Biodegradation Performance of Cellulosic, Meltblown PLA and Spunbond PLA Mulches in Soil Treatments Used in Crops

Larry C. Wadsworth1 (lwadswor@utk.edu), Douglas G. Hayes2, Annette L. Wszelaki3, Jaehoon Lee2, Karen K. Leonas4 Jeffrey Martin3 Tommy L Washington5 C TylerLeonas4, Jeffrey Martin3,Tommy L. Washington5, C. Tyler Pannell2 and Galina Menlichenko2

1Materials Science & Engineering and Biosystems Engineering & Soil ScienceUniversity of Tennessee, Knoxville (UT)

2UT Biosystems Engineering and Soil Science Department3UT Pl t S i D t t3UT Plant Sciences Department4Washington State Univ. (WSU), Pullman, WA USA991645UT Materials Science & Engineering

“Plastic” Agricultural Mulches: Advantages

Reduced weed problems Enhanced moisture controlReduced evaporationReduced water saturation

Increased soil temperature extension of growing season increased growth rate increased growth rate

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

“Plastic” Agricultural Mulches: Disadvantages

Costly and laborious to remove

Potential environmental hazard Black plastic (polyethylene) does not biodegrade or

compostable Its persistence in the ecosystem can increase local

pesticide and toxicant concentrations

Greater initial costs Greater initial costs

Increased management of irrigation

Increased soil erosion (between strips of mulch) Increased soil erosion (between strips of mulch)

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

Goals for Biodegradable Mulches in AgricultureCurrent UIFA-SCRI Project: Oct 1, 2009-Sep 30 , 2012

To assess agricultural, ecological, and economic consequences of using biodegradable mulches in protected (High Tunnel) and Open Field specialty crop production systems Open Field specialty crop production systems.

To test Poly(Lactic Acid)- [PLA-]Based Nonwovens (spunbondO

and meltblown) as mulch prototypes.

To test PLA and commercial “biodegradable” mulches for their

O

O

n To test PLA and commercial biodegradable mulches for their

performance in growing tomatoes under High Tunnel and open field conditions at 3 different US sites .. in a controlled study

Provide data that may be useful for developing a standard for biodegradation of mulches .. (“inherent biodegradation” of g ( gcompostable plastics, ASTM D 6400 / D5988, is not robust)

Sites for Investigation Washington State University, Mount Vernon and Pullman

Campuses

Texas A&M / Texas Tech University, Lubbock, TX

University of Tennessee, Knoxville, TN

2

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 crops g g p y p

production systems: plant physiology, weeds, pests, & diseases

Outreach to specialty crop grower / organic farming community

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

Economics WG (WSU, TTU) Assess the economic impact of biodegradable mulches in high tunnels & its Assess the economic impact of biodegradable mulches in high tunnels & its

impact on sustainability: life cycle assessment.

Sociology WG (WSU, UTK) Better understand the needs and concerns of the specialty crops grower / Better understand the needs and concerns of the specialty crops grower /

organic farming community

Key Scientific Advisors and StakeholdersJ h D John Dorgan, Site Director, Colorado Center for Biofuels and Biorefining (C2B2), Department of Chemical Engineering; Colorado School of Mines, g g; ,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 Robert Green, NatureWorks LLC, 402 Sir Walker Lane, Cary, NC

Terry Phillips, Mark Williams, BioBag USA, Palm y p , , g ,Harbor, FL

Several members of the Specialty Crops Grower / O i F i C i f WA TX d TNOrganic Farming Community of WA, TX, and TN

High Tunnel and Field Studies of Biodegradable Mulches for Specialty Crops

Mulches BioBag (Starch-Based), Palm Harbor, FL

Bi T l (St h B d) D b i A i ti W t f d O t i BioTelo, (Starch-Based), Dubois Agrinovation, Waterford, Ontario

Spunbond PLA PLA donated by NatureWorks, Blair NE; made at Saxon Textile Institute, Germany, white, 90 g m-2

Black Plastic Polyethylene, Pliant Corp, Schaumburg., IL

Control (no mulch)

C ll l C t l “W dG dPl ” S Shi P C LLC Cellulose Control, “WeedGuardPlus,” SunShine Paper Company, LLC, Denver, CO, 107 g m-2

Conditions Mulches laid 12 ft long, 2 ft wide and 5 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, etc.

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 inexpensively

High Tunnels at WSU-Mt. Vernon

High Tunnels at Univ. Tennessee

Greenhouse Studies of BDMsGreenhouse Studies of BDMs 3 Mulches (SB-PLA, MB-PLA,

Cellulose)Cellulose)

3 Soil Treatments (Manure, Lime, Control)

2 Durations (10 wk, 29 wk)

3 Replicates

Mulches Buried 2 cm below surface of soilof soil

Soil from a certified organic farm

1.0 L of Water per tray per 48 h p y pperiod

Performance of PLA Nonwoven Mulches: Greenhouse Studies SB PLA 14 8 ± 0 8Greenhouse Studies Spunbond PLA (SP-PLA)M = 132 000; PDI = 1 5

SB-PLA: 14.8 ± 0.8 m

Mn 132,000; PDI 1.5

Meltblown PLA (MB-PLA)Mn = 111,000, PDI = 1.5

Cellulosic Mulch

Cellulose: 20 8 ± 8 1 m MB-PLA: 6.3 ± 2.3 mCellulose: 20.8 ± 8.1 m MB PLA: 6.3 ± 2.3 m

Degradation of MB-PLA Mulches: Lime Treatment

10 weeks| 29 Weeks

Properties of Cellulosic Mulch which Nearly Disappeared after 10 Weeks in All Soil TreatmentsDisappeared after 10 Weeks in All Soil Treatments

Measurement Method 0 wk

Mass, g m-2 ASTM D3776

110.27 ± 4.66

Thickness, mm ASTM D1777

0.254 ± 0.007

Air Permeability, cm3 s 2

ASTM D737

0.72 ± 0.28cm-2 D737

Breaking Load ASTM D4632

50.54 ± 21.29

Breaking Elongation ASTM D5035

3.88 ± 0.44

Mn, kDa GPC Not Determined

Degradation of MB-PLA Mulch after 10 Weeksg

Measurement Method 0 wk 10 wk, Control

10 wk, Lime

10 wkManure

Mass, g m-2 ASTM D3776

82.89 ±7.69

97.71 ±7.57

96.66 ±9.72

101.56 ±9.08

Thickness, mm ASTM D1777

0.460 ±0.028

0.666 ±0.109

0.679 ±0.111

0.674 ±0.093

Air Permeability, cm3 s ASTM 35.2 ± 3.1 56.2 ± 14.4 Not Tested Not Testedcm-2 D737

Breaking Load ASTM D4632

5.23 ± 2.65 2.05 ± 1.26 0.88 ± 0.51 1.07 ± 0.76D4632

Breaking Elongation ASTM D5035

6.71 ± 4.30 4.16 ± 3.20 3.82 ± 1.96 4.26 ± 2.88

Degradation of SB-PLA Mulch after 10 Weeksg

Measurement Method 0 wk 10 wk, Control

10 wk, Lime

29 wk Manure

Mass, g m-2 ASTM D3776

91.06 ±2.84

112.87 ±3.26

108.50 ±5.80

108.47 ±3.58

Thickness, mm ASTM D1777

0.657 ±0.015

0.814 ±0.057

0.814 ±0.066

0.891 ±0.078

Air Permeability, cm3 s ASTM 96.2 ± 5.31 83.4 ± 6.58 90.1 ± 9.11 89.3 ± 6.93cm-2 D737

Breaking Load ASTM D4632

9.00 ± 1.38 10.25 ±0.90

10.05 ±1.00

9.68 ± 1.25D4632 0.90 1.00

Breaking Elongation ASTM D5035

11.13 ±1.06

11.05 ±0.82

10.77 ±1.42

11.24 ±1.29

Degradation of SB-PLA Mulch after 29 Weeksg

Measurement Method 0 wk 29 wk, Control

29 wk, Lime

29 wkManure

Mass, g m-2 ASTM D3776

91.06 ±2.84

Thickness, mm ASTM D1777

0.657 ±0.013

0.872 ±0.093

0.914 ±0.087

0.892 ±0.087

Air Permeability, cm3 s ASTM 96.2 ± 5.31 75.49 ± 75.44 ± 67.36 ±cm-2 D737 8.99 7.42 10.77

Breaking Load ASTM D4632

9.00 ± 1.38 2.25 ± 0.27 2.13 ± 0.32 2.24 ± 0.27D4632

Breaking Elongation ASTM D5035

11.13 ±1.06

9.25 ± 1.26 8.41 ± 2.58 9.39 ± 1.47

Summary

Cellulose control nearly disappeared after 10 wksMB PLA, as shown by physical strength testing

had appreciable degradation after 10 weeks in the l li d d il b h d h control, lime and manure treated soil but had the

greatest degradation in lime, followed by the manure compostmanure compost.

SB PLA did not have any loss in physical strength after 10 weeks but had appreciable strength loss after 10 weeks but had appreciable strength loss after 29 weeks in the control, lime and manure treated soil.

AcknowledgmentsDebra Inglis and Carol Miles (Project Directors)1;

C t B A d C bi A E i l A d d K L T M h d T W lt 1Curt Beus, Andrew Corbin, Ana Espinola‐Arredondo, Karen Leonas, Tom Marsh and Tom Walters1; Doug Hayes, Bobby Jones, Jaehoon Lee, Larry Wadsworth and Annette Wszelaki2; 

Eric Belasco and Jennifer Moore‐Kucera3; Russ Wallace4; and, Marian Brodhagen5

NatureWorks (PLA Donation)Saxon Textile Institute (Germany)

Biax Fiberfilm (WI USA)D Willi Kli (UTK)Dr. William Klingeman (UTK) 

Phil Flanagan (UTK) 

1 2 3 4 5

SCRI‐SREP Grant Award 

No. 2009‐02484