Composting and biodegradation of thermally processed feather keratin polymer

Proteins obtained from agricultural sources represent a unique feedstock from which to prepare thermally processable polymers. In this study, thermally processed feather keratin films were composted with three-month-old compost inoculum in self-heating laboratory composters for 30 days and temperature and carbon dioxide development monitored. About 24% of the available carbon in the feather keratin polymer (FKP) was metabolized in this time and this may not be high enough for some applications. Degradation of the feather keratin polymers was observed within 10 days with concurrent molecular weight reduction measured using FT-IR. Visual inspection of the polymers also showed destruction of the films. A change in crystallinity was observed in DSC analysis and some degradation processes could be inferred from this as well.     

红外光谱结合二维相关分析研究堆肥过程腐殖酸演化规律

堆肥材料中腐殖酸的组成和结构直接影响堆肥产品品质和腐熟度。为研究堆肥腐殖酸的组成和形成过程,进行了生活垃圾堆肥并提取了不同堆肥阶段样品中的胡敏酸和富里酸,采用红外光谱和二维相关分析,探讨了堆肥过程胡敏酸、富里酸的组成、结构及随时间演化规律。红外光谱结果显示,堆肥胡敏酸组成复杂,在2 917～2 924,2 844～2 852,2 549,1 662,1 566,1 454,1 398,1 351,990～1 063,839,711 cm-1均出现了吸收峰;相对于胡敏酸,堆肥富里酸结构简单,仅在1 725,1 637,990 cm-1出现了吸收峰。上述吸收峰的出现表明堆肥胡敏酸和富里酸均含有木质素来源的苯环和糖类结构,但胡敏酸还含有丰富的脂族和蛋白类结构,这些在富里酸中含量较低;堆肥过程糖类、脂类、蛋白类及木质素结构均发生了降解,但是在胡敏酸和富里酸中它们的降解优先顺序不同。二维相关光谱分析结果表明,胡敏酸中降解先后顺序为脂肪类—蛋白类—多糖类和木质素,而富里酸中为蛋白质—多糖和脂肪类,降解过程均生成了羧酸、酮类和酯类结构,其中羧酸类物质一部分在堆肥中形成了碳酸盐。研究结果表明,红外光谱结合二维相关分析不仅可以获得堆肥腐殖酸官能团组成,还可以揭示堆肥过程这些官能团降解顺序,确定堆肥腐殖酸合成机制和动力学过程。     

不同物料堆肥腐熟程度的紫外-可见光谱特性表征

水溶性有机物(DOM)紫外-可见吸收光谱特性是评价堆肥腐熟度重要方法之一,但由于紫外-可见吸收光谱指标众多,单指标评价具有较大局限性。因此,本研究开展了影响堆肥腐熟度的关键紫外-可见光谱特性指标识别,并采用化学剂量学方法评价了不同来源堆肥腐熟程度。与传统单一物料评价相比,优选的评价指标及评价方法更具普适性。不同物料堆肥过程中DOM紫外-可见光谱特性分析结果表明,SUVA₂₅₄和SUVA₂₈₀值呈明显的增加趋势,E₂₅₀/E₃₆₅和E₄/E₆值呈相反的趋势,而A_226～400,S_275～295,S_350～400值则在堆肥末期变化显著。相关分析表明不同紫外-可见光谱参数(E₂/E₄和E₂₃₅/E₂₀₃除外)彼此之间相关性显著;主成分分析显示,DOM紫外-可见光谱指标A_226～400, SUVA₂₅₄, S_350～400, SUVA₂₈₀, S_275～295可作为堆肥腐熟程度关键影响评价指标。在此基础上,采用筛选的特性指标对堆肥末期进行聚类分析,可将九种不同来源堆肥分为两大类,第一类为猪粪、鸡粪、污泥、秸秆、园林垃圾、果蔬及生活垃圾等腐熟程度较低的堆肥;第二类为杂草和厨余腐熟程度较高的堆肥。     

Electron Transfer Capacities of Dissolved Organic Matter Derived from Swine Manure Based on Eletrochemical Method

Dissolved organic matter (DOM) is the most active fraction of compost organic matter. The presence of the redox-active functional groups in DOM allows it to act an electron shuttle to promote the electron transfer between microorganisms and terminal electron acceptors. In this study, the electron transfer capacities (ETCs) of compost DOM samples at eight different composting stages were determined by electrochemical method. 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Diquat dibro-mide monohydrate (DQ) were used to measured electron donating capacity (EDC) and electron accepting capacity (EAC) at working voltage 0.61 V/–0.49 V, respectively. The evolution characteristics of the chemical structures and components were analyzed by combining the three-dimensional fluorescence spectra, Fourier transform infrared (FTIR) spectra and elemental analysis. The results showed that the EDC of DOM increased from 16.850 μmol e^? (g C)^?1 to 22.077 μmol e^? (g C)^?1, The EAC decreased from 1.866 μmol e^? (g C)^?1 to 1.779 μmol e^? (g C)^?1. The results of three-dimensional fluorescence spectroscopy showed that the relative contents of humic-like and protein-like components gradually increased and decreased, respectively, during the composting process. The humuc-like components were the main contributor for the ETC of DOM. FTIR spectra showed that there was no significant change in the hydroxyl and carboxyl group contents of DOM during composting, suggesting no contribution of these function groups to the ETC of DOM. The elemental analysis showed that the content of oxygen in the DOM increased during the composting process, while the sulfur-containing group might be dominated contributor for its ETC.     

Biodegradation of sequentially surface treated lignocellulose reinforced polylactic acid composites: Carbon dioxide evolution and morphology

Maple fibres were treated with a variety of sequential treatments, namely sodium hydroxide (NaOH), NaOH followed by acetylation, or NaOH followed by silanation. These fibres were incorporated into a polylactic acid (PLA) composite and the biodegradation effects were investigated. After 124 days, all composites had exceeded 90% biodegradation with most close to 100%. The PLA composite with the NaOH-treated fibres had the quickest onset of degradation (4.9 days) and highest peak rate of degradation (1.77% biodegradation/day) of all composites studied. Neat PLA had a similarly high peak rate of degradation at 1.85% biodegradation/day, but had a later onset of 11 days. Gel permeation chromatography (GPC) analysis showed the earlier onset of degradation of the composites was caused by increased hydrolysis during composite fabrication as well as composting. GPC showed the formation of up to three molecular weight bands in the PLA during composting which were hypothesised to be occurring by surface hydrolysis, bulk hydrolysis and hydrolysis at the fibre interface. Analysing the remaining composite revealed the NaOH treatment not only caused an increased rate of degradation in the PLA through increase fibre porosity, but also caused an increased rate of degradation in the fibre from the lack of surface waxes and hemicellulose. Similar, yet slower, behaviours were also seen in the NaOH followed by acetylation and NaOH followed by silane treated composites with all composites degrading more rapidly than the neat PLA and neat maple fibre samples.     

Biodegradation and hydrolysis rate of aliphatic aromatic polyester

The biodegradation and hydrolysis rates of an aliphatic aromatic copolyester were measured in manure, food, and yard compost environments and in phosphate buffer solution (pH = 8.0) and vermiculite at 58 °C. Mineralization, molecular weight reduction, and structural changes determined by DSC, FTIR, and ¹H NMR were used as indicators of the biodegradation and hydrolysis rates. Poly(butylene adipate-co-terephthalate), PBAT, film biodegraded at distinctive rates in manure, food, and yard compost environments having different microbial activities. The highest biodegradation rate was found in manure compost, which had the highest CO₂ emissions and lowest C/N ratio. The possible presence of extracellular enzymes in manure and food composts may facilitate the hydrolytic reaction since greater molecular weight reduction rates were observed in these composts. ¹H NMR and thermal analysis revealed that, while PBAT is a semi-crystalline copolyester with cocrystallization of BT and BA dimers, the soft aliphatic domain (BA) and the amorphous region are more susceptible to hydrolysis and biodegradation than the rigid aromatic domain (BT) and the crystalline region.     

Biodegradability of conventional and bio-based plastics and natural fiber composites during composting,anaerobic digestion and long-term soil incubation

Plastics are a major constituent of municipal solid waste that pose a growing disposal and environmental pollution problem due to their recalcitrant nature. To reduce their environmental impacts and allow them to be transformed during organic waste recycling processes, various materials have recently been introduced to improve the biodegradability of plastics. These include conventional plastics amended with additives that are meant to enhance their biodegradability, bio-based plastics and natural fiber composites. In this study, the rate and extent of mineralization of a wide range of commercially available plastic alternative materials were determined during composting, anaerobic digestion and soil incubation. The biodegradability was assessed by measuring the amount of carbon mineralized from these materials during incubation under conditions that simulate these three environments and by examination of the materials by scanning electron micrography (SEM). The results showed that during a 660 day soil incubation, substantial mineralization was observed for polyhydroxyalkanoate plastics, starch-based plastics and for materials made from compost. However, only a polyhydroxyalkanoate-based plastic biodegraded at a rate similar to the positive control (cellulose). No significant degradation was observed for polyethylene or polypropylene plastics or the same plastics amended with commercial additives meant to confer biodegradability. During anaerobic digestion for 50 days, 20–25% of the bio-based materials but less than 2% of the additive containing plastics were converted to biogas (CH₄ + CO₂). After 115 days of composting, 0.6% of an additive amended polypropylene, 50% of a plastarch material and 12% of a soy wax permeated paper pulp was converted to carbon dioxide. SEM analysis showed substantial disintegration of polyhydroxyalkanoate-based plastic, some surface changes for other bio-based plastics and coconut coir materials but no evidence of degradation of polypropylene or polypropylene containing additives. Although certain bio-based plastics and natural fibers biodegraded to an appreciable extent in the three environments, only a polyhydroxyalkanoate-based resin biodegraded to significant extents during the time scale of composting and anaerobic digestion processes used for solid waste management.     

Real-life application of a QCM-based e-nose: quantitative characterization of different plant-degradation processes

Continuous surveillance of composting processes would enable a feedback loop to be obtained for both analysis and process control. For this purpose, we designed e-noses based on a six-electrode quartz-crystal microbalance (QCM) array coated with affinity materials and molecularly imprinted polymers (MIP). They enable quantitative monitoring of volatile organic compounds (VOCs) emitted directly in a compost bin and are highly suitable tools for achieving on-line characterization of the degradation processes occurring. During grass and pine composting (duration 14 days and 40 days, respectively), we observed concentrations of up to 250 ppm of esters, 700 ppm of alcohols, 250 ppm of terpenes, and 90% relative humidity directly on-line with such a system and could validate the data off-line by GC-MS. The sensor also gave direct insight into the differences between the two composting batch types. Besides duration, during grass composting larger amounts of alcohols are emitted whereas relative amount of terpenes is twice as high for pine composting. Detailed correlation of the sensor and the GC-MS data allows approximate estimation of the sensitivity of the sensor materials towards analyte classes such as, e.g., aliphatic alcohols or terpenes. Figure Mass sensitive sensor arrays coated with different molecularly imprinted and affinity materials are a highly suitable tool for quantitatively monitoring solvent patterns during composting procedures on-line in a composter headspace. Dedicated to Professor Udo Brinker on the occasion of his 65th birthday.     

Biodegradation of γ-sterilised biomedical polyolefins under composting and fungal culture environments

Polyolefin-based commodities are widely used as biomedical devices and food packaging after γ-sterilisation. The aim of the present work was to study the effect of γ-sterilisation on the biodegradation of polyolefins. Films of isotactic polypropylene, high-density polyethylene and ethylene-propylene (EP) copolymers were sterilised under γ-radiation with doses of 10 and 25 kGy. Neat and sterilised samples were incubated in compost and fungal culture environments. The changes in functional groups, surface morphology and chain scission in polymer chains were characterized by FTIR spectroscopy, SEM and viscometric measurements, respectively. A gradual decrease in intrinsic viscosity [η] and increase in carbonyl and hydroxyl regions in FTIR spectra were found for the γ-sterilised samples as a function of increasing dose. Polypropylene was found to be more susceptible to both radio-oxidation and biodegradation. It was observed that in case of ethylene-propylene copolymers, extent of γ-sterilisation and/or biodegradation depends on the composition and distribution of comonomers. Important surface erosion was detected by SEM, for higher sterilisation doses, after composting.     

初始物料组成对堆肥理化、生物和光谱学性质的影响

在中国,厌氧发酵的渣滓——沼渣的主要处理方式是作为有机肥直接施用于土壤,此方式对土壤存在不利影响,本研究采用畜禽粪便与沼渣混和堆肥的方式处理沼渣,可避免传统沼渣处理方式的缺陷,改善土壤质量。初始原料组成对堆肥过程有显著影响。为揭示初始物料组成对堆肥理化、生物和光谱学性质的影响,进行了15组不同物料配比的沼渣、猪粪和鸡粪混合堆肥试验。对堆肥理化和生物指标进行了测定,并采用紫外-可见光谱（UV-Vis）、同步和三维荧光光谱（3D-EEM）结合区域体积积分（FRI）和平行因子分析（PARAFAC）识别特征光谱参数,表征堆肥光谱学特性,采用典型对应分析（CCA）分别建立堆肥理化生物学性质和光谱学性质与初始物料组成的关系。结果显示：堆肥理化、生物学性质和光谱学性质都与初始物料组成有较高相关性,前4个排序轴分别合并解释了83.9%和97.5%的样本总变异。影响堆肥理化、生物学性质和光谱学性质的环境因子排序分别为：猪粪量＞鸡粪量＞沼渣量和沼渣量＞猪粪量＞鸡粪量。富碳原料有利于堆肥腐熟,高比例富氮原料不会导致堆肥氨氮累积。在沼渣混合物料堆肥中,低比例的沼渣有利于腐殖质形成。对沼渣与畜禽粪便混合堆肥发酵效果的评价应综合考虑理化、生物学指标和光谱学参数。