While the EIO-LCA model is useful in many regards, it is outdated and has some limitations. The data describing the inter-industry transactions were developed from the 2002 benchmark U.S. input-output table, and there likely have been considerable changes since then. in addition, the emissions associated with the various industries likely have changed due to increased regulations of emissions and changing energy production systems. For this study, we used the U.S. 2002 (428-sector) Producer model, and the adjusted industry output was deflated from 2013 dollars to 2002 dollars.
For each of the three sectors examined (biobased chemicals, bioplastic bottles and packaging, and biorefining), a custom model was developed by entering the adjusted output that could be considered biobased for each of the sector groupings. In addition to the uncertainty surrounding the use of the EIO-LCA model, there is significant uncertainty concerning the percentages of biobased products that make up the total industrial sectors. Because of these uncertainties, the results presented in this study are estimates and should be used cautiously and in context. The aim of this analysis was to provide a range of estimates for GHG emissions and the reductions in the use of petroleum.
Other Environmental Aspects of Biobased Products Biobased products are an important part of human history, from providing the first forms of heating and tools to advancing education by providing media for written communication.
Many of these original uses of biobased products are still very important to many economies and society in general; however, many new biobased products have been developed in the last 150 years. Cellulose nitrate (1860), cellulose hydrate films or cellophane (1912), and soy-based plastics (1930s) are three examples of biobased materials that were developed prior to the development of the petrochemical industry in the 1950s.
With the increased use of petrochemical-based polymers and products, certain biobased materials were supplanted by petroleum-based feedstocks for the production of polymers and other materials. With renewed interest in the environment, fluctuating oil prices, and developments in biotechnology, scientists in the 1980s developed biodegradable biobased plastics, such as PLA and PHAs. These bioplastics, based on renewable polymers, have the potential of reducing the use of fossil fuels and the associated greenhouse gas emissions.
The lifecycle assessment (LCA) framework defined in the ISO 14044 standard can be used to understand and quantify the environmental impacts of these biobased products. This framework has been used in the literature to examine the lifecycles of various biobased products and to compare them to the fossil fuel-based products they could replace. The ISO 14044 standard has been beneficial in normalizing LCA methods and in providing a common standard that has increased the comparability and rigor of various studies.
However, within this framework, there is no guidance on how to deal with the important issues that are unique to biobased products. The environmental analyses of biobased products have been shown to be sensitive to assumptions concerning the storage of biogenic carbon, the timing of emissions, direct and indirect changes in land use, and the methodologies used for accounting for carbon. The lack of commonly-used, extensively-shared, and scientifically-sound methodologies to address these topics has been noted by OECD (2010), Nowicki et al. (2008), Pawelzik et al. (2013), and Daystar (2015.).
Climate Change Impacts There is extensive literature that deals with the role of biobased feedstocks as a renewable resource and their enhanced environmental performance compared to non-renewable resources. LCAs are available in the literature that compare biopolymers and various petrochemical polymers; however, the results can be very disparate because of the lack of consistent LCA methodologies that are needed to address biobased products.
One example that has been the subject of extensive research is the role of petrochemical-based plastics, such as PE and PET, with regard to global warming potential (GWP) compared to biobased alternatives. , The majority of studies focused only on the consumption of non-renewable energy and GWP, and they often found biopolymers to be superior to petrochemical-derived polymers.
Other studies that considered these and other environmental impact categories were inconclusive. It also is valuable to note that maturing technologies, future optimizations, and improvements in the efficiencies of biobased industrial processes are expected as we learn more about these processes and products. Yates and Barlow undertook a critical review of biopolymers to address the assumption that biopolymers are an eco-friendly alternative to petrochemical polymers because they are produced using a renewable feedstock and because they potentially are biodegradable.
The research that they examined in the literature consistently identified that the farming practices used to grow biobased feedstocks may produce varying levels of environmental burdens. In addition, the energy required to produce these biobased feedstocks may, at times, be greater than the energy required to produce petrochemical polymers.
Carbon Storage in Biobased Products Biogenic carbon requires additional accounting methodologies as compared to anthropogenic carbon emissions that originate from the burning of fossil fuels. There are two fundamental methods that can be used to account for biogenic carbon:
- Account for the carbon uptake as an initial negative emission, carbon stored for a period of years, and the later burning or decompositions as a positive emission in the life cycle inventory.
- Assume that biogenic emissions are carbon neutral and are excluded from life cycle inventories.
The benefits and issues related to temporary carbon storage and biogenic carbon currently are being debated in the scientific community. There is literature that supports storing carbon for a set period of time to reduce its radiative effects, which warm the Earth.
The hypothesis is that this storage over a specified time period has the potential to reduce its GWP within a given analytical time period. The benefit created by temporarily removing carbon from the atmosphere depends largely on the analytical time period within which the GWP is calculated, which typically is 100 years. Benefits from storing carbon temporarily would generally be greater for short analytical time periods, and the benefits would decrease as the time period increases.
These benefits have been questioned by many scientists on the basis that removing carbon for a period of time will only delay emissions and ultimately increase future emissions. The EPA has recognized the importance of a sound methodology to account for biogenic carbon, and it has released a draft regulation setting guidelines for accounting for biogenic carbon emissions. Currently, this regulation is in the Notice-and-Comment Period.
Land Use Change With the world’s rapidly increasing population, additional land or improvements in agricultural yield will be required to support people’s needs. Direct land use change (LUC) results from the intentional conversion of land from its current use to a new use.
To determine direct LUC emissions, the Intergovernmental Panel on Climate Change (IPCC) has provided guidelines and data that have been incorporated in tools, such as the Forest Industry Carbon Accounting Tool (FICAT), which was developed by the National Council for Air and Stream Improvement. Direct LUC emissions associated with biobased products must be included according to ISO 14067 and the GHG Protocol Initiative.
There are several methodologies that use an economic equilibrium model to determine market feedback and increases in production yields from agricultural intensification, but they have a high degree of uncertainty because of price elasticity, unknown LUC locations, the productivity levels of previously unused land, trade patterns, and the production of co-products. Despite the uncertainty and the issues associated with determining indirect LUC, it is an important factor associated with biobased products.
Disposal Biobased materials often are inherently biodegradable or they are engineered to be biodegradable in landfills. This feature potentially could reduce the amount of land required for landfills. The portion of biobased carbon in products that does not decompose will remain in the landfill indefinitely, so the landfill can serve as a carbon sink.
This permanently captured carbon that previously would have gone into the atmosphere has the potential to reduce the GWP of the product over its life cycle. End of life options have been shown to change the conclusions of LCA studies when comparing different biobased products. However, it is difficult to model the future of a product when it is first created. End of life LCA modeling also is sensitive to the biogenic accounting methodologies that are used, as discussed earlier.
Water Use As a result of the variability of weather and its effects on watersheds, the use of water for agricultural purposes is of constant concern, just as is the use of water for non-renewable energy sources. Researchers and companies now use life cycle techniques to explore and compare the tradeoffs of using certain biobased feedstocks for biobased products and their potential impacts on water usage. The primary complicating factor is the geographic specificity of water impacts, since individual watersheds and aquifers have very specific characteristics, which can vary greatly.
Worked Cites
- Golden, J.S., Handfield, R.B., Daystar, J. and, T.E. McConnell (2018).
- An Economic Impact Analysis of the U.S. Biobased Products Industry: 2018 Update. Volume IV.
- A Joint Publication of the Supply Chain Resource Cooperative at North Carolina State University and the College of Engineering and Technology at East Carolina University. 2018.
