Carbon Mineralization of Pruning Wastes Compost At Different Stages of Composting

Compost Science & Utilization, (2005), Vol. 13, No. 3, 203-207

Marta Benito, Alberto Masaguer, Ana Moliner and Roberto De Antonio

Departamento de Edafología, Escuela Técnica Superior de Ingenieros, Agrónomos, Universidad Politécnica de Madrid, Madrid, Spain

To study the carbon mineralization of pruning waste compost, four samples originated from pruning waste, leaves and grass clippings were collected each from a different pilot pile at different stage of the composting process: initial nondecomposed material (C1); two-months old at the end of the biooxidative stage (C2); seven months old during the curing phase (C3) and 12 months old at the end of the curing phase (C4). The CO2-C evolution was measured during 56 days of aerobic incubation. The proportion mineralized from the different composts (% of compost TOC) during the incubation period were: 4.54, 2.43, 1.71 and 1.60 for C1, C2, C3 y C4, respectively. Regardless of compost age, C mineralization occurred in two phases: a first rapid phase (corresponding to the decomposition of the most labile products by microorganisms) and a second, slower phase, during which the most resistant organic products mineralized. During the first stage, the model was fitted to a first-order equation, whereas in the second phase the model was a zero-order equation. Because of the similar results obtained for samples C3 and C4, we can conclude that organic matter had similar microbial stability at both stages and the composting process could be shortened by five months.

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