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1 This article was downloaded by: [Universita Studi la Sapienza] On: 06 September 2011, At: 01:59 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Energy Sources, Part A: Recovery, Utilization, and Environmental Effects Publication details, including instructions for authors and subscription information: Bioplastics and Petroleum-based Plastics: Strengths and Weaknesses F. Gironi a & V. Piemonte a a Department of Chemical Engineering, Materials & Environment, University of Rome, Rome, Italy Available online: 09 Aug 2011 To cite this article: F. Gironi & V. Piemonte (2011): Bioplastics and Petroleum-based Plastics: Strengths and Weaknesses, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 33:21, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan, sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Energy Sources, Part A, 33: , 2011 Copyright Taylor & Francis Group, LLC ISSN: print/ online DOI: / Bioplastics and Petroleum-based Plastics: Strengths and Weaknesses F. GIRONI 1 and V. PIEMONTE 1 1 Department of Chemical Engineering, Materials & Environment, University of Rome, Rome, Italy 1. Introduction Abstract The application of biomass, such as starch, cellulose, wood, and sugar, used to substitute fossil resources for the production of plastics, is a widely accepted strategy towards sustainable development. In fact, this way a significant reduction of non renewable energy consumption and carbon dioxide emission is accomplished. In recent years, several typologies of bioplastics were introduced and the most important are those based on cellulosic esters, starch derivatives, polyhydroxybutyrate, polylactic acid, and polycaprolactone. Nowadays, the most important tool to evaluate the environmental impact of a (bio)plastic is the life cycle assessment that determines the overall impact of a plastic on the environment by defining and analyzing several impact categories index like the global warming; the human toxicity; the abiotic depletion; the eutrophication; the acidification; and many others directly related to the production, utilization, and disposal of the considered plastics. The aim of this work is to present a comparison between bioplastics and conventional plastics through the use of the Life Cycle Assessment methodology. In particular, the life cycle assessment s Cradle to Grave of shoppers made from Mater-Bi (starch-based plastic) an polyethylene were reported and compared as a case study in order to highlight the strengths and weaknesses of the bioplastics and the conventional plastics. Keywords bioplastics, environmental impact, mater-bi, life cycle assessment, renewable resources Nowadays the worldwide production of bioplastics is about 750,000 tons/year and is very modest when compared with 200 million tons/year of conventional plastics derived from petroleum; it is estimated that in the near future, the growth will be exponential, reaching about 1,000,000 tons/year in 2011 (Widdecke et al., 2008). The major manufacturers are Nature Works (with a production of 140,000 tons/year of polylactic acid [PLA]) and Novamont (with a production of 35,000 tons/year of Mater-bi, starch-based bioplastics). The interest in the development of biodegradable plastics noticed in recent years is due to motives of both environmental and strategic nature (Zhang et al., 2000; Demirbas, 2007; Anderson et al., 1998; Gross and Kalra, 2002). As a matter of fact, in order to reduce the environmental impact of plastics (especially in terms of CO 2 released in the environment) some of the products obtained from agriculture (starch, cellulose, wood, Address correspondence to Dr. Vincenzo Piemonte, Department of Chemical Engineering, Materials & Environment, University of Rome, via Eudossiana 18, Rome 00184, Italy. piemonte@ingchim.ing.uniroma1.it 1949

3 1950 F. Gironi and V. Piemonte sugar) are used as raw materials. This way the net balance of carbon dioxide is greatly reduced, since the CO 2 released during production, utilization, and disposal of plastics is balanced by the CO 2 consumed during the growth cycle of the plant. Furthermore, petroleum, with a constantly rising price, is replaced by renewable raw materials obtained from agriculture. Several biopolymers are produced from fermentative processes of natural valuable raw materials, such as wheat, corn, sugar, rice, potatoes, and soya. Specific consumption per unit of biodegradable plastic produced is different (Harding et al., 2007) depending on the raw material used, but there is no doubt that these raw materials will be taken away from other uses, in particular from alimentation, with a consequent increase in the cost of food. From this point of view, it is clear that the development of bioplastics requires the use of less valuable raw materials, such as agricultural or food industry wastes or from the use of non edible genetically modified plants, which may be grown in lands (e.g., mountains) not suitable for the production of food. The use of bioplastics was also stimulated by a second environmental motive, related to problems connected with the disposal of waste: in the 1990s, the main system for the disposal of municipal solid waste (with a fraction of plastics equaling 20 30%) was the disposal in landfill. Traditional plastics undergo degradation phenomena with very slow kinetics; hence, the volume required by these materials in landfills is virtually stable over time. On the contrary, bioplastics show higher degradation rates in landfills (Ishigaki et al., 2004) and, therefore, the required volumes can be contained. Currently the market suggests several typologies of bioplastics, among which the most important are those based on cellulosic esters (Hoppenheidt and Trankler, 1995), starch derivatives (TPS) (Bastioli, 2005), polyhydroxybutyrate (PHB) (Harding et al., 2007), polylactic acids (PLA) (Tokiwa and Calabia, 2006), and polycaprolactone (PCL) (Demirbas, 2007). Application fields range from uses in the pharmaceutical and biomedical area as potential biocompatible materials for artificial protheses, for sutures, and as a medium for controlled drug release; in the field of packaging, including food and shoppers; and in the field of agriculture as mulching films (Widdecke et al., 2008). Nowadays, the development of bioplastics is hampered by higher costs of production of these materials as opposed to traditional plastics; however, a thorough analysis considering not only the cost of production but also the costs associated with the managing of waste might lead to various results. In this article, the main features of bioplastics will be discussed, highlighting the problems linked with their biodegradation and with possible scenarios for their disposal. Therefore, in order to provide first considerations on the strengths and weaknesses of the conventional plastics and bioplastics, the results reported in different literature life cycle assessments (LCAs) studies (Harding et al., 2007; Hoppenheidt and Trankler, 1995; Bastioli, 2005; Patel, 2002; Krueger et al., 2009) were analyzed and discussed. Furthermore, an original cradle to grave LCA study (from the raw materials up to the final disposition of the analyzed product) focused on the comparison between shoppers made from Mater-Bi and polyethylene (PE) is reported as a Case Study. 2. The Biodegradability Matter In accordance with ASTM D 6400, biodegradable plastics are only those whose degradation occurs as a result of natural action of microorganisms, such as bacteria, fungi, and algae, in a limited period of time and in absence of ecotoxic effects.

4 Bioplastics vs. Petroleum-based Plastics 1951 Aerobic or anaerobic biodegradation may occur and the process that completely degradates the polymer into biomass is called Complete Biodegradation, while if the original polymer is completely converted in gas and minerals we have a Mineralization. In any case, the biodegradation takes place in two phases: an initial phase in which microorganisms launch a chemical attack on the polymer chain aimed at the breaking of chemical bonds, and a second phase of real biodegradation. These two phases are strongly controlled by the presence of numerous factors, both endogenous (as molecular weight, crystallinity, flexibility of the molecule) and exogenous (temperature, humidity, ph, availability of oxygen, enzymatic activity) that can, therefore, alter and/or modify the outcome of the biodegradation process itself (Kale et al., 2007b). As reported by Davis and Song (2006), the most favorable final disposition, from an environmental point of view, for a bioplastics is represented by the composting process that transforms, by a biodegradation process, the disposed product into a soillike substance called humus, CO 2, water, and inorganic compounds and leaves no visible, distinguishable, or toxic residues. Indeed, with regard to recycling, nowadays processes for selecting and recycling bioplastics are not yet developed, despite what happens for conventional plastics. The composting of bioplastics can, therefore, be an optimal solution, taking into account that the process conditions in terms of temperature, humidity, oxygen, etc. must be strictly controlled if we want to achieve appreciable results in terms of final products. The work of Kale et al. (2007a) concerning the biodegradation of PLA bottles under controlled and natural conditions is interesting. The experimental results show that the efficiency of degradation in a natural environment is equal to approximately 10 20% of efficiency in a controlled environment. Additives are often present in the bioplastics, mainly to improve the mechanical properties of the obtained material. This choice may not only cause a reduction in the biodegradability of plastics and other serious ecotoxic effects, but it might even determine the non-compostability of the bioplastic, making in fact, a vain every advantage achievable through the use of a bioplastic. 3. Bioplastics and Petroleum-based Plastics: How to Compare? If on the one hand, the real biodegradation of a plastic represents an extremely delicate problem, certainly a key aspect in assessing the applicability or not of bioplastics is the impact on the environment resulting from their use, during the entire life cycle from production to final disposal (cradle to grave). This type of analysis is called Life Cycle Analysis (LCA) and is based on finding some factors considered crucial in assessing the impact that a particular product can have on the environment. Among the most important factors or indices of environmental impact there are: Abiotic depletion: the characterization factor is the potential of abiotic depletion of the extraction of those minerals and fossil fuels. The unit of the characterization factor is kg of antimony (Sb) equivalents per kg of extracted mineral. Global warming: the characterization factor is the potential of global warming of each greenhouse gas emission to the air. The unit of the characterization factor is kg of carbon dioxide (CO 2 ) equivalents per kg of emission. Human toxicity: the characterization factor is the potential of human toxicity of toxic substances emitted to the air, water, or/and soil. The unit of the characterization factor is kg of 1,4-dichlorobenzene (1,4-DB) equivalents per kg of emission.

5 1952 F. Gironi and V. Piemonte Fresh water aquatic ecotoxicity: the characterization factor is the potential of fresh water aquatic toxicity of each substance emitted to the air, water, or/and soil. The unit of this factor is kg of 1,4-DB equivalents per kg of emission. Marine aquatic ecotoxicology: the characterization factor is the potential of marine aquatic toxicity of each substance emitted to the air, water, or/and soil. The unit of this factor is kg of 1,4-DB equivalents per kg of emission. Terrestrial ecotoxicity: the characterization factor is the potential of terrestrial toxicity of each substance emitted to the air, water, or/and soil. The unit of this factor is kg of 1,4-DB equivalents per kg of emission. Photochemical oxidation: the characterization factor is the potential of photochemical ozone formation of each substance emitted to the air. The unit of this factor is kg of ethylene (C 2 H 4 ) equivalents per kg of emission. Acidification: the characterization factor is the acidification potential for each acidifying emission to the air. The unit of this factor is kg of sulfur dioxide (SO 2 ) equivalents per kg of emission. Eutrophication: the characterization factor is the potential of eutrophication of each eutrophying emission to the air, water, and soil. The unit of this factor is kg of phosphate ion (PO4-) equivalents per kg of emission. Tables 1 and 2 show a collection of LCA literature data (Patel, 2002, 2005); each LCA characterizes and compares the environmental impact of various bioplastics (thermoplastic starch (TPS), polylactic acid (PLA), and polyhydroxyalkanoates (PHA) and traditional plastics (high and low density polyethylene, Nylon 6, polyethylene terephtalate (PET), polystyrene (PS), polyvinyl alcohol (PVOH) and polycaprolactone) with an approach cradle to grave. The comparison is given on the basis of some of the most important indices of environmental impact cited above. Table 1 Energy required from non-renewable sources and CO 2 emissions for different types of plastics currently on the market Type of plastic Energy requirement, MJ/kg Global warming, kg CO 2 eq/kg From non-renewable sources HDPE LDPE Nylon PET PS PVOH PCL From renewable sources TPS TPS C 15% PVOH TPS C 60% PCL PLA PHA 57.0 Not Available

6 Bioplastics vs. Petroleum-based Plastics 1953 Table 2 Eutrophication and acidification for different types of plastics currently on the market Type of plastic Acidification a Eutrophication b Pellets LDPE (1 kg) TPS (1 kg) Starch foam (1 kg) Starch film (1 kg) Loose fills Starch foam (1 m 3 D 10 kg) PS foam (1 m 3 D 4 kg) Films and bags TPS (100 m 2 ) Starch-polyester (100 m 2 ) PE (100 m 2 ) a (g SO 2 eq). b (g PO 3 4 eq). Overall, the data reported in Tables 1 and 2 show how the production and use of bioplastics is more advantageous compared to conventional plastics from the energy demand and emissions of greenhouse gases point of view. On the contrary, they have a strong impact on the environment for acidification of soil and the eutrophication, mainly because of the use of fertilizers and chemicals in the cultivation of renewable raw materials used for the production of bioplastics. However, it should be pointed out that the presence of non-biodegradable copolymers in bioplastics (see Table 1) decrees a significant increase in energy demand and CO 2 emissions compared to bioplastics. Indeed, in an attempt to improve the performance of mechanical biopolymers, non-biodegradable copolymers are added thus reducing the biodegradable power of the obtained material. It is important to stress that the results of above LCA were obtained using the incineration with energy recovery as final provision: this choice is not particularly favorable to bioplastics mainly for their low calorific value. The analysis of LCA data, always show that bioplastics have some indices of environmental impact lesser than those of other traditional plastics, while other indices are in favor of the latter; hence, the need to determine an index of overall environmental impact where all indices can be incorporated and adequately weighed. To that end, there are various methods for weighting factors of environmental impact, aimed precisely to the determination of a single global index. One of the methods most often used in the LCA is called distance-to-target (Weiss et al., 2007), which deals directly a pair of plastics to compare (for example PLA and PE) providing a single index of environmental impact on the pair itself. In this regard, Figure 1 shows the value of the cumulative index of environmental impact for a couple of products of commercial interest. Zero values of this index indicate a substantial balance between the two materials in terms of environmental impact. Positive values indicate a conventional plastic superiority, while negative values indicate a lower environmental impact of bioplastics. The data seem to be entirely in

7 1954 F. Gironi and V. Piemonte Figure 1. Values of the overall environmental impact for several plastic-bioplastics pairs evaluated with the distance to target methodology. (color figure available online) favor of bioplastics, with the exception of two cases (regarding packaging with PLA and loose-fills-based starch compared with polystyrene). However, since that methodology defines the weight of the various indices of environmental impact depending on the target of each index, it is clear that the results are strongly influenced by the criteria of choice and priorities that are given to each category of environmental impact. Another possibility to give an overall impact index is to group the impact categories into three macro-categories: Human Health, Ecosystem Quality, and Resources as proposed by the Ecoindicator-99 methodology (Goedkoop et al., 2000). Then we must assign a weight to the individual macro-category and define a global index of the impact I given by: I D X i p i c i ; where p i is the assigned weight to the macro-category of impact i and c i is the value of the macro-category of impact. The result in terms of convenience of a conventional or a new generation product is a function of the importance that will be assigned to individual macro-categories. Representing the three categories in a mixing diagram (Figure 2), each point within the triangle represents a weighting combination. In each point of the mixing triangle, the relative weights always add up to 100%. Therefore, the weighting question is, how much weight out of 100% is attached to each of the three safeguard subjects. In a mixing triangle, each corner represents a weight of 100% for one safeguard subject; in Figure 2, the top corner is the weighting combination where Ecosystem Quality is weighted 100%, and 0% weight is given to both Human Health and Resources. Opposite each corner is the 0%-weight line for this safeguard subject: Any point on the base of the triangle of Figure 2 gives 0% weight to Ecosystem Quality, and the weights are

8 Bioplastics vs. Petroleum-based Plastics 1955 Figure 2. Weighting problem: triangle diagram solution. (color figure available online) split between 100% Human Health/0% Resources in the bottom-left corner to 0% Human Health/100% Resources in the bottom-right corner. We only consider positive weights, that is, a positive impact score always means a damage: only points within the mixing triangle are taken as reasonable weighting sets. The figure shows two sets of weights corresponding to point A (60% Ecosystem Quality, 20% Human Health, and 20% Resources) and B (40% Ecosystem Quality, 30% Human Health, and 30% Resources). In the A condition it is more convenient to use Product 1 while in the B one it is preferable to use Product 2: the focus on one or other product is a function of the weight that will be assigned to individual macro-categories of impact. The border area between the two regions is the so-called line of indifference that is the set of values of the weights assigned to bring the two products tested to have the same overall impact index, and thus a condition of substantial equilibrium between the two products analyzed. 4. Case Study: Mater-Bi vs. PE Shoppers In the following, we compare the results obtained from our LCAs on shoppers made from Mater-bi and PE using the Ecoindicator-99 methodology (Goedkoop et al., 2000). This LCA methodology considers 11 impact categories: Carcinogens, Respiratory Organics, Respiratory Inorganics, Climate Change, Radiation, Ozone Layer, Ecotoxicity, Acidification/Eutrophication, Land Use, Minerals, and Fossil Fuels. The first six impact categories are then be normalized and grouped in the macro-category Human Health that considers the overall impact of the emissions associated to the product analyzed on the human health; the categories Ecotoxicity, Acidification/Eutrophication, and Land Use flow in the macro-category Ecosystem Quality considers the overall damage on the Environment, while the Minerals and Fossil Fuels are grouped in the macro-category Resources that accounts for the depletion of non renewable resources.

9 1956 F. Gironi and V. Piemonte The LCAs were performed by using the SimaPro7 software, while the data of LCIs were taken both from the Ecoinvent v.2 and the Buwal 250 libraries. The data about the Mater-Bi production (provided directly from Novamont, with data relating to production in Terni, Italy) are updated to 2004 (Ecoinvent v2) and refers to a co-polymer with a starch content of 35% and the left 65% are biodegradable polyester derived from non renewable sources (polyester type not specified). For the PE, the production process of granules was performed on average data, for various production sites throughout Europe, contained in the Eco-profiles prepared by the European Plastics Industry (Buwal 250, data updated to 2002). The main assumptions made to perform the LCAs are: Nature is not part of the production system, this implies that all the emissions (fertilizers, pesticides, etc.) relative to the area allocated for agricultural production are strictly taken into account. As for the biodegradable polyester contained in the co-polymer Mater-Bi, it has been considered the PCL (biodegradable polyester made from fossil fuels) (Demirbas, 2007). The production of Mater-Bi and PE shoppers is achieved through three phases: Production of granules, transportation of granules in the processing establishments, and process of production of the shoppers by blow foil extrusion. The LCAs have been realized on the basis of 1,000 shoppers made from Mater-Bi (total weight of 68 kg) and PE (total weight of 52 kg), respectively. The different weight between the two shoppers is due to different mechanical properties of the Mater-Bi and PE, that is to obtain shoppers with the same mechanical characteristics, different thickness of polymer films are needed (Davis, 2003). The composting process has been chosen as the best disposal scenario for the shoppers made from Mater-Bi. In particular, it was considered a degradation of Mater-Bi by 60% (the remaining 40% is divided between biomass and recalcitrant residue) in the presence of oxygen, such that 95% of the degraded carbon evolves in CO 2. The remaining 5%, assuming the presence of small anaerobic pockets (due to not perfect mixing of the medium) is considered to evolve in CH 4 (Hofstetter et al., 2008). Furthermore, the model provides the treatment of the collected water in appropriate facilities and municipal waste disposal by incineration for not composted wastes, including relative emissions. The Recycling was chosen as the best disposal scenario for the shoppers made from PE. The production efficiency of PE granules from recycled waste is about 90% (1 kg recycled shoppers produce 0.9 kg of granules). Transportation and energy are considered requirements of the selection and reprocessing processes. Furthermore, we assume that the material obtained downstream of the process is being used for production in place of virgin material. The results of the LCAs cradle to gate are reported in Figures 3 and 4 in terms of macro-categories of damage and mixing diagram for the weighting. Figure 3 shows how the production of Mater-Bi shoppers has a strong impact in terms of damage to quality of the ecosystem (it is worth noting that this macro-category includes the impact categories acidification, eutrophication, ecotoxicity, and land occupation ). On the contrary, the effects on human health are roughly the same for both Mater-Bi and for PE. Finally, from Figure 3 it is evident that the greater damage, in terms of consumption of non-renewable resources (like petroleum-based resouces), is determined by the shoppers made from PE with respect to that made from Mater-Bi. The diagram of Figure 4 shows how the two products, using the set of weights suggested by the LCA Suisse group (40% Human Health, 40% Ecosystem Quality, and 20% Resources) (Krueger et al., 2009), are roughly equivalent in terms of environmental

10 Bioplastics vs. Petroleum-based Plastics 1957 Figure 3. Comparison LCA cradle to gate on the production of Mater-Bi and PE shoppers. (color figure available online) impact. On the one hand, the bioplastics allow saving in terms of fossil resources, on the other hand, they cause more damage in terms of the ecosystem since the use of different chemicals (pesticides, herbicides, fertilizers) is particularly harmful both for humans and the environment. As for the disposal scenarios of the two products, a very interesting result was obtained considering the comparison of the LCAs cradle to grave reported in Figure 5. As you can see from the figure, the Mater-Bi shoppers show a higher impact respect to the PE shoppers for all three damage categories; hence, all the possible weighting sets provide the same result: the recycling of the PE shoppers have a lower overall environmental impact than the Mater-Bi shoppers. The advantages, in terms of environmental impact, derived from the saving of the non renewable resources that can be achieved by the Figure 4. Weighting problem: comparison between Mater-Bi and PE shoppers. (color figure available online)

11 1958 F. Gironi and V. Piemonte Figure 5. Comparison LCA cradle to grave for the composting of Mater-Bi shoppers and the recycling of PE shoppers. (color figure available online) recycling of a conventional plastic are much higher than the advantages derived from the production of compost. On the other hand, materials that can only have a certain destination, such as the plastic used for bags for the collection of organic wastes, remain outside of this type of consideration. In this case, the final destination can only be the composting together with organic waste itself. 5. Conclusions The literature studies show, in general, a superiority of bioplastics in terms of consumption of non-renewable sources and emissions of greenhouse gases, whereas it would be preferable for conventional plastics with regard to the impact indices related to acidification and eutrophication. Obviously, depending on the weight given to the various indices of environmental impact, we may give preference either to bioplastics or conventional plastics. The LCA studies conducted to compare the environmental impact of the Mater-Bi with that of a conventional plastic, such as PE, in terms of impact associated with the production of the shoppers, yield a result only apparently controversial: the comparison appears almost at par. This result must be interpreted considering that, if on one hand, the bioplastic can save in terms of fossil resources, the other causes major damage in terms of ecosystem quality because for the production of raw material (corn) it is necessary to use an intensive agriculture with the use of different chemicals (pesticides, herbicides, fertilizers) that are harmful to the environment. The superiority of the Mater-Bi on the PE does not seem so obvious, but on the contrary, giving a high weight to both human health and ecosystem quality the Mater-Bi failed in comparison. This result can be generalized to other pairs of bioplastics/conventional plastics with close areas of employment, such as PET and PLA. Therefore, the true advantage of the bioplastics is represented by the use of renewable resources, but the benefit is paid in environmental terms due to the impact on ecosystem quality caused by the use of pesticides and fertilizers and by the consumption of land and water. As for the disposal scenarios, the comparison of the LCAs cradle to grave for the two products analyzed has pointed out the superiority, in terms of overall environmental impact, of the recycling of conventional plastics on the composting of bioplastics. On the other hand, the LCAs performed do not consider the advantages derived from the use of biodegradable products, such as bags for the collection of organic wastes or cuterly disposable, that can be disposed directly with the organic wastes avoiding the energetic and logistical costs of the processes of collection and sorting of the wastes.

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