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

Why do we want to convert woody biomass?

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.