Bio-based plastics: Steps towards a sustainable industry

Sarah Lott | May 06, 2013

As an undergraduate, I became increasingly interested in the environmental issues surrounding the modern agriculture system – a system dominated by mono-cropping of cereal crops (namely corn) that require heavy inputs of chemicals and water.

The overproduction of cereal and sugar crops has led to their use beyond the food industry to fuels, chemicals and, more recently, plastics. While this shift away from petrochemical feedstocks sounded good, I questioned whether the increasing load on the agricultural system for biobased materials would promote sustainability or exacerbate the land use issues surrounding modern agriculture.

As a Pharos Project researcher, I’ve noticed more manufacturers using biobased claims and incorporating bio-based polymers into their products.

The bio-plastics market has largely focused on biodegradable polymers such as poly-lactic acid (PLA) and polyhydroxyalkanoate (PHA) for food packaging and food service applications. However, the market is shifting towards bio-based drop-in replacements of petrochemicals to manufacture commodity plastics such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) – all of which can be produced, in some part, from bio-ethanol-derived ethylene. These plastics, commonly used in building materials, together make up almost 90% of plastics produced globally. [1]

Commodity plastics using bio-based feedstocks are now on the market. Brazilian manufacturer Braskem has been producing bio-polyethylene since 2010, and bio-polypropylene from Braskem and so-called bio-PVC from Solvay aren’t far behind.

This surge in bio-chemicals and bio-polymers led me to further research how sustainable these bio-based plastics really are and what companies are doing to overcome the lifecycle issues surrounding modern agriculture and plastics. 

What does it mean to be sustainable?

European Bioplastics, an industry organization, defines bioplastics simply as biobased - being at least partially derived from biomass, biodegradable, or both. While the prefix, “bio,” might feel good, it is hardly a guarantee that these plastics as a whole are in any way sustainable, in terms of chemistry or land use.

For one, some plastics have inherently toxic lifecycles, regardless of the source of the original feedstock. PVC is one. As Jennifer Atlee wrote last year, “Getting the polymer from a biobased source merely sugarcoats PVC without addressing the fundamental problem.” Mike Belliveau seconded that sentiment in a February article: “To make PVC, the poison plastic, add two carcinogens, pump the resin full of toxic additives and leave a trail of chlorinated waste from production and disposal. Replacing the petroleum in PVC with renewable carbon hardly greens its lifecycle.”

In order to promote a holistic and sustainable vision of the bioplastics industry, the Sustainable Biomaterials Collaborative (SBC) published Guidelines for Sustainable Bioplastics in 2009. [2] Under these guidelines, to be “sustainable” requires inclusion of “issues of environment, health, and social and economic justice, as well as material resource sustainability across the entire life cycle (from the production of their feedstocks to the management of the bioplastic product after its intended use).” This includes designing bio-plastics that meet the 12 principles of green chemistry and avoiding plastics like PVC, polystyrene (PS), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), and polyurethane (PU) which all require toxic chemicals in their manufacture.

Sustainable Feedstock Sourcing

Substituting petrochemical feedstock with agricultural feedstock produced through industrial agriculture brings in a host of new land use and other environmental issues to the plastics lifecycle. Monoculture agricultural practices routinely require heavy use of fossil fuels, toxic pesticides, chemical fertilizers and water causing soil erosion, loss of biodiversity, and indirect land use changes, all of which can have negative implications for the surrounding environment and communities. 

Increased demands on agriculture for chemicals have the potential to conflict with land requirements for food/feed and bio-fuels. However, it is estimated that only 7% of global arable land (100 million hectares) will be required to substitute all 250 million tonnes of petro-plastics with bio-plastics, while bio-fuels are estimated to require 250 million hectares and, therefore, would have a much greater impact on the food system than biopolymers. [3]

Land use requirements for biochemicals, as well as biofuels, may be further dimished by the transition to lignocellulosic feedstocks such as crop wastes (e.g. corn stover or sugar cane bagasse) or switchgrass.

According to the BREW study on biochemical production, biochemicals from lignocellulosic feedstock verses sugar feedstocks (e.g. corn and sugar cane) could reduce land use requirements by 60%. [4] Based on data from this study, if lignocellulosic ethanol was used rather than corn ethanol to produce bio-polyethylene at a global scale we would avoid the use of 21.2 million hectares of farmland – an area almost as large as the state I live in, Kansas. [5]

At current production levels and with the potential for reduced land use requirements from lignocellulosic feedstocks, land use for biopolymer feedstock may be small and manageable. However, without more sustainable production practices, the use of toxic chemicals and environmental degradation through agriculture still remain a major issue for bio-based materials.

European Bioplastics has stated that “the bioplastics industry is fully aware that the sustainable sourcing of its feedstock supply is a prerequisite for more sustainable products.” Additionally, some bio-based chemical manufacturers have individually stepped up to take a harder look at sustainability. Marc Verbruggen, CEO of PLA manufacturer NatureWorks said last year, "Addressing concerns over feedstock sustainability is important for the future because renewably sourced materials will be the only alternative to fossil-based materials for plastics production… Therefore, assuring sustainable land use is a fundamental requirement for this new technology."

But how can consumers know whether manufacturers are taking practical and certifiable steps to increase the sustainability of bio-plastics?

Fortunately, some good third-party certifications for sustainable feedstock sourcing exist. Two exemplary certifications are the International Sustainability and Carbon Certification (ISCC)’s “ISCC Plus” certificate and the Institute for Agriculture and Trade Policy’s Working Landscapes Certificate (WLC) program. Both certificates have feedstock production standards which address biodiversity conservation, soil and water conservation, limiting and phasing out chemical usage, and safe and healthy working conditions. ISCC-Plus certification is achieved by companies who work with the ISCC to trace the chain of custody of the feedstock from field to market. On the other hand, WLCs work like renewable energy certificates: farmers work directly with the IATC to follow sustainable production practices and Green Harvest Technologies (GHC) – who founded and developed the WLC program along with the IATC – sells the certificates as sustainable agriculture offsets.

Major bio-plastic producers have already obtained these certifications. Braskem has obtained ISCC-Plus certification for its bio-polyethylene in addition to generating a code of conduct for their ethanol suppliers which also addresses biodiversity, good environmental practices, and human rights. NatureWorks obtained ISCC-Plus and WLC certification for some of their PLA products sold in Germany by Danone.

Bio-plastics may not be a universal remedy, but the good news is that some big companies are taking bold steps to ensure that these land use and social and environmental health considerations are front and center. For building owners and occupants, this means we can demand more sustainable plastics that pose few inherent toxicity concerns and are produced using sustainably sourced feedstocks.

We have to challenge the idea that contamination is just the price of living in the modern world. Our bodies don't have systems to process plastics or flame retardants or pesticides. If contamination is the price of modern society, modern society has failed us. -- Russell Libby, Organic Farmer, Campaigner for Pollution Free Local Food Economies, 1956 - 2012


Footnotes

[1] Sagel, Esteban. Polyethylene Global Overview. PEMEX and IHS. Mexico City, Mexico. June 2012. Presentation. Accessed April 2013

[2] SBC is a coalition of NGOs, academia, businesses and government dedicated to the development of an economy based on sustainable biomaterials.

[3] Singer, Stephan, ed. The Energy Report. World Wildlife Fund. January 2011, p 61. Downloadable from http://worldwildlife.org/publications/the-energy-report.

[4] “If starch is used as basis for fermentable sugar, the total land use ranges from 1.0 to 38.2 million ha in the three scenarios. If lignocelluloses is used as biofeedstock, only 0.4 to 15.6 million ha are needed.” (Patel, M.; Crank, M.; Dornburg, V.; Hermann, B.; Roes, L.; Hüsing, B.; Overbeek, van, L.;Terragni, F.; Recchia, E.: Medium and long-term opportunities and risks of thebiotechnological production of bulk chemicals from renewable resources - The BREW Project. September 2006, p 309. Downloadable from http://brew.geo.uu.nl/)

[5] Ethylene from lignocellulosic feedstock would require 0.19 hectare (ha)/ton (t), but 0.47 ha/t if from corn feedstock. (Patel et. al. 2006) p 182, Table 3-7, part 2; Ratio of bio-ethylene to bio-polyethylene is approx. 1:1 “About 11700 kton ethylene are needed for the production of 11300 kton polyethylene.” (Patel et. al. 2006) p 219, Table 4-6; Polyethylene production totaled 76 million metric tones in 2011.  (Sagel 2012); Area of Kansas is 213,096 sq km (21.3096 million hectares).