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Over the past few years, persistent organic pollutants (POPs) exhibiting high ecotoxicity have been widely detected in the environment. Persulfate-oxidation hybrid system is one of the most widely used novel advanced oxidation techniques and is based on the persulfate generation of SO

Over the years, the transformation of biomass into a plethora of renewable value-added products has been identified as a promising strategy to fulfil high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Techno-economic analysis (TEA) and life-cycle assessment (LCA) are essential to scale up this process while lowering the conversion cost. In this study, trade-offs are made between economic, environmental, and technical indicators produced from these methodologies to better evaluate the commercialization potential of biomass pyrolysis. This research emphasizes the necessity of combining LCA and TEA variables to assess the performance of the early-stage technology and associated constraints. The important findings based on the LCA analysis imply that most of the studies reported in literature focussed on the global warming potentials (GWP) under environmental category by considering greenhouse gases (GHGs) as evaluation parameter, neglecting many other important environmental indices. In addition, the upstream and downstream processes play an important role in understanding the life cycle impacts of a biomass based biorefinery. Under upstream conditions, the use of a specific type of feedstock may influence the LCA conclusions and technical priority. Under downstream conditions, the product utilization as fuels in different energy backgrounds is crucial to the overall impact potentials of the pyrolysis systems. In view of the TEA analysis, investigations towards maximizing the yield of valuable co-products would play an important role in the commercialization of pyrolysis process. However, comprehensive research to compare the conventional, advanced, and emerging approaches of biomass pyrolysis from the economic perspective is currently not available in the literature.

Soil acidification in managed ecosystems such as agricultural lands principally results from the increased releasing of protons (H

Food waste constitutes a remarkable portion of municipal solid waste. About one-third of the global food waste produced is lost with the food supply chain. Food waste in many countries is still dumped of in landfill or incinerated simultaneously with other municipal wastes. Food waste requires proper management and recycling techniques in order to minimise its environmental burden and risk to human life. Despite considerable research on food waste conversion still, there is a shortage of comprehensive reviews of the published literature. In this review, we provide a mini global perspective of food waste with special emphasis on New Zealand and their conversion into the useful material through hydrothermal carbonisation (HTC). Other thermal technologies such as incineration and pyrolysis are also briefly discussed. The review discusses why HTC is more suitable thermal technology than others, which are currently available. Recognising the importance of techno-economic feasibility of HTC, we present a cost analysis on the production of value-added products via HTC with examples taken from the literature to gather information in the feasibility assessment process. Finally, key challenges and future directions for a better productive way of handling food waste are being suggested.

Hazardous wastes disposed of in engineered landfills interact with rainwater, generate harmful leachate and may contaminate groundwater. To minimize this, a suitable multi-layered cover system (MLCS) is constructed over the buried waste. Field assessment of complex moisture dynamics in unsaturated MLCS and its long-term hydraulic efficiency has not been investigated in detail for extremely humid conditions (annual rainfall >1000 mm). Therefore, the overarching purpose of this study was to investigate the long-term hydraulic performance of a three-layered hydraulic barrier cover system under humid Indian conditions. The field cover setup was exposed to natural weather condition in the Northeast Indian state of Assam, for 800 days. The MLCS was instrumented to measure continuous variation of volumetric water content and matric suction as function of time and depth. The field measurements were used to determine the appropriate input hydraulic parameters and evapotranspiration model that can be used for numerical modeling. The results showed that simulation using drying van Genuchten soil-water characteristic curve parameters and Penman-Monteith evapotranspiration model matched the field observations. Events of the highest precipitation and extreme drought (cause for desiccation) did not lead to percolation in the drainage layer (60 cm) and barrier layer (100 cm). Numerical analyses performed for 87 years by considering the climate data of two different humid locations (Eastern and Western part) of India revealed that the progressive saturation of barrier layer occurred within 18 to 20 years. However, when geosynthetic clay liner was incorporated as additional barrier material, the saturation time increased by two-fold (42 to 44 years).

The combined action of biochar and C-S-H (calcium-silicate-hydrate) in the cement mortars as adsorbents was explored for treating heavy metals from water. The biochar admixture cement mortars were ground to fines for use as adsorbents with the rationale that combined action of Ca, Si, Al etc. based industrial waste with conventional adsorbent biochar could enhance the removal efficiency of contaminants and therefore the overarching aim was to study the removal capacity for three selected heavy metals (Pb

We investigated the competitive effects of different fractions of wastewater treatment plant effluent organic matter (EfOM) on adsorption of an organic micro pollutant (OMP), propranolol (PRO), in a fixed bed column packed with magnetic tyre char (MTC). The results showed that the presence of EfOM inhibited PRO adsorption in wastewater leading to decreased PRO adsorption capacity from 5.86 to 2.03 mg/g due to competitive effects and pore blockage by smaller EfOM fractions. Characterization of EfOM using size exclusion chromatography (LC-OCD) showed that the principal factor controlling EfOM adsorption was pore size distribution. Low molecular weight neutrals had the highest adsorption onto MTC while humic substances were the least interfering fraction. Effect of important parameters such as contact time, linear velocity and bed height/diameter ratio on MTC performance was studied in large-lab scale columns. Linear velocity and contact time were found to be effective in increasing adsorption capacity of PRO on MTC and delaying breakthrough time. Increase in linear velocity from 0.64 cm/min to 1.29 cm/min increased mass transfer and dispersion, resulting in considerable rise of adsorbed amount (5.86 mg/g to 22.58 mg/g) and increase in breakthrough time (15.8-62.7 h). Efficiency of non-equilibrium Hydrus model considering dispersion and mass transfer mechanism was demonstrated for real wastewater and scale up purposes. Ball milling for degradation of adsorbed PRO and regeneration of MTC resulted in 79% degradation of PRO was achieved after 5 h milling (550 rpm), while the addition of quartz sand increased the efficiency to 92%.

An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl−, NO3−, SO42−, and CO32−) provide a high anion exchange capacity (53–520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer–Emmett–Teller specific surface area of LDH (1.80–179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° 0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.

We evaluated wastewater remediation and CO2 utilization potential of Chlorella minutissima from flue gas in a raceway pond, while synthesizing lutein and lipid for potential healthcare and biofuel application. A mix of 20% kitchen waste, 10 g L−1 of poultry litter waste and 5% flue gas was maintained while cultivating the microalga. Complete removal of nitrate, nitrite and ammonium, 85% carbon and 91% phosphorus was observed. An average areal biomass productivity of 4.06 ± 0.12 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was observed within 9 days. Biomass productivity of 6.21 ± 0.16 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was achieved during winter. Furthermore, lipid content with appropriate fatty acid composition 1.04:1 (saturation:unsaturation) increased from 25% to 58%. Additionally, lutein productivity of 1.2 ± 0.08 mgL−1 day−1, while utilizing 80.74 ± 0.07 mg L−1 day−1 of CO2 from 5% flue gas was obtained.

Bringing two completely different properties into one nanostructure by using individual metals is a difficult goal to achieve. However, recently core-shell metallic nanostructures have introduced as a novel multifunctional nanomaterial with enhanced properties. Iron and silver based nanoparticles are among the most widely applicable nanomaterials in modern industries. Zero-valent iron nanostructures and silver nanoparticles are well known for their applications as catalyst and antimicrobial agent, respectively. In the present study, for the first time, we are reporting a successful fabrication of zero valent iron coated silver nanoparticles (ZVI@AgNPs) by using a green and one-pot synthesis approach. Aqueous leaf extract of Mediterranean cypress (Cupressus sempervirens) was used as a natural source of reducing and capping agent for reduction of both Ag+ and Fe3+ ions. Prepared nanostructures were characterised by a range of analytical techniques namely UV–vis spectroscopy, Transmission Electron Microscopy, X-Ray Diffraction, and Fourier Transform Infra-Red Spectroscopy. The prepared nanostructures were found to be an effective material for dye removal and were capable to remove 98.5% of the initial dye just after 4 h. Based on the results, zero valent iron coating enhanced the antimicrobial potential of AgNPs against Gram-positive bacteria (S. aureus), while showing no significant enhancement against Gram-negative bacteria (E. coli). ZVI@AgNPs, therefore, can be introduced as a novel nanostructure for application in aquatic filter materials to simultaneously reduce microbial and organic contaminants.

Rapid industrial development and human activities have caused a degradation of soil quality and fertility. There is increasing interest in rehabilitating low fertility soils to improve crop yield and sustainability. Biochar, a carbonaceous material intentionally produced from biomass, is widely used as an amendment to improve soil fertility by retaining nutrients and, potentially, enhancing nutrient bioavailability. But, biochar is not a simple carbon material with uniform properties, so appropriate biochar selection must consider soil type and target crop. In this respect, many recent studies have evaluated several modification methods to maximize the effectiveness of biochar such as optimizing the pyrolysis process, mixing with other soil amendments, composting with other additives, activating by physicochemical processes, and coating with other organic materials. However, the economic feasibility of biochar application cannot be neglected. Strategies for reducing biochar losses and its application costs, and increasing its use efficiency need to be developed. This review synthesized current understanding and introduces holistic and practical approaches for biochar application to low fertility soils, with consideration of economic aspects.

Seasonal variations in the concentrations and fate of 20 selected pharmaceuticals and personal care products (PPCPs) were investigated over one year in a wastewater treatment plant in New Zealand, which relies on a membrane bioreactor (MBR) and Bardenpho as parallel processes for its secondary treatment. Results showed that all of the monitored PPCPs were detected in the wastewater influent. Nonsteroidal anti-inflammatory drugs (NSAIDS) and caffeine were predominant in the influent, whereas in the effluent, β-blockers and benzotriazole were present at significant concentrations. Total PPCPs' concentration in the influent was found to be 130 μg/L. Average removal efficiency was found to be ≥ 99% for acetaminophen, caffeine, TCEP, naproxen, and ibuprofen, whereas

The degradation of metformin (MET) and guanylurea (GUA) fortified separately in freshly collected two top soils (0–10 cm) from New Zealand's pastoral region was studied under controlled laboratory conditions. Incubation studies were carried at 30 °C under aerobic conditions at 60% of maximum water holding capacity and at two (0.5 mg/kg and 5 mg/kg) nominal soil concentrations. Degradation profiles revealed a bi-phasic pattern of both the compounds with an initial rapid degradation followed by slow dissipation rate, resulting in poor fits by simple first order kinetics. However, the use of three non-linear mathematical models sufficiently described the measured data and well supported by an array of statistical indices to judge model's ability to fit the measured datasets. Further evaluation using box-whisker plots showed that double first-order in parallel (DFOP) and first-order two-compartment (FOTC) models best fitted the data points followed by the Bi-exponential (BEXP) model. Mechanistic assumptions from DFOP and FOTC suggest that degradation of MET and GUA proceeds at two different rates, possibly in two compartments. The calculated DT50 using both models were in the range of 2.7–15.5 days and 0.9–4 days, while 90% dissipation time (DT90) varied between 91 and 123 days and 44 and 137 days for MET and GUA, respectively. Degradation of both compounds were dependent on soil types and properties, incubation conditions and initial substrate concentration. Formation of GUA with decrease in MET concentration over time confirmed that GUA is a transformation product concomitantly formed from aerobic degradation of MET in soil.

The world has entered into the "fourth-generation" of refrigerants, and it is an undeniable fact that we will continue to encounter several issues in identifying a suitable refrigerant that suits the purpose and poses no harm to the environment. The ever-changing regulations on the use of refrigerants have often posed great challenges to the refrigeration industry and there is a pressing need to develop new refrigerants and develop better equipment to use them. Theoretically, an ideal refrigerant should possess characteristics such as low-global warming potential (GWP), non-toxic, non-flammable, and zero-ozone depletion potential (ODP). In addition, the refrigerants are also expected to have excellent thermodynamic and thermophysical properties. Many new synthetic refrigerants have been reported as alternative refrigerants and have very low atmospheric life as well as low GWP and zero-ODP. However, it is irrefutable that most of the studies that reported the so-called new refrigerants are actually not new. From the invention of R-12 (Dichlorodifluoromethane) in 1930s to the invention of R-1234yf in 2000s, these substances are available for decades even before being recognized as refrigerants. This review attempts to provide chronicles on different aspects of refrigerants such as their progress since their invention in the early 1800s, classification and properties. In addition, concepts such as issues associated with the long-term use of refrigerants, barriers for the inclusion of low-GWP refrigerants, various protocols and accords that have occurred since the inception of refrigerants are also critically discussed.

We investigated the potential application of anaerobically digested residues for generating bioenergy in the presence of alkali bifunctional material, sodium zirconate (Na

Conversion of hazardous waste materials to value-added products is of great interest from both agro-environmental and economic points of view. Bone char (BC) has been used for the removal of potentially toxic elements (PTEs) from contaminated water, however, its potential BC for the immobilization of PTEs in contaminated water and soil compared to bone (BBC)- and plant (PBC)-derived biochars has not been reviewed yet. This review presents an elaboration for the potentials of BC for the remediation of PTEs-contaminated water and soil in comparison with PBC and BBC. This work critically reviews the preparation and characterization of BC, BBC, and PBC and their PTEs removal efficiency from water and soils. The mechanisms of PTE removal by BC, BBC, and PBC are also discussed in relation to their physicochemical characteristics. The review demonstrates the key opportunities for using bone waste as feedstock for producing BC and BBC as promising low-cost and effective materials for the remediation of PTEs-contaminated water and soils and also elucidates the possible combinations of BC and BBC aiming to effectively immobilize PTEs in water and soils.

A parametric study employing Taguchi's design of experimental technique was conducted to produce a value added novel biochar mix from three different origin feedstock and evaluate the effect of process parameters on biochar quality. Three feedstocks sourced from different origins (macroalgae: Sargassum sp, agricultural waste: rice husk and lignocellulosic waste: pine wood) were mixed in a definite proportion and pyrolyzed following the L4 experimental layout. Results indicated that temperature and mixing ratio were the most influential contributing factor. A temperature of 500 °C and 70% algae mix was the optimum condition to get an enhanced biochar in terms of thermal stability, aromaticity, pH balance, ash content and yield. Among the 4 Taguchi combination char S3 stands out as the best condition that resulted in high aromaticity, 40% high ash content, highly alkaline pH (10.3), 1–2% higher nitrogen and sulfur content. Potential application of biochar in agronomy as a soil ameliorant and/or in contaminant remediation as an adsorbent is suggested.

A solid carbon-rich product hydrochar, was prepared using hydrothermal carbonisation of food waste at temperatures of 200, 250 and 300 °C. To acquire detailed insight into physicochemical and structural properties, hydrochar samples were characterised using a range of techniques. The carbon content and higher heating value of food waste increased considerably from 39 to 73% and 15 to 31 MJ/kg corresponding to the heating temperature. The blends of hydrochar and coal prepared in three different ratios (5%, 10% and 15%) exhibited different thermal behaviour. The overall results of co-combustion study showed that the activation energy of hydrochar samples decreased from 56.78 KJ/mol to 29.80 KJ/mol with increase in temperature. Hydrochar prepared at 300 °C with coal blending ratio of 10% exhibited the lowest activation energy of 19.45 KJ/mol. Additionally thermal gravimetric analysis of the samples showed that high temperature carbonization can increase the combustion properties of hydrochar.

Rice is second only to maize among the world's most important cereal crops, with a global harvested area of approximately 158 million hectares and an annual production of more than 700 million tonnes as paddy rice. At this scale, rice production generates vast amounts of waste in the form of straw, husk, and bran. Because of high cellulose, lignin, and silica contents, rice biowaste (RB) can be used to produce rice biochar (RBC) and rice compost (RC). Furthermore, RB can be used as sorbents, soil conditioners, bricks/concrete blocks, flat steel products, and biofuels, all of which make significant contributions to meeting United Nations Sustainable Development Goals (UNSDGs). Although previous reviews have explored individual applications of rice feedstocks, inadequate attention has been paid to multifunctional values and potential multi-utilities. Here, we offer a comprehensive review of RBC and RC with respect to: (1) preparation and characterization; (2) applications as soil conditioners and organic fertilizers and their effects on soil-carbon sequestration; (3) remediation of toxic element–contaminated soils and water; (4) removal of colors, dyes, endocrine-disrupting chemicals, personal-care products, and residual pesticides from water; and (5) applications in the construction industry. Specifically, we describe the opportunities for the sustainable use of RBC and RC in the management of contaminated soils and water as well as the construction industry. Overall, this review is expected to lengthen the list of possible multifunctional applications of RBC and RC.

Recycled aggregates obtained from construction and demolition waste is known to have lower strength performance than natural aggregate concrete. Several studies have been conducted during the past decade to reduce the adverse effects of recycled aggregates on the strength properties of recycled aggregate concrete. The present study is in continuation of the similar approach, contributing towards the improvement of the recycled aggregate concrete properties with waste derived silicon rich char as a cement replacement from 0.1 to 0.75% of total volume of concrete. Concrete was produced with 100% recycled coarse aggregates and wash-mix sand. It was observed that rice husk and enhanced poultry litter char; both improved the compressive and splitting tensile strength at 0.1% of total volume. Rice husk char at 0.1% produced highest compressive and splitting tensile strength with 17% and 3% increment respectively. On the other hand, enhanced poultry litter and rice husk at 0.75% replacement produced optimum flexural strength than the rest of char mixes. Char was also found to reduce water absorption up to 0.5% of total volume and reduced the permeable voids in recycled aggregate concrete by creating dense structure. Based on the findings, we conclude that waste derived char can potentially enhance the properties of recycled aggregate concrete with marginal amount of cement content replacement while simultaneously acting as carbon storage.

The removal of recalcitrant organic pollutants in groundwater is a challenge being faced around the world. Achieving effective long-term remediation of contaminated aquifers faces a variety of significant issues such as back diffusion, tailing, and rebound. In recent years, some researchers have proposed the use of controlled release materials (CRMs) as a new approach to counteracting such issues. The novelty of CRMs lies in that they release their active products slowly, over prolonged periods of time, in order to sustain in situ treatments and long-term effectiveness. Here we review the main constituents of CRMs, analyze their production, characterization, and applications, with a focus on reaction mechanisms, effectiveness, and secondary effects. This review shows that the reactive components of CRMs most commonly involve either: (i) chemical oxidants to treat contaminants such as TCE, PCE, BTEX, and 1,4-Dioxane; (ii) sources of dissolved oxygen to stimulate aerobic biodegradation of contaminants such as BTEX and 1,4-Dioxane; or, (iii) substrates that stimulate reductive dechlorination of contaminants such as TCE and 1,2-DCA. It was found that in some studies, CRMs provided sustained delivery of CRM treatment reagents over several years, and achieved complete contaminant removal. However, lower removal rates were apparent in other cases, which may be ascribed to insufficient dispersion in the subsurface. There are a relatively limited number of field-scale applications of CRMs in contaminated land remediation. Those conducted to date suggest that CRMs could prove to be an effective future remediation strategy. Lessons learned from field applications, suggestions for future research directions, and conclusions are put forward in this review.

Concrete production and construction and demolition waste generation are some of the main contributors of constant carbon dioxide emission into the atmosphere. The main aim of this review is to present the status of construction and demolition waste generation around the world and subsequently provide a critical review of the recent studies conducted to improve the properties of recycled aggregate concrete through different supplementary materials. Information from 40 countries within six continents have been collated, critically analysed with the central focus being on the current construction and demolition waste generation and different policies adopted by the relevant government bodies. The future goals and targets of each country are briefly discussed. The overall construction and demolition waste generation in 40 countries worldwide reached more than 3.0 billion tonnes annually until 2012 and this trend is increasing constantly. The developing countries including India and China need to develop comprehensive system to monitor and utilize their huge C&D waste and government level initiative is required for mass awareness. Recycled aggregates obtained through construction and demolition waste are of inferior quality and use of different pozzolanic materials are recommended by several researchers to enhance its properties. Furthermore, it was also suggested to use the recycled aggregates from 30 to 50% to achieve the strength equivalent to natural aggregate concrete with supplementary cementitious materials. More research is imperative in the area of unconventional supplementary materials in recycled aggregate concrete and full structural analysis on long term scale. The uncertainty of its quality and absence of proper standards hinder its way of common adoption in real-world applications. Therefore, further research is necessary to endorse this waste in the construction industry and develop proper standards for its use in low-risk structural applications.

The application of biochar (BC) as a filler in polymers can be viewed as a sustainable approach that incorporates pyrolysed waste based value-added material and simultaneously mitigate bio-waste in a smart way. The overarching aim of this work was to investigate the electrical, mechanical, thermal and rheological properties of biocomposite developed by utilizing date palm waste-derived BC for the reinforcing of polypropylene (PP) matrix. Date palm waste derived BC prepared at (700 and 900°C) were blended at different proportions with polypropylene and the resultant composites (BC/PP) were characterized using an array of techniques (scanning electron microscope, energy-dispersive X-ray spectroscopy and Fourier transform infra-red spectroscopy). Additionally the thermal, mechanical, electrical and rheological properties of the BC/PP composites were evaluated at different loading of BC content (from 0 to15% w/w). The mechanical properties of BC/PP composites showed an improvement in the tensile modulus while that of electrical characterization revealed an enhanced electrical conductivity with increased BC loading. Although the BC incorporation into the PP matrix has significantly reduced the total crystallinity of the resulted composites, however; a positive effect on the crystallization temperature (Tc) was observed. The rheological characterization of BC/PP composites revealed that the addition of BC had minimal effect on the storage modulus (G') compared to the neat (PP).

In this study, biochar, a carbonaceous solid material produced from three different waste sources (poultry litter, rice husk and pulp and paper mill sludge) was utilized to replace cement content up to 1% of total volume and the effect of individual biochar mixed with cement on the mechanical properties of concrete was investigated through different characterization techniques. A total of 168 samples were prepared for mechanical testing of biochar added concrete composites. The results showed that pulp and paper mill sludge biochar at 0.1% replacement of total volume resulted in compressive strength close to the control specimen than the rest of the biochar added composites. However, rice husk biochar at 0.1% slightly improved the splitting tensile strength with pulp and papermill sludge biochar produced comparable values. Biochar significantly improved the flexural strength of concrete in which poultry litter and rice husk biochar at 0.1% produced optimum results with 20% increment than control specimens. Based on the findings, we conclude that biochar has the potential to improve the concrete properties while replacing the cement in minor fractions in conventional concrete applications.

Magnetisation of carbonaceous adsorbents using iron oxides has been found to be one of the potential solutions for easy recovery of adsorbent after use. We evaluated the effects of Fe3O4 nanoparticle addition on the physico-chemical properties of biochar and its sorption properties. Five adsorbents with varying amount of Fe3O4 per mass of adsorbent (0%, 25%, 50%, 75% and 100%) were used to adsorb sulfamethoxazole (SMX), an emerging micropollutant. Five isotherm models were used to evaluate the sorption behaviour of SMX onto the adsorbents where Redlich-Peterson model was found to best describe the data. Based on this model, the approximate site energy distribution for each adsorbent was determined. Surface area and sorption capacity had strong negative linear relationship with the amount of Fe3O4 per mass of adsorbent while the pore volume and saturation magnetisation of the adsorbent increased with increasing percentage of Fe3O4. The results of the approximate site energy distribution analysis showed that the addition of Fe3O4 on biochar reduced the area under the frequency distribution curve of sorption site energies leading to the lowering of the sorption sites available for SMX. This could be attributed to the blockage of the hydrophobic surface of biochar reducing the hydrophobic interaction between SMX and biochar.

Biochar is a recycled material obtained through the thermal degradation of any organic biomass in the manufacture of bio-fuel inside a reactor in a process known as pyrolysis. It is an organic material that can endure in soil for thousands of years. Given its aromatic nature, biochar is highly recalcitrant, and has been considered to have great potential to sequester carbon and reduce greenhouse gas emissions. This material has been commonly used in environmental and agricultural applications, as it can store plant minerals in its pore spaces and provide a large water-holding capacity. However, little research has been done on the geomechanical properties of the resulting mixture of biochar and soil. Some studies have shown that biochar can increase the shear strength of clays and desaturate soil particles, and it may be possible that it can also increase the resistance to liquefaction in loose sand. Therefore, it would be very interesting to assess whether this material is able to present a more environmentally friendly alternative for improving the properties of soil. In this study, samples of pure sand are dry-mixed with 0%, 3%, and 5% biochar by weight and tested under cyclic undrained shearing using a simple shear test apparatus. The preliminary results indicate that biochar can increase the cyclic resistance of sand.

A constant shift of society's dependence from petroleum-based energy resources towards renewable biomass-based has been the key to tackle the greenhouse gas emissions. Effective use of biomass feedstock, particularly lignocellulosic, has gained worldwide attention lately. Lignocellulosic biomass as a potent bioresource, however, cannot be a sustainable alternative if the production cost is too high and/ or the availability is limited. Recycling the lignocellulosic biomass from various sources into value added products such as bio-oil, biochar or other biobased chemicals in a bio-refinery model is a sensible idea. Combination of integrated conversion techniques along with process integration is suggested as a sustainable approach. Introducing 'series concept' accompanying intermittent dark/photo fermentation with co-cultivation of microalgae is conceptualised. While the cost of downstream processing for a single type of feedstock would be high, combining different feedstocks and integrating them in a bio-refinery model would lessen the production cost and reduce CO2 emission.

Biochar based wood/polypropylene (PP) composites were manufactured with two flame retardants (FRs): ammonium polyphosphate/APP and magnesium hydroxide/Mg(OH)2. The amounts of wood and biochar were alternated for accommodating the FRs in each blend. Flammability and mechanical characterisation for both the batches containing different FRs were done. Having higher proportion of biochar and less wood is beneficial to reduce flammability. The thermally stable biochar contributes to formation of effective char to restrict O2 transfer into PP. The higher weight ratio of biochar than wood in the composites compromised the tensile and flexural strengths to some extent as the APP and Mg(OH)2 particles were trapped inside biochar pores consequently reducing the effectiveness of biochar pore infiltration by PP. In general, addition of biochar with a woody biomass (with FRs) to neat PP significantly impedes its flammability while enhancing certain mechanical properties, such as flexural strength and tensile/flexural moduli and preserving the tensile strength.

Plastic pollution has increased exponentially in land and marine environment since its first usage started in the 1950s. Most of the microplastic studies have been conducted in the Northern hemisphere and little about microplastics is known in the Southern hemisphere particularly for New Zealand and Antarctic regions. Through this article we attempt to provide the current status of microplastic prevalence in entire New Zealand whilst analyse the environmental issues associated with it and the necessary actions being taken to mitigate those. Studies conducted specifically for New Zealand indicated that small urban streams served as the major transport pathways for microplastic pollution and local-scale processing factors had more impact than the overall catchment-scale processes being undertaken. Additionally, among the various types of microplastics a large proportion of plastics from wear and washing textile fabric were increasing the pollution load. These microplastic debris were eventually contaminating the waterways impacting the marine environment and the entire food chain. In order to reduce the contamination, New Zealand government took a firm step by banning the use of microbeads in some consumer products that are designed to be washed down the drain. Furthermore, businesses in New Zealand have taken firm action by stopping single-use plastic shopping bags and finding alternative solutions replacing plastics in various sectors. However, to completely eradicate microplastic contamination in New Zealand it is important to understand the level of damage done and for that more research is warranted, particularly attention needs to be at estimating the amount of plastic collected across New Zealand, types of plastics and their potential risks to human and the ecosystem health.

Due to the realisation of the reinforcement potential of waste based biochar and wool in polymeric composites, in the recent past, their individual flammability, thermal and mechanical properties were determined. Composites were manufactured with biochar and with both biochar and wool in conjunction with the halogen free flame retardant, which was followed by their characterisation through cone calorimeter, limiting oxygen index (LOI), thermogravimetry, tension/flexural tests, and scanning electron microscopy (SEM). Biochar exhibited a high resistance to heat without being ignited and possessed very low heat release and smoke production rates. Wool, although, had relatively high peak heat release rate (PHRR), its advantageous charring ability enabled a gradual reduction in heat release until flameout. The hardness and modulus of biochar were 4.3 GPa and 26 GPa, respectively. The tensile strength and modulus of wool were 160 MPa and 4.8 GPa, respectively. Composites containing biochar and wool significantly reduced the PHRR, smoke production, and elevated the mass loss rate (compared to neat polypropylene/PP). Hybridisation with wool proved to be beneficial for enhancing the LOI. Certain mechanical properties, such as flexural strength and tensile/flexural moduli, were preserved and enhanced, respectively, due to biochar pore infiltration by PP as seen in SEM.

Magnetisation of carbonaceous adsorbent using iron oxide (Fe x O y ) has potential to decrease the recovery cost of spent adsorbent because it could be separated magnetically. However, formation of various phases of Fe x O y and iron hydroxide (Fe x (OH) y ) during synthesis particularly the non-magnetic phases are difficult to control and could significantly reduce the magnetic saturation of the adsorbent. Hence, formation of the most magnetic Fe x O y , Fe 3 O 4, on biochar via oxidative hydrolysis of FeCl 2 under alkaline media was performed to synthesise magnetic adsorbent using pine sawdust biochar (magnetic pine sawdust biochar: MPSB). The Fe 3 O 4 nanoparticles on the surface of biochar contributed to high saturation magnetisation of MPSB, 47.8 A m 2 /kg, enabling it to be separated from aqueous solution using a magnet. MPSB were examined physically and chemically using various techniques. Sorbent-stability, parametric, kinetics, isotherm, thermodynamic and sorbent-regeneration studies were performed to comprehend the potential of MPSB as adsorbent to remove an emerging contaminant, sulfamethoxazole (SMX) from aqueous solution. Results showed that MPSB was stable within solution pH 4–9. Adsorption of SMX onto MPSB was favourable at low pH, fast and best described by Redlich-Peterson model. Adsorption was exothermic with physisorption possibly due to hydrophobic interaction and spent adsorbent could be regenerated by organic solvents.

Currently, the global carbon footprint of cement industry is nearly 7 to 8% and this number is expected to grow in the near future given the continued global demand of cement usage in the construction and other sectors. Additionally, extraction of sand from the coastal and riverine environment is detrimental to ecosystem health and also gives rise to sand mafia in many developing countries. Biochar has the potential to sequester CO2 in cement mortars. The purpose of this study was to valorise a waste biomass (poultry litter) to carbon-rich biochar and utilise as filler material to replace the sand in the range of 10–40% of the total weight in cement. A total of four mix designs each with three replicates at 10%, 20%, and 40% replacement of sand and control (0% biochar addition) were investigated for their mechanical, durability and micro-computed tomography (CT) analysis. The results showed that the flexural strength of the composites at 20% biochar replacement of sand was improved by 26% when compared to control. Biochar addition lowered the thermal conductivity of the cement mortars and was optimised at 10% addition. The density of the mortars decreased ~20% with 40% biochar addition. Micro-CT analysis showed nearly a five-fold increase in the 2-dimensional porosity of the samples, from 2.5% (control) to 12% for samples which had 40% biochar; however, no marked changes were noticed for samples at 20% biochar addition. Taking mortar plastering as an example for 100 m2 area with standard 12 mm thickness revealed that CO2 emissions decreased 20% when sand was replaced with 40% biochar as compared to control specimen. It was concluded that biochar has the potential to replace the sand in the mortars for improving toughness, lowering thermal conductivity and density of the cement composites.

We demonstrate a challenge-based innovation of End of Life Tyres (ELTs) pyrolysis for magnetic pyrochar production and synthesis with evidence of its use as low cost, novel adsorbent for pharmaceuticals removal from aqueous solutions. Magnetic tyre pyrochar (MTC) derived from ELTs at Technology Readiness Level 3-7 (TRL3-7), was tested for the removal of ciprofloxacin (CIP), propranolol (PRO) and clomipramine (CLO), from water, at varied pH and ionic strengths. The morphological and chemical properties of the adsorbents were assessed using Brunauer Emmett Teller (BET) surface area, Vibrating Sample Magnetometer (VSM), Fourier Transform Infrared (FTIR), Scanning Electron Microscope coupled with Energy Dispersive X-ray (SEM-EDS), elemental analysis and zeta potential measurements. MTC showed excellent adsorption efficiency of 85%, 90% and 92% for CIP, PRO and CLO respectively, higher than that of the non-magnetic tyre pyrochar (TC), due to the larger surface area, and porosity and lower polarity. Adsorption of the compounds onto MTC was highly pH dependent, and favourable at low ionic strength. The experimental data were well described by pseudo-second order kinetic and Freundlich isotherm models. Based on FTIR and zeta potential analysis, the interaction mechanisms were explained by cation-π, π-π EDA, cation exchange, electrostatic repulsion and hydrophobic effect. In the context of the circular economy, this ELTs based low cost magnetic adsorbent (estimated at $299/t) can be potentially used at full-scale industrial wastewater treatment for elimination of drugs from aqueous solutions, offering sustainable environmental remediation.

Waste based activated biochar was used to manufacture wood/polypropylene biocomposites. The biochar used had no surface functional groups, however, possessed high surface area (335 m2/g). Therefore, it was hypothesised that less than usual amount (3–5 wt%) of compatibiliser (maleic anhydride) could be used, to reduce production costs, while maintaining similar mechanical and flammability properties of the biocomposite. The biocomposites were characterised mechanically through tension, flexural, impact, and micro–hardness tests. The flammability and thermal behaviours were determined using cone calorimetry and thermogravimetry, respectively. Infrared spectroscopy and X–ray diffraction were also employed to comprehend the chemical changes occurring in the biocomposites. It was found that the amount of compatibiliser could be reduced to 1 wt% (from 3 wt%) without compromising on the mechanical performance (especially, tensile strength/modulus, impact strength, and micro–hardness) and flammability properties of the biocomposites. Electron microscopy revealed that the lack of compatibiliser in the biocomposites was compensated by well–dispersed biochar particles whose pores were infiltrated by the polymer causing a mechanical interlocking. In general, addition of biochar improved the mechanical and fire performance of the biocomposites compared to the neat polymer. Reduction of compatibiliser to 1 wt% from 3 wt% in conjunction with biochar saves ∼18% of the biocomposite production costs.

Soil carbon (C) plays a central role in the global biogeochemical cycles of most major nutrients, but the degree to which the quality versus quantity of C controls microbial abundance and function across land uses is still somewhat uncertain. We measured soil organic matter (SOM) concentration and composition as well as nutrient ratios and other soil characteristics on two contrasting soil types across three land uses (forest, pasture, maize cropping), to determine their relationships to microbial abundance and specific measures of microbial activity (e.g. qCO2, the ratio of respiration rate to microbial biomass, and net laboratory N mineralization). Although there was significant variability in bulk SOM composition (by 13C NMR spectroscopy), we could detect differences between broad-leaved forest and pasture/maize systems on a landscape scale, primarily attributable to differences in aryl C content. Variability in O-alkyl C between sites correlated strongly with the soil C:N ratio, but variability in alkyl C (which was particularly evident in pasture sites) could not be adequately explained by measured environmental or soil characteristics. Soil C:P and N:P ratios followed similar patterns with forest > pasture > maize. Bulk soil C:N, hot-water extractable C:N and particulate C:N all followed similar patterns with forest > pasture ≈ maize cropping. Microbial biomass C:N followed a different pattern, however, with forest ≈ pasture > maize. Despite the differences in SOM composition and nutrient ratios, anaerobically mineralizable N and hot-water extractable C (as a measures of available C) best explained the variation in microbial biomass and function across sites. Anaerobically mineralizable N generally explained the most variation for microbial biomass and qCO2 and had the smallest soil or land use effect. Hot-water extractable C explained the most variance for net N mineralization. Addition of stoichiometric measures and other soil attributes (e.g. soil C:N, C:P, δ15N) in a multiple regression model explained more of the variation than a single factor plus the land use effect (though soil order still explained a small, but significant amount of variance for measures of microbial biomass). A measure of available C, however, was needed to explain the maximum amount of variance in microbial biomass and function across sites (i.e. total C plus nutrient status and other soil attributes could not explain as much of the variance). Our data suggest that nutrient content/stoichiometry does assist in defining the quality of SOM, but a measure of available C (similar to the “active” pool in C models) is also needed. Anaerobically mineralizable N and/or hot water–water extractable C appear to be adequate measures of available C that relate to “active” C, but C functional groups (from 13C NMR spectroscopy) were not particularly useful for this purpose.

The current study investigated the formation of organic acids and alcohols as major intermediate products of wet oxidation of municipal sludge. Municipal sludge was subjected to 60-min wet oxidation at temperatures ranging from 220 to 240°C, with 20bar oxygen partial pressure. Acetic acid was the main intermediate compound produced in this study, followed by propionic, n-butyric, iso-butyric and pentanoic acids and methanol. It was found that the process severity has a significant influence on the formation and degradation of these intermediate products.

Biochar produced from the pyrolysis of waste pine wood was employed to manufacture wood/polypropylene biocomposites. Mechanical properties of micron–sized biochar particles were investigated and compared with those of waste pine wood and neat polypropylene particles by nanoindentation technique. An attempt was made for nanoindentation–assisted prediction of comprehensive mechanical properties of the resulting biocomposites. Theoretical models (i.e. rule of mixtures, Halpin–Tsai–Nielsen, and Verbeek) were applied using the nanoindentation properties of individual constituent particles to calculate the bulk properties of biocomposites. Good agreement was observed between the predicted and experimental moduli values. The hardness prediction through rule of mixtures correlated well with the Vicker's hardness test values. The nanoindentation hardness values of individual components follow an order: biochar (0.43 GPa) > wood (0.3 GPa)> polypropylene (0.1 GPa), whereas the moduli values are 1.5, 5.6, and 4.9 GPa for polypropylene, wood, and biochar, respectively.

To identify a route for organic wastes utilisation, biochar made from various feedstocks (landfill pine saw dust, sewage sludge, and poultry litter) and at diverse pyrolysis conditions, were collected. These biochars were used to fabricate wood and polypropylene biocomposites with a loading level of 24 mass%. The composites were tested for their mechanical, chemical, thermal, morphological, and fire properties. The poultry litter biochar biocomposite, with highest ash content, was found to have high values of tensile/flexural strength, tensile/flexural modulus, and impact strength, compared to other composites. In general, addition of all the biochars enhanced the tensile/flexural moduli of the composites. The crystal structure of polypropylene in the composite was intact after the incorporation of all the biochars. The final chemical and crystal structure of the composite were an additive function of the individual components. The biochar particles along with wood acted as nucleating agents for the recrystallization of polypropylene in composite. Each component in the composites was found to decompose individually under thermal regime. The electron microscopy revealed the infiltration of polypropylene into the biochar pores and a general good dispersion in most composites. The poultry litter composite was found to have lower heat release rate under combustion regime.

To impart usability in waste based biomass through thermo-chemical reactions, several physical and chemical pre-treatments were conducted to gain an insight on their mode of action, effect on the chemistry and the change in thermal degradation profiles. Two different waste biomasses (Douglas fir, a softwood and hybrid poplar, a hardwood) were subjected to four different pre-treatments, namely, hot water pre-treatment, torrefaction, acid (sulphuric acid) and salt (ammonium phosphate) doping. Post pre-treatments, the changes in the biomass structure, chemistry, and thermal makeup were studied through electron microscopy, atomic absorption/ultra violet spectroscopy, ion exchange chromatography, and thermogravimetry. The pre-treatments significantly reduced the amounts of inorganic ash, extractives, metals, and hemicellulose from both the biomass samples. Furthermore, hot water and torrefaction pre-treatment caused mechanical disruption in biomass fibres leading to smaller particle sizes. Torrefaction of Douglas fir wood yielded more solid product than hybrid poplar. Finally, the salt pre-treatment increased the activation energies of the biomass samples (especially Douglas fir) to a great extent. Thus, salt pre-treatment was found to bestow thermal stability in the biomass.

Douglas fir wood, a forestry waste, was attempted to be converted into value added products by pretreatments followed by pyrolysis. Four different types of pretreatments were employed, namely, hot water treatment, torrefaction, sulphuric acid and ammonium phosphate doping. Subsequently, pyrolysis was done at 500°C and the resulting bio-oils were analysed for their chemical composition using Karl Fischer titration, thermogravimetry, ion exchange, and gas chromatography. Pretreatment with acid resulted in the highest yield of bio-oil (~60%). The acid and salt pretreatments were responsible for drastic reduction in the lignin oligomers and enhancement of water content in the pyrolytic liquid. The quantity of xylose/mannose reduced as a result of pretreatments. Although, the content of fermentable sugars remained similar across all the pretreatments, the yield of levoglucosan increased. Pretreatment of the biomass with acid yielded the highest amount of levoglucosan in the bio-oil (13.21%). The acid and salt pretreatments also elevated the amount of acetic acid in the bio-oils. Addition of acid and salt to the biomass altered the interaction of cellulose-lignin in the pyrolysis regime. Application of pretreatments should be based on the intended end use of the liquid product having a desired chemical composition.