Potential and Challenges of Life-Cycle Assessment as a Tool for
Green Chemistry
Mina Yekkalar1, Elham Abazarian2
1) MS.c. in Civil and Environmental Engineering, Researcher at Office of Sustainability, Amirkabir
University of Technology
2) BS.c. in Chemical Engineering, Amirkabir University of Technology
“Green Chemistry” is the term that is accepted widely for explaining the tendency towards
sustainability and chemical processes and products that are more environmentally friendly. LifeCycle Assessment is an important assessment tool for decision making; In particular, it can
determine process stages exactly with a high environmental effect when it is applied throughout
the planning phase. Therefore, it can provide guidelines regarding the optimization of applying the
actual technology. Life cycle assessment has been described as a tool for comparing products and
processes or different components during a life-cycle.
The current study provides a profound review with respect to the principal descriptions of Green
Chemistry as well as Life-Cycle Assessment (LCA) as a tool that evaluate environmentally the
chemical products and processes. This paper tries to consider challenges of LCA methodologies
to green chemistry as well.
Keyword: Sustainability, Green Chemistry, Life-Cycle Assessment, Environmentally Friendly
Chemical Processes and Products, Challenges of LCA
1. Introduction
“Green Chemistry” is the term that is accepted universally to describe the tendency towards
chemical processes and products that are more suitable for the environment [1].
Various studies in the field of green chemistry often advance new products or methods as ‘green’
or ‘more environmentally friendly’ than their conventional partner, in spite of the fact that these
articles usually do not evaluate the environmental performance quantitatively.
Fortunately, in the last decades a variety of procedures and their ready-to-use guidance have
emerged to design products and processes in an environmentally friendly manner. Life-cycle
assessment (LCA) is one of the most important tools.
The basis of this paper is a profound review of the definitions of Green Chemistry and investigation
of the operators that are the sources of the movement towards Green and Sustainable Chemistry,
and then Life-Cycle Assessment (LCA) is considered from an environmental point of view as a
tool for assessing chemical products and processes. Furthermore, it is attempted to investigate the
most important challenges of LCA methodologies to green chemistry.
2. Objectives for Green Chemistry
Extensive information about chemicals, and categorizing a growing number of chemical
substances as being “hazardous”, will be involved in health and safety, and also leads to difficulty
and high cost in using those substances. It will certainly results in the restriction of waste which
consists of those substances, by local authorities and governments as well as increase in the costs
of disposal. Therefore, legislation will progressively compel chemical industries that are the
biggest sources of hazardous substances to improve their products and processes by replacing
hazardous substances with other safe substances in their processes or products and also by
minimizing the amount of their waste and its hazards [2].
As shown in Figure 1, the costs and other constraints for a chemical product are obvious all over
the supply chain from the growing expenses of raw materials, due to increasing rareness of
petroleum and penalties exerted by carbon taxes for using it, to an increasing knowledge
concerning the risks that are often related to that chemicals among end-users, and their awareness
about the necessity to separate themselves from any chemical which is recognized as being
hazardous in their supply chain.
Figure1. Supply chain pressure [2]
In addition, as shown in Figure 2, in this situation Green Chemistry may be considered as a chain
of reductions. These reductions result in benefits including economic, environmental, and social
improvements [3]. Waste reduction causes costs to be saved because waste disposal is increasingly
becoming expensive, especially when it is hazardous. In addition, costs are saved when energy
usage is lessened and also more efficient processes are made by decrease in materials consumption.
Furthermore, these reductions result in environmental advantages regarding the consumption of
feedstock and also end-of-life disposal. Moreover, an expanding use of renewable resources will
lead to the more sustainable manufacturing industry [4].
Figure2. Chain of reductions in green chemistry [3]
3. Development of Life-Cycle Assessment in Green Chemistry
Chemical industry is getting more informed about environmental burdens and some companies
can understand that Green Chemistry may offer the business advantage and competitive benefit.
In this situation, it is crucial that the benefits which are presented by Green Chemistry can be
quantified. Legislation or supply chain compulsions can convince a company to use a process or
substance that is environmentally benign, but how can they choose a really “greener” option?
Trying to apply Green Chemistry during the life-cycle of a chemical product is specifically
important [5]. Figure 3 presents the life-cycle of a product in the area of Green Chemistry.
These requirements have resulted in developing life-cycle assessment (LCA) [5]. LCA is usually
used to determine the environmental impacts of one economic activity, commonly at a particular
place and one point in time [6]. Considering all feasible environmental and socio-economic issues
related to the proposed project in terms of quality and quantity, as well as giving the obtained
information to decision makers is its primary purpose. Then, environmental damage from the
proposed project can be reduced and any environmental benefits can be determined.
Figure3. Life-cycle of a product in Green Chemistry [5]
A large number of chemical products used conventionally today were not made for end-of-life. In
addition, entire supply-chain issues including resource and energy consumption and production of
waste were not necessarily regarded. The Green Chemistry method in design stage should help to
promise the sustainability of novel products across their entire life-cycle and decrease the number
of mistakes that we make, when it is implemented at the design section.
Some of the research relating to Green Chemistry has concentrated on chemical producing
processes. It can be believed here that Green Chemistry leads us towards the “ideal synthesis” [7].
Figure 4 shows the elements of the "ideal synthesis".
Figure4. "ideal synthesis" elements [7]
Yield is the metric which is recognized widely in chemistry research for estimating the efficiency
of a chemical synthesis. LCA presents a simple and comprehensible method for measuring the
success of a synthetic route and comparing it to other routes.
4. life-Cycle Methodology
4.1. LCA Background
The beginning of the LCA methodology may be found in the late 1960s. Concerns regarding the
limitations of raw materials and energy resources stimulated interest to find ways in order to
explain cumulatively the energy usage and to estimate future resource supplies and use [8].
Early researches applied various methods without a common theoretical structure. Since 1990,
efforts have been done in order to develop and standardize the LCA methodology under the
coordination of the Society of Environmental Toxicology and Chemistry (SETAC). International
Standardization Organization (ISO) presented an international standard for LCA which has
recently been revealed and is going through assessment and revision [2]. The methodology system
for ISO is similar to that for SETAC but it has some differences for the interpretation phase. In
this phase, additional analysis and sensitivity studies have been included in ISO [2].
4.2. Framework of LCA
The LCA methodology in fact consists of a group of different methods in a common structure. The
technical framework for the management of LCA and its applications under ISO 14040 are shown
in Figure 5.
Figure5. Technical framework of LCA and its applications Based on ISO 14040, 1997 [9]
The items determined in the goal and scope definition phase include definition of the study
objective, the system boundaries that specify which unit processes must be involved inside the
LCA, environmental impacts which will be reviewed for evaluation and functional unit that is a
source for assuring the comparability of LCA results [9].
Collecting data and calculation mechanisms are mainly included in the inventory analysis phase
of life cycle assessment in order to quantify appropriate inputs and outputs of a product system.
These inputs and outputs may involve the resources usage and discharges to water, air, and land
that are related to the system. These data comprise the input to the life-cycle impact assessment
too [9].
The impact assessment phase of LCA is intended to assess the significance of potential
environmental effects by using the results of the second phase, i.e. the life-cycle inventory analysis.
This process generally includes the connection of inventory data with particular environmental
effects and trying to comprehend them. The extent of detail, selection of impacts that are assessed
and methodologies used depend on the goal and scope of the study [9].
In the interpretation phase of LCA, results of the inventory analysis and the impact assessment are
taken into account simultaneously and in the case of LCI studies, only the results from the
inventory analysis are considered. This phase should describe limitations and give the decisionmakers interpretations and suggestions that are compatible with the goal and scope of the study.
Life-cycle interpretation is also aimed at providing an introduction of the results of an LCA which
is easily comprehensible, perfect and consistent and is in agreement with the goal and scope
definition of the study [9].
5. Challenges of LCA
LCA is the prominent tool for the evaluation of environmental impacts generated by products and
processes from ‘cradle to grave’. Although it is popular and is codified by organizations such as
the International Organization for Standards and the Society of Environmental Toxicology and
Chemistry, LCA is a tool that requires improvement. It is usually told in the reports that LCA has
not developed yet to a well-defined tool. Table 1 determines 15 most important problem areas and
arranges them according to LCA phases. This section addresses main challenges which are related
to Green Chemistry.
Table1. LCA problems by Phase [10]
Goal and Scope
Inventory Analysis
Life-Cycle Impact
 Functional definition
 Boundary selection
 Social and economic impacts
 Alternative scenario considerations
 Allocation
 Negligible Contribution (Cutoff)
 Local technical uniqueness
 Impact category and methodology
 Spatial variation
 Local environmental uniqueness
 Dynamics of the environment
 Time horizon
 Weighting and valuation
 Uncertainty in the decision process
 Data availability and quality
5.1. System Boundaries
Decisions regarding inclusion and exclusion lead to some problems during goal and scope
definition, while problems in inventory analysis include flows and transformations. Fundamental
decisions with respect to the borders of the study, base of comparison (functional unit) and physical
relationships between processes involved determine mostly the representativeness and
consequently, the value of an LCA. Therefore, problems in functional unit definition, selecting
boundary, and allocation are the most important problems studied in the first part of this review
While the philosophy of LCA is to investigate the beginning of all processes and pursue them
thoroughly to their ends, the analysis becomes unmanageable if boundaries are not delineated [11][12]. As Hendrickson, Horvath, Joshi, and Lave (1998) discuss, defining a system boundary that
does not include life-cycle stages in the evaluation, will definitely underestimate environmental
impacts [13]. However, this is a practical imperfection of the data collection process [14].
Determining the system boundaries depends on the individual goals and scope of the study [15][16]. For example, when processes are common to all options compared, they may be kept out of
system boundaries. It is very important to present an exact determination of the system boundaries
as part of the final results in any LCA [15]-[17].
5.2. Inventory Analysis Difficulties
Studies relating to Life-cycle that is based on the quantification of raw materials and wastes
discharged to the environment have been done for over 20 years. However, the inventory analysis
still needs agreement about several critical points, although it is the more factual part of LCA. In
addition, inventory outcomes of studies with similar systems can still be notably different [18].
5.3. Allocation Rules
Allocation may be defined as the relative distribution of the responsibility for resource usage,
emissions and waste streams of the processes in the life-cycle [16]. For instance, when several
products under the study are able to be sold or leave the system for advantageous utilization in
other systems, discount should be performed for their share of environmental burdens and thus,
their share of the inventory data. This problem of co-product allotment to multiple output flows is
tackled using an allocation parameter that indicates the physical behavior of the system, as
pragmatically as possible [19]. According to the report of Stromberg et al. (1997), assignment of
all environmental effects to the main product would really be the simplest approach to allocation
[16]. However, this approach would not be suitable when the process being considered supports
notably the overall environmental impact of the system or when a considerable amount of coproducts exist.
A single solution to allocation problems appears to never be settled. As a result, it might be better
to undertake the problem using sensitivity analysis for all important allocation procedures in
subsequent case studies [20].
5.4. Impact Assessment Methods
Although, the required tools for implementation of the inventory analysis are improved well,
interpretation of the results leads to more problems, because transforming the inventory data into
human health or ecological effects are not well comprehended yet [17]-[21]. Besides, the lack of
a standard impact assessment methodology intensifies the problem, as different methods all have
their own advantages and shortcomings. The most controversial and subjective step of life-cycle
studies is to allocate relative weights to each impact group, because tradeoffs between the various
environmental problems is required [11]. Difficulties related to the normalization component of
the impact assessment also exist, and there is no international agreement on how to perform this
stage [22]. The main problems are associated with the selection of reference area and finding the
suitable data [23].
5.5. Temporal and Spatial Features
Impact assessment is involved in possible impacts in the majority of life-cycle studies and it does
not have a linear relation between the extent of the industrial processes and their actual impacts.
Temporal and spatial features are usually disregarded, because LCA is basically an implement to
preserve resource as well as prevent pollution [23]. However, it is possible to incorporate time and
space features by considering information such as the background levels of substances.
It is believed that all processes in the inventory analysis take place at a reference time. Huppes
(1996) claims that while LCA is not described dynamically in time, time features should be
considered in the advance of present LCA methodology since they are necessary in taking into
consideration, for example, the environmental impacts of heavy metals in mining wastes [24].
However, the spatial representativeness of the system should be defined in the goal definition
phase of an LCA (i.e. global, continental, regional, national or company level). When equivalency
factors for some of the impact groups in LCA are used, spatial differentiation is often investigated
[25]. Differentiation is required in local problems like acidification, although this is not essential
for global problems such as global warming.
5.6. Data Quality
The quality of the data which is used in LCA is critical, because the accuracy of the LCA outputs
is just as good as the accuracy of the input data [15]-[19]-[26]. However, lack of available
inventory data has led to make LCA an expensive and time-consuming procedure [27].
As Guinee et al. (1993) and Udo de Haes (1993) propose the development of databases and
software by applying accepted data would support the problem solution. Furthermore, this would
be especially helpful for documenting the global resource use and emissions data, which is
essential for the normalization stage of the impact assessment. Lack of such data often impedes
the normalization stage [25]-[27].
6. Conclusion
Green Chemistry arises from a number of items mentioned below as a tendency to the development
of chemical processes and products that are more suitable for environment.
1) Hazardous chemicals need high costs to be disposed of.
2) Public pressure and knowledge concerning chemicals is growing, and an increasing number of
chemical substances are categorized as being “hazardous” substances.
Although a number of studies have been conducted in the field of Green Chemistry, they have not
evaluated the environmental performance quantitatively in many cases.
Studying Green Chemistry quantitatively in every part of the life-cycle of a chemical product is
crucial. These requirements and reality checks have caused the life-cycle assessment (LCA) to
emerge, which is usually used for the determination of the environmental impacts of a new product
or process compared to traditional products or processes.
Although LCA is popular and codified, it needs progress. Main reported problems of LCA related
to Green Chemistry include: determining the system boundaries, problems associated with
inventory analysis, allocation rules, impact assessment procedures, temporal and spatial features,
data quality.
Therefore, explaining clearly each stage of the selected methodology and the problems
encountered should be one of the purposes of prospective LCA studies which comprise the
assessment of process.
7. References
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