My Points I
• Ethanol is and will be an important contributor to
reducing our “petroleum addiction”
• Focus needs to be on finding replacements for
crude oil for liquid fuels—we need real solutions
• Ethanol is one of a very few solutions available—
gives high “return on petroleum invested” (about
2200% or 22 fold)
• “Net energy” is a fundamentally wrong concept &
even dangerous as a policy guide
My Points II
– Corn ethanol is a good start for large scale
ethanol and has generally positive features
•
•
•
•
•
Bridge to cellulosic ethanol
Improves rural economy
Reduces net farm subsidies
Can reduce greenhouse gases
Greatly reduces dependence on petroleum for liquid
transportation fuels
– Cellulose ethanol will have a much bigger
positive impact than corn ethanol on these &
other areas
Most Recent Pimentel & Patzek Study*Some Serious Deficiencies and Errors
• Define ethanol’s % net energy as:
– [(Ethanol Heating Value (LHV) – Fossil Energy Inputs) /Ethanol
Heating Value (LHV)] x 100
• All BTU are treated as equivalent (1 BTU coal = 1 BTU
petroleum = 1 BTU natural gas = 1 BTU electricity = and so
on)
• Confound “fossil fuels” with “liquid fossil fuels”=petroleum
• They calculate net energy for ethanol from:
– Corn
– Switchgrass
– Wood
- 29%
- 50%
- 57%
• They make no comparisons with other liquid fuels
• *Natural Resources Research, vol. 14, No. 1, March 2005
pgs. 65-76
Net Energy Reductio Ad Absurdum:
the Accounting Analogy
• “Net energy” is an energy accounting tool: a
terrible one
• Using the net energy approach of “All BTU are
equal” BP’s accountants would calculate:
– 100 U.S. $ + 100 Pounds Sterling + 100 French
francs + 100 Deutschmarks = $400 U. S.
– The math is right; the idea is absurd!
• We cannot add up different forms of energy on a
straight BTU basis any more than we can add up
different currencies on a straight numerical
equivalency basis
• Different forms of energy have different qualities—
just like different currencies do
Are All Btu Created Equal:
What Does “the Market” Say?
Energy
Carrier
Energy
Content*
(Btu/X)
Coal
20.4 MM
Btu/short ton
Natural Gas 1,030 Btu/
Petroleum
Electricity
* EIA 2004 pg. 357386
cubic foot
5.8 MM
Btu/barrel
3413 Btu/
Kwhr
Typical Market Market Value
Value
($/MM Btu)
($/X)
$40.30/short
$2.00
ton
$7.30 per 1000
cubic foot
$55 per barrel
$7.10
$0.082/Kwhr
$24.00
$9.50
Pimentel & Patzek Confound Fossil Fuels &
Petroleum Used for Ethanol Production I
Five major
Inputs in
P&P 2005*
Total Fossil Petroleum Total
Energy
Fraction of Petroleum
(kcal x 1000)
Total Fossil (kcal x 1000)
Machinery
1,018/ha
~50%
500/ha
Diesel
1,003/ha
~100%
1,003/ha
Nitrogen
(Fertilizer)
2,448/ha
~0%
0
Steam
2,546/1000 l
~0%
0
Electricity
1,011/1000 l
~0%
0
Total*
6,597/1000 l
2,123/1000 l
*Out of 21 different inputs. Adapted from Tables 1 & 2 of
Pimentel & Patzek, NRR, 2005.
Pimentel & Patzek Confound Fossil Fuels
& Petroleum Used II
• From previous slide, per P&P:
– Total energy equals 6,597 kcal/liter ethanol
– Total petroleum used equals 2,123 kcal/liter ethanol
• “Net energy” calculation for corn ethanol
– [(Ethanol Heating Value (LHV) – Fossil Energy Inputs)
/Ethanol Heating Value (LHV)] x 100
– Thus [(5,130 - 6,597)/5,130] x 100% = -29%
• Minimum “Net petroleum”
– Thus [(5,130 - 2,123)/5,130] x 100% = +60%
• I prefer “Petroleum Profit Ratio” = Kcal liquid fuel out
per kcal of petroleum invested to make that fuel
• Ratio for petroleum invested to make ethanol vs.
petroleum invested to make gasoline is +2200%.
What Do Others Conclude about
Pimentel and Patzek Studies? I*
• “Studies** that reported negative net energy
incorrectly ignored coproducts and used some
obsolete data.
• All studies (two by P&P and four others) indicated
that current corn ethanol technologies are much
less petroleum-intensive than gasoline...”
• Fig. 2. Ethanol yields (1.1/0.05) = 22x more liquid
fuel than gasoline per unit of petroleum “invested”
• *Farrell, et al, “Ethanol can Contribute to Energy and Environmental
Goals” Science vol. 311. Jan. 2006 pg. 506-508
• **Refers to T. Patzek. Crit. Rev. Plant. Sci. 23, 219 (2004) & D. Pimentel
and T. Patzek. Nat. Resource Res. 14, 65 (2005)
What Do Others Conclude about
Pimentel and Patzek Studies? II*
• “The large energy inputs reported by Pimentel & Patzek
are [due to] a collection of conservative assumptions…”
• “All studies (P&P + 3 others) indicated that current corn
ethanol technologies are much less petroleum-intensive
than gasoline..”
• For cellulosic ethanol, P&P results are an order of
magnitude higher than the other 3 studies because P&P
“assume that industrial process energy is generated by
fossil fuel combustion and electricity rather than by lignin
combustion”.
• *R. Hammerschlag. Environ. Sci. & Technol. “Ethanol’s Energy Return
on Investment: A Survey of Literature 1990-Present” in press 2006.
Why should we bury “net energy”? I
•
•
•
•
Because it is a convenient fiction, an academic toy
Net energy doesn’t relate to the real world
It doesn’t serve good energy policy formation
Why?
• Because it treats all energy from all sources
(coal, oil, natural gas, solar, wind, hydro, etc) as
equal
• Confounds “fossil fuels” with petroleum used
• Ignores energy quality, only deals with energy
quantity
• But all energy is NOT created equal
Why should we bury “net energy”? II
•
•
•
Professors Pimentel & Patzek have further
separated net energy from reality: why?:
Because they don’t compare ethanol with
real fuels
We have. According to their flawed “net
energy” standard:
– Ethanol is significantly better than gasoline,
diesel, jet fuel ( ethanol is -29% vs. gasoline 37%)
– Ethanol is enormously better than electricity
(-235%)
Making Some Comparisons
• I disagree with the fundamental premise of “net
energy” analysis: “All BTU (kcal, erg) are created
equal” They are not.
• But let’s apply the “net energy” approach to other
energy systems, for example:
• Burn 3 kcal of coal or natural gas to get 1 kcal
electricity
– “Net energy” is negative 235%
– But electricity is higher quality energy than coal
• Refine 100 kcal of crude oil to produce 83.5 kcal
of gasoline, diesel, jet fuel, residual oil, etc.
– “Net energy” is negative 37%
– But gasoline is higher quality energy than
crude oil
Petroleum Refining
Refining input
9.6 BTU
Fuel out 83.5 BTU
Gasoline, diesel,
jet fuel, LPG, residual
oil, etc
Other
non fuel products
Crude oil
100 BTU
Production &
Distribution Input
4.5 BTU
83.5 BTU – 114.1 BTU
NET ENERGY =
= - 37 % (vs.-29%)
83.5 BTU
Electricity Generation From Coal
Mining input
1 BTU
Coal
Electricity
100 BTU
31 BTU
Generation &
Distribution Input
3 BTU
31 BTU – 104 BTU
NET ENERGY =
= - 235 % (vs. -29%)
31 BTU
Fossil Energy Replacement Ratio:
the Primary Climate Security Driver
Fossil Energy Ratio (FER) =
6
Energy Delivered to Customer
Fossil Energy Used
5.3
5
4
3
2
1.4
0.8
1
0
0.4
Cellulosic
Ethanol
Biorefinery
Corn Ethanol
Gasoline
Electricity
Source: J. Sheehan & M. Wang (2003)
Petroleum Replacement Ratio:
the Primary Energy Security Driver
Petroleum Replacement Ratio (PRR) =
Liquid Fuels Delivered to User
Petroleum Energy Used
25
20
20
15
12.5
10
5
0
0.91
Cellulosic
Ethanol
Biorefinery
Corn Ethanol
Gasoline
Adapted from Farrell, et al (2006)
A Question Follows:
• Are we really going to stop burning coal for
electricity or refining crude because their
“net energy” is negative?
• Heck no! – so let’s not apply that reasoning
to ethanol
• Unfortunately, that is exactly where the net
energy analysis (mis)leads us
• It’s time to get real about energy…and the
“net energy” idea is simply unreal
Logical Consequences
• If “negative net energy” means anything,
then:
– Shut down all coal (& natural gas) electricity
generation (70% of total)
– Shut down all oil refineries—98% of vehicles
• “Net energy” is a foolish argument
• All energy production systems sacrifice
some quantity of energy for increased
energy quality
Summary
• Professors Pimentel & Patzek are not dealing with
the real world of our energy needs
• Net energy” is fundamentally wrong & dangerous
as a policy guide
• Focus needs to be on:
– finding replacements for crude oil
– system designs that work
• “Net energy” argument misleads us and misdirects
our focus: extending & then replacing petroleum
• Corn ethanol is and will be an important contributor
to ending our dependence on petroleum
• Cellulosic ethanol will do even more to replace
petroleum with renewable fuels