Jordi Valero

Bulk density determination as a simple and complementary tool in composting process control.

Ten composting facilities (CF) treating source-sorted organic fraction of municipal solid waste (OF) were sampled to study the relationship between the bulk density and the composting process (CP) development. Hundred and fourteen samples from different stages of the CP were considered (organic fraction, initial mixture, final decomposition, final maturation and compost), including the reject materials coming from the densimetric table at postprocessing. Total organic matter (TOM), moisture content (MC), wet bulk density and dry basis (BDd) were determined. Significant differences were detected for MC, TOM and BDd between some stages of the CP. The BDd increased along the CP while TOM decreased. Correlation studies showed a significant negative relationship between TOM and bulk density, especially BDd, during the CP, as a result of the biological activity. Moreover, a clear relationship was also found between TOM and BDd in samples related to reject materials. The results indicate that bulk density could be a simple and useful tool to evaluate the CP, in addition to the others parameters commonly used. At the same time, BDd could be an easy way to infer TOM lost within rejects.

On zero-truncating and mixing Poisson distributions

The distributions that result from zero-truncating mixed Poisson (ZTMP) distributions and those obtained from mixing zero-truncated Poisson (MZTP) distributions are characterised based on their probability generating functions. One consequence is that every ZTMP distribution is an MZTP distribution, but not vice versa. These characterisations also indicate that the size-biased version of a Poisson mixture and, under certain regularity conditions, the shifted version of a Poisson mixture are neither ZTMP distributions nor MZTP distributions.

On left-truncating and mixing Poisson distributions

ABSTRACT The distributions obtained by left-truncating at k a mixed Poisson distribution, denoted kT-MP, and those obtained by mixing previously left-truncated Poisson distributions, denoted M-kTP, are characterized by means of their probability generating function. The main consequence is that every kT-MP distribution is a M-kTP distribution, but not the other way around.

Education and research related to organic waste management at agricultural engineering schools

Purpose – The purpose of this paper is to describe the experience of the Agriculture Engineering School of Barcelona (ESAB), where undergraduate students were involved in field research experiments on organic waste use in agricultural systems.Design/methodology/approach – The paper outlines how the formation of professionals oriented to work for OWM companies has been successfully promoted.Findings – Agricultural systems can assimilate self‐produced organic wastes (OW) and others from different sources. Their management for crop production can generate enormous economic and environmental benefits which can contribute to sustainable development. The implementation of an integrated strategy for OW treatment (OWT) and management (OWM) must be adapted to the characteristics of the specific geographical region and must consider the interrelations among diverse subjects such as: soil science, fertilizer management, plant production, animal husbandry, farm machinery, climate and culture.Practical implications – ...