De-barking roundwood timber is an early-stage process at sawmills with subsequent bark residues previously considered to be a waste product. More recently, however, there has been a transition in thought about discarding bark which holds significant value with a number of specific qualities allowing it to be transformed into valuable products that increase business income.

The issue for suppliers of bark products is that phytosanitary requirements rightly aim at reducing the spread of nematodes, beetles, diseases and harmful organisms that kill trees. In areas where bark infection and nematode spread is rife, bark is required by law to be felled and/or burnt. However, FlowSteama’s steam sterilisation offers a viable solution for disinfecting bark, enabling it to be screened, sorted and sold into separate income streams across multiple sectors. This article, together with the graphic below, details the many utilities of disinfected bark products.

Whether due to a shortage in material availability, sawmill slow-downs, harmful pathogens or restrictions concerning peat extraction, uses of bark products are increasing on a global-scale and the resource’s demand continues to exceed available supply, in the UK market and beyond.

Annually approximately 400 million m₃ of whole bark residue is produced and the majority is underutilised. The time to join the bark product supply industry is NOW, and Stronga are available as your experienced bark heat-treatment specialists.

After debarking, steam sterilisation is a vital next step, followed by screening and sorting of the various fractions. Some fractions can be separated into fine, medium and coarse grades, and packaged for use across different sectors. Bark fractions can then be categorised based on functionality and application, including ‘play grade’ bark, ‘nursery grade’ bark or ‘ornamental grade’ bark.

The majority of bark in the UK market is pine species which provides profitable opportunities for distributers and sustainable solutions for consumers. Bark residues have a wide range of applications as soil improvers, for composting, peat replacement, briquettes for energy production, landscape mulches and weed suppressions.

At Stronga, we have experience working with a number of pioneering companies who have seen the benefits of early adoption by cooperating us to acquire premium-level steam sterilisation solutions. Below, we have put together a short summary of the most highly favoured uses of screened, sterilised and treated bark.

One of the most common uses for bark is as an ‘organic mulch’ which is often available in different grades; (1) fine grade (composted bark); (2) medium grade (ornamental bark); (3) coarse grade (decorative grade bark).

As bark mulch decomposes in soil, the soil becomes loaded with organic nutrients which aid in growing healthy plants. These qualities mean bark can be used as a component in alternative ‘peat-free’ mixes which is important given that peat is becoming more stringently regulated. Bark therefore provides a viable option to many nurseries and gardeners facing the struggle to find ‘peat-free’ alternatives.

What’s more, by creating a ‘bark barrier’, bark mulch helps to prevent weed growth while also helping soil retain appropriate temperatures, absorbing moisture in dry conditions and allowing rain penetration in wetter conditions, protecting roots from adverse weather conditions and eventually, conditioning the soil and stabilising soil pH.

Composted fibrous bark fines can be used as an alternative to peat, offering similar soil enriching and porous properties and significant moisture retention benefits, especially during drought periods, avoiding the costly and negative environmental implications of using peat.

Screened and composted bark mulch can be used alone or as part of a compost mix. However, in order for composted bark fines to be considered suitable for professional growing applications, it is essential that all harmful pathogens, pests and weeds have been steam sterilised and destroyed. Using Stronga’s FlowSteama solution is the most economic and safest way to achieve this. Steam sterilising bark mulch ensures no new harmful pathogens are introduced to the freshly applied area while also enabling suppliers to export high value mulch, across borders, in accordance with increasingly stringent phytosanitary requirements.

Like fine grade bark, medium grade fractions can also be used for mulching, erosion control, improved drainage and weed suppression purposes. Once screened, white wood can be removed and the coarser bark remaining can be utilised for its aesthetic qualities, providing a decorative and natural finish to outside areas including garden beds, baskets and pathways. Distributing steam sterilised bark is essential in reducing the risk of spreading pests and disease. Choosing steam sterilisation as your disinfection method consolidates your reputation as a trusted, reliable, ‘clean’ bark supplier.

Coarser bark is highly durable and visually impactful, providing an overall attractive ‘eco-friendly’ finish to dedicated landscapes. Coarse decorative bark is a highly versatile product which can be used to improve the appearance of flower beds and around trees. When tested in accordance with fire safety and ignition resistance standards, coarser and more durable decorative bark can also be used as a safety measure around petrol stations and in schools.

Among many other uses, small grade, decorative pine bark can also be used in reptile enclosures with bark chips providing a suitably-humid, absorbent bedding. Bark substrate creates the perfect burrowing conditions for smaller reptiles and is fully compostable.

Note - Stronga encourage customers to check the bark species selected is safe for use in reptile enclosures and has been suitably steam sterilised, prior to application.

Bark nuggets are available in a variety of sizes and have minimal dust and white wood content. Those striving for both a high-quality appearance and practical weed suppression can rest assured that uniform bark nuggets achieve high quality finishes in all outdoor spaces. Like some of the previous bark fractions discussed, bark nuggets can also be used in water features, borders and for ground cover, adding texture and striking colour to the landscape.

Using bark chips in playgrounds has become highly popular but, in order to qualify, safety certifications and stringent testing is required to ensure settlement factor (percentage) and critical fall heights have been appropriately tested to local standards (e.g. BS EN 1177). For play bark production, screening must remove all dangerous shards of bark while meticulous testing is also required to ensure the material is free from dust and fines.

Steam sterilised play-bark chips provide a pest-free, disinfected material for children’s play-parks, as well as providing an aesthetic, authentic-looking landscape. Councils, home owners and outdoor play companies are realising the benefits of play-bark over other alternatives. With its self-levelling, frost and stain-resistant qualities, parents can rest easy knowing bark is the superior solution for their child’s play-park.

Steam sterilising bark residues adds significant value to what was once widely considered a waste product, making a compelling business case for those wanting to sell clean products for a variety of uses. Distributers using pure, 200’C super-heated steam for a minimum of 30 minutes ensure bark fractions are clean, weed and pathogen-free, exceeding phytosanitary regulations.

Each invasive organism has different levels of thermo-tolerance. In the FlowSteama vessel, a temperature of approximately 85’C is reached for thorough steam sterilisation, setting the standard in the heat-treatment market. As the graphic below shows, the FlowSteama process ensures all harmful nematodes, larvae, fungus, pests, pine beetle and disease are eradicated.

It is essential that steam sterilisation has taken place before bark is sold since most barks are susceptible to pathogen infestation and are recognised as high risk in countries not yet affected by bark pests and nematodes. The list of quarantine areas is expanding and indicates which bark and pests represent the highest risk to import regulations (e.g. pine wood nematode is predominantly spread through timber import/exports).

Phytosanitary requirements and forestry commissions highlight the importance of bio-secure precautions that reduce the spread of pathogens and allow wood products to be transported freely and safely across borders. FlowSteama’s superheated steam process comfortably exceeds the highest required temperatures, providing full assurance to bark distributers and end-users.

To emphasise the point, we’ve created the animation below which highlights how quickly ‘imported’ pathogens can spread, when allowed to do so. In Portugal, millions have been spent in an attempt to eradicate ‘pine wood nematode’, something that could have more easily been controlled if imported timber was steam sterilised before import into the country.

Stronga are increasingly being approached by customers who have had costly experiences in the past with contaminated bark imports/exports being turned away at ports due to inadequate sterilisation certification. In order for bark by-products to be considered a valuable, saleable asset, steam sterilisation needs to be evidenced.

FlowSteama enables excellent record keeping of all sterilisation cycles, allowing operators to prove the appropriate duration of steam treatment has occurred at the target temperature. Steam sterilisation is central to the process of operating competitively while adding value to bark in growing markets on an international scale. Don’t miss the opportunity to be a part of something transformative.

In order to avoid non-compliance as enforcement increases, clients can invest in FlowSteama steam sterilisation systems to ensure the best possible steaming outcomes.

- FlowSteama uses 200’C low pressure, super-heated steam to fully penetrate and uniformly disinfect bark loads.
- FlowSteama is well insulated, reducing energy losses while there is minimal noise pollution when the equipment is in use.
- FlowSteama has special PulseWave™ technology which ensures bark material is fully mixed and tumbled during the steaming process.
- FlowSteama’s SteamStation™ can be used to evidence temperature and time parameters have been met and prove sterilisation requirements have been achieved. These records can be kept for up to a year and are critical in providing steam sterilisation evidence.
- FlowSteama is equipped with a clear “clean/dirty” side system which encourages good bark sanitation practises, to reduce the risk of re-contamination.
- Stronga’s heat recuperation system can be implemented to encourage energy recovery and increase efficiency by up to 25%, depending on certain factors.
- The SteamBoila automatically modulates down when no more steam can be absorbed into the bark in the FlowSteama vessel.

At Stronga, we like adding value. We like delivering good-value solutions and we like enabling customers to gain valuable opportunities through generating saleable, high-value products. FlowSteama creates value, not only through steam sterilisation but also by providing immediate confidence that sterilised value-added bark products can be used and sold worldwide.

If you appreciate value, collaborate with a team that recognises your value - info@stronga.co.uk