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Sprayable Biodegradable Polymer Membrane Technology forCropping Systems: Challenges and Opportunities
Vilim Filipovic,́ * Keith L. Bristow, Lana Filipovic,́ Yusong Wang, Henry Y. Sintim, Markus Flury,and Jirí̌ Š imůnek

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recycling technologies and replacing nonbiodegradable plastics
with biodegradable products.
For agricultural-use plastics, a promising alternative toconventional plastic is the development of “biodegradable”
mulch materials.4 These biodegradable mulch materials canretain similar physical and mechanical properties of theirconventional plastic counterparts, while being biodegradable
into carbon dioxide, methane, water, and microbial biomass.
Work is ongoing to improve their mechanical andbiodegradation properties while minimizing production costs
so that they can compete with cheaper plastic products.
However, there is a lack of long-term ﬁeld studies understanding the impact of biodegradable plastics on soil
ecosystems, biodegradation, and fragmentation pathways, andthe fate of plastic degradation products in the environment.4
Researchers have recently turned their attention to develop asprayable biodegradable polymer membrane (SBPM) technology5 (Figure 1), and this innovative approach of spraying
continuous polymer coatings rather than laying prefabricatedmulch ﬁlms is starting to raise attention among scientists andagricultural producers. Sprayable polymer membranes can beformulated using renewable and biodegradable raw materials,
such as polysaccharide polymers, natural polymers (e.g.,seaweed), protein polymers, polyethylene glycols, polysiloxane,polyurethane, and acrylic polymers.5 Eﬀorts also exist toproduce biodegradable sprayable polymers out of naturalproducts (e.g., sugar cane, wood-cellulose microﬁbers, lignin,gum, and leather). The use of recyclable, biodegradable natural
materials in polymer fabrication can be part of a sustainableholistic approach, which addresses not only the problem ofplastic pollution but also the problem of waste disposal.
Sprayable biodegradable plastic mulches adhere to the soil
surface with no headspace between the soil and the polymer
membrane.5 They may degrade more eﬃciently because they
are tightly bound with soil particles while having weakerlinkages between the polymer molecules compared tohe use of conventional plastic mulch ﬁlms in cropping
systems plays a major role in specialty crop production.
Plastic mulch improves soil microclimate, helps to conserve
soil moisture, and suppresses weed growth.1 However, themajority of plastic mulch ﬁlms commonly used are notbiodegradable and have to be removed after each growing
season. In China, the largest user of plastic mulch ﬁlms, morethan 184 × 105 ha of agricultural soil is covered annually withplastic ﬁlms, amounting to a total mass of around 14.7 × 105 tof plastic waste for disposal.2 Remnants of plastic mulches also
remain in soil, leading to plastic pollution of agricultural landand possibly entering the food chain or water systems.
Recycling of used plastic mulch ﬁlms is often hampered bysoil particles adhering to the plastics.
Greater public awareness of the extent of the global plastic
pollution problem and its ecological and societal impacts is oneof the main driving forces behind current policy changes
related to plastics use. Europe’s policy to ban single-use plastic
and to recycle at least 55% of plastic packaging by 2030 isleading the way, while the U.S. is introducing new plastic
recycling requirements for manufacturers.3 Additional ways toaddress the issue include the development of innovativeT© 2020 American Chemical Society

Received: February 13, 2020
Published: April 9, 2020

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Figure 1. A schematic of sprayable biodegradable polymer membrane (SBPM) technology indicating its properties, performance, and comparison
with conventional plastic mulch ﬁlms. The lower right-hand photo shows an application of SBPM in a tomato ﬁeld experiment near Echuca,
Victoria, Australia.

preformed biodegradable plastic mulch ﬁlms. Spraying
methodology is also commonly used by agricultural producers
to apply nutrients and pesticides, which makes this technology
easily implementable into existing cropping systems. TheSBPM can be sprayed onto the soil surface using hand-held
sprayers for smaller applications (rural plots), or large
mechanized sprayers can be used for large scale industrial
farming. Early results with SBPM under both controlled andﬁeld conditions indicate increased water-use eﬃciency andreduced weed growth compared to bare soils while
demonstrating agronomic performance comparable withcommercial low-density polyethylene mulch ﬁlms.5,6Maintaining the right mechanical properties of thebiodegradable polymer is also important alongside the primaryaims of sprayability, biodegradability, and nontoxicity. Ongoingwork focuses on discovering and ﬁne-tuning the right polymer
formulation, producing mechanical properties capable ofsustaining ﬁrm elastic binding with soil particles and durability
throughout the crop growing season. The addition of carbon
black as black pigment and absorbent of photosynthetically
active radiation (PAR) results in suppressing weed growth andincreasing soil temperature,5 with similar beneﬁcial eﬀects asconventional plastic mulch ﬁlms. Viscosity modiﬁers canprevent rapid adsorption (e.g., wicking) into the soil due toreduced viscosity, as wicking may result in poor membrane
formation and inconsistencies in membrane thickness,weakening water barrier properties.7 The SBPM technology
can be further adapted to implement novel add-ons intopolymer membrane, like those enabling bidirectional watertransfer, a slow release of fertilizers and nutrients, or control

over biodegradation time. Biodegradation by microorganisms
was found to be variable among various polymer types, ranging
from few months in the greenhouse up to one year in theﬁeld.5,6 SBPM developed by CSIRO group (Australia)
achieved 70% biodegradation in the ﬁeld during seven monthsof testing, showing no phytotoxicity or ecotoxicity. Additional
microbial diversity analysis indicated no drastic shifts inpopulation after the application of SBPM technology, that is,
no toxic eﬀects on soil microbial population was found.5,7Therefore, the SBPM degradation process appears highly
dependent on polymer properties and soil environmental andclimatic conditions, and it may diﬀer substantially from case tocase.
In summary, the future of the SBPM technology depends on
its ability to perform as well as prefabricated plastic andbiodegradable mulch ﬁlms which are currently in use, while
also reducing the production cost. The scientiﬁc community
will need to test various biodegradable polymer formulations inlong-term ﬁeld trials under diﬀerent climatic conditions todeﬁne to what extent the SBPM technology can compete withplastic mulch ﬁlms for agricultural performance. Further, littleis known about the long-term impact of biodegradable
mulches, such as SBPM, on soil health and ecosystem services,
so long-term ﬁeld assessments are needed.8 The biodegradable
SPBM technology with a simple modus operandi is apromising solution to replace vast amounts of plastics inagriculture and prevent pollution of soil and water systems,
while still supporting food production to keep pace with theperpetually growing global demands.
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AUTHOR INFORMATION

Corresponding Author

Vilim Filipović − CSIRO, Townsville, QLD 4814, Australia;
University of Zagreb Faculty of Agriculture, Department of SoilAmelioration, 10000 Zagreb, Croatia; orcid.org/00000001-9733-6720; Phone: +385 1 2393 711;
Email: vﬁlipovic@agr.hrAuthors

Keith L. Bristow − CSIRO, Townsville, QLD 4814, Australia
Lana Filipović − University of Zagreb Faculty of Agriculture,
Department of Soil Amelioration, 10000 Zagreb, Croatia
Yusong Wang − CSIRO, Townsville, QLD 4814, Australia
Henry Y. Sintim − Department of Crop and Soil Sciences,
University of Georgia, Tifton, Georgia 31793, United States
Markus Flury − Department of Crop & Soil Sciences,
Washington State University, Puyallup, Washington 98371,
United States; orcid.org/0000-0002-3344-3962
Jiří Šimůnek − Department of Environmental Sciences,
University of California Riverside, Riverside, California 92521,
United States

Complete contact information is available at:https://pubs.acs.org/10.1021/acs.est.0c00909
Notes

The authors declare no competing ﬁnancial interest.

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(2) Gao, H.; Yan, C.; Liu, Q.; Ding, W.; Chen, B.; Li, Z. Effects ofplastic mulching and plastic residue on agricultural production: ameta-analysis. Sci. Total Environ. 2019, 651, 484−492.
(3) Scott, A. Pressured plastics firms will look to recycling. C&EN
Global Enterprise 2020, 98 (2), 31−31.
(4) Sintim, H. Y.; Flury, M. Is Biodegradable Plastic Mulch theSolution to Agriculture’s Plastic Problem? Environ. Sci. Technol. 2017,51 (3), 1068−1069.
(5) Adhikari, R.; Bristow, K. L.; Casey, P. S.; Freischmidt, G.;
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(6) Sartore, L.; Schettini, E.; de Palma, L.; Brunetti, G.; Cocozza, C.;
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(8) Sintim, H. Y.; Bandopadhyay, S.; English, M. E.; Bary, A. I.;
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