Poly(Lactic Acid)-Based Biodegradable Mulches for...

Poly(Lactic Acid)-Based Biodegradable Mulches for “Green” Agriculture

Douglas G. Hayes

Department of Biosystems Engineering and Soil Science,University of TennesseeKnoxville, TN USA [email protected]

Nanjing Agricultural University, Nov 111

Douglas G. Hayes

• Professor of Biosystems Engineering, University of Tennessee

• Internationally recognized scientist with over 25 years experience

• Co-authored and produced 50 articles and 13 book chapters

• Editor of Biobased Surfactants and Detergents - Synthesis, Properties, and Applications published by AOCS press

• Serves on editorial board of Journal of the American Oil Chemists’ Society, Journal of Surfactants and Detergents, and Biological Engineering Transactions

• Research Areas:

• Biobased products produced via biocatalysis

• Complex fluids / soft colloids for protein purification and biocatalysis

• Biobased degradable agricultural mulches


Outline1. Introduction, Goals, and Approaches

2. Soil burial / greenhouse studies

3. Performance assessment in high tunnel and open field studies

4. Weatherometry and biodegradability testing

5. Conclusions


Plastic Agricultural Mulches: Advantages

Reduced weed problems Enhanced moisture control Increased soil temperature extension of growing season increased plant growth rate

Reduced soil compaction Reduced fertilizer leaching Cleaner product Root pruning eliminated http://www.ces.ncsu.edu/depts/hort/hil/hil-33.html


“Plastic” Agricultural Mulches: Disadvantages

Costly and laborious to remove ($600 per acre) Potential environmental hazard Black plastic (polyethylene) is not biodegradable or

compostable Its persistence in the ecosystem can increase local

pesticide and toxicant concentrations Greater initial costs More intensive irrigation management Increased soil erosion (between strips of mulch)

http://www.ces.ncsu.edu/depts/hort/hil/hil-33.html


Goals for Biodegradable Mulches in AgricultureCurrent NIFA-SCRI Project: Oct 1, 2009 – Sept 30, 2012 To assess agricultural, ecological, and economic

consequences of using biodegradable mulches in protected (High Tunnel, or HT) and Open Field (OF) specialty crop production systems.

To test Poly(Lactic Acid)- [PLA-] based nonwovens (Spunbond and Meltblown) as mulch prototypes.

To test PLA and commercial “biodegradable” mulches for their performance in growing tomatoes under HT and OF conditions at 3 different US sites .. in a controlled study

Provide data that may be useful for developing a standard for biodegradation of mulches

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Sites for Investigation Washington State University, Mount Vernon and

Pullman Campuses Texas A&M / Texas Tech University, Lubbock, TX University of Tennessee, Knoxville, TN


SCRI Interdisciplinary Research Team

Materials Working Group, “WG” (UTK, WSU)Design new biodegradable mulches from PLA and

its biopolymer blends via nonwovens textile technology

Physico-Chemical Testing

Crops WG (WSU, UTK, TAMU/TTU)Assess use of biodegradable mulches in high

tunnels for specialty crop production systems: plant physiology, weeds, pests, and diseases

Outreach to specialty crop growers/ organic farming community


SCRI Interdisciplinary Research Team

Soils WG (WSU, UTK, TAMU)Assess the impact of biodegradable mulches on

soil ecosystem

Economics WG (WSU, TTU)Assess the economic impact of using

biodegradable mulches in high tunnels

Sociology WG (WSU, UTK)Better understand the needs and concerns of the

specialty crops growers / organic farming community,

Discover and address the barriers hindering increased use of biodegradable mulches and high tunnels Nanjing Agricultural University, Nov 119

Why PLA-Based Nonwovens as Mulches?

PLA: Biobased, commercially available, reasonably priced, compostable & biodegradable

PLA: monomer is a common metabolite

Nonwovens: high strength, low weight

Nonwovens: small fiber size Increased rate of hydrolysis

Nonwovens can be made inexpensivelyNanjing Agricultural University, Nov 1110

Ultimate Goal

Prepare a biobased agricultural mulch .. that will perform well for specialty crop cultivation .. that would undergo slow deterioration during the

cultivation season (~March – October) .. that would be tilled into the soil at the end of the

cultivation season (~November) .. and would be completely mineralized by the

beginning of the next cultivation season (March) Alternate Goal: ..would not undergo fragmentation during the

cultivation season .. would be easily retrieved from the soil at the end

of the growing season .. then would be composted


Nonwovens Textiles

(Wikipedia) “fabric-like material made from long fibres, bonded together by chemical, mechanical, heat or solvent treatment”

“manufactured sheet, web or bat of directionally or randomly oriented fibers, bonded by friction, and/or cohesion and/or adhesion” (http://web.utk.edu/~mse/Textiles/)

Not woven or knitted; not paper-based Examples: Medical surgical gowns; HEPA air

filters, disposable clothing


Nonwovens Textiles: Spunbond (SB)

Thermoplastic polymers are melted;

extruded through spinnerets; fibers are cooled and

collected on a conveyer beltNanjing Agricultural University, Nov 1113 http://web.utk.edu/~mse/Textiles/

Nonwovens Textiles: Meltblown (MB)

Low viscosity polymers are melted and extruded from a spinneret;

A stream of high velocity hot air disperses and solidifies the extruded polymer

Nanjing Agricultural University, Nov 1114http://web.utk.edu/~mse/Textiles/

Assessment Tools1. Soil burial studies in greenhouse experiments

2. Utilization of mulches for cultivation of vegetables in high tunnel and open field studies

3. Weatherometry and biodegradability testing


Outline1. Introduction, Goals, and Approaches2. Soil burial / greenhouse studies3. Performance assessment in high tunnel and open field studies4. Weatherometry and biodegradability testing5. Conclusions

Key Participants S. Dharmalingham, T. Washington, T. Pannell, Prof. Doug

Hayes, Prof. Larry Wadsworth, UTK J. Martin, Prof. Annette Wszelaki, UTK R. Raley, Prof. Jaehoon Lee, UTK


Greenhouse Study I (UTK) 3 Mulches “Spunbond” = SB-PLA-2010-white “Meltblown” = MB-PLA-2010-white, Cellulosic (WeedGuardPlus)

3 Soil treatments (manure, lime, control)

2 Durations (10 wk, 29 wk) 3 Replicates

Mulches buried 2 cm below the soil surface

Soil from a certified organic farm 1.0 L of water per tray per 48 h

period

Nanjing Agricultural University, Nov 1117 Wadsworth et al, submitted (2011)

PLA Nonwoven Mulches (SEM Micrographs)

Molecular Weight: SP-PLA-2010: Mn =

132,000; PDI = 1.5MB-PLA-2010: Mn =

111,000, PDI = 1.5


Cellulose: 20.8 ± 8.1 m

SB-PLA: 14.8 ± 0.8 m

MB-PLA: 6.3 ± 2.3 m

Wadsworth et al, submitted (2011)

10 weeks

Greenhouse Study IDeterioration of MB-PLA-10 Mulch: Lime Treatment


29 weeksWadsworth et al, submitted (2011)

Evidence of Deterioration for MB-PLA-2010 Mulch:SEM Analysis (Greenhouse Study I)

Lime soil treatment29 weeks exposure

Nanjing Agricultural University, Nov 1120 Wadsworth et al, submitted (2011)

Deterioration of MB-PLA-10 Mulch (Greenhouse Study I)

Measurement Method 0 wk 10 wk, Control

10 wk, Lime

Mass, g m-2 ASTM D3776 82.58 ± 8.35 97.71 ± 7.57 96.66 ± 9.72

Thickness, mm ASTM D1777 0.435 ± 0.020 0.666 ± 0.109 0.679 ± 0.111

Air Permeability, cm3 s cm-2 ASTM D737 37.0 ± 2.1 56.2 ± 17.4 Not Tested

Breaking Load, N ASTM D4632 6.87 ± 3.26 2.05 ± 1.26 0.88 ± 0.51

Breaking Elongation ASTM D5035 5.98 ± 3.67 4.16 ± 3.20 3.82 ± 1.96

Mn, kDa GPC 93.5 ± 0.620 111± 8 112 ± 5

Nanjing Agricultural University, Nov 1121Wadsworth et al, submitted (2011)

Greenhouse Study II: Effect of Moisture Level


Mulch and Treatment Breaking Load, gSB-PLA-11, as received 4190 ± 148

High Moisture 3820 ± 315Low Moisture 4200 ± 145

MB-100% PLA-11, as received 1820 ± 299High Moisture 639 ± 168Low Moisture 587 ± 222

MB 75% PLA/25% PHB-11 513. ± 252High Moisture 89.4 ± 45.8Low Moisture 70.0 ± 36.7

• Low and High Moisture: 1.0 L and 0.5 L per tray per 48 h, respectively• Soil from organic farm with compost added• Burial in soil for 10 wk• 3 replicates

Outline1. Introduction, Goals, and Approaches2. Soil burial / greenhouse studies3. Performance assessment in high tunnel and open

field studies4. Weatherometry and biodegradability testing5. Conclusions

Key Participants Profs. Debra Inglis and Carol Miles, and their groups (WSU, NW

REC, Mount Vernon, WA USA) Prof. Russell Wallace’s group (Texas AgriLife REC, Lubbock,

TX USA) J. Martin, Prof. Annette Wszelaki, UTK Prof. Karen Leonas and her group; Prof. Doug Hayes and his

group


High Tunnel and Open Field Studies in TN, TX, and WA: Mulches (2010)

BioBag (Starch-Based), Palm Harbor, FL BioTelo, (Starch-Based), Dubois Agrinovation,

Waterford, Ontario SB-PLA-2010-white, PLA donated by NatureWorks,

Blair NE USA; made at Saxon Textile Institute (STFI), Germany, white, 90 g m-2

Black Plastic Polyethylene, Pliant Corp, Schaumburg, IL

Cellulose Control, “WeedGuardPlus,” SunShinePaper Company, LLC, Denver, CO USA, 107 g m-2

Control (no mulch)Nanjing Agricultural University, Nov 1124

Mulches for High Tunnel and Open Field Studies


High Tunnel and Open Field Studies in TN, TX, and WA (2010): Methods and Conditions

Mulches laid 14 ft long, 2-3 ft wide and 5-6 ft apart in high tunnels or open fields

Tomatoes planted: ~April – September, 2010 Irrigated: 1 inch of water per week Continuous monitoring of soil & air temperature,

moisture, pests & diseases, etc. Several different physical and chemical test

conducted on retrieved mulches


High Tunnels at WSU-Mount Vernon



High Tunnels at Univ. Tennessee

Maximum Load – Machine Direction for Mulches as Received


High Tunnel and Open Field Studies (2010): Decrease of MW

Biobag BioTelo

SB-PLA

Greatest loss of MW occurs for High Tunnel, TN (thus far)

Loss of MW: Biobag > Biotelo >


Comparison of Locations/Environment

Percent of Maximum Load at Time 3

Open Field High Tunnel Nanjing Agricultural University, Nov 1131

Comparison of Open Field & High Tunnel

Percent of Maximum Load at Time 3


Comparison of Open Field & High TunnelPercent of Maximum Elongation

0

50

100

150

200

250

TN TX WA TN TX WA TN TX WA TN TX WA TN TX WA TN TX WA TN TX WA TN TX WA TN TX WA TN TX WA

BioBag BioTelo Cellulose Non-BDM SB PLA BioBag BioTelo Cellulose Non-BDM SB PLA

FIELD HT

Perc

enta

ge o

f Tim

e 0

Elon

gati

on (

%)

Time 1

Time 2

Time 3


Outline1. Introduction, Goals, and Approaches2. Soil burial / greenhouse studies3. Performance assessment in high tunnel and open field studies4. Weatherometry and biodegradability testing5. Conclusions

Key Participants1. Dr. Elodie Hablot, Prof. Ramani Naryan, and his

group, Michigan State Univ, East Lansing, MI USA2. S. Dharmalingham, Drs. Doug Hayes and Larry

Wadsworth, UTK


Biodegradability and Weatherometry Four mulches investigated

Spunbond PLA 2010 – white Spunbond PLA 2010 – black Meltblown PLA 2010 (white) Meltblown 75% PLA / 25% polyhydroxyalkanoate (PHA)

All mulches treated by weatherometry Ci4000 Xenon Weather-Ometer, Standard = ASTM G155-05a Exposure Cycle: 102 min light at 63°C; 18 min light and water

spray Exposure time: 21 d (504 h) Irradiance: 0.35 W m-2 nm-1

Wavelength: 340 nm All mulches analyzed for biodegradability (ASTM D5833), before

and after weatherometry treatment


Biodegradability and Weatherometry

Photodegradation of PLA: Norrish II mechanism of carbonyl polyester (Ikada E. , J Photopolym Sci Technol 1997:10(2):265-270.


Preliminary Results: Weatherometry(GPC Analysis)

2-fold decrease of Mn for all mulches; polydispersityindex increases


SB-PLA-black

SB-PLA-white MB PLA MB-PLA+PHA

Mn (g/mol)

0 day 39000 44000 44000 3100021 days 17928 18430 20701 14045Mn 0d/Mn 21 d 2.18 2.39 2.13 2.21

Mw (g/mol)

0 day 52000 56000 56000 4300021 days 42299 46834 48309 32451Mw 0d/Mw 21 d 1.23 1.20 1.16 1.33

PDI0 day 1.33 1.27 1.27 1.3921 days 2.36 2.54 2.33 2.31PDI 0 d/PDI 21 d 0.56 0.50 0.54 0.60

Preliminary Results: Weatherometry(GPC Analysis)


10000

20000

30000

40000

50000

60000

0 5 10 15 20 25Ageing (days)

Mn

(g/m

ol)

BSBWSBMB PLAPLA/PHB

Preliminary Results: Weatherometry(Differential Scanning Calorimetry, DSC)

For all 100% PLA nonwovens, two melting peaks occurred after ageing different type and/or size of crystalline zones

From lowest to highest degradation): MB PLA > SB-PLA-2011-black > SB-PLA-2011-white > MB PLA/PHA


Mulch Tg (°C) Tm (°C) ∆Hm (J/g)SB-PLA-black – Day 0 62 168 51.9SB-PLA-black – Day 21 59 (-5%) 150 / 159 (-10%/-5%) 38.0 (-27%)SB-PLA-white – Day 0 62 169 45.8SB-PLA-white – Day 21 60 (-3%) 155 / 162 (-8%/-4%) 39.2 (-14%)

MB PLA – Day 0 62 168 47.6MB PLA – Day 21 57 (-8%) 146 / 154 (-13%/-8%) 33.6 (-29%)

MB - PLA/PHB – Day 0 41 140 / 166 0.8 / 43.2MB - PLA/PHB – Day 21 40 (-2%) 142 / 164 (+1%/-1%) 0.6 / 44.4 (-25%/+3%)

Preliminary Results: Weatherometry(Differential Scanning Calorimetry, DSC)


61.51°C(I)

58.83°C

62.26°C

102.11°C

92.95°C29.54J/g

167.90°C

162.58°C47.56J/g

56.69°C(I)53.73°C

58.02°C

112.50°C

102.84°C32.41J/g

153.87°C

148.19°C33.60J/g

146.17°C

-2.0

-1.5

-1.0

-0.5

0.0

0.5

Hea

t Flo

w (W

/g)

0 50 100 150 200 250

Temperature (°C)

MBPLA-0d.001––––––– MBPLA-21d.001–––––––

Exo Up Universal V4.3A TA Instruments

Preliminary Results: Weatherometry (FTIR) (SB-PLA-2010-black)


Preliminary Results: Weatherometry (FTIR) (SB-PLA-2010-black)


0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

1900210023002500270029003100330035003700Wavenumber (cm-1)

Abs

orba

nce

Day 0Day 21

Hydroperoxidesand alcohols

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

1900210023002500270029003100330035003700Wavenumber (cm-1)

Abs

orba

nce

Day 0Day 21

Hydroperoxidesand alcohols

Summary Greenhouse Studies MB-PLA-10 in the presence of lime shows the

greatest extent of deterioration Mechanical strength: breaking load; elongation, SEM no significant change of MW

Long-Term High Tunnel & Open Field Studies Loss of mechanical strength greater for mulches used in the open field as compared to

high tunnels No universal trend based on mulch type and location


43

Ongoing Research Greenhouse Studies Focus upon moisture level, use of enzymes, new

PLA/poly(hydroxyalkanoate nonwovens (lower MW)

High Tunnel & Open Field Studies New Spunbond PLA mulch; Year 2 study is ongoing

Biodegradability and Weatherometry All mulches underwent deterioration via

weatherometry; biodegradability testing is ongoing


44

Biodegradable Mulches for Specialty Crops Produced Under Protective Covers

Debra Inglis and Carol Miles (Project Directors)1;Andrew Corbin, Ana Espinola‐Arredondo, Annabel Kirschner, Karen Leonas, Tom Marsh and Tom Walters1;

Doug Hayes, Bobby Jones, Jaehoon Lee, Larry Wadsworth and Annette Wszelaki2; Jennifer Moore‐Kucera3; Russ Wallace4; Marion Brodhagen5 ; and Eric Belasco6;

NatureWorks (PLA Donation)Saxon Textile Institute (Germany)

Biax Fiberfilm (WI USA)Dr. William Klingeman (UTK)

Phil Flanagan (UTK)

1 25

SCRI Grant Award No. 2009-51181-05897

43 6


Back-Up Slides


Key Scientific Advisors and Stakeholders John Dorgan, Site Director, Colorado Center for

Biofuels and Biorefining (C2B2), Department of Chemical Engineering; Colorado School of Mines, Golden, CO

Ramani Narayan, Department of Chemical Engineering and Materials Science; Michigan State University, 2527 Engineering Building, East Lansing, MI

Robert Green, NatureWorks LLC, 402 Sir Walker Lane, Cary, NC

Terry Phillips, Mark Williams, BioBag USA, Palm Harbor, FL

Several members of the Specialty Crops Growers / Organic Farming Community of TN, TX, and WA


Comparison of Locations/Environment

Percent of Maximum Elongation at Time 3

Open Field High Tunnel Nanjing Agricultural University, Nov 1148

Comparison of Open Field & High Tunnel

Percent of Maximum Elongation at Time 3


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