Composting of Organic Garden and Kitchen Waste in Open-air Windrows: Influence of Turning Frequency on the Development of Aspergillus Fumigatus

Composting at industrial scale (installations treating. 100 tons per year) is increasingly used in Switzerland for the stabilization of organic waste and the recycling of humigenic materials. In 1992, 320.000 tons of garden and kitchen waste were treated in 150 composting sites, 80% thereof treating more than 1.000 t/a (1). Even if mature composts are generally of satisfactory quality, the process itself could often be considerably improved. Our research team is currently involved in a threeyear study that aims at optimizing the thermogenic phase of composting processes, in order to ensure a good thermo-hygienization (elimination of allergenic and pathogenic micro-organisms, e.g. the thermotolerant mold Aspergillus fumigatus) and to improve the number and diversity of the thermophilic micro-organisms. This will lead to a rapid degradation of the organic material. By this, phytotoxicity hazards can also be avoided.