Introduction to Sustainable Engineering

& Circular Economy Course (CE60214)

Spring 2025
Brajesh Kr Dubey, PhD, FIE, C.Eng
Professor – Environmental Engineering & Management
Chairperson – School of Water Resources
Humans on Earth
The Earth is 4.6 billion years old

1 second = 52,000 yr
1 minute = 3.125 Myr
1 hour = 187.5 Myr
Global population growth
Mid 2017
7,600,000,000

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Global population growth

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5
6
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 Urbanization

• ~1 % land surface BUT

• 60-70 % of anthropogenic greenhouse gas emissions
• Concentration of:
• Population
• Economic activities
• Demand for food, energy, water, materials

• Urban areas drive global land use changes

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 Urbanization

• Almost all population growth expected in cities &

towns of developing countries.
• By 2050:
• >70 % China’s population urban
• China +30 cities >1 million people
• >50 % India’s population urban
• India +26 cities >1 million people

• Urban growth will require 100-200 million hectares

(~equivalent to 2010 global urbanized area)
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1st August 2024

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Impact

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 Limits to Growth Model

13-01-2025 Source: Meadows,

Dr VR Sankar D.H.,
Cheela, Assoc. Meadows,
Professor, D.L., Randers, J. and Behrens III, W.W. (1972)
MVGRCE (A) 12
Overconsumption and excess waste lead to an unsustainable
planet
Source: Ismail Serageldin, 1993

INPUT RULE OUTPUT RULE

•RENEWABLES: Harvest rates • Waste and pollution from a
of resources must be within community must not exceed
the regenerative capacity of the assimilative capacity of its
systems that produce them. bioregion and must not
•NON-RENEWABLES: Rates of degrade future absorptive
depletion must not exceed capacity or any other
the rate at which ecologically important ecological services.
sound, long-term resource (Note: residuals exported
substitutes are developed. beyond the bioregion must be
accounted for)
For simplicity, use two data sets:
Energy Efficiency, Materials Resource Efficiency
Overconsumption
Global Annual Extraction of Natural Resources, 1900-2015

I. Marín-Beltrán et al., Science of the Total Environment

811 (2022) 151359

Increase in human population growth, Gross Domestic Product (GDP) and the extraction of natural
resources in 2015, relative to values reported in 1900. The black dashed line delimits the level above
which the increase in production of a given material is above the increase in human population growth.
Non-metallic minerals (NMM), Total primary energy supply (TPES)
More than needed…
• Goods produced (industrial machinery)
• Goods transported (freight modes)
• People travelling (passenger modes)
• Cooling used (ACs, fridges, industrial chillers)
• Heating used (heaters, furnaces, kilns, boilers)
• Fertilizer and pesticides used (agriculture)
• Power used (power plants, generator sets)
• Data usage ! (data centres) …
 What is a circular economy?
• A circular economy is a systemic approach to
economic development designed to benefit
businesses, society, and the environment.
• In contrast to the ‘take-make-waste’ linear model,
a circular economy is regenerative by design and
aims to gradually decouple growth from the
consumption of finite resources.
• A circular economy aims to redefine growth,
focusing on positive society-wide benefits. It
entails gradually decoupling economic activity from
the consumption of finite resources, and designing
waste out of the system.
Source: https://quantumpr.wordpress.com/2014/07/25/three-
reports-call-for-action-in-the-uks-circular-economy/
 Design out waste and pollution
What if waste and pollution were never created in the first place?
• A circular economy reveals and designs out the negative impacts of economic
activity that cause damage to human health and natural systems.
• This includes the release of greenhouse gases and hazardous substances, the
pollution of air, land, and water, as well as structural waste such as traffic
congestion.

Source: http://www.biokemi.org/biozoom/issues/546/articles/2531 Source: https://www.hsy.fi/en/experts/climatechange/Pages/circular-economy.aspx

 Regenerate natural systems
What if we could not only protect, but actively improve the environment?
• A circular economy avoids the use of non-renewable resources and preserves or enhances
renewable ones, for instance by returning valuable nutrients to the soil to support
regeneration, or using renewable energy as opposed to relying on fossil fuels

Source: Source:
https://www.researchgate.net/publication/319232712_Microbial_biotechnology_and_circular http://en.envirocitiesmag.com/articles/generating_economic_development_through_integ
_economy_in_wastewater_treatment/figures?lo=1 rated_waste_management/generating_revenue_from_waste_management.php
 Origin of circular economy

IMP

Swiss architect and industrial analyst

Walter R. Stahel is known as one of
the Founding Fathers of Circular
Economy
Source: https://www.ellenmacarthurfoundation.org/explore/the-circular-economy-in-detail Source: http://www.beastmagazine.lu/origins-circular-economy-dr-stahel/
 Circular
Economy
System
Diagram

Source: https://www.ellenmacarthurfoundation.org/circular-economy/concept/infographic
 Keep products and materials in use
What if we could build an economy that uses things rather than uses them up?
• A circular economy favours activity that preserve value in the form of energy, labour, and
materials. This means designing for durability, reuse, remanufacturing, and recycling to
keep products, components, and materials circulating in the economy.

• Circular systems make effective use of bio-based materials by encouraging many different
uses for them as they cycle between the economy and natural systems.

Source: https://circulareconomy.worldsteel.org/
 Past and projected future resource use in India
❑ Finite resources such as metals and minerals
will become more expensive as their
extraction becomes more difficult
❑ The resulting supply constraints will put great
pressure on productive sectors
❑ The future needs of India for resources and
its dimensions and challenges, such as
resource availability and access, affordability
and sustainability make it clear that resource-
efficient production processes and the use of
secondary materials are inevitable to meet

Past and projected future resource use in India (Source: based on data from both growing demand and supply constraints
Dittrich, 2012; SERI, 2012; World Bank, 2012; UN Population Statistics, 2012,
(FIRP, 2015)
IGEP 2013, Cited from: Framework for the Indian Resource Panel, 2015 )
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Example of CE Measurement Framework
Trends in Circular Economy
 Product-as-a-Service Models
• Shift from ownership to access.
• Key Industries
• Electronics, automotive, fashion.
Examples
• Lighting as a service (Phillips)
• Subscription-based fashion (H&M)

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 Closed-Loop Supply Chains
• Reusing, recycling, and refurbishing
products
• Importance of product design for
disassembly
Examples
• Patagonia Worn Wear program

13-01-2025 26
 Advanced Recycling Technologies
Integrated Circular Cascade Model in Borealis’ approach
• Beyond mechanical recycling to achieve circularity
• Types
• Chemical Recycling
• Biodegradable plastics
• Examples
• Textiles, Mixed-material recycling

https://www.borealisgroup.com/news/borealis-advances-plastics-circularity-with-the-first-of-its-
kind-borcycle-m-commercial-scale-advanced-mechanical-recycling-plant?id-media-
single=gallery-395666
13-01-2025 27
 Regenerative Design
• Restoring ecosystems and
increasing biodiversity
• Applications:
• Bio-based concrete, green building
integration
• Examples
• Biomason’s carbon-capturing bricks

Shanmugam et al., 2021, Circular economy in bio-composite

development: State-of-the-art, challenges and emerging
trends. https://doi.org/10.1016/j.jcomc.2021.100138
13-01-2025 28
 Digitalization and Data-Driven Circularity
• IoT, AI, and blockchain
• Benefits:
• Resource tracking, transparency, and
lifecycle optimization
• Examples
• AI for predictive maintenance.
• Blockchain for material traceability

Jose, R., Panigrahi, S.K., Patil, R.A. et al. Artificial Intelligence-Driven Circular Economy as a Key Enabler for
13-01-2025 Sustainable Energy Management. Mater Circ Econ 2, 8 (2020). https://doi.org/10.1007/s42824-020-00009-9 29
 Sustainable Business Models and Innovation
• Eco-design: Durable, repairable,
and recyclable products.
• Material efficiency: Reducing waste
generation
• Examples
• IKEA: Modular furniture designs.
• Nike: Recycled materials and closed-
loop manufacturing.

13-01-2025 30
 Circular Cities and Urban Sustainability
• Resource recovery, smart waste
management.
• Initiatives
• Amsterdam, Copenhagen.
• Urban mining

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 Consumer Education and Awareness
• Need for consumer participation in
circular models
• Methods:
• Campaigns and incentives
• Educational programs

13-01-2025 https://www.nature.com/articles/s43247-024-01663-6/figures/1 https://www.sciencedirect.com/science/article/pii/S0959652622051423#fig232

 Circular Finance and Investment
• Role of finance: Green bonds, impact
investing.
• Funding circular economy projects.
• Example
• Circular bonds for recycling infrastructure.

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 Institute-Industry-Government Collaboration

To develop research projects in Circular Development of policies, knowledge

Engineering and sustainability domain database and capacity building systems
Focus area: Focus area: Sustainability education
Circular Engineering and Sustainability

• National Institutes • Public-private partnerships

• International Institutes • Bi-lateral collaborations
• Research institutes
Incubation hub
Industry
Focus area: Sustainable Design and Circularity
• Development of solutions by application of sustainability design thinking, industrial
ecology principles and circular economy approaches
• Development of inventory database and performance indicators specific to Indian context
13-01-2025 34
 Hydrothermal carbonization (HTC)
•HTC, also referred to wet torrefaction, is a thermochemical process for converting wet
waste feedstock into a high carbon rich solid product called as “hydrochar” (Coalification)
•
•During the HTC process feedstock is mixed with the water and is heated in a closed
reactor at a temperature range of 180-300°C and under autogenouse pressure.

Wet Hydrothermal (HTC)

waste/Digestate carbonization

Hydrochar

Mimics the natural

Coalification process

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 Hydrothermal carbonization (HTC)

Sub critical water

Mimics the natural Coalification process

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Save Energy and Resource through HTC with different
feedstocks and integration approaches
Save Energy and Resource through HTC with different feedstocks, and
integration approaches : a zero-loss process
 Save Energy through HTC Modelling
Schematic of the HTC reaction pathway process
Areas that require further
investigation for computational models:

Input and output streams for HTC mass

balance:

Ubene, M.; Heidari, M.; Dutta, A. Computational Modeling Approaches of Hydrothermal Carbonization: A Critical Review. Energies
2022, 15, 2209. https://doi.org/10.3390/en15062209
 HTC of the organic fraction of MSW

Hydrochar Fuel Pellets

Yard Waste

Reactor

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Food Van Krevelen diagram
Pelletization using self design pelletiser

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Proposed framework

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Hydrothermal Carbonization of food waste in landfill leachate: an electrode
material for supercapacitor applications
Application of hydrochar
 Loop the waste into energy sector
Hydrothermal Carbonization _ Future of waste to energy
Recent Publication addressing Hydrothermal carbonization of organic waste
Media Coverage of Research
Applications that we are researching Waste heat recovery and reuse

currently and is planned for in near future Water

Bio-coke Treatment
Dry biomass for process heating recovery Heat &
Gas

Heat

Adsorbent
Functionalization

s
Targeted Kitchen / Food Hydrothermal Hydrochar Bio-Coal

Electrodes
Carbonization (HTC)
Waste

Catalysts
Processing Waste &

Adsorbents
yard waste

Fuel
Organic
Acid HTC Liquid Sodium Ion
CHP
Fermentation Catalytic
Synthesis Batteries

Liquid

Anaerobic
Solid

Fuel
Digestion
UF
Chromatographic Agrochemicals
separation Cleaning
Biogas /Upgrading Biomethane

Biochemical
Treatment
Lactic Acid
Co-polymerization

Biopolymer

Biomedical Bioelectricity,
Bioplastics Applications Plant Growth Acid and alkali Biofertilizer
Biocide Promoter recovery
 Waste treatment technologies

Plastic
Anaerobic Waste
Municipal digestion
yard
waste

Feedstocks
Pyrolysis Reactor

Hydrothermal carbonization reactor

Food
Waste
Agri-
Waste

Torrefaction 51
Valorization of organic fraction of municipal/agricultural solid waste by hydrothermal
carbonization

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Integrating hydrothermal carbonization and aqueous phase reforming for hydrogen
production by using modified alum sludge-based catalysts

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 Lab-scale biomanufacturer of Polyhydroxyalkanoates (PHAs) by hydrothermal processing
of Food waste

Hydrothermal Hydrolysis of Food Waste Synthesis of PHAs

Characterization of PHAs

Hydrochar Purify and characterize

alkaloids
Solids Modifying the crude
hydrolysate as culture media
for PHAs by C. necator
Extraction &
HTC Process optimization Purification Analyse surface morphology,
Liquid for PHA synthesis using mechanical and thermal
reactor Hydrolysate shake flask cultures properties
C source for
Collection of Hydrothermal Cupriavidus necator
FW
Assessing the
pre-treatment
environmental impact Biodegradability studies in
organic waste treatment
Characterization facilities (Anaerobic digestion
and Composting)
Optimizing the process parameters for hydrothermal
hydrolysis of FW
Scale-up studies in
Optimized conditions for maximum concentration of small-scale
fermentable sugars:- S:L ratio-1:5, Temperature- 180°C, fermenters (3 L)
LCA studies
Time-1 hour Anaerobic Digestion Composting

This Work is in collaboration with Bioprocess and bioproduct development laboratory (BBDL), IITKGP of Prof. R K Sen54
 Prospects of SUP-biochar composite as Solid Fuel and Soil amender
Properties
optimization

Application of Char in
commercial organic
olericulture
Physicochemical and Optimized Char
Thermal Characteristics +

Molasses
(Binder)

SUP Biochar Application of Char in

Composite phytoremediation of mine
Char Pellets as fuel in Char dumps
indigenously manufactured Pellets 55
Forced draft cooking stove
 Pretreatment strategies to improve biogas yield from lignocellulosic biomass

Electrochemical
Liquid hot water pretreatment pretreatment of yard
techniques waste to
Improve biogas
production

Anaerobic co-digestion of food

waste with pretreated Yard waste

Thermo-chemo-sonic
pretreatment of yard waste

Laccase mediated enzymatic

pretreatment of yard
waste
Electrolysis
pretreatment of
lignocellulosic
56 waste
Sustainability Assessment of waste treatment system- An Indian Case study

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Plastic waste generation and its fate and transport

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 Thank You

Circular Engineering Research Group (CERG)

 Thank you
Brajesh K Dubey, PhD, FIE, CEng.
Professor-Circular Engineering
Chair – School of Water Resources
Department of Civil Engineering, IIT-Kharagpur
bkdubey@civil.iitkgp.ac.in; bkdubey@gmail.com
+91-9434205884

http://scholar.google.ca/citations?user=gLXcah0AAAAJ
http://www.linkedin.com/pub/brajesh-dubey/0/883/716
https://twitter.com/wasteprof
Prof. Brajesh K Dubey