Composting of green waste: observations from windrow trials and bench-scale experiments

The composting of green waste is currently of great importance to the waste industry. For this reason, large-scale compost windrows were investigated and the results compared with those from small, bench-scale experiments. In the two windrows sampled, temperature profiles differed, and greater organic matter loss was observed in the higher temperature windrow. However, enhanced organic matter degradation through elevated temperatures was not supported in the bench-scale experiment, where, under fixed temperatures (30 and 50 degrees C, respectively), no difference in both the total dry and organic matter content was observed. Analysis of particle size distributions in both sets of experiments strongly suggested that moisture-dependent effects were a confounding factor in determining the total LOI of the windrows. Analysis of beta-glucosidase activity in the bench-scale samples demonstrated that it was the assay temperature, rather than the in situ composting temperature, which was more important in determining the level of activity. No evidence for adaptation to local maxima due to variation in the thermal environment was observed.