Steam Heat Treatment of Soils
Soil quality lays the foundation for all successful growing operations.
Super-heated steam treatment has long proven its considerable capabilities as the most effective, sustainable and organic approach to eradicating pests, weeds, pathogens and other unwanted organisms from soil. It eradicates virus transmission vectors while boosting plant resilience, increasing plant health and reducing crop loss from pathogens, fungus, weed seeds and bacteria often competing for soil, space and nutrients. Famed for its ability to penetrate deep into the core of soil lumps, steam allows soil to be re-used multiple times over. What’s more, as a non-toxic solution, steam avoids human and environmental health risks associated with chemical use.
Please see our short descriptive video below to help envisage the significant value FlowSteama could provide your business.
W. J. C. Lawrence, esteemed garden curator at the ‘John Innes Horticulture Centre’ and author of highly respected resource, ‘Soil Sterilisation’, introduced the idea of steam heat sterilisation and identified steam as an essential requirement for innocuous, rapid and robust plant growth.
Investing in FlowSteama equipment enables businesses to deliver clean soil to the grower; this is the basis of the best nutritious foundations for growth, reducing seedling mortality and minimising disruption to the balance of organisms required for soil fertility.
Future-Proof Global Crop Production
In a 2021 food security report carried out in the UK, results indicated that up to 35% of global crop production is lost every year from poor growing conditions, plant disease and pests. Results are visualised in the chart below. Annual losses are enough to sustain millions of people and the risks can be easily mitigated. Imagine the benefits of avoiding just a fraction of this waste!
Along with current crop wastage, contaminated topsoil is also regularly wasted. With FlowSteama’s steam sterilisation system, wasted topsoil can be easily recycled, initiating positive circular growing opportunities while reducing risks of soil-borne bacteria causing crop failure. There is strong evidence suggesting that topsoil pasteurisation increases yields, in some cases by up to 300%, proving steam to be an essential component in elevating and enhancing grown plants and produce.
Requirements for Achieving the Best Outcomes
To ensure the highest quality steam results, W. J. C. Lawrence has identified specific sterilisation requirements which have been extensively considered in the engineering of the FlowSteama vessel.
Low Pressure Steaming
Lawrence states there is a limit to the rate soil can absorb steam. If a measured approach isn’t taken, unnecessary steam will be produced and wasted. Using a low-pressure boiler allows the efficient conversion of water to steam. This reduces heat lost from the process and allows more latent heat to be generated and absorbed by the soil. With this in mind, Stronga use low-pressure, super-heated steam instead of alternative high-pressure, more complex solutions.
Soil Moisture Content
Lawrence identified that sterilising soils with moisture content in excess of 35% can use 50% more fuel. Drier soils reduce steam energy requirements and allow for a more effective steam penetration process where a considerable 5lb steam/cu.ft (80 kilo/m₃) of soil can be preserved.
Steam Quantity
Lawrence reaffirms the importance of the steam quantity, stating it to be the ‘chief requirement for efficient sterilising’. Stronga’s FlowSteama engineers have spent years developing technology that ensures 200’C super-heated steam is effectively absorbed throughout the topsoil load. In our opinion, matching steam generation to use is key. FlowSteama and SteamBoila work effectively together with equipment optimally sized for each project. This ensures the appropriate amount of steam enters the pore spaces in the soil, avoiding losses through excessive steam supply.
Screened Soil & Material Agitation
Particle size is also extremely important for effective steam sterilisation. Generally, compacted soils and large soil clods cause uneven sterilisation. Large stones should also be removed by the client prior to loading into the FlowSteama. With particle size and low labour requirements in mind, Stronga developed FlowSteama to have integrated material agitation. The hydraulic ‘PulseWave™’ agitation system mixes soils across the floor in the steam chamber, ensuring even temperature gain throughout all soil particles, across the whole load depth.
Invasive Species Threaten the Future of Crops
‘Biotic Invasions’, an article written in the ‘Ecological Applications’ journal, addresses the invasive species pandemic with a great sense of urgency. Invasions on crops can be exacerbated by human transport and commerce activities, meaning there is great deal that can be done to limit the spread, including adopting phytosanitation methods.
Certain plant invaders have particularly catastrophic impacts on native ecosystems, reducing the quality and quantity of any surviving species while impacting wholesale values, as well as causing extinction to vulnerable plant species. Establishing a control method from the outset is the most proven way of achieving long-term control and prevention. It is far less costly to steam sterilise soil before planting and propagation than to apply pest control to a variety of ‘individual invaders’ after they are established.
Some of the most harmful and common invasive species/plants include; Japanese Knotweed, Giant Hogweed, Whitetop weed, Barnyard grass, Root-knot nematode and Potato cyst nematode. Steam treatment is the cleanest and safest way of controlling and reducing their harmful impact on soil, proving essential for the future health and prosperity of grown produce.
‘Thermal Death Point’
A term coined by Lawrence, “thermal death point” refers to the appropriate temperatures required to rid soil of diseases, pathogens, fungus and various other unwanted organisms. Experts including Kenneth Baker and W. J. C. Lawrence agree that temperatures between 70’C-85’C are sufficient in removing a significant proportion of pathogenic fungi, soil-born pests and disease. The graph below has been developed with their expert advice in mind and illustrates the depth of FlowSteama’s heat treatment capabilities. For each temperature, a 20–30-minute treatment cycle is applied.
Transformative Clean-Steam Technology
Steam treatment cycles improve soil’s crumb structure and friability, encouraging increased aeration and improved drainage while releasing nutrients for healthier plants, pest-free with increased yields.
Using FlowSteama enables pioneering growers to join the circular growing economy, reducing losses associated with infected crops from soil-borne diseases. Growers are able to repeatedly use steam sterilised soils with high germination rates to propagate a variety of crops without fear of cross-contamination, stunted growth or ‘damping off’. A key benefit of FlowSteama is that it enables the easy adjustment of ‘time at temperature’ via the easy-to-operate ‘SteamStation™’ HMI controls. The video below demonstrates the benefits of the ‘circular growing economy’, enabled by FlowSteama.
Save Fuel with Energy Recuperation
Stronga’s optional energy recuperation system has seen increased interest during recent periods of high energy costs and growing awareness of CO₂ emissions. FlowSteama’s ‘heat recuperation system’ directly saves fuel in the region of 25%-30%, allowing effective recuperation of valuable heat energy.
Please contact Stronga directly for more information on specific features of energy recuperation.
Chemical Solutions are Fading Fast
For decades, chemical companies have advertised chemicals as a good and safe method of control in soil. There is no doubt that various pesticides, nematicides, insecticides and fungicides have delivered short term crop yield and quality improvements. However, long-term effects were underestimated. Current research has revealed harmful unintended consequences of prolonged chemical treatments, harmful and toxic to nature, soils and human health.
Increasingly strict protocol, such as protective clothing, eye wear, masks and aeration, is in place for operators when spraying harmful chemicals, while some of the more harmful chemicals (Methyl Bromide) have been completely phased out since the Montreal Protocol was finalised in 1987. In addition to strict operator protocols, recent research has also proven chemical pesticides often contain volatile gases and often leave ‘hidden’ harmful residues. Research from ‘Science of The Total Environment’, indicates over 80% of tested soils across Europe contain pesticide residue.
If the risk to human and environmental health isn’t enough, chemical solutions are also increasingly expensive and have other application constraints. Unlike steam, chemical’s often only target a single specific pest or disease, resulting in complex decisions around timings and spray applications. A number of chemicals are required for effective control against a variety of organisms, with some pathogens and nematodes even developing resistance to chemical compounds.
Steam treatment looks to be the natural progression.
5 Reasons to Steam Sterilise Soil
1) No risk of pathogen resistance.
2) No harmful health risks to soil, plants or people.
3) No extended aeration period between steam application and cultivation.
4) Regenerative process where no chemical residues are sustained in plants and groundwater/soil.
5) Tried, tested and proven, steam is effective against a large variety of pathogenic organisms, fungus and diseases.
Overall, FlowSteama’s topsoil steam solution represents the most useful, practical and reliable form of soil remediation available in the market, treating soil effectively while allowing it to be utilised soon after a short cooling period, posing no risk to human health or nature.
Enhanced Soil Revitalisation, on All Levels
FlowSteama reduces soil-borne inhibitions on plant growth, enabling heat-treated topsoil to reach temperatures of 85'C. Time parameter controls prevent excessive heating and damage to the soil microbiome while the reintroduction of soil inoculation, perlite and composts can further enhance sterilised output.
To summarise the benefits, Stronga topsoil heat treatment enables;
- ‘Improved crumb structure and renders the soil more friable, allowing it to produce better aeration’, Lawrence identifies.
- Improved crumb structure, allowing more open pore spaces for optimised soil fertility via microbial biome activity. This allows for good nutrient circulation, cultivation ability and root growth development.
- Improved structure, moisture retention and air circulation of soil, directly increasing yield and growth of healthy plants.
One-Step Super-Steam Process
FlowSteama equipment from Stronga uses energy-efficient, super-heated steam for immediate heat transfer, ensuring the entire load of soil is successfully sterilised, restoring fertility with very low labour requirements. The benefit of super-heated steam is that it replaces air in the pore spaces of soil, condensing on cold surfaces and rapidly heating them up to the target core temperature. Once the soil has been treated at approximately 85’C for operator-controlled ‘time at temperature’ periods, often 20-30 minutes, the soil can be used soon after in the next crop cycle.
A key benefit of FlowSteama equipment is that it is fully insulated to prevent steam energy escaping to the atmosphere when heat is transferred from the boiler. Note how, in the thermal camera mapping shown below, the only part of the camera showing heat is the heat-treated output material; the FlowSteama vessel itself is insulated and therefore highly thermally efficient, reducing losses to the atmosphere and saving cost.
Architects of Renewal
At Stronga, we like finding situations where our products add considerable value for customers. FlowSteama creates value, ensuring that increasingly-scarce topsoil can be re-used over and over for healthy plant growth.
Our highly skilled engineers are adept at scaling and designing each FlowSteama vessel to the client’s specific soil type and throughput targets. We thrive on open collaboration with our clients to ensure the most favourable end result is achieved, meeting their long-term business goals. Collaborating with Stronga opens up a wealth of valuable opportunities for your business. Let us assist you on your soil transformation journey - info@stronga.co.uk
Bibliography:
Baker, Kenneth, ‘The U. C. system for producing healthy container-grown plants through the use of clean soil, clean stock, and sanitation’, 1957. https://archive.org/details/ucsystemforprodu23bake
Lawrence, W. J. C., ‘Soil Sterilisation’, 1956. https://archive.org/details/dli.ernet.425583/page/29/mode/2up
Mack, Richard and Simberloff, Daniel and Lonsdale, W. and Evans, Harry and Clout, Mick and Bazzaz, FakhriA. (2000). Biotic Invasions: Causes, Epidemiology, Global Consequences and Control. Ecological Applications 10. 689-710 https://www.researchgate.net/publication/201999174_Biotic_Invasions_Causes_Epidemiology_Global_Consequences_and_Control
Silva, Vera, ‘Pesticide residues in European agricultural soils – A hidden reality unfolded’, 2019. https://www.sciencedirect.com/science/article/pii/S0048969718343420
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