For example, adsorption of corn-straw > peanut > > wheat straw and the adsorption amount decreased with higher pyrolysis temperature [1]

Phosphorus retention

NOTE - this is from one study, just inserted here as an example

  • Unwashed biochar: Influent TP was 0.57 mg/L and effluent was 0.3-0.4 mg/L.
  • Washed biochar: Influent TP = 0.82 mg/L and effluent 0.4-0.52 mg/L reduced total phosphorus by 47%
  • Overall total phosphorus removal was 47%, but the influent concentrations were higher than typically found in urban stormwater and the study did not examine phosphorus speciation

Retention of other pollutants

NOTE - this is from one study, just inserted here as an example

  • Reduced TSS by 86%, nitrate by 86%
  • Metal decreases were 18, 19, 65, 75, 17, and 24% respectively for Cd, Cr, Cu, Pb, Ni, and Zn
  • PAH removal was 100% for phenanthrene, 76% for naphthalene, and 0% for benzo(a)pyrene.
  • Bacteria (e coli) removal was 27%

Properties and specifications

biochar speciications
Example of biochar properties

The properties of biochar vary depending on the feedstock and conditions under which the biochar is produced. Example to the right. The information in this table and other similar tables would be extracted and synthesized into a broader discussion and summary of recommended properties for pollutant retention

Accessibility

References