integrated hybrid life cycle optimization for multi-scale

Integrated Hybrid Life Cycle Optimization for Multi-Scale Sustainability Analytics of

Energy Systems

Fengqi YouRoxanne E. and Michael J. Zak Professor

Process-Energy-Environmental Systems Engineering (PEESE)School of Chemical and Biomolecular Engineering

Cornell University, Ithaca, New York

www.peese.org

3rd SEE SDEWES, Novi Sad, July 2018

Environmental Sustainability Issues

2

Life Cycle Analysis (LCA) – “Cradle to Grave”

3

Life Cycle Analysis (LCA)

4

• Quantifying environmental impacts of complex systems• Modeling the entire product/process life cycle• Holistic view of the system

Life Cycle Analysis

Life Cycle Optimization (LCO)

Integrating life cycle analysis approach with multi-objective optimization techniques

Life Cycle Analysis

5

Life Cycle Optimization: Theory and Methods

6

• Life Cycle Optimization▪ Life Cycle Analysis + Techno-economic Analysis + Design Optimization

Process Analysis

Process Design

Process Optimization

Life Cycle Analysis

Sustainable Design

Life Cycle Optimization

• Research Challenges▪ How to seamlessly integrate LCA into process systems optimization?▪ How to define the “optimal” systems boundary and functional unit?▪ How to incorporate state-of-the-art inventory analysis methods in LCO?▪ How to deal with uncertainty and solve large-scale LCO problems?

Process-based Life Cycle Optimization (LCO)

• Systems boundary must be defined in Phase I of LCA• Functional unit serves as the basis for calculation and comparison

Life Cycle Analysis

7

• Algae• Microalgae, cyanobacteria, & macroalgae• Non-food; high yield; rich in oil

• Algae-based biorefinery• Consume and utilize CO2; recycle nutrients & water• Produce fuels and value-added products• Process economics? Environmental sustainability?

Motivation

Chlorella Vulgaris

Biofuels

Bioproducts

8

• Optimal design and synthesis of algal biorefinery• Selection of technology, pathway, and processing methods• Determination of product portfolio under the given feed• Recycling nutrients, water and carbon dioxide• Mass balance, capacity, and equipment sizing• Energy and utility consumption• Process economics ? Techno-econmic analysis• Environmental sustainability ? Life cycle analysis• Cost-effective & sustainable design

Algal Biorefinery Process Design and Optimization

9

LCO for Sustainable Design of Energy Systems

10Gong & You (2015). Current Opinion in Chemical Engineering, 10, 77-86.

Superstructure of Algae Process

Harvesting

Lipid extraction

Biofuel production Bioproduct manufacturing

Remnant treatment

Cultivation

HydrogenPropylene glycol

Glycerol-tert-butyl etherPoly-3-hydroxybutyrate

BiodieselDiesel

Biogas utilization

11


<1,2> Flat plate photobioreator

<1,3> Bubble column photobioreator

<1,4> Tubular photobioreator

7,800+ processing pathways12

Optimization Model: Constraints for ONE Unit

{ }

,

,0

1, 0,1

4 defk de k

def DEde k d

de DE

de DE

e

DE DEde de

m m

m y UB

y y

∈

∈

=

≤ ≤ ⋅

= ∈

∑

∑( )

,/ /∈

+ ⋅ ⋅ = +

= ⋅ +

= ⋅∑

1 OP OP 1 2 OG1k k 2 k k

OG1 OP 2 OG1k k k k

steam1 SC C buf1 ms k

k Kk k

m SC X m m m

m SF m m

m MW R N m MW

• Technology selection • Mass balance and unit sizing

• Electricity

• Heating utility

• Cooling utility

( )∈

∈

=

= ⋅ ⋅ + ⋅

∑

∑

pce

turbine buf ng ng1

p

k co

ce PCE

k Km,k k

pct pc

ppt Y LHV m WF m

∈

= ⋅ ⋅ ⋅ ⋅

= ⋅

∑HE HChce1 hce1 k h

k Kce1,k

hce2 hce2 hce2

hc1 Y UC DTH CP mhc1

hc2 UHC mhc2

∈

= ⋅ ⋅ ⋅ ⋅

= ⋅

∑HE HCcce1 cce1 k c

k Kce1,k

cce2 cce2 cce2

cc1 Y UC DTC CP mcc1

cc2 UCC mcc2

= ⋅

sfequP CEPCI

equ equeccbequ equ mfb CEPCIB

equ equ

m Pecc P

P P

( )( )

1

1 1∈

⋅ + = ⋅ + ⋅

+ − ∑

LS

equequ

SE

LQU

IR IRaic K ecc lc

IR

= + + +aoc fsc utc omc wc

• Equipment capital cost

• Annualized investment cost

• Annual operating cost

= + +rma tran maghg ghg ghg ghg

• Greenhouse gas emissions

Mass and material balanceProcess network design specifications

Technology and pathway selectionEquipment sizing and capacity

Energy balanceUtility consumption

Techno-economic analysis

Life cycle environmental impact analysis

13

• Objectives:• Minimize: Unit cost of fuel product (techno-economic analysis)

• CAPEX + OPEX• Credit from selling by-products (glycerol, fertilizer, biogas, …)

• Minimize: Unit life cycle GHG emission (life cycle analysis)• Direct emissions: Cultivation, remnant treatment, & utility generation• Indirect emissions: External utility, e.g. electricity and steam, …

Optimization Model: Objectives

Systems boundary and life cycle stages of LCA

14

Pareto Optimal Curve

Minimum unit GWP

Minimum unit annualized cost

)

15

Pareto Optimal Curve

Minimum unit GWP

Minimum unit annualized cost

)

16


Harvesting

Lipid extraction Biofuel production Bioproduct manufacturing

Remnant treatment

Cultivation

Biogas utilization

17

2.71 – 3.78 14.43 Petroleum-derived diesel

Optimal Design of Minimum Unit Biofuel Cost

Unit cost of biofuel ($/GEG)

Unit GHG emissions (kg CO2-eq/GEG)

Biodiesel Throughput

(million GGE)Bioproduct

2.79 7.21 47 Propylene glycol

18

GWP of Algae-based H2, PHB, Propylene Glycol

Alternative bio-based propylene glycol is derived from soybean by ADM(R).

63%

51% 6%

19

ACS Sustainable Chem. Eng. 2015, 3, pp 82−96

20

Alternative approaches for Life Cycle Inventory (LCI) analysis• Process-based LCA• Economic Input-Output (EIO)-based LCA• Hybrid LCA

Hybrid Life Cycle Optimization (h-LCO)

21

(most widely used)(for macroscopic analysis)(state of the art)

Process-based LCA

22

Process-based

Resolution Process Sector Process (foreground)Sector (background)

Construction Bottom Up Top Down Hybrid

Scope Selected Processes Entire Economy Entire Economy

Process system boundary

Detailed process inventories

EIO-based LCA

23

Process-based EIO-based




Entire macroeconomy

Transactions among sectors

Sectors:Agriculture, mining, construction, manufacturing, wholesale trade, retail trade, transportation, etc.

Integrated Hybrid LCA

24

Process-based EIO-based Integrated Hybrid




Insights into Different LCA Approaches

25

Process-based LCA

26

Drawbacks:• System boundary truncation• Underestimation of the true impact

Advantage:• Specificity of process analysis

EIO-based LCA

27

Drawbacks:• Loss of precision at process level

Advantage:• Completeness of life cycle boundary


28

Integrates process- and IO-based LCA

Advantages:• Completeness of life cycle boundary• Specificity of foreground processes

Toaster Example

29

(Functional unit: produce 1,000 pieces of bread)Comparing two toasters

Toaster Example

30

Processes SectorsPr

oces

ses

Sect

ors

AA ABB B

Toaster Example

31

18.7 17.7Direct emission

(process system)

Toaster Example

32

18.7 17.7

27.2 27.3

Direct emission (process system)

Full emission(process + IO systems)

Neglectedindirect emission

(IO system)34% 35%


33

I1

I2

IM

…

Inputs

P_B2P_B1 P_BK

P_N2

…

P_N1 P_NK

…

…

……

P_A2P_A1 P_AK…

Processes

O1

O2

OP

…

Outputs

Processes Systems

S1

S2

S3

Sn

S1

S2

S3

Sn

Economic Input-output SystemsUpstream cutoffs

Downstream cutoffs

Sectors SectorsIntegrated Hybrid LCA:• Explicit process analysis – foreground process systems (precision of analysis)• EIO analysis – background macroeconomic systems (complement the truncated

system boundary)

Mathematical Foundation

34

1

Total environmental impact0

p dp io

u io

A C yE E

C I A

−− = − −

pE

ioE

Environmental extension factor (process systems)

Environmental extension factor (EIO systems)

pA Process matrix

Direct requirementsmatrixioA

uC Upstream cutoff matrix

dC Downstream cutoff matrix

• Unconventional natural gas from shale rocks

• Large-scale production due to hydraulic fracturing and horizontal drilling

• Half of the NG production in the U.S.

• Over 63,000 shale wells in the U.S.

Application to Shale Gas

35U.S. natural gas production

Hydraulic fracturing Horizontal drilling

Hybrid LCA of Shale Gas

36

• Climate change

• Water consumption

• Energy consumption

Goal and scope• UK shale gas• System boundary: well-to-wire• Functional unit: 1 MWh electricity generation from shale gas

Life cycle inventory• 40 basic processes in the process systems• Two-region IO model (UK-ROW) with 224 industrial sectors• Three cases from literature: best, balance, and worst cases

corresponding to the lowest, the medium, and the highest environmental impacts

Impact assessment• GHG emissions (100-year GWP factors;

CO2, CH4, N2O, HFCs, PFCs, and SF6)• Water consumption • Energy consumption

LCA of Shale Gas

37

Process Systems – 40 Basic Processes

38

Process ID Description Process ID Description

m1 Steel production, converter, chromium steel 18/8 m21Soda ash, dense, to generic market for neutralizing agent

m2Concrete production, for civil engineering, with cement CEM I m22 Sodium persulfate production

m3 Tap water production, direct filtration treatment m23 Sodium borates production

m4 Diesel production, low-sulfur m24 Citric acid production

m5 Diesel, burned in building machine m25 Pesticide production, unspecified

m6Diesel, burned in diesel-electric generating set, 18.5kW m26 N, N-dimethylformamide production

m7 Barite production m27 UK electricity generation, with mixed energy inputs

m8 Bentonite quarry operation m28Transport, freight, lorry, all sizes, EURO3 to generic market for transport, freight, lorry, unspecified

m9 Chemical production, inorganic m29 Injection in disposal well

m10 Chemical production, organic m30 Wastewater treatment by CWTm11 Lignite mine operation m31 Onsite treatment with MSFm12 Treatment of inert waste, inert material landfill m32 Onsite treatment with MEDm13 Treatment of drilling waste, landfarming m33 Onsite treatment- with ROm14 Silica sand production m34 Steam production, in chemical industrym15 Petroleum refinery operation m35 Tap water production, direct filtration treatmentm16 Isopropanol production m36 Transporting gas through pipelines

m17 Hydrochloric acid production, from the reaction of hydrogen with chlorine m37 Ethanolamine production

m18 Ethylene glycol production m38 Ethylene glycol productionm19 Potassium chloride production m39 Fugitive emissions of CO2

m20 Carboxymethyl cellulose production, powder m40 Fugitive emissions of CH4

Hybrid LCI Data Structure

39

IO System (896 × 896 matrix)

Agriculture

Mining

Energy

Transportation

Finance

Law

Communication

Real estate

Education

Recreation etc.

Sector groups:

• Multi-region: UK and ROW (rest of world)• Supply-Use Table (SUT): each containing 224 industrial sectors/products

LCA Results

40

• Electricity generation • Transportation

• Electricity generation • Processing

• Drilling • EIO system

Comparison with Existing Hybrid LCA Studies

41

• GHG emissions of shale gas are comparable to those of natural gas • Less GHG emissions than Coal and Oil

Activity – Linking SC Decisions with h-LCO

42

Definition: Activity is a flexible process that involves decision making.

Truck Rail Ship

Operation

Lorry

maintenance, lorry

disposal, lorry

Road

operation, maintenance, road

disposal, road

Operation, freight train

Locomotive

Goods wagon

Maintenance, goods wagon

Maintenance, locomotive

Disposal, locomotive

Railway track

Operation, maintenance, railway track

Disposal, railway track

Operation, transoceanic freight ship

Transoceanic freight ship

Maintenance, transoceanic freight ship

Port facilities

Operation, maintenance, port

?

Agriculture Mining Manufacturing Finance Law Energy

Unit priceUnit price

Unit price

Yue, Pandya, & You (2016). Environmental Science & Technology, 50, 1501–1509.

Hybrid LCO Model for Shale Gas

43

( )1min

opercap

tt T

TCTCdr

LCOETGE∈

++

=∑Economic objective:

Environmental objective: min pro IOTE TEUETGE+

=

s.t. Economic Constraints

Environmental Constraints

Mass Balance Constraints

Capacity Constraints

Composition Constraints

Bounding Constraints

Logic Constraints

IO IOn nssTE e P=

Total GHG emissions :

, ''

ns ns nsns

nNS

s nsP Paio UP∈

− ⋅ ≥∑

Total output of each industrial sector Pns

,nsn m mm

s mM

c price QUP∈

= ⋅ ⋅∑

Upstream input from industry sector ns to process systems

n

sfp

prpca

ocp

p P

PCC

ppr

rcpci

rpcii

∈

= ⋅

⋅∑

Nonlinear term:

Mixed-Integer Nonlinear Fractional Program

mpro pro

mTE e Q=

Case Study of UK Shale Gas Supply Chain

44

• 15 Shale sites (7 existing, 8 potential ones)

• 4 processing plants (2 existing, 2 potential)

• 6 CCGT power plants

• 10-year planning horizon (40 time periods)

MINLP problem: • 414 integer variables• 11,797 continuous variables • 15,370 constraints

Pareto-optimal Curve

45

Drilling Schedules and Production Profiles

46

Drilling Schedules Production Profiles

Supply Chain Design and Flow Information

47

ACS Sustainable Chem. Eng. 2016, 4, pp 3160-3173

48

LCO: Attributional v.s. Consequential

49

Multiobjective Optimization

Goal and Scope Definition

Life Cycle Inventory Analysis

Life Cycle Impact Assessment

Interpretation

Life Cycle Assessment

Automatic generation of system design decisions

• Attributional LCA

• Consequential LCA

Motivating Example

50

Environmental Impacts of producing A

Environmental Impacts of the conversion

Environmental Impacts of end of life of B+ +

(2)Environmental Impacts

of the new system -(1)

Environmental Impacts of the original system

Environmental Impacts of

conversion (2)


conversion (1)-Environmental

Impacts of end of life of B


end of life of C-+

Or

Attributional LCA: static and fact-based

Consequential LCA: dynamic and change-driven

Consequential Life Cycle Optimization

51

Consequential LCA

Techno-economic Analysis

• What upstream and downstream processes are influenced by the target process?

• How does the target process influence the upstream and downstream processes?

Consequential Life Cycle OptimizationMultiobjective Optimization

Process Models

How does it work?

An Analogy – Spot the Difference

52

Before After

Attributional LCA for Process Design Problems

53

Environmental impacts in the

use and end-of-life phases

Environmental impacts in the feedstock

production phase Environmental impacts from the process

Environmental impacts from transportation

• Not suitable for new systems• Overlook the power of markets and influences in other processes

• Applicable to existing systems

System Boundary of the Consequential LCO

54

Partial Equilibrium Model

55

Supply Demand

( )

1

1

1

,

,

1

,

,

,

,

l

l

l

l l,p l,p l,p l,p lp PPC

l,p l,pl,p

l,p l,p

l,p l,p l,p l,p

l,pp PPC

l,p lp PPC

l,p l,p l,p l,p l,p

AS asc XS bsc YS

ns nsasc

ms msbsc ns asc ms

PS l

l,

YS

XS PR

ms YS XS ms YS

p

l, p

l

l

l, p

∈

−

−

∈

∈

−

= ⋅ + ⋅ +

−=

−

= − ⋅

∀

∀

∀

∀=

=

⋅ ≤

∀

≤ ⋅ ∀

∑

∑

∑

( ) ,1l ll l l l l

l

edAD PR PDd leα αβ⋅

= ⋅ + − + ∀⋅

Price elasticity of demandAggregate supply function

Quantities by the target process

,l lAS AD l= ∀

Equilibrium

( )( )

,

,

Supplierl l llcustomerl l l l

LCI AS as0

L

PS l

PC DI D lA ad0

= − −

= − −

∀

∀Life Cycle Inventory

,l las0 ad0 l= ∀

Consequential LCO framework

56

Economic Objectivee.g. maximize net present value

Environmental Objectivee.g. minimizing ReCiPe points

Process ModelInteger variables for technology selection; Mass and energy balance

Market ModelPartial equilibrium models

s.t.

( ),,

max , , ,k l l l k kk l

h P Q X YC∑

( ), , , l k l k kk

Q f X YP l= ∀∑

( ), , , l l l l lAS m Q P YS l= ∀

, l lAS AD l= ∀

( ), , , ,, ,

min , ,l r s l r s l l ll r s

c v Q AS AD ⋅ ∑

( ), , , l l l l lAD n Q P YD l= ∀

Application to Algae-based Biofuel Production

57

Scenedesmus sp. with 27.4 wt % lipid

Renewable dieselFunctional Unit:1 GJ of renewable diesel

Detailed superstructure

586 markets in the U.S.

Fertilizer

Natural Gas

Electricity

Hexane

Hexane

Diesel

Diesel

Fertilizer

Natural Gas

Optimization Results for ReCiPe

59

Production Rate:3.5 MMGal/year

Environmental Impact Breakdown

60

Primary Markets Attributional Consequential

-7,000 -6,000 -5,000 -4,000 -3,000 -2,000 -1,000 0 1,000 2,000 3,000 4,000

Consequential

Attributional

Annual ReCiPe endpoint score (kPt./year)

Urea production DAP production Hexane production Electricity productionDiesel production Fertilizer consumption Fertilizer adjustiment Diesel consumptionDirect emissions Transportation

Diesel Combustion in end of life(1) Displace fossil diesel; (2) Transportation market

(diesel ↑; gasoline ↓)

Fertilizers Increase fertilizer production(1) Increase but not as much;

(2) Crops market (foreign ↑; domestic ↓)

Hexane Positive characterization factors*

Negative characterization factors*

*Data for “rest of the world” from Ecoinvent 3.3

Consequential Environmental Profile

61

ACS Sustainable Chem. Eng. 2017, 5, pp 5887-5911

62

• Life cycle analysis and life cycle optimization• Process-level LCA and life cycle design/optimization

• Systems boundary• Functional unit

• Integrated hybrid LCA and LCO • Process systems to supply chain, and to macroeconomics scales

• Consequential LCA and LCO• Dynamic and change-driven• Suitable for new product systems to account for influences of other

processes through the market

• Applications to energy systems• Algal biorefinery• Shale gas • ……

Conclusion

63

64

http://you.cbe.cornell.edu

integrated hybrid life cycle optimization for multi-scale

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