Investigating The Greenness Of Biobased Products
Investigating The Greenness Of Biobased Products
Interest in the use of agricultural products and wastes for energy and industrial materials is growing throughout the world. One path could lead to a new system of production that will produce a virtuous cycle of benefits for the environment and society. It would envision a return to renewable raw materials in lieu of feedstocks and fuels based on petrochemicals. Advocates of this vision predict a reduction in demand for fossil fuels, a decrease in greenhouse gas emissions, as well as the mitigation of a host of other environmental threats. An alternative path for the bioeconomy also exists, which foresees the increased use of synthetic fertilizers, a related reduction in water quality, and an increase in soil erosion and greenhouse gas emissions. This disparity in expectations points to the need for careful and wide-ranging analysis.
Industrial ecology, as a field centrally concerned with materials choice, the opportunities for environmental improvement through technological innovation, and the insights to be gained from systems-based analyses, is especially well positioned to examine whether a dramatic shift from petrochemicals to biobased materials is environmentally advantageous.
The debate over the net environmental benefits of the bioeconomy emerged in 1999 with the publication of an article in Nature Biotechnology (Gerngross 1999) and a companion piece in Scientific American (Gerngross and Slater 2000). These articles questioned whether PHA (polyhydroxyalkanoate) bioplastics are “green.” The first article examined PHAs created in high-cell-density fermentations and the second article looked at PHAs grown in genetically-modified corn plants (where the polymers were produced in the corn stover, the plant's leaves and stalks). The conclusion in both cases was that at the current state of development, bioplastics produced in these ways consumed more energy on a life-cycle basis than did a comparable petrochemical-based plastic. A follow-on paper published in the Journal of Industrial Ecology (Kurdikar et al. 2000) revisited the question by asking whether a bioplastic produced from genetically-engineered corn would improve the global warming profile of the bioplastic. It did, but the encouraging results were contingent on the use of residues as fuels for producing power—a strategy that could be employed without producing bioplastics (i.e., conventional plastics could be produced using power generated by burning corn stover and the net energy consumption would be even lower.)
This debate generated considerable interest, including an exchange of letters in the journal, Science (Gerngross et al. 2003) and a symposium at Dartmouth College, “Understanding the Sustainability of Biobased Products” in 2001. These debates involved important and complicated questions such as:
* How should mature (petrochemical) and emerging (biobased) technologies be compared?
* Which bioplastics should be used as an example when investigating the environmental advantages or disadvantages of biopolymers in general?
* How can the environmental and resource implications of increased reliance on agricultural raw materials and residuals be included in an assessment of a bioeconomy?
These questions and others led researchers to seek out industrial ecology tools.
Industrial Ecology
Industrial ecology provides a powerful prism through which to examine the environmental character of bio-based materials. Industrial ecology is an emerging field that examines local, regional, and global uses and flows of materials and energy in products, processes, industrial sectors, and economies. It focuses on the potential role of industry in reducing environmental burdens throughout the product life cycle and encompasses:
* material and energy flow studies (industrial metabolism);
* dematerialization and decarbonization;
* technological change and the environment;
* life-cycle assessment, design, planning, and management;
* design for the environment;
* extended producer responsibility (product stewardship);
* eco-industrial parks (industrial symbiosis);
* product-oriented environmental policy; and
* eco-efficiency.
Life-cycle assessment (LCA) is perhaps the tool most commonly applied in answering questions about the impacts of biobased products. Issues such as the sufficiency of biomass resources to meet industrial and dietary demands, however, require other industrial ecology tools.
Major research projects on the sustainability of biobased products are underway in the U.S. at Iowa State University, Dartmouth College, and the University of Illinois-Chicago as well as research in the European Union. In addition, the Journal of Industrial Ecology (Vol. 7, Number 3-4) a peer-reviewed international journal owned by Yale University and published by MIT Press, recently published a special issue on the impacts of the production, use, and disposal of biobased materials.
The issue provides a snapshot of the state of the emerging bioeconomy and the ability to assess its impact. The picture that emerges suggests that biobased materials may indeed help reduce our dependence on nonrenewable energy and materials without creating large new environmental problems. Biobased materials are not universally superior to those made from nonrenewable resources, however, and the research community needs to find ways to evaluate biobased materials without assessing each case individually. The following are abstracts provided by the Journal of Industrial Ecology on articles in the recent special issue. These articles provide important perspectives on the past and present search for biobased power, fuels, chemicals, and materials.
Old Efforts at New Uses
An article by Mark Finlay of Armstrong Atlantic State University provides a historical review of the chemurgy movement in the U.S. This insightful summary of an earlier extensive—and largely forgotten—effort to develop new industrial uses for farm products presents interesting parallels between chemurgy and current efforts to promote biobased products. Current U.S. federal initiatives to support biomass R&D are described by Marvin Duncan of the USDA in a separate article in the issue.
Identifying Promising Processes
The question of how to identify the biobased processes that have the greatest potential, such as for displacing use of fossil fuels, is addressed in an intriguing article by Lee Lynd of Dartmouth College and Michael Wang of Argonne National Laboratory. They suggest a number of feedstock and process factors that are particularly important in determining the extent of possible fossil fuel displacement via biological processes. The proposed framework provides a means to screen processes with respect to potential for fossil fuel displacement in the absence of product-specific information.
Impacts of Ethanol from Corn Stover
A research topic that has received a great deal of attention in recent years, particularly in the U.S., is the search for methods of producing sugars and other chemical intermediates from lignocellulosic biomass such as corn stover (stalks). Using corn stalks to make valuable products such as fuels and chemicals is a good example of by-product utilization (a topic central to industrial ecology). The unharvested portions of biomass crops, such as the stalks of the corn plant, are not without agronomic value, however—when left in the fields they serve useful purposes such as reducing soil erosion, reducing evaporative water loss and maintaining soil fertility. For this reason, farmers have been advised for many years to leave stover on their fields to protect the soil, and they are quick to recognize that there are uncertain trade-offs associated with harvesting more of the plant from the field. The industrial use of stover couples the agricultural and industrial systems in a way that explicitly connects questions of agricultural and economic sustainability and creates a need for new sorts of analysis techniques.
In their article, John Sheehan at the National Renewable Energy Laboratory (NREL) and colleagues describe a life cycle model that comprehensively addresses the impacts of stover collection on soil health, measured in terms of both of soil erosion and soil organic matter. Although there is still a great deal that is not known about what constitutes agricultural sustainability, their model is the first of its kind and may serve as a framework for discussing the benefits and trade-offs of substituting a petroleum fuel with one made from an agricultural by-product.
Importance of Agriculture
Like Sheehan, Veronika Dornburg and colleagues at Utrecht University in the Netherlands examine the importance of including measures of the use of (potentially scarce) agricultural land when assessing biobased materials. They use an interesting meta-analysis approach combining a dozen previous assessments of biopolymers to draw some general conclusions about potential energy savings and GHG emission reductions per unit of agricultural land used. These results are compared to similar measures for bioenergy production from energy crops, revealing that biopolymers offer interesting opportunities to reduce the utilization of non-renewable energy and to contribute to greenhouse gas mitigation.
In a third article related to agricultural practice, Seungdo Kim and Bruce Dale of Michigan State University provide a comprehensive summary of net energy characteristics for a range of crops likely to be important feedstocks used in biobased industrial production—a topic widely debated since the seminal article on the energy balance of ethanol made from corn by David Pimental of Cornell in the early 1980s. Their research provides data that will improve the reliability of future LCAs of biobased products.
Plastics from Garbage
While the most commonly considered sources of biomass feedstock are dedicated agricultural production and agricultural by-products such as corn stover, other possible sources are waste from food processing and the organic component of municipal solid waste. Waste streams have the advantage of providing biomass without the environmental impacts of new primary production and harvesting. Kenji Sakai of Oita University and colleagues from several other Japanese universities and laboratories describe the development of a novel process for making polylactide (PLA) plastic that takes advantage of a readily available biomass source—municipal food waste.
Case Studies
The issue includes two articles that present case studies of two different approaches to assessing the merits of biobased hydraulic fluids. The case studies in the issue also include a series of four profiles of firms that manufacture biobased products. These firms represent a small sample of the industrial players that are building a new biobased product industry. Coupled with the guest columns by Robert Dorsch and Ray Miller of DuPont, Matthew Realff of Georgia Tech, and Charles Abbas of ADM, these profiles provide a glimpse into the perspectives and strategies of pioneering firms.
State-of-the-Art
There are important issues associated with a transition to a bioeconomy that have not been addressed from an industrial ecology perspective. As noted by Lynd and Wang in their article, life-cycle environmental issues related to the impacts per unit of product have been addressed much more thoroughly than resource issues regarding the availability and sufficiency of biomass for various uses. Similarly, impacts on water quality, soil fertility, and rural development are issues that should be addressed before we lock ourselves into biomass technology choices.
Clearly the research described here is but the beginning of what has to be a sustained investigation and discussion. Industrial ecology can contribute to the understanding of the environmental benefits and limitations of a transition to greater use of biomass for the production of fuels, chemicals, and other materials. All of the articles in the special issue are free and available in full text at http://mitpress.mit.edu/jie/biobased.
This article was written by:
Robert Anex
Department of Agricultural and Biosystems Engineering
Iowa State University
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