Abstract

In the caustic process from kraft cellulose pulp industry, solid wastes with alkalines properties named dregs (D) and grits (G) are obtained. Nowadays, both types of wastes are deposited in industrial weirs, and this generates an economic and environmental problem. In this work the main uses of these wastes are summarised, and it is studied its particular application to degraded soils. Therefore, main objectives are: to quantify D&G production, its characterisation and to study their leaching, compaction properties and pH correction effect, when they are applied in different concentrations to acid soils. D&G characterisation shows that they do not present reactivity, corrosion and flammability properties and therefore, they are not toxic. Besides, granulometry characteristics, pH (12, 76), Ca (26,5%), Mg (1,5%), p (0,28%) and K (0,20%) contents, between others, confirm their potential use in degraded soils for possible agricultural uses. It has been studied the behaviour of a series of continuous columns during 86 days, with different soils and a dose of 5 g/kg of D&G (1:1) equivalent to 2 g/kg of lime, applied to degraded soils (acid). Nutrients leached in the different columns were evaluated. Finally, the substrate characteristics in each column were evaluated and it was concluded that physical and chemical properties in acid soil had been improved with the addition of D&G.