Fabricating Biodegradable Mulches Douglas G. Hayes 1 , Larry C. Wadsworth 1 , and Karen K. Leonas 2 1 Department of Biosystems Engineering and Soil Science, University of Tennessee Knoxville, TN USA 37996-4531 2 Department of Apparel, Merchandising, Design & Textiles, Washington State University Pullman, WA 99164-2020, [email protected]ASHS Conference, 31 July 2012 1
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Fabricating Biodegradable Mulches
Douglas G. Hayes
1, Larry C. Wadsworth 1, and Karen K. Leonas 2
1
Department of Biosystems Engineering and Soil Science,University of TennesseeKnoxville, TN USA 37996-45312
Department of Apparel, Merchandising, Design & Textiles, Washington State UniversityPullman, WA 99164-2020,
Commercially Available Polymers and Blends Employed in Biodegradable Agricultural Mulches
Green = Biobased
PBAT (Ecoflex®)
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Mechanical properties similar to PE (high flexibility, good impact strength, and good melt processability)
Biodegradable under composting environments (55-58 oC)
Readily forms composites with cellulose, polysaccharides, PLA, and PHA
Field trials: mulches performed similarly to PE mulches: weed control and crop yield; slighly higher soil temperature (Ngouajio, et al., HortTechnol. 2008, 18, 605-610)
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,”
SunShine Paper Company, LLC, Denver, CO USA, 107 g m-2
Control
(no mulch)ASHS Conference, 31 July 201223
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High Tunnels at Univ. Tennessee
Maximum Load –
Machine Direction for Mulches as Received
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Comparison of Locations/Environment
Percent of Maximum Load at Time 3
Open Field High Tunnel ASHS Conference, 31 July 201226
Biodegradability and Weatherometry
Photodegradation of PLA: Norrish II mechanism of carbonyl polyester (Ikada E. , J Photopolym Sci Technol 1997:10(2):265-
270.
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Weatherometry Treatment
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Summary
Conventional polyethylene mulches: the environmental fate at end-of-life is a major concern
Commercially available biodegradable mulches:
Many perform well (mechanical strength, biodegradability under specific conditions); but:
Are they applicable to all cultivation systems, climates, and soil types?
Are they truly environmentally benign under all circumstances?
Can they meet organic agriculture certifications?
Have they been sufficiently tested in large-scale agriculture to ensure environmental safety?
What will “third generation”
biodegradable mulches look like? (Can improved performance be commensurate with reduced cost?)
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29
Summary
Greenhouse Studies
Meltblown-PLA / PHA in the presence of lime and/or compost shows the greatest extent of deterioration
Spunbond-PLA: excellent properties for long-use compostable material
Long-Term High Tunnel & Open Field Studies
Loss of mechanical strength: most visible parameter for assessment of physico-chemical changes
No universal trend based on mulch type and location
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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)S. Dharmalingam , C. Tyler Pannel and R. Dunlap (UTK), Dr. William Klingeman, Phil Flanagan
1 25
SCRI Grant Award No. 2009-51181-05897
43 6
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Hayes et al, Biodegradable Agricultural Mulches Derived from Biopolymers, in Degradable Polymers and Materials, Principles and Practice, 2nd Edition (ACS Symposium Series), in press.
Back-Up Slides
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Important Definitions
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Biobased: “.. composed in whole or in significant part of biological products or renewable domestic agricultural materials (http://www.biobased.us/)
Compostable plastic: “.. undergoes degradation by biological processes during composting to yield carbon dioxide, water, inorganic compounds, and biomass .. leaves no visible, distinguishable, or toxic residue”
(ASTM D6400)
Biodegradable plastic: “..degradation (change in its chemical structure) resulting from the action of naturally occurring microorganisms such as bacteria, fungi, and algae”
Biobased: “.. composed in whole or in significant part of biological products or renewable domestic agricultural materials (http://www.biobased.us/)
Compostable plastic: “.. undergoes degradation by biological processes during composting to yield carbon dioxide, water, inorganic compounds, and biomass .. leaves no visible, distinguishable, or toxic residue”
(ASTM D6400)
Biodegradable plastic: “..degradation (change in its chemical structure) resulting from the action of naturally occurring microorganisms such as bacteria, fungi, and algae”
promotes and enhances biodiversity, biological cycles, and soil biological activity .
.based on minimal use of off-farm inputs and
on management practices that restore, maintain, or enhance ecological harmony”
(USDA-NOSB)
Synthetic Material:
“A substance that is formulated or manufactured by a chemical process
or by a process that chemically changes a substance .. from a naturally occurring plant, animal, or mineral sources..”
(USDA-NOSB)
Important Definitions
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Sustainable Agriculture:
“Integrated system of plant and animal production practices that will, over the long term:
satisfy human food and fiber needs;
enhance environmental quality and the natural resource base upon which the agricultural economy depends;
make the most efficient use of nonrenewable resources and on-farm resources ..
sustain the economic viability of farm operations;
and enhance the quality of life for farmers and society as a whole. “
(1990 USA Farm Bill)
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
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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
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Comparison of Locations/Environment
Percent of Maximum Elongation at Time 3
Open Field High Tunnel ASHS Conference, 31 July 201239
Comparison of Open Field & High Tunnel
Percent of Maximum Elongation at Time 3
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Goals for Biodegradable Mulches in Agriculture Current 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
O
O
n
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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
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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
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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 ASHS Conference, 31 July 201244
Nonwovens Textiles: Spunbond (SB)
Thermoplastic polymers are melted;
extruded through spinnerets;
fibers are cooled and collected on a conveyer belt
ASHS Conference, 31 July 201245 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
ASHS Conference, 31 July 201246http://web.utk.edu/~mse/Textiles/
PHA
Biobased; not “synthetic”
Readily available
60,000 tonnes per year
High cost
Readily biodegradable, including in soil
Highly crystalline thermoplastic polymer susceptible to embrittlement & thermal
degradation
Incompatible with several other polymers
Susceptible to loss of elongation at break due to ultraviolet radiation produced by the sun
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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
ASHS Conference, 31 July 201248 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
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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)
Greenhouse Study II: Effect of Moisture Level
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Mulch and Treatment Breaking Load, gSB-PLA-11, as received 4190 ±
148High Moisture 3820 ±
315Low Moisture 4200 ±
145MB-100% PLA-11, as received 1820 ±
299High Moisture 639 ±
168Low Moisture 587 ±
222MB 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
Mulches for High Tunnel and Open Field Studies
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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
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High Tunnels at WSU-Mount Vernon
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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 >
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Comparison of Open Field & High Tunnel
Percent of Maximum Load at Time 3
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Comparison of Open Field & High TunnelPercent of Maximum Elongation
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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 USA
2.
S. Dharmalingham, Drs. Doug Hayes and Larry Wadsworth, UTK
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Preliminary Results: Weatherometry (GPC Analysis)
2-fold decrease of Mn for all mulches; polydispersity index increases
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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