Many clients who approach Stronga have a wide range of growing blends and media types on-site. Stronga focus on each growing blend, one-by-one, to ensure we optimise the steam sterilization system for the job to be done.

Stronga were recently approached by a Belgian supplier of composts and other growing blends. They enquired about steam sterilizing a whole tree shredded material which had already partly composted, shredded with pieces up to 70mm long prior to further grinding down to fibre for use as growing blends. The goal of their shredded wood sterilization project is to reduce the use of peat in their growing blends.

The image below sent in to us by the client demonstrates the material to be steam sterilized.

Stronga understand there is often variation in bulk density of the material, however in this case we came to the conclusion that the bulk density of the shredded wood was around 500kg per m³.

The effect of material moisture content and bulk density on the amount of steam needed to raise the material temperature is also an important consideration. The ideal material moisture content for steam sterilization is around 20-25%; at this level there is the lowest energy requirement and lowest kg of steam per m³ of material while the steam front transfer through the material is efficient. This level also gives the lowest added moisture in condensed steam in the product.

The Stronga steam sterilization process brings the material to be sterilized to 80-85˚C. The period of time the FlowSteama holds material at temperature inside the steam vessel can be controlled and optimised by the operator to suit local sterilization rules and regulations. The trade-off of slowing down the FlowSteama moving floor to achieve more time ‘at temperature’ is a lower output m³ per hour.

At the discharge point of the FlowSteama, it is possible to heap the material with a suitable rising auger into a stockpile or container to hold the material at temperature for longer periods, if required. The material could stay at say 70˚C for many hours after the in-vessel steam sterilization process.

When sizing the SteamBoila, Stronga consider the material to be sterilized and the output per hour required by the client. We advise clients on the amount of fuel required to generate “X” amount of steam and this helps our customers imagine the operating costs associated with their steam sterilization equipment.

Of course, lighter / lower bulk density materials use less steam. Our client in Belgium was considering obtaining recycled growing media material from local growers. Stronga discovered that this recycled fraction weighed circa 250kg per m³ and was dryer at 25% moisture. We discovered that the recycled fraction would use approximately ½ the amount of steam as the fresh shredded wood fraction, and was therefore far more economic to sterilize.

Stronga recognise the strong and growing interest in avoiding the use of peat as a growing substrate and a reduction in a use of chemicals with the associated side effects on humans and the environment. We are excited to play our own small part in the movement towards using shredded wood as a high quality, renewable, environmentally friendly and lower cost alternative.

Learn more below about why growers are driving away from peat use.

Peat and peatlands are hugely important for plants, the wildlife that depend on them and mankind, too. Peat bogs store vast amounts of atmospheric carbon which must kept locked in the ground to avoid contributing to devastating climate change.

On top of their role as an important carbon sink, peat bogs are also extremely efficient in soaking up rainwater and thus help to reduce risk of flooding. Water that is filtered through healthy peat bogs is of a higher quality than water filtered through degraded bogs, making it cheaper to treat as drinking water.

What’s more, peatlands are also home to a wide variety of flora and fauna including colourful mosses, cotton grasses, rare sedges, cuckooflower, marsh violet, sundews and much more. The wild plants that are common in peatlands support a range of butterflies, dragonflies and birds.

In simple terms, there is nothing wrong with peat extraction, but our current use of peat as a growing substrate has become unsustainable. The facts are damning with commercial extraction at the current rate removing over 500 years’ worth of peatland growth in a single year. Pursuing alterative growing media blends, such as recycled shredded wood, is an ethical and environmentally-friendly alternative solution for commercial greenhouses and nurseries.

Stronga see a good commercial future for the business of using recycled substrate for local growers when it is carried out in an efficient, considered and intelligent manner. We see great potential in re-using good quality growing medium via in-vessel steam sterilization.

It seems to us that currently too much good valuable growing media is wasted. See further information about FlowSteama in the following link: https://stronga.com/en/stronga-flowsteama-steamboila-reducing-waste-in-your-business/

Contact Stronga today to learn more about our steam sterilization solutions – sales@stronga.co.uk