Life Cycle Assessment of Cellulosic Ethanol

Julie  Sinistore  Research  Experience  for  Teachers  

June  30th,  2010  

Outline !   What  is  Life  Cycle  Assessment  (LCA)?  

!   How  do  you  do  an  LCA?  !   Case  study  in  the  applicaGon  of  LCA  

  Corn  grain  and  cellulosic  ethanol  !   Direct  vs.  Indirect  Land  Use  Change  !   Fossil  vs.  bioGc  carbon  emissions  

What is LCA? !   Life  Cycle  Assessment  (LCA)  is  the  invesGgaGon  and  valuaGon  of  the  environmental  impacts  of  a  product  or  service.  It  is  sGll  a  method  in  progress:  

!   “There  is  no  single  method  for  conducGng  LCA  studies.  OrganizaGons  should  have  flexibility  to  implement  LCA  pracGcally  as  established  in  this  InternaGonal  Standard,  based  upon  the  specific  applicaGon  and  the  requirements  of  the  user.”            (ISO  14040:1997)   iso.org

What can you do an LCA on? Goods, services, anything!!

LCA Pieces: Boxes, lines, quantities

Inputs

Primary output

Secondary output

Good or Service Functional unit &

Measurement quantity

Assumptions Data

Allocated inputs

Allocated outputs

Conversion rates/Process

+ Result Metric

Comparison Sensitivity Analysis

Step 1. Pick the good or service and its functional unit

!   Say  you  wanted  to  do  an  LCA  on  bo[led  water    Do  you  want  an  LCA  on  one  bo[le  of  water  or  all  the  bo[led  water  sold  in  a  store  or  all  the  bo[led  water  Pepsi  made  or  sold  last  year?  

!   Examples  of  reference  quanGGes:    One  unit  –  a  bo[le  of  water,  a  gallon  of  milk,  a  bushel  of  corn,  a  liter  of  fuel,  a  plane,  a  car  

  One  Gme  step  –  yearly  producGon  at  a  factory,  daily  irrigaGon  water  use  

  One  funcGonal  unit  (service)  –  one  plane  trip,  one  screening  of  a  movie  

  Mix  and  match  –  gallons  of  ethanol  per  year  

Step 2: Define your measurement quantities

!   What  do  you  want  to  measure  in  the  life-­‐cycle  of  this  thing?    Energy    Greenhouse  gas    Water  

  Air  polluGon    Water  polluGon  

  Money    Social  implicaGons  

!   Divide  your  measurement  quanGty  by  your  reference  quanGty  and  you  have  a  metric!    Energy  per  plane  flight    Water  use  per  gallon  of  milk  

  GHG  emissions  per  bo[le  of  water  

Step 3: Define the beginning and the end (boundary)

 How far “upstream” and “downstream” do you want to go?  Sweet corn production LCA up to the farm gate, the store or your dinner table?  Ethanol production up to the refinery, the gas station or burning in your car?

Step 4: Think of every input/output of production

Inputs   Outputs  

Plastic

Paper

Water

Ink

Energy

Transportation

Bottles of water

GHGs

Other?

Other?

Process and Conversion rates (not just what but how)

!   You  need  to  understand  the  manufacturing  process  of  a  product  or  the  administraGon  of  a  service    This  may  uncover  hidden  inputs  and  outputs  

  Product:  What  kind  of  plasGc  is  used  to  make  the  bo[le  and  what  is  the  process  for  making  the  mold?  

  Service:  What  is  required  to  operate  a  passenger  train    (e.g.  personnel,  wear  and  tear  on  equipment)?  

!   What  are  the  conversion  rates  and  losses?    How  much  plasGc  does  it  take  to  make  1  bo[le  (and  how  much  is  lost  as  waste)?  

Step 5: Data compilation !   Decide  what  data  do  you  need  

  Electrical  grid  mix  a  state  or  region  –  Wisconsin  or  the  US    Conversion  efficiencies  –  liters  ethanol  per  kg  corn    Process  energy  –  MJ  from  natural  gas  for  process  heat    TransportaGon  –  distance  from  refinery  to  farm,  truck  or  train,  number  of  trips,  fuel  efficiency  of  a  full  and  empty  truck  

!   Be  consistent  about  sources    Literature  –  different  papers  use  very  different  numbers    Databases  –  some  are  free,  some  are  not    Experimental/observaGonal  data  –  self-­‐generated  data    GeospaGal  data  –  helps  with  landscape  factors  and  transportaGon  assumpGons  

  Industry  standards  –  check  ISO  documents  for  data  standards,  industry  standard  values  are  a  good  starGng  point  

Step 6: Allocation !   All  inputs/outputs  are  not  created  equal.  

Primary output

Good or Service

Allocated inputs

Allocated outputs

Inputs

Most are straightforward, but some are more “slanted,” so you need to figure out their “right-left” component.

counts doesn’t count

a

counts = total·cosa

a

Warning! Math metaphor!

unitless ratio

Allocation: How? !   How  do  we  allocate  some  of  the  energy  and  GHGs  associated  with  making  parts  of  a  product  in  an  LCA?    Economic/Market  allocaGon:  Energy  required  or  GHGs  emi[ed  to  replace  an  economically  equivalent  amount  of  the  product  on  the  market  (could  be  an  economic  subsGtute).  

  Mass  allocaGon*:  Make  a  raGo  of  the  mass  of  the  input  you  used  to  make  the  product  and  the  total  mass  and  mulGply  that  by  the  total  energy  or  GHGs  from  the  input  producGon.  

  Energy  allocaGon:  Same  as  with  mass,  but  with  energy.  

*This is tough if the product has no mass like electricity.

Allocation

  You  can  also  allocate  energy  and  GHGs  for  co-­‐products  by  all  the  same  methods  plus:  •  System  expansion:  Expand  the  analysis  boundary  to  include  the  upstream  and  downstream  costs  of  the  products  that  co-­‐products  displace.  

•  Eg.  PlasGc  is  a  valuable  co-­‐product  of  oil  refining,  so  you  could  apply  an  energy  or  GHG  credit  to  oil  refining  which  is  proporGonal  to  the  energy  and  GHG  value  of  plasGc  by  the  Economic,  Mass,  Energy  or  System  Expansion  systems.  

Step 7: Comparison   LCAs  are  only  valuable  if  you  have  something  to  compare  your  numbers  to.  

  Let’s  say  the  net  energy  used  to  make  a  16oz  water  bo[le  is  12Joules  and  5gCO2eq  are  emi[ed.*  •  Is  that  high  or  low?  

 What  do  you  compare  it  to?  •  Other  bo[led  water  brands  •  Tap  water  •  Other  “economic  subsGtutes”  

*completely fictitious

Step 8: Sensitivity analysis !   IdenGfy  variables  and  assumpGons  which  could  dramaGcally  affect  your  analysis.  

!   Test  the  sensiGvity  of  your  results  to  those  assumpGons.    Eg.  If  you  had  a  co-­‐product  credit  of  5MJ  per  liter  of  ethanol,  try  10,  9,  8,  7,  6,  4,  3,  2,  1  and  0  and  see  how  that  changes  your  results.  

  Eg.  If  you  did  a  market-­‐value  co-­‐product  credit,  try  a  mass  or  energy  balance  credit.  

!   You  may  adjust  or  throw  out  some  assumpGons  based  on  sensiGvity  analysis.  

Result Metric

Comparison Sensitivity Analysis

Rules of LCA 1.  Know  your  system.  

2.  Know  your  data  and  data  sources.  

3.  If  you  must  allocate,  allocate  fairly  and  always  remember  why  you  are  allocaGng.  

4.  Be  consistent  with  data  and  allocaGon.  

5.  Clearly  state  all  assumpGons  and  the  reasons  for  the  assumpGons.  

6.  QuesGon  everything.*  * This is a good rule for life too.

Case Study: Ethanol !   FuncGonal  Unit  

  Liter  of  fuel  or  all  the  liters  produced  in  a  year  at  a  refinery  !   Measurement  quanGty  

  Energy  (MJ)    GHG  (gCO2eq)  

!   Metrics    Energy  or  GHG  per  liter  or  year    Net  Energy  RaGo  (output  energy/input  energy)    GHG  Intensity  (gCO2eq/MJ  output)  

!   Boundaries    Farm  or  field  to  fuel  (as  it  leaves  the  refinery)  

!   AllocaGon    Eg:  co-­‐products  and  farm  machinery  

!   Comparison    Gasoline    92  gCO2eq/MJ*  and  LHV  32MJ/L  

* CA Low Carbon Fuel Standard value for gasoline

How is corn ethanol made?

Corn Ethanol Feedstock production  Corn grain

 Inputs: NPK, lime, natural gas, pesticides, diesel, gasoline, tillage practices, equipment

Liquefaction   Heating & enzymatic hydrolysis

 Inputs: Natural gas, electricity, enzymes Fermentation  Yeast

 Inputs: Natural gas, electricity, yeast, nutrients Fuel processing  Distillation, dehydration, denaturation  Inputs: Natural gas, electricity, gasoline

Products  Ethanol, animal feed (WDG)  Allocation of energy and GHG values for ethanol and co-products

To market  Transportation

CO2

Remember: if you burn a fossil fuel you get GHGs.

Drying WDG to get DDG requires natural gas

Cellulosic Ethanol Feedstock production  Corn stover, switchgrass, wood

 Inputs: NPK, lime, natural gas, pesticides, diesel, gasoline, tillage practices, equipment

Pretreatment  Dilute Acid, AFEX, SPORL

 Inputs: Natural gas, electricity, chemicals

Saccharification  Enzymatic hydrolysis

 Inputs: Natural gas, electricity, enzymes

Fermentation  Yeast or bacteria

 Inputs: Natural gas, electricity, microbes, nutrients Fuel processing  Distillation, dehydration, denaturation  Inputs: Natural gas, electricity, gasoline

Products  Ethanol, animal feed, electricity, heat, lignin-derivatives

 Allocation of energy and GHG values for all products

Burn lignin for process heat or electricity

To market  Transportation

Ethanol production differences for various feedstocks

Produc1on  step   Corn  grain   Corn  stover   Switchgrass  

Biomass  produc1on  

FerGlizer  input   high   allocaGon   low  

Soil  Gllage   medium  to  high   allocaGon   low  

Equipment  legacy   mature   developing   developing  

Pretreatment   not  necessary   necessary   necessary  

Enzymes   cheap   expensive   expensive  

Co-­‐products   animal  feed   electricity   animal  feed  &  electricity  

You tally the inputs and outputs Net  GHG  emission   Net  Energy  Use  

Inputs   Does  this  input  add  to  GHG  emissions  or  use  energy?  

Natural  Gas  (NG)  

Petroleum  fuels  (transportaGon/Gllage)  

Soil  Gllage  

NPK  and  Lime  

Electricity  

Land  use  change  

Outputs   Does  this  output  abate  GHG  emissions  or  provide  energy?  

Ethanol  

Co-­‐products  (feed,  electricity)  

Yes Yes

Yes Yes

Yes Yes Yes

Yes

Yes

Yes

Yes

No

No

Yes**

*Yes for coal or NG power, no for nuclear or renewable solar or wind energy **Carbon released from burning the ethanol was sequestered from the air by the plant

Yes Yes and No*

Direct vs. Indirect Land Use Change from Biofuels !   Direct  Land  Use  Change  (DLUC):  A  farmer  decides  to  grow  an  energy  crop  where  no  other  crop  was  grown  or  a  non-­‐energy  crop  was  grown.  

!   Indirect  Land  Use  Change  (ILUC):  A  naGon  or  region  grows  less  of  a  food-­‐crop  or  diverts  a  food  crop  to  bioenergy  uses.  Demand  for  that  food  crop  does  not  decrease,  so  producGon  shiss  elsewhere  (another  state  or  country).  

Direct LUC example

!   A  farmer  decides  to  take  land  a  current  land  use  e.g.  ConservaGon  Reserve  Program  (CRP)  land,  forest,  food-­‐crop  land  or  fallow  land  and  grow  a  bioenergy  crop  on  that  land.  

Indirect LUC example !   A  U.S.  farmer  takes  a  replaces  a  food-­‐crop  (e.g.  soybeans)  with  a  bioenergy  crop  (e.g.  switchgrass).  

!   Demand  for  soybeans  remains  the  same  or  increases.  

!   Land  in  another  country  (e.g.  Brazil)  is  taken  out  of  forest,  pasture  or  other  producGon  to  produce  soybeans  to  make  up  for  this  lost  supply  in  the  U.S.  

Why does ILUC matter?

!   An  indirect  change  in  land  use  could  cause  more  GHGs  to  be  emi[ed  than  if  the  bioenergy  crop  did  not  cause  ILUC.  

!   What  if  producing  soybeans  in  Brazil  emits  more  GHGs  than  producing  soybeans  in  the  U.S.?  

Important differences between energy and GHG LCA

!   There  are  processes/inputs  which  produce  GHGs  that  do  not  use  energy    Soil  Gllage  pracGces    N  applicaGon,  runoff  and  leaching  

!   There  are  processes/inputs  which  use  energy  and  don’t  produce  GHGs    Nuclear,  wind  and  solar  electricity  

Caution: What counts in the GHG LCA? Follow the carbon!

Trapped Carbon

Ethanol

Gasoline

CO2

CO2

CO2 CO2

CO2 CO2

CO2

CO2

CO2

CO2 > CO2

Questions? Visit www.glbrc.org for more information on the

GLBRC’s scientific publications and education and outreach programs.

Or, email me: sinistore@wisc.edu