How does wood fiber perform as a peat alternative in substrates?
Wood fibre performs well as a peat alternative in growing media, particularly when blended with peat at rates of 20 to 50% by volume. It improves aeration and drainage, reduces compaction, and lowers dependence on peat as a raw material. However, it also introduces specific management requirements around irrigation, nitrogen nutrition, and pH that growers must address to achieve reliable crop results.
The performance of wood fibre in a substrate depends heavily on how it is processed, which species it is derived from, and how it is combined with other components. Professional growers working with substrate-based greenhouse cultivation will find that wood fibre is not a straightforward one-to-one replacement for peat, but a complementary material that, when used correctly, extends the functional range of a growing medium. The sections below address the most common questions growers ask when evaluating wood fibre for their substrate programmes.
How does wood fibre affect water retention and air porosity?
Wood fibre increases air porosity in a growing medium and improves drainage, but on its own it holds less readily available water than peat. When blended with peat, the two materials interlock to form a structured matrix that combines high overall porosity with strong water capture and reduced risk of hydrophobicity. The result is a more aerated, better-draining substrate than peat alone, without the rewetting problems associated with dried peat or bark.
In a standalone wood fibre substrate, the lower water-holding capacity means growers need to irrigate more frequently and monitor moisture levels carefully. This is a meaningful management shift for operations accustomed to peat’s large buffering capacity. However, in peat-wood fibre blends, this limitation is substantially offset: the peat provides water retention while the wood fibre opens up the structure and increases air-filled pore space in a way that closely resembles the role of perlite.
One particularly useful property of wood fibre is its ability to maintain rewettability after drying. Unlike bark, which can shift from hydrophilic to hydrophobic when it dries out, wood fibre continues to absorb water evenly, helping to distribute moisture throughout the substrate. BVB Substrates, Kekkilä-BVB’s professional substrate brand, attributes this behaviour to the structural characteristics of their processed wood fibre, noting higher oxygen diffusion rates and improved rewettability in peat-containing mixes. For growers managing container crops, this property reduces the risk of dry pockets forming in the pot and supports more even root development.
What are the main types of wood fibre used in substrates?
The wood fibre used in professional growing media is produced primarily from softwood conifer species, with Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) among the most widely used. Softwoods are preferred because they decompose more slowly than hardwoods, contain fewer phytotoxic compounds, and are available close to production sites in northern and central Europe. More than 30 different wood substrate materials have been developed and tested across Europe and North America, though only a small number have reached commercial scale.
The manufacturing process has a significant influence on the physical and chemical properties of the finished fibre. Three main processing methods are used commercially: screw extrusion, twin-disc refiners (defibrators), and hammer mills. Each produces a fibre with different particle size, compressibility, and chemical profile. Disc refiners and screw-based processors are the most common in Europe.
Thermo-mechanical processing, which uses temperatures above 100°C combined with mechanical pressure, is particularly effective because the heat reduces or eliminates phytotoxic compounds present in fresh wood. BVB Substrates uses steam treatment followed by grinding and fluffing to produce their wood fibre, sourced from 100% pure PEFC-certified European spruce logs, with branches, needles, and residual wood excluded to prevent impurities. This level of source control and processing consistency is important because, as research on wood substrates confirms, variability in species, processing method, and material age can significantly alter the physical and chemical behaviour of wood fibre in a substrate blend.
Does wood fibre affect nutrient availability and pH?
Yes, wood fibre affects both nutrient availability and pH in ways that require active management. Its high carbon-to-nitrogen ratio drives microbial nitrogen immobilisation, reducing the amount of nitrogen available to plants. Wood fibre also has weak pH buffering capacity and very low cation exchange capacity, meaning it provides little inherent nutrient storage and is sensitive to pH shifts caused by fertilisers.
Nitrogen immobilisation
Wood fibre typically has a carbon-to-nitrogen ratio well above 100:1. When this ratio exceeds around 30:1, soil microbes begin to consume available nitrogen faster than plants can access it, a process known as nitrogen immobilisation. Research published in 2025 found that lettuce grown in wood fibre substrates showed significant reductions in biomass and total nitrogen content compared to peat controls, underscoring the need for upward adjustment of nitrogen fertilisation rates when wood fibre is present in the mix.
One practical mitigation used in European commercial production is nitrogen pre-impregnation, where granular nitrogen is incorporated into wood chips before thermo-mechanical fibreisation. This embeds fertiliser within the finished fibre, reducing the supplemental fertility burden during the crop cycle. Regardless of approach, growers should plan nitrogen management from the first day of the crop cycle rather than waiting for deficiency symptoms to appear.
pH behaviour and buffering
Wood fibre substrates tend to have an acidic pH, typically in the range of 4 to 6.5 depending on species and processing, but their buffering capacity is much weaker than peat. This means that acid- or alkali-forming fertilisers can cause larger pH swings than growers may be accustomed to managing. In substrates with high wood fibre content and no lime addition, pH can rise noticeably over the first weeks of cultivation. Most greenhouse crops perform best within a slightly acidic to near-neutral pH range, so regular monitoring and timely correction are essential when wood fibre makes up a significant proportion of the mix.
How much wood fibre can replace peat in a substrate mix?
In commercial practice, 20 to 30% wood fibre by volume is the most reliably proven range for consistent crop performance across a broad range of species without requiring significant changes to standard growing protocols. Higher proportions of up to 50% are achievable, but they require adapted irrigation, nutrition, and monitoring practices. Above 50%, wood fibre as a sole substrate is possible in specific soilless systems, but is not yet the norm for general greenhouse production.
Wageningen University research on begonia in an ebb-and-flood system found that blends containing up to 50% wood fibre produced no negative effect on flowering time over a ten-week crop cycle. However, the lower average water content at these rates required more frequent irrigation and closer attention to nutrient levels. Several commercial growing media already incorporate 30 to 40% wood fibre by volume, confirming that this range is operationally feasible at scale.
A useful framing for professional growers is to think of peat as a conditioning agent within the blend rather than the material being displaced. Retaining a proportion of peat alongside wood fibre provides structural stability, pH buffering, and water retention that supports the overall performance of the mix. At higher wood fibre rates, growers must also account for the fact that wood fibre’s lighter colour compared to peat can make visual moisture assessment unreliable, increasing the risk of overwatering if standard peat-based visual cues are applied.
Kekkilä-BVB’s target is that by 2030, half of the raw materials used in its substrate blends will be something other than peat, with wood fibre playing a central role alongside other circular raw materials such as sphagnum moss, reed canary grass, and miscanthus. The company’s circular raw materials programme reflects a broader industry direction toward optimising blends rather than pursuing outright replacement.
What are the sustainability benefits of wood fibre?
Wood fibre is a renewable, biodegradable material with a low bulk density, which reduces the climate footprint associated with transport.
LCA research comparing bio-based growing media found that incorporating 25% of a wood fibre-based alternative alongside peat reduced the climate footprint of the substrate by between 16 and 33% compared to pure peat. These are the kinds of specific, measurable findings that support compliant environmental communication under EU Directive 2024/825. An LCA study on bio-based growing media confirmed that bio-based peat alternatives, including wood fibre, can show significant reductions in global warming potential across their life cycle.
From a supply chain perspective, wood fibre sourced from certified European forestry operations supports traceability and regional production. BVB Substrates sources its wood fibre from PEFC-certified European spruce, and its low bulk density means the material is relatively efficient to transport by volume. Kekkilä-BVB has invested in new wood fibre production infrastructure in the Netherlands and Estonia to strengthen local supply, positioning wood fibre as a circular raw material that can be produced and consumed within the same regional supply chain.
It is worth noting that wood fibre, like all processed materials, carries its own carbon footprint from energy use in thermo-mechanical processing and logistics. LCA-based comparison remains the appropriate tool for evaluating the net environmental position of wood fibre against peat, rather than categorical claims of superiority in either direction.
Which crops perform best with wood fibre substrates?
Ornamental crops were the first to be produced commercially using wood fibre-based substrates, and they remain the category with the most established track record. Pot plants, nursery stock, and cut flowers grown in peat-wood fibre blends have shown reliable performance across many species. Greenhouse vegetables, including tomatoes and cucumbers, have also demonstrated good results in wood fibre-containing substrates when nitrogen management is adapted from the outset.
In ornamental production, species including chrysanthemum, euphorbia, impatiens, and salvia have been successfully grown in substrates incorporating lignocellulosic materials derived from pine. The Kekkilä Professional FLOW substrate range, which combines premium peat with wood fibre, is specifically formulated for nursery stock, ornamental plants, and pot plants, offering measurable properties including fast water absorption, good aeration, and high structural stability.
For greenhouse vegetable production, research has shown that tomatoes and cucumbers can achieve comparable yields to peat-based growing when appropriate nutrient solutions are applied from the beginning of the crop cycle. Strawberry production in controlled environment systems has also shown promising results with peat-wood fibre blends: a 50:50 peat-wood fibre mix performed comparably to European peat and coir-based alternatives in greenhouse strawberry trials, suggesting it is a viable option for growers seeking more locally sourced substrate components.
The key variable across all crops is not the wood fibre itself but how the substrate formulation is matched to the specific crop’s water and nutrient requirements. Substrate composition needs to be optimised for each crop type, and growers moving to higher wood fibre inclusion rates should expect to adjust their irrigation frequency, nitrogen application, and monitoring protocols accordingly. For growers looking to explore substrate options suited to their specific crops and growing systems, contacting Kekkilä-BVB directly is a practical starting point for technical guidance.
This content was generated with the help of AI and it may contain mistakes