WHAT IS THE DIGESTATE?

As anaerobic digestion (AD) is quickly being harnessed in Italy and in other European countries, there is a need for a more in-depth description of the main by-product of the process, the digestate. Little information on digestate characteristics and composition is available and unclear legislation causes problems in biogas plant management. In this work, the organic matter (OM) of this matrix was described through chemical, biological, spectroscopic, and statistical approaches. It was shown that AD results in a strong reduction of the easily degradable fraction of the OM and an accumulation of recalcitrant molecules (possible humus precursors). This contributes to a relatively high biological stability of the residual OM content in the digestate and may lead to good amendment properties. Besides, the observed relative accumulation and the high mineralisation of nitrogen and phosphorus may point to the digestate as a readily available liquid fertiliser for agronomic use. Moreover, xenobiotics and pathogens respected limits for both biosolids and compost in Italian and European legislation

Evaluating inhibition conditions in high-solids anaerobic digestion of organic fraction of municipal solid waste

High-solids anaerobic digestion (HSAD) processes, when applied to different types of organic fractions of municipal solid waste (OFMSW), may easily be subjected to inhibition due to organic overloading. In this study, a new approach for predicting these phenomena was proposed based on the estimation of the putrescibility (oxygen consumption in 20 h biodegradation, OD20) of the organic mixtures undergoing the HSAD process. Different wastes exhibiting different putrescibility were subjected to lab-scale batch-HSAD. Measuring the organic loading (OL) as volatile solids (VS) was found unsuitable for predicting overload inhibition, because similar VS contents corresponded to both inhibited and successful trials. Instead, the OL calculated as OD20 was a very good indicator of the inhibiting conditions (inhibition started for OD20 > 17\u201318 g O2 kg^(-1)). This new method of predicting inhibition in the HSAD process of diverse OFMSW may be useful for developing a correct approach to the technology in very different contexts

Prospective, observational, multicenter study on minimally invasive gastrectomy for gastric cancer: robotic, laparoscopic and open surgery compared on operative and follow-up outcomes - IMIGASTRIC II study protocol: IMIGASTRIC II

Background:Several meta-analyses have tried to defi ne the role of minimally invasive approaches. However, further evidence to get a wider spread of these methods is necessary. Current studies describe minimally invasive surgery as a possible alternative to open surgery but deserving further clarifi cation. However, despite the increasing interest, the difficulty of planning prospective studies of adequate size accounts for the low level of evidence, which is mostly based on retrospective experiences.A multi-institutional prospective study allows the collection of an impressive amount of data to investigate various aspects of minimally invasive procedures with the opportunity of developing several subgroup analyses.A prospective data collection with high methodological quality on minimally invasive and open gastrectomies can clarify the role of diff erent procedures with the aim to develop specifi c guidelines.Methods and analysis:a multi-institutional prospective database will be established including information on surgical, clinical and oncological features of patients treated for gastric cancer with robotic, laparoscopic or open approaches and subsequent follow-up.The study has been shared by the members of the International study group on Minimally Invasive surgery for GASTRIc Cancer (IMIGASTRIC)The database is designed to be an international electronic submission system and a HIPPA protected real time data repository from high volume gastric cancer centers.Ethics:This study is conducted in compliance with ethical principles originating from the Helsinki Declaration, within the guidelines of Good Clinical Practice and relevantlaws/regulations.Trial registration number:NCT0275108

The contribution of water soluble and water insoluble organic fractions to oxygen uptake rate during high rate composting

This study aims to establish the contribution of the water soluble and water insoluble organic fractions to total oxygen uptake rate during high rate composting process of a mixture of organic fraction of municipal solid waste and lignocellulosic material. This mixture was composted using a 20 l self-heating pilot scale composter for 250 h. The composter was fully equipped to record both the biomass-temperature and oxygen uptake rate. Representative compost samples were taken at 0, 70, 100, 110, 160, and 250 h from starting time. Compost samples were fractionated in water soluble and water insoluble fractions. The water soluble fraction was then fractionated in hydrophilic, hydrophobic, and neutral hydrophobic fractions. Each fraction was then studied using quantitative (total organic carbon) and qualitative analysis (diffuse reflectance infrared spectroscopy and biodegradability test). Oxygen uptake rates were high during the initial stages of the process due to rapid degradation of the soluble degradable organic fraction (hydrophilic plus hydrophobic fractions). Once this fraction was depleted, polymer hydrolysis accounted for most of the oxygen uptake rate. Finally, oxygen uptake rate could be modeled using a two term kinetic. The first term provides the oxygen uptake rate resulting from the microbial growth kinetic type on easily available, no-limiting substrate (soluble fraction), while the second term considers the oxygen uptake rate caused by the degradation of substrate produced by polymer hydrolysis

Estimating biogas production of biologically treated municipal solid waste

In this work, a respirometric approach, i.e., Dynamic Respiration Index (DRI), was used to predict the anaerobic biogas potential (ABP), studying 46 waste samples coming directly from MBT full-scale plants. A significant linear regression model was obtained by a jackknife approach: ABP=(34.4 +/- 2.5) + (0.109 +/- 0.003). DRI. The comparison of the model of this work with those of the previous works using a different respirometric approach (Sapromat-AT(4)), allowed obtaining similar results and carrying out direct comparison of different limits to accept treated waste in landfill, proposed in the literature. The results indicated that on an average, MBT treatment allowed 56% of ABP reduction after 4 weeks of treatment, and 79% reduction after 12 weeks of treatment. The obtainment of another regression model allowed transforming Sapromat-AT(4) limit in DRI units, and achieving a description of the kinetics of DRI and the corresponding ABP reductions vs. MBT treatment-time. (C) 2009 Elsevier Ltd. All rights reserved