Mohammad Rehan

The current electricity demand of Kingdom of Saudi Arabia (KSA) is around 55 GW, which is projected to reach upto 120 GW by 2032. This energy is mainly produced from fossil fuels, posing a serious risk to human health and environment. Moving towards a sustainable model, KSA government has initiated a plan called King Abdullah City of Atomic and Renewable Energy (KACARE) to utilize the indigenous renewable energy resources to generate a further 54 GW energy from solar, wind, nuclear, geothermal and waste-to-energy (WTE). The arid nature of the KSA increases the importance of water in daily life and makes the country the third-largest per capita water user worldwide. There are about 12 thousand industries working in different sectors, which produce large quantities of wastes and waste sludge on daily basis. It has been estimated that 2.4 and 0.77 billion m3/ year of municipal and industrial wastewater respectively is produced in KSA, totalling to 3.17 billion m3/ year. Therefore, ther...

Envirocities eMagazine The energy demand and waste generation have increased significantly in the developing world in the last few decades with rapid urbanization and population growth. The adequate treatment of the waste or sustainable waste management is essential not only from a sanitation point of view but also due to its economic and environmental values including its potential contribution to energy generation in the developing countries. Many of the developed nations have adopted the approach and strategies of the integrated waste management system (Figure 1) to maximize the waste-based revenues in the form of energy, fuels, heat, recyclables, valueadded products, and chemicals along with more jobs and business opportunities. As a result, waste is no longer seen as refuse or discarded material, but an asset or resource to reduce not only the landfill volumes but also the dependency on fossil fuels by generating clean fuels. Dr. Abdul-Sattar Nizami Centre of Excellence in Envi...

Millions of Muslims from all over the world visit the Holy Cities of Saudi Arabia: Makkah and Madinah every year to perform Hajj and Umrah. The rapid growth in urbanization and the local population of Makkah city along with an ever increasing number of visitors result in huge municipal solid waste (MSW) generation every year. Most of this waste is currently dumped into landfill sites without any treatment, thus causing environmental and health issues. For example, on average around 2.4 thousand tons of waste is dumped into Makkah city’s landfill sites every day that increases to around 3.1 and 4.6 thousand tons per day during Ramadan and Hajj periods, respectively. Around 23% on average of this waste is a plastic waste in the form of plastic bottles, water cups, food plates and shopping bags (Abdul Aziz et al. 2007). A pilot scale catalytic pyrolysis process has been used to convert plastic waste into liquid fuel at Center of Excellence in Environmental Studies (CEES) of King Abdulaziz University, Jeddah. The produced liquid fuel has been found to have a high energy value of around 40 MJ/Kg, the viscosity of 0.9 mm2/s, the density of 0.92 g/cm3, the flash point of 30°C, pour point of -18°C and freezing point of -64°C, characteristics similar to conventional diesel. Thus the produced liquid fuel has the potential to be used in several energy-related applications such as electricity generation, transportation fuel, and heating purposes. It has been estimated that the plastic waste in Makkah city in 2016 could produce around 87.91 MW of electricity with net revenue of 297.52 million SAR. This is projected to increase up to around 172.80 MW of electricity and a total net revenue of 584.83 million SAR by 2040.

Today, the world is facing the challenges of the security of food, water and energy, economic growth and jobs and increased competitiveness and innovation. The nations have to change the traditional linear economy model having the pattern of taking, making, consuming and throwing away with a circular economy model that inherit the principles of sharing, leasing, reusing, repairing, refurbishing and recycling. Currently, the poor municipal solid waste management (MSW) in developing countries is resulting in several environments and public health issues such as the contamination of soil and groundwater, greenhouse gasses (GHG) emissions, disease spreading vectors, flies and rodents, fire outbreaks, odors and air and waterborne pollutants. Although, many developing countries have ambitious plans to improve MSW standards like developed nations, but due to limited allocated budgets to MSW, poor enforcement of the waste handling regulations, lacking necessary infrastructure and machinery ...

Biodiesel is a promising liquid fuel that is mainly derived from triglycerides and is utilized in diesel engines directly or after blending with conventional gasoline. Triglycerides comprise fatty acid methyl esters (FAME), which are generated from plant or animal based sources. Biodiesel generated from vegetable oils is expensive than petroleum-based diesel and has concerns with food vs. fuels debate. Therefore, biodiesel from renewable sources such as non-food feedstocks has attained a considerable interest in last two decades. This paper aims to examine the biodiesel generation from the non-food feedstocks available in the Kingdom of Saudi Arabia (KSA) as a source of renewable energy and valueadded products along with and a solution to current waste disposal problems. In KSA, non-food feedstocks such as animal fats, waste cooking oil (WCO), agricultural wastes, sewage sludge, and microalgae are promising sources for biodiesel production. These feedstocks are relatively cheap, eas...

Proper treatment and disposal of industrial pollutants of all kinds are a global issue that presents significant techno-economical challenges. The presence of pollutants such as heavy metal ions (HMIs) and organic dyes (ODs) in wastewater is considered a significant problem owing to their carcinogenic and toxic nature. Additionally, industrial gaseous pollutants (GPs) are considered to be harmful to human health and may cause various environmental issues such as global warming, acid rain, smog and air pollution, etc. Conductive polymer-based nanomaterials have gained significant interest in recent years, compared with ceramics and metal-based nanomaterials. The objective of this review is to provide detailed insights into different conductive polymers (CPs) and their nanocomposites that are used as adsorbents for environmental remediation applications. The dominant types of CPs that are being used as adsorbent materials include polyaniline (PANI), polypyrrole (Ppy), and polythiophen...

The world is facing severe environmental challenges, including increasing consumption of fossil-based energy and its consequent devastative impact, i.e. global warming and climate change. Biofuels are promising alternatives to fossil fuels with tremendous environmental and socio-economic benefits. There has been a considerable deal of research and development carried out on the production of biofuels in the last 2 decades. However, there is still a huge potential for achieving more cost-effective and efficient biofuel production processes through the application of nanotechnology. The exceptional properties of nanomaterials (nanocatalysts) such as high surface area, catalytic performance, crystallinity, durability, energy storage capacity, etc. offer great potential for optimizing biofuel production systems. Nanocatalysts could also serve recovery, reusability, and recycling purposes.

The organic Rankine cycle (ORC) has recently emerged as a practical approach for generating electricity from low-to-high-temperature waste industrial streams. Several ORC-based waste heat utilization plants are already operational; however, improving plant cost-effectiveness and competitiveness is challenging. The use of thermally efficient and cost-competitive working fluids (WFs) improves the overall efficiency and economics of ORC systems. This study evaluates ORC systems, facilitated by biogas combustion flue gases, using n-butanol, i-butanol, and methylcyclohexane, as WFs technically and economically, from a process system engineering perspective. Furthermore, the performance of the aforementioned WFs is compared with that of toluene, a well-known WF, and it is concluded that i-butanol and n-butanol are the most competitive alternatives in terms of work output, exergy efficiency, thermal efficiency, total annual cost, and annual profit. Moreover, the i-butanol and n-butanol-bas...

Black liquor (BL) rich phenolic and complex compounds is generated from pulp and paper mill manufacturing processes which should be treated before reaching the environment. The potential of achieving several sustainable development goals (SDGs) by recovering energy and valuable by-products from BL was extensively investigated. Results revealed that under a dark-fermentation process, the organic content in BL was effectively bio-degraded by anaerobes to achieve a hydrogen yield (HY) of 0.62 ± 0.04 mol/mol glucose. Fortunately, the HY was significantly increased up to 1.41 ± 0.13 mol/mol glucose by immobilizing the anaerobes onto magnetite nanoparticles (MN). α-amylase, xylanase, CM-cellulase, polygalacturinase, and protease enzymes activities were increased by 2.3, 23.7, 2.7, 26.8, and 31.1 folds with supplementation of MN. Moreover, the conversion efficiencies of protein and carbohydrate were improved by values of 36 and 113.3% and total phenolic compounds (TPC) were enhanced by 23....

This paper reviews the status of microbial electrolysis cells (MEC) as a mean for hydrogen (H2) production and urban wastewater treatment method. A case study of the Kingdom of Saudi Arabia (KSA) under MEC concept was developed. KSA is the world’s third largest per capita water user country with no lakes and rivers. Every year, around 1.17 and 0.38 billionm3 of domestic and industrial wastewater is generated respectively. The KSA government is seeking sustainable solutions for wastewater treatment and waste-to-energy (WTE) production to bridge the ever increasing water and energy demand-supply gap. However, there is no WTE facility exists to convert the wastewater into energy. Moreover, the potential of wastewater is not examined as an energy recovery substrate. This study, for the first time, estimated that a total electricity of 434 MWe can be produced in 2015 from the KSA’s wastewater if MEC technology is employed. Similarly, an estimated total electricity of 612 and 767 MWe can be produced for the years 2025 and 2035 from the domestic and industrial wastewater by using MEC technology. A surplus electricity of 508 and 637 MWe for the years 2025 and 2035 respectively can be added to the national grid after fulfilling the energy requirement of MEC wastewater treatment plants. Collectively, MEC will contribute 20.4% and 25.6% share of the KSA government’s WTE target of 3GW in 2025 and 2035 respectively. A number of challenges in MEC such as ohmic and concentration losses, saturation kinetics and competing reactions that lower the H2 production are discussed with their potential solutions including, the improvements in MEC design and the use of appropriate electrolytes, antibiotics and air or oxygen.

This study examines point and non-point sources of air pollution and particulate matter and their associated socioeconomic and health impacts in South Asian countries, primarily India, China, and Pakistan. The legislative frameworks, policy gaps, and targeted solutions are also scrutinized. The major cities in these countries have surpassed the permissible limits defined by WHO for sulfur dioxide, carbon monoxide, particulate matter, and nitrogen dioxide. As a result, they are facing widespread health problems, disabilities, and causalities at extreme events. Populations in these countries are comparatively more prone to air pollution effects because they spend more time in the open air, increasing their likelihood of exposure to air pollutants. The elevated level of air pollutants and their long-term exposure increases the susceptibility to several chronic/acute diseases, i.e., obstructive pulmonary diseases, acute respiratory distress, chronic bronchitis, and emphysema. More in-de...

Waste-to-energy (WTE) production is one of the sustainable solutions to fulfill energy demands and minimize the environmental problems associated with waste landfilling. This work investigates the biogas production and methane (CH4) enrichment for anaerobic digestion (AD) of fruit and vegetable waste (FVW). The effect of pH and temperature were studied using a lab scale batch anaerobic digester. The raw biogas was pebbled through water, NaOH, Ca(OH)2 and triethanolamine (TEA) for biogas purification and CH4 enrichment. The results showed that mixed fruit waste (MFW) provides 10 % more biogas yield than mixed fruit vegetable waste (MFVW). The maximum biogas yield of 0.030 (g/g volatile solids) was achieved at thermophilic temperature (TT). The optimum pH range under mesophilic temperature (MT) and TT condition was in between 8.3-8.8. The use of NaOH, Ca(OH)2 and TEA increased CH4 enrichment upto 5 %, 9 % and 7 %. Biogas having 71 % CH4 contents with 28 % reduced CO2 and 150 ppm H2S was produced using Ca(OH)2.

Zinc carbonate hydroxide Zn 5 (CO 3) 2 (OH) 6 nanoparticles have been successfully synthesised by the hydrothermal treatment of an aqueous solution of zinc acetate dihydrate (Zn(CH 3 COO) 2 •2H 2 O) and urea (NH 2 CONH 2) at 120 °C. The as-synthesized nanoparticles were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). XRD and SEM revealed Zn 5 (CO 3) 2 (OH) 6 nanoparticles produced in 20-40 nm size range with spherical morphology. TGA showed the expected one-step decomposition of zinc carbonate hydroxide to zinc oxide (ZnO) between temperatures of 180 °C and 350 °C. The hydrothermal reaction time (2, 3 and 4 hours) studied did not show any significant effect on the particle size and morphology. However, the crystallinity of the synthesised nanoparticles seems to be enhanced at longer hydrothermal reaction time by showing larger XRD diffraction peaks.

Millions of Muslims from all over the world visit the Holy Cities of Saudi
Arabia: Makkah and Madinah every year to worship in form of Pilgrimage
(Hajj) and Umrah. The rapid growth in local population, urbanization, and
living standards in Makkah city along with continually increasing number of
visitors result in huge municipal solid waste generation every year. Most of
this waste is disposed to landfills or dumpsites without material or energy
recovery, thus posing substantial environmental and health risks. The municipal
plastic waste is the second largest waste stream (up to 23% of total
municipal waste) that is comprised of plastic bottles, water cups, food
plates, and shopping bags. The sustainable disposal of plastic waste is
challenging task due to its clogging effects, very slow biodegradation
rates, and presence of toxic additives and dyes. Pyrolysis is one of the
promising waste-to-energy technology for converting municipal plastic
waste into energy (liquid fuel) and value-added products like char. The
produced liquid fuel has the potential to be used in several energy-related
applications such as electricity generation, transportation fuel, and heating
purposes. It has been estimated that the plastic waste in Makkah city in
2016 can produce around 87.91 MW of electricity. This is projected to
increase up to around 172.80 MW of electricity by 2040. A global warming
potential of 199.7 thousand Mt.CO2 eq. will be achieved with savings of 7.9
thousand tons emission of CH4, if pyrolysis technology is developed in
Makkah city. Furthermore, a total savings of 297.52 million SAR from landfill
diversion, electricity generation, and carbon credits would be possible to
achieve in 2016 from pyrolysis. These economic benefits will increase every
year and will reach up to 584.83 million SAR in 2040.

• First study on the incidence of FRs from different micro-environments of KSA • First study in literature reporting emerging Br/Cl FRs and OPFRs in AC filter dust • Chlorinated alkyl phosphate, BDE-209, and DBDPE were major chemicals. • Lower levels were observed in house dust than those of car and AC filter dust. • Estimated risk assessment of BDE-99 for toddlers was high than the RfD values. Different flame retardants (FRs) namely polybrominated diphenyl ethers (PBDEs), emerging brominated/chlori-nated flame retardants (Br/Cl FRs), and organophosphate FRs (OPFRs) were analyzed in cars, air conditioner (AC) filters and floor dust of different households from Jeddah, Kingdom of Saudi Arabia (KSA). To the best of our knowledge, this is first study in literature reporting emerging Br/Cl FRs and OPFRs in AC filter dust and also first to report on their occurrence in dust from KSA. Chlorinated alkyl phosphate, penta-BDEs, BDE-209, and decabromodiphenylethane (DBDPE) were the major chemicals in dust samples from all microenvironments. ΣOPFRs occurred at median concentrations (ng/g dust) of 15,400, 10,500, and 3750 in AC filter, car and house floor dust, respectively. For all analyzed chemicals, relatively lower levels were observed in floor dust than car and AC filter dust. The profiles of FRs in car dust were different from AC filter and floor dust, which reflected their wider application as FR and plasticizer in variety of household and commercial products. For toddlers,

A lot of attention has been paid to improving occupational safety and health (OSH) in small scale industries all over the globe. This study describes the outcomes of a preliminary OSH status assessment in small scale industries of motor vehicle repair workshops (MVRW) in Jeddah, Kingdom of Saudi Arabia (KSA). An inspection tool composed of 10 OSH elements and 62 items employed walk-through survey, observations and interviews. The mean positive responses for different OSH elements surveyed were as follows; personal protective equipment (PPEs) (43%), emergency preparedness (49%), fire protection (60%), facilities (80%), general workshop safety (43%), housekeeping (17%), chemical exposure (12%), services and maintenance (57%), mechanical handling (81%) and tool safety (63%). However, special concerns were found for OSH elements including; use of PPE's, emergency preparedness, general workshops safety, housekeeping and exposures to chemicals as having safety score less than 50%. OSH elements with lower positive responses at surveyed workshops would be addressed through further monitoring and training of technical and administrative staff. This preliminary survey will form the basis of a more comprehensive study for evaluation of an accurate representative OSH status in small scale industries in KSA.

Professional driving is associated with high rates of occupational musculoskeletal disorders (OMSDs). The objective of this study was to assess the prevalence of OMSDs among drivers and office workers of taxi industry in Jeddah city. A detailed custom-made questionnaire was used that included socio-demographic and occupational characteristics of subjects together with OMSDs prevalence rates. In this research, 173 subjects participated of which 70.5% were drivers and 29.5% were office workers. Standard Nordic Questionnaire (SNQ) was used to assess 1-year and 1-week prevalence rates of OMSDs in nine body regions. 1-year and 1-week reported prevalence rates of OMSDs among taxi drivers were 85.3 and 51.6%, while among office workers were 52.9 and 31.4%, respectively. The highest self-reported prevalence rates of OMSDs for taxi drivers were found for the lower back (60.7%) and lowest rates for the elbow (14.8%). Whereas, among office workers, the highest prevalence rates were found for the lower back and knee (29.4%) and lowest rates for feet/ankle (2.0%). The chi-square test found significant correlation between being immigrant (p=0.038), hours of driving per day (p=0.002), number of working days per week (p=0.000) with 1-year prevalence of OMSDs, while job experience (p=0.006), hours of driving per day (p=0.004) and break during work (p=0.029) showed significant correlation with perceived 1-week prevalence of OMSDs among taxi drivers in Jeddah.

This study aims to examine the occupational health and safety (OHS) status in motor vehicle repair workshops (MVRW) industry in the city of Jeddah, Kingdom of Saudi Arabia (KSA). An inspection tool composed of 10 OHS components and 69 items was employed through observations, interviews, walk through survey and focused group discussions. The data was collected from local workshops (LWs, N=62) and multinational companies' workshops (CWs, N=11). The mean positive response for OHS components among surveyed LWs and CWs was as follow; personal protective equipment's (PPEs) (28% and 61%), fire protection and emergency management (52% and 91%), provision of facilities (69% and 94%), electric safety (44% and 82%), general workshop safety (43% and 82%), housekeeping (18% and 84%), chemical exposure (16% and 69%), maintenance and services (54% and 86%), manual handling (84% and 100%) and tool safety (58% and 91%), respectively. The overall OHS mean positive response, complying best practices and regulations, of all OHS elements in LWs was 47% which was much lower than 84% positive response for CWs. The impact of OHS on workers' health was also discussed together with recommendations given for further improvement.

The concept of energy from waste is getting popular nowadays across the globe, as being capable of producing multi fuels and value-added products from different fractions of municipal solid waste (MSW). The energy recovery technologies under this concept are anaerobic digestion (AD), pyrolysis, transesterification, refuse derived fuel (RDF) and incineration. This concept is very relevant to implementation in countries like Saudi Arabia, who wants to cut their dependence on oil. Moreover, the waste to energy becomes the imperative need of the time because of new governmental policy ‘Vision 2030’ that firmly said to produce renewable energy from indigenous sources of waste, wind and solar and due to given situations of Hajj and Umrah with massive amounts of waste generation in a short period. This study focused on two waste to energy technologies, AD and pyrolysis for food (40% of MSW) and plastic (20% of MSW) waste streams respectively. The energy potential of 1409.63 and 5619.80 TJ can be produced if all of the food and plastic waste of the Madinah city are processed through AD and pyrolysis respectively. This is equivalent to 15.64 and 58.81 MW from biogas and pyrolytic oil respectively or total 74.45 MW of continuous electricity supply in Madinah city throughout the whole year. It has been estimated that the development of AD and pyrolysis technologies will also benefit the economy with net savings of around US $63.51 and US $53.45 million respectively, totaling to an annual benefit of US $116.96 million. Therefore, in Saudi Arabia and particularly in Holiest cities of Makkah and Madinah the benefits of waste to energy are several, including the development of renewable-energy, solving MSW problems, new businesses, and job creation and improving environmental and public health.

Small-scale industries account for a large proportion of jobs and play a vital role in most countries’ economic
growth and prosperity. Due to the very low use of personal protective equipment (PPEs), employees
are exposed to numerous physical, chemical, and accidental hazards in small-scale industries. PPEs
are very effective in minimizing occupational injuries, accidents, and other hazards which otherwise
result in substantial manpower and financial losses. The study objective was to assess the availability
and use of PPEs as well as self-reported occupational exposures among workers in surveyed small industries
in Jeddah. The study involved 102 workers from 28 small-scale industries (vehicle repair, welding,
and paint). A survey was conducted to gather data of socio-demographic characteristics, self-reported
occupational exposures, and frequency of PPEs used by workers. The occupational exposures (never
exposed, sometimes exposed and always exposed) were reported in percentages including; noise exposure
(19.6, 73.5 and 6.9%); dust/smoke exposure (9.8, 69.6 and 20.6%); vapors/fumes exposure (11.8, 60.8
and 27.5%); and direct sunlight (43.1, 56.9 and 0%), respectively. The reported use of different PPEs in
descending order was; knee joints mats (50%), welding shields (50%), safety glasses (33.3%), gloves
(27.5%), face masks (26.5%), safety shoes (10.8%) and earplugs/ muffs (8.8%). On the basis of this study
findings, hand hygiene and general OSH awareness like interventions can be developed which will help
in minimizing workplace exposures among small-scale industry workers.

Growing environmental concern and rapid consumption of poor biodegradable mineral oils have triggered the need for the development of eco-friendly biodegradable bio-based oils with low toxicity and excellent lubricating performance. The study aims to produce and evaluate the performance of date seed (Phoenix dactylifera L.) oil, which is abundantly available in the Middle East region, as an alternative bio-based lubricant. The optimum date seed oil (DSO) yield of 6% was achieved using solvent extraction of date seeds with particle size of 1 mm, hexane solvent to seed ratio of 6:1, and processing time of 18 hours. The physicochemical properties of the DSO were found such as its clear yellow color, density of 0.907 g/cm 3 , iodine value of 13.28 gl 2 /100 g, saponification value of 162.5 mg KOH/g, and acid value of 1.4 mg KOH/g. Moreover, fatty acid composition was analyzed employing quantitative gas chromatography (GC), and the oleic acid (41.1%), linoleic acid (21.4%), and palmitic acid (11.3%) were found to be the major unsaturated fatty acids. The pour and flash points were around-10°C and 140°C, respectively. Thermogravimetric analysis (TGA) revealed that the produced DSO is thermally stable at up to 300°C. The rheological properties such as viscosity (41.62 cSt at 40°C and 8.13 cSt at 100°C) and viscosity index 173 were also assessed. These properties along with tribological properties of the DSO were compared with other bio-based oils and commercial SAE20W40 mineral oil. Overall, the characteristics of the DSO showed good potential to be developed into a bio-based lubricant. Furthermore, its properties can be enhanced by adding suitable additives. The findings of this study will help in developing eco-friendly bio-based industrial lubricants.

Purpose The aim of this work was to investigate the influence of hydroxypropyl methylcellulose (HPMC) on the phase transformation and release profile of carbamazepine-nicotinamide (CBZ-NIC) cocrystal in solution and in sustained release matrix tablets. Methods The polymorphic transitions of the CBZ-NIC cocrystal and its crystalline properties were examined by differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Raman spectroscopy, and scanning electron microscopy (SEM). Results The apparent CBZ solubility and dissolution rate of CBZ-NIC cocrystal were constant in different concentrations of HPMC solutions. In a lower percentage of HPMC in the matrix tablets, the CBZ release profile of the CBZ-NIC cocrystal was nonlinear and declined over time. With an increased HPMC content in the tablets, the CBZ-NIC cocrystal formulation showed a significantly higher CBZ release rate in comparison with the other two formulations of CBZ III and the physical mixture. Conclusions Because of a significantly improved dissolution rate of the CBZ-NIC cocrystal, the rate of CBZ entering into solution is significantly faster than the rate of formation of the CBZ-HPMC soluble complex in solution, leading to a higher supersaturation level of CBZ and subsequently precipitation of CBZ dihydrate.

An increasing interest in biochar application has opened many multidisciplinary research areas in science. Biochar can be produced by thermochemical conversion of organic biomass in an oxygen-deficient condition. Extensive research has been conducted on the potential of biochar for agronomic applications, such as soil fertility improvement and carbon sequestration due to its specific mineralogical composition and long-term stability in the soil. Using biochar for environmental remediation has also been recognized recently as a promising area of research for its unique physicochemical characteristics, redox potential, and adsorption capacity. However, the published works are mostly focused only on the agronomic and environmental applications with little information presented to elucidate the different mechanisms involved. This study, therefore, aims to examine the influence of controlling parameters during biochar production, such as pyrolysis temperature, residence time, and types of feedstock on the characteristics of biochar. Various mechanisms explaining the potential of biochar for the environmental and agronomic applications are discussed in detail. The challenges faced in biochar development and its field applications for agronomic and environmental remediation purposes are also highlighted. Finally, recommendations for future research are given on the development of biochar with high redox functional groups and sorption potential as well as on understanding the behavior of biochar under the natural field conditions.

The Sustainable Development Goals (SDGs) established by the United Nations provide a comprehensive framework for a brighter tomorrow, encompassing crucial aspects such as renewable energy, clean water and sanitation, and responsible consumption. However, accomplishing these goals requires dedicated efforts over an extended period. An innovative
and effective solution to waste management and energy issues is the emergence of waste biorefineries. These advanced systems not only provide sustainable waste management and energy solutions, but they also have the potential to reduce poverty and hunger while supporting global economic growth initiatives.

As our world faces critical environmental concerns, such as climate change and serious health issues, a major shift in our production and consumption paradigms seems inevitable. One solution to achieve that would be extending waste-oriented biorefineries, converting waste into energy, power, and useful products in a circular economy context. In light of the above, this Research Topic focuses on the role of waste biorefineries in meeting the SDGs, where respected scientists share their insights on waste biorefineries’ status, advancements, and prospects. Through their contributions, readers can explore how these innovative systems can play a vital role in achieving SDGs, tackling pressing environmental and health issues, and creating a better future. The accepted articles in this Research Topic are categorized under the sections of (1) Technological innovations and advancements in biorefineries, (2) Biomass sourcing, characterization, and valorization, and (3) Sustainable systems, economic growth, and policy implications based on the relevancy of their Research Topic and aims.

The world is facing severe environmental challenges, including increasing consumption of fossil-based energy and its consequent devastative impact, i.e. global warming and climate change. Biofuels are promising alternatives to fossil fuels with tremendous environmental and socio-economic benefits. There has been a considerable deal of research and development carried out on the production of biofuels in the last 2 decades. However, there is still a huge potential for achieving more
cost-effective and efficient biofuel production processes through the application of nanotechnology. The exceptional properties of nanomaterials (nanocatalysts) such as high surface area, catalytic
performance, crystallinity, durability, energy storage capacity, etc. offer great potential for optimizing biofuel production systems. Nanocatalysts could also serve recovery, reusability, and recycling purposes.

This Research Topic is designed to attract the state-of-the-art recent developments in fabrication, modification, and optimization of advanced nanocatalysts and nanostructured materials for biofuel production processes (Figure 1). This Frontiers Research Topic has attracted and compiled 12 top quality research and review articles. The articles have been written by researchers and academics working in institutions at different countries across the world including Australia, China, Egypt,
Greece, India, Iran, Malaysia, Netherlands, Pakistan, Saudi Arabia and South Korea. The editorial team of this research topic is very grateful to all the authors for their excellent contributions and making the research topic successful.

Energy recovery from waste resources holds a significant role in the sustainable waste management hierarchy to support the concept of circular economies and to mitigate the challenges of waste originated problems of sanitation, environment, and public health. Today, waste disposal to landfills is the most widely used methodology, particularly in developing countries, because of limited budgets and lack of efficient
infrastructure and facilities to maintain efficient and practical global standards. As a consequence, the dump-sites or non-sanitary landfills have become the significant sources of greenhouse gases emissions, soil and water contamination, unpleasant odors, leachate, and disease spreading vectors, flies, and rodents. However, waste can be utilized to produce a range of potential products such as energy, fuels and value-added products under waste biorefineries.

A holistic and quantitative view, such as waste biorefinery, on waste management must be linked to the actual country, taking into account its socio-economic situation, local waste sources, and composition, as well as the available markets for the recovered energy and products. Therefore, it is critical to understand that solutions cannot be just copied from one region to the others. In fact, all waste handling, transportation, and treatment can represent a burden to the cities’ environment and macro and
micro economics, except for the benefits obtained from recovered materials and energy. Equally significant is a clear and quantitative understanding of the industrial, and public potential of utilizing recovered materials and energy in the markets as these can be reached without exacerbating the environmental issues using excessive transport.

The book explores new advancements and discoveries on the development of emerging waste-to-energy technologies, practical implementation, and lessons learned from sustainable waste management practices under waste biorefinery concept, which will accelerate the growth of circular economies in the world. The articles presented in this book have been written by expert researchers and academics working in institutions at different countries across the world including Germany,
Greece, Japan, South Korea, China, Saudi Arabia, Pakistan, Indonesia, Malaysia, Iran, and India. The research articles have been arranged into three main subject categories; 1) Resource recovery from waste, 2) Waste to energy technologies and 3) Waste biorefineries. This book will serve as an important resource for research students, academics, industry, policy makers, and government agencies working in the field of integrated waste management, energy and resource recovery, waste to energy technologies, waste biorefineries etc. The editorial team of this book is very grateful to all the authors for their excellent contributions and making the book
successful.