Waste Components Research Articles

Waste to Energy: Review on the Development of Land Fill Gas for Power Generation in Sub-Saharan Africa

This study focused on the development of land fill gas for power generation in Sub-Saharan Africa. In rapidly expanding cities in developing and emerging nations, it has been observed that municipal solid waste (MSW) has increased dramatically, raising public concern about the effects on the environment and public health. In Sub-Saharan Africa today, the garbage of people within this region especially in Nigeria is carelessly disposed. Environmental pollution and its effects on people's quality of life have become more sensitive topics among residents and decision-makers in Sub-Saharan Africa. Additionally, municipal solid waste management (MSWM) is becoming a more important topic on the local political agenda. Local decision-makers routinely debate whether to invest in waste-to-energy technologies as part of their effort to modernize waste management systems. Waste-to-Energy technologies are being promoted more and more as an alluring solution to a number of problems, including the urgent issue of waste disposal. These issues include inadequate power production, a shortage of landfill space, and greenhouse gas emissions from improper waste management. As an alternative to waste burning and composting, landfilling is one of the municipal solid waste (MSW) disposal techniques that are most frequently used. Due to its financial benefits, the sanitary landfill method is still often employed in various nations for the final disposal of solid waste. Landfill gas (LFG) is mostly produced by the anaerobic breakdown of the biodegradable component of municipal solid waste (MSW), specifically kitchen and yard trash, which is disposed of in landfills. Due to the anaerobic breakdown of the organic portion of solid waste, landfill gas is continuously produced. As a result, if an extraction system is not constructed in a landfill, there will be an overpressure that will force the biogas to be released into the atmosphere, which will have an adverse effect on the environment. Methane and carbon dioxide make up the majority of the gases that make up landfill gas, which is a mixture of other gases. Many landfill sites include an operational gas collection system that draws gas from both horizontal and vertical gas wells using a blower. The gas from the landfill was thought to only include carbon dioxide and methane. Methane's typical volume composition is 49%, hence it was believed that carbon dioxide would have a volume composition of 51%. Reviewing the information gathered by numerous studies regarding the volume of waste being dumped in landfills reveals that the waste produced in sub-Saharan Africa is sufficient to power the area with electricity. It was discovered that the quantity of electricity generated will fluctuate over time based on the flow rate of landfill gas. It will initially rise until a peak is attained. A million tons of landfill waste typically emits 434,000 cubic feet of LFG each day, which is sufficient to generate 0.80 MW of power. About 70% of LFG projects use internal combustion engines, gas turbines, and micro-turbines to produce power.

Full utilization of coal-fired power plant ash and slag waste components

Ash and slag waste are a major source of raw materials for various industries. In this work, we studied the possibility of the fractionation of coal-fired power plant ash and slag waste. The fractionation was carried out by the flotation to separate the aluminosilicate and carbon concentrate. The magnetic separation was used for isolation of iron oxide. The composition of the ash and slag as well as the fractions obtained was studied. Moreover, the morphology of the concentrate was investigated.

Improving Solid Waste Management Practices in Primary Schools in Ibadan, Nigeria

School system represents an important outlet for waste generation and advancement of knowledge on waste management. The aim of the study was to improve knowledge, attitude and practices of solid waste management (SWM) among pupils of selected primary schools in Ibadan, Nigeria. The study intended to find out what will be the effect of the intervention (training on solid waste management) on the knowledge, attitude and practice of the students towards solid waste recycling? A quasi-experimental study was conducted among pupils of two primary schools (public and private schools). Using validated questionnaire, information was collected to assess their knowledge, attitude and practices before and after intervention. Waste generated over a two-week period was characterised. A solid waste segregation stand was provided with all students trained on waste craftsmanship. Data were analysed at p=0.05. The post-intervention knowledge scores at increased from 5.3 ± 1.9 to 8.8+1.3 and 5.6 ± 2.4 to 9.1 ± 1.3 in public and private schools, respectively. The predominant waste materials in both schools were paper and nylon with mean weekly values of 5.3 ± 0.6 kg and 4.0 ± 0.4 kg in public school and 14.8 ± 0.2 kg and 8.6 ± 0.9 kg in private school. Plastic and organic waste had mean weekly values of 1.8 ± 0.0 kg and 0.5 ± 0.6 kg in public school and 2.9 ± 0.7 kg and 0.4 ± 0.3 kg in private school, respectively. Different crafts were made by the pupils from the components of waste generated. The intervention led to waste recycling and improved pupils' SWM knowledge, attitude and practices.

Integrating food waste management into urban wastewater treatment: Economic and environmental impacts

Food waste is the main component of municipal solid waste (MSW) and its sustainable management is a global challenge. Co-treatment of food waste and urban wastewater in wastewater treatment plants (WWTPs) could be a plausible management strategy to reduce the MSW amount that is disposed in landfills, while converting its organic fraction into biogas in the WWTP. However, the increased organic load in the wastewater influent would impact the capital and operating costs of the WWTP, mainly due to the increase in sludge production. In this work, different scenarios for co-treatment of food waste and wastewater were studied from both economic and environmental perspectives. These scenarios were designed based on different sludge disposal and management options. The results showed that the co-treatment of food waste and wastewater would be more environmentally friendly than their separate treatment, but its economic feasibility strongly depends on the ratio between the management costs of MSW and sewage sludge.

Viable Recycling of Polystyrene via Hydrothermal Liquefaction and Pyrolysis

Chemical recycling is considered one of the most sustainable solutions to limit the environmental issues related to plastic waste pollution, whereby plastic is converted into more valuable compounds when mechanical recycling is not feasible. Among the most critical fast-growing components of municipal solid waste, polystyrene represents 1/3 of the filling materials in landfills. In this work, the chemical recycling of polystyrene via two main thermochemical processes is investigated: pyrolysis and hydrothermal liquefaction (HTL). The influence of temperature (HTL: 300–360 °C and pyrolysis: 400–600 °C) and reaction time (HTL: 1–4 h; pyrolysis: 30 min) on the products obtained was studied. The obtained liquid and solid products were analyzed by using gas chromatography-mass spectrometry (GC-MS), an elemental analysis (EA), Fourier-transform infrared spectroscopy (FT-IR) and a thermogravimetric analysis (TGA). During HTL, a temperature of 360 °C and reaction time of 4 h were needed to completely decompose the polystyrene into mainly oil (83%) and water-soluble compounds (10%). The former was mainly composed of aromatics while the water phase was mainly composed of aromatics and oxygenated compounds (benzaldehyde and acetophenone). The pyrolysis led to the formation of 45% gas and 55% oil at 500 °C, and the oil was 40% styrene. Pyrolysis was thus more selective towards the recovery of the styrene monomer while the HTL can be an effective process to produce renewable aromatics.

Study on the influence of different side chain structures on the pyrolysis behavior of polyolefin plastic wastes

As an important component of organic solid wastes, disposal of plastic wastes (PWs) has always been a thorny issue. Thermochemical conversion is an efficient method. In-depth research on the influence of structural differences on their pyrolysis behavior is beneficial to promote the development of thermal treatment and conversion technology of PWs. The differences in the chemical structure of different polyolefin plastics at the molecule level are mainly reflected in their side chains. Herein, a series of typical polyolefin plastics with similar backbone structure and different side chain structures, including high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyvinyl alcohol (PVA) and ethylene-vinyl acetate copolymer (EVA), were selected for comprehensive pyrolysis characterization in this work. Advanced experimental analysis methods such as in-situ DRIFT and 2D-PCIS were adopted to investigate the evolution of two weak oxygen-containing side chains during pyrolysis of PVA and EVA, respectively. Besides, typical product distribution of six samples were systematically studied by combining SVUV-PIMS and GC/MS. Spectral analysis showed that OH side chain in macromolecular structure of PVA had the weakest thermal stability, and its oxidation reaction occurred earlier than dissociation and dehydration, while the acetoxy side chain in EVA polymers could not only be directly dissociated via deacetoxylation, but also be transformed into OH side chain via deacetylation that occurred simultaneously with deacetoxylation. Further combined with SVUV-PIMS and GC/MS, the distribution characteristics of pyrolysis products of polyolefin plastics and the rules of generation and release of typical products with temperature were obtained in detail. It was found that the release of typical oxygen-containing products was earlier or slightly earlier than the release of hydrocarbons in pyrolysis of PVA or EVA. However, the release of all hydrocarbons was almost simultaneous during the respective pyrolysis process of HDPE, PP and PS, suggesting that the evolution of oxygen-containing side chains with weak thermal stability occurred earlier under the drive of temperature. Based on the characterization results, the main evolution pathways of different side chains were proposed to explain the influence mechanism of different side chain structures on the pyrolysis behavior of polyolefin plastics. The cleavage of CC bonds mainly occurred in HDPE, PP and PS, while the evolution of side chains occurred first in PVC, PVA and EVA, and exerted different influence on the degradation of carbon skeleton.

Horse Manure and Lignocellulosic Biomass Characterization as Methane Production Substrates

This paper aimed to study the value of horse manure through anaerobic digestion. The study involved characterization of different components of horse waste and the evaluation of their biochemical composition, physicochemical characterization and the influence of the composition of horse waste on biochemical methane potential. More specifically, two bedding mixtures were studied: the first one was composed of wheat straw (WS), wood chips (WC) and horse manure (HM) with a volumetric composition of 85%, 14% and 1%, respectively; and the second one was a mixture of WS and HM with a volumetric composition of 99% and 1%, respectively. The analysis was carried out on the two bedding mixtures and on each substrate separately with 406 samples from May 2017 to October 2019. Biochemical methane potential tests conducted on these samples showed that the composition and structure of the substrate influenced the BMP. WS had the highest mono-digestion methane production with 176.1 NmL·gVS−1. The second bedding mixture (99% WS, 1% HM) showed a production of 189.4 NmL·gVS−1 compared to 127 NmL·gVS−1 by bedding mixture 1 (85% WS, 14% WC, 1% HM). The difference was due to a dilution effect on methane production caused by the presence of WC rich in lignin.

Simulation and experimentation on parameters influencing microwave-assisted extraction of bioactive compounds from Punica granatum waste and its preliminary analysis

Nowadays, the revalorization of high-value components of waste is the business goal for the development of food supplements in personalized nutrition, pharmaceuticals, and cosmetics. The objective of this study was to simulate and upgrade the extract quality of the medicinal plant Punica granatum L. peel powder by using microwave-assisted extraction (MAE). The central composite design was implemented for optimized parameters ethanol concentration of (50%), solvent: solid ratio (25:1 mL/g), extraction time (4 min), microwave power (450 W), on yield of 47.3%, total phenolic content of 432.05 mg GAE/g, DPPH reduction of 87.34%, was observed. The extract obtained after MAE of phenolic compounds contained 279.2 mg TAE/g DM of the highest total ellagitannin content and 25 mg QE/g DM of the flavonoid content of pomegranate peel powder. The structural characterization of bioactive compounds before and after MAE was performed using FTIR, SEM, and XRD. FT-IR technique was used to identify the functional groups in the pomegranate peel extract. The highest antioxidant active rich pomegranate peel extract proved that it can be utilized for the preparation of functional foods. This ‘green technology’ can be applied to various by-product processing and can be useful for upgrade studies for the value-addition of food products using an extraction approach. Practical applicationsThis study aims to establish a sustainable prototype for agro-industrial wastage management using an approach to process pomegranate peel that can deliver better economic and environmental outcomes. In this case, the application of the pomegranate peel extract is presented as an alternative to synthetic preservatives due to its highest antioxidant capacity. The advantage of the MAE procedure was the higher yield of up to 50% of extract per gram of peel powder. Our study demonstrates that statistically designed experiments allow for significant enhancement of the extraction process, which application could aid better use of natural resources and deliver more potent extracts than those obtained by currently recommended procedures.

Biomedical waste generation at Ayurveda hospitals in South Asia: A mini review of the composition, quantities and characteristics.

Ayurveda hospitals generate biomedical wastes (BMW). However, details on composition, quantities and characteristics are very scarce, details which are important to formulate a proper waste management plan for subsequent implementation and continual improvement. Therefore, this article presents a mini review of the composition, quantities and characteristics of BMW generated from Ayurveda hospitals. Additionally, this article presents some best possible treatment and disposal procedures. Most of the information was gleaned from peer-reviewed journals, although some information was collected by the author and from grey literature available to the author; 70-99% (by wet weight) of the solid waste is non-hazardous; biodegradables contributing to 44-60% by wet weight due to more used Kizhi (medicinal bags for fomentation) and other medicinal/pharmaceutical wastes (excluding waste medicated oils, which is 12-15% of the liquid medicinal waste stream and are not readily biodegradable) largely derived from plants. The hazardous waste component includes infectious wastes, sharps, blood as pathological wastes (from Raktamoksha - bloodletting), heavy metal containing pharmaceutical wastes, chemical wastes and heavy metal rich wastes. Quantities of infectious wastes followed by sharps and blood form a major portion of hazardous wastes. Most of the infectious waste material contaminated with blood or other body fluids and sharps from Raktamoksha are very similar (appearance, moisture content and bulk density) to what is generated from hospitals practicing Western medicine. However, hospital-specific waste studies are required in future to better understand the sources, areas of generation, types, quantities and characteristics of BMW, and hence to formulate more accurate waste management plans.

Experimental investigation on the impact properties and microstructure of recycled steel fiber and silica fume reinforced recycled aggregate concrete

With the continuous development of the economy and society, the production of solid waste is increasing. Construction and demolition waste (CDW), used tires and silica fume are the main components of solid waste. Recycling these materials will reduce resource pressure, decrease carbon emissions and protect the environment, while bringing certain economic benefits. This study focused on the influence of the synergistic effect of recycled steel fibers (RSF) and silica fume on the mechanical properties and impact resistance of recycled aggregate concrete (RAC). The mathematical statistical model of Weibull distribution was adopted to depict the impact results. In addition, the microstructure of the interfacial transition zone (ITZ) between the cement paste and the aggregate/fiber was researched by scanning electron microscopy (SEM). Results revealed that the synergistic effect of RSF and silica fume significantly improved the impact resistance of RAC. Especially the specimen containing 10% silica fume and 0.75% RSF performed the best properties, the first crack impact and failure impact energy increased by 421.9% and 461.3%, the net-gain in them by the synergistic action of silica fume and RSF with values of 102.7% and 115.3%. The distribution law of the impact life for RSF reinforced RAC can better describe by the two-parameter Weibull distribution function. Impact resistance life was predicted corresponding to reliability levels. SEM investigations revealed that the ITZ between cement and aggregate/RSF significantly improved by mixing silica fume.

Waste Valuation and Problems Encountered In Waste Bank Management: A Case Study at BSU ASRI BMP

Community participation-based waste management has been carried out by DKLH Jember Regency through the establishment of the Main Waste Bank its derivative organization, namely the Unit Waste Bank at a lower level. In this system, the effort being made is the integration of waste management, starting from the household as a producer, followed by sorting, then depositing it to BSU and ending with delivery to a temporary warehouse so that the waste is handled properly. This article aims to explore the potentials and problems encountered in the management of a Waste Bank which involves the participation of residents while still paying attention to aspects of economic feasibility. The research was carried out using the analitcal descriptive via interview and analysis of primary data owned by BSU ASRI BMP with due observance of scientific principles and maintaining the independence and interests of the authors. From the results of the research it is known that waste valuation efforts by providing economic value to each component of waste produced by each household are able to generate citizen interest in sorting and depositing the waste produced. The main contributors in the transfer of inorganic waste from BSU to BSI sequentially are paper, plastic and metal waste with the highest exchange rate ratio in metal waste. The main problem faced in the management of waste banks is the motivation of residents to independently handle daily waste. Besides that, there are also management constraints because the managers are housewives who must divide their time and attention for routine daily activities.

Generation and composition of solid waste in low-income areas of Jos, Plateau State, Nigeria

This study was carried out to determine the composition of solid wastes generated by some households in low-income areas of Jos Plateau State. Point source daily collection of household wastes from selected homes that were initially identified and categorized as low-income households were carried out for one week. The collected waste samples were weighed and sorted into food, ash/unburnt wood, plastic film/bags, fines, miscellaneous combustible, papers/cards, textiles, waste from electrical and electronic equipment (WEEE), glass, metals, dense plastic, garden waste and others. The components of these solid wastes were further classified into biodegradable (65.2%), recyclable (13.2%) and residual (21.6%). Biodegradable materials in the waste stream per household ranged from 1.7 kg to 18.3 kg per week. The recyclable materials produced by households varied from 0.4 kg to 2.9 kg and residual waste ranged from 0.6 kg to 6.0 kg per week. Urbanization and population growth are solely responsible for high increasing rate of solid wastes. The average household size found in the study area is 6.3 compared to an average household size of 4.6 Nigeria Demographic and Health Survey and 5.5 for Jos – Bukuru metropolis.

Sustainable hemp-based bioplastics with tunable properties via reversible thermal crosslinking of cellulose

Modern bioplastics and biocomposites frequently contain non-biodegradable or non-sustainable components and require complex recycling routes. Sustainable materials require integrating bio-based, cheap, widely available, recycled, or waste components. In order to incorporate these concepts, we selected hemp stalk waste, the industrial byproducts glycerol and xylan (hemicellulose), and citric acid as key components. Hemp stalks were processed into cast papers using only mechanical processes and no chemical modifications or pre-treatments. Cast papers were impregnated with a crosslinking mixture of glycerol, xylan, citric acid, and the plasticizer polyethylene glycol (PEG). Thermal crosslinking was performed as a single-step reaction by curing materials at 140 °C. All prepared bioplastics were washed in water for 48 h and extensively tested for water resistance and water absorption. A recycling route with depolymerization (for pulp recovery) in sodium hydroxide is demonstrated. A comprehensive analysis of crosslinking reaction is provided via FTIR and rheology, supplemented by structure analysis via SEM. A 7-fold reduction in water uptake was achieved compared to cast hemp paper. Obtained bioplastics, after washing in water, show elastic modulus up to 2.9 GPa, tensile strength up to 70 MPa, and elongation up to 4.3 %. As a result of component ratio variation, bioplastics achieve a high tuneability of properties ranging from brittle to ductile. Dielectric analysis indicates that bioplastics have the potential for application in electric insulation. A three-layer laminate is demonstrated as a concept for potential application as an adhesive for bio-based composites.

Chemical Recycling Processes of Waste Polyethylene Terephthalate Using Solid Catalysts.

Polyethylene terephthalate (PET) is a non-degradable single-use plastic and a major component of plastic waste in landfills. Chemical recycling is one of the most widely adopted methods to transform post-consumer PET into PET's building block chemicals. Non-catalytic depolymerization of PET is very slow and requires high temperatures and/or pressures. Recent advancements in the field of material science and catalysis have delivered several innovative strategies to promote PET depolymerization under mild reaction conditions. Particularly, heterogeneous catalysts assisted depolymerization of post-consumer PET to monomers and other value-added chemicals is the most industrially compatible method. This review includes current progresses on the heterogeneously catalyzed chemical recycling of PET. It describes four key pathways for PET depolymerization including, glycolysis, pyrolysis, alcoholysis, and reductive depolymerization. The catalyst function, active sites and structure-activity correlations are briefly outlined in each section. An outlook for future development is also presented.

Where are demolition wastes going: reflection and analysis of the February 6, 2023 earthquake disaster in Turkey

On 6 February 2023 at 09.17 BST, an earthquake measuring 7.8 on the Richter scale struck the southern border of Turkey near Syria, causing massive casualties and building damage. Badly damaged buildings need to be demolished, bringing a large amount of demolition waste, which, if not properly disposed of, can be a burden on the environment. In this study, damage to buildings in the quake-hit areas of Turkey is investigated, including reinforced structures and masonry structures. Based on this, the amount of demolition waste produced and the proportion of waste components are estimated roughly. Ultimately, the paper puts forward the strategy of recycling demolition waste after the earthquake and the application scenario planning of recycled products. Conclusively, the amount of demolition waste generated after the earthquake ranges from 450 to 920 million tons, providing new ideas for post-disaster reconstruction work. Besides, post-disaster waste management, safe demolition and environmentally friendly disposal and recycling technologies for demolition and construction wastes will bring good economic and environmental benefits, help the reconstruction of disaster areas, and provide a model for the resource utilization of construction and demolition waste worldwide.

Making Vermicompost from Kitchen Waste with Vermicomposting Technology

Rapid urbanization, industrialization, technological development, and population growth have created serious problems with rising solid waste generation, and managing such enormous amounts of waste is becoming increasingly difficult. Each year, more than one billion tonnes of solid trash are produced, and they end up unscientifically in the environment, creating costs for society, the economy, and the ecosystem. The proper management of this massive volume of garbage presents significant difficulties for humanity. Researchers from all over the world are looking for fresh, cutting-edge, and environmentally sustainable waste management technology. Biological approaches are more suited for waste treatment since they can be economical and recycle different waste components into useful end products. One such efficient biological waste management technique is vermicomposting, which uses bacteria to help earthworms break down garbage. Vermicomposting is a naturally occurring bio-oxidative decomposition process that takes place in mesophilic environments and is further facilitated by the biochemical activity of microorganisms.

The Effect of Cu2+ Exposure on the Nrf2 Signaling Pathway of Tilapia Hepatocyte, Base on Experiments In Vitro

Copper is a common component of industrial heavy metal waste and a major component of some fish medicines, which can cause oxidative stress and damage the health of farmed fish. The Nrf2 signaling pathway is an important pathway related to the oxidative stress on vertebrates. Exploring the effect of copper on the Nrf2 signaling pathway in fish hepatocytes would help improve the understanding of the molecular mechanism of antioxidants in fish hepatocytes and provide theoretical data for relevant toxicological research. Adult tilapia were cultured under properly controlled conditions for two weeks to adapt to laboratory culture conditions. Primary tilapia hepatocytes were obtained by cell culture. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay was used to detect the effect of copper ions on the viability of tilapia hepatocytes. The lipid peroxidation level (MDA) and antioxidant ability of tilapia hepatocytes (SOD and CAT activity) were detected. Quantitative PCR (qPCR) was used to detect the differential expression of each gene (Nrf2, Keap1a, Keap1b, CuZnSOD, MnSOD, HO-1, and GSTA) in the Nrf2 signaling pathway. The results suggested that after treatment with 100 μM copper ions for 4 h, 8 h, and 24 h, the viability of hepatocytes significantly decreased (p < 0.05). LDH and MDA after 8 h and 24 h treatment were significantly higher than those in the control group (p < 0.05). CAT activity significantly decreased after 4 h (p < 0.05), and SOD activity significantly decreased after 8 h and 24 h (p < 0.05). The results of qPCR showed that the expression of MnSOD significantly increased after a treatment with copper ions for 4 h, and the expression of Nrf2, Keap1a, CuZnSOD, HO-1 as well as GSTA significantly increased after a treatment with copper ions for 8 h, compared with the control group (p < 0.05). After being treated with copper ions for 24 h, the expression of Nrf2 and CuZnSOD significantly increased compared with the control group (p < 0.05). There was no significant difference in the expression of Keap1b or CAT at each time point. In conclusion, with copper ions exposure, the viability of tilapia hepatocytes was reduced, causing lipid peroxidation, a reduction in the antioxidant capacity of cells, the activation of the Nrf2 signaling pathway, and the increase in the expression of most genes in this pathway, which are defensive responses of hepatocytes to oxidative stress caused by copper ions. This study can provide theoretical data for related toxicological research.

EFFECT OF ETHANOL TREATMENT ON SHRINKAGE OF OIL PALM TRUNK FOR THE DRYING PROCESS

Oil palm trunk is one of the promising biomass materials due to the high volume of unused waste components and increasing worldwide demand to replace conventional wood. This study investigated the feasibility of using ethanol as a drying agent for oil palm trunks with different dimensional surfaces (radial, tangential and longitudinal sections). The radial shrinkage percentage for the outer layer is 1.50% (untreated) and 1.22 % (treated). In comparison, the inner layer of the untreated sample was recorded at 2.54 % shrinkage and the treated sample was at 2.29%. The tangential sample for the inner untreated sample shows 2.60% and the treated sample shows 2.40%. The same pattern of shrinkage was shown for the tangential section on the outer layer as 1.81% and 1.10% of the untreated and treated sample respectively. For the longitudinal surface, the inner layer section of the untreated sample was recorded at 0.39% compared to the treated sample at 0.25%. In comparison, a longitudinal surface section for the outer layer of the untreated sample was recorded at 0.38%, while the treated sample was recorded at 0.33% shrinkage percentage. The effect of ethanol treatment on the shrinkage is significantly different between different sections (P-value: 0.01) and between the outer and inner layers (P-value: 0.02). The result suggested that ethanol treatment could be an option for the oil palm trunk drying process. Dried oil palm trunks can be utilized as a potential substitution for biomass and wood to produce various products.

Polyhydroxyalkanoate synthesis from primitive components of organic solid waste: Comparison of dominant strains and improvement of metabolic pathways

The production of polyhydroxyalkanoate (PHA) from organic solid waste is a research hotspot. However, the allocation and conversion mechanism of different carbon resources between precursor routes and PHA metabolism remains unclear. We compared the PHA synthesis of dominant functional bacteria, Cupriavidus necator (C. necator) and Bacillus cereus (B. cereus), and replenished the metabolic pathways of primitive components (glucose, glycerin, lactic acid and propionic acid). The results showed that the PHA accumulation ability of C. necator (11.8%∼36.5%) was better than that of B. cereus (10.1%∼24.5%). C. necator had a faster rate of cell growth and PHA synthesis than B. cereus, which showed advantages in production efficiency. Most of the carbon of glucose flowed to the direct poly-3-hydroxybutyrate synthesis pathway. The carbon competition inhibited the PHA production from glycerin in C. necator, and cysteine metabolism was an effective pathway for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis in B. cereus. There were active amino acid pathway and aminobutyric acid pathway in the utilization of lactic acid in C. necator and B. cereus, respectively. The yield of copolymer was limited by acetyl-CoA in propionic acid system. This study laid the foundation for exploring the PHA synthesis from the components of organic solid waste.

Toxicity Characteristics Leaching Procedure of Wastes dumped in some part of Federal Capital Territory Abuja, North Central Nigeria

The solid wastes in some waste disposal facilities within Federal Capital Territory, Abuja Nigeria were assessed. They were assessed to know whether they are characteristically hazardous to the environment where they are dumped. The procedure became necessary because the solid wastes in the study are known not to be sorted before disposal. Sorting is needed to separate the hazardous components from non-hazardous components of the solid wastes before they are disposed. The assessment was done in accordance with Resource Conservation and Recovery Act, (RCRA, 1976) of United State Environmental Protection Agency using Toxicity Characteristics Leaching procedure. The procedure shows that the Chromium (Cr) ranges from 3.03mg/L to 11mg/L across the investigated dumpsites, Lead (Pb) ranges from 1.58mg/L to 47.6mg/L across the investigated dumpsites and Cadmium (Cd) ranges from 0.169mg/L to 19.2mg/L across the investigated dumpsites. It can be deduced from the results that the wastes in the investigated dump facilities are characteristically hazardous because the concentration of RCRA metals (Pb, Cr and Cd) are above the USEPA allowable limits.