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Sustainable Engineering - Challenges and Opportunitiesfor Process Operation and Control

Bhavik R. Bakshi

William G. Lowrie Department of Chemical and Biomolecular EngineeringThe Ohio State University, Columbus, Ohio, USA

FOCAPO / CPC 2017Foundations of Computer Aided Process Operations / Chemical Process ControlLoews Ventana Canyon Hotel and Resort, Tucson, Arizona, January 8-12, 2017

Sustainable Engineering 1 / 25

Sustainability and Process Control

• Sustainability in process engineering

ProcessIntegration

WasteMinimization

PollutionPrevention

SustainableEngineering

• Initial efforts focus on design, followed by control

• Methods are developed to consider new systems, constraints, andobjectives

• Effect of Sustainable Engineering on Process Control• New “sustainable” processes are being developed, and present control

challenges• Key challenges for process control are associated with system

integration, pollution control, new technologies• Recently reviewed by Daoutidis et al. (Daoutidis, Zachar, Jogwar, J.

Proc. Cont., 44, 184-206, 2016)


Sustainability and Process Control - Process SystemsChallenges

Process Integration

• Control of distributed, multiscale systems

Process Intensification

• Novel sensors and control hardware

Emission and Effluent Management

• Objectives that cross regional and national boundaries

Renewable fuels

• Industrial scale use, balancing monetary and environmental goals

Daoutidis, Zachar, Jogwar, J. Proc. Cont., 44, 184-206, 2016


Sustainability and Process Control - Energy SystemsChallenges

Thermal Power Plants

• New technologies

• CO2 management

Renewable Electricity

• Addressing intermittency, storage

Distributed Energy Systems

• Operating for flexibility amidst uncertainty

Daoutidis et al. adopt a bottom-up view of the challenges

• Technologies → Sustainability

This presentation adopts a top-down view

• Sustainability → Technologies


Requirements for Engineering to Contribute toSustainability

A sustainable system,

1. Respects nature’s limits

2. Contributes to human well-being

3. Is socially acceptable

While meeting these requirements, problems must not shift outside thesystem boundary

• Spatial

• Temporal

• Disciplinary

• Flows

Bakshi, Gutowski, Sekulic, 2017


Process Engineering to Sustainable Engineering

Process

Equipment

Supply Chain

Enterprise

mm m km Mms

h

day

month

year

decade

• ProcessSystemsEngineering

• Expanding tolarger scales

• Includingecosystems

• So far, sustainable engineering has considered mostly linear andstatic systems



Process

Life Cycle

Economy

Equipment

Supply Chain

Enterprise

mm m km Mms

h

day

month

year

decade







Process

Life Cycle

Economy

Equipment

Supply Chain

Enterprise

mm m km Mms

h

day

month

year

decade

Site

Organism

Regions

Regions

Nation

Campus






Expanding to Larger Scales

LCA and footprintmethods consider largerspatial scales

• Reliance on linear,static and empiricalmodels

• Incorporated insustainable processdesign

• Process-to-Planet framework integrates nonlinear process modelswith models of the life cycle and economy (Hanes and Bakshi, 2015)

• Consequential LCA considers some temporal and cross-disciplinaryshifts


Process-to-Planet Framework

Equipment

Value Chain

Economy

min∑

x i ; min B(z)s;

s.t. X (z)s ≥ f ; H(z) ≥ 0

min p(z)s; min B(z)s

s.t. X (z)s ≥ f ; H(z) ≥ 0

• Policy Design

• Supply Chain Design

• Process Design

Hanes, Bakshi, AIChE J., 61, 10, 3332-3352, 2015


Process-to-Planet Framework

Equipment

Value Chain

Economymin

∑x i ; min B(z)s;

s.t. X (z)s ≥ f ; H(z) ≥ 0

min p(z)s; min B(z)s

s.t. X (z)s ≥ f ; H(z) ≥ 0

• Policy Design

• Supply Chain Design

• Process Design

Hanes, Bakshi, AIChE J., 61, 10, 3332-3352, 2015


Attributional and Consequential LCA

Life cycle

Env.ImpactTechnology

• Attributional LCA• Assumes full adoption of technology

• Attributional LCA• Assumes full benefit of technology


Attributional and Consequential LCA

Economicsystem

Life cycle



• Consequential LCA• Accounts for human behavior and economic rebound


Application - Gas Tax and Biofuel Subsidy

Goal

• Reduce national GHG emissions by specified quantity

Policy

• Impose 25 cents/gallon tax on gasoline

• Utilize tax revenue to subsidize biofuels

Approach

• Use economic input-output models to capture effect of tax

• Use elasticity of demand models to capture societal response toprice change

• Use Eco-LCA to determine life cycle impact of fuel substitution(http://resilience.osu.edu/ecolca)

Price_0Quantity_0Emission_0

PolicyMaker

Gasolinetax subsidizesbiofuel

Economy(Leontief

price model)Price_1Quantity_0Emission_0

Society(Elasticity of

demand)

Life Cycle(Eco-LCA)




http://resilience.osu.edu/ecolca

Results - Life Cycle Impact of Tax and Subsidy

Sulfur Dioxide (SO2)Carbon Monoxide (CO)Nitrogen Oxide (Nox)VOC (Volatile Organic Compound)Lead (Pb)

Particulate Matter (PM10)Carbon Dioxide (CO2)Methane (CH4)

Nitrous oxide (N2O)Hydrofluorocarbons (HFC)Methanol (CH4O)

Ammonia (NH3)Toluene (TOL)Trilchloroethane (TCE)Styrene (STY)

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8

Crude oilNatural gasCoalIron oreCrushed stoneSand

N deposition from atmCropland

TimberlandLand - urban & industrial

Detritus to agricultural soilWood

GrassFish and related species

Water (agriculture & livestock)Soil erosionPollination

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

Inputs from Nature Emissions to Nature

This policy need not meet the societal GHG reduction goal

Choi, Bakshi, Hubacek, Nader, Applied Energy, 184, 830-839, 2016


Including Feedback in LCA

Economicsystem

Life cycle




• Adaptive LCA• Ensures satisfaction of specified policy goal• Enables adaptive management• LCA with control can provide superior implementation of societal

goals


Including Feedback in LCA

Policymaker

Economicsystem

Life cycle

Env.Impact

DesiredImpact

Techno-logy



• Adaptive LCA• Ensures satisfaction of specified policy goal• Enables adaptive management• LCA with control can provide superior implementation of societal

goals


LCA with Control - Some Challenges

Need models of large systems

• Life cycle, economy, human behavior

Many methods and models are available

• Computable general equilibrium, system dynamics, agent-based, etc.

Several control strategies are relevant

• MPC, Robust control, Adaptive control, Nonlinear control

Need to integrate with conventional operation and control tasks

• Hierarchy of control and operation


Engineering and Ecosystems

Domination of Nature

• Respecting nature’s limits is a critical requirement for sustainability

• The aim of engineering has been to dominate and control nature

• Engineering has developed over the last few centuries while takingnature for granted and without considering it’s limits

Consequences of Taking Nature for Granted

• Unsustainable engineering due to ecological degradation andresource depletion

• Lost opportunities for innovation and sustainability

Grand Challenge

• Paradigm shift toward respecting and learning from nature

• Explicitly account for the role and capacity of ecological systems


Techno-Ecological Synergy

TechnologicalSystems

Products

Pollutants

Raw Materials

Wastes

• Eco-efficiency, life cycle design

• Circular economy, industrial symbiosis, byproduct synergy• Techno-ecological synergy• Sustainable TES

Bakshi, Ziv, Lepech, Env. Sci. Technol., 2015




Products

Pollutants

Raw Materials

WastesWasteConversion

• Eco-efficiency, life cycle design• Circular economy, industrial symbiosis, byproduct synergy

• Techno-ecological synergy• Sustainable TES





EcologicalSystems

Products

Pollutants

Raw MaterialsCo-benefits

Capital &Management

Wastes

EcologicalInputs

WasteConversion

NaturalResources

• Eco-efficiency, life cycle design• Circular economy, industrial symbiosis, byproduct synergy• Techno-ecological synergy

• Sustainable TES





EcologicalSystems

Products

Co-benefits

Capital &Management

Wastes

EcologicalInputs

WasteConversion

NaturalResources

• Eco-efficiency, life cycle design• Circular economy, industrial symbiosis, byproduct synergy• Techno-ecological synergy• Sustainable TES



TES at Equipment Scale: Ecosystems as Unit Operations

Electricity and steam

Coal CHP–steam&electricity

Baghousefilter

Wet FGD

SCR

Coal

Gypsum

Ammonia

Stackemissions(Co2,CO,SO2,

NO2,PM)

Ash

Unpolished stack emissions

Wastewater

Airemissions

Gopalakrishnan, Ziv, Bakshi, AIChE J., 2016


TES at Equipment Scale: Ecosystems as Unit Operations

Electricity and steam

Coal CHP–steam&electricity

Baghousefilter

Wet FGD

SCR

Coal

Gypsum

Ammonia

Stackemissions(Co2,CO,SO2,

NO2,PM)

Ash

Unpolished stack emissions

Wastewater

Airemissions

Wood/Biomass Forest

Rainwater

Wetland

Process water

Gopalakrishnan, Ziv, Bakshi, AIChE J., 2016


Assessing TES: Biodiesel Manufacturing Site


Biodiesel TES with Forest and Wetland

0.0

0.1

0.2

0.3

D S D S D S D S

kg/m

3of

bio

dies

el

D - Biodiesel process demand

0

10

20

D S

D - Utility generation demand

100

0

25

50

75

D S

NO2

SO2

O3

PM10

CO2

H2O

• 10 year-oldforest cancapture all NO2

and PM10

• 20 year-oldforest capturesall air emissionsexcept CO2

• 50 year-oldforest mitigates80% CO2 andH2O

Gopalakrishnan, Bakshi, Ziv, AIChE J., 2016


Biodiesel TES with Forest and Wetland

0.0

0.1

0.2

0.3

D S D S D S D S

kg/m

3of

bio

dies

el

D - Biodiesel process demand

0

10

20

D S

D - Utility generation demand

Supply over 10 years




100

0

25

50

75

D S

NO2SO2

O3

PM10 CO2

H2O • 10 year-oldforest cancapture all NO2

and PM10

• 20 year-oldforest capturesall air emissionsexcept CO2

• 50 year-oldforest mitigates80% CO2 andH2O

Gopalakrishnan, Bakshi, Ziv, AIChE J., 2016


Air Quality Regulation Across U.S.

Fraction of SO2 captured

> 100% 75-100%

50-75% 25-50% 0-25%

• Fraction of SO2 emissions taken up by current vegetation

• Vegetation can capture significant fraction of air emissions

• Ecosystem restoration is less expensive than technology for majorityof counties (indicated by gray counties)

• Can identify sectors that are “low hanging fruit” for policy makers



Sustainability Index

Local sustainabilityN/A -1 -0.75 -0.5 -0.25 0

Demand:13,747 MT/yr

Current supply:1543 MT/yr

Additional supply:1335 MT/yr

NO2

Demand:5330 MT/yr



PM2.5

Demand:5775 MT/yr



SO2

Current Potential


Demand:18,450 MT/yr


PM10

• Fraction of SO2 emissions taken up by current vegetation• Vegetation can capture significant fraction of air emissions• Ecosystem restoration is less expensive than technology for majority

of counties (indicated by gray counties)• Can identify sectors that are “low hanging fruit” for policy makers



Restoration cost (without land cost) > equipment cost

Restoration cost (without land cost) < equipment cost

• Fraction of SO2 emissions taken up by current vegetation

• Vegetation can capture significant fraction of air emissions

• Ecosystem restoration is less expensive than technology for majorityof counties (indicated by gray counties)

• Can identify sectors that are “low hanging fruit” for policy makers


Techno-Ecological Synergy of Processes

Diverse applications

• Biodiesel manufacturing

• Biosolids management inCentral Ohio

• Single-family home andyard

• Agricultural landscapedesign

Benefits of including nature in design

• Discovers innovative designs by expanding the design space

• New designs can be “win-win”

TES looks attractive, but how do we control and operate such systems?








Space of conventional designs

Cost

Env.Impact












Space of conventional designs

Cost

Env.Impact

Addi-tional design space due to TES






Characteristics of Technological and Ecological Systems

Properties Technological Systems Ecological Systems

Design approach Imposed-Design Self-Design





Control Externally imposed;centralized control

Endogenously imposed;distributed control







Abilities Rigid networks, can doa few things well

Flexible networks, cando multiple things









Inputs Concentrated, usuallyfossil resources

Dilute, renewableresources









Inputs Concentrated, usuallyfossil resources

Dilute, renewableresources

Availability Constant Intermittent


Homeostasis versus Homeorhesis

Atoms

Molecules

Cells

Tissues

Organs

Organ Systems

ORGANISM

• Process control isdirected towardhomeostasis

• Engineering attempts toimpose homeostasis onsystems that arehomeorhetic resulting inincreased variability inother systems

• Emergent propertiesalong the hierarchy

Such issues need to beaddressed in control andoperation of TES systems



Atoms

Molecules

Cells

Tissues

Organs

Organ Systems

ORGANISM

Set-point controlsfeedback (+ and -)maintaining steady states within limits

HOMEOSTASIS







Atoms

Molecules

Cells

Tissues

Organs

Organ Systems

ORGANISM

Populations

Communities

Ecosystems

Landscapes

Biomes

Ecosphere


HOMEOSTASIS







Atoms

Molecules

Cells

Tissues

Organs

Organ Systems

ORGANISM

Populations

Communities

Ecosystems

Landscapes

Biomes

Ecosphere


HOMEOSTASIS

HOMEORHESIS

No set-point controlsfeedback (+ and -)maintaining pulsing states within limits






Control of Manufacturing TES

Manufac-turingSystem

Wastetreatmenttechnology

Forest

Wetland

Products

Byproducts

WasteRawMaterials

RecycledWater

Biofuel


Control of Manufacturing TES

Manufac-turing

System

Wastetreatmenttechnology

FeedbackControl

Data Analysis

Sensors

Sensors

Forest

Wetland

Products

Byproducts

WasteRawMaterials

RecycledWater

Biofuel


Site-wide Control of Manufacturing TES

For sustainability, size of “site” can vary from local to global, dependingon ecosystem service

• Economic objective: Non-declining wealth (monetary value ofman-made and natural capital)

Wt =

∫ ∞t

U(Cτ )e−δ(τ−t)dτ

• Ecological objective: Non-decreasing resilience (change that can betolerated before system moves to another regime)

• Other objectives could be based on network metrics such as FisherInformation

TES systems are likely to have high uncertainty, nonlinearities, thresholdeffects


Summary

Sustainability requires PSE to

• Consider systems at larger scales, and

• Account for the role of nature

Existing efforts are mainly linear and static

• LCA may be formulated as a control problem to satisfy policy goals

• Need to incorporate life cycle objectives into process operationhierarchy

Techno-Ecological Synergies can provide “win-win” designs

• Need control strategies for integrating self-design withimposed-design

• Address high uncertainties, multiscale systems, threshold effects

Acknowledgments

• National Science Foundation, Dept. of Agriculture, Forest Service,Eastman Chemical, American Electric Power


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