Grantee Research Project Results

2013 Progress Report: Developing Alternatives to Plastic Mulch

EPA Grant Number: SU835348
Title: Developing Alternatives to Plastic Mulch
Investigators: Santelmann, Mary , Cassidy, James , Chen, Hsiou-Lien , Rochefort, Skip , Cluver, Brigitte , DiFrancesco, Kara , Selko, Tucker , DeGeorge, Dustin , Clark, Caitlin , Doniger, Alison , Nelson, Veronica , Walker, Stephanie , Ingram, Mark
Current Investigators: Santelmann, Mary , Cassidy, James , Chen, Hsiou-Lien , Cluver, Brigitte , Rochefort, Skip , Ingram, Mark , DiFrancesco, Kara , Livingston, Grant , Doniger, Alison , Selko, Tucker , Brennan, Sarah , Walker, Stephanie , Plesa, Florin , DeGeorge, Dustin , Clark, Caitlin , Rabe, Samuel
Institution: Oregon State University
EPA Project Officer: Hahn, Intaek
Phase: II
Project Period: August 15, 2012 through August 14, 2014 (Extended to August 14, 2015)
Project Period Covered by this Report: August 15, 2012 through August 14,2013
Project Amount: $90,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2012) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Awards , Sustainable and Healthy Communities

Objective:

Every year farmers around the globe lay plastic mulch over 300 million acres of fields in an effort to suppress weeds, retain soil moisture, regulate temperature or other purposes which ultimately increase crop production and farm income. However, the plastic mulch produces a plethora of deleterious environmental and human health impacts during its lifecycle. Due to limited disposal and recycling options, this plastic accumulates in landfills or is burned, releasing pollutants into the air. Unrecovered debris pollutes the landscape and can endanger livestock and aquatic organisms. In addition to the pollution generated by the use of plastic mulch, its manufacture consumes energy and materials while providing only short-term utility—usually less than a year. Currently available alternatives to plastic mulch have not gained widespread acceptance due to their high cost, uncertain performance, and low availability. Despite these serious consequences, the widespread use of plastic in agriculture has been largely overlooked by the public. In our P3 project, we aim to:  develop a biodegradable mulch product that has the attributes desired by end-users (people), is cost-effective (prosperity), and results in less waste and more efficient use of resources (the planet). All steps of this endeavor include efforts to inform the public of the negative impacts of plastic use in agriculture and to engage farmers in developing a solution to this problem.   

The overarching objective of our P3 project is to raise awareness of the environmental and human health threats posed by the use of plastics in agriculture, while working to decrease agricultural plastic use through the development of a biodegradable alternative to plastic mulch.

In Phase I, we achieved the objectives of:  (1) raising awareness of pollution associated with the production, use and disposal of plastic mulch, (2) testing promising alternative materials that are already on the market, and (3) working with farmers and industry partners to begin development of a biodegradable, sustainable alternative to plastic mulch. 

In Phase II, we are building upon our prior work to accomplish the following goals:

• Goal 1 – develop and test a sustainable mulch prototype made from flax;
• Goal 2 – gather data on the performances of alternative mulches, and;
• Goal 3 – conduct a life cycle analysis of alternative mulch products. 

To achieve our first goal, we partnered with the company Naturally Advanced to produce a mulch prototype derived from flax shive using sodium alginate as a binding agent. We are currently testing the prototype alongside other mulches to assess how well it performs in water retention, soil heat insulation, pest control, soil health and crop production. During the 2013-14 academic year, we will conduct a life cycle analysis on the mulches tested in the field trial to see how they relate in terms of water use and carbon emissions throughout their lifetimes. 

Progress Summary:

In summer 2012, we field tested a loose flax shive product that could simply be spread in agricultural rows. Using loose shive as a mulch requires minimal processing, potentially making it an economical way to produce a mulch from flax or a similar raw material. However, initial field trials indicate that 5 cm thick layers of loose shive performed poorly compared to sheeted mulch products, particularly in terms of weed suppression in the Willamette Valley, Oregon field trials. In addition, mulch did not provide significant yield improvements of potatoes over the control in field trials conducted by one of the graduate students working in drier regions of eastern Oregon and western Idaho with the Malheur, Oregon Agricultural Experiment Station. We thus determined that loose much would not adequately meet most farmers’ needs, leading us to the task of developing a new sheeted mulch product. We are currently field testing a newly-developed sheeted mulch product made from flax shive and sodium alginate.

In this task, we aimed to create a shive-based sheeted alternative to the plastic mulch, which would be relatively light, easier to use than loose shive mulch, but more effective in weed suppression, moisture retention and soil temperature regulation, leading to improved crop yields. Undergraduate P3 student team members used a sodium alginate binding agent to develop a sheeted mulch from shive, achieving one of our anticipated outputs. 

The bulk of the experiments conducted in Winter 2013 involved formulating an appropriate concentrate of sodium alginate binding solution and determining an appropriate ratio of flax shive to binding solution. Dry tensile strength, wet tensile strength, chemical composition, and decomposition time of various films were recorded. Reducing the amount of sodium alginate used was important when considering future production costs. Agricultural wastes (like flax shive) are relatively inexpensive and were not a limiting factor in our film design. A 1.5% by weight solution of sodium alginate was eventually used in the final product. We also tested different flax/solution mixtures, finding that both 20% and 22% concentrations by weight of flax shive met our design criteria.  

Sixteen, 0.76 m x 0.76 m squares of prototype flax sheets were developed for the Summer 2013 field trials in Corvallis, OR . Half of the sheets (8) developed for field testing were composed of 20% by weight flax, and the other half were composed of 22% by weight flax. All 16 prototype sheets were bound together with a 1.5% by weight sodium alginate solution. 

The most notable departure from the original object of the project is the scale of production. Because of the size and weight of these flax sheets, they are not likely to compete with PLA (Polylactic acid, a biodegradable plastic) for use on a large scale farm. Though costs are potentially very low, this mulch will likely be better suited for small farm or home use. A major benefit of this film product, along with its biodegradability, is its potential to be customized per region. For example, in the Willamette Valley, grass straw waste would be a suitable alternative for flax, reducing carbon costs embedded in transportation. 

Whether our new mulch product will produce the desired outcome to provide farmers with an economically viable, environmentally sustainable mulch and create a market for flax is yet to be determined. We are currently conducting field trials, described below, to assess whether the developed sheeted mulch product meets farmers needs and enhances yield. Further research for this project is possible and would be valuable to pursue. There are possibilities for considering other agricultural waste products, various binders, and other plant nutrient additives. Other delivery mechanisms for the mulch could be developed, such as rolls or sprays.   

We are currently running field trials of five different mulch types, in addition to a bare earth control:  WeedGuard Plus, Biotelo, perforated green polyethylene, and the two different formulations of our experimental sheeted flax shive prototype using a randomized split-plot design, planted with common Willamette Valley summer crops, tomatoes and bell peppers. We are collecting performance data on:  plant yield, weed retention, soil moisture, soil temperature, and soil health (soil respiration and mesofaunal composition).  We will also observe biodegradability of the mulches in the field following final harvest.

We anticipate completing harvests from the field trials by the end of September, and initial data analysis by the end of November. Preliminary analysis of yield data from weekly harvests indicates that our prototype 22% shive mulch may produce the highest yields (136 kg, significantly higher than the control). All mulches are performing well in weed suppression. 

Of note, elemental analysis of the shive mulch revealed that the sodium concentration of this mulch approximately four times the amount in orchard leaf standards. We hypothesize this is a result of the sodium alginate binding agent leaching into the soil.  This could be a problem when the films are used year after year. Potassium alginate or another binder that contains plant nutrients may serve as a better option in the future.

The life cycle analysis (LCA) will be completed in the second year of the project (academic year 2013-14). Now that we have produced a mulch of our own, we can begin to compare the energy and water used in production of this mulch with those of commercially available products. Undergraduate team members will conduct a pilot LCA of black plastic and is working with the graduate student team to develop the methodology for further LCA of the shive products in comparison to plastic. 

Over the course of two growing seasons we have collected substantial data on how different mulch types perform, an anticipated project output. We are working to determine the best way to disseminate this data, in order to achieve the outcome of providing farmers the opportunity to compare performance of different mulches in side-by-side field trials. 

Future Activities:

Plastic mulch sheeting poses several sustainability challenges over its lifecycle, primarily resulting from the production of plastic and the lack of environmentally and economically viable disposal options for this non-biodegradable product. Introducing a sustainable mulch to the agricultural market that is economically competitive to a plastic mulch will decrease the prevalence of plastic in agriculture and improve the long-term sustainability of this important sector. More specifically, our developed alternative shive product could provide the following quantifiable sustainability benefits:  (1) decrease solid waste production, (2) eliminate toxins released by open burning of plastic mulch, (3) eliminate contaminants leached from used plastic mulch, (4) shift from non-renewable to renewable raw materials for production, (5) as well as eliminate plastic pollution on the landscape, which poses a danger to livestock and wildlife from ingestion of remnant plastic fragments. In addition, we are continually working to bridge the gap between academia, industry, and farmers and to inform the public about the sustainability challenges posed by plastic mulch. 

Our P3 project is on schedule to produce the anticipated output / outcomes within the scheduled funding periods, without cost overruns. We are well on our way to completing Goals 1 and 2, namely to develop a sustainable mulch prototype made from flax and gather data on the performances of our prototype and commercially available mulches. In the upcoming academic year we will primarily dedicate our efforts completing the life cycle analysis (Goal 3) and completing an analysis of our field trial findings for dissemination to the public and agricultural communities.

Journal Articles:

No journal articles submitted with this report: View all 4 publications for this project

Supplemental Keywords:

Plasticulture, mulch, soil health

Progress and Final Reports:

Original Abstract

2014 Progress Report

Final Report

P3 Phase I:

Developing Sustainable Alternatives to Plastic Mulch  | Final Report