01 · Direct answer.
Loose coir pith is sold by volume, in 100 L bags, and the weight of a bag changes with the moisture and particle size of the material. In compressed blocks, the industry reference for fine grade is 15 liters per kg after hydration, with 5:1 compression for blocks and 4:1 for slabs.[1] Carve ships coir pith loose, sold by volume; compressed formats are set per export programme.[4]
| Format | Yield | Basis |
|---|---|---|
| Compressed block 5:1, fine grade, hydrated | 15 L/kg | Romero 2025 |
| Compressed block, medium grade, hydrated | 14 L/kg | Romero 2025 |
| Compressed block, coarse grade (chips), hydrated | 13 L/kg | Romero 2025 |
Liters per kg are direct arithmetic on the declared density. See also Coir Pith.
02 · Why loose pith and blocks yield differently.
The two numbers describe different states of the same material. A 100 L bag is already at loose volume, at shipping moisture. A block has been compressed and only returns to working volume when it takes up water:
- Blocks are compressed 5:1 and slabs (slabs and grow bags) 4:1.[1]
- Before compression the material must be dry, below 20 % moisture by the industry reference.[1][4]
- The slower the hydration, the larger the expansion volume. In the Netherlands, blocks are sometimes hydrated with hot water, which speeds the process and keeps calcium and magnesium in solution.[1]
Carve ships coir pith in 100 L woven bags with loose fill; compressed formats are set per export programme.[4] The 15 L/kg block figure is the market reference for comparing formats, not a specification of the loose bag.
03 · Expansion and durability by particle size.
Romero groups coir into three particle sizes. The fine grade, which corresponds to coir pith, expands the most and holds the most water. It also has the shortest life in continuous cropping, because a substrate's durability is set by its aeration:[1]
| Particle size | Expansion | Life in continuous cropping |
|---|---|---|
| Fine (coir pith) | 15 L/kg | 1.5-2 years |
| Medium | 14 L/kg | 4-7 years |
| Coarse (chips) | 13 L/kg | 8-10 years |
Romero 2025.
04 · What changes the weight of a 100 L bag.
- Moisture: each extra percentage point of moisture raises density by about 1.07 %, according to the Manickam and Suresh regression. It is a weak effect.[3]
- Particle size: halving the mean particle size raises density by about 26 %. It is the strong effect, 3 to 4 times larger than moisture.[3]
- This is why a "finer" pith weighs more per liter. Carve's ~4.1 mm screen keeps the material relatively coarse, and particles below 0.5 mm are undesirable because they clog aeration pores.[1][4]
- EMBRAPA records bulk density below 0.09 g/cm³ (90 kg/m³) for dry-husk coir pith, at a sun-drying moisture of 15 to 20 %.[2]
Because Carve sells loose pith by volume, moisture is neutral for the buyer: a wetter bag weighs more without holding more substrate. When a quotation is per tonne, convert it to liters with a measured density and state whether moisture is on a wet or dry basis. The arithmetic of a full load is in Coir pith per truck.
05 · How to check the yield on arrival.
- Weigh a bag on any scale and compare with the weight declared on the label.[5]
- Measure density yourself: fill a container of known volume, letting the pith fall freely from about 15 cm without tapping or pressing, level the top with a ruler and weigh. Weight in grams divided by volume in liters is density in g/L, the same number as kg/m³.[5]
- Record the moisture at the time of the test: density without moisture says nothing.[5]
For blocks, the hydration-yield test and the other contract items are in the specification checklist. Company data: Company facts.
06 · Frequently asked questions.
How much does a 100 L bag of coir pith weigh?
The weight varies with the moisture and particle size of the material, so Carve sells loose pith by volume, in 100 L bags.
How many liters does 1 kg of coir pith make?
As a compressed block, once hydrated, the industry reference for fine grade is 15 liters per kg, according to Adalberto Romero. The two numbers describe different states of the same material: one is dry and loose, the other was compressed and then expanded with water.
How many liters does a 5 kg coir pith block make?
About 75 liters, applying the 15 L/kg reference for fine grade cited by Romero. Blocks are compressed 5:1 and slabs 4:1, and the final volume depends on how the block is hydrated: slower hydration gives more volume.
Is coir pith bought by weight or by volume?
Carve sells loose coir pith by volume, in 100 L bags, because volume is the unit that is neutral to moisture: a wetter bag weighs more without holding more substrate. Romero notes that the industry measures substrate in liters but often sells it by the kilogram because freight is charged by weight. When comparing quotations, convert everything to liters using the declared density of the lot.
Why does slow hydration of a block give more volume?
Because the expansion of compressed coir depends on hydration time: the slower the hydration, the larger the final volume, according to Romero. He notes that in the Netherlands blocks are sometimes hydrated with hot water, which speeds the process and keeps calcium and magnesium in solution.
07 · Sources.
- Ing. Adalberto Romero webinar (Science Fetti / El Semillero, Colombia, 2025): expansion of 15 / 14 / 13 L/kg by particle size, compression 5:1 for blocks and 4:1 for slabs before compression, slow hydration yields more, hot water in the Netherlands, particles below 0.5 mm undesirable, life by particle size.
- EMBRAPA Tabuleiros Costeiros, Comunicado Técnico 226 (COT-226-19): bulk density below 0.09 g/cm³, water holding 8 to 10 times dry weight, sun-drying moisture 15 to 20 %.
- Manickam, T. and Suresh, K. (2011), International Journal of Engineering Science and Technology 3(4): regression of coir pith bulk density against moisture and particle size.
- Carve public specification: Coir Pith and Import Coir from Brazil.
- Carve bench procedure for bulk density: container of known volume, free fall, levelling, weighing, moisture recorded.