Coir and applications of coir in stormwater management
This page provides information on coir. While providing extensive information on coir, there is a section focused specifically on stormwater applications for coir.
Coconut (Cocus nucifera L.) pith or coir, the mesocarp of the fruit, is a waste product that has potential benefits in growth media. Coir dust is peat-like and consists of short fibres (< 2 cm). Coir has a large surface area per unit volume, is hydrophilic, and therefore has the ability to absorb water.
There are three basic types of coir material.
Coir production involves separating the husk from the shelled nut and soaking the husk in water. The fibers are then separated from the pith and the resulting material is screened to create a uniform particle size. A dust is created during this process and the dust may be air dried and packaged.
Coir benefits may include but are not limited to the following.
This section includes a discussion of chemical and physical properties of coir, and potential contaminants in coir,
The physical and chemical properties of coir vary with particle size. Noguera et al. (2003) varied particle size of coir dust, studying the properties of coir passing through sieves 0.125, 0.25, 0.5, 1.0, and 2.0 mm in diameter. They observed the following.
Based on generally recommended plant specifications, the researchers concluded the 0.25-0.5 mm size appears most suited for plant growth, with some addition of larger particles recommended. Abad et al. (2005) similarly concluded that a mix of particle sizes is likely to be optimum for use of coir as a plant medium.
Another factor affecting chemical properties of coir are the conditions under which it is prepared. In particular, if soaking in a saline solution is used in the preparation of coir, concentrations of potassium, sodium, chloride can be very high and may interfere with plant growth.
The following table summarizes data from the literature on physical and chemical properties of coir. Some general conclusions include the following.
Chemical and physical properties of coir.
Link to this table
Property | Range found in literature1 | Median value from literature |
---|---|---|
Total phosphorus (% dry wt) | 0.036 - 0.41 | 0.036 |
Total nitrogen (% dry wt) | 0.24 - 0.5 | 0.45 |
Total potassium (% dry wt) | 0.4 - 2.39 | 0.819 |
Total carbon (%) | 42 - 49 | 47.1 |
Total hydrogen (%) | 4.4 | |
pH | 4.9 - 6.9 | 5.9 |
Cation exchange capacity (cmol/kg) | 31.7 - 130 | 50 |
Electrical conductivity (ds/m) | 39 - 2900 | 582 |
Total calcium (%) | 0.18-0.47 | 0.40 |
Total magnesium (%) | 0.11-0.47 | 0.36 |
Total copper (mg/kg) | 3.1-10.3 | 4.2 |
Total zinc (mg/kg) | 4.0-9.8 | 7.5 |
Total manganese (mg/kg) | 12.5-92 | 17 |
Bulk density (g/cm3) | 0.025 - 0.132 | 0.06 |
Water holding capacity (% by wt) | 137 - 1100 | 566 |
Total pore space (%) | 85.5 - 98.3 | 95.2 |
Primary references for this data: