01 · Direct answer.
Loose, at shipping moisture (18 % at most), Carve's coir pith has a bulk density of about 90 to 95 kg/m³. So 1 kg fills about 10.5 to 11 liters, and a 100 L bag weighs about 9 to 9.5 kg.[4] 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's 5 kg export block is guaranteed at a minimum of 13 L/kg.[4]
| Format | Yield | Basis |
|---|---|---|
| Loose coir pith, 100 L bag | ~10.5-11 L/kg · bag ~9-9.5 kg | Bulk density ~90-95 kg/m³ at 15-20 % moisture, Carve data sheet and EMBRAPA |
| 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 |
| Carve 5 kg export block, guaranteed minimum | ≥ 13 L/kg · ≥ 65 L per block | Carve public specification |
Bag values come from the density declared on the Coir Pith data sheet; the actual value of each lot is printed on the bag. Liters per kg are direct arithmetic on the declared density.
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. Carve works to an 18 % limit.[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, and in 5 kg compressed blocks for export on committed volume.[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. Water holding of dry-husk coir pith is 8 to 10 times its dry weight according to EMBRAPA; Carve's data sheet guarantees 5 times dry weight, about 500 ml/L.[2][4]
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 the lot's declared 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.
- Read the label: each bag carries its net weight and the lot's density, and the QR opens the lot report with the measured moisture. See Coir pith lot report (COA).[4]
- 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?
About 9 to 9.5 kg, at a loose bulk density of 90 to 95 kg/m³ and 15-20 % moisture. The actual weight varies with the moisture and particle size of the lot, which is why the measured density of the lot is printed on the bag and the net weight is on the label.
How many liters does 1 kg of coir pith make?
Loose, at shipping moisture, 1 kg fills about 10.5 to 11 liters, the inverse of a density of 90 to 95 kg/m³. 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. Carve's 5 kg export block is guaranteed at a minimum of 13 L/kg, so at least 65 liters. 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, moisture below 20 % 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 (density ~90-95 kg/m³ loose, maximum moisture 18 %, ~4.1 mm screen, water holding 5 times dry weight, ~500 ml/L, 100 L bag with lot QR) and Import Coir from Brazil (5 kg block, ≥ 13 L/kg, ≥ 65 L per block).
- Carve bench procedure for bulk density: container of known volume, free fall, levelling, weighing, moisture recorded.