Docstoc

Ethanol from Biomass - Potential Availability and Benefits

Document Sample
Ethanol from Biomass -  Potential Availability and Benefits Powered By Docstoc
					     Ethanol from Biomass:
Potential Availability and Benefits
            Gary A. Herwick
        Director Environment & Energy

          Candace S. Wheeler
           Staff Research Scientist
                  Introduction
   Fossil fuel consumption
    •   The US transportation sector relies on petroleum for
        95% of its energy and consumes approximately 140
        billion gallons of gasoline each year
    •   Light duty vehicles account for 77% of the
        transportation energy used
   Green house gas emissions
    •   The US accounts for 22% of the world’s CO2 emissions
    •   Transportation represents the largest primary source of
        carbon accounting for 32% of all US emissions
    •   Carbon emissions are projected to rise from 500 mmtc
        (million metric tons carbon equivalent) to 1000 mmtc
        by 2050
         Ethanol – Advantages
   Renewable
   Reduces petroleum fuel use
   Reduces CO2 emissions (potentially CO2 neutral)
   Stimulates domestic economic development
    •   Increase domestic jobs
    •   Increase revenue particularly in rural areas
   Can be used in today’s vehicles
    •   All cars since 1979 are E10 compatible
    •   3,000,000 E85 flex-fuel vehicles currently in use
        Ethanol – Disadvantages

   Not currently cost competitive versus gasoline
    •   Production costs will likely decline within 10 years
    •   Biotech breakthroughs are anticipated
   Limited capacity
   Lower energy density
    •   1 gal of ethanol has the energy equivalency of 2/3
        gal of gasoline
                   Current State

   Ethanol has been used in the
    US since 1908 (Model T)
   Total US ethanol production is
    projected to be 4.0-4.5 B gal in
    2005 primarily from corn
   GM acknowledges and
    supports this continued growth
   However, corn derived ethanol
    will not be enough to replace
    the 140B gal of gasoline used
    each year
                                  2002 US Ethanol Production
                                    Capacity and Forecast
                               5000
                               4500
Millions of Gallons per Year




                                                                                                  New Plants
                               4000
                                                                                                  Planned
                               3500
                               3000                                                               New Plants
                               2500
                                                                                                  Under
                                                                                                  Construction
                               2000                                                               Existing Plant
                               1500                                                               Expansions
                               1000
                                                                                                  Existing Plants
                                500
                                  0
                                        2001        2002          2003          2004     2005


                                                                         2001     2002   2003   2004    2005
                                  Existing Plants                        2219     2594   2594   2594    2594
                                  Existing Plant Expansions                         66    257    352     430
                                  New Plants Under Construction                    205    442    442     456
                                  New Plants Planned                             -        881   1036    1081
                                  Total                                  2219     2865   4174   4424    4561
Maximum Production from Corn
   The US produced 9.01 B bushels of corn last
    year down from 9.5 B bushels in 2001
   Each bushel of corn produces 2.6 - 2.8 gal of
    ethanol
   Therefore, 23.4 B gal of ethanol could be
    produced if we used 100% of the corn produced
   This falls far short of the 140 B gal of gasoline
    currently used by the transportation sector but
    would be enough to make all fuel used E15
   To replace all 140 B gal with E85 would require
    120 B gal of ethanol, 50 B bushels of corn, and
    300 M acres of land
What about Ethanol from Biomass

     Production Differences
     Potential Availability
     Potential Benefits
            Ethanol Production
   Currently produced from starches
    and sugars
    •   Corn in the US and sugarcane in
        Brazil
    •   Uses simple enzymes to break down
        starches to simple sugars which are
        then fermented into ethanol
    •   Mature industry - cost not likely to
        decrease substantially
   In the future, also produced from
    biomass (stover, straw)
    •   Uses agriculture wastes and
        dedicated energy crops as
        feedstocks
    •   Requires special enzymes to break
        down the cellulose into sugars
Ethanol Production: Corn vs. Biomass
                                                     Product
  Pretreatment             Fermentation
                                                     Recovery
  Corn:            Amylase                  Yeast
    Starches                 Glucose                Ethanol
    Sugars

                             Hexose (C6)
                              Glucose
Biomass:       Cellulase      Galactose
 Cellulose                    Mannose
                                                Bacteria Ethanol
 Hemicellulose
 Lignin                      Pentose (C5)
                              Xylose
     trichoderma reesei       Aarabinose
Possible Feedstock Sources
   Agricultural residues
    •   Stover, straws, bagasse, alfalfa
   Forestry waste
    •   Mill residue, bark, wood chips, thinnings
   Dedicated energy crops
    •   Switch grass, willows, poplars, sorghum, eucalyptus
   Municipal solid waste
    •   Yard wastes, paper, packaging, organic wastes
   Sewage
    •   Livestock wastes, municipal sewage sludge
 Basic Composition of Biomass
            Other
   Lignin
             5%
    20%

                          Cellulose
                            45%          (glucose polymer)


 Hemi-
cellulose   (xylose/arabinose polymer)

  30%
        Feedstock Composition
Feedstock    Cellulose Hemi-     Lignin Other
                       cellulose
Agricultural 38        32        17     13
Waste
Forestry     50        23        22     5
Waste
Municipal    45        9         10     36
Waste
Herbaceous 45          30        15     10
Energy Crop
             Cellulosic Ethanol
         Production Improvements
•Low feedstock prices
                          •Enzymes improvements
Plant Fiber     Enzymes
                                •Decreased production time
Pretreatment    Enzymatic    Waste         Ethanol
                                                      Distillation
(dilute acid)   Hydrolysis Separation    Fermentation

•Increase hydrolysis yield
                             Lignin                    Bioethanol
 •Decrease enzyme loading                   Biotech Firms
                           Electricity      •Genencor
                           Generation       •Novozymes
                   Issues
   Availability
    • Is there enough land to grow sufficient
      quantities of biomass?
    • How much biomass is potentially
      available?
   Sustainability
    • Is the harvesting of large quantities of
      biomass sustainable?
    • How does using ethanol produced from
      biomass impact the environment from a
      total life cycle perspective?
        Biomass Availability

   Includes these sources of biomass
    • Agricultural residues
    • Dedicated energy crops
    • Municipal solid waste (MSW)
    • Forestry and mill wastes
        Agricultural Residues
   Net collectible residues range from 327 -
    407 M MT and represent 67-70% of total
    residues generated
    • Corn stover 31-45%
    • Wheat straw 18-28%
    • Soybean residue 19-23%
    • Barley 3-8%

   Assuming a conservative yield of about 60
    gal/MT, this generates 20 to 25 B gal/year
   An optimistic yield of 110 gal/MT would
    generate 36 - 45 B gal/year
             Energy Crops
   Our best estimate of possible
    biomass yield based on growing
    switch grass after considering
    climate and soil conditions and strict
    economic and agricultural
    constraints is 555 M MT/year
   This would produce between a
    conservative 33 B gal/year and an
    optimistic 61 B gal/year
                     MSW

   US generates 210 - 371 M MT/yr of which 147
    - 227 M MT is land filled
   Approximately 66% of all MSW could be used
    to produce ethanol
   Therefore, 115 – 158 M MT is convertible to
    ethanol
   This would generate 5.8 – 10.4 B gal/year
    (optimistic yield equals 15.2 gal/year)
      Forestry and Mill Wastes

   Represents a relatively small
    contribution
   Total available forestry and mill waste
    equal approximately 13.0 M MT
   This represents 450 - 980 M gal/year
Maximum Ethanol from Biomass

Biomass Source         Ethanol Produced

Agricultural Residues 20 - 25 B gal (conserv.)
                      36 - 45 B gal (optim.)
Energy Crops          33 - 61 B gal
MSW                    5 - 10 B gal
Forestry/Mill Waste    0.5 - 1.0 B gal
Total (average)        66.5 – 107 B gal
NREL Projections of Future
   Ethanol Production
30

25

20

15

10

5

0
     2003   2007   2012   2020   2020?
             WTW GHG Emissions

              WTW GHG Emissions
Pathway           GHG Emission, g/mile

                      WTT        TTW      WTW
Gasoline              121         431     552

E85 (from corn)        28         424     452

E85 (from             -271        424     153
cellulose)
GHG emissions include CO2, CH4, and N2O
   G
       as
          o




                                                                      Better
              lin
                                                                                              g CO2/mile

                  e
      Di         c
                                                                                           (fuel production

          es on
             el         ve
    Di                      n




                                          0
                                              100
                                                    200
                                                          300
                                                                400
                                                                       500
                                                                               600
                                                                                     700
                                                                                             and vehicle) 800


        es con tio
G                                 n
  as el h ven al
      ol
         in
                 yb           t
 Na         e         rid ion
     ph fue                el al
         th        l c ect
 Fi         a           el         r
   sc         fu          l h ic
       he el                  y
           r T ce brid
                ro ll h
                                                                                                Petroleum




          CN psc ybr
              G          h          id
                            Di
        LH co
M           2         nv ese
  et
     ha fue ent l
        no          l           io
            l f cell nal
                u            hy
       CH el                     br
E-          2         ce
  85           fu        ll          id
       (8         e         hy
          5% l ce bri
 Et
     ha         et l l h d
        no han ybr
                                                                                                Natural Gas




   El l fu               ol          id
      ec          e         )c
          tro l ce on
              ly         l           v.
                 si l hy
                    s
                       hy brid
                           dr
                              og
                                   en
                                                                                                Electricity
                                                                                                Renewable/
                                                                                                                Well-to-Wheel Greenhouse Gases
Emissions Associated with FFV’s
   Assuming that the ~3 million FFV’s are driven
    an average of 11,142 miles/year

        Current FFVs WTW GHG emissions
                                      CO2 Equivalents
                           Gasoline E85 (Corn) E85 (Cellulose)
WTW GHG Emissions              18.5         15.1           3.3
(Mtons/yr)
Emissions Reduction               -          3.3          13.3
from Gasoline (Mtons/yr)
Emissions Reduction               -         18.1          72.3
from Gasoline (%)
                     Summary
   Ethanol produced from corn will increase but
    eventually reach a maximum due to economic
    constraints (~5 to 10 B gals)
   Ethanol produced from biomass could reach 66
    to 107 B gals annually based on current yields
   While short of the 140 B gal used today, it would
    • Be sufficient to support E60 to E70
    • Displace approximately half of the petroleum used
    • Significantly impact energy security issues
    • Significantly reduce CO2 emissions
                Conclusions
   General Motors supports the continued
    production and promotes the use of ethanol
    as an automotive fuel
   Increased production of ethanol from corn is
    a low risk/viable short term solution
   Ultimately, producing ethanol from biomass
    will be more cost effective and necessary to
    achieve significant volume
   Ethanol is an effective strategy for
    displacing petroleum and for reducing
    carbon emissions

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:73
posted:4/27/2008
language:English
pages:29