SEBASTIAN HEDEL1, JOACHIM CLEMENS2, UTE ARNOLD3
1University of Halle-Wittenberg, Germany
2University of Bonn, Institute of Plant Nutrition, Germany
3University of Can Tho, Center of Environmental Engineering and Renewable Energy, Vietnam
In the Mekong-Delta, pig production is one major income source of farmers. The piggeries are small (3-5 sows) and the pig excrements are disposed directly to fields or into ponds or canals. Without treatment of the excrements soil or water may be polluted by pathogens originating from pig excrements.
Composting may be a way to sanitise the excrements by heat. In this study we composted pig excrements and investigated the sanitation and decomposition potential. In 100 litre basket ca. 90kg substrate were treated. The substrates were pig droppings without additive, pig droppings with straw addition at two levels and anaerobically pretreated pig excrements. During eight weeks we monitored temperature, moisture, nitrogen and carbon content, organic dry matter as well as coliforms and E. coli. Weekly the substrates were mixed and total mass was recorded to calculate a mass balance.
Additionally nitrous oxide emissions were analysed during the maturing phase when N2O emissions were most likely. While the maximum temperature in the anaerobically pretreated substrate was less than 50°, the other substrates showed temperatures as high as 69°C indicating a good sanitation of these substrates. Pig excrements showed the highest temperatures, although this material had the poorest structure. This indicates that oxygen diffusion into the substrate and heat transport out of the substrate, both influenced by the structure of the material, need to be well balanced in small scale composting systems.
The mass balance, C- and N-losses will be presented in the presentation; at the moment these parameters are analysed.
Keywords: Biogas sludge, closing nutrient cycles, composting, Mekong-Delta, pig excrements, Vietnam