Dr Karthik Rajendran, Assistant Professor from the Department of Environmental Science, has added another paper to his list of publications. His paper titled Towards green whiskey production: anaerobic digestion of distillery by-products and the effects of pretreatment has been published in the Journal of Cleaner Production (Q1 category) with an impact factor of 9.2.

Abstract of the research

Using renewable biogas from anaerobic digestion of distillery by-products as a low carbon heat source can decarbonise the distillery process and support the distillery industry for a transition to a more sustainable production process. The study investigated the anaerobic digestion performance of different types of whiskey by-products and the effects of acid pre-treatment on the digestion of solid by-products. Results of biomethane potential assays showed that the methane yield from the unprocessed by-products was 330 mL/g volatile solids (VS) from draff, 495 mL/g VS from thin stillage, and 503 mL/g VS from thick stillage. For the processed by-products, the specific methane yield was 370 mL/g VS from cake maize, 382 mL/g VS from wet distillers’ grains with solubles (WDGS), and 545 mL/g VS from syrup. Acid pre-treatment (1% H2SO4 at 135 ◦C for 15 min) did not significantly improve the methane yield from solid by-products (such as draff and WDGS) but reduced the digestion time by 54.5% for cake maize. The microbial community analysis revealed that methane production from the untreated and acid-pre-treated solid by-products (draff and WDGS) was mainly through the hydrogenotrophic methanogenesis pathway. The gross thermal energy in the form of methane produced from 100 tonnes of mixed unprocessed by-products (draff, thin stillage, and thick stillage) was calculated as 24.4 MWthh equivalents to 60.6% of the thermal energy consumed in whiskey production, which affected the same percentage of CO2 emissions reduction.

Explanation of the research

Many industries meet their energy demand based on the fossil fuels such as coal, oil, and natural gas, which increases carbon dioxide emissions. Alcohol production is one of the heavy fossil fuel using industries, especially in distillation. The waste after alcohol production can be used to produce methane, which can be used as energy in distillation, reducing the need for energy consumption. By consuming the waste and producing energy, up to 60% of thermal energy could be reduced. This also reduces the CO2 emission by 60%. Alcohol industries can use their waste to decarbonise the energy demand, thus meeting the net-zero. India is expected to reach net-zero by 2070, which will be a bigger addition as a part of it.

In this research, Dr Karthik Rajendran has collaborated with Professor Jerry Murphy, UCC, Ireland, and Dr Richen Lin, UCC, Ireland. Applying the similar concept in the Indian context is his future plan for this research.

Water pollution continues to be one of the serious concerns facing the country. The ensuing scenario of eutrophication and harmful algal blooms has exacerbated the menace. This demands wholescale water management techniques to segregate the pollutants, retrieve useful nutrients, and treat the water effectively for sustainable use. Dr Karthik Rajendran and his PhD scholar, Mr Sarath Chandra, from the Department of Environment Science have published a paper discussing various nutrient recovery methods and their consequential outcomes. The research was done in collaboration with Dr Deepak Kumar from SUNY College of Environmental Science and Forestry, Syracuse, NY and Dr Richen Lin from Southeast University, Nanjing, China.

The article titled, “Nutrient recovery from wastewater in India: A perspective from mass and energy balance for a sustainable circular economy” was published in Bioresource Technology Reports (Q1 Journal), having an Impact Factor of 4.41. Their research investigates the possibilities of recovering Nitrogen (N) and Phosphorous (P) from wastewater in terms of technology, energy, and economic point of view. Excessive presence of Nitrogen and Phosphorous can result in eutrophication and algal blooming. These nutrients also pose a harmful threat to infrastructure. Nutrient recovery can mitigate these challenges and improve the quality of water.

Phosphorus is one of the limited resources available on earth and a key ingredient in fertilizer production. The recovery process also helps in transforming wastewater into resource pools that can efficiently churn out valuables that hold the key to a sustainable future. This will help reduce the imports of fertilizers and bring down the emissions to half in producing fertilizers. Their findings will also pave the way for making necessary policies to reduce water pollution and recover nutrients. As two-thirds of wastewater remains uncollected, they claim that effective treatment and water management practices can save around 800 crores per annum. Their future research plan also includes the experimental analysis of the nutrient recovery system.

Abstract of the Research

Wastewater (WW) is a potential source to recover N, and P, whereas, in India, it is scarcely explored. In this work, four different nutrient recovery methods were compared from a mass- and energy-balance perspective to understand the overall process flow. From 1000-m3 WW, chemical precipitation yielded 33.8 kg struvite, while micro-algae resulted in 299.1 kg (dry powder). Energy consumption was lowest for the fuel cells at 216.2 kWh/1000 m3, while microalgae used the highest energy at 943.3 kWh/1000 m3. Nonetheless, the cost-saving analysis showed that microalgae (78.6$/1000 m3) as a nutrient recovery choice, had higher savings than any other methods compared. For a country like India, where two-thirds of urban wastewater is untreated, wastewater-biorefinery options such as nutrient recovery hold the key to a sustainable circular economy.

The paper titled “An invasive shrub Lantana camara L. alters the flora and soils in tropical dry deciduous forests of Central India” has been published by Dr Javid Ahmad Dar, Assistant Professor of Environmental Science at SRM University-AP, in “Biotropica” having an impact factor 2.508 (Q1 Journal).

Abstract

The findings of this research reveal how an invasive shrub Lantana camara L. significantly alters the flora and soils in tropical dry deciduous forests of Central India and suggested long-term monitoring studies and proper management strategy.

Practical implementation

The findings would be helpful to forest managers, scientists and policymakers for better understanding, management, and restoration of the invaded landscapes in tropical forest ecosystems.

Collaborations

Prof M. L. Khan, Department of Botany, Dr Harisingh Gour Vishwavidyalaya (A Central University), Sagar, Madhya Pradesh, India.
Prof Raman Sukumar, Centre for Ecological Sciences, Indian Institute of Science (IISc), Bengaluru, India.
Prof Mukund Dev Behara, CORAL, Indian Institute of Technology, Kharagpur, West Bengal, India.
Prof S. M. Sundarapandian, Ecology and Environmental Sciences, Pondicherry University, Puducherry, India.

Future research plans:

Dr Javid Dar’s research plan for the next five years is to bring together several unique aspects of forest ecology which will be focused on carbon dynamics, mortality, microbial diversity and their relationship in shaping the structure and functional aspects of different forest ecosystems in the on-going and future climate change. Another major aspect of the research will be, to focus on ecophysiology and plant functional trait analysis in forest ecosystems as they are vulnerable to climate change and to see the impacts of climate change on diversity, productivity and stand structure in tropical and temperate forest ecosystems.

Dr Pankaj Pathak from the Department of Environmental Science has been keenly involved in research studies involving solid waste management and the effective conversion of wastes to energy. Her latest research publication ‘A comprehensive review on integrative approach for sustainable management of plastic waste and its associated externalities’ in the journal Science of the Total Environment (Impact Factor: 10.973) proposes enhanced solution for the sustainable management of plastic wastes. The article was published in collaboration with her PhD Scholar MSSR Tejaswini, Prof Sreeram Ramakrishna from the Centre for Nanofibers and Nanotechnology, National University of Singapore and Dr P Sankar Ganesh from BITS Pilani, Hyderabad.

Abstract of the Research

The management of post-consumer discarded plastic wastes (PCPW) creates new challenges in developing countries due to the lack of amenities, technological interventions, and associated negative environmental externalities. The fate of untreated recyclable and non-recyclable plastic wastes lies in open dumping along with other solid waste, and improper management leads to environmental externalities such as pollution, global climate change, and health issues. Additionally, open dumping upsurges the emerging microplastics and nano plastics (MNPs) contaminants. The externalities depend on the waste generating sources (household, industries, commercial), waste composition, and its characteristics. However, urban mining can minimize environmental externalities where waste plastics can convert into potential anthropogenic resources and also helps in achieving the target of sustainable development goals (SDGs 11 & 12). Moreover, various treatment technologies that help in the sustainable utilization of plastic wastes are extensively reviewed in this study and evaluate the costs benefits arising during various stages of treating plastic waste through recycling (R), incineration (I), and landfilling (L). The recycling of plastic waste has demonstrated the lowest impact on global warming potential (GWP) and total energy use (TEU), followed by landfilling and incineration (R < L < I). Nevertheless, when energy is recovered from inert (non-recyclable) plastic waste in the form of fuel or by its utilization in construction purposes, the environmental impacts are more negligible (Incineration < Landfilling). Therefore, this study determines the significance of circular economy with legislative approach and standards on plastic waste management, which help in reducing environmental externalities besides yielding a secondary resource as energy and materials through urban mining. A sustainable plastic waste management (SPWM) model is proposed for developing countries to convert plastic waste into resources and use it as a sustainable tool in urban mining.

Yet another article, ‘Comprehensive technological assessment for different treatment methods of leather tannery wastewater’, co- published by Dr Pankaj Pathak along with a group of other researchers was featured in the journal Environmental Science and Pollution Research having an Impact Factor of 5.19. The work offers some exhaustive observations and recommendations that could be helpful in the industry to manage tannery wastewater and recirculate the water in a sustainable manner.

Abstract of the Research

The leather-making process necessitates large amounts of water and consequently generates tons of liquid waste as leather tannery wastewater (TWW) is disposed of directly in the open environment. Open disposal of untreated TWW into the natural environment causes an accumulation of various polluting compounds, including heavy metals, dyes, suspended solids inorganic matter, biocides, oils, tannins, and other toxic chemicals. It thus poses potential hazards to the environment and human health. This study primarily focuses on providing in-depth insight into the characteristics, treatment strategies, and regulatory frameworks for managing TWW in leather processing industries. Different technologies of conventional physico-chemical (equalization, coagulation, and adsorption), advanced approaches (Fenton oxidation, ozonation, cavitation), thermo-catalytic and biological treatments available to treat TWW, and their integrative approaches were also highlighted. This review also sheds light on the most frequently applied technologies to reduce contaminant load from TWW though there are several limitations associated with it such as being ineffective for large quantities of TWW, waste generation during treatment, and high operational and maintenance (O&M) costs. It is concluded that the sustainable alternatives applied in the current TWW technologies can minimize O&M costs and recirculate the treated water in the environment. The exhaustive observations and recommendations presented in this article are helpful in the industry to manage TWW and recirculate the water in a sustainable manner.

Worldwide, 1.3 billion tons of bio-waste are generated annually. By 2025, this is predicted to be increased by 2.2 billion tons/year. The emerged biowaste biorefinery has proved as a sustainable approach for integrated bioproducts, such as bioenergy, biopolymers, biochemicals, bioplastics, and biofertilizers further used for industrial, commercial, agricultural, and energy applications. Integrating biorefinery concepts into biowaste management is promising for a circular bioeconomy. Recent research at the Department of Environmental Sciences investigates the potential of sustainable biorefinery approaches. Assistant professor Dr Karthik Rajendran and his PhD scholar Mr. Prabakaran G published a paper, Sustainable biorefinery approaches towards circular economy for conversion of biowaste to value added materials and future perspectives, in Fuel, a Q1 journal, with an impact factor of 8.03. For this paper, they have collaborated with Dr Mukesh Kumar Awasthi from the College of Natural Resources and Environment, Northwest A&F University, China.

Biorefinery is designed to improve the economic potential and achieve a circular bioeconomy by integrating various technologies such as pyrolysis, anaerobic digestion, gasification, incineration, and aerobic composting to gain energy, nutrients, and material recovery. Biowaste biorefinery contributes as a driving force to cope with challenges of resource scarcity, climate changes, and increased demand. The sustainable biorefinery approaches toward circular bioeconomy require a comprehensive understanding of the biowaste across the value chain. Based on the carbon neutralized biowaste biorefinery concept, this paper explained biowaste generation and utilization as a renewable resource through biorefinery techniques from the perspective of energy, nutrients, and material recovery. Meanwhile, clarify the implementation status, public engagement, and prospects of biowaste recycling with the central concept of biorefinery circular bioeconomy.

Abstract

With the colossal energy demand inevitably exacerbating the non-renewable resources depletion and ecological-social challenges, renewable energy has become a crucial participant in sustainable strategy. Biorefinery emerged as a sustainable approach and recognized promising transformation platforms for products to achieve a circular bioeconomy that focuses on biomass efficiency and sustainable valorisation, promotes resource regeneration, and restorative. The emerged biowaste biorefinery has proved as a sustainable approach for integrated bioproducts and further applied this technology in industrial, commercial, agricultural, and energy sectors. Based on carbon-neutral sustainable development, this review comprehensively explained biowaste as renewable resource generation and resource utilisation technologies from the perspective of energy, nutrient, and material recovery in the concept of biorefinery. Integrating biorefinery concepts into biowaste management is a promise for the conversion of biowaste into value-added materials. It contributes as a driving force to cope with resource scarcity, climate changes, and huge material demand in a circular bioeconomy. In practice, the optimal of biorefinery technologies depends on environmentally friendly, economic and technical feasibility, and social and policy acceptance. Additionally, policy interventions are necessary to promote biowaste biorefinery implements for a circular bioeconomy and contribute to a low-carbon cleaner environment.

Read the full article here.

Rampant exploitation of resources has indisputably contributed to an enormous rise in solid waste generation. It has been estimated that solid waste generation will shoot up from 1.3 billion tons to 2.2 billion tons in 2025. While 16% of the high-income countries’ population corresponds to 34% of waste being generated, only 5% of the waste generated is attributed to the low-income countries. However, it is a meagre volume of 39% that is collected leaving the rest to rot. This open dumping affects the environment and creates pollution. In addition, improper waste disposal techniques have resulted in emissions of 1.6 billion tons of CO2eq in 2016. Effective waste management is thus a matter of concern in third-world countries.

Assistant Professor Dr Karthik Rajendran and his post-doctoral scholar Dr V S Vigneswaran from the Department of Environmental Science in collaboration with Dr Mukesh Kumar Awasthi from the College of Natural Resources and Environment, Northwest A&F University, PR China, have published their research papers on solid waste management in the journal Bioresource Technology having an Impact Factor of 11.8. This is the second-best journal in the Environmental Engineering category according to SCImago Journal Rank (SJR). The journal aims to disseminate knowledge in the areas of biomass, biological waste treatment, bioresource systems analysis, and technologies associated with conversion or production.

The paper titled “Recovery of value-added products from biowaste: A review” introduces microbial biotechnology for the valorisation of solid wastes. Microbial biotechnology offers several solutions for the utilisation of waste resources. The carbon present in solid and gaseous wastes can be utilised by the microbes as carbon feedstock for their growth. During the growth of microbes on wastes, it produces primary and secondary metabolites, which are of significant use to humankind. The microbes can also be engineered biotechnologically to use waste resources and produce new compounds. Microbial biotechnology, with the use of various genetic engineering tools, can be efficiently explored for the microbes’ modification to utilise different wastes thereby making the environment clean by reducing GHG emissions.

Abstract of the Research

This review provides an update on the state-of-the art technologies for the valorization of solid wastes and its mechanism to generate various bio-products. The organic content of these wastes can be easily utilized by the microbes and produce value-added compounds. Microbial fermentation techniques can be utilized for developing waste biorefinery processes. The utilization of lignocellulosic and plastic wastes for the generation of carbon sources for microbial utilization after pre-processing steps will make the process a multi-product biorefinery. The C1 and C2 gases generated from different industries could also be utilized by various microbes, and this will help to control global warming. The review seeks to expand expertise about the potential application through several perspectives, factors influencing remediation, issues, and prospects.

Read the full article here

Food waste in solid forms has been generated throughout the entire food life cycle, from the agricultural production process to the distribution of processed foods and even to their consumption in the market. Considering that approximately 1.3 billion tons of edible food waste is leftover annually, recycling it in the biorefinery will contribute both economically and socially. Another of their publication “Myco-biorefinery approaches for food waste valorization: Present status and future prospects” discusses various types of food waste sources and their evaluation targets. Food waste can be evaluated in fungi-based bioproduction processes for this purpose. In addition, potential biorefinery systems, circular bioeconomy processes, techno-economic studies, and social/ethical aspects of food wastes in the evaluation of valuable products are discussed.

Abstract of the Research

The increase in population and urbanization leads to the generation of a large amount of food waste (FW) and its effective waste management is a major concern. Its putrescible nature and high moisture content are the major limiting factors for cost-effective FW valorization. Bioconversion of FW for the production of value-added products is an eco-friendly and economically viable strategy for addressing these issues. Targeting the production of multiple products will solve these issues to a greater extent. The article provides an overview of the bioconversion of FW to different value-added products.

Read the full article here

Dr Pankaj Pathak from the Department of Environmental Science has been keenly involved in research studies involving solid waste management and the effective conversion of wastes to energy. Her latest research publication Sustainable approach for valorization of solid wastes as a secondary resource through urban mining proposes an enhanced solution for the sustainable management of different types of solid wastes. It was published in the Journal of Environmental Management with an impact factor 8.98.

In this paper, sustainable alternative valorisation techniques that aid in maximum recovery from waste materials, and associated challenges and limitations have been highlighted. These solid wastes mainly include construction and demolition wastes, organic food wastes, plastic, and WEEE (Waste electrical and electronic equipment) from various sources. In order to overcome these challenges, a sustainable circular model is recommended in this paper that will help minimise the negative environmental impacts, maximise the life cycle of material, reduce the consumption of fossil fuels, and thereby sustainably manage waste. Implementation of this recommendation can help in achieving the target of sustainable development goals (SDGs).

The article was published in collaboration with her PhD Scholar MSSR Tejaswini, and D.K. Gupta, Member Secretary in the Hazardous Substance Management Division in the Ministry of Environment, Forest and Climate Change, New Delhi.

Abstract

The incessant population has increased the production and consumption of plastics, paper, metals, and organic materials, which are discarded as solid waste after their end of life. The accumulation of these wastes has created growing concerns all over the world. However, conventional methods of solid waste management i.e., direct combustion and landfilling have caused several negative impacts on the environment (releasing toxic chemicals and greenhouse gases, huge land use) besides affecting human health. Therefore, it is requisite to determine sustainable alternative technologies that not only help in mitigating environmental issues but also increase the economic value of the discarded solid wastes. This process is known as urban mining where waste is converted into secondary resources and thereby conserves the natural primary resources. Thus, this review highlights the technological advancements in the valorisation process of discarded wastes and their sustainable utilization. We also discussed several limitations of the existing urban mining processes and further the feasibility of valorisation techniques was critically analysed from a techno-economical perspective. This paper recommends a novel sustainable model based on the circular economy concept, where waste is urban mined and recovered as a secondary resource to support the united nations sustainable development goals (SDGs). The implementation of this model will ultimately help the developing countries to achieve the target of SDGs 11, 12, and 14.

The different dimensions of sustainable waste management have always been explored by researchers all over the world. Assistant Professor Dr Pankaj Pathak, Department of Environmental Science, has been actively involved in this research area for a while. Her paper titled Dual role of grass clippings as buffering agent and biomass during anaerobic co digestion with food waste is published in the journal Clean Technologies and Environmental Policy with an impact factor 4.7. Dr Pankaj Pathak co-authored the paper with Debkumar Chakraborty, Sankar Ganesh Palani, M M Ghangrekar, and N Anand.

Abstract

There is a dire need to replace the chemical buffers that regulate the redox environment in single-stage anaerobic digestion of food waste. Hence, the applicability of grass clippings as an eco-friendly buffering agent and biomass during the anaerobic co-digestion of food waste was explored. A focus was primarily given on the effects of grass clippings on the redox environment and acidogenesis. Concomitantly the production of volatile fatty acids, hydrogen, and methane in mesophilic conditions was monitored. Organic load and substrate-to-inoculum ratio were kept constant in all the experiments, and no chemical buffer was used. The results revealed that the redox environment was regulated with 10% grass clippings by inhibiting rapid pH drop in the digester. The addition of 2, 4, and 6% grass clippings promoted acidogenesis with increased production of acetic and butyric acids, whereas 8 and 10% grass clippings promoted solventogenesis with ethyl alcohol production. Hydrogen generation from the experiments with grass clippings was in the range of 27–30% of the total biogas, which was marginally higher than the control (25%). Methane concentration was negligible in the biogas generated from all experiments. The acidification rate, VFA production/consumption rate, specific hydrogen yield, hydrogen conversion efficiency, and volatile solids removal were maximum and minimum in the reactors with 6 and 10% grass clippings, respectively. From the above results, it can be concluded that adding grass clippings to food waste would regulate the sudden pH changes and enhance the production of value-added biochemicals, making the process cost-effective.

Dr Pankaj Pathak, Assistant Professor, Department of Environmental Science co-edited the book “Circular Economy in Municipal Solid Waste Landfilling: Biomining & Leachate Treatment: Sustainable Solid Waste Management: Waste to Wealth” in collaboration with Prof Sankar Ganesh Palani from BITS Pilani, Hyderabad. The book was released as part of the Springer publication series ‘Radionuclides and Heavy Metals in the Environment’ that covers issues pertaining to environmental pollution of air, water and soil, causative toxic agents, including radioactive materials, and remediation strategies.

The book is a ready reckoner of contemporary information regarding municipal solid waste landfill biomining, treatment of landfill leachate and heavy metals in a single platform. Construction of new landfills which requires huge monetary investments can be avoided if old landfills were bio-mined for resources and the space can be re-used as new landfills. Landfill leachate is a hazardous waste which needs proper treatment that could generate value-added products such as clean energy and biofertilizers. The book is a rich repository of information for academicians, researchers, and students at master’s and doctoral levels to understand the current trends in municipal solid waste landfill operations.

It also features the chapter, ”Valorization of Solid Waste from Landfill Activities” co-authored by Dr Pankaj Pathak and her PhD scholar MSSR Tejaswini along with Prof Sankar Ganesh Palani and Dr Prangya Ranjan Rout from Thapar Institute of Engineering and Technology. The article states that urban mining of various types of landfill wastes helps in the conservation of natural resources as well as increases the economic value of the disposed of wastes. It also ensures maximum recovery from the wastes that can be used as a secondary raw material for production purposes. Accordingly, they determine the environmental impacts associated with landfill wastes and identify different technologies that would help in the conversion of waste into resources through urban mining.

Essentially the book provides a circular economy approach to municipal solid waste (MSW) management. It also reviews the current technologies and future trends in MSW treatment by focusing on technological solutions for MSW treatment in developing countries in comparison with developed countries.