Recovery of waste biomass in nurseries

The nursery sector in Europe involves 90,000 ha of potted cultivations and 120,000 ha of open land and greenhouse cultivations valued at 19.8 billion Euros in 2011. Every year, nurseries waste approximately 4 kg of residual biomass for each 1 m2 of potted plant cultivation; thus, a mechanical optimization of the operations for treating this biomass is required. Several studies have analyzed the environmental impacts associated with nurseries, recommending best practices for waste recycling or reuse. Therefore, the present work focused on the evaluation of possible solutions for the reuse of residual biomasses, such the wood and substrate of potted plants that are discarded from the nursery production chain. Considering that the reuse of these residual materials is much more feasible if they can be separated, two different shaker heads were tested on two ornamental trees species [the Atlas cedar (Cedrus Atlantica Glauca Pendula) and the Leyland cypress (Cupressocyparis Leylandii)]. The analysis of the machines’ performance (e.g., shaking efficiency, working times, fuel consumption, operative capacity) suggested that the shaking time is not correlated with the shaking efficiency, large-sized shaker heads are more profitable for larger trees, and extended shaking is not practical using small-sized machines. In addition, accelerations of the shaker heads were measured during the tests, and a spectral analysis of their temporal evolution was conducted. The results showed that shaking efficiency is related to shaking frequency, associated with the machine’s capability to tune to the system resonance frequencies.