Renewable Hydrogen from Biomass Pyrolysis Aqueous · PDF fileRenewable Hydrogen from Biomass...

Renewable Hydrogen from Biomass Pyrolysis Aqueous Phase

Abhijeet P Borole (PI) 1

Ramesh Bhave1, Costas Tsouris1,2, Spyros Pavlostathis2, Sotira Yiacoumi2, Philip Ye3, Nikki Labbe3, Pyongchung Kim3, Jim Pollack4, Dan Westerheim5 1Oak Ridge National Laboratory 2Georgia Institute of Technology 3University of Tennessee 4OmniTech international 5FuelCellEtc, Inc. 6Pall Corporation May 30, 2014 CHASE Project Webinar

The slides from this presentation should not be distributed, forwarded or cited (where noted)

2 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name

Outline • Background

– Biomass pyrolysis process – Need for Hydrogen – Potential impact on efficiency of biofuel production – Potential impact on greenhouse gas emissions and sustainability

• Objectives • Project tasks • Team members • Microbial Electrolysis • Bio-oil production, oil-water separation, downstream

membrane separations, LCA analysis.


Fast pyrolysis-based biofuel production

Gasoline, diesel

Ref: Biomass Multi-year Program Plan


Fast Pyrolysis Process Flow Diagram

Biomass: C5H7O2N → gasoline (C8H18), diesel (C12H23)

Needs significant amount of hydrogen

Ref: Jones et al., Production of gasoline and diesel from biomass via fast pyrolysis, hydrotreating and hydrocracking: A design case.; PNNL-18284 Rev.1; Pacific Northwest National Laboratory: 2009


Hydrogen production from natural gas

• Natural gas – Steam-Reforming Reactions

Methane: CH4 + H2O (+ heat) → CO + 3H2

• Producer gas from pyrolysis – Water-Gas Shift Reaction

CO + H2O → CO2 + H2 (+ small amount of heat)

T = 700-1000°C P = 3-25 bar


Hydrogen Efficiency and Process yields

The energy content of the fuel product depends significantly on natural gas input (26-40% of energy input)

Energy balance 74% 26%

19% 31% 49%

51%

Biooil characterization Fuel product characterization

Carbon balance Energy balance

loss

Yield

Ref: Jones et al., Production of gasoline and diesel from biomass via fast pyrolysis, hydrotreating and hydrocracking: A design case.; PNNL-18284 Rev.1; Pacific Northwest National Laboratory: 2009

ORNL preliminary energy balance

Note: The data on this slide should not be distributed, forwarded or cited.


Other issues

• Problems – Stability of biooil (polar-non-polar separation over time) – Corrosivity due to acids (biooil pH = 2.8) – Biooil and fuel yield (biomass basis) – Loss of carbon to aqueous phase

Phenolic acids

Acetic acid CH3COOH

CHASE program: Carbon, hydrogen and separations efficiency improvement.


Microbial Electrolysis

Biomass

Electrons

Bio-oil Upgrading and

Hydrotreatment

Hydrocarbon fuels

Pyrolysis

Hydrogen

Oil phase

Aqueous Phase

Bio-oil

Schematic of the biomass to biofuel process with modifications to enable improvement in hydrogen efficiency

Project Outline

Note: The information on this slide should not be distributed, forwarded or cited.

http://www.best-home-alternative-energy.com/


Focus: Hydrogen

Is there an alternate way to meet the objectives without using natural gas? Oil stabilization Upgrading to gasoline/diesel fuels Reducing cost of hydrogen

Hydrogen production expenses: Capital costs: 28% for natural gas reformer Operating Expenses: 16% for natural gas Minimizing natural gas use has potential to minimize operating expenses, while meeting GHG emission goals to meet Renewable fuel standard (RFS).

Ref: Biomass Multi-year Program Plan


Project objectives

• Develop reforming process for efficient conversion of aqueous phase organics to hydrogen via microbial electrolysis.

• Develop energy-efficient methods to separate bio-oil aqueous phase, extract acidic and polar compounds from bio-oil for production of hydrogen.

• Demonstrate improvement in hydrogen efficiency via mass and energy balance.

• Demonstrate potential for reduction in life cycle greenhouse gas emissions via life-cycle analysis.

Address Technical Area 2: Hydrogen Efficiency, Subtopic: Reforming hydrogen from aqueous streams in biomass liquefaction.


Potential Impacts

• The proposed work will enable efficient conversion of the corrosive and polar, carbon-containing compounds in bio-oil aqueous phase to hydrogen.

• Potential to improve the stability of the bio-oil and reduce corrosivity.

• The implementation of MEC reforming and separation unit operations being developed in this study will enable improvements in hydrogen production and overall biomass to biofuel conversion efficiency while minimizing use of natural gas and thus reducing life cycle greenhouse gas emissions.

Microbial Electrolysis


Bioelectrochemical Conversion Technology

2 Borole, A. P., Reguera, G; Ringeisen, B.; Wang, Z-W; Feng, Y.; Kim, B H; l. (2011). "Electroactive biofilms: Current status and future research needs.“ Energy Environ. Sci. 4: 4813-4834.

Substrate

Product / Fuel /

Chemical Organic Carbon/ Reduced

substrate/ Waste

CO2 + H2O

Bio

cata

lytic

ano

de

Cat

hode

BioElectrochemical System (BES)

e- e-

H+

H+

H+

H+

CxHyOz → CO2 + H+ + e- MEC: H+ + e- → H2

Nutrients

Cell mass

Load/Power source

Reduction

Type of BES Cathode Product substrate MFC Oxygen Electricity MEC Protons Biohydrogen BES Acetate Ethanol/biofuel BES Oxygen Hydrogen peroxide BES Carbon dioxide Electrofuels BES other/sunlight Photo/biofuels

Proposed path: Bio-oil Aqueous Phase → electrons + protons in MEC (anode ) → BioH2 (cathode)


Microbial Electrolysis for converting aqueous phase generated during pyrolysis to hydrogen

• Pyrolysis derived aqueous phase – Potential for loss of carbon via aqueous phase – Emulsifies with oil phase – Makes bio-oil unstable (polar-non-polar separation over

time) – Makes bio-oil corrosivity due to acids (bio-oil pH = 2.8)

• Microbial electrolysis – Conversion of biooil aqueous organics to hydrogen – Anode: Conversion of degradable organics to electrons,

protons and CO2

– Cathode: Proton reduction to hydrogen at applied potential of 0.3-1V.

– Develop electroactive biofilms with tolerance to inhibitory and toxic molecules in biooil aqueous phase (furfural, HMF, phenolics, etc.)

H2

H+ Organic Carbon

CO2 + H2O

Bio

cata

lytic

ano

de

e- e-

CxHyOz → CO2 + H+ + e- H+ + e- → H2

Nutrients

Cell mass

Cat

hode

> 0.3 V

Cathode catalyst

H+

H+

H+

H+

MEC


Biological hydrogen production MEC vs. Existing Technologies

Borole, A. P. (2011). Biofuels, Bioproducts & Biorefining "Improving energy efficiency and enabling water recycle in biorefineries using bioelectrochemical cells." 5(1): 28-36.


Pyrolysis-derived water-soluble compounds

• Furfural

• Acetic acid

• Phenolics

• Vanillin

• Eugenol

• Acetol

• unknowns

Convert in MEC: e.g., Vanillin: C8H8O3 + 13H2O → 17H2 + 8CO2.

Biomass to fuels conversion reaction (with MEC reforming included): 30 CH2O (biomass) + 0 CH4 + 0 H2O + kW → C8H18 + C12H23 + 10 CO2 + 10 H2O (gasoline) (diesel)

Many of these molecules have not been tested in MEC previously


http://en.wikipedia.org/wiki/File:Vanillin2.svg

http://en.wikipedia.org/wiki/File:Eugenol_acsv.svg


H2

H+ Organic Carbon

CO2 + H2O

Bio

cata

lytic

ano

de

e- e-

CxHyOz → CO2 + H+ + e- H+ + e- → H2

Nutrients

Cell mass

Cat

hode

> 0.3 V

Cathode catalyst

H+

H+

H+

H+

Microbial Electrolysis Cell

Biology Microbiology Molecular Biology Biocatalysis

Engineering Chemical Engineering Electrochemical Engineering Environmental Engineering Life-cycle analysis

Electrochemistry Electrocatalysis Voltammetry Chronoamperometry Impedance spectroscopy

Materials chemistry Membrane materials Electrode materials Catalyst formulation

Analytical chemistry Bio-oil and aqueous phase analysis -Chromatography -Mass spectrometry -UV-Vis spectroscopy

Interdisciplinary Components


Handling toxic molecules in MFC/MEC • Typical substrates

– Hemicellulose byproducts - acetic acid (deacetylation).

– Sugar degradation products – furfural, hydroxymethylfurfural

– Lignin degradation products – phenolic aldehydes and ketones and acids.

• Investigate energy recovery from acidic molecules while managing toxic compounds present in biooil aqueous phase (mechanisms).

• Transformation of toxic molecules to non-toxic products without energy extraction

• Mineralization of recalcitrant and inhibitory byproducts 1

• Evaluate potential for water recycle

• Applicable to fermentation-derived biorefinery wastewater stream, enabling processing high biomass loading (> 20% solids) cellulosic biochemical conversion process with water recycle.

Borole, et.al., 2009, Biotechnol for Biofuels., Controlling accumulation of fermentation inhibitors in biorefinery process water using Microbial Fuel Cells, April 2009, 2, 1, 7.


Approach to bioanode development • Development of engineered bioanode systems for energy

recovery – To increase current density.

• Designed novel BES systems to achieve high coulombic efficiency and current density – Engineering parameter optimization.

• Enrichment of electroactive microbial catalysts for conversion of organic acids, sugars, etc to bioenergy – Biocatalyst development.

• Assessment of limitations in bioanode performance – Electrochemical Impedance Spectroscopy.

• Characterization of the microbial communities to understand the diversity of novel electrogenic organisms.

– Microbial diversity of exoelectrogens

Borole, A. P. (2010). Microbial fuel cell with improved anode, US Patent 7,695,834. USA, UT-Battelle. US Patent 7,695,834.

Borole et.al., 2009, J. Power Sources, 191(2): 520-527..

75 µm

MFC-A (day 113)

0% 11%

0%

10%

0%

8%

25%

42%

4%

MFC-A (day 126)

0%18%

1%

27%

2%4%

26%

19%

3%

MFC-A (day 136)0%

20%

0%

29%

0%2%

40%

7%

2%MFC-B (day 162)

2%

54%

0%11%

9%

11%

7%

0%

1%

5%

21 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name 21

Conversion of furan aldehydes and phenolic molecules in bioanode

– Demonstrated potential of bioanode to remove furfurals, phenolics, organic acids, and sugar derivatives in model aqueous streams3.

– Examine effect of concentration of toxic/ inhibitory molecules at representative concentrations (acetate 10 g/L, 2-furfural, HMF, phenolics: 1-4 g/L) • No detrimental effect on current production

– Near complete removal of the substrates – Coulombic efficiency up to 64% – Current density : up to 10 A/m2 (3700

mW/m2 power density)

Borole, et.al., 2009, Biotechnol for Biofuels., Controlling accumulation of fermentation inhibitors in biorefinery process water using Microbial Fuel Cells, April 2009, 2, 1, 7.

0

200

400

600

800

1000

-1.0 1.0 3.0 5.0 7.0Pow

er d

ensi

ty, m

W m

-2

Current density, A m-2

0.1 g/L 2-furfural2 g/L 2-furfural0.2 g/L acetate5 g/L acetate10 g/L acetate

0

500

1000

1500

2000

2500

3000

3500

4000

0 5 10 15

mW

m-2

A m-2

Furfural5-HMF4-HB


Electroactive Biocatalyst Characterization • Biofilm sample from bioanode developed for model substrate mixtures

(furfural, HMF, 3 phenolic compounds, acetic acid, ) • 16S rRNA analysis

14%

19%

9%

50%

6% 2%

Alphaproteobacteria

BetaproteobacteriaRhodocyclaceaeBetaproteobacteriaBurkholderiaceaeDeltaproteobacteriaDesulfovibrioGammaproteobacteria

Firmicutes Anaerofilum

http://www.biotechnologyforbiofuels.com/about/access/


Developing high performance MECs

Process/ Operating parameters

Biological parameters

Electroactive Biofilm Optimization

1. Batch vs. flow system

2. External resistance

3. Redox potential 4. Shear rate / liquid

flow rate 5. pH 6. Substrate loading 7. Temperature 8. Aerobic vs.

anaerobic 9. Ionic strength

1. Electrode spacing 2. Presence of

membrane and type of membrane

3. Relative anode:cathode surface area

4. Electrode surface area to volume ratio

5. Electrode properties: conductivity, hydrophilicity, porosity, etc.

6. Type of cathode (oxygen diffusion)

1. Source of inoculum 2. Pure culture vs. consortium

3. Gram-positive vs. Gram-negative Biofilm parameters (Dependent variables)

1. Biofilm growth rate 2. Specific rate of electron transfer 3. Ability to synthesize redox-active mediators 4. Ability to grow nanowires and perform DET

System design parameters

5. Relative exoelectrogen population 6. Characteristics of EPS layer 7. Extent of substrate mineralization 8. Substrate specificity Borole AP, Reguera G, Ringeisen B, Wang Z, Feng Y, Kim, BH, 2011, Energy Environ. Sci. (Review paper)

Electroactive Biofilms: Current Status and Future Research Needs, 4:4813-4834


Stability of maximum current production

Current density increased first 30 days, thereafter, it remained ~ 35 A/m2 for 20 days, but not without fluctuations. Coulombic efficiency ranged from 50-80% (for fermentative substrates glucose + lactate)

Current prouction (-0.2V vs Ag/AgCl)

0

10

20

30

40

50

0 10 20 30 40 50 60

days

mA

/cm

2

Current production

A/m

2



Biooil aqueous phase analysis

Bio-oil aqueous phase characterization via HPLC


1 Presented by: Spyros G. Pavlostathis and Xiaofei Zeng

Renewable Hydrogen Production from Pyrolysis Aqueous Phase Task II: Reforming of Aqueous Phase to Hydrogen using MEC

• Objective: Assess the biotransformation extent of specific model compounds in anodic biofilms and their contribution to hydrogen production

H2

MEC

Biofuels

Hydrogenation

Oil Phase

Aqueous Phase

Page 1


• Experimental Setup

Page 2


A MFC maintained as stock culture to provide inoculum for MECs

MFC

Furan Compounds

Phenolic Compounds

Model Compounds MEC


• Results

Page 3


Time (d)0 10 20 30 40 50 80 90 100

Curr

ent

Den

sity

(m

A/cm

2 )

0.00

0.05

0.10

0.15

0.20

0.25

0.30

500250100100

Resistance (Ω):

Time (d)70 75 80 85 90 95 100 105

H2

Prod

uctio

n (m

L/L

anod

e)0

50

100

150

200

250

300

350

Cycle

16 17 18

Sol

uble

CO

D (m

g/L)

0

100

200

300

400InitialFinal

Cycle

16 17 18

Met

abol

ites

Abun

danc

e (m

UA*

s)

0

1000

2000

3000

4000

P18-210P24-210

On-going Work

1. Startup of MEC 2. Bioconversion of furan

and phenolic compounds in separate MFCs

3. Biotransformation pathways of model compounds



Potential application in bioconversion-based biorefinery

Estimated Energy production Electricity production = 2.5 MW (MFC) or 7000 m3/hr H2 (MEC) ~ 25% of total power needs for a biorefinery targeting 70 millions gallons ethanol/year.

Borole, A. P. US Patent, (2012). Microbial fuel cell treatment of ethanol fermentation process water, UT-Battelle, LLC. Borole AP, Mielenz J, Intl J Hydrogen Energy, 2011, Estimating Hydrogen Production Potential in Biorefineries Using Microbial Electrolysis Cell Technology, 36, 14787–14795.

Mixing

Overliming followed

by pH adjustment

S/L Separation

Distillation

Fermentation

Saccharification

Further product purification

Cell Production

S/L Separation

Treated recycle water

Liquid

Solids Treated recycle

water

Enzyme

Nutrients

Process water

Bottoms (with solids)

Bioalcohol

Recycle water

Solids

Liquid

To Boiler Dilution water

MFC / MEC

Recirculating dilution water El

ectr

icity

/ H

ydro

gen

Pretreatment Biomass

Enable water recycle

H2

H+ Organic Carbon/ Inhibitor molecules

CO2 + H2O

Bioc

atal

ytic

ano

de

e- e-

CxHyOz → CO2 + H+ + e- H+ + e- → H2

Nutrients

Cell mass

Cath

ode

> 0.3 V

Cathode catalyst

H+

H+

H+

H+


10.7 % Distillation Bottoms

Stover feedstock

Pretreatment and

Conditioning (1)

Hydrolyzate Distillation and Dehydration (3)

Evaporation (4)

Ethanol

Burner / Boiler (5)

Electricity (8)

Water Treatment / Recycle (7)

Blowdown

Methane And

Sludge Pretreatment Flush

Cooling Tower

(6)

Evaporator Heat (via

water), 11.7%

Proc/Cond Heat, 0.7% Ferm. Heat, 0.6% Distillation Heat, 8.6%

Boiler Heat, 2.7 %

WWT Heat, 0.6 % Syrup (18.8%)

Solid Residue (36.6%)

110%

Ferm. broth

110%

Ambient Heat,

CW Evaporation

Flue gas,

22.4%

7.6%

14.7% 0.6% 1.3%

8 %

67.5% Energy In, 100%

HP Steam 9 % 3.2%

Process

Make-up water 88.5%

Water in 7%

Water in 3%

Saccharification Fermentation

(2)

Enzyme

Water losses, 99% (including evaporator, cooling tower and boiler)

LP Steam

48.7%

4.8%

Legend

Green ovals indicate percent water content of the process stream in the flowsheet

Teal boxes show energy content of each stream as percent of total energy in (i.e., biomass) throughout the process

Yellow shapes indicate energy/water loss from the existing process stream, which can be minimized using MECs.

Product streams showing energy content as fraction of total energy in (Biomass) in the process reported by NREL Heat loss paths in the process reported by NREL

7.4%

Potential for improvement in energy efficiency and ability to recycle water using MECs.

Borole AP, Biofuels, Bioproducts & Biorefining, Improving Energy Efficiency and Enabling Water Recycle in Biorefineries Using Bioelectrochemical Cells. 5(1):28-36 (2011).


Projected mature biorefinery scenarios

AFEX pretreatment +

Consolidated bioprocessing

Biomass

Ammonia Ethanol

Solid residue

Gasification Gas cleanup H2S, CO2 separation

FT Synthesis

Separation/Refining

Power Island

MEC

FT liquids

Export electricity

Process steam and electricity

Treated water Hydrogen

Aqueous stream after solids removal

AFEX pretreatment +

Consolidated bioprocessing

Biomass

Ammonia Ethanol

Solid residue

Gasification Gas cleanup H2S, CO2 separation

FT Synthesis

Separation/Refining POX

Power Island

WWT

FT liquids

Export electricity

Process steam and electricity

Unconverted syngas

Biogas Treated water

Aqueous stream after solids removal

Borole AP, Biofuels, Bioproducts & Biorefining, Improving energy efficiency and enabling water recycle in biorefineries using bioelectrochemical cells., 5(1):28-36 (2011).

Laser, et al., 2009, Biofuels, Bioproducts & Biorefining


MEC Scale-up issues

• Study by J. Keller and group

• Low power output

• Engineering vs. Biocatalyst issues at pilot-scale

• Low coulombic efficiency – Presence of dissolved oxygen – Growth of unwanted (aerobic) biofilms

• MEC scale up – 1000L – 7.4 A/m3, 0.19 L/L-day H2. – 86% methane in product

Borole, AP; US Patent 7,695,834, April 2010. Microbial fuel cell with improved anode.

Bio-oil production and aqueous phase bio-oil separation for MEC experiments from switchgrass using pyrolysis unit at UTK CRC

Bio-oil production by pilot auger pyrolysis reactor at UTK CRC

• Source: switch grass particle size: less than 2mm • Feeding rate: 10kg/hr • Reaction temperature: 500°C and 550°C • Bio-oil yield: 40-50wt%, biochar: 25-30wt%,

gas:20-25wt% • The bio-oil is combined by three condensers

Aqueous phase bio-oil separation

• Water: oil: 4:1 • Vigorous shaking • Standing for overnight at

4°C • Centrifugation:

5000rpm/min for 30min Fractions of bio-oil (wt% of crude bio-oil) after separation

Pilot auger pyrolysis reactor at UTK CRC

36.7%

5.5%

35.1%

22.6%

water in crude bio-oil to aqueous phasewater in crude bio-oil to organic phasechemicals to aqueous phasechemicals to oganic phase

Fractions of crude bio-oil (wt%) before separation

42.27%

55.68%

1.74% 0.31%

Water Chemicals Solids Ash


Characterization of crude and aqueous phase bio-oil Properties of crude and aqueous phase bio-oil

Properties Crude bio-oil Aqueous phase bio-oil

Water content (wt%) 42.27±0.66 91.72±1.03

Total solid (wt%) 1.74±0.25 Not detected

pH value 2.84±0.07 3.02±0.01

Density (g/ml) 1.13±0.001 1.01±0.004

Ash (wt%) 0.31±0.04 0.085±0.004 Viscosity at 40 °C

centistokes (cSt) 6.5±0.82 0.75±0.01

TAN, mg KOH/g 137.39±2.96 30.13±1.28

Major chemicals identification and quantification in aqueous phase bio-oil

Aqueous phase

Chemicals extracted by organic solvent

Organic solvent extraction

GC/MS

chemicals identification chemicals Quantification

Aqueous phase

GC HPLC

Most volatiles: Aldehydes, ketones, lignin

Acids and sugars


Removal of Water from Bio-oil Liquid-Liquid Extraction of Bio-oil Components

Investigators: Sotira Yiacoumi and Costas Tsouris Ph.D. Student: Kyoung Eun (Lydia) Park

School of Civil and Environmental Engineering Georgia Institute of Technology

Aqueous Solution

Organic Solvent

Aqueous Extraction of Bio-oil with the Centrifugal Contactor

Options for Solvent Extraction of Bio-oil

Aqueous Phase Organic Phase

MEC for H2 production Fuel

Extraction Options

Sequential Extraction

Simultaneous Extraction

Extraction Parameters: Solvent type, pH, ionic strength, volume ratio, etc.

Volume ratio 1:1 4:1

NaCl (Ionic strength) (M) 0.001 0.01 0.1 1

Microbial growth media (phosphate buffer) DI ¼ ½ 1

‒ Bio-oil contains a significant fraction of water and water-soluble species ‒ The water to bio-oil volume ratio and ionic strength affect the extraction of bio-oil species

Measurements: Partitioning, pH, conductivity, chemical composition

Batch experiments to determine range of parameters:

Aqueous solutions after extraction


1 Managed by UT-Battelle for the Department of Energy

Membrane Separations-Objectives • Removal of cellular debris in the MEC effluent.

• Evaluate impact of carryover oil, fines and contaminants in recycle water on downstream processes.

• Produce clean water for recycle to aqueous phase.

• Feed volumes from microbial reactor: <1L -10L

• Identify and develop process parameters using hollow fiber and tubular ceramic membranes- hydrophobic (PVDF) and hydrophilic (PAN) and zirconia.

• Flux stability over time, membrane fouling, back pulsing and membrane regeneration.

• Process optimization, integration, reliability and scalability.

• Obtain engineering data for scale-up and assess energy requirements.

2 Managed by UT-Battelle for the Department of Energy

Verification of water flux for Pall membranes


Life Cycle Assessment Defined

Cradle-to-Grave Product System Boundary

Raw material and energy consumption

Emissions to air, water and soils

RawMaterial

RawMaterial

ProductionProduction UseUse End of LifeEnd of Life

Simplified Mass Balance

Process or

Operation

Product(s)

Liquid waste

Sewer/Floor Drains

Chemicals

Process Aids

Cleaning Agents

Emissions (Internal/External)

Raw Materials

Balance sheet of environmental inflows and outflows

Sample list

Life Cycle Inventory

Sample Life Cycle Impact Assessment Calculation

Global Warming Potential

Corresponding characterization

factors

GWP equiv. factor LCI Result LCIA Result

Carbon dioxide 1 2000 2000Methane 21 15 315Nitrous Oxide 310 0.1 31

Total Potential GWP (CO2-eq) --> 2346

-60

-40

-20

0

20

40

60

80

100

120

Petro PolyolImpact ScoreEquals 100%

Assessing Environmental Performanceof Soy vs. Petroleum Polyols

Petro Polyol Soy Polyol

Sample Comparative Results

Renewable Hydrogen from Biomass Pyrolysis Aqueous · PDF fileRenewable Hydrogen from Biomass...

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