1University of Washington, Energy and Environmental Combustion Laboratory Thermochemical Conversion of Forest Thinnings March 8 th, 2005 – Thesis Defense.

1University of Washington, Energy and Environmental Combustion Laboratory

Thermochemical Conversion of Forest Thinnings

March 8th, 2005 – Thesis Defense –

2University of Washington, Energy and Environmental Combustion LaboratoryAgenda,02-07-05,PYR

Agenda

• Thinning of Forests

• Bio-fuel Production

• Comparison of Alternatives

• Conclusions


Many forests in the western US are at elevated risk to wildfire

Forest or Tinderbox?- Western US Forests -

• Years of active fire suppression on private and public land in the west have led to unnaturally high forest fuel loads

—Small-diameter trees (<6” diameter)—Brush—Dead wood

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

010,02-07-05,PYR.ppt

• 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

• Periodic natural fires regenerate the forest ecosystem by burning out brush and small diameter trees

—Decreased competition among remaining trees—Returns nutrients to soil


One way to reduce the risk of wildfire is to mechanically thin overstocked forests

Mechanical Thinning- Overview -

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

011,02-07-05,PYR.ppt

Before – High Risk Forest After – Thinned Forest

Mechanical Thinning

Source: Reynolds Forestry Consulting - RFC, Inc

• 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?

• 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


Thinnings have a number of energy and non-energy uses

Uses for Thinnings- Overview -

• 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

012,02-07-05,PYR.ppt

Energy UsesEnergy Uses Non-Energy UsesNon-Energy Uses

• Pulp and paper

• Forest products—Emerging small-wood industries—OSB production at small scale—Long-term carbon capture opportunity

• Disposal—Landfill—Pile burning


Of special interest are “stranded” thinnings harvested far from industrial centers

“Stranded” Thinnings- Key Concerns -

009,02-07-05,PYR.ppt

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

Okanogan National Forest- Example -

• 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

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

Wood Chips

Wood Pellets

Bio-oil Methanol

350 kg/m3 640 kg/m3 1200 kg/m3 790 kg/m3

Low-grade Solid Fuel

High-grade Solid Fuel

Low-grade Liquid Fuel

High-grade Liquid Fuel

Source: Rural Technology Initiative


Agenda




• Conclusions

Agenda,02-07-05,PYR


We are interested in optimal size and location for the bio-fuel production facility

Bio-fuel Network- Layout -

007,02-07-05,PYR.ppt

Logging Deck

Logging Road

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

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 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

Forested Area

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)


Producing a high-grade solid fuel, like pellets, is primarily a mechanical process

Pellet Production- Process Flow -

017,02-07-05,PYR.ppt

Dryerto 10% moisture

Grindingto 3 mm Pelletization

Pile Burner

Exhaust

Power127 kWhr/dry ton


Mineral Ash

Flue Gas

Power31 kWhr/ton water

Diesel Engine

Diesel Fuel

Process Power

Additives

• 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

Solid Phase

Gas Phase

Legend

Primary PathInput or Secondary Path

Problem


Fast pyrolysis produces a low grade bio-fuel, commonly referred to as bio-oil

Low-grade Liquid Bio-fuel Production- Overview -

016,02-07-05,PYR.ppt

• 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

• Three categories of decomposition products

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

• 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

• Condensable Vapors• Light Gas• Char

Component Yield (dry mass%)

• 70-80%• 10-15%• 10-15%

• 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


Production of bio-oil involves relatively few process steps

Bio-oil Production- Process Flow -

006,02-07-05,PYR.ppt

Solid Phase

Gas Phase

Liquid Phase

Legend


Dryerto 10% moisture

Grindingto 3 mm

Fast Pyrolysis Reactor

Suspension Combustor

Exhaust



Cyclone Separation

Storage

Bio-oil

Mineral Ash

Power

Heat Exchanger

Power10 kWhr/ton bio-oil

Flue Gas

Power31 kWhr/ton water

Dual Fuel Diesel Engine

Diesel Fuel7.5% energy

Bio-oil92.5% energy

Process Power

Heat Exchanger

Heat

Waste Heat

Char and Ash

Light Gas

Vapor Quench

Problem


Most research has been focused on the production of high-grade bio-fuels

High Grade Liquid Bio-fuel Production- Overview -

013,02-07-05,PYR.ppt

• Dependent Processes―Some clean-up requirements

driven by gasification

Gasification

Gas Clean-up

Bio-fuel Synthesis

High-grade Liquid Bio-fuel

• Largely stand-alone―Developed for use in

petrochemical industry―New interest for extraction

of “stranded” resources (e.g. natural gas)

Dirty Syngas

Clean Syngas

• Gasification―Thermal decomposition of biomass in oxygen deficient

environment (fuel rich)―Produces a syngas of CO, H2, CO2, and H2O (and N2)

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

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


For example, gasification and tar removal are closely coupled

Biomass Gasification- Gasification and Tar Removal -

015,02-07-05,PYR.ppt

• 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:

Entrained Flow Gasifier

Syngas

Oxygen

Wood Particles

Air Separation UnitAir Nitrogen

Indirect Gasifier

Syngas + Tar

Steam

Wood Chips

ExternalHeat

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

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

Indirect GasificationEntrained Flow Gasification

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

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


The devil is in the details. Key issues include gas cleaning, gasifier design, and heat and power integration.

Methanol Production- Process Flow -

014,02-07-05,PYR.ppt

Drying

Catalytic Tar Cracking

Coarse Sizing Gasifier

Multi-cyclone

Particulate > 5μm

Wet Gas Cleaning(100oC)

Particulate > 2μm, Alkali Metals

Dirty Syngas

Steam Reformer(890oC)

Steam

Syngas Compression

Water-Gas Shift(330oC)

CO2 Removal(127oC)

Methanol Synthesis(260oC)

Methanol

Power

MethanolSynthesis

Gas Cleaning

Catalyst

Gasification

Power

Pile BurnerAux. Power Generation

PowerFlue Gas Power, Heat

Clean Syngas

Power

Steam Power

Solid Phase

Gas Phase

Liquid Phase

Legend


Problem

Purge Gas

CO2, Acid Gasses

Power Generation

Power

Heat

Power

HeatDiesel

Fuel

Bag Filtration(350oC)

Residual Contaminants, Waste Water

Water


Clearly, each bio-fuel has advantages and disadvantages

008,02-07-05,PYR.ppt

Bio-Fuel Comparison- Summary -

Wood Chips Pellets Bio-oil Methanol

Transportation Cost - - + + + + +

Technical Readiness + + + - - -

Product Value - -

-

+ +

Production Cost + + + - -

Feedstock Requirement

+- - - -

Potential for Improvement?

N/A - - + + + +

N/A

-

How do we quantify these trade-offs?

-


Agenda




• Conclusions

Agenda,02-07-05,PYR


Net thinning cost is an appropriate metric to compare different scenarios

Net Thinning Cost- Framework -

018,02-07-05,PYR.ppt

Net Thinning Cost

Revenue

• Bio-fuel• Power• Heat

Gross Thinning Cost

Thinning TransportationBio-Energy Production

• Harvesting activities

• Transportation of wood chips or densified bio-fuel

• Bio-fuel production• Co-fire or cogeneration

18University of Washington, Energy and Environmental Combustion Laboratory031,02-07-05,PYR.ppt

Net Thinning Cost- Base Case Results -

Mobile Bio-fuel Production

Transportable Bio-fuel

Production

Stationary 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

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

450 km (~280 miles)7.5 wet tons/acre10 years80,000 acres

Relocatable Bio-fuel

Production

$61/wet ton

$58/wet ton

$74/wet ton


$30

$35

$40

$45

$50

$55

$60

$65

$70

$75

$80

150 250 350 450 550 650 750

Bio-oil

Pulp Sale

Wood Chip Cogeneration

Pellets

Methanol

Co-fire

Landfill

For shorter transportation distances, co-fire is preferred by a wide margin

020,02-07-05,PYR.ppt

Transportation Distance Sensitivity- Base Technology -

Net Thinning Cost

($/wet ton thinnings)

Average Transportation Distance (Deck to End-Use)(km)

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

Case Assumptions

Two drivers required for round-trip distance

Disposal preferred beyond this point

Net thinning cost for methanol and bio-oil converge

Bio-oil preferred over pulp sale


$30

$35

$40

$45

$50

$55

$60

$65

$70

$75

$80

150 250 350 450 550 650 750

Advanced Bio-oil

Pulp Sale

Wood Chip Cogeneration

AdvancedMethanol

Co-fire

Landfill

Advanced fast pyrolysis for production of bio-oil is cost competitive with pulp sale or cogeneration at shorter distances

021,02-07-05,PYR.ppt

Transportation Distance Sensitivity- Advanced Technology -

Net Thinning Cost

($/wet ton thinnings)

Average Transportation Distance (Deck to End-Use)(km)

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

Case Assumptions

Net thinning cost for methanol and bio-oil converge further out

Bio-oil preferred over pulp sale much earlier


For a given transportation distance, annual acreage thinned, and thinning duration, we can determine the lowest net thinning cost

005,02-07-05,PYR.ppt

Mapping Bio-energy Options - Methodology -

Mobile

Transportable

Stationary

Relocatable

Mobile

Transportable

Stationary

Relocatable

Mobile

Transportable

Stationary

Relocatable

Fast Pyrolysis

Fast Pyrolysis

Fast Pyrolysis

Fast Pyrolysis

Pelletization

Pelletization

Pelletization

Pelletization

Methanol Synthesis

Methanol Synthesis

Methanol Synthesis

Methanol Synthesis

Co-fire

Wood Chip Cogen

Pulp Sale

Disposal

Scenario Results

Facility Bio-Energy Production Net Thinning Cost

$160/wet ton

$83/wet ton

$56/wet ton

$62/wet ton

$163/wet ton

$95/wet ton

$61/wet ton

$63/wet ton

$215/wet ton

$129/wet ton

$64/wet ton

$83/wet ton

$68/wet ton

$82/wet ton

$74/wet ton

$79/wet ton

Bio-Energy Technology Map- 500 km Transportation Distance, Base Technology -

Annual Acreage Thinned(acres)

Thinning Duration (years)

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

1 3 5 7 9 11 13 15

Repeat analysis for each thinning acreage and duration for multiple transportation distances…


For short transportation distances, bio-fuel production is unattractive

001,02-07-05,PYR.ppt

Bio-Energy Technology Map - 200 km Transportation, Base Technology -


10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

1


3 5 7 9 11 13 15

Co-fire

Pulp Sale• 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

Trends


As transportation distance increases, densified bio-fuels become preferred to co-fire and pulp sale

002,02-07-05,PYR.ppt

Bio-Energy Technology Map - 500 km Transportation, Base Technology -



PelletizationStationary

Pulp Sale

Fast PyrolysisStationary

Relocatable

Methanol SynthesisStationary

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

1 3 5 7 9 11 13 15

• 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

Technology Map Trends

Relocatable

Relocatable

Stat.

Stat.


Near term improvements in bio-fuel production technologies are likely to make fast pyrolysis the option of choice for long transportation distances

003,02-07-05,PYR.ppt

Bio-Energy Technology Map - 500 km Transportation, Advanced Technology -



Pulp Sale

AdvancedFast Pyrolysis

Stationary

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

1 3 5 7 9 11 13 15

• 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


Relocatable

Pellet


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

004,02-07-05,PYR.ppt

Bio-Energy Technology Map - 200 km Transportation, Advanced Technology, No Co-fire -



Pulp Sale

AdvancedFast Pyrolysis

Stationary

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

1 3 5 7 9 11 13 15

• 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



Agenda




• Conclusions

Agenda,02-07-05,PYR


Bio-fuel Production- Conclusions -

022,02-07-05,PYR.ppt

• 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 (RD&D)

—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


Different options are preferred for different transportation distances

030,02-07-05,PYR.ppt

Technology Summary- Conclusions -

SmallOperation

< 400 km Transportation Distance

ModerateOperation

LargeOperation

> 400 km Transportation Distance

Pulp Sale

Co-fire

Disposal

Methanol

Pellets

Fast Pyrolysis

Disposal

Advanced Fast Pyrolysis


This analysis allows us to answer a few key questions

Bio-Energy from Thinnings- Conclusions -

024,02-07-05,PYR.ppt

• 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


Next Steps

025,02-07-05,PYR.ppt

• 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


Questions?

028,02-07-05,PYR.ppt


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.

019,02-07-05,PYR.ppt

Bio-oil Production- Cost Detail -

-$50

$0

$50

$100

$150

$200

Production$141

Transportation $8

Net Thinning

Cost($/ton wet thinnings)

Harvest$40

Production$52

Transportation $12– Bio-oil $8

– Wood Chips $2– Bio-oil $101

Revenue$19

Revenue$23

Harvest$40

Production$27

Harvest$40

Revenue$26

Transportation $12– Wood Chips $7– Bio-oil $6

Mobile$159/wet ton

thinnings

Transportable$81/wet ton thinnings

Stationary$54/wet ton thinnings

Note: Revenue increase due to higher yields of bio-oil for stationary and transportable production

1Higher cost due to higher bio-oil yield for transportable conversion


An interesting extension of this analysis is to forecast costs for technical advances and the benefit of learning scale

Advanced Technology Case- Assumptions -

027,02-07-05,PYR.ppt

Technology

Learning Scale

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

• 1st unit costs • 10th unit costs• Justified by successful

first generation demonstrations

• 1st unit costs • 1st unit costs• No successful

commercial demonstration

Fast Pyrolysis Methanol Synthesis

Substantial cost reduction Modest cost reduction, Enhanced practicality

These scenarios represent advanced, but realistically near-term process evolutions

1University of Washington, Energy and Environmental Combustion Laboratory Thermochemical Conversion of Forest Thinnings March 8 th, 2005 – Thesis Defense.

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