Humic fertilizers by oxiammoniation of hydrolyzed olive pits residues

Abstract

Hydrolyzed olive pit residues from the production of furfural were ammoniated to obtain a nitrogenenriched humic fertilizer. Samples had been previously oxidized with nitric acid. The oxidized samples were further ammoniated in a batch reactor in the following range of experimental conditions: T = 80−210°C,$C_{HNO_3 } = 0.5 - 5.0 wt\%$, solid/liquid ratio, S/L = 0.5−2.8 w/w and reaction time, t = 1−4 h.

Planning of experiments was made by statistical design and results were fitted by multiple non-lineal regression polynomials. The product consists of two fractions: a water soluble fraction which contains most of the nitrogen (10−13 wt%) and a solid fraction with a very low nitrogen content (<4.0 wt%), which is likely to be fixed during the oxidation step. The soluble fraction can be used as a humic fertilizer and the solid product as a soil conditioner.