Value-added Waste Research Articles

Value-added utilization technologies for seaweed processing waste in a circular economy: Developing a sustainable modern seaweed industry.

The global seaweed industry annually consumes approximately 600,000 tons of dried algal biomass to produce algal hydrocolloids, yet only 15-30% of this biomass is utilized, with the remaining 70-85% discarded or released as scum or wastewater during the hydrocolloid extraction process. This residual biomass is often treated as waste and not considered for further commercial use, which contradicts the principles of sustainable development. In reality, the residual algal biomass could be employed to extract additional biochemical components, such as pigments, proteins, and cellulose, and these ingredients have important application prospects in the food sector. According to the biorefinery concept, recycling various products alongside the principal product enhances overall biomass utilization. Transitioning from traditional single-product processes to multi-product biorefineries, however, raises operating costs, presenting a significant challenge. Alternatively, developing value-added utilization technologies that target seaweed waste without altering existing processes is gaining traction among industry practitioners. Current advancements include methods such as separation and extraction of residual biomass, anaerobic digestion, thermochemical conversion, enzymatic treatment, functionalized modification of algal scum, and efficient utilization through metabolic engineering. These technologies hold promise for converting seaweed waste into alternative proteins, dietary supplements, and bioplastics for food packaging. Combining multiple technologies may offer the most effective strategy for future seaweed waste treatment. Nonetheless, most research on value-added waste utilization remains at the laboratory scale, necessitating further investigation at pilot and commercial scales.

Applications of waste polyethylene terephthalate (PET) based nanostructured materials: A review

While polyethylene terephthalate (PET) has enjoyed widespread use, a large volume of plastic waste has also been produced as a result, which is detrimental to the environment. Traditional treatment of plastic waste, such as landfilling and incinerating waste, causes environmental pollution and poses risks to public health. Recycling PET waste into useful chemicals or upcycling the waste into high value-added materials can be remedies. This review first provides a brief introduction of the synthesis, structure, properties, and applications of virgin PET. Then the conversion process of waste PET into high value-added materials for different applications are introduced. The conversion mechanisms (including degradation, recycling and upcycling) are detailed. The advanced applications of these upgraded materials in energy storage devices (supercapacitors, lithium-ion batteries, and microbial fuel cells), and for water treatment (to remove dyes, heavy metals, and antibiotics), environmental remediation (for air filtration, CO2 adsorption, and oil removal) and catalysis (to produce H2, photoreduce CO2, and remove toxic chemicals) are discussed at length. In general, this review details the exploration of advanced technologies for the transformation of waste PET into nanostructured materials for various applications, and provides insights into the role of high value-added waste products in sustainability and economic development.

Thermal insulation material produced from recycled materials for building applications: cellulose and rice husk-based material

Construction materials derived from agro-industrial waste are increasingly attractive in the building sector, due to their sustainability and lower environmental impact. Hence, in recent years worldwide the amount of research and publications tending to the development of materials that take advantage of residues from agro-industrial activities has increased. The role of thermal insultation materials in the building envelope is significant, especially in hot-humid region. This study presents the manufacturing and evaluation of a cellulose and rice husk-based insulation material, as a proposal for the reuse of materials considered as value-added waste, such as recycled paper and rice husks. Boards and test specimens were elaborated, as well as mechanical and thermal tests. The material was evaluated by means of thermal tests, in accordance with ASTM C177, to measure the thermal conductivity. Tensile and compressive strength tests were performed, based on ASTM C209 and ASTM C39 Standard, respectively. According to the results obtained, the material shows a thermal coefficient of 0.04 W/m∙K which corresponds to a material with the potential to thermally insulate an enclosure. Maximum stresses were obtained for the 3 compositions in average for a range between 1.31 and 1.76 MPa. Ultimate compressive strength obtained was between 20.19 and 21.23 MPa. The proposed material is presented as a sustainable alternative, which can be used in the field of environmentally friendly buildings, which contribute to reducing the carbon footprint, by energy savings.

Evaluation of porosity, mechanical and thermal properties of self-ignition coal gangue-based foams via fast microwave foaming

Recently, the large-scale stock and pollution of solid waste has become a serious environmental and economic problem. Upcycling the solid waste to produce porous materials is a value-added waste management method. Self-ignition coal gangue-based alkali-activated foams were successfully produced via a fast microwave foaming method within a few minutes. The effect of alkali concentration on pore structure, porosity, mechanical and thermal properties of alkali-activated foams was explored. Alkali-activated foams with low bulk density (0.41–0.81 g/cm3), high total porosity (65.6–83.5 vol%), acceptable compressive strength (0.92–4.42 MPa), and low thermal conductivity (0.11–0.14 W/mK) were obtained by a fast microwave foaming method. The foams showed excellent high temperature performance. The compressive strength showed an increasing trend after heat treatment from 500 to 1100 °C. Simultaneously, a low high-temperature volume shrinkage (4.0–4.1%) was achieved. The obtained foams can be used as high-performance proppant materials, thermal insulation building materials, and in fire-resistant applications.

Current Challenges in the Sustainable Valorisation of Agri-Food Wastes: A Review

In the upcoming years, the world will face societal challenges arising, in particular, from the impact of climate change and the inefficient use of natural resources, in addition to an exponential growth of the world population, which according to the United Nations (UN) estimations will be 9.8 billion in 2050. This increasing trend requires optimized management of natural resources with the use of value-added waste and a significant reduction in food loss and food waste. Moreover, the recent pandemic situation, COVID-19, has contributed indisputably. Along with the agri-food supply chain, several amounts of waste or by-products are generated. In most cases, these biomass wastes cause serious environmental concerns and high costs to enterprises. The valorisation of the agri-food loss and food industry wastes emerged as a useful strategy to produce certain value-added compounds with several potential applications, namely in the food, health, pharmaceutical, cosmetic, and environmental fields. Therefore, in this review, some of the crucial sustainable challenges with impacts on the valorisation of agri-food loss/wastes and by-products are discussed and identified, in addition to several opportunities, trends and innovations. Potential applications and usages of the most important compounds found in food loss/waste will be highlighted, with a focus on the food industry, pharmaceutical industry, and the environment.

Dietary shredded steam-exploded pine particle supplementation as a strategy to mitigate chronic cyclic heat stress by modulating gut microbiota in broilers

Improving the availability of underutilized waste for the economic use of livestock feed can be important in countries where feed grain production is scarce. Modulating the gut microbiota through the fibrous content present in these wastes may help mitigate the adverse effects of heat stress (HS). Here, we investigated the effects of dietary steam-exploded pine particle (SPP), a value-added waste product, on the performance, gut health, and cecum microbiota in heat-stressed broilers. Ross 308 broilers (n = 180) at 29 days of age were distributed into three dietary treatment groups (0%, 1%, and 2% SPP) and two temperature conditions (NT: 21 °C; CHS: 31 °C) and grown for seven days. CHS, but not SPP, adversely affected performance parameters, but SPP did not interactively modulate these results. On the contrary, both differently affected other parameters. CHS resulted in increased rectal temperature, total protein in serum, and Nox4 gene expression, whereas 2% SPP increased GLP-2 and the Nox4 gene expression in the duodenum in comparison to 0% and 1% SPP. CHS significantly modified the beta-diversity of cecal microbiota while 1% SPP supplementation in diets increased the abundance of the favorable bacterial genera in chicken. Concludingly, CHS adversely affects growth performances, gut health, stress-related genes, and cecal microbiota while dietary 1% SPP may facilitate the proliferation of beneficial microorganisms in the cecum of broilers.

A full-scale black soldier fly larvae (Hermetia illucens) bioconversion system for domestic biodegradable wastes to resource.

Domestic biodegradable wastes (DBW) pose a threat to environmental quality and human health. Bioconversion via black soldier fly larvae (BSFL; Hermitia illucens L.) is an expedient way for converting 'waste to resource' (insect protein and biofertilizer). Although researches abounded in laboratory-reared experiments and bioconversion mechanisms were pertinent, the void of data from actual and full-scale operation restricts the intensification of BSFL technology and its global adoption. Hence, a full-scale BSFL bioconversion system lasting 4 years in Hangzhou (China) was investigated, and the feasibility and efficiency of 15 tonnes of DBW per day were studied. Through continuous technical optimization, the average production of fresh larvae was increased from 8.5% in 2017 to 15.3% in 2020, along with bioconversion rate of final vermicompost decreased from 35.4% to 14.5%. The total biomass reduction rate in 2020 was 68.7 ± 17.4 kg/(m3 d), equivalent to 0.735 ± 0.215 kg/(kg d) in the form of fresh larvae. Crude fat in fresh larvae accounted for 13.4%, and crude protein accounted for 16.2% in which the determined amino acid profile bore a strong resemblance to fish meal only except histidine and tyrosine. Its economic benefits proved the feasibility of this technology, and the profit reached up to 35.9 US$ per tonne of DBW in 2019. In conclusion, BSFL bioconversion system under current 'insect-farm' operation was a promising solution for DBW treatment with value-added waste recycling.

Emulsion-based drilling fluids: Rheological properties preservation facing changes on the temperature, pressure and dispersed phase

The biodiesel transesterification reaction generates crude glycerol as a by-product, which has been excessively generated due to the growing production of this biofuel. The possibility of allocating this low value-added waste to applications would solve several problems, especially regarding the need to dispose of this material. In this sense, the use of crude glycerol in olefin-based inverse emulsion fluids is something new in the literature. However, its performance in drilling fluids must ensure that the fluid's rheological properties are achieved. For this purpose, the plastic viscosity, yield stress and thixotropy of olefin-based fluids were studied, varying the temperature, pressure and the composition of the dispersed phase (sodium chloride brine (NaCl), crude glycerol and pure glycerol). A 23 factorial design was also carried out to assess whether the dispersed phase type, pressure and temperature variables affect the rheological properties of these fluids. The results showed that crude glycerol maintains the rheological properties of the conventional NaCl brine fluid even with changes in temperature and pressure, enabling the use of this industry waste for this type of application.

Physicochemical properties and storage stability of Turkish coffee fortified with apricot kernel powder

Apricot kernel (AK) is a by-product of dried apricot rich in oils, proteins, carbohydrates, and minerals. However, despite its rich content, it is generally discarded after apricot processing. This study aims to expand the usage areas of AK with rich content and offer new alternatives to coffee consumers. Various concentrations of powdered AK were added in Turkish coffee (mixture: AKTC) to improve product flavor and increase nutritional and functional properties. After cooking, some physicochemical analysis and storage stability of AKTC were evaluated. With the addition of AK, the phenolic content of TC increased approximately two times. Also, the addition of AK increased the antioxidant activity of TC by about 15%. Acrylamide content of TC was decreased from 131.36 ± 3.13 μg/kg to 82.55 ± 2.13 μg/kg by adding more AK. Panelists gave higher scores to AKTC compared to TC. According to the storage stability analyses, adding AK increased the storage stability of the pure Turkish coffee. Novelty impact statement The dried apricot by-product was first used for the fortifying of Turkish coffee, and the usage area of the apricot kernel, a high value-added waste, was expanded. The acrylamide level of the Turkish coffee was reduced by adding apricot kernel powder. The shelf life of Turkish coffee as extended by adding apricot kernel powder.

Upcycling of blending waste plastics as flexible growing substrate with superabsorbing property

Converting blending waste plastics into lightweight growing substrate is an attractive approach for efficiently recycling low value-added waste plastics. In the current research, a universal and mild strategy for recycling blending waste plastics to fabricate blending plastic-g-growing substrate (BP-GS) with superabsorbing and flexible properties was developed. The incompatibility between blending waste plastics was successfully overcome, and the effects of several parameters on the synthesis and water absorption of BP-GS were established. Furthermore, the prepared BP-GS possessed high water-absorbing capacity (1188%), excellent porous structure and flexible properties. Mechanisms study demonstrated that the blending plastics formed uniform structure via crosslinking of macromolecular free radicals, and additives such as superabsorbent polymer (SAP) and polyolefin elastomer (POE) were grafted into the blending waste plastics by forming stable covalent bonds, generating hydrophilic and flexible BP-GS. Furthermore, the regulation of melt flow rate (MFR) was ascribed to the effect of POE on crystallinity and branching degree of the plastics. In addition, pot and slope experiments showed BP-GS could coordinate with soil to support plants growth for drought and landslide prevention. Meanwhile, sequencing analysis indicated a micro-ecosystem could be formed in the prepared BP-GS to support plants growth. Therefore, the synthesized superabsorbent has potential application in vertical greening and slope restoration. This high value-added and universal recycling method will promote eco-friendly, upcycling and circular development of blending waste plastics recovery.

Value-added waste substitution using slag and rubber aggregates in the sustainable and eco-friendly compressed brick production

The current study aimed to analyse the viability of incorporating the post cryogenic discarded rubber and the air-cooled slag as an aggregate in partial replacement of stone dust in fly ash bricks production. A range of mechanical, non-destructive, and microstructural tests was performed on bricks thus produced by incorporating rubber and slag aggregates in various dosages (i.e., 5, 10, 15, 20 and 25% by stone dust weight). The result revealed that the compressive strength dropped from 71 to 43 % in the case of rubber aggregate replacement. Morphology study confirms that the rubber aggregates resulted in the porous microstructure of the bricks and leads to lesser unit weight and lighter structure. The rubber may be used as a lightweight aggregate in the brick possibly as it reduces the density of the final product. However, the use of rubber in bricks needs to be cautiously designed to get hold of productive solutions at the end. The findings demonstrate that the copper slag substitution of up to 15%, found to be enhanced the strength properties and it will be a better choice for low-cost construction as a promising alternative construction material.

Mechanical And Physical Properties Of Recycled Concrete Aggregates For Road Base Materials

The utilization of recycling recycled concrete aggregates (R-RCA) in road base construction is an option of value-added waste materials. The evaluation of R-RCA appropriateness as a road base material need to study. The use of massive amount of RCA in construction projects has acquired wide notoriety. The use of RCA is due to decrease- of amount natural rock as the original aggregate. The main objectives of this study are to characterize properties of R-RCA as road material, to determine mechanical and physical properties as a road base material, and to identify the R-RCA bearing capacity for road base comparison to natural aggregates. The mechanical and physical properties tests conducted according to standard, including particle size distribution Los Angeles Abrasion, Aggregate Crushing Value, Aggregate Impact Aggregate Density, Flakiness Index, Water Absorption, and California Bearing Ratio (CBR). The results show that the aggregates have an excellent distribution particle size, durability, and shapes as required by specifications R-RCA also produced appropriate CBR and strength for road base applications. These results stipulate exclusive information to utilize R-RCA as aggregates for road base construction. R-RCA can be used as road base construction materials, and its engineering properties transform from waste materials to value-added road base construction. Recycling of RCA not only can diminish the road base construction cost and decrease landfill space needed for disposal, but it engineering properties prone as road base construction, and considered a renewable resource.

Properties of 3D-printed wood sawdust-reinforced PLA composites

Thermal, morphological, and mechanical properties of three-dimensional (3D) printed polylactic acid (PLA) composites reinforced with different amounts of waste pine sawdust were investigated. To determine the mechanical properties of the obtained filaments, test samples were produced using a 3D printer according to the mechanical test standards. The filaments that were produced from blends that contained the wood sawdust at the highest level (20%) could be printed via a 3D printer without any problems. According to the results obtained from the mechanical tests, a decrease in the tensile strength values of the composites was observed with the addition of wood sawdust into the neat PLA polymer. On the other hand, it was determined that the flexural strength values of the wood sawdust/PLA composites significantly increased with the addition of the wood sawdust. It was concluded that the waste pine sawdust is a reasonable reinforcement material for the production of composite filament for 3D printing applications and it can be compatibly extruded with PLA polymer. Thus, sawdust can be used as a value-added waste source for the production of high-quality 3D polymeric materials.

Influence of inoculum variation and nutrient availability on polyhydroxybutyrate production from activated sludge

Carbon recovery through polyhydroxybutyrate (PHB) production can create a value-added waste management system. Activated sludge as inoculum enables PHB production using cheap and renewable carbons source, bringing PHB at par to conventional plastics. The PHB accumulating potential of activated sludge needs to be improved to realize the objective. The interaction between the origin of activated sludge, petroleum refinery sludge and brewery sludge, and nitrogen availability was explored to effect culture enrichment, improve PHB accumulation, and polymer characteristics through aerobic dynamic feeding. Consequently, nitrogen excess and limitation enrichment of both sludges produced mix microbial culture with adequate PHB storage of 7.8 ± 0.05%, 14.4 ± 0.04%, 14.4 ± 0.04%, 13.4 ± 0.02% respectively. Batch accumulation revealed higher PHB accumulation of 76.1 ± 0.03% and 71.7 ± 0.05% under nitrogen limitation for PRS and BS enriched under nitrogen excess condition compared to any other combination. The higher decomposition temperature of 285 °C, 293 °C, and a lower melting point of 168 °C, 165 °C with a higher molecular weight of 4.3x105g/mol and semi-crystalline arrangement indicates the potential applications for extracted PHB. PHB production enhanced under nitrogen limited conditions with culture enriched under nitrogen excess condition. However, similar PHB storage, physiochemical property, and overlapping microbial community show an insignificant effect of sludge origin on PHB production.

Value-added waste latex paints in masonry cement for plastering applications

Polymeric latexes are commonly used in cement-based plastering and rendering works. This paper assesses the effect of recycled polymers obtained from waste latex paints (WLPs) on flowability and mechanical properties of masonry cement (MC) mortars, including whether such performance would be similar to that induced by virgin polymers. Three MC classes prepared with different cement-to-limestone ratios are produced in compliance to relevant EN 413-1 and ASTM C91 specifications. The WLPs were not obtained from waste collection sites, rather produced to monitor constituents and properties prior to use. Test results showed that water retention and rheological properties of mortars containing virgin or recycled polymers are remarkably higher than unmodified mixtures. The mechanical properties of WLP-modified mortars including compression, flexure, and pull-off adhesion strength were pretty similar, or even higher than equivalent mixtures containing virgin polymers. This was attributed the presence of ultrafine pigment and extender particles that improve packing density and infer nucleation benefits for the growth of additional hydrates. The dry curing regime applied for virgin and recycled polymer-modified mortars is particularly advantageous in construction sites, as this reduces the hassle of moist curing normally required for unmodified plasters while securing higher resistance against sorptivity and shrinkage cracks.

Characterization of cannonball jellyfish (Stomolophus sp. 2) blue protein: a pH-stable pigment.

Pigments are present in a broad variety of terrestrial and aquatic organisms. The cannonball jellyfish (Stomolophus sp. 2) is an important fishery resource in the northwest of Mexico and is processed to be traded and consumed as seafood. During the process, water with a soluble blue pigment and other compounds are discarded to the environment. In this work, we present some properties of the blue pigment from Stomolophus sp.2 (S2bp), to decide if it could be considered as a potential value-added waste and avoid the blue proteinaceous pigment wastewater. S2bp was purified to homogeneity and had a molecular mass of 28.0kDa; this protein exhibited a ʎmax at 650nm, contained Zn2+ and Cu2+ metal ions, and was stable from 10 to 50°C and in a pH range of 3.0 to 13.0 for 1h. It had halotolerant characteristics maintaining the blue coloration in a broad range of ionic strength (0-4M NaCl) and showed changes in ʎmax with chaotropic salts. In addition, S2bp was stable in the presence of organic acids and EDTA and in zwitterionic, anionic, and nonionic detergents at critical micellar concentration. However, oxidant reagents like NaClO and H2O2 decrease the coloration. These results show that the jellyfish pigment is a stable protein which makes it an alternative pigment for the food industry.

New vacuum distillation technology for separating and recovering valuable metals from a high value-added waste

Flotation tailings of copper-anode slime is a high value-added waste. A new, clean and highly efficient vacuum distillation process is presented for the separation of valuable metals that remain in the waste. In this work, the saturated vapor pressure of each metal element in the flotation tailings is theoretically analyzed, with vapor-liquid equilibria (VLE) diagrams used to quantitatively predict the composition of the products. The optimum distillation temperature and time of volatilization behavior of each component are investigated using a two-step, low-temperature and high-temperature vacuum distillation experiment; the system pressure of both steps is 1–5 Pa. The experimental results indicate that the recovery efficiencies of Se and Te are 98.09% and 97.82%, respectively, after the low-temperature distillation (923 K and 120 min); the removal rates of Pb, Sb and Bi are 92.99%, 96.86% and 94.57%, respectively. The recovery efficiencies of Cu, Ag and Au are 95.65%, 99.28% and 99.12%, respectively, after the high-temperature distillation (1173 K and 50 min). Valuable metals in the flotation tailings can be separated and recovered effectively via a two-step vacuum distillation in which no wastewater or gas is released into the environment, meeting the development needs for cleaner production within the metallurgical industry.

Value-added Waste Potential of Wastewater Sludge from Pharmaceutical Industry: A Review

Wastewater treatment (WWT) plant treating pharmaceutical processing water produces sludge that may contain residue of the pharmaceutical products. This residue, known as Active Pharmaceutical Ingredient (API) is known to show ecotoxicity to the environment. The sludge potential to be utilised as value added products or to be used as raw material for other processes is explored in this review. Currently there is lack of studies on the content of pharmaceutical WWT (pWWT) sludge and its added value usage, partly due to vast varieties of pharmaceutical products, each utilising different process with different removal success in WWT and different effect on bacterial growth. Residue API from pharmaceutical manufacturing is known to be sorbed on the surface of the sludge. Cross comparison using limited sources of studies of bacterial composition in pWWT with municipal WWT (mWWT) shows that there are similarities between the bacterial compositions and thus sludge composition since sludge from biological WWT is constituted mainly of microorganism and Extracellular Polymer Substance (EPS). Studies on pWWT sludge composting shows usability of the sludge for agriculture purpose, but with concern over the sorbed API content causing ecotoxicity on the soil. Converting pWWT to energy using gasification and biodiesel production and construction material are the most promising value-added usage for the sludge.

Value-added waste cotton yarn: Optimization of recycling process and spinning of reclaimed fibers

In the spinning industry, waste yarns are generally forsaken or sale at low prices. The main purpose of this study is to give an added value to this waste and produce a new low cost yarn based on recycled yarn fibers. The first part of this study investigated the effect of the raw material and the recycling process taking into account the cut length (L) and the passage number (N) on the final quality of reclaimed fibers. The effect of different factors on the count of Neps (Neps), mean length (L), short fiber content (SFC), Upper Quartile Length (UQL), and weight yield (R) were examined by using design of experimental method. In the second part of this work, the highest quality fibers (Neps=260Cnt/g, SFC=26%, UQL=23.9mm,L=18mm and R=61.20%) were selected for this project. They were spun with a ratio cotton/recycling cotton 50/50 into a three account (Ne 10, Ne 15 and Ne 20). Comparing with the 100% cotton yarn, the blended yarn has similar physical and mechanical properties and it has a lower cost yarn since we can increase the total value of the yarn more than 33.5%.

Tire-derived carbon composite anodes for sodium-ion batteries

Hard-carbon materials are considered as one of the most promising anodes for the emerging sodium-ion batteries. Here, we report a low-cost, scalable waste tire-derived carbon as an anode for sodium-ion batteries (SIBs). Tire-derived carbons obtained by pyrolyzing acid-treated tire at 1100 °C, 1400 °C and 1600 °C show capacities of 179, 185 and 203 mAh g−1, respectively, after 100 cycles at a current density of 20 mA g−1 in sodium-ion batteries with good electrochemical stability. The portion of the low-voltage plateau region in the charge-discharge curves increases as the heat-treatment temperature increases. The low-voltage plateau is beneficial to enhance the energy density of the full cell. This study provides a new pathway for inexpensive, environmentally benign and value-added waste tire-derived products towards large-scale energy storage applications.