Analysis And Comparison Of Lifecycle Assessment Studies

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In our assessment, we analyze 11 LCA studies for biobased energy, fuels, and materials [3, 5, 9-17]. These studies compare biobased energy, fuels, or materials with their conventional counterparts made from fossil resources. The criteria that led to the selection of these LCA publications were that (a) the studies should compare environmental impacts of biobased products with fossil-based product alternatives on a cradle-to-grave basis, i.e., including the entire process chain from the extraction of raw materials, via processing of intermediate and final products, up to the final disposal and that (b) the publications should cover several environmental impacts and not only energy consumption and CO2 emissions. As a consequence of these criteria, prominent studies on biopolymers (e.g., [18-20]) are not included in our comparison. All analyzed LCA publications refer to the situation in Europe and to the current state of technologies. The selected publications differ considerably with respect to the amount of published background data and the degree of detail regarding explanations about methodology and results. Also, studies with a comparatively limited level of detail are included in this analysis if (a) they contribute to a better understanding of environmental impacts from biobased materials not studied from this perspective before and (b) they provide an indication about uncertainty and sensitivity of LCA results [2].

Furthermore, the LCA publications vary regarding the assumptions made for agricultural yields, treatment of agricultural residues, allocation procedures for byproducts, and waste-treatment scenarios. We did not correct for all of these differences; instead, we compared biobased and fossil products based on the assumptions made in each respective LCA study.* The most important assumptions made in the LCA publications analyzed in this chapter are given in Table 7.1.

The life-cycle assessment studies consider a wide range of different environmental impact categories. We select four categories for our analysis here, based on data availability and quality. In total, the environmental performance of 45 product pairs made from renewable and fossil resources is evaluated by use of the following four environmental impact categories:

Consumption of non-renewable primary energy resourcesf Global warming potential Eutrophication potential Acidification potential

Several studies differentiate between terrestrial and aquatic eutrophication potential (e.g., [17]), others, such as [5, 9], choose a different method and give total eutrophication potential. We follow the latter approach and uniformly calculate eutrophication potential as the sum of terrestrial and aquatic eutrophication, expressed in phosphate equivalents. We further assume that the carbon dioxide originating from biomass is equivalent to the amount that was previously withdrawn from the atmosphere during the growth period of crops and, therefore, does not contribute to global warming. Fossil fuels required for transport and processing of biomass as well as the production of auxiliaries (e.g., application of mineral fertilizers) are, however, taken into account. For the comparison of biobased energy, fuels, and materials with their fossil counterparts, land is only used for the production of biobased products. This means that no reference land use is defined for fossil-based products because quantities required to produce the latter are negligible in comparison with biobased products.

We obtain the data for this LCA comparison from the relevant publications and recalculate the environmental impacts consistently for 1 hectare (1 Ha) of agricultural land. In the case of biopolymers, this means that the results refer to the amount of a particular biopolymer that can be produced using the agricultural crop yield available from 1 Ha (e.g., 38 t potatoes to produce starch-

* This approach differs somewhat from the analysis of Dornburg et al. [1]. There, the regional- and producer-specific LCA data are harmonized by (a) assuming identical average yields for agricultural crops, by (b) adopting waste incineration without energy recovery as the single only waste treatment option, and by (c) taking the life-cycle data for fossil-based polymers from one single source, e.g., the Association of Plastics Manufacturers Europe [21].

t In the following, we refer to the consumption of nonrenewable primary energy resources as "nonrenewable energy consumption."

TABLE 7.1

Overview of Core Assumptions Made in LCA Publications

Publication

Corbiere-Nicollier et al. 2001 [9] Diener and Siehler 1999 [10]

Product

Transport-pallets

Fiber composites for car construction Polymer films, cups (single serving)

Scope of Analysis

Cradle to grave Cradle to grave Cradle to gravea

Crop Yield per Hectare

17.2 t china reed

5.5 t flax

Dinkel and Waldeck 1999 [12]

Gartner et al. 2002 [13]

Reinhardt et al. 2000 [14]

Plates (single serving)

Packaging material

Lubricants, hydraulic oils, packaging material, fiber composites, insulation material Heat, electricity, fuels

Cradle to grave Cradle to grave Cradle to grave

Cradle to grave

38.9 t potato

12.1 t triticaled;

3.3 t rapeseed; 2.7 t sunflower; 20.51 china reed; 17.3 t willow;

8.4 t various woods;

5.7 t wheat straw

Allocation Method

Substitution

Waste-Treatment Scenario

Incineration

Utilization of Agricultural Residues

Recycling

20% landfilling, 80% No incineration b

Incineration, composting, No production of biogas Incineration

Incineration

Substitution of oils0

Substitution, Incineration allocation of environmental impacts

Reinhardt and Gärtner 2003 [15]

Reinhardt and Zemanek 2000 [3]

Fuels and rapeseed oil Cradle to grave

Heat, fuels

Cradle to grave

Fiber composites for car construction Loose-fill packaging Cradle to material grave

3.3 t rapeseed

5.7 t orchard grass;

9.9 t Cottonwood;

1.8 t wheat straw;

2.8 t pasture;

14.81 sugar-beet;

10.11 china reed;

2.8 t corn

9.0 t hemp

Substitution

Substitution

Incineration

Incineration

Substitution, allocation of environmental impacts

Various waste-treatment scenarios

Substitution of mineral fertilizers Substitution of mineral fertilizers

Substitution of mineral fertilizers

Note: — = no information available.

O"

" Without use phase. b Without energy recovery.

0 For the consumption of flax and hemp as fiber material, it is assumed that the oil contained in the seed is used to replace sunflower and primrose oil. d Total plant.

e Wheat produced by extensive farming.

Adapted from: Weiss, M., Bringezu, S., and Heilmeier, H., Zeitschrift Angewandte Umweltforschung, 15/16, 3-5, 2003/2004. With permission.

based loose fills). For the petrochemical counterparts, the same amount of final product was then chosen as reference. Crop yields and data on biomass processing are obtained from the respective LCA studies. If agricultural yields are not reported, we use yield data from [22] as estimates. The differences between biobased and conventional product alternatives are calculated for each environmental impact category separately:

difference between biobased and fossil product alternative environmental impact of the biobased product alternative environmental impact of the fossil product alternative index for the environmental impact category

As the result of this approach, negative values indicate advantages of biobased energy, fuels, and materials, whereas positive values represent environmental advantages of their fossil counterparts. For final characterization, we divide the various options for biomass use into three categories: energy (power and heat), fuels, and materials. For the three groups, median values are calculated separately for each of the four environmental impact categories.

7.3.1 Results

The relative differences between biobased and conventional products per hectare and year with respect to the four environmental impact categories are presented in Figure 7.2*. The results show large variations, both between single product alternatives and among the different environmental impact categories.

7.3.1.1 Nonrenewable Energy Consumption

All biobased product alternatives consume less nonrenewable energy throughout their life cycle than their fossil counterparts. Energy savings range from around 1300 GJ/(Haa) for the china reed/PP transport pallet to 8 GJ/(Haa) for PLA packaging material produced from cornstarch. The outstandingly high value of the china reed/PP transport pallet is mainly a consequence of (a) the relatively high yield of china reed per hectare of agricultural land, (b) the large proportion of the crop (70%) that is usable for fiber-composite production, and (c) the high resource and energy requirements to produce conventional glass fiber/PP pallets. Glass fiber/PP pallets are, however, not the most common fossile-based alternative for transportation where et biobased(i) Elfossil(i)

* It is important to note that the units for all environmental impact categories are chosen to visualize the performance of biobased and fossil product alternatives. The size of the bars representing the different environmental impact categories in Figure 7.2 is, therefore, not an indication for the relative importance of one environmental impact category compared with another.

[9] transport materials

ation-pallet (chi

potato starch, ir

•s (potato starch potato starch, co untera-Plast®

ymer-film (LDP

mer-film (Flunt " polymer-film

[5] hydraulic oil (rape-seed )il vs. conventional oil)

[5] lubricants (sunflower vs. conventiona ) [10] fiber composites for cais (hemp vs. fibe') îposites for car; (hemp vs. ABS)

fiber composites for cars (flax vs. glass) na reed/PP vs. glass fiber/PP)

cineration vs. biogas vs. EPS

loose-fills (wh nsulation (flax eat starch, ext.

-ffli

Is (wheat starch :arch vs. prima -fills (cornstarc packaging mate packaging mate [5] packaging S, incineration incineration)

cineration vs. biogas vs. EPS

vs. mineral woo vs. primary PS)

vs. primary PS rial (PLA, whea ial (PLA, corn material (PLA, ) □=

MTBE)

ethanol vs. gaso

diesel)

die;

sel) diesel)

power/ heat

[3] heat [3] heat (orch at (wheat, whole eat (wheatstraw [3] heat (wheats 14] heat (whea I from forestry [3] h

14] heat (misc. [14] heat (wi low, plantation [3] heat (cotton eat (willow, plan heat (china reed [3] heat (chi ] heat (china re electricity (tritic misc. grass vs. ard-grass vs. fue plant vs. fuel o vs. natural gas traw vs. fuel oil el oil) oil)

[14] [14] e straw vs. fuel vs. natural gas) eat (spruce vs wood vs. fuel oil vs. natural gas) wood vs. fuel tation vs. fuel o vs. natural gas) reed vs. fuel ed vs. fuel oil) ale vs. hard coal)

oil)

fuel oil)

oil)

oil)

-2S00

environmental impact in nonrenewable energy consumption in GJ/(ha*a) 2 M global warming potential in dt CO2/(ha*a)

3 □ eutrophication potential in 10-1 kg PO4/(ha*a) acidification potential in kg SO2/(ha*a)

FIGURE 7.2 Relative environmental impacts of biobased and conventional products.

pallets. Instead, mainly wood pallets are used. It is very likely that the environmental advantages of the china reed pallet would decrease if this pallet were compared with other conventional transport pallets.

High savings of nonrenewable energy can also be achieved with disposable plates, cups, and polymer films made from potato and potato/cornstarch (580 to 290 GJ/[Haa]). ETBE (ethyl t-butyl ether) from sugar beet, which can be used as a substitute for the fuel additive MTBE (methyl t-butyl ether), reduces nonrenewable energy consumption by approximately 380 GJ/(Haa). The substitution of conventional packaging materials by corn- or wheat-based biomaterials and the replacement of conventional diesel by RME, SME, or rapeseed oil offers only minor reductions of nonrenewable energy consumption (8 to 54 GJ/[Haa]). This is mainly caused by (a) the relatively low hectare specific yield of biobased raw material (i.e., corn and wheat) and (b), especially in the case of RME (rapeseed methyl ester) and SME (sunflower methyl ester), by the energy-intensive chemical conversions of raw oil to final fuel products.

7.3.1.2 Global Warming Potential

The results in this category vary from around -520 dt CO2/(Haa) for the china reed/PP transport pallet to +12 dt CO2/(Haa) for loose fills made from wheat starch. The findings for this category are strongly related to the results in the category of nonrenewable energy consumption because energy production is the main source of CO2 emissions. Consequently, products that score best with respect to nonrenewable energy use also generally offer the greatest reduction of CO2 emissions.

7.3.1.3 Eutrophication Potential

The total results in this category range between -10 kg PO4/(Haa) for the transport pallet and around +45 kg PO4/(Haa) for polymer films studied by Dinkel et al. [11]. Biobased energy, fuels, and materials score in general worse than their fossil counterparts. Exceptions are, among others, the china reed/PP transport pallet (-10 kg PO4/(Haa) and the fiber-reinforced composite for cars (-5 kg PO4/[Haa]). The relatively poor performance of biobased products in this category is mainly a consequence of atmospheric ammonia emissions as well as nitrate and phosphate leaching to surface and ground waters from fertilizer application in agriculture [17]. As improved farming practices can reduce these fertilizer losses by (a) reducing the total amount of fertilizers applied and (b) improving the management of fertilizer application, a high potential to reduce eutrophication associated with biomass production exists. This potential is independent of further biomass utilization and processing options.

7.3.1.4 Acidification Potential

The results in this category range from -450 kg SO2 equivalents/(Haa) for the china reed/PP transport pallet to 45 kg SO2 equivalents/(Haa) for heat produced from wheat versus fuel oil. Relative to their fossil-based counterparts, disposable plates and cups made from potato/corn starch as well as loose fills made from potato starch also reduce acidification considerably. In contrast, the production of heat from wheat or china reed and the generation of RME and especially ETBE from sugar beet (+32 kg SO2/[Haa]) increase acidification compared with their fossil product alternatives. The use of biomass to manufacture materials (mainly polymers and fiber-composite products)

generally decreases acidification. In contrast, acidification is increased if biomass is used to replace fossil fuels to produce energy (power/heat) and transportation fuels. The specific acidification potential for energy, fuels, and materials is mainly caused by sulfur and nitrogen oxide emissions from incineration processes. This holds for biobased and conventional products. In addition, ammonia emissions from fertilizer application are a typical source for acidification caused by biobased products. Energy and fuels from biomass score worse than their fossil counterparts because, for these products, the process chains from raw biomass to incineration are typically short, and the production of biomass contributes significantly to the total product-specific acidification potential. In contrast, these emission sources constitute only a smaller portion of the total acidifying emissions for biobased materials because process chains are longer. As a result, there is a higher chance that biobased materials (typically characterized by long process chains) are advantageous over their fossil product alternatives.

7.3.2 Specific Results by Categories of Biomass Utilization

In Figure 7.3**, the product alternatives analyzed in this chapter are grouped according to three different options of biomass utilization: power and heat production, fuel production, and the manufacture of materials. The data shown represent medians as well as value ranges.

Environmental impact

FIGURE 7.3 Medians and value ranges of different biomass utilization options.

Environmental impact

FIGURE 7.3 Medians and value ranges of different biomass utilization options.

** For this comparison, we chose the median instead of the mean because the former is more resistant against statistical outlier. This is important here as our sample sizes are comparatively small and the data do not conform to a Gausian distribution. Therefore, the choice of either median or mean to represent the mathematical average has a profound impact on the results.

The results indicate that the use of biomass reduces environmental impacts in the categories of nonrenewable energy consumption and global warming potential, regardless of whether biomass is used to produce energy, fuels, or materials. In contrast, biobased products show, on average, disadvantages compared with their conventional counterparts with respect to eutrophication. In the category acidification, biomaterials score better, whereas bioenergy and biofuels score worse than their fossil counterparts. The error bars in Figure 7.3 display the value ranges of the individual products. The ranges are, in general, large for all three options of biomass utilization. The median values in Figure 7.3 indicate, however, that bioenergy and biomaterials score on average better than biofuels regarding the consumption of nonrenewable energy resources and greenhouse gas emissions (see also Weiss et al. [7]).

7.3.3 Discussion

The findings presented in this chapter are based on the most important LCA studies on biobased energy, fuels, and materials published to date. The studies do, however, vary considerably regarding system boundaries, allocation schemes, waste scenarios, and the treatment of agricultural residues (see also Table 7.1). Errors and uncertainties of data collected for the inventory analysis might also have a significant effect on the results of individual life-cycle assessment studies. Process energy requirements and emissions for conventional products can vary substantially, depending on the data source used for the inventory analysis [2]. Dinkel et al. [11] quantify error ranges of inventory data at 40%, and different allocation schemes are reported to cause deviations up to 90%. When comparing results of the various LCA publications, it was, however, not possible to correct for all of these differences and uncertainties. The conclusions drawn in this chapter can be false if the LCA results differ only within their error margins from each other.

In our analysis, we assume identical functionality of biobased and conventional products. Possible differences regarding lifetime, product quality, and applications are neglected. However, starch-based polymers, for example, do not offer the same range of applications as conventional polymers (e.g., polystyrene) due to their susceptibility to moisture. Also, biofuels might not have exactly the same quality as petrochemical fuels. However, these differences in product properties can usually be assumed not to change the general interpretation of LCA results because, in LCA, it is ensured that the material or product choices fit the respective application (e.g., use of starch polymers for certain packaging applications but not for durable goods like car components).

The available body of LCA studies allows the identification of subsections within the system that have a particularly strong effect on the results. The studies point, in particular, to agricultural production and to the waste treatment. For these two areas, the findings and conclusions about further possibilities for improvement are discussed next.

The utilization of agricultural residues has an important effect on the environmental performance of biobased fuel and materials because, in most cases, only certain parts of the plants are used in production processes.11 Leaves and stems of crops often remain on the fields and are either (a) taken into account as a substitute for mineral fertilizers or (b) simply excluded from the product system (see Table 7.1). However, if these residues are used for energy generation, the environmental performance of bio-product can improve significantly. Along the life cycle of bio-based polymers, for example, the consumption of nonrenewable energy resources can be reduced by up to 190 GJ/(Haa), and greenhouse gas emissions are decreased by up to 15 t CO2/(Haa) [1].

The ecological disadvantages of biobased products in the impact categories of eutrophication and acidification mainly arise from biomass production using conventional agricultural practices. Würdinger et al. [17] have shown in their LCA study of loose fills from wheat starch the high potential of extensive farming practices for reducing environmental impacts compared with conventional farming practices in all four environmental categories. These results show that biobased products do not score per se worse than conventional products with respect to eutrophication. Future biomass production should, therefore, aim (a) to improve the management of fertilizer application and (b) to reduce on-site soil erosion. A reduction of eutrophication potential associated with biomass production remains doubtful, however, if farming practices do not change.

Additional environmental benefits can be realized by so-called agricultural intercrops, which are mainly used to cover fields inbetween vegetation periods. These crops can also be used for energy or material purposes [23]. Environmental impacts can be further reduced by choosing the most appropriate crop for each specific purpose and region and by processing it in the most efficient way. Related to environmental risks of biomass production, the introduction of genetically modified crops also has to be taken into account. This is, so far, not included in life-cycle assessment studies, mainly due to lack of scientifically proven insight. Further research on this subject is therefore highly recommended.

Another important factor affecting environmental impacts of both bio-based and conventional materials is the waste-treatment technology chosen. In their LCA study on loose fills, Würdinger et al. [17] state that the differences between the various waste-treatment options for conventional polystyrene loose fills are comparable with the differences between biobased and conventional loose-fill materials, based on a cradle-to-factory-gate comparison. This result is also confirmed by the findings of Dinkel and Waldeck [12] for disposable plates. Therefore, not only replacing fossil feedstocks by renewable ones, but also optimized waste management can effectively reduce environmental impacts. This finding calls for a detailed assessment of all major waste-management options, including landfilling, composting, waste-to-energy facilities, municipal waste incineration, digestion, and recycling [2].

While considerable attention is paid in LCA studies and ongoing research to issues related to agricultural production and waste management (see above), relatively little is still known about the total environmental impact and improvement potentials for the conversion of biobased feedstock to new fuels, materials, and chemicals. This holds, in particular, for biotechnological processes as, for example, applied for the production of PLA and ethanol (Note that all other products shown ft This example is less relevant for biobased energy (power and heat) production because usually the whole plant is harvested and incinerated.

in Figure 7.2 imply conventional chemical conversion, simple blending, or incineration). In view of the great progress being made in biotechnology, major opportunities for reducing environmental impacts are expected. To exploit them fully, technological as well as logistical shortcomings need to be overcome. At the same time, new environmental impacts may arise, e.g., from the use of genetically modified organisms in fermentation processes.

The completeness of LCA studies with regard to environmental impacts is not only an issue for future and novel technologies, but also for existing processes. In Section 7.3.1, we discussed four environmental impact categories, i.e., nonrenewable energy use, greenhouse gas emissions, eutrophication, and acidification. The results provide important insight into the environmental performance of bio-based versus conventional products. However, relevant environmental impacts remain excluded from our analysis, such as human and environmental toxicity, ozone depletion, as well as impacts on soil erosion and biodiversity. The reason most studies are limited to just a few indicators is the lack of data as well as the effort and costs related to closing these data gaps. This also holds for processes that were implemented on a large scale. Future research should, therefore, address these environmental impacts to come to a more complete and comprehensive environmental evaluation of bio-based energy, fuels, and materials.

Once available, a conclusion in favor of or against biobased energy, fuels, and materials needs to be drawn. This conclusion often depends on the weighing of the different environmental impacts with respect to a sustainability framework [6]. Weighing requires value judgment about the relative importance of the various impact categories (weighting) is, therefore, subjective to some extent. For this reason, it is excluded from LCA studies [24] and generally seen as the task of economic, political, and environmental decision makers.

The results presented in this chapter generally show good correspondence with the findings of Dornburg et al. [1] and Kaenzig et al. [6], even if these two publications differ from our comparative analysis regarding assumptions and harmonization steps (see footnote on page 141). This finding is a strong indication of the robustness and reliability of (a) LCA results on biobased products in general and (b) our results presented in this chapter.

7.3.4 Conclusion

In this chapter we compare nonrenewable energy consumption, greenhouse potential, as well as eutrophication and acidification potential of biobased and conventional energy, fuels, and materials based on a functional unit of 1 Ha of agricultural land. Biobased products score generally better than their fossil-based counterparts with respect to nonrenewable energy consumption and global warming potential. The use of biomass is, therefore, suitable for contributing to climate protection, independent of its specific utilization. Biobased products perform worse than conventional ones with respect to environmental eutrophication. Regarding mixed results are obtained, with biomaterials scoring on average better than conventional materials and bioenergy and biofuels scoring worse than their conventional counterparts. Product-specific results can vary considerably from these averages. Decisions in favor of or against a particular option of biomass use can only be made based on individual cases. It is, hence, advisable (a) to assess the environmental performance of the desired bioproduct, (b) to compare the result with its conventional counterpart, and (c) to evaluate the relative advantages and disadvantages by comparison with the findings for other product systems.

The results in this chapter show, that biobased energy, fuels, and materials are neither without any environmental impacts nor are they per se more environmental friendly than their conventional fossil-based counterparts. This finding calls for a comprehensive evaluation of the environmental performance of products from renewable resources.

Major disadvantages of biobased products result from agricultural emissions and the leaching of fertilizers. Various studies have shown that the environmental performance of biomass utilization can be increased by (a) adopting extensive cultivation methods and farming practices, (b) using agricultural residues and "intercrops" for energy, fuel, or material production, (c) choosing the most suitable crops for the various biomass utilization options, and finally (d) optimizing end-of-life waste treatment. New production processes, e.g., those involving biotechnology, may offer further substantial improvement potentials, but their realization will require substantial technology development. Potential negative impacts of these technological developments need to be assessed in parallel with the evaluation of these new opportunities.

For nonrenewable energy use and greenhouse gas emissions, which currently represent the most important targets of environmental and industrial policy, the results presented in this chapter show the relevance of biobased energy, fuels, and materials. In Section 7.3.1 of this chapter, the results are presented at the level of products, while the overall contribution to energy savings and emissions reduction will depend, to a large extent, on how the markets for these biobased products develop. Despite expected large growth rates of several biobased products (energy, fuels, and materials), the very large scale of conventional fossil-based products implies that the time required for biobased products to reach significant market shares may be substantial [25]. The emergence of biobased products will depend on physical limitations (availability of land), boundary conditions (fossil fuel prices, environmental legislation, etc.), their technological performance, and on developments in other technological areas. The fact that energy and fuels can be also supplied by renewable resources other than biomass, while raw materials (e.g., feedstock for the chemical industry) cannot, may lead to a focus on biomaterials in view of the limited availability of land. For the moment, we conclude that the accessible LCA studies strongly support the further development of biobased energy, fuels, and materials, which are all still in an infant stage compared with their conventional counterparts.

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