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FP5

AGROIWATECH Informe resumido

Project ID: ICA2-CT-2002-10010
Financiado con arreglo a: FP5-INCO 2
País: Serbia

Stabilised sludge from agro-industrial wastes that can be used as land conditioner or fertilizer in agriculture or forestry

The objectives were to determine the possibilities for using stabilised sludge, obtained from the anaerobic treatment of solid waste from the agro-industry (brewery, sugar factory and edible-oil refinery), in agriculture and forestry, to fertilize and/or condition the soil.

For the investigation into the possibilities of applying anaerobically stabilised sludge, and anaerobically stabilised sludge post-stabilised by the addition of CaO from the chosen agro-industries, humus-poor soil of acidic character was obtained from a private farm near Novi Sad. Soil with these characteristics was chosen for investigation based on the fact that in Vojvodina (northern province of Serbia), the total area of this soil type is 1412 ha. pH was taken as the key factor in the evaluation of the maximum amount of the investigated sludges which can be applied to the soil chosen for the experiment, considering the alkaline characteristics of the sludge.

By simulating rainfalls during the experiment, significant washing-out effects were observed on the nutrient content (above all nitrogenous matter) of the investigated soils. Because of its alkaline characteristics (pH 7.45-12.78), all of investigated anaerobic sludges (with and without post-stabilisation by CaO addition), can be successfully applied as a soil conditioner (the addition of 2.8-6.7% sludge to the soil results in a pH correction of 1.24-2.21 pH units in the soil).

The effects of the application of this sludges as a fertilizer resulted in an increase in nitrogenous matter content by 6-23% and phosphorous by 38-25%, depending of the applied slude on soil, and also leads to a reduction in the washing-out of these compounds during heavy rainfall. Besides that, based on the C/N ratio (which decreases), this sludge leads to soil stabilisation from a nutritional content aspect.

Comparison of the results for the application of anaerobically stablised sludge as a soil conditoiner and fertilizer, with respect to its effect on the pH of the soil and the content of useful materials, shows that all the investigated sludges are efficient pH correctors, but the highest-quality sludge in respect to increasing nitrogen matter content in soil was the sludge obtained by digesting solid brewery waste, and from the aspect of phosphoruos matter content the sludge obtained from edible oil refinery waste.

As fertilizers, slugdes post-stabilised by adding CaO increase the nutrient content and nutrient retention of the soil, but application of post-stabilised edible oil refinery slude is limited by its reduction of the water permeability of the soil, due to its quagmire- inducing effects.

Reported by

University of Novi Sad
Trg Dositeja Obradovica 3
21 000 NOVI SAD
Serbia
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