Monitoring respiration and biological stability during sludge composting with a modified dynamic respirometer

A static electrolytic respirometer was adapted to work under dynamic conditions using an internal airflow recirculation system that passed air through sludge/straw solid mixtures. Airflow reduced oxygen transfer limitations and increased the maximum respiration rate and k_La values, indicating that the observed value may have been close to the actual biodegradation rate. Airflow caused sludge drying, so the sample moisture was controlled by air humidification. To apply the optimised respirometric technique, a pilotscale composting process was developed. Some commonly used respiration indices (RI₂₄, AT₄) were used to measure the final compost stability. RI₂₄ indices without airflow were underestimated during the thermophilic composting stage. Once the easily biodegradable carbon was consumed, the static and dynamic RI₂₄ indices were nearly identical. Because of the dynamic procedure, the respiration rate was likely controlled by the biochemical reaction and not by the mass transfer. The respiration indices indicated that the final compost was unstable.     

Novel static composting method for bioremediation of olive mill waste

This paper presents results obtained on the evaluation of static composting process aimed at bioremediation of the hazardous solid olive mill waste (OMW). The static composting process carried out in gas-permeable polyethylene bags followed the fluctuating temperature and oxygen profiles similar to those seen in aerated composting systems. Static composting resulted in apparent increases and decreases in values for total nitrogen and C:N ratios respectively during the process. The amount of nitrogen (>3%) in the composting end product was in agreement with the Italian legislation (Decreto Legislativo 29 aprile 2010, n. 75) specification for nitrogen fertilizer. A gradual decrease in polyphenols during the storage of compost resulted in a non-phytotoxic composted organic matter high in humic substances. Different respirometric tests also stated high biological stability of the end compost product.     

Source separation,selective collection and in reactor digestion of biowaste

Biowaste or the organic fraction of domestic waste, for instance kitchen, fruit and garden waste, is collected selectively in several European communities. The complementary fraction is called the dry or non recyclable fraction. A Dutch study reported that 92% of the participants that have a weekly collection service of both fractions (biowaste and non recyclable fraction) and 80% of the participants in the alternating collection program (one week biowaste and the next week non recyclable fraction) are pleased with separate collection of biowaste. Dominating problems that arise in case of alternating collection are a repulsive odor and an infestation with flies and maggots. By expanding the definition of biowaste to include non recyclable or soiled paper like dirty newspapers, table napkins and paper handkerchiefs, most of these problems can be overcome without changing the way compostable waste is collected and processed. The expanded definition of biowaste was used in this paper. Over a 12 month period a quality survey of the collected biowaste was conducted by the composting facility Intercompost, Hoeselt, Belgium. A special aspect was the fact that in one participating community baby diapers were included in the soiled paper fraction; this is called biowaste+. The biowaste+ had a 10% non recyclable paper fraction opposed to only 1–2% of non recyclable paper present in the conventional biowaste. Baby diapers were a rather notable part (more than 80%) of this non recyclable paper fraction of biowaste+ and as a consequence might contribute to a large extent to improve the collection and treatment of biowaste. It was demonstrated that rural districts yielded about 35% more biowaste than more urban districts; resp. ± 122 kg biowaste/capita.year versus ±90 kg biowaste/capita.year. In Hoeselt the biowaste+ yield was about 130 kg/capita.year. Biowaste+ is also separately collected in another Belgium community, namely Brecht. The purity level of the biowaste+ and the amount of non recyclable paper (including diapers) were comparable with the results of Hoeselt. In Hoeselt the biowaste+ fraction is composted aerobically. In Brecht on the other hand, the biowaste+ is processed using the Dry Anaerobic Composting process (DRANCO). The latter process is discussed in more detail. The biological start-up of the dry anaerobic composting installation at Brecht, Belgium, is reported. The reactor has a total volume of 808 m³ and a design capacity of 730 m³. After 2 months of start up, the fermentor was at full loading rate, i.e. 8 kg bVS/m³ _reactor .day and the installation was working at full capacity, i.e. 40 ton/day. After 1 year of full-scale operation, the installation can handle peak loads of 60 ton/day. The average biogas production is 107 m³/ton with an average methane content of 55%. This corresponds to an annual gross energy production of approximately 600 toe (ton oil equivalent). The average biogas production rate is 4.0 m³/m³ _reactor .day. The end product of the aerobic process in Hoeselt and the end product in Brecht, the Humotex, are of similar composition. Both are of high quality and are sold as a soil conditioner or as a potting substrate. However, the double processed compost has a garanteed hygienic quality which makes it a product suitable for export.     

Efforts to Explain and Control the Prolonged Thermophilic Period in Two-phase Olive Oil Mill Sludge Composting

The aim of this paper was to evaluate the use of different bulking agents in different ratios as a means to control, optimise and eventually reduce the duration of the thermophilic period in two-phase olive oil mill sludge (OOMS) composting. The bulking agents used were: (i) olive tree leaves (OTL), (ii) olive tree shredded branches (OTB) and (iii) woodchips (WDC). The selection of these materials was based on their abundance and availability on the island of Crete, the southernmost point of Greece. The ratios studied were: Pile 1, OOMS:OTL in 1:1 v/v; Pile 2, OOMS:WDC in 1:1.5 v/v; Pile 3, OOMS:OTL in 1:2 v/v; Pile 4, OOMS:OTL:OTB in 1:1:1 v/v; and Pile 5, OOMS:OTL:OTB in 1:1:2 v/v. The composting system used was that of windrows with the volume of each pile approximately 20–25 m³. The experiments took place over two consecutive years. A composting turner was used and turnings were performed at one and two week intervals. In each pile a variety of physiochemical parameters were monitored. Temperature remained high in all five trials. Piles 1, 2, 3, 4 and 5 temperatures recorded values of above 50 °C for 106, 158, 160, 175 and 183 days, respectively. Volumes were reduced by approximately 67%, 62%, 63%, 80% and 84%, respectively. Temperature remained high, mainly due to the presence in large amounts of oily substances which during their complete oxidation release important amounts of energy and aid the cometabolism of more stable molecules such as lignin. This process is better described as the slow “burning” of a “fuel” mixture in an “engine” than composting. This approach is based on the extensive similarities of this process to that of crude oil sludge or similar waste composting.     

The Use of the Microcomposter to Study the Dynamics of a Mini-Ecosystem

In this activity, students learn about the important topic of invasive species, specifically Zebra Mussels. Students role-play different characters in a real-life situation: the trial of the Zebra Mussel for unlawful disruption of the Great Lakes ecosystem. Students will also learn about jurisprudential inquiry by examining the trial process. This activity will reinforce important knowledge and skills underscored in the Life Science and Science in Personal and Social Perspectives Standards in the National Science Education Standards (National Research Council 1996).     

Utilization of Bacillus sp. strain TAT105 as a biological additive to reduce ammonia emissions during composting of swine feces

Bacillus sp. strain TAT105 is a thermophilic, ammonium-tolerant bacterium that grows assimilating ammonium nitrogen and reduces ammonia emission during composting of swine feces. To develop a practical use of TAT105, a dried solid culture of TAT105 (5.3 × 10⁹ CFU/g of dry matter) was prepared as an additive. It could be stored for one year without significant reduction of TAT105. Laboratory-scale composting of swine feces was conducted by mixing the additive. When the additive, mixed with an equal weight of water one day before use, was added to obtain a TAT105 concentration of above 10⁷ CFU/g of dry matter in the initial material, the ammonia concentration emitted was lower and nitrogen loss was approximately 22% lower in the treatment with the additive than in the control treatment without the additive. The colony formation on an agar medium containing high ammonium could be used for enumeration of TAT105 in the composted materials.     

微生物在有机固废堆肥中的作用与应用

好氧堆肥是实现有机固体废弃物资源化利用的主流处理方式.堆肥腐熟是一个由微生物主导的生理生化过程,堆料通过微生物发酵实现矿质化、腐殖化和无害化,转变成腐熟的有机肥.传统的好氧堆肥存在发酵周期长、养分损失、恶臭及温室气体排放等不足.在堆肥过程中添加微生物是弥补传统好氧堆肥缺陷、提高堆肥品质和功效的有效方法.近年来,国内外在...     

堆肥微生物学研究现状与发展前景

综述了有机固体废弃物堆肥微生物学的研究方法的最新进展,以及堆肥过程中微生物的研究现状,提出了堆肥微生物学研究存在的主要问题和发展趋势。