From Waste to Resource: Valorization of Lignocellulosic Agri-Food Residues through Engineered Hydrochar and Biochar for Environmental and Clean Energy Applications-A Comprehensive Review

Agri-food residues or by-products have increased their contribution to the global tally of unsustainably generated waste. These residues, characterized by their inherent physicochemical properties and rich in lignocellulosic composition, are progressively being recognized as valuable products that align with the principles of zero waste and circular economy advocated for by different government entities. Consequently, they are utilized as raw materials in other industrial sectors, such as the notable case of environmental remediation. This review highlights the substantial potential of thermochemical valorized agri-food residues, transformed into biochar and hydrochar, as versatile adsorbents in wastewater treatment and as promising alternatives in various environmental and energy-related applications. These materials, with their enhanced properties achieved through tailored engineering techniques, offer competent solutions with cost-effective and satisfactory results in applications in various environmental contexts such as removing pollutants from wastewater or green energy generation. This sustainable approach not only addresses environmental concerns but also paves the way for a more eco-friendly and resource-efficient future, making it an exciting prospect for diverse applications.

The Relationship between "Zero Waste" and Food: Insights from Social Media Trends

Zero waste (ZW), the concept of reducing waste production, is now becoming a lifestyle trend. Social media is strengthening this by popularizing the movement and connecting related communities. ZW and food are closely related, since food waste is a significant sustainability issue; however, the exact relationship between ZW and food communication on social networks is not clear. This study analyzed user communication on the social networking site Twitter between July 2008 and April 2023 to determine how members communicated and shared topics related to ZW and food; an analysis of hashtag frequency was also conducted. During the study period, a total of 50,650 tweets with both #zerowaste and #food hashtags were recorded, written by 21,271 unique users from all over the world. Topic analysis identified the nine related topics: ZW lifestyle, leftover recipes, ZW events, food rescue, climate change, packaging, ZW stores, composting, and ZW restaurants; visual analysis indicated that these topics were closely connected, suggesting common membership of these communities. Overall, our results provide insight into the ZW and food communities on Twitter, which may be useful for marketers, influencers, and government agencies to create targeted content and facilitate wider adoption of a ZW lifestyle.

Improvement of Natural Polymeric Films Properties by Blend Formulation for Sustainable Active Food Packaging

Active packaging manufactured with biopolymers extracted from agri-food waste is one of the most innovative and eco-sustainable strategies for maintaining food quality. However, biopolymers often present poor performances, which hinders their competitiveness compared with plastics. This work focused on developing and optimizing a natural polymeric blend produced by solvent casting based on zein and chitosan to improve the pure biopolymers' properties. The best results were obtained by blending zein and chitosan in a 1:2 weight ratio. The films were characterized in terms of morphology, mechanical and oxygen barrier properties, thermal stability, transparency and wettability. The blend production allowed us to obtain lower brittleness and lower stiffness materials compared with pure polymer films, with oxygen permeability values two orders of magnitude lower than pure zein, better optical properties with respect to pure chitosan and good thermal stability. The wettability properties of the blend did not result in being altered with respect to the single polymer, which was found to have hydrophilic behavior, highlighting the strong influence of glycerol used as a plasticizer. The results suggested that the polymer blending strategy is a viable and cost-effective method for producing packaging materials as alternatives to plastics.

Green Economy and Waste Management as Determinants of Modeling Green Capital of Districts in Poland in 2010-2020

Waste management must comply with the principle of sustainable development. A green economy is one of the paths to sustainable development and response to environmental problems. Waste should be a raw material that can be reused, processed, or turned into energy. The aim of the article is to assess the relationship and present the concept of zero waste and green economy, and to show selected framework conditions for their development in the county. To study the formation of phenomena depending on the location of a given object in the socio-economic space, a synthetic measure, the similarity matrix, the Gini coefficient was used. The analysis took into account features describing the condition of the natural environment, links between the natural environment, economy and society, the quality of life of the population, economic policy, and instruments influencing the economy, society and the environment. Empirical data were obtained from the local database of the Central Statistical Office for the years 2010-2020. The obtained results indicate the existence of dependencies in the development of a green economy and waste management in the region. The synthetic measure of waste management is from 0.43 to 0.61 in 2010, from 0.39 to 0.55 in 2020; green economy from 0.42 to 0.55 in 2010 and from 0.43 to 0.56 in 2020. Waste management is based on multidimensional waste management, taking into account economic, ecological and social aspects. Economic activity is related to the degradation of the natural environment. The green economy should assume the elimination of waste and environmental threats and the preservation of their value. The green economy is becoming a factor inducing structural changes in the economy and social life, helping in the most effective, sustainable and efficient use of limited resources. In the literature on the subject, this type of research is carried out at the level of regions or voivodeships. The authors use their own sets of indicators or their own indicators aggregated according to the available data at the poviat level. The obtained results can be an important source of information for local government authorities about disproportions between units.

Characterization of Biodegradable Films Made from Taro Peel (Colocasia esculenta) Starch

Studies of renewable polymers have highlighted starch’s role to replace petroleum-based components to produce biodegradable films with plastic-like qualities. In this study, the novelty of taro peel starch (TPS) to produce such films using the casting technique is reported for the first time. A response surface method (RSM) approach was employed to optimize different concentrations of TPS (2.5−3.5%, w/w) and glycerol (25−35%, w/w) and investigate their effects on the physico-mechanical and water barrier properties of TPS films. TPS films showed a positive linear effect (p < 0.05) for thickness (0.058−0.088 mm), opacity (1.95−2.67), water vapor permeability (0.06−0.09 g∙m/m2∙kPa∙h), and cubic effect (p < 0.05) for moisture content (0.58−1.57%), which were linked to high starch concentrations when plasticized with glycerol. X-ray diffraction analysis of TPS films depicted “amorphous”-type crystalline structure peaks at 19.88°, while the thermogravimetric analysis of the film samples exhibited 75−80% of the weight loss of TPS film in the second phase between temperatures of 300 °C to 400 °C. All films exhibited homogenous, transparent surfaces with flexibility, and completely degraded in 5 days in simulated river water and composting soil environments, which confirmed TPS as a promising film polymer in food packaging.

Multifunctional cellulosic materials prepared by a reactive DES based zero-waste system

Energy consumption and post-treatment of chemical reagent residues are important issues that hinder the sustainable production of the natural building blocks of cellulose nanofibrils (CNFs). In this study, we realize a low-energy, zero-waste process for CNF production by designing a novel reactive deep eutectic solvent (DES), the residue of which can be directly used as a plant growth regulator. After pretreatment with the DES, cellulose fibers self-delaminate into thin layers referred to as pseudo-CNFs, as their strength, toughness and transmittance are comparable to those of CNFs. Pseudo-CNFs break into smaller particles during recycling and thus display unique mechanical upcycling. After facile fibrillation, the obtained CNFs can independently form freestanding sub-micrometer films that show a strong, full coloration, which is demonstrated for the first time. Our concept can enable a green process, and the developed cellulosic materials may find various applications as structural materials and optical coatings.

Factors Affecting Zero-Waste Behaviours of College Students

This study evaluated the recognition and attitude toward microplastic and zero waste among college students and investigated the factors influencing their zero-waste behaviours. The study was conducted from 20 August 2021 to 10 September 2021, including students at a university in G metropolitan city, Republic of Korea. A total of 196 data were analysed. Statements were developed to verify how the use of disposables and the recognition, attitude, and behaviours related to zero waste were affected during the COVID-19 pandemic. Family type and usage of disposables were the factors affecting zero-waste behaviour in Model 1. In Model 2, which included the subcategory of zero-waste recognition, the health effects of microplastics and environmental preservation were significant factors. In Model 3, which included the subcategory of zero-waste attitude, the health effects of microplastics (β = 0.149, p = 0.016), use of eco-friendly products (β = 0.342, p < 0.001), and environmental preservation (β = 0.317, p < 0.001) were significant factors. The use of plastic products increased dramatically during the COVID-19 pandemic. Research and education are needed to promote zero-waste behaviours with a focus on microplastics. Raising awareness of the health effects of microplastics can enhance the effectiveness of education.

Integrated AHP-TOPSIS under a Fuzzy Environment for the Selection of Waste-To-Energy Technologies in Ghana: A Performance Analysis and Socio-Enviro-Economic Feasibility Study

Energy recovery from waste presents a promising alternative for several countries, including Ghana, which has struggled with unsustainable waste treatment methods and an inadequate power supply for several decades. The current study adopts a comprehensive multi-criteria decision-making approach for the selection of an optimal waste-to-energy (WtE) technology for implementation in Ghana. Four WtE technologies are evaluated against twelve selection criteria. An integrated AHP-fuzzy TOPSIS method is applied to estimate the criteria’s weights and rank the WtE alternatives. From the AHP results, technical criteria obtained the highest priority weight, while social criteria emerged as the least important in the selection process. The overall ranking order of WtE technologies obtained by fuzzy TOPSIS is as follows: anaerobic digestion > gasification > pyrolysis > plasma gasification. The sensitivity analysis indicates highly consistent and sturdy results regarding the optimal selection. This study recommends adopting a hybrid system of anaerobic digestion and gasification technologies, as this offers a well-balanced system under all of the evaluation criteria compared to the standalone systems. The results of the current study may help the government of Ghana and other prospective investors select a suitable WtE technology, and could serve as an index system for future WtE research in Ghana.

Chemical, technological, and sensory evaluation of the suitability of coconut by-products in white rolls

BACKGROUND

Fortification of rolls, one of the most popular snacks for children and adults, with coconut by-products can be interesting in terms of both nutritional enrichment and reduction of food waste. Coconut by-products, such as residues from coconut milk (RCM) and coconut oil (RCO) extraction, are a valuable source of dietary fiber. In the study, coconut flours obtained from RCM and RCO were used (FCM and FCO, respectively) for supplementation of rolls; white wheat flour was replaced with FCM or FCO at levels of 6, 12, and 18 g per 100 g.

RESULTS

The effect of the addition of the coconut by-products on the nutritional value, sensory evaluation, physical properties, and texture of rolls was determined after 24 and 72 h of storage. The research showed a positive effect of FCM and FCO on the roll yield, crumb moisture, and baking loss. The sensory evaluation revealed that the 12% addition of coconut residues yielded products with high overall acceptability (8 points on a 9-point scale). Compared with the control, a 12% addition of FCO or FCM contributed to an increase in proteins of 7.9% and 3.9% respectively and an increase in dietary fiber of 76% and 57% respectively. Despite the increase in the fat and protein contents, the energy value of the coconut rolls was significantly lower (244.6 kcal and 245.3 kcal for FCO and FCM respectively) than in the control wheat rolls (266.0 kcal).

CONCLUSION

White rolls with coconut flours obtained after grinding residues from oil or coconut milk extraction significantly increased the nutritional value of the rolls. © 2021 Society of Chemical Industry.

By-Products Revalorization with Non-Thermal Treatments to Enhance Phytochemical Compounds of Fruit and Vegetables Derived Products: A Review

The aim of this review is to provide comprehensive information about non-thermal technologies applied in fruit and vegetables (F&V) by-products to enhance their phytochemicals and to obtain pectin. Moreover, the potential use of such compounds for food supplementation will also be of particular interest as a relevant and sustainable strategy to increase functional properties. The thermal instability of bioactive compounds, which induces a reduction of the content, has led to research and development during recent decades of non-thermal innovative technologies to preserve such nutraceuticals. Therefore, ultrasounds, light stresses, enzyme assisted treatment, fermentation, electro-technologies and high pressure, among others, have been developed and improved. Scientific evidence of F&V by-products application in food, pharmacologic and cosmetic products, and packaging materials were also found. Among food applications, it could be mentioned as enriched minimally processed fruits, beverages and purees fortification, healthier and "clean label" bakery and confectionary products, intelligent food packaging, and edible coatings. Future investigations should be focused on the optimization of 'green' non-thermal and sustainable-technologies on the F&V by-products' key compounds for the full-utilization of raw material in the food industry.

Properties of Biocomposites Produced with Thermoplastic Starch and Digestate: Physicochemical and Mechanical Characteristics

This paper presents the results of a study on the influence of the addition of digestate (DG) sludge from an agricultural biogas plant on the mechanical properties of the coating obtained from thermoplastic starch (TPS). The dried, fragmented digestate, some of which had previously undergone ultrasound treatment, is used in the study. Biocomposites are produced by the pouring method using Teflon moulds as matrices. The physicomechanical study included the determination of the basic parameters of the materials obtained. Strength parameters, the contact angle, thermogravimetric properties (TGA), colour and colour difference and moisture absorption are determined. Photographs of the surface of the samples are taken with a scanning electron microscope (SEM) as well. It is found that the addition of the digestate has an advantageous effect on improving the physical and mechanical parameters. In general, samples with digestate also have a higher strength compared to the pure TPS material. The highest tensile strength and Young's modulus are found in samples with the 14 wt% addition of ultrasound-treated digestate. On the basis of this study, it can be concluded that the addition of digestate is a promising approach for the production of TPS biocomposites with superior mechanical properties.

Towards the circular economy: Analysis of barriers to implementation of Turkey's zero waste management using the fuzzy DEMATEL method

Zero waste has an important position in the circular economy model in terms of manufacturing recyclable products instead of products to be consumed quickly, reducing the amount of waste, developing and implementing recycling/reuse technologies, and thus ensuring resource efficiency. A zero-waste strategy is one of the basic steps to achieve the goal of the circular economy. The number of studies conducted on Turkey's zero waste management strategies referring to the circular economy is quite limited. To fill this gap in the literature, this study aims to identify the potential barriers which have an important role in zero waste management practices in Turkey. Through a broad literature review and expert opinions, 12 key barriers for zero waste implementation in Turkey have been defined in view of circular economy principles. Then, fuzzy DEMATEL methodology is employed to examine which is the most influential barrier affecting zero waste management success and to identify the interdependence of these barriers. The results indicate that uncertainty of the goals and tactics relevant to the circular economy and lack of financial and economic aid are key causal barriers that affect Turkey's zero waste management.

Zero waste and Wastephilian ethics during COVID-19

Responsibility toward the planet becomes imperative during the pandemic. Among the pressing issues, this is the management of waste. Ethical considerations on waste pertain to the consistency of adopting viewpoints that confront waste and its reality. Zero waste prospects remain to be an ideal in the perceived sustainable futures. The ethics of wastephilia or wastephilian ethics can reimagine sustainability in terms of waste management. While acknowledging the spectral or circular character of waste, wastephilian ethics confronts this reality by living-with waste.

Waste-to-Carbon: Is the Torrefied Sewage Sludge with High Ash Content a Better Fuel or Fertilizer?

Sewage sludge (SS) recycling is an important part of the proposed ‘circular economy’ concept. SS can be valorized via torrefaction (also known as ‘low-temperature pyrolysis’ or ‘roasting’). SS can, therefore, be considered a low-quality fuel or a source of nutrients essential for plant growth. Biochar produced by torrefaction of SS is a form of carbonized fuel or fertilizer. In this research, for the first time, we tested the feasibility of torrefaction of SS with high ash content for either fuel or organic fertilizer production. The research was conducted in 18 variants (six torrefaction temperatures between 200~300 °C, and three process residence times of 20, 40, 60 min) in 5 repetitions. Fuel and fertilizer properties and multiple regression analysis of produced biochar were conducted. The higher heating value (HHV) of raw SS was 21.2 MJ·kg⁻¹. Produced biochar was characterized by HHV up to 12.85 MJ·kg⁻¹ and lower H/C and O/C molar ratio. Therefore, torrefaction of SS with high ash content should not be considered as a method for improving the fuel properties. Instead, the production of fertilizer appears to be favorable. The torrefaction increased C, N, Mg, Ca, K, Na concentration in relation to raw SS. No significant (p < 0.05) influence of the increase of temperature and residence time on the increase of biogenic elements in biochar was found, however the highest biogenic element content, were found in biochar produced for 60 min, under the temperature ranging from 200 to 240 °C. Obtained biochars met the Polish regulatory criteria for mineral-organic fertilizer. Therefore SS torrefaction may be considered a feasible waste recycling technology. The calculation of torrefaction energy and the mass balance shows energy demand <2.5 GJ∙Mg⁻¹ w.m., and the expected mass yield of the product, organic fertilizer, is ~178 kg∙Mg⁻¹ w.m of SS. Further investigation should consider the scaling-up of the SS torrefaction process, with the application of other types of SSs.

Valorization of byproducts from tropical fruits: Extraction methodologies, applications, environmental, and economic assessment: A review (Part 1: General overview of the byproducts, traditional biorefinery practices, and possible applications)

Tropical fruits represent one of the most important crops in the world. The continuously growing global market for the main tropical fruits is currently estimated at 84 million tons, of which approximately half is lost or wasted throughout the whole processing chain. Developing novel processes for the conversion of these byproducts into value-added products could provide a viable way to manage this waste problem, aiming at the same time to create a sustainable economic growth within a bio-economy perspective. Given the ever-increasing concern about sustainability, complete valorization through a bio-refinery approach, that is, zero waste concept, as well as the use of green techniques is therefore of utmost importance. This paper aims to report the status on the valorization of tropical fruit byproducts within a bio-refinery frame, via the application of traditional methodologies, and with specific attention to the extraction of phenolics and carotenoids as bioactive compounds. The different types of byproducts, and their content of bioactives is reviewed, with a special emphasis on the lesser-known tropical fruits. Moreover, the bioactivity of the different types of extracts and their possible application as a resource for different sectors (food, pharmaceutical, and environmental sciences) is discussed. Consequently, this review presents the concepts of tropical fruit biorefineries, and the potential applications of the isolated fractions.

New York City's Reuse Impact Calculator: Quantifying the zero waste impact of materials reuse

In 2015, the city of New York (NYC) introduced a plan to reduce the volume of collected solid waste by 90% by 2030 and envisioned the expansion of reuse opportunities as one of its main drivers. The assessment of the contributions from reuse initiatives to the advancement of waste prevention and waste reduction goals requires a quantitative understanding of the scope of reuse activities. The high population density in NYC and well-organised collection efforts by The City of New York Department of Sanitation (DSNY) (DSNY) have resulted in a structure that enables the informal sector to readily contribute and access the reuse market. Importantly, the scale of the operations in NYC enable the results found to be a model for other municipalities of similar size. This article presents the Reuse Impact Calculator, developed from the need to automate and quantify the environmental impact of product reuse by nonprofit enterprises in NYC. Specifically, we will explain the development process, show the novel characteristics of this calculator, describe the software in terms of data input, auto mapping functionality and calculations and present a case study to demonstrate the implementation of the Reuse Impact Calculator. This calculator is a dynamic and easily modifiable tool that converts diverse datasets to comparable conditions and allows the assessment of the impact of reuse organisations to waste prevention in NYC.

Electronic Waste Governance under "One Country, Two Systems": Hong Kong and Mainland China

China is one of the largest e-waste dumping sites in the world, and Hong Kong, a semi-autonomous territory in China, is also affected by illegal e-waste disposal and transfer. While the Chinese government implemented a waste import ban in January 2018, Hong Kong has not enforced Chinese policies under the “One Country, Two Systems” framework. Drawing on a policy network approach, this paper provides an explanatory framework for e-waste governance in Hong Kong and China, and identifies the major obstacles to shaping effective transboundary e-waste control and prevention. The paper argues that institutional arrangements play a dominant role in governing e-waste policy networks at the local level of governance in Hong Kong and China; however, a lack of accountability and capacity at the transboundary level can explain the different waste electrical and electronic equipment (WEEE) management strategies in these two places.

Moving from recycling to waste prevention: A review of barriers and enables

Current European waste policy does not mainly aim to treat waste streams but rather place in the foreground of interest the complete supply chain of a product. Waste prevention and re-use do have the highest priority and they take effect before the end-of-life phase of a product or a material is reached. Recycling only takes the third place whereas recovery and disposal represent the least favourable options. Recycling can help to decrease the consumption of primary resources but it does not tackle the causes but only the symptoms. In principle, recycling processes require energy and will generate side streams (i.e. waste). Furthermore, there are insuperable barriers and the practice is far from 100% recycling. The philosophy of waste prevention and re-use is completely different since they really tackle the causes. It is self-evident that a decrease of waste will also decrease the consumption of resources, energy and money to process the waste. However, even if European legislation is proceeding in the right direction, a clear decrease in waste generation did not occur up to now. Unfortunately, waste generation represents a positive factor of economic growth. Basically, waste generation is a huge business and numerous stakeholders are not interested to reduce waste. More sophisticated incentives are required to decouple economic growth from waste generation.

Development of demand forecasting tool for natural resources recouping from municipal solid waste

Sustainable waste management requires an integrated planning and design strategy for reliable forecasting of waste generation, collection, recycling, treatment and disposal for the successful development of future residential precincts. The success of the future development and management of waste relies to a high extent on the accuracy of the prediction and on a comprehensive understanding of the overall waste management systems. This study defies the traditional concepts of waste, in which waste was considered as the last phase of production and services, by putting forward the new concept of waste as an intermediate phase of production and services. The study aims to develop a demand forecasting tool called 'zero waste index' (ZWI) for measuring the natural resources recouped from municipal solid waste. The ZWI (ZWI demand forecasting tool) quantifies the amount of virgin materials recovered from solid waste and subsequently reduces extraction of natural resources. In addition, the tool estimates the potential amount of energy, water and emissions avoided or saved by the improved waste management system. The ZWI is tested in a case study of waste management systems in two developed cities: Adelaide (Australia) and Stockholm (Sweden). The ZWI of waste management systems in Adelaide and Stockholm is 0.33 and 0.17 respectively. The study also enumerates per capita energy savings of 2.9 GJ and 2.83 GJ, greenhouse gas emissions reductions of 0.39 tonnes (CO2e) and 0.33 tonnes (CO2e), as well as water savings of 2.8 kL and 0.92 kL in Adelaide and Stockholm respectively.