Life Cycle Tools

Many assessment methodologies have been developed that include not only the product or process but also the entire supply chain and disposal, that is, the cradle-to-grave approach [68, 69]. Apart from life cycle assessment (LCA) and life-cycle costing (LCC) [70], the energy-based sustainability index (ESI) [52, 53], MIPS (materials input per unit service [71]) and MFA (materials flow accounting) [72] are also cradle-to-grave approaches. The main differences among all these indices lie in the way they normalize the environmental impacts. There is still no readily available simple, efficient and unambiguous methodology suitable for comparing alternative chemical technologies in such a way that they faithfully represent the benefits of implementation of sustainable chemical technologies. However, LCA is the best known and used methodology.

The original definition of LCA is that of a process aimed at evaluating the environmental burdens associated with a product, process or activity by identifying and quantifying energy and materials used and wastes released to the environment. The assessment includes the entire life cycle of the product, process or activity, encompassing (i) extracting and processing raw materials, (ii) manufacturing, transportation and distribution, (iii) use, (iv) re-use, maintenance and (v) recycling and final disposal. A general overview of LCA history and recent developments can be found in Sonneman et al. [73]. The ISO 14040 standard has provided very relevant input into the process of defining LCA.

The ISO 14040 standard determines four basic stages for LCA studies, schematically represented in Figure 5.9. "Goal and scope definition" is the first stage of the study and one of the most important, since the elements defined here, such as

Life Cycle Assessment Stages
Figure 5.9 Stages in a life cycle assessment. Source: ISO [74].

purpose, scope and main hypothesis considered are the key of the study. In first place, the goal ofthe study is defined, as well as the reasons that have lead to its realization, the kind of decisions that will be made from the results obtained and if these will be of internal use (for a company, for instance) or external (to inform the general public or an institution). Secondly, the scope of the study is defined. This implies, among other elements, defining the system, its boundaries (conceptual, geographical and temporal), the quality of the data used, the main hypothesis, as well as the limitations of the study. A key issue is the definition of the functional unit. This is the unit of the product or service whose environmental impacts will be assessed or compared. It is often expressed in terms of amount of product, but should really be related to the amount of product needed to perform a given function.

The "inventory analysis" is a technical process of collecting data, in order to quantify the inputs and outputs of the system. Energy and raw materials consumed, emissions to air, water, soil and solid waste produced by the system are calculated for the entire life cycle ofthe product or service. To make this analysis easier, the system under study is split into several subsystems and unit processes, and the data obtained are grouped in different categories in a LCI table.

The "impact assessment" identifies and characterizes the potential effects produced in the environment by the system under study. The first step is "classification," in which the environmental interventions (resources consumed, emissions to the environment) identified in the inventory analysis are grouped in different impact categories or indicators, according to the environmental effects they are expected to produce. For example, CO2 and CH4 emissions are classified in the category global warming potential (GWP).

The second step, called "characterization," consists of weighting the different substances contributing to the same environmental impact. For each impact category included in the impact assessment, an aggregated result is produced, in a given unit of measure. For example, the GWP is calculated in kg eq. of CO2, from the contribution of CO2 and CH4 emissions, among others. At this point, the so-called environmental profile ofthe system is obtained, consisting of a set of indicator scores.

The third step is "normalization," which involves the environmental profile ofthe system to a broader data set or situation, for example, relating the system's GWP to a country's yearly GWP.

The last step is "weighting," where the environmental profile is reduced from a set of indicators to a single impact score, by using weighting factors based on subjective value judgments. For instance, a panel of experts could be formed to weight the impact categories. The advantage of this stage is that different criteria (impact categories) are converted into a numerical score of environmental impact, thus making it easier to make decisions. However, a lot of information is lost, and reality is simplified.

"Interpretation" is the last stage of an LCA study, where the results obtained are presented in a synthetic way, presenting the critical sources of impacts and the options to reduce them. Interpretation involves a review of all the stages in the LCA process, to check the consistency ofthe assumptions and the data quality, in relation to the goal and scope of the study.

LCA is an holistic approach. All necessary inputs and emissions in many stages and operations of the life cycle are considered to be within the system boundaries. This includes not only inputs and emissions for production, distribution, use and disposal but also indirect inputs and emissions - such as from the initial production of the energy used - regardless of when or where they occur.

The LCA thus collects and evaluates the data on the emissions and their environmental impacts at every step in a process of production of a given product or provision of a service, starting from acquiring raw materials (including energy) and finishing with the end-of-life disposal and/or elimination of incurred emissions/ wastes (so-called "cradle to grave" approach). This approach is the strength of LCA, but also its limitation, since the broad scope of analyzing the entire life cycle of products and processes can only be achieved at the expense of simplifying other aspects. Some of the limitations of the approach are:

• LCA addresses potential rather than actual impacts. This is because, in LCA, impacts are not specified in space and time.

• The LCA model focuses on physical characteristics of industrial activities and other economic processes. Market mechanisms or other secondary effects of technological development are not included.

• LCA generally regards all processes as linear, both in the economy and the environment, but this is not always true.

• LCA focuses on environmental issues associated with products and processes, excluding economic and social consequences.

• Availability of true and reliable data is often a limitation.

The suitability of LCA as a tool for environmental evaluation of chemical products and processes has been suggested by several authors to be involved in the development and promotion of green/sustainable chemistry [44, 76-79]. The tool is well known by the chemical industry, which uses it for product and process development, marketing and communication with public authorities and clients, among other purposes.

Development of suitable inventories and LCA databases are one of the necessary components for more extensive use of the methodology. One of these is the Ecoinvent (www.ecoinvent.ch) database, which contains over 200 datasets corresponding to the category of chemical products, divided into organic and inorganic chemicals. The database contains international industrial life cycle inventory data on energy supply, resource extraction, material supply, chemicals, metals, agriculture, waste management services and transport services.

In these databases, chemical products are typically inventoried applying "cradle to gate" boundaries, which means that only the first half of the life cycle is included: from raw material extraction (cradle) until the product is ready to be sold in the market (gate). It is thus necessary to include in the life cycle the distribution, use and end of life as waste.

It is important to include the full life cycle. A good recent example is the case of methyl tert-butyl ketone (MTBE). MTBE can be produced using an efficient catalytic distillation process and it performs well as a fuel additive. However, the combination of three facts [carcinogenic potency, significant solubility in water and difficulty in avoiding leakage of MTBE into the ground water table at the point-of-use (leakage of underground tanks)] make the use of this fuel additive undesirable. MTBE was banned for this reason in California. To identify such problems a broad system boundary is necessary. However, considering the overall environmental impact of a system within a broad system boundary often gives inconclusive results.

Another interesting example of inappropriate boundary conditions for environmental assessment is the use of water- or organic-type solvents for automotive-based coating [80]. Despite the lower level of emissions from water-based coatings, application of these coatings requires more energy (even including VOC abatement for solvent based processes) due to the slow evaporation of water. The two types of solvents have a similar global impact on environment from LCA analysis, an unexpected result based on green chemistry principles and metrics, for example.

Accessibility to data and accuracy of the data are of particular importance. Even if significant progress is made in data standardization and the development of new databases and search software, relevant issues are still present. The large disagreement in LCA data for biofuel assessment (e.g., the well-known case of ethanol) teaches us the need for more reliable data as well as ofprocedures in definition ofthe elements to consider in a LCA analysis.

The cost, time required and the difficulties in gathering all the necessary data are the main drawbacks for carrying out a complete LCA study. For this reason, some effort has been made to develop "simplified," but still reliable, methodologies.

A streamlined LCA is a simplified version of detailed LCA, in which the scope, cost and effort required is reduced [81,82]. A complete LCA is considered to include all the relevant life cycle information in a quantitative manner. Streamlining can be based on increasing the amount of qualitative or semi-quantitative data used; this process progressively leads to applying life cycle thinking rather than LCA, that is, the concept instead of the tool. On the other hand, streamlining can be based on excluding processes or stages in the life cycle, but keeping the quantitative nature of the tool. In sustainable chemistry, streamlining approaches will be very often needed to assess products and processes by means of LCA.

Life cycle costing (LCC), also called life cycle management (LCM), is another toolbox based on life cycle concepts [83, 84]. It includes aspects related to the three pillars of sustainability: an environmental tool, an economic tool and a social tool. It is expected to become in the near future a standard addition to LCA, in order to evaluate the economic implications of a product's life cycle. Hunkeler and Rebitzer [85] have indicated that LCC is an assessment of all costs associated with the life cycle of a product that are directly covered by any one or more of the actors in the product life cycle (supplier, producer, user/consumer, end-of-life actor), with complementary inclusion of externalities that are anticipated to be internalized in the decision-relevant future. For example, a product manufacturer should include in an LCC study the costs incurred by the user of his product. On the other hand, it is important to note that only externalities expected to be internalized in the future by means of taxes or other regulatory measures must be included. The issue of externalities is one of the most controversial in environmental accounting.

There are two classes of costs to consider in LCC studies:

• Internal costs, also called private costs, which are those appearing in company's accounts, as well as those incurred by consumers or other stakeholders. These costs have a clear market value. In this group we find conventional costs (materials, fuels, labor, equipment, etc.) and potentially hidden and less tangible costs, which are usually assigned to overheads in company's accounts (permits, post-closure care, liability costs, etc.).

• External costs, also called social costs, societal costs or externalities, these are the monetized effects of environmental and social impacts caused by products and services, for which a company, consumer or another stakeholder is not obliged to pay, since neither the marketplace nor regulations assign such costs to a particular

Table 5.5 List of commonly used environmental accounting terms. Source: adapted from Muñoz Ortiz [86].

Environmental cost accounting

Full cost (environmental) accounting

Total cost assessment

Cost-benefit analysis Cost-effectiveness analysis

Life cycle cost assessment

Life cycle accounting Life cycle cost

Life cycle assessment, life cycle analysis

Addition of environmental cost information into existing cost accounting procedures and/or recognizing embedded environmental costs and allocating them to appropriate products or processes

Allocation of all direct and indirect costs (highlighting environmental, safety and health costs) to a product or product line for the purposes of inventory valuation, profitability analysis and pricing decisions

Integrating environmental costs into a capital budgeting analysis. Similar to total cost accounting (TCA). Synonymous with true cost accounting

Describes and quantifies the social advantages and disadvantages of a project in monetary units

Determines the least cost option for a predetermined environmental target, or, conversely, the option involving the greatest environmental improvement for a given expenditure

Evaluation of life cycle costs of a product, product line, process, system or facility by identifying environmental consequences and assigning a monetary value to these consequences

Assignment and analysis of product-specific costs within a life cycle framework

Total of the direct, indirect, recurring, non-recurring and other related costs incurred by or estimated for the project in the design, development, production, operation, maintenance and support of a major system over its anticipated useful life span

Identifying the environmental consequences of a product, process or activity through its entire life cycle and opportunities for achieving environmental improvements. Focuses on environmental impacts, not costs person or activity. Examples of these costs are increased risk of asthma resulting from air pollutants or the expected impacts on global climate due to emissions of greenhouse gases.

Owing to the lack of standardization, it is usual to find in the literature different terms related to life cycle approaches and/or environmental accounting. Sometimes different terms are used as synonymous, while other times the same term is used for different approaches, causing some confusion. Table 5.5 summarizes an attempt to define commonly used terms.

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