The short answer: there is no drop-in replacement for coco coir. Wood fibre is the closest organic substitute and the one the industry is investing in, but it holds about half the water and ties up nitrogen. Bark and perlite add air, vermiculite and compost add water and nutrients, rice hulls and biochar are cheap fillers with limits. Most growers who move away from pure coir end up with a blend, not a swap. Here is how the options compare on the numbers that matter, and what to test before you change.
Key facts
- Coir holds roughly 40% water by volume with 13–28% air-filled porosity; wood fibre holds 20–25% water with 30–35% air (Hort Innovation / RMCG, 2022).
- Wood fibre immobilises nitrogen: Klasmann-Deilmann quotes a constant 100–150 mg/L N fixation for its GreenFibre and adds a nitrogen store to the mix.
- Coir compresses about 6:1 for shipping; wood fibre only 1.4:1. In Australia, shipping was estimated at up to half of growers' coir cost (Hort Innovation, 2022).
- Perlite is reusable after steaming; vermiculite is not; coir and bark are usually composted after one to four crops (Jackson, Fonteno and Whipker, 2018).
Why growers look for an alternative
The Australian berry-industry review by Hort Innovation and RMCG (2022) sums up the pressures. The delivered price of coir had doubled in three to four years; order-to-farm lead time had stretched from 9–10 weeks in 2019 to 6–7 months in 2022; and growers put up to 50% of their coir cost down to shipping. Those figures are Australian, but the drivers (container freight, a concentrated origin in India and Sri Lanka, competition between buyers) apply to every importer. Peat-free policy in Europe adds a push toward regional raw materials; see our peat-free growing media guide.
None of this says coir performs badly. The same review kept coir as the reference because it "produces good results and it is considered the most environmentally sustainable option". The question is what else can do the job, and at what cost in management.
Comparison table: coir and nine alternatives
Figures come from the sources listed at the end. Physical values shift with particle size, compression and test method, so read them as ranges. CEC is cation exchange capacity in meq/100 g; "N drawdown" is nitrogen immobilised by microbes feeding on the material.
| Medium | Air-filled porosity | Water holding (vol.) | pH as supplied | CEC | N drawdown | Re-use | Cost tier | Availability | Sustainability |
|---|---|---|---|---|---|---|---|---|---|
| Coco coir (pith) | 13–28% | ~40% | 4.8–6.8 (Jackson); 6.0–6.8 (Hort Innovation) | ~50 | Low | 3–4 years in berries, then compost | Mid | Imported; lead times vary | Renewable by-product; shipping emissions |
| Sphagnum peat | 18–25% | ~40% | 3.8–4.2 | 150–250 | Very low | Single crop | Mid | Restricted in UK/EU retail | Non-renewable; see coir vs peat |
| Wood fibre | 30–35% | 20–25% | 5.0–7.5 | Lower than coir | Medium (100–150 mg/L) | Unknown; compostable | Low–mid ex works, freight-sensitive | Growing in EU, US, Australia | Renewable; poor compression |
| Pine bark (aged) | ~22% | Lower than peat | 4.0–4.5 | ~50 | Medium–high unless composted | Compost after use | Low | Regional; price rising | Forestry by-product |
| Perlite | ~30% | Low | 7.0–7.5 | ~3 | None | Yes, after steaming | Mid–high | Mined, ~70% from Greece/Turkey | Non-renewable; landfill; dust |
| Vermiculite | Lower than perlite | High | 7.0–7.5 | High | None | No (heat destroys it) | High | Mined | Non-renewable |
| Rockwool | ≥18% | High | 7.0–8.5 | None | None | Steam-sterilise slabs | High | Industrial | Landfill unless recycled |
| Parboiled rice hulls | High, similar to perlite at 20% | Low–moderate | Slightly acidic | Low | None (parboiled) | 1–2 crops (salt build-up) | Low | Rice regions | Renewable by-product |
| Green compost | Variable | High | Neutral to alkaline | High | Variable | No | Low | Local | Recycled waste; variable quality |
| Biochar | Falls as rate rises | Falls as rate rises | High (manure biochar 9.2–12.4) | Raises CEC | Low | Stable | High | Limited | Carbon storage; feedstock-dependent |
Two caveats. Premier Tech Horticulture gives coir air-filled porosity as about 13% and Hort Innovation as 13–28%; the gap is mostly the share of fibre and chips in the sample. Coir pH is quoted as 4.8–6.8 by NC State's Jackson, Fonteno and Whipker and 6.0–6.8 by Hort Innovation, because it depends on source and washing.
Each alternative in brief
Wood fibre
Made by thermal and mechanical defibration of wood chips, usually pine, at temperatures that leave it free of pathogens and weed seed. It is the alternative substrate companies back most: the Australian review counted Dutch, US and German producers, and Klasmann-Deilmann runs six wood fibre plants in Europe.
Where it beats coir: air. At 30–35% air-filled porosity it drains faster and the surface dries sooner, which cuts algae and fungus gnats. Where it loses: water and nitrogen. Water holding is 20–25% against coir's 40%, so irrigation must be more frequent in shorter pulses. Microbes colonising the fibre tie up nitrogen; Klasmann-Deilmann quotes 100–150 mg/L and adds a nitrogen reserve to its mixes. Harris, Dickson, Fisher, Jackson and Poleatewich (HortTechnology, 2019) found no statistical evidence of immobilisation in peat with 30% pine wood fibre, but warned that higher shares may need more fertiliser and irrigation changes. Jackson (2018) also saw sulphur deficiency in near-100% pine wood, fixed with fine gypsum.
Logistics decide the price. Wood fibre compresses only about 1.4:1, so it competes only when the plant is near the farm: Hort Innovation quoted A$130/m³ ex works plus about A$50 freight within the same state, against A$180–220/m³ for delivered coir. A 25% wood fibre / 75% coir mix gave no yield difference from pure coir in New South Wales raspberry and blueberry trials.
Right choice when: a regional producer exists, your crop tolerates frequent irrigation, and you monitor EC and adjust nitrogen.
Bark
Aged pine bark is the backbone of nursery substrates in the south-eastern United States. Premier Tech gives it 80% total porosity, about 22% air-filled porosity, a bulk density of 0.2 g/cm³ (more than double coir's 0.08) and CEC around 50 meq/100 g. At pH 4.0–4.5 it needs lime or a higher-pH feed, and bark that is not composted or heat-treated draws down nitrogen. It is cheap, but Hort Innovation notes it is "becoming more expensive and greater difficulty sourcing" as mulch, nursery and energy buyers compete for it.
Right choice when: you need a heavy, stable, free-draining base for larger containers or outdoor nursery stock.
Perlite
Volcanic glass popped at 800–1,100 °C: about 75% total porosity, 30% air-filled porosity, pH 7.0–7.5, CEC near 3. It holds three to four times its own weight in water, which is little by volume because it is so light. It is dusty, floats and blocks drains in recirculating systems, and roughly 70% of supply is mined near the Aegean coast of Greece and Turkey. Jackson, Fonteno and Whipker call it the second most expensive component in most mixes. Its strengths are stability and re-use after steaming; its weakness at end of life is that any mix containing perlite is harder to compost.
Right choice when: you want an inert aggregate to open up a coir or peat mix, or a long-lived medium for recirculating hydroponics.
Vermiculite
Expanded mica. Holds three to four times its weight in water, pH 7.0–7.5, supplies some magnesium and potassium, high CEC. It cannot be steam-sterilised and it compacts over time. Its cost has led many blenders to drop it from high-percentage use.
Right choice when: germination and cuttings, or to add water and nutrient buffering to a very open mix. Not a bulk coir replacement.
Rockwool
Covered in detail in our coco coir vs rockwool comparison. In short: high water holding with at least 18% air space, pH 7.0–8.5 so the feed must be acidified, no CEC, sterile, re-usable after steaming, landfill-bound unless a recycling route exists. It is the main alternative in high-tech hydroponics, not in potting mixes.
Parboiled rice hulls
Steamed during parboiling, so they arrive sterile and free of viable weed seed. According to Jarahian (Greenhouse Management & Production, 2010) they match perlite for plant growth at up to 30% of a mix, cause no significant nitrogen tie-up and cost up to US$0.50 less per cubic foot than perlite depending on freight. Purdue University trials reported at ASHS meetings (2015, 2019) found rice hulls raised total porosity and air space in peat, lowered water holding, and gave lower pH and EC than the control. Drawbacks: fines from a poor-quality base can fill the canoe-shaped hulls and undo the drainage gain; the surface looks dry when the root zone is not; CEC is low; and the Australian review flagged salt build-up and high manganese, with replacement after one or two crops.
Right choice when: you grow in a rice-producing region and your base mix has few fines.
Green compost
Adds nutrients, water holding and CEC at low cost. Its problem is consistency: Jackson, Fonteno and Whipker list feedstock, pile size, turning, air and water supply, composting time and pile cover as factors that change the product batch to batch. Compost tends to run neutral to alkaline with higher EC, higher bulk density and finer particles than coir. We found no well-sourced universal maximum rate, so treat a supplier's figure as the starting point for your own trial.
Right choice when: blending low-cost peat-free retail or nursery mixes and you test each batch for pH, EC and maturity.
Biochar
Pyrolysed plant material: stable, porous, and it raises pH, EC and CEC of whatever it joins. Rathnayak and colleagues (2019) found bark biochar blended with peat at 1:3, 1:1 and 3:1 improved germination and growth of cress, lettuce and tomato over peat alone or biochar alone. Feedstock matters: poultry-manure biochar tested by Wystalska et al. (2023) had pH 9.2–12.4, enough to act as lime. Air-filled porosity and water holding fall as the share rises, so it is an amendment at modest rates, not a bulk medium.
When coir is still the right choice
Coir wins on the combination of high water holding with usable air, a pH that needs little adjustment, moderate CEC, low bulk density (about 80 kg/m³), 6:1 compression, three to four years of structural life in berry crops, and a compostable end of life. In Hort Innovation's gross-margin model, a berry farm switching to locally made wood fibre saw a negligible change (64.4% vs 64.5%), and only because freight on the wood fibre was short. If you import both, coir's compression usually gives it the transport advantage. Coir's weak point is raw-material variability: EC and buffering status must be checked on each lot, a topic covered in our pH and EC and buffering articles.
Blends: how the alternatives combine with coir
In practice the alternatives are used with coir more often than instead of it. The most thoroughly documented pairing is bark and coir. Basiri Jahromi, Fulcher, Walker and Altland (Water, 2020) measured pine bark amended with coir by volume:
| Coir in pine bark | Total porosity | Air space | Container capacity | Bulk density (g/cm³) |
|---|---|---|---|---|
| 0% | 69% | 30% | 39% | 0.18 |
| 10% | 79% | 35% | 44% | 0.18 |
| 25% | 77% | 29% | 48% | 0.16 |
| 40% | 77% | 29% | 48% | 0.14 |
| 65% | 81% | 21% | 59% | 0.11 |
Source: Basiri Jahromi et al., 2020. Container capacity is water held after free drainage.
Pure bark fell below the recommended 45–65% container capacity; more than 10% coir brought it into range, and 65% coir gave the highest photosynthetic rate in hydrangea while air space stayed inside the 10–30% guideline. That is the general pattern: coir supplies water buffering, the partner supplies air or weight. Other pairings with published or grower-reported support:
- Coir + wood fibre (75:25): no yield difference from pure coir in Australian berry trials; Hort Innovation recommends replicated trials of 50:50 and 75:25.
- Coir + perlite or vermiculite: the standard propagation and container recipes; ratios by crop are in our article on coco coir, perlite and vermiculite mixes.
- Coir pith + coconut husk chips: air from the same plant, no imported aggregate.
- Coir + rice hulls: a renewable stand-in for coir + perlite where hulls are local; keep fines low.
At scale, grading and ratio matter more than the ingredient list. Alongside our standard coco peat products we produce custom blends of pith, chips and fibre to a specified grading.
Supply and price: what moves each material
Coir prices track container freight, the monsoon and drying season, and export rules in origin countries. Wood fibre tracks regional timber supply, defibration energy and distance to farm. Bark competes with mulch, nursery and bioenergy demand. Perlite tracks mining output in Greece and Turkey and the energy used to expand it. Rice hulls follow the harvest and animal-bedding demand. Compost is a quality risk more than a price risk. The lesson of 2020–22 is that no material is immune, and that growers with a qualified second supplier or a tested second blend fared better than those planning a full switch under pressure.
What to test when switching medium
- Physical properties of the actual batch, expanded and at your particle grade. Targets: 10–30% air space, 45–65% container capacity, 50–85% total porosity (nursery guidelines cited by Basiri Jahromi et al.).
- pH and EC of a saturated extract. Adjust lime or feed acid before planting, not after.
- Nitrogen drawdown. For wood fibre, bark or compost, run a pot trial and check pour-through EC and nitrate weekly for four to six weeks; immobilisation peaks in the first two to three weeks.
- Irrigation frequency. Weigh pots daily for a week. Wood fibre and rice hulls need shorter, more frequent cycles; vermiculite and compost need fewer.
- Shrinkage. Photograph fill height at planting and at eight weeks.
- Rewetting. Dry a sample hard and re-irrigate. Coir rewets easily; peat, bark and some wood fibres do not.
- End of life. Confirm your composter accepts the spent mix; a perlite or rockwool fraction can disqualify it.
- Economics including yield. Hort Innovation's threshold analysis showed a 2% drop in marketable yield outweighs a large substrate saving. Price the trial on yield and labour, not cost per cubic metre.
If you are weighing a change and want a coir component specified to a particular grading or blend, tell us what you are testing and we will match a product to it.
FAQ
What is the closest alternative to coco coir?
Wood fibre is the nearest organic substitute in supply and investment, but it is not identical. It holds about half as much water (20–25% against roughly 40% by volume), has more air (30–35%), and ties up nitrogen unless the mix carries a nitrogen reserve. Most trials use it blended with coir or peat at 25–50% rather than alone.
Can I replace coco coir with perlite?
Not one for one. Perlite is an inert aggregate with about 30% air-filled porosity, little water holding by volume and almost no cation exchange capacity, so plants in pure perlite depend on frequent feeding. It works well as 20–40% of a coir or peat mix, or alone in recirculating hydroponics with constant nutrient supply.
Is wood fibre cheaper than coco coir?
Ex works it often is: the Australian Hort Innovation study quoted about A$130 per cubic metre for wood fibre against A$180–220 for delivered coir. But wood fibre compresses only 1.4 to 1 while coir compresses about 6 to 1, so wood fibre's freight cost per usable cubic metre rises fast with distance. It is competitive when produced near the farm.
Does bark cause nitrogen deficiency like wood fibre?
Fresh or lightly aged bark can. Properly composted or heat-treated bark immobilises much less. Aged pine bark is also acidic (pH 4.0–4.5) and needs lime or a higher-pH feed. Check pour-through EC and nitrate weekly during the first month to see whether your batch is drawing nitrogen down.
Are rice hulls a good substitute for perlite in a coir mix?
Parboiled rice hulls give similar drainage to perlite at up to about 30% of the mix, arrive sterile and weed-free, and are renewable and usually cheaper where rice is grown. They hold less water, have low cation exchange capacity and can accumulate salts, so they suit short-rotation crops better than multi-year plantings.
Which growing medium can be re-used the most?
Perlite and rockwool can be steam-sterilised and re-used several times. Vermiculite cannot be steamed because the heat destroys its structure. Coir is used for three to four years in berry crops before it loses structure, and bark, wood fibre and coir are compostable afterwards. Mixes containing perlite are harder to compost.
How much compost can I put in a potting mix?
There is no single safe percentage because compost varies so much in pH, salts and particle size between batches. Test each batch for pH, EC and maturity, start at a modest share in a trial, and raise it only if plants and drainage perform. High compost shares usually reduce air space and raise EC.
Does biochar replace coco coir or peat?
No. Biochar is an amendment, not a bulk medium. It raises pH, EC and cation exchange capacity and stores carbon, but air-filled porosity and water holding fall as its share increases, and some feedstocks such as poultry manure are strongly alkaline. Blends of biochar with peat or bark have improved growth in trials; pure biochar has not.
Sources
- Hort Innovation / RM Consulting Group (RMCG): Alternative growing media for hydroponic berry production, a desktop review, project RB21002, final report and "Coir and its alternatives" booklet (2022)
- Jackson, B. E., Fonteno, W. and Whipker, B. E.: Media Matters, Cannabis Business Times (November 2018)
- Jackson, B. E.: Challenges and Considerations of Using Wood Substrates: Biological Properties, Greenhouse Grower (2018)
- Klasmann-Deilmann: GreenFibre wood fibre technical page (accessed 2026)
- Harris, C. N., Dickson, R. W., Fisher, P. R., Jackson, B. E. and Poleatewich, A. M.: Assessing nitrogen immobilization in peat substrates amended with pine wood fiber, HortTechnology (2019)
- Basiri Jahromi, N., Fulcher, A., Walker, F. and Altland, J.: Optimizing Substrate Available Water and Coir Amendment Rate in Pine Bark Substrates, Water 12(2):362 (2020)
- Premier Tech Horticulture: How to optimize your growing media (2014) and Fundamentals of growing media (2016), republished by HortiDaily
- Jarahian, S.: Consider rice hulls as a media component, Greenhouse Management & Production 30(12) (2010)
- Purdue University, Department of Horticulture and Landscape Architecture: rice hull substrate studies presented at ASHS annual conferences (2015, 2019)
- Rathnayak, D., Creber, H., Van Poucke, R., Mašek, O., Sohi, S., Meers, E. and Ronsse, F.: Characterization of tree bark biochar and evaluation of its potential to use in horticultural growing mediums, Bio-Char II conference (2019)
- Wystalska, K., Malińska, K., Sobik-Szołtysek, J., Dróżdż, D. and Meers, E.: Properties of Poultry-Manure-Derived Biochar for Peat Substitution in Growing Media, Materials 16(19):6392 (2023)
- Apex Publishers: Growing Media for Greenhouse Crops, Chapter 12, Ingredients used in formulating media (undated)