Changes in the chemical composition of water-extractable organic matter during composting: distribution between stable and labile organic matter pools

Aerobic decomposition and stabilization of organic matter during the composting of waste materials is primarily due to the biochemical transformation of water-soluble compounds in the liquid phase by the microbial biomass. For this reason water-soluble organic matter represents the most active fraction of compost, both biologically and chemically, and thus should directly reflect the biochemical alteration of organic matter. This work aims to elucidate the microbial-mediated processes responsible for the distribution of soluble organic matter between stable and labile pools with composting time. Accordingly, chemical analysis as well as UV absorption, and ¹H and ¹³C-NMR spectroscopy of samples collected during the industrial composting of urban waste revealed microbial induced transformation of water-extractable organic matter over time. The chemical composition changed from labile, hydrophilic, plant-derived organic compounds in the beginning to predominately stable, hydrophobic moieties comprising lignin-derived phenols and microbially-derived carbohydrates at later stages of composting.     

Factors affecting the degradation of amoxicillin in composting toilet

The biological and non-biological factors that affect the degradation of amoxicillin in the composting process of feces have been investigated. The effect of living bacteria and the enzyme (beta-lactamase) on amoxicillin decay was examined, and our results indicated that the biological effects are likely to be negligible. Consequently, the effect of phosphate, ammonia and pH level as non-biological factors was investigated by monitoring the reduction rate of amoxicillin in phosphate and ammonia buffer solutions with several pH levels. Each reduction rate constant was integrated by a simulation model, and the each calculated amoxicillin reduction profile was compared to the reduction profiles of amoxicillin in the composting process of feces. The calculated results corresponded almost exactly to the experimental profiles. We therefore concluded that the degradation of amoxicillin in a toilet matrix was dependent on the concentration of ammonia, phosphate and hydroxyl ion.     

推进厕所革命需要解决的技术问题及措施建议

厕所问题是当前城乡发展不平衡与不充分的最直接体现。推进厕所革命是一项系统工程,不仅对材料、能源、环保、建筑等产业技术提出新的要求,也是生态文明建设关键一环,涉及生态环保、卫生健康、乡村建设、文明进步、可持续发展等多重目标。近年来,我国开展大量农村厕所整治工作,取得阶段性重要成果,但在厕所系统性、理念意识、安全舒适、技术适应性等方面仍有差距。建议围绕厕所革命的阶段性多目标要求进行系统部署,以整体提升厕所系统的环保卫生、安全舒适、经济持续性为核心,准确把握技术创新发展路径,增强多技术方案供给和商业模式选择,增强农民群众在乡村振兴中的获得感。     

旅客列车真空集便器便盆冲洗排空影响因素及相关技术研究

旅客列车真空集便器便盆污物冲洗排空效果受诸多因素影响,各影响因素间相互作用.为实现以较低冲洗水量达到良好冲洗排空效果、提高系统洁净性能,对便盆曲面、冲洗流型进行分析设计,对旋流和扇面2种不同冲洗流型特点进行比较,分析不同设计参数及安装位置对冲洗排空效果的影响,最终通过试验研究验证冲洗喷嘴的安装位置、旋流喷嘴的射流方向等...     

粪便与生活垃圾混合堆肥氮转化与腐熟度

采用静态仓强制通风进行粪便和生活垃圾混合堆肥,以玉米秸和石灰为调理剂,考察堆肥过程的氮转化与腐熟度。试验结果表明:堆肥中氮的损失量为26%～49%,堆体高温期持续时间长,导致氮的损失增加。添加石灰使堆肥前期的氮损失率增加,但加快了堆肥过程,总氮的损失没有加大。水溶性氨氮含量在堆肥升温期出现峰值5.61mg/gdw,堆肥结束时氨氮含量小于0.34mg/gdw;堆肥中硝态氮主要在降温期和腐熟期形成,达到1.84～4.05mg/gdw。氨氮和硝态氮之比小于0.16和水溶态有机碳与总氮之比小于1.10,较适合作为粪便与垃圾的混合堆肥腐熟指标。     

Modelling of organic matter dynamics during the composting process

Composting urban organic wastes enables the recycling of their organic fraction in agriculture. The objective of this new composting model was to gain a clearer understanding of the dynamics of organic fractions during composting and to predict the final quality of composts. Organic matter was split into different compartments according to its degradability. The nature and size of these compartments were studied using a biochemical fractionation method. The evolution of each compartment and the microbial biomass were simulated, as was the total organic carbon loss corresponding to organic carbon mineralisation into CO₂. Twelve composting experiments from different feedstocks were used to calibrate and validate our model. We obtained a unique set of estimated parameters. Good agreement was achieved between the simulated and experimental results that described the evolution of different organic fractions, with the exception of some compost because of a poor simulation of the cellulosic and soluble pools. The degradation rate of the cellulosic fraction appeared to be highly variable and dependent on the origin of the feedstocks. The initial soluble fraction could contain some degradable and recalcitrant elements that are not easily accessible experimentally.     

Degradation of greenhouse twines derived from natural fibers and biodegradable polymer during composting

Commercial composting operations generally do not accept organic wastes with plastic twines from the greenhouse vegetable industry and the bulk of the waste materials ends up in landfills. The objectives of this paper are to identify environmentally compatible substitutes that could replace the current use of petrochemically derived plastic twines in greenhouse vegetable production, thus diverting them from landfills, and to assess the extent of their degradation via composting. Physical properties of the twines, including linear density, percent weight loss and tensile strength were monitored for the biodegradation tests. A pilot-scale composting trial was conducted in an in-vessel composting system. Results showed that the three biodegradable twine materials (cotton, jute and EcoPLA) could degrade readily in a composting environment within a reasonable time frame. Specifically, at the end of 105 days of composting, 85.3%, 84.8% and 81.1% of weight loss was observed for cotton, jute and EcoPLA, respectively. Furthermore, EcoPLA exhibited a slower decline in tensile strength with time, when compared to jute and cotton.     

Sustainability research and practices in enforced residential institutions: collaborations of ecologists and prisoners

Enforced institutional settings such as penitentiaries provide environments to raise awareness, carry out research, and implement and assess practices for sustainable living. Institutions where residence is enforced due to health, recreational, military, or legal reasons (e.g., assisted living centers, summer camps, army bases, prisons) house people who may lack scientific training but have time and need for intellectual stimulation that can be filled by supervised research. These institutions have stable populations, structured social organization, and measurable inputs and outputs of materials and energy to carry out sustainable practices in tasks that affect regional resources such as groundwater quality and landfill use. We report on three examples at a corrections center resulting from partnerships among visiting academic ecology researchers, sustainability practitioners, corrections administrators, and prisoners: (1) research on how to sustainably “farm” moss for the horticulture trade to reduce harvesting pressure on wild moss populations; (2) a vermiculture and thermophilic composting system to reduce the kitchen waste; and (3) a monthly seminar series at the prison. Over 26 months: (1) participants developed methods to optimize moss growth; (2) landfill-bound waste and particulate flow rate destined for wastewater treatment decreased by 50%, to less than 50% of permit limits; (3) resulting compost (ca. 5000 kg) fertilized institutional vegetable gardens; (4) water quality improved so that the prison could return funds allocated to upgrade the prison’s water quality. The lectures encouraged intellectual exchange among researchers, convicts, and guards. Researchers derived new perspectives and broader impacts for their work. This can be a model for other correctional facilities and other enforced residential institutions (ERIs). Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Composting toilets as a sustainable alternative to urban sanitation – A review

In today’s flush based urban sanitation systems, toilets are connected to both the centralized water and wastewater infrastructures. This approach is not a sustainable use of our water and energy resources. In addition, in the U.S., there is a shortfall in funding for maintenance and upgrade of the water and wastewater infrastructures. The goal of this paper was to review the current knowledge on composting toilets since this technology is decentralized, requires no water, creates a value product (fertilizer) and can possibly reduce the burden on the current infrastructure as a sustainable sanitation approach. We found a large variety of composting toilet designs and categorized the different types of toilets as being self contained or central; single or multi chamber; waterless or with water/foam flush, electric or non-electric, and no-mix or combined collection. Factors reported as affecting the composting process and their optimum values were identified as; aeration, moisture content (50–60%), temperature (40–65 °C), carbon to nitrogen ratio (25–35), pH (5.5–8.0), and porosity (35–50%). Mass and energy balance models have been created for the composting process. However there is a literature gap in the use of this knowledge in design and operation of composting toilets. To evaluate the stability and safety of compost for use as fertilizer, various methods are available and the temperature–time criterion approach is the most common one used. There are many barriers to the use of composting toilets in urban settings including public acceptance, regulations, and lack of knowledge and experience in composting toilet design and operation and program operation.     

Pathogen reduction in minimally managed composting of bovine manure

Spread of manure pathogens is of considerable concern due to use of manure for land application. In this study, the effects of four static pile treatment options for bovine manure on die-off of a generic Escherichia coli, E. coli O157:H7 surrogate, Salmonella Senftenberg, Salm. Typhimurium, and Listeria monocytogenes were evaluated. Bovine manure spiked with these bacteria were placed in cassettes at the top, middle, and bottom sections of four static pile treatments that reflect minimal changes in pile construction with and without straw. Temperatures were monitored continuously during the 28 day self-heating period. E. coli and salmonellae were reduced from 8 to 9 log₁₀ CFU g^?1 to undetectable levels (<1.77 log₁₀ MPN g^?1) at 25–30 cm depths within 7 days in all pile sections except for the manure-only pile in which 3–4 logs of reduction were obtained. No L. monocytogenes initially present at 6.62 log₁₀ CFU g^?1 were recovered from straw-amended piles after 14 days, in contrast with manure-only treatment in which this pathogen was recovered even at 28 days. Decline of target bacterial populations corresponded to exposure to temperatures above 45 °C for more than 3 days and amendments of manure with straw to increase thermophilic zones. Use of straw to increase aeration, self-heating capacity, and heat retention in manure piles provides producers a minimal management option for composting that enhances pathogen die-off and thereby reduces risk of environmental spread when manure is applied to land.