Archive for the ‘Effect of Steam’ Category

Hot steam finds its way into Kenya

Samstag, November 13th, 2010

Even where labor and land is cheap, hot steam is needed to sterilize arable land. In September 2010 a big Dutch flower grower started to use its steam generator in its Kenyan green houses.

Area steaming in Kenya – Flower growing
Area steaming in Kenya – Flower growing

Steam is mainly used to sterilize volcanic substrate so the material can be reused several times. The substrate gets steamed in steam boxes which are equipped with a vacuum steaming system. Vacuum steaming systems are highly energy efficient. The steam generator was manufactured by MSD Corp., Durbach.

Soil decontamination with hot steam

Dienstag, Dezember 22nd, 2009

Decontaminating and disinfecting soil with hot steam has been applied for more than 100 years and is well proven. The Swiss Friedrich Miescher Institute in Basel has made use of this method.

The institute will decontaminate the soil of several green houses completely without chemicals. The goal is to free soil from sproutable plant parts such as seeds and roots as well as restore the original condition of the soil before cultivation without residues of chemical products. Hence steaming was the first choice.

A contractor is responsible for steaming. First soil is loosened down to 20 cm depth, after that the area is gradually covered with steaming sheets which get weighted. Steam generated with a low pressure steam boiler, is induced via a steam injector underneath the sheets.

After 2-4 hours of steaming the desired results are achieved: The soil is completely sanitized and without weeds and diseases.

Steaming on the „Green Week 2010“, Berlin

Mittwoch, November 18th, 2009

The horticulture consulting department of LB Berlin plans to introduce steaming systems for hobby gardeners on the Green Week in Berlin in January.

Owners of smaller garden plots shall have the chance to get more information on the advantages of steaming.

What works for big growers also works for small growers

It takes a little more efforts but steaming on a smaller scale is feasible. Before cultivation soil and “self-made” compost are freed from weeds, weed seeds and in particular pest and diseases without chemicals – 100% residue free!

Plants pay back with better growth and more nutrients!
This fact is scientifically proven. Hence Mr. Prof. Dr. Klaus-Dieter Hentschel from  the renowned Humbold-University, Berlin, unreservedly recommends steaming, also for hobby users.


“Less toxins = more nature and active, healthy regeneration

This slogan is followed by more and more hobby gardeners that show responsibility towards society as responsible citizens. For small growers joy of gardening already starts when seeding plants.

Healthy seedlings only grow in healthy soil which is not always available in abundance in small garden plots. Also purchased soil or compost not always fulfill all high phytohygienic requirements for seedlings.

A small steam generator in the shape of a push cart which gets introduced at the upper mentioned event,  is a suitable solution. This inexpensive and easy to use device sterilizes about 70 to 80 liters of substrate within 2 hours and  just € 1,- energy cost.

This old but technically newly improved steaming method uses temperatures of just 60 to 80 degrees which are sufficient to successfully sterilize fresh compost and contaminated soil. Steaming not only improves the condition of soil or substrate but also unblocks nutrients and enhances the starting position and the resistance against pest and diseases of seedlings.

I think that this device has been long waited for by hobby gardeners. It supports their ecologically minded and responsible activities and should be available in every garden.“

The regional board of Freiburg fights Japanese knotweed, an invasive neophyte, with hot steam

Samstag, Oktober 3rd, 2009

Japanese knotweed (Fallopia Japonica) belongs to the problematic non-native plants (neophytes). The plant originates from the far east and has spread rapidly through Central Europe, the British Isles as well as the United States, causing major damage to dams, walls and streets due to its powerful growth. Furthermore it destroys native plants and endangers biodiversity.

In the West of the German federal state Baden-Württemberg, public offices have been dealing with this issue for more than thirty years. In the Ortenau region, dams have been damaged since Japanese knotweeds destroyed sod causing high water to penetrate into building structures, resulting in fatal problems with their stability.

The regional board of Freiburg reports on studies to control Japanese knotweed with hot steam.

Conventional mechanical methods such as mowing and mulching are not able to diminish the population, they only hinder spread. At present the only remedy available are broad band herbicides such as Round-Up, which are not completely safe. Hence they cannot be used in close proximity to water due to their water damaging effects. Furthermore, they have to be applied over several years in order to significantly decrease the population.

For these reasons, the regional board of Freiburg decided to study the effect of hot steam on larger contaminated areas. In September 2009 about 500 square meters of afflicted soil was excavated down to 30 cm depth to fully remove the soil layers mainly infested by the plant rootstock. The contaminated excavation was steamed in a specially prepared trailer. The steamed ground was put back and the area re-natured.

The lowland adjacent to the river is paved with stones and was specially treated. Since excavation of infested soil was impossible due to the pavement, areas were gradually covered with special steaming hoods and treated. Since then the steamed areas are supervised by staff of the regional board (Mr. Keller, Mr. Martin) and by staff of MSD Corp. (Moeschle-Seifert-Daempftechnik), which has supported the study with technical equipment and expertise.

In a second step, sprouting plant parts in deeper not treated soil layers will be partially steamed with steaming lances reaching up to 1 m into the soil.

Prior to the study MSD Corp. and the association for sewage treatment Offenburg (Mr. Mohn) has already made an initial study in the beginning of 2009. Due to the highly positive results yielded in this first trial, in which no shoots occurred more than half a year after steaming, positive results are expected for the next study as well.

For more information on Japanese knotweed, please check on Wikipedia Wikipedia.

Control of wild herbs with hot steam

Sonntag, September 27th, 2009

The public sector, such as communities, must also deal with solutions to control wild herbs and weeds.

On squares, streets and sidewalks, weeds amass in gaps and free areas and have to be eliminated. Furthermore, challenges arise due to the steady spread of problematic plants such as the invasion of neophytes.

Invasive Neophytes and other problematic plants

In recent decades many non native plants have been introduced to Central Europe.

Many of these plants cause growing problems due to their rapid growth. Some are harmful to health such as Ambrosia, while others endanger biodiversity since they supplant native plant varieties and detriment the natural habitat. Among these is Japanese knotweed (Fallopia Japonica /Reynoutria Japonica) whose powerful growth suppresses other plants and depending on its location may damage agricultural land or building structures such as dams, streets and walls.

Furthermore, native problematic plants are further advancing such as ragwort which is toxic and can lead to liver damage and even fatal poisoning depending on the ingested dosage. The accelerated spread of ragwort can be traced back to growing area of fallow land and climate change.

In particular the public sector is faced with the challenges to address this issue.

Today two methods are applied for weed control: 1. Mechanical means such as brushing, mulching, bunking and mowing 2. Application of herbicides. In particular the usage of chemical means is limited due to its harmful impact on nature and humans.

Hot steam is an adequate alternative.

Steaming systems for weed control in public spaces are available and can universally be applied. In contrast to mechanical methods, which are quick and simple, steaming provides the advantage that not only superficial plant parts are removed. Hot steam penetrates into all gaps and fights the complete plant. It kills all sprouted plant parts and weed seeds making it really worth the effort. The results are completely weed-free areas which only require to be retreated once or twice a year. No chemicals are needed and the treatment is residue-free.

Steaming and other thermal methods.

Besides hot steam there are other thermal methods used for weed control available on the market such as infrared rays, scarfing and hotwater systems. The efficacy of these methods is often insufficient despite their relatively high energy usage. Radiant heaters preserve surfaces but require long residence times until heat has sufficiently damaged the plant in particular reaching parts underground. Scarfing devices have the same problem, since they show little depth effect.

Hotwater systems may overcome these issues. When applied properly, these systems can kill deeper sprouted plant parts at temperatures higher than 65°C for a positive long term effect. However hotwater systems show high energy losses and massive water consumption. Hot steam does not have these disadvantages.

More than „Hot air“

In contrast to hot water at 100°C, hot steam at 100°C contains about 5 times more energy. Furthermore its density is 1000 times lower. Hence when using hot steam, users need less water and can apply more heat to fight weeds: The result are weed-free areas at relatively low energy and labor cost. Furthermore, low pressure steam generators are very easy to handle.

In contrast to methods using extreme heat and high pressure the application of steam has more positive effects: Soil surface is preserved and freed from weeds, moss and linchen. Steaming even cleans deeper soil layers. Persistent dirt such as gum, etc. is loosened and can be removed easily after steaming.

Steaming systems are suitable for small as well as large areas with different surfaces such as sports and playgrounds, sidewalks, parking lots and cemeteries.

Steam can be applied anywhere.

Steam can be applied in many different areas. Communities can use steam generators not only for effective weed control and cleaning of squares and streets. Steaming systems can also be used to treat municipal green areas, beets and compost or zoological gardens. If coordinated and applied properly a steam generator never stands still.

Hohenheim Univeristy confirms the high effectiveness of steam against weeds at the 32nd horticulture day

Sonntag, September 20th, 2009

On the 19.09.2009 (32nd horticulture day) Hohenheim University located close to Stuttgart presented the results of open field tests for weed control.

From June to September 2009 three methods of weed control were tested 4 times repeatedly on parcels of 16m x 1.2 m. On the parcels two Baby-Leaf salads “Batavia red” and “Batavia green” were planted.

The total testing area was divided into 18 plots, on which the three methods were compared with each other: weed control with pick, with herbicide and with soil steaming.

Steaming took place once before seeding after sufficient soil loosening, while herbicides were applied after seeding. Manual seed control with pick took place when weeds started to occur. Control plots were not subject to any weed control means.

Baby-Leaf cultures were harvested after 4 weeks. Then freshmass and drymass of salad and weed of all three test variations were measured and compared (steaming, herbicide, pick).

University Hohenheim yielded the result that after the application of 90°C hot steam, no weeds grew in the cultivation period. On sufficiently steamed areas weed control of Baby-Leaf-Cultures is not necessary.

Nitrate and Ammonium

As expected when examining the steamed soil, a relatively high but harmless concentration of ammonium and after harvest a high concentration of nitrate was measured due to the blocking of nitrifying bacteria through steaming. Ammonifying bacteria however were less affected through hot steam. Hence ammonia accumulates in steamed soil. More detailed results were yielded by S.N. Malowany and I.D. Newston in the middle of the last century already. Normally the ammonia / nitrate ratio normalizes within 6-8 weeks after steaming. This period can be significantly shortened if nitrifying and ammonifying bacteria are injected into the soil right after steaming(Integrated Steaming).

Practical experience of weed seed control with hot steam in horticulture

Sonntag, September 13th, 2009

Since the middle of the last century, the effectiveness of humid heat to fight weeds, in particular their seeds, has been researched thoroughly. Within just 5 minutes all seeds can be rendered ungerminable as long as hot steam of 95°C is used steadily.

In practice today there is a trend of shorter treatments with hot steam in particular when fighting weed seeds on open fields. In particular in France, the Netherlands and in Denmark big areas of beet cultures are superficially sterilized to up to 5-10 cm depth using steaming automats. Special hoods with a total area of up to 20 square meters are moved step by step after just 5 minutes of steam injection.

The goal of using short steaming periods however is not the total abolition of resistant pathogens. Here longer steaming times and larger steaming depths are necessary. Instead the focus is the killing of weed seeds on the surface in order to give beet cultures a headstart so they can prevail against other growing weeds.

The results show success. Despite short steaming periods, hot steam can sufficiently harm seeds sufficiently to avoid the penetration of weeds.

This steaming method for superficial seed control is further propagated in Germany as well. This development can be traced back to the lack of available alternatives. In earlier times chemical means were used which are meanwhile prohibited or considered risky.

Furthermore the present discussion about the spread of ragwort and similar plant types drives the promotion of steaming. The market demands even more weed=free products, but due to the market price situation there is no alternative for automatic harvest methods. Hence, beets need to be free of weeds when harvesting.

Steaming as ecological method for seed control gains importance nationally as well as internationally.

Steaming against weeds and weed seeds

Mittwoch, September 2nd, 2009

For more than 50 years the effect of heat on the germination capacity of weed seeds has been studied intensely.

Studies consider the effect on wet as well as dry seeds of different weed types, in which they were exposed to dry as well as humid heat such as hot steam for different durations. Studies made at the University of Zurich in the fifties of the last century showed clear results:

While dry heat did not yield a sufficient desired effect on seeds, humid heat such as hot steam ensured the complete killing of all seeds at 95°C after 5 minutes of treatment.

Dry heat even proved to be counterproductive: Germination capacity of weed seeds was even found to improve at times.
Hot steam showed to be the most thorough and effective means to treat against weed seeds and is superior to all other thermical methods as well has chemical herbicides, which are only partially effective against seeds.

The effect of heat in soil

Samstag, August 22nd, 2009

Each type of soil is a mixture of different components, in particular organic and mineral substances, which serve as biotope for many different organisms. Heat achieves a comprehensive effect: it has an impact on soil life and chemical, biological and physical processes. In the following there is a short list of the most important processes which are triggered by hot steam:

A) Biological and chemical impact:
Degeneration of organic material, in particular of structures based on proteins. Killing of organic and inorganic substances as well as solving of bound agents.

B) Physical impact:
Changing of soil structure, capillarity and the absorbency of salts and water, flushing and dissolution of chemical agents.

Research has shown that physical changes of soil are not very dependent on its specific composition. Notable are only the decrease of capillary flow conditions of water and a slight increase of siltation inclination. Both can be traced back to colloid structure changes. The acid-base metabolism of soil is not affected by heat.

The mentioned biological, chemical and physical effects have a direct impact on soil life and the growth of its plants. Diseases are fought and soil fatigue removed. After steaming many economic plants find better starting conditions and develop healthily.

Hot steam and plant growth

Samstag, August 22nd, 2009

Due to its composition and inherent organisms, soil has a fundamental impact on plant growth. For healthy development, seedlings depend on optimal growth conditions provided by soil. In particular intensely used horticultural soils have problems, since they amass many pathogenic organisms and substances.

Practical experiences of applying hot steam have shown that conservative methods of heating soil in general have a positive effect on plant growth. Hot steam has a physical, biological and chemical effect on intensely used soils and solves the majority of issues without chemicals.

Nevertheless until today not all effects of hot steam on each plant type is scientifically clarified in detail due to the complex dependencies between plant types and soil components.

In practice hot steam kills the majority of diseases and releases abundant nutrients, in particular nitrate, which is made available for plants in soluable form through condensation. After steaming plants are healthier: A culture shows more equality in growth and can be planted earlier in temperate zone, since soil is heated up and resting period is shorter in comparison to chemical usage. However there are exceptions where steamed soil can cause growth depressions e.g. with lettuce. The reason for which can not be clarified yet. It is assumed that in some soils the rate of nutrients has been negatively changed by heat. Normally soil born organisms compensate this effect. In steamed soil however it takes time until those organisms have resettled.

Hence it is recommended, in particular for sensitive cultures, to either wait two to four weeks before planting by extending the cooling period or – in order to cut down on the duration of the cooling period – to inject active beneficial micro organisms into the soil in order to facilitate and accelerate the recreation of soil equilibrium. Furthermore those beneficial organisms hinder pathogenic organisms to resettle in particular those coming from deeper soil layers which have not been steamed.