NREL is a national laboratory of the U.S. Department of Energy
Office of Energy Efficiency & Renewable Energy
Operated by the Alliance for Sustainable Energy, LLC.
This report is available at no cost from the National Renewable Energy
Laboratory (NREL) at www.nrel.gov/publications.
Contract No. DE-AC36-08GO28308
Process Design and Economics
for the Conversion of
Lignocellulosic Biomass to
Hydrocarbons:
Dilute
-Acid and Enzymatic
Deconstruction of Biomass to Sugars
and Biological Conversion of
Sugars to
Hydrocarbons
R. Davis, L. Tao, E.C.D. Tan, M.J. Biddy,
G.T. Beckham, and C. Scarlata
National Renewable Energy Laboratory
J. Jacobson
and K. Cafferty
Idaho National Laboratory
J. Ross, J. Lukas, D. Knorr,
and P. Schoen
Harris Group Inc.
Technical Report
NREL/TP-5100-60223
October 2013
NREL is a national laboratory of the U.S. Department of Energy
Office of Energy Efficiency & Renewable Energy
Operated by the Alliance for Sustainable Energy, LLC.
This report is available at no cost from the National Renewable Energy
Laboratory (NREL) at www.nrel.gov/publications.
Contract No. DE-AC36-08GO28308
National Renewable Energy Laboratory
15013 Denver West Parkway
Golden, CO 80401
303-275-3000 • www.nrel.gov
Process Design and
Economics for the Conversion
of Lignocellulosic Biomass to
Hydrocarbons:
Dilute-Acid and Enzymatic
Deconstruction of Biomass to Sugars
and Biological Conversion of Sugars
to Hydrocarbons
R. Davis, L. Tao, E.C.D. Tan, M.J. Biddy,
G.T. Beckham, and C. Scarlata
National Renewable Energy Laboratory
J. Jacobson and K. Cafferty
Idaho National Laboratory
J. Ross, J. Lukas, D. Knorr, and P. Schoen
Harris Group Inc.
Prepared under Task No. BB07.2410
Technical Report
NREL/TP-5100-60223
October 2013
NOTICE
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Cover Photos: (left to right) photo by Pat Corkery, NREL 16416, photo from SunEdison, NREL 17423, photo by Pat Corkery, NREL
16560, photo by Dennis Schroeder, NREL 17613, photo by Dean Armstrong, NREL 17436, photo by Pat Corkery, NREL 17721.
Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.
i
This report is available at no cost from the
National Renewable Energy Laboratory (NREL)
at www.nrel.gov/publications.
Executive Summary
The U.S. Department of Energy (DOE) promotes the production of a range of liquid fuels and
fuel blendstocks from lignocellulosic biomass feedstocks by funding fundamental and applied
research that advances the state of technology in biomass collection, conversion, and
sustainability. As part of its involvement in this program, the National Renewable Energy
Laboratory (NREL) investigates the conceptual production economics of these fuels.
Between 1999 and 2012, NREL conducted a campaign to quantify the economic implications
associated with measured conversion performance for the biochemical production of cellulosic
ethanol, with a formal program between 2007–2012 to set cost goals and to benchmark annual
performance toward achieving these goals, namely the pilot-scale demonstration by 2012 of
biochemical ethanol production at a price competitive with petroleum gasoline based on modeled
assumptions for an “n
th
” plant biorefinery. This goal was successfully achieved through NREL’s
2012 pilot plant demonstration runs, representing the culmination of NREL research focused
specifically on cellulosic ethanol, and a benchmark for industry to leverage as it commercializes
the technology. This important milestone also represented a transition toward a new Program
focus on infrastructure-compatible hydrocarbon biofuel pathways, and the establishment of new
research directions and cost goals across a number of potential conversion technologies.
This report describes in detail one potential conversion process to hydrocarbon products by way
of biological conversion of lignocellulosic-derived sugars. The pathway model leverages
expertise established over time in core conversion and process integration research at NREL,
while adding in new technology areas primarily for hydrocarbon production and associated
processing logistics. The overarching process design converts biomass to a hydrocarbon
intermediate, represented here as a free fatty acid, using dilute-acid pretreatment, enzymatic
saccharification, and bioconversion. Ancillary areas—feed handling, hydrolysate conditioning,
product recovery and upgrading (hydrotreating) to a final blendstock material, wastewater
treatment, lignin combustion, and utilities—are also included in the design. Detailed material and
energy balances and capital and operating costs for this baseline process are also documented.
This benchmark case study techno-economic model provides a production cost for a cellulosic
renewable diesel blendstock (RDB) that can be used as a baseline to assess its competitiveness
and market potential. It can also be used to quantify the economic impact of individual
conversion performance targets and prioritize these in terms of their potential to reduce cost. The
analysis presented here also includes consideration of the life-cycle implications of the baseline
process model, by tracking sustainability metrics for the modeled biorefinery, including
greenhouse gas (GHG) emissions, fossil energy demand, and consumptive water use.
Building on prior design reports for biochemical ethanol production in 1999, 2002, and 2011,
NREL, together with the Harris Group Inc., performed a feasibility-level analysis for a plausible
conversion pathway to RDB to meet an intermediate DOE cost goal of $5/gallon gasoline
equivalent (GGE) by 2017. The modeled biorefinery processes 2,205 dry ton biomass/day and
achieves an RDB selling price of $5.10/GGE in 2011$ as determined by modeled conversion
targets and “n
th
-plant” project costs and financing, associated with a process RDB yield of 45.4
GGE/dry ton. In addition, the report includes a high-level discussion on improvements needed to
achieve a final 2022 DOE target of $3/GGE moving forward, focused on coproducts from lignin.
ii
Figure ES-1. Economic summary for diesel blendstock production
Minimum Fuel Selling Price (MFSP):
$5.35 /gal
MFSP (Gasoline-Equivalent Basis): $5.10 /GGE
Contributions: Feedstock $1.85 /gal ($1.76/GGE)
Enzymes $0.39 /gal ($0.37/GGE)
Non-Enzyme Conversion $3.11 /gal ($2.96/GGE)
RDB Production 31.3 MMgal/yr (at 68 °F) (32.9 MM GGE/yr)
RDB Yield 43.3 gal / dry U.S. ton feedstock (45.4 GGE/ton)
Bioconversion Metabolic Yield 0.284 kg FFA/kg total sugars (79% of theoretical)
Feedstock + Handling Cost $80.00 /dry U.S. ton feedstock
Internal Rate of Return (After-Tax) 10%
Equity Percent of Total Investment 40%
Capital Costs Manufacturing Costs (cents/gal RDB product)
Pretreatment $51,400,000 Feedstock + Handling 184.9
Neutralization/Conditioning $2,200,000 Sulfuric Acid 6.2
Enzymatic Hydrolysis/Conditioning/Bioconversion $75,400,000 Ammonia (pretreatment conditioning) 3.6
On-site Enzyme Production $12,400,000 Caustic 6.5
Product Recovery + Upgrading $26,600,000 Glucose (enzyme production) 21.7
Wastewater Treatment $60,100,000 Hydrogen 8.4
Storage $3,400,000 Other Raw Materials 19.2
Boiler/Turbogenerator $76,000,000 Waste Disposal 4.5
Utilities $8,800,000 Net Electricity -16.3
Total Installed Equipment Cost $316,300,000 Fixed Costs 44.9
Capital Depreciation 58.7
Added Direct + Indirect Costs $266,400,000 Average Income Tax 34.1
(% of TCI) 46% Average Return on Investment 158.5
Total Capital Investment (TCI) $582,700,000 Manufacturing Costs ($/yr)
Feedstock + Handling $57,900,000
Installed Equipment Cost/Annual Gallon $10.09 Sulfuric Acid $1,900,000
Total Capital Investment/Annual Gallon $18.59 Ammonia (pretreatment conditioning) $1,100,000
Caustic $2,000,000
Loan Rate 8.0% Glucose (enzyme production) $6,800,000
Term (years) 10 Hydrogen $2,600,000
Capital Charge Factor (Computed) 0.135 Other Raw Materials $6,000,000
Waste Disposal $1,400,000
Carbon Retention Efficiencies: Net Electricity -$5,100,000
From Hydrolysate Sugar (Fuel C / Sugar C) 49.5% Fixed Costs $14,100,000
From Biomass (Fuel C / Biomass C) 26.2% Capital Depreciation $18,400,000
Average Income Tax $10,700,000
Maximum Yields (100% of Theoretical)
a
Average Return on Investment $49,600,000
FFA Production (U.S. ton/yr) 172,465
Current FFA Production (U.S. ton/yr)
b
117,587 Specific Operating Conditions
Current Yield (Actual/Theoretical) 68.2% Enzyme Loading (mg/g cellulose) 10
Saccharification Time (days) 3.5
a
Complete conversion of biomass carbohydrates to C16 fatty acid Bioconversion Time (days) 2.9
b
Recovered FFA yield after concentration, sent to hydrotreating Bioconversion FFA titer (wt%) 9%
(Theoretical yields above do not consider refining to final RDB Excess Electricity (kWh/gal) 2.6
product, as refining yield varies with catalyst and conditions) Plant Electricity Use (kWh/gal) 11
All Values in 2011$
Dilute Acid Pretreatment, Enzymatic Hydrolysis, Hydrocarbon (FFA) Bioconversion, Hydrotreating to Paraffins (RDB)
Biological Renewable Diesel Blendstock (RDB) Process Engineering Analysis
