Thermochemical Conversion of Forest Thinnings

1
Thermochemical Conversion of Forest
Thinnings March 8th, 2005 Thesis Defense
2
Agenda

• Thinning of Forests
• Bio-fuel Production
• Comparison of Alternatives
• Conclusions

Agenda,02-07-05,PYR
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Many forests in the western US are at elevated
risk to wildfire
Forest or Tinderbox? - Western US Forests -

• Periodic natural fires regenerate the forest
  ecosystem by burning out brush and small diameter
  trees
• Decreased competition among remaining trees
• Returns nutrients to soil

• Years of active fire suppression on private and
  public land in the west have led to unnaturally
  high forest fuel loads
• Small-diameter trees (lt6 diameter)
• Brush
• Dead wood

• High fuel density enables wildfires
• Burns hotter than natural fires
• Can consume both large and small trees
• Long eco-system recovery
• Expensive to fight
• Dangerous for firefighting personnel

• As of 2002, the US Forest Service listed 120
  million acres at unnatural risk for wildfire

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One way to reduce the risk of wildfire is to
mechanically thin overstocked forests
Mechanical Thinning - Overview -
Mechanical Thinning
Before High Risk Forest
After Thinned Forest

• Mechanical thinning involves the removal of small
  diameter trees to create a more natural forest
• Simulate end-state of a natural burn

• Numerous benefits to thinning include
• Decreased risk of wildfire
• Improved resistance to insect infestation and
  disease
• Remaining trees grow larger and faster due to
  decreased competition

• However, thinnings have little traditional
  commercial value
• Thinning can not pay for itself (unless combined
  with commercial logging highly contentious)
• So what do you do with all the material you
  remove from the forest?

Source Reynolds Forestry Consulting - RFC, Inc
011,02-07-05,PYR.ppt
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Thinnings have a number of energy and non-energy
uses
Uses for Thinnings - Overview -
Energy Uses
Non-Energy Uses

• Wood chip cogeneration
• Production of power and low-grade heat or steam
  from wood chips
• Co-fire
• Substitute wood chips for fraction of coal at
  conventional power plant
• Produce a bio-fuel
• Methanol commodity chemical, transportation fuel
  
• Bio-oil industrial fuel, refining feedstock
• Wood Pellets residential fuel

• Pulp and paper
• Forest products
• Emerging small-wood industries
• OSB production at small scale
• Long-term carbon capture opportunity
• Disposal
• Landfill
• Pile burning

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Of special interest are stranded thinnings
harvested far from industrial centers
Stranded Thinnings - Key Concerns -
Okanogan National Forest - Example -

• Stranded thinnings are typified by long
  transportation distance to end-use markets

• For long transportation distances, fuel density
  becomes a key concern and fuel densification will
  reduce transportation costs

Wood Chips
Wood Pellets
Bio-oil
Methanol
Low-grade Solid Fuel
High-grade Solid Fuel
Low-grade Liquid Fuel
High-grade Liquid Fuel
350 kg/m3
640 kg/m3
1200 kg/m3
790 kg/m3

• 763,000 acres at risk to wildfire
• More than 70 total forested acreage
• Urgent thinning need

• But densification comes at a cost

• Stranded thinnings
• No local market for pulp
• East of Cascade Crest (east-west barrier) and
  distant from Spokane

Source Rural Technology Initiative
009,02-07-05,PYR.ppt
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Agenda

• Thinning of Forests
• Bio-fuel Production
• Comparison of Alternatives
• Conclusions

Agenda,02-07-05,PYR
8
We are interested in optimal size and location
for the bio-fuel production facility
Bio-fuel Network - Layout -
Logging Deck

• Option 1 Mobile Bio-fuel Production
• Highly mobile unit built on semi-trailer
• 10 dry tons per day throughput
• Spends days to a week at logging deck
• 15 year lifetime

• Option 4 Relocatable Bio-fuel Production
• Relocatable facility located at edge of forest in
  industrial zone (grid electricity available)
• 500 dry tons per day throughput
• In position for duration of thinning operation
  (20 year lifetime)

• Option 2 Transportable Bio-Fuel Production
• Modular design readily transported in several
  semi-trailer containers
• 100 dry tons per day throughput
• Spends months at collection area
• 15 year lifetime

Forested Area
Logging Road

• Option 3 Stationary Bio-fuel Production
• Stationary facility located at edge of forest in
  industrial zone (grid electricity available)
• Sized so single facility consumes entire daily
  production from forest
• Lifetime equal to duration of thinning operation

Major Road
007,02-07-05,PYR.ppt
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Producing a high-grade solid fuel, like pellets,
is primarily a mechanical process
Pellet Production - Process Flow -
Flue Gas
Additives
Power 127 kWhr/dry ton
Power 114 kWhr/dry ton
Power 31 kWhr/ton water
Dryer to 10 moisture
Grinding to 3 mm
Pelletization

• Pellets formed by high pressure extrusion of
  ground wood through die
• Pressure raises temperature to over 100oC
• Lignin begins to flow and acts as an adhesive
  when cooled
• Limited research opportunities
• Grinding requirement fixed by standardized pellet
  size
• Mature technology with respect to woody biomass

Exhaust
Legend
Pile Burner
Diesel Engine
Solid Phase
Process Power
Gas Phase
Problem
Mineral Ash
Diesel Fuel
Primary Path
Input or Secondary Path
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Fast pyrolysis produces a low grade bio-fuel,
commonly referred to as bio-oil
Low-grade Liquid Bio-fuel Production - Overview -

• Fast pyrolysis is defined as the thermal
  decomposition of biomass by rapid heating in the
  absence of oxygen

• Three categories of decomposition products

Component
Yield (dry mass)

• Condensable Vapors
• Light Gas
• Char

• 70-80
• 10-15
• 10-15

• Condensed vapors are collectively referred to as
  pyrolysis oil or bio-oil
• Mixture of oxygenated hydrocarbons and water
  water is the most common single species
• High density liquid fuel (1200 kg/m3) with
  moderate heating value (16-19 MJ/kg)
• Potential applications for industrial heating,
  power generation, and chemical feedstock for
  bio-refining

• Bio-oil has a number of undesirable
  characteristics
• Low pH (2.5-3) due to organic acids (e.g. acetic
  acid)
• High solids content (1 by mass) incompatible
  with downstream applications requiring low solids
  content (e.g. gas turbines)
• High water content (20-30) immiscible with
  hydrocarbon fuels due to polar nature
• Over time, chemical composition changes
  (non-equilibrium) increasing viscosity and water
  content and decreasing volatility

• Fast pyrolysis reactor development driven by
  char-related issues
• Rapid, isothermal heating lower temperatures
  favor char formation substitution effect
• Short vapor residence time (1-2 seconds max)
  char catalyzes cracking of condensable vapors to
  light gas
• Rapid and effective char removal char fines
  entrained in bio-oil accelerate aging effects

016,02-07-05,PYR.ppt
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Production of bio-oil involves relatively few
process steps
Bio-oil Production - Process Flow -
Flue Gas
Power 127 kWhr/dry ton
Power 40 kWhr/dry ton
Power 31 kWhr/ton water
Power
Dryer to 10 moisture
Grinding to 3 mm
Fast Pyrolysis Reactor
Cyclone Separation
Heat
Char and Ash
Heat Exchanger
Exhaust
Vapor Quench
Suspension Combustor
Dual Fuel Diesel Engine
Light Gas
Process Power
Legend
Solid Phase
Gas Phase
Mineral Ash
Diesel Fuel 7.5 energy
Bio-oil 92.5 energy
Liquid Phase
Heat Exchanger
Problem
Storage
Waste Heat
Primary Path
Input or Secondary Path
Power 10 kWhr/ton bio-oil
Bio-oil
006,02-07-05,PYR.ppt
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Most research has been focused on the production
of high-grade bio-fuels
High Grade Liquid Bio-fuel Production - Overview -

• Gasification
• Thermal decomposition of biomass in oxygen
  deficient environment (fuel rich)
• Produces a syngas of CO, H2, CO2, and H2O (and N2)

Gasification

• Dependent Processes
• Some clean-up requirements driven by gasification

Dirty Syngas
Gas Clean-up

• Gas Clean-up
• Tar
• Particulate
• Alkali metal vapor

Clean Syngas

• Largely stand-alone
• Developed for use in petrochemical industry
• New interest for extraction of stranded
  resources (e.g. natural gas)

• Liquid Fuel Synthesis
• Optimize CO and H2 concentrations in syngas
• Gas to liquid (GTL) process

Bio-fuel Synthesis
High-grade Liquid Bio-fuel
013,02-07-05,PYR.ppt
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For example, gasification and tar removal are
closely coupled
Biomass Gasification - Gasification and Tar
Removal -

• Syngas produced by the gasifier must be free of
  nitrogen
• Higher gas volume increases capital cost
• Catalysts less effective when syngas diluted by
  nitrogen

• Two gasification options being pursued

Indirect Gasification
Entrained Flow Gasification
Syngas Tar
Syngas

• Wet scrubbing
• Removes most tar
• Lose tar energy
• Waste water stream
• Thermodynamic penalty for quench

Entrained Flow Gasifier
Indirect Gasifier
Wood Particles
Wood Chips

• Catalytic tar cracking
• Recover tar energy
• Not all tar removed
• Short catalyst lifetime

Oxygen
Air Separation Unit
Steam
External Heat
Air
Nitrogen

• Re-circulate tars
• Removes most tar
• Recovers tar energy
• Thermodynamic penalty for quench
• May produce PAH (carcinogenic)

• Very high capital cost at smaller scale
• High power consumption

015,02-07-05,PYR.ppt
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The devil is in the details. Key issues include
gas cleaning, gasifier design, and heat and power
integration.
Legend
Methanol Production - Process Flow -
Solid Phase
Gas Phase
Power
Power
Flue Gas
Power, Heat
Liquid Phase
Problem
Drying
Coarse Sizing
Gasifier
Gasification
Primary Path
Input or Secondary Path
Diesel Fuel
Heat
Dirty Syngas
Aux. Power Generation
Pile Burner
Power
Catalyst
Power
Water
Wet Gas Cleaning (100oC)
Gas Cleaning
Catalytic Tar Cracking
Syngas Compression
Bag Filtration (350oC)
Multi-cyclone
Particulate gt 5µm
Particulate gt 2µm, Alkali Metals
Residual Contaminants, Waste Water
Clean Syngas
Steam
Power
Steam
Power
Purge Gas
Power
Power Generation
Heat
Methanol Synthesis
Methanol Synthesis (260oC)
Steam Reformer (890oC)
Water-Gas Shift (330oC)
CO2 Removal (127oC)
Methanol
CO2, Acid Gasses
014,02-07-05,PYR.ppt
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Clearly, each bio-fuel has advantages and
disadvantages
Bio-Fuel Comparison - Summary -
Pellets
Bio-oil
Wood Chips
Methanol
Transportation Cost
- -



Technical Readiness


-
- -
-
Product Value
- -

-
-
Production Cost


- -
Feedstock Requirement

- -
- -
N/A
Potential for Improvement?
N/A
- -


How do we quantify these trade-offs?
008,02-07-05,PYR.ppt
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Agenda

• Thinning of Forests
• Bio-fuel Production
• Comparison of Alternatives
• Conclusions

Agenda,02-07-05,PYR
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Net thinning cost is an appropriate metric to
compare different scenarios
Net Thinning Cost - Framework -
Net Thinning Cost
Revenue
Gross Thinning Cost

• Bio-fuel
• Power
• Heat

Thinning
Transportation
Bio-Energy Production

• Harvesting activities

• Transportation of wood chips or densified bio-fuel

• Bio-fuel production
• Co-fire or cogeneration

018,02-07-05,PYR.ppt
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Net Thinning Cost - Base Case Results -

• Transportation Distance
• Thinning Yield
• Thinning Duration
• Annual Acreage Thinned

450 km (280 miles) 7.5 wet tons/acre 10
years 80,000 acres
Transportable Bio-fuel Production
Stationary Bio-fuel Production
Relocatable Bio-fuel Production
Mobile Bio-fuel Production

• Wood Pellets
• Bio-oil
• Methanol
• Wood Chip Cogeneration
• Co-fire
• Pulp Sale

162/wet ton 159/wet ton 214/wet ton 75/wet
ton 63/wet ton 71/wet ton
93/wet ton 81/wet ton 126/wet ton
59/wet ton 54/wet ton 59/wet ton
61/wet ton 58/wet ton 74/wet ton
031,02-07-05,PYR.ppt
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For shorter transportation distances, co-fire is
preferred by a wide margin
Transportation Distance Sensitivity - Base
Technology -
Two drivers required for round-trip distance
Net Thinning Cost (/wet ton thinnings)
Case Assumptions

• Thinning Duration 10 years
• Annual Acreage 80,000 acres

Average Transportation Distance (Deck to
End-Use) (km)
020,02-07-05,PYR.ppt
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Advanced fast pyrolysis for production of bio-oil
is cost competitive with pulp sale or
cogeneration at shorter distances
Transportation Distance Sensitivity - Advanced
Technology -
Net Thinning Cost (/wet ton thinnings)
Case Assumptions

• Thinning Duration 10 years
• Annual Acreage 80,000 acres

Bio-oil preferred over pulp sale much earlier
Average Transportation Distance (Deck to
End-Use) (km)
021,02-07-05,PYR.ppt
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For a given transportation distance, annual
acreage thinned, and thinning duration, we can
determine the lowest net thinning cost
Mapping Bio-energy Options - Methodology -
Scenario Results
Bio-Energy Technology Map - 500 km Transportation
Distance, Base Technology -
Facility
Bio-Energy Production
Net Thinning Cost
Mobile
Fast Pyrolysis
160/wet ton
Thinning Duration (years)
Transportable
Fast Pyrolysis
83/wet ton
1
3
5
7
9
11
13
15
Stationary
Fast Pyrolysis
56/wet ton
Relocatable
Fast Pyrolysis
62/wet ton
10,000
Mobile
Pelletization
163/wet ton
20,000
Transportable
Pelletization
95/wet ton
30,000
Stationary
Pelletization
61/wet ton
40,000
Annual Acreage Thinned (acres)
Relocatable
Pelletization
63/wet ton
50,000
Mobile
Methanol Synthesis
215/wet ton
60,000
Transportable
Methanol Synthesis
129/wet ton
70,000
Stationary
Methanol Synthesis
64/wet ton
80,000
Relocatable
Methanol Synthesis
83/wet ton
90,000
Co-fire
68/wet ton
100,000
Wood Chip Cogen
82/wet ton
Pulp Sale
74/wet ton
Repeat analysis for each thinning acreage and
duration for multiple transportation distances
Disposal
79/wet ton
005,02-07-05,PYR.ppt
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For short transportation distances, bio-fuel
production is unattractive
Bio-Energy Technology Map - 200 km
Transportation, Base Technology -
Thinning Duration (years)
1
3
5
7
9
11
13
15
Trends
10,000

• Pulp sale preferred for short durations or small
  scale operations
• Least capitally intensive revenue generating
  option
• Co-fire preferred over wide range of durations
  and scales

Pulp Sale
20,000
30,000
40,000
Annual Acreage Thinned (acres)
50,000
60,000
Co-fire
70,000
80,000
90,000
100,000
001,02-07-05,PYR.ppt
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As transportation distance increases, densified
bio-fuels become preferred to co-fire and pulp
sale
Bio-Energy Technology Map - 500 km
Transportation, Base Technology -
Thinning Duration (years)
1
3
5
7
9
11
13
15
Technology Map Trends
10,000
Pelletization Stationary
Pulp Sale

• Pulp sale preferred for very short durations and
  very small scale operations
• Pelletization preferred for moderate to long
  durations or moderate to large thinning yields
• Least capitally intensive densification process
• Methanol synthesis preferred only for very long
  durations and high yields
• Most capitally intensive densification process
• Fast pyrolysis preferred for moderate to large
  yields or moderate to long term operations

20,000
30,000
Relocatable
40,000
Annual Acreage Thinned (acres)
50,000
Stat.
Relocatable
Fast Pyrolysis Stationary
60,000
70,000
80,000
Relocatable
Methanol Synthesis Stationary
90,000
Stat.
100,000
002,02-07-05,PYR.ppt
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Near term improvements in bio-fuel production
technologies are likely to make fast pyrolysis
the option of choice for long transportation
distances
Bio-Energy Technology Map - 500 km
Transportation, Advanced Technology -
Thinning Duration (years)
1
3
5
7
9
11
13
15
Technology Map Trends
10,000
Pellet
Pulp Sale

• Pulp sale preferred for very short durations and
  very small scale operations
• Fast pyrolysis preferred for most other yields
  and durations of operations
• Smaller, shorter duration thinning favor
  relocatable production
• Larger, longer duration thinning favor stationary
  production

20,000
30,000
40,000
Relocatable
Annual Acreage Thinned (acres)
50,000
Advanced Fast Pyrolysis Stationary
60,000
70,000
80,000
90,000
100,000
003,02-07-05,PYR.ppt
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When co-fire is not an option, as might be the
case in Washington, advanced fast pyrolysis
becomes the lowest cost option even for short
transportation distances
Bio-Energy Technology Map - 200 km
Transportation, Advanced Technology, No Co-fire -
Thinning Duration (years)
1
3
5
7
9
11
13
15
Technology Map Trends
10,000

• Co-fire may not be an option in some regions due
  to a scarcity of coal-fired power plants
• Pulp sale preferred for short to moderate
  durations or small to moderate scale operations
• Fast pyrolysis preferred for large or long
  duration thinning operations

20,000
30,000
Pulp Sale
40,000
Annual Acreage Thinned (acres)
50,000
60,000
70,000
Advanced Fast Pyrolysis Stationary
80,000
90,000
100,000
004,02-07-05,PYR.ppt
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Agenda

• Thinning of Forests
• Bio-fuel Production
• Comparison of Alternatives
• Conclusions

Agenda,02-07-05,PYR
27
Bio-fuel Production - Conclusions -

• Bio-fuel production at a stationary facility
  outside the forest is preferred over production
  within the forest
• Economics
• Lower capital unit costs (scale effect)
• Low cost power (grid electricity vs. diesel
  generators)
• Better labor utilization
• High availability (better capital utilization)
• Practicality
• Three-shift operation uncommon within the forest,
  but is common in industry
• Equipment for production of bio-fuels generally
  designed in expectation of fixed, continuous
  operation
• Transportable and mobile scale facilities should
  be considered for research, development, and
  demonstration (RDD)
• Investment cost for a single unit fairly low
• Easy to test and stage investment
• Once technology proven, scale-up to larger
  facilities to realize lowest projected costs

022,02-07-05,PYR.ppt
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Different options are preferred for different
transportation distances
Technology Summary - Conclusions -
lt 400 km Transportation Distance
gt 400 km Transportation Distance
Small Operation
Disposal
Disposal
Pulp Sale
Pellets
Moderate Operation
Advanced Fast Pyrolysis
Co-fire
Fast Pyrolysis
Large Operation
Methanol
030,02-07-05,PYR.ppt
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This analysis allows us to answer a few key
questions
Bio-Energy from Thinnings - Conclusions -

• Does the conversion of thinnings to bio-energy
  make economic sense?
• Yes. But, with current technology, only when the
  transportation distance to end-use exceeds 400
  km.
• Bio-energy will not pay for thinning. But the
  economics are stronger than for disposal in
  almost all cases

• Which bio-energy technologies are most promising?
• Co-fire with coal for transportation distances
  less than 400 km
• Fast pyrolysis for bio-oil where transportation
  distances are longer

• Where are non-energy options preferable?
• Pulp sale for short durations and low yields
  where transportation distances are less than 600
  km
• Disposal for very short durations and low yields
  where transportation distances are longer

024,02-07-05,PYR.ppt
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Next Steps

• Forestry
• Estimated probabilities for various acreage
  yields and durations
• Economics of forest products
• Model
• Rail transportation and hybrid rail-truck
  transportation networks
• Other bio-fuel production technologies
• Solid fuel briquettes
• Fischer-Tropsch fuels
• Other bio-fuel end-uses
• Close-coupled gasification-combustion
  applications
• Biomass Gasification Combined Cycle (BiGCC)
• Improved visualization of results
• Research
• Methods for improved bio-oil combustion
• Large feedstock fast pyrolysis

025,02-07-05,PYR.ppt
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Questions?
028,02-07-05,PYR.ppt
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Net thinning costs are lowest for stationary
bio-fuel production. The small penalty for
transporting chips out of the forest is
outweighed by large reductions in bio-fuel
production cost.
Bio-oil Production - Cost Detail -
Mobile 159/wet ton thinnings
Transportable 81/wet ton thinnings
Stationary 54/wet ton thinnings
Transportation 8
Transportation 12

• Bio-oil 8

• Wood Chips 2
• Bio-oil 101

Net Thinning Cost (/ton wet thinnings)
Transportation 12

• Wood Chips 7
• Bio-oil 6

Production 141
Production 52
Production 27
Harvest 40
Harvest 40
Harvest 40
Note Revenue increase due to higher yields of
bio-oil for stationary and transportable
production
Revenue 19
Revenue 23
Revenue 26
1Higher cost due to higher bio-oil yield for
transportable conversion
019,02-07-05,PYR.ppt
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An interesting extension of this analysis is to
forecast costs for technical advances and the
benefit of learning scale
Advanced Technology Case - Assumptions -
Fast Pyrolysis
Methanol Synthesis
Base Case
Advanced Case
Base Case
Advanced Case

• 3 mm chip size
• Hammer-milling required

• 6 mm chip size
• Coarse sizing only

• Wet, cold gas cleaning

• Hot, dry gas cleaning

Technology

• 1st unit costs

• 10th unit costs
• Justified by successful first generation
  demonstrations

• 1st unit costs

• 1st unit costs
• No successful commercial demonstration

Learning Scale
Substantial cost reduction
Modest cost reduction, Enhanced practicality
These scenarios represent advanced, but
realistically near-term process evolutions
027,02-07-05,PYR.ppt