Environmental impact of PLA

Both comparative and stand-alone LCAs would provide useful environmental information on PLA. A comparative LCA could evaluate the relative environmental impacts of PLA as opposed to similar petroleum-derived or bio-based polymers such as PE, PHA, or PET. A stand-alone LCA could be evaluated to identify areas where environmental improvements can be made during the life cycle and production of PLA. 

The comparative environmental impacts of PLA and PE, PS, PP, and PET for other environmental impact categories can be estimated by applying an LCIA tool to the PLA data contained within the ecoinvent database. TRACI (Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts), developed by the U.S. EPA, was used to calculate the environmental impacts related to eutrophication, ecotoxicity, acidification, ozone depletion, smog formation, and human health (Figure 26.6) [53]. The impacts for PLA from the ecoinvent database (PLArSP) and the modified agricultural stage (PLA SP + L) are calculated in the same manner as previously discussed. 

FIGURE 26.6 Life cycle environmental impacts of PLA compared to petroleum polymers. 

LCA Results for Case 1 Table 7.1 lists the environmental impacts of PLA and foam PS clamshells. For 10,000 clamshells, foam PS had lower mass, energy consumption, carbon footprint, waste generation, and water consumption. The pollution aspects were not considered and no data were provided for eutrophication, acidification, smog generation, or release of toxic chemicals. 

The second LCA of packaging materials was provided by IFEU from Germany and was commissioned by LCA Nature Works LLC (2006). The LCA is dated but can show the improvement in reduced environmental impacts of PLA in the third LCA study (LCA Packaging NatureWorks LLC 2006). 

It is important when creating biodegradable nanocomposites that high demands are placed on the environmental impact of the surfactant. The DMA performed to investigate the thermal properties of the produced materials showed that the introduction of CNW were able to improve the storage modulus of PLA in the plastic zone. The researchers stated that the well dispersed CNW have a large potential in improving the mechanical properties of biopolymers such as PLA. 

In summary, the LCA studies show that, assuming current technological and energy use practices, PLA exhibits comparable nonrenewable energy use and greenhouse gas emissions to PE and PET [27, 38]. The life cycle environmental impacts of petro-polymers are often taken from the European Association of Plastics Manufacturers (APME). The APME has an extensive database of LCl data for numerous polymers, including PE, PET, PP, and PS. 

By examining the cradle to gate LCA of PLA in Figures 26.4—26.6, it is apparent that the majority of environmental impacts from PLA production result from the agricultural and fermentation stages. Therefore, improvement of PLA s environmental footprint should first focus on these areas. 

During the Aichi EXPO 2005 in Japan, many innovative applications for PLA were presented. For instance, new materials produced from PLA were applied to the outer wall of the exhibition pavilion of the Japanese Government to reduce the negative environmental impacts of construction materials. The building was made of materials derived from biomass, representing a significant event that expanded the possibility of the application of PLA to durable goods. 

The study presented by Vink et al. was focused on the environmental performance of PLA as measured by three life cycle impact categories fossil energy requirement, greenhouse gases and water use. The results are presented in Table 8.1. 

LCA can be used to calculate the environmental impacts of producing biobased PLA plastic. 

Table 3.2 provides the environmental impacts of producing 1 kg of Ingeo PLA. 

Plastic packaging can be produced with sustainable plastics through the use of the definitions presented above. Plastic packaging products account for approximately 30% of the plastics sold in the United States, and approximately 27% of the plastic products sold in Europe (Beswick and Dunn 2002). Sustainable plastic packaging can be made from recycled plastics or biobased plastics, like PHA, PLA, starch, and others. Life cycle assessments can be used to compare environmental impacts of using recycled or biobased plastic materials for plastic packaging products. 

The first LCA from Franklin and Associates is dated but can provide a starting point in discussing LCAs of plastics for packaging. The Franklin LCA compares the environmental impacts of PS, paper, and PLA packaging materials. Franklin and Associates use SIM Pro LCA software with a database of LCI data. Food service items were produced from polystyrene foam, paper, and PLA. The food service items included cups, plates, and clamshells. Only the clamshell data are analyzed in the following analysis (LCI Food Service Products 2(X)6). 

A third LCA that calculated the environmental profiles of clamshells was created for PLA, PET, and PS plastic materials. The LCA was calculated for use as containers for strawberries. The functional unit was 1000 containers that have packaging capacity to hold 0.4536 kg of strawberries. The LCA included transportation effects and provided environmental impact results for global wanning, energy consumption, aquatic acidification, ozone layer depletion, aquatic eutrophication, respiratory organics, respiratory inorganics, land occupations, and aquatic eco-toxicity. SimaPro LCA software was used to calculate the environmental impacts of the plastic materials. The mass of the PET was calculated based on the same volume as the PLA clamshell and the density ratio of PET and PLA (Madival et al. 2009). 

Environmental impacts of sustainable plastic containers can be determined with the LCA information and the definitions of sustainable plastics. The sustainable plastic containers can be made of recycled plastic or biobased plastics. The end-of-life for the plastic is either recycled or composted. Thus, polystyrene is not considered because sufficient recycled plastic is not available. As a comparison, virgin PET is evaluated for LCA. Recycled PET and biobased PLA can be compared for clear sustainable plastic containers. The LCA information from Madival et al. 2009 is used as a starting point. Then, WARM model from ERA is... 

The environmental impacts of the plastic materials can be calculated based on the data in Table 7.4. Environmental comparisons can be made based on the ratio of the environmental impact of the plastic material and a reference material as listed in Table 7.4. For our purposes, we will use PLA as the reference material. Thus, we will be able to compare the ways in which different plastic materials have more or less environmental impacts of global warming potential, solid waste generation, and pollution than the reference material. 

Similarly, the GSI for each of the materials can be found from the ratios of environmental impacts of the plastic material with a reference material. PLA can provide the reference material. The different environmental impact factors can be weighted with the following 50% for GWP, 25% for waste generation, and 25% for pollution factor. The pollution factor is an arithmetic average of eutrophication, acidification, ozone depletion, and freshwater eco-toxicity. Table 7.5 provides a summary of the ratios of environmental impacts of rPET and virgin PET containers versus the reference containers made from PLA. 

Table 7.15 lists the environmental impacts of plastic bottles produced from PLA, PET, and rPET with 25% KR recycled content. 

Plastics can be made with lower environmental impacts of lower GHGs, lower waste generation, and lower pollution. NatureWorks LLC provides a sustainable plastic example by producing the Ingeo PLA with lower energy and lower carbon footprint than previous versions of PLA. 

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