Microbiological and chemical characterization during composting of cattle manure and forestry wastes – a case study in Madeira Island

摘要

Large quantities of forestry wastes are produced every year in Madeira Island, as well as appreciable quantities of cattle manure. The composting of these two otherwise landfilled wastes, is therefore an important recycling option that will reduce their environmental impact. The main objective of this work was to study the dynamic of several physical-chemical parameters during the composting of cattle manure and forest residues, as well as the quantitative and qualitative characterization of the microbial populations, which are responsible for the biodegradation of the materials used. The composting trials were performed in piles using several turning frequencies. The results indicate that the turning frequencies had a significant effect on the evolution of the operational parameters, especially on temperature, O_2 and CO_2 contents, moisture, electrical conductivity and, nutrient availability. Losses of nitrogen by volatilization of ammonia were not detected, and therefore, we could obtain composts with high nitrogen levels. The microorganisms identified are in agreement with the evolution of the operational parameters followed, especially the nitrogen dynamics. The identification of free-living nitrogen fixing bacteria, as well as, autotrophic and heterotrophic nitrifying bacteria, allowed us to justify the high nitrogen concentrations found in the composts. The biodiversity indexes showed that the composts reached biological stabilization.