Woody Biomass to Energy: Overview of Conversion PathwaysOverview of Conversion Pathways
Woody Biomass WorkshopWoody Biomass Workshop
Ukiah, CA
December 2, 2010
John R. ShellyUC Cooperative Extension
University of California, Berkeley
John Shelly, University of California at Berkeley, Cooperative Extension December 2, 2010
Biomass Sourcesiomass SourcesWoody BiomassSawmill Residue
Other BiomassAgricultural Residues
Landfill DiversionLogging ResidueDedicated Forest
Grass crops‐ switch grass‐miscanthusDedicated Forest
Fuel Reduction ThinningDead Trees Ch l
miscanthus
Chaparral
California Biomass 200740
Total
40
Total
30
35Total
(million BDT/yr)
Gross Potential 83 Technically available 32.4
30
35Total
(million BDT/yr)
Gross Potential 83 Technically available 32.4
20
25
n BD
T/yr
y
20
25
n BD
T/yr
y
15
20
Milli
on
15
20
Milli
on
5
10
5
10
0Agriculture Municipal waste Logging/Slash Forest thinnings Sawmill
ResiduesChaparral
0Agriculture Municipal waste Logging/Slash Forest thinnings Sawmill
ResiduesChaparral
US Energy DemandUS Energy Demand
95100
859095
BT
U
707580
drill
ion
556065
Qua
501970 1980 1990 2000 2010 2020 2030 2040
Year
Source: Energy Information Administration: Annual Energy Outlook 2007
US Renewable Fuel DemandUS Renewable Fuel Demand12
8
10
llons
4
6
illio
n G
al
0
2
Bi
01975 1980 1985 1990 1995 2000 2005 2010 2015
Year
Source: Renewable Fuels Association 2010
Global Carbon Cycle (billion metric tons)
6 3
+ 3.2 Billion tons per year to atmosphere
119 120
6.388 90
Oceans
Vegetation and Soils
Caused by human activit
Potential Uses and CompetitionPotential Uses and Competition
• Energy feedstock (heat and electricity)Energy feedstock (heat and electricity)• Landscape materials & soil amendments
i f d k i l• Extra steps in feedstock preparation elevate woody biomass to a higher value resource– Fiber resource – pulp or composites (particleboard, wood‐
plastic lumber, etc.)
Bio refinery i h i l i l di bi f l– Bio‐refinery – organic chemicals including biofuels
Characteristics and Cost Factors of
L dfill Di i t f ti t t bl
Various Types of Biomass
• Landfill Diversion – cost of sorting out unacceptable materials and grinding is offset by tipping fees
• Sawmill Residue – clean sawdust wood andSawmill Residue clean sawdust, wood, and bark…costs offset by lumber manufacturing; can be used as raw material for value‐added products
• Logging Residue – collection, grinding or chipping costs are offset by timber value
l l d• Agricultural Residue – costs offset by crop value
• Forest/Fuel Reduction Thinning or Salvage – costs d b th l f th bi d d???covered by the value of the biomass produced???
John Shelly, UC Berkeley Cooperative Extension
What Role Will Biomass Play in Helping Meet the Ever‐GrowingHelping Meet the Ever Growing
Demand for Energy?
Conversion Pathways
Thermochemical Combustion Heat El t i it
Thermochemical P rol sis
HeatElectricity
Electricity
• Pyrolysis• Gasification
ElectricityBio-dieselAlcoholOrganic chemicals
Biochemical• Anaerobic digestion
Hydrolysis/Fermentation
Organic chemicals
AlcoholOrganic chemicals• Hydrolysis/Fermentation
Organic chemicalsPhysiochemical
• Heat/Pressure/Catalysts
Organic chemicals
g• Heat/Pressure/Catalysts
Typical Biomass‐Fired Powerplantyp p
20 MW i• 20 MW capacity• Processes 140 - 200 thousand tons/yr (1BDT/MW/hour)• Biomass transported up to 50 miles• Delivered biomass valued at $15 - 25 per tonDelivered biomass valued at $15 25 per ton• Average production cost ~ $0.05 - $0.07/kWh
John Shelly, UC Berkeley Cooperative Extension
Combustion – A Basic Thermal Technology
COCO2 2 + + HH22OO
Fuel Fuel
Combustion Heat
Excess AirExcess Air
BoilerEmissions
Excess AirExcess AirAsh
o e• COCO
•• NoNoxx
•• SOSOElectricity or CHP
Steam, Heat
SOSOxx
•• othersothers
Pyrolysis Heating of biomass to temperature of 400 - 800 F with limited or no air producing voc, CO2 and H2 and solid char 2 2and particulates (smoke)
Torrefaction or Torrefied BiomassSource: Agri-Tech Producers, LLC
Source: Gareth Mayhead
Charcoal Production in the woods
•This method used for > 1000 years
•Mild pyrolysis, about 1 hour at 450 °F
•Removes moisture and light volatile material, leaves about 70% of original dry-weight of feedstock and about 90% of original energy
•Burns part of the batch for heat input
•Air Quality issues with this method
Basic Pyrolysis Technology• Thermal decomposition of biomass without oxygen (400 – 900 °F).• Products of thermal decomposition are char, tar, and Pyrolysis gas
(methane(methane,• Controlling temperature and residence time products produced. Low
temperatures favor char production, higher temperatures favor tar and gas productsgas products.
PyrolysisChar
(biochar) Torrified Bi
Soil amendment
?
tar
Pyrolysis gas
Biomass
Fuel for
Upgrade to bio-oil
gas Fuel for Combustion
or gasification
Fl idi d B d G ifi (W tFluidized Bed Gasifier (West Biofuels, Inc. demonstration unit) – Designed to convert 5
tons of biomass to a combustible producer gas
that can be further refined athat can be further refined a synthetic gas (syngas) and to to higher value biochemicals
including biofuelsincluding biofuels.
Operating parameters:Operating parameters:• T = 1400 degrees F• 5 tons Biomass per hour• Theoretical Yield -- enough
t d b t 500syngas to produce about 500 gals ETOH
Basic Gasification TechnologyBoiler Steam,
HeatFuel Gas
Fuel (woody Fuel (woody biomass)biomass)
Gasification Electricity or CHP
Fuel Gas (CO2 +
H2 + hydro-carbon
Engine
Gas Turbinecarbon gases
Fuel Cell
Syngas
Liquid FuelsOxidant Oxidant
( i ( i Tar,
Particulates
HeatHeat
Syngas(air or (air or oxygen)oxygen)
Particulates, H2S, NH3
Char + Ash
Gasification is the “Partial Oxidation” (controlled amount of air or oxygen) of an organic material to produce a combustible, gaseous mixture (producer
Ash
gas) of many compounds that can be used directly as a low BTU fuel gas or cleaned to make syngas that can be used to produce higher value products.
Energy in Product Gas & Relative Characteristics of Gasifier Types
• Air gasification* (partial oxidation in air)– Generates Producer Gas with high N2 dilution low heating value.
Energy Content (Btu/ft3)
~ 100-200• Oxygen gasification (partial oxidation using pure O2)
– Generates synthesis gas (Syngas) with low N2 in gas and medium heating value
• Indirect heat w/ Steam gasificationG t hi h H t ti l N i d di h ti l C l
~ 300-400
~300-450
Do ndraft Updraft Bubbling Circulating Entrained
– Generates high H2 concentration, low N2 in gas and medium heating value. Can also use catalytic steam gasification with alkali carbonate or hydroxide
Natural Gas ~ 1000 (Btu/ft3)* Small systems are generally “Air-blown” downdraft or updraft gasifiers
Downdraft Updraft gFB
gFB Flow
Fuel Particle Size (in.) 0.5 - 4 0.25 - 4 0.5 - 3 0.5 - 3 Small < 0.1
Moisture Content (%) <30 (prefer<15) < 60 < 40 < 40 < 15
Relative Tar Production low high moderate moderate very low
Scale(F l i t)
(MM Btu/hr) < 34 < 70 34 - 340 34 - ?? > 340
(Dry tons(Fuel input) (Dry tons wood/hr) < 2 < 4 2 - 20 2 - ?? > 20
Knoef, H.A.M., ed. (2005). Handbook of Biomass Gasification. BTG biomass technology group: Enschede, The Netherlands.
Life Cycle Inventory Analysis
Harvest
Raw Material
E/$ Harvest
Collection Emissions
E/$
E/$
TransportationE/$
Feedstock Prep.
Residue
E/$
Process Residue handlingE/$
Product E/$
Competing Cellulosic Feedstocks
Cellulose Hemi-Cellulose
Energy Cont ent(BTU/lb)
Yield (tons/acre)
Bulk Den. (kg/m3)
Million BTU/m3
Switch 45% 45% 7 000 20 108 1 7Switch-grass
45% 45% 7,000 20 108 1.7
Miscanthus 45 24 7,700 60 80 1.4
Corn Stover 35 25 7,300
Bagasse 40 22 7,500 60 1,
Wood 42 25 8,000 10 450 8
Coal 10,000 800 17.6
t t ti t d i ti i ttransportation costs and energy conversion ratio are impt.
Example of Competing Uses
Sawmill Co‐gen
Ag Residue BarkSawdust
Bagged Soil Amendment
Th C ti l t d 8 MW f l t i it dThe Co-generation plant produces 8 MW of electricity and steam to operate the lumber dry kilns. The sawmill residues are more valuable for soil amendments than fuel for the boiler. The sawmill purchases lower value fuel in the biomass market.
CombustionCombustionPROS
Si lCONS
i l i i• Simple process to produce heatG i i
• Particulate emissions may not meet clean air requirements• Gaseous emissions are
similar to those of the natural decomposition
requirements
natural decomposition of wood
GasificationGasificationPROS
d il f lCONS
l h• Produces a versatile fuel gas that can be:
used directly or stored
• Lower BTU value than natural gas or LPGHi h d ti t– used directly or stored
– combusted to produce heat
• High production costs (capital and operating)
• Tar contaminates the– Used to synthesize other chemicals
• Tar contaminates the gas and must be cleaned for higher value
• Lower emissions than combustion
cleaned for higher value uses
• Char ash may be a ydisposal problem
PyrolysisPyrolysisPROSd
CONSi il h hi h• Can produce
hydrocarbon gases, liquids and a solid char
• Bio‐oils have a high moisture content and a complex mix of organicliquids, and a solid char
product (e.g. charcoal)• Solid char has
complex mix of organic chemicals and are not very compatible with Solid char has
properties similar to that of coal and can be
y pother fuel oils
• Markets for products used to co‐fire coal combustion units
are untested
• Relatively low costs
lEncouraging Biomass Utilization
1 Reduce handling and processing costs1. Reduce handling and processing costs2. Improve conventional technology3 I i ffi i3. Improve conversion efficiency4. Develop new processes5. Develop new products6. Develop new marketsp7. Educate public to benefits of
utilization
John Shelly, UC Berkeley Cooperative Extension
A Wood Scientist’s OpinionTrees for the most part grow without intensive cultivation and are moreintensive cultivation and are more adaptable to environmental changes than most plants They consume CO andmost plants. They consume CO2 and produce wood – a basic building block for many productsmany products.
The importance of woody biomass as a raw p f ymaterial will increase dramatically through the 21st century becoming the raw material y gof choice for many carbon‐based materials.
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