Carbon Sequestration by Composting around Mount Etna Latvian State Forest Research Institute “Silava” Institute of Sustainable Development of Landscapes of the Earth e.V. (DUENE) Naturland e.V. Agricultural Institute of Slovenia Institute of Field and Vegetable Crops Manfred-Hermsen-Stiftung Danube Delta National Institute for Research and Development (DDNI) “Green Jackets” Bronte National Research and Development Institute for Soil Science, Agrochemistry and Environment Bucharest (ICPA)