Agricultural activities produce an estimated 32.7 MToe/year of waste in EU countries. Most of it is disposed of in landfills, incinerated without any control or abandoned on the fields, causing serious impacts on human health and the environment. Rice is one of the most widely consumed crops worldwide, with an annual production of 782 million tonnes, according to the Food and Agriculture Organisation database. In this context, the LIFE LIBERNITRATE project, funded by the European Union, promotes the use of renewable waste sources (i.e. rice straw) to obtain new materials with added value. The methodology is based on the incineration of rice straw in a recovery system of own design and construction. The rice straw and wood pellets are burned under conditions optimised to produce a maximum amount of ash with a high silica content. These materials will then be used to treat water contaminated with nitrates, which represents an optimal example of a circular economy strategy. This paper describes the recovery unit of our own design, with special attention to its main constituent elements. The theoretical study of the co-incineration of rice straw and wood pellets made it possible to identify the optimised combustion conditions. The experimental tests carried out with the theoretical inputs confirmed the most suitable operating conditions (10 g of rice straw pellets/min + 10 g of wood pellets/min, 6-7 Nm3/h of air, T = 500 ◦C) and helped to define the improvements in the experimental plant.

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