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Location: Quality & Safety Assessment Research

Title: A Half Century of Research on Agricultural Applications for RF and Microwave Dielectric Heating

item Nelson, Stuart

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Proceedings
Publication Acceptance Date: 6/22/2011
Publication Date: 8/7/2011
Citation: Trabelsi, S., Nelson, S. 2011. A Half Century of Research on Agricultural Applications for RF and Microwave Dielectric Heating. American Society of Agricultural and Biological Engineers. ASABE Paper Number:110849.

Interpretive Summary: Radio-frequency and microwave dielectric heating are processes that offers unique features for many industrial applications, so they have been explored for possible uses in agriculture over the past 50 or 60 years. In this paper, the fundamental principles of dielectric heating are summarized, and many applications are identified for reference that have been explored for radio-frequency dielectric heating at frequencies from 1 to 40 MHz and at microwave frequencies of mainly 915 and 2,450 MHz. These include applications of radio-frequency and microwave energy for grain and forage drying, treatments to enhance nutritional value or qualities of agricultural products, seed treatment to improve germination and seedling development, treatments for stored-grain insect control, soil treatment for insect and weed control, treatment to control insects infesting fruit and nuts, and seed treatment to control plant fungi and human pathogens. Most of these applications have not yet been accepted for practical use, and the economic reasons for this are considered. Discussion is also included on applications that may warrant further consideration. The high costs of lower frequency RF and microwave dielectric heating equipment with capacities great enough for practical-scale drying of most agricultural commodities and the energy costs for operation have been too great for serious consideration to be given for practical use. For the same reasons, practical use of dielectric heating for controlling insects infesting agricultural products has not been developed for practical application. Economically, the application of RF and microwave dielectric heating for treatment of seed appears more likely to be practical than other agricultural applications, because seed is a high-value commodity and generally much smaller quantities need to be handled. Therefore, equipment would not have to deliver such large amounts of RF power and equipment costs might be more manageable. As with any commercial development, the benefits of new processes need to be evaluated in relation to costs and marketing considerations. Improved quality attributes of some products as a result of dielectric heating processes might justify the expenses associated with the RF and microwave power equipment and its operation if the competitive advantages are sufficient. The value of time saved with the faster processes and total energy requirement comparisons are other factors that need to be considered. Research conducted on the potential use of RF and microwave dielectric heating for a large number of agricultural applications over the past half century has answered many questions that arise in the consideration of such applications. Hopefully, the identification of many of these sources of information on the research studies will be helpful to those considering new applications of dielectric heating for the solution of problems with agricultural products.

Technical Abstract: Basic principles of radio-frequency and microwave dielectric heating are presented, and research reports and reviews published over the past 50 or 60 years are identified for various dielectric heating applications that have been explored for potential use in the field of agriculture. Included are applications for grain and forage drying, treatment to improve nutritional value of products, seed treatment to improve germination, treatments to control stored-product insects, soil treatment for weed control, and seed treatment for control of plant pathogens and human pathogenic bacteria. Economic reasons for lack of practical use and requirements for development of potential practical applications are discussed.