BIOTECHNOLOGY - V. H. Herasymenko - 2006

Part II. Special Biotechnologies

Chapter 22. BIOTECHNOLOGIES FOR WASTE UTILIZATION AND BIOCONVERSION IN THE AGRO-INDUSTRIAL COMPLEX

22.2. METHODS OF MANURE UTILIZATION

22.2.1. Traditional methods. Use of manure as an organic fertilizer

The most widespread method of manure utilization is its application to improve soil fertility. This is due to the fact that dry manure matter contains significant amounts of nitrogen (1.9-6.5 %), potassium (1.0-2.9 %), phosphorus (0.2-2.7 %), and organic matter (70-85 %). A standard unit of organic fertilizer is defined as one ton of untreated liquid manure, which, after Processing (prior to soil application), contains 35-40 % dry matter, 0.05 % nitrogen, 0.25 % phosphorus, and 0.6 % potassium. In addition, manure is a source of humus, the primary factor in soil fertility. On average, 1 t of manure yields 40-50 kg of humus. Therefore, manure has a positive effect on soil fertility, physicochemical, agrophysical, and biological properties. As a source of macro- and microelements as well as carbon dioxide, manure significantly improves the nutrient balance in the soil. Applying manure to the soil substantially increases its energy capacity, which is one of the factors promoting higher yields of terrestrial biomass per unit of land area, as well as enhancing the synthetic activity of autotrophic microorganisms.

This method is primarily used for utilizing the solid fraction of manure (farmyard manure) with a moisture content not exceeding 70 %. It is stockpiled in specialized areas for accumulation, quarantine, and biothermal disinfection. The biothermal method relies on generating high temperatures (60 ^oC) within the disinfected mass and maintaining them for one month during the warm season and two months during the cold season. If the manure moisture content exceeds 70 %, the Treatment period must be extended to 5-6 months. Afterward, the manure is hauled to the fields for plowing under.

In the soil, organic substances from manure are transformed by autotrophic microorganisms and other biological agents (earthworms, Arthropods). Inorganic substances are adsorbed by soil particles or precipitated, but they do not break down. Heavy metals are particularly hazardous in this regard, and therefore their concentrations in the soil are strictly regulated.

Liquid manure (untreated cattle manure and slurry from pig-breeding complexes) is first separated in settling tanks into a solid fraction and a liquid fraction or wastewater. The solid fraction is stockpiled for biothermal disinfection and used as an organic fertilizer.

The liquid fraction is also utilized as a liquid organic fertilizer for irrigating crops. Irrigation with wastewater ensures its natural soil-based post-treatment, creating favorable conditions for environmental protection.

The widespread adoption of this method is hindered by sanitary-hygienic and economic requirements. For instance, pathogenic microorganisms present in manure biomass can persist in the external environment for a long time and may trigger human epidemics and animal epizootics. Ensuring veterinary and sanitary safety in this case requires waste disinfection via high-Temperature thermal sterilization, which is an energy-intensive Procedure.

Significant economic challenges are associated with the costs of removing, transporting, storing, and applying manure in crop production, as well as disinfecting it through thermal sterilization to ensure veterinary and sanitary safety.