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Soil disinfestation microwave system as an alternative to methyl bromide

Final Report Summary - MICRODIS (Soil disinfestation microwave system as an alternative to methyl bromide)

In intensive agriculture and greenhouse management it is necessary to control pests, pathogens, weed seeds and nematodes that are present in the soil. The most common practice is to steam the soil, use various fumigants or exploit soil solarisation.

Conventional steaming systems can be inefficient, pollute the environment, are bulky and difficult to operate. On the other hand, fumigants are heavy pollutants and their use within the European Union has been prohibited. Methyl bromide in particular was identified as contributing to the depletion of the Earth's ozone layer under the Montreal Protocol of 1991. Nevertheless, there is currently no alternative technology to substitute methyl bromide in terms of effectiveness, applicability, low cost, ease of use, availability, worker safety and environmental safety below the ozone layer.

The objective of the MICRODIS project was to provide a viable alternative of methyl bromide through the development of a system for the fumigation of cultivation soil via electromagnetic radiation in the range of 950 MHz to 2450 MHz. The project scientific challenge was to design the microwave system so as to reduce energy consumption and associated costs while rendering it user friendly and as effective as possible in the elimination of pathogens and pests. In addition, the system should not affect the vital nutrients and organic matter of the soil which were necessary for crop growth.

Firstly, a market survey was carried out, using questionnaires and interviews, to ensure that the developed technology would be accepted and correspond to the market needs and price sensitivity. This survey helped to identify the MICRODIS general input requirements. In parallel, microbial life was investigated to provide the necessary biological information for the proposal development. A study of the most typical European soils was also performed to determine which soil parameters affected the proposed disinfestation method and how.

Secondly, soil samples were prepared, transported and stored in specific sealed boxes that controlled the temperature conditions. Alternative techniques, namely radio frequency (RF) and high electric field pulses, were investigated to improve the proposal's energy efficiency in comparison to conventional microwave radiation and resulted in the determination of prototype design rules. The development of microwave power of 18 kW was finally proposed and the generators and sensors for the process control were selected. Three experimental microwave cavities were subsequently prepared and characterised via extensive testing.

In addition, a soil selection machine was developed based on existing machinery and combined with a soil deposition system. Different security systems were implemented, as well as a system for speed control and a monitor to prevent the radiation of microwave escapes. The finalised system was capable to treat three to four tonnes of soil per hour using 20 kW of electric energy. After determining its technical and economical viability, a user guide that distilled non-confidential elements of the developed technology into a user friendly form was prepared. Finally, a knowledge dissemination plan was structured and applied to transfer the developed technology and know-how to the partner organisations and the general public.

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