For growers undertaking landscape-scale nature restoration, woodland expansion and forestry management, CleanSteama provides a simple, chemical-free approach to pasteurisation, preparing propagation trays for their next cycle.

For one customer, a family-owned specialist forestry nursery who are growing their own tree stock from locally collected seed; CleanSteama contributed to long-term woodland restoration, ensuring every propagation cycle started with a ‘clean slate’.

Transferred disease and pathogens means lost plants, wasted labour and growing time, disrupted production schedules, and ultimately fewer trees ready to plant when needed. CleanSteama reduces risk of damping-off, root rot and water moulds, all typically associated with forestry seedling propagation.

Where growing trays are densely packed and used repeatedly across successive growing cycles, effective cleaning and hygiene between crops is essential.

Any residual organic matter, pests or pathogens carried over in propagation trays can be introduced into the next generation of seedlings, putting valuable young plants and the wider restoration programme at risk.

In this customer’s case, the plug-and-play CleanSteama solution uses 75°C (170°F) steam to suit the customer’s tray manufacturer recommendations. Steam penetrates the surfaces and cells of the stacked propagation trays, heat treating organic residues, reducing the risk of pest and disease carryover using clean “green” steam.

For woodland restoration programmes, where thousands of seedlings may pass through the same propagation infrastructure, CleanSteama helps protect the whole investment; including the young trees that grow in them.

Healthy seedlings grown in pasteurised propagation trays.

CleanSteama uses an electric steam boiler/generator to supply low-pressure steam to an insulated vessel with steam evenly distributed via a specialised pipework assembly. The steam vessel is extremely easy to operate and well-insulated to maintain the steam treatment temperature of approximately 75°C.

Unlike harmful chemical spraying or high-pressure tray washing, CleanSteama delivers reliable, controlled, sustained heat that permeates the entire tray surface, including every cell, corner and recess for time at temperature requirements of 30 minutes to 1 hour.

Steam is an excellent means of heat transfer. The CleanSteama operates at low 0.5 bar pressure, with steam supplied to the steam vessel automatically, circulating around every surface of the stacked propagation trays. For this particular customer, the in-vessel internal treatment temperature was designed to not exceed 75°C, with temperature monitored during the cycle.

The unique in-vessel steam distribution system includes the steam supply pipework between boiler and vessel, valves, fittings and controls required for operation (power indicator/pressure gauge/heating instructions etc.).

As described below, the CleanSteama pasteurisation process is low-cost and extremely simple:
1. Pallets with stacked trays are driven, using a forklift, into the ‘dirty-side’ end of the CleanSteama vessel, and dropped off.
2. Once the vessel has been loaded with circa 24 pallets, the ‘dirty-side’ doors of the CleanSteama are closed to tightly seal the vessel.
3. The electric SteamBoila is powered on; steam instantly and rapidly transfers heat throughout the entire vessel.
4. Once the vessel is filled with steam, the SteamBoila modulates on and off to maintain the steam and heat environment.
5. After the validated treatment period of approximately 1 hour, pallets are forklifted away from the ‘clean-side’ of the vessel, reducing contamination risks with the dirty, used material.

The electric SteamBoila is designed to deliver 100kg of steam per hour which is sufficient for a single, 75m³ in-vessel application, with a mains water supply requirement of approximately 100 litres per hour (this can be adjusted to 25/50/75/100kg of steam per hour).

Once the vessel has filled with steam, the SteamBoila, which comes with a standard water-softening kit, automatically modulates steam, cycling on and off as steam condenses against colder surfaces. The CleanSteama E100 uses a 100-amp, three-phase mains electrical supply or suitably sized diesel generator.

The benefits of the CleanSteama Electric 100 include:
• Highly efficient energy-to-steam; 95%+ efficiency on-site.
• No exhaust gases, flues or heat exchangers required, can be located inside or outside with a cover, depending on preference.
• ‘Pollution free’; potential for renewable electricity use.
• Super-fast, simple, plug-and-play start-up.
• Low capital costs and installation cost when compared to fossil fuel alternatives.
• Compact footprint compared to fuel boilers with same capacity.
• Low maintenance, simple long-term upkeep.

Talk to our team if you do not have a sufficient electrical supply available, we can offer alternative solutions: enquiries@flowdrya.com

The electric SteamBoila, complete with controls, forklift pockets and weatherproof housing.

Stronga are leaders in the field of pasteurising substrates, growing trays and other greenhouse equipment.

CleanSteama is designed to ensure the utmost efficiency, the rapid forklift ‘clean-side’ unloading and ‘dirty-side’ loading and plug-and-play design, mean that once the system is loaded and running, no further supervision is required.

The vessel is designed to allow up to 24 pallets, up to 2 metres high, each with circa. 150 trays per pallet, to be steam pasteurised at once. We’ll do the maths… That’s circa. 3,500 trays every single hour (depending on tray size).

With some information about your production volume, current crop loss and current tray cleaning process; our expert team can calculate the overall cost savings and electric cost specific to your growing operation: enquiries@flowdrya.com

Doors open; CleanSteama pre-1 hour heat-treatment, loaded and ready for the pasteurisation cycle.

CleanSteama uses electrically-generated steam to enable the reuse of propagation and growing materials without the fear of harmful fungal pathogens; Pythium spp. and Fusarium spp. and water moulds; Phytophthora spp.

Using temperatures up to 75°C, or in line with tray manufacture’s requirements, growers reduce seedling mortality and chronic root damage; producing a crop that is healthier and stronger for subsequent forestry planting. Depending on the number and value of trays being processed, the potential return on CleanSteama can be substantial: a one-year capital payback.

CleanSteama hygenisation = low seedling mortality + upgraded crops + increased uniformity + reduced labour for remedial work (re-planting)

Beyond trays, the same vessel-steaming heat treatment system can also be used for bagged growing substrates, extending the steam pasteurisation opportunity for growers. Coir, peat-based media and other propagation growing substrates can be effectively treated in big bags or wire-frame mesh stillages, within the insulated vessel.

The benefits include:
• Insurance against devastating crop losses.
• Ability to recycle pots, greenhouse tools and growing media.
• Reducing weed seeds and unwanted plant material.
• Reducing pest carryover and pathogens.
• Managing biological contamination between crop cycles.
• Reducing the cost and logistics of continually purchasing fresh substrate.
• Elimination of chemical usage, such as Methyl Bromide.

For growers purchasing large quantities of coir, peat or substrate blends, the ability to treat reusable material can represent a significant additional substrate cost saving. It also supports a more sustainable approach to horticulture: treat, reuse and recirculate rather than purchase and dispose.

Check out our other steaming articles for further information >

Investing in CleanSteama, growers choose a system that will clean, pasteurise, reuse and recirculate valuable production assets; including expensive trays and valuable growing media.

For high-volume nurseries and growers, that can mean greater cost control over the hygiene of each production cycle, while providing a flexible batch treatment system capable of handling both trays and selected growing substrates, providing the confidence that trays are pathogen and disease-free.

Stronga also offer steam sterilisation that uses 200°C super-heated steam. Please contact our team; we would be happy to help assist with your project: enquiries@flowdrya.com

Further reading;
Pasteurising propagation trays, crates & pots, with Stronga FlowSteama >
Using FlowSteama & SteamBoila to reduce waste in your growing business >
Steam heat treating peat; a microgreen grower success story >