Eco-profiles of the
European Plastics Industry
METHODOLOGY
A report by
I Boustead
for
PlasticsEurope
Last revision
March 2005
PlasticsEurope may be contacted at
Ave E van Nieuwenhuyse 4
Box 3
B-1160 Brussels
Telephone: 32-2-672-8259
Fax: 32-2-675-3935
CONTENTS
ECOPROFILE METHODOLOGY 6
OVERVIEW 6
IMPACTS AND INVENTORIES 8
INDUSTRIAL SYSTEMS 9
ECO-PROFILES AND LIFE CYCLES 11
SYSTEMS AND SUB-SYSTEMS 12
INDUSTRIAL NETWORKS 13
MODELLING USING NET FLOWS 15
THE NATURE OF EXTENDED SYSTEMS 16
FUELS 18
THE FUEL PRODUCING INDUSTRIES 19
Oil fuels 19
Coal 20
Electricity 22
Sulphur 26
Combined heat and power plants (CHP) 27
DESCRIBING THE PERFORMANCE OF A SYSTEM 30
ECO-PROFILE CALCULATIONS 32
CALCULATING AVERAGES 32
FEEDSTOCK ENERGY 36
CAPITAL EQUIPMENT 39
HUMANS 39
ECO-PROFILE DATA 40
Data gathering 40
Data quality 41
Complexity of plant 41
Accuracy of data 42
Format of records 42
Sharing common facilities 42
Missing data 43
Common problems 43
INTERCHANGE OF HYDROCARBON FUELS 45
CO-PRODUCT ALLOCATION 46
Establishing system function 46
Simple mass partitioning 47
Using process detail 49
Stoichiometric partitioning 50
Partitioning with excess of reactants 51
Procedure 1 52
Procedure 2 52
Procedure 3 53
Procedure 4 53
Procedure 5 53
Summary 54
Electricity partitioning in chlorine production 54
Simple mass partition 54
Elemental mass partition 55
Partition to NaOH and chlorine only 55
Elemental partition to NaOH and chlorine only 56
Mass partition with allowance for hydrogen 56
Elemental partition with allowance for hydrogen 56
Mechanistic approach (mercury cell) 57
Mechanistic approach (diaphragm/membrane cell) 58
Modified mechanistic approach for the diaphragm cell 59
Partition using reaction enthalpy 59
One stage enthalpy partition 63
Partition using gross calorific value of hydrogen 65
Partition using net calorific value of hydrogen 66
Summary of partitioning methods for the chlorine cell. 66
Using multiple partitioning parameters 66
Substitution partitioning 67
Economic partitioning 68
Partitioning in polystyrene production 69
UNWANTED CO-PRODUCTS 70
Treat the co-product as waste 71
Use a substitution procedure 71
Allocate only materials 72
SULPHURIC ACID DILUTION 73
STEAM CO-PRODUCT 75
STEAM CONDENSATE 76
REPORTING RESULTS 76
FORMAT OF RESULTS TABLES 78
Data categories 78
Energy data 80
The simple energy table 80
Primary fuel tables 82
Fuels expressed as mass 83
Water consumption 83
Raw materials inputs 84
Air emission data 85
Carbon dioxide equivalents 86
Water emission data 87
Solid waste 88
The empirical system 88
EU Solid waste categories 90
UNDERSTANDING ECO-PROFILE RESULTS 91
General observations 91
Interpreting energy data 92
USING ECO-PROFILE DATA 99
REFERENCES 102
ECOPROFILE METHODOLOGY
The purpose of this report is to explain the background and general methodology that has been used in the eco-profile calculations. It also explains, in outline, how to make use of the results. Much of the content of this report is applicable to systems other than polymer production but there are some unique features of the petrochemical industry that need to be highlighted.
OVERVIEW
Manufacturing industry is concerned with processing materials and the laws of science govern the operations involved in this processing. Two consequences follow from this. First, energy is needed to effect the desired transformations and secondly, waste is inevitably produced. The notion that it is possible to produce an energy-free and waste-free industrial process is a myth. As a result, the best that can be achieved is minimising the use of energy and reducing waste production.
The first step in attempting to achieve this is to describe the situation that currently exists because this is the base line against which any future improvements will be judged.
Within individual factories, this has been the task of engineers for over a century because energy use and waste generation directly affect the profitability of an enterprise. However, the last thirty years have seen the development of a further stimulus in the form of environmental pressures from both governments and public opinion.
The source of this interest can be traced to the late 1960’s when a number of world modelling exercises were carried out. In particular, the publication of the National Academy of Science’s Resources and man,[i] Meadows’ book The limits to growth[ii] and the Club of Rome’s document A blueprint for survival[iii] led to considerable concern about the continued viability of society as a whole. The primary cause was thought to be increasing population and the inability of the planet to cope with the consequent demands that would be placed upon it. In particular, all of these publications singled out the exhaustion of fossil fuels and some of the scarcer mineral resources, as well as possible pollution problems.
With hindsight, some of the predictions of these modelling exercises were somewhat extreme. Nevertheless they sparked an interest in describing the behaviour of extended industrial systems.
Initially interest focused on the use of energy, especially fossil fuels, and the work was often referred to as energy analysis. Because the calculations required the construction of balanced flow charts to describe the processes, the consumption of raw materials and the generation of solid waste were also automatically calculated. As a result, some analysts referred to the work as resource analysis or resource and environmental profile analysis.
One of the earliest reports of the results of this type of work was presented to the World Energy Conference by Harold Smith from ICI in 1969 and concerned some aspects of the chemical industry.[iv] This was followed in the early 1970’s by the publication of a large number of reports on various production systems[v] and the work was given added impetus by the oil crises of the mid 1970’s. As a result many companies elected to have their practices examined and reports and publications have continued right up to the present day[vi] although many of these reports have remained confidential to the sponsoring organisation and are not freely available.
During this same period, the environmental lobby was persistent in its attacks on the packaging industry and especially beverage packaging, where the introduction of one-trip packs was seen as wasteful. In the USA pressure grew to promote returnable containers and resulted in the pioneering legislation in Oregon[vii] that has subsequently been repeated elsewhere. In Europe, the EC Directive on beverage packaging[viii] was passed in 1985. The data needed to implement these different forms of legislation were all based on the results of energy and resource analysis as a means of decision making, although it has to be admitted that, at times, the analyses have not been entirely objective.
It is, however, important to remember that long before the interest in energy occurred, there was awareness, in many parts of the world, of the localised pollution problems being caused by other human activities. Litter, the smogs of Los Angeles and Tokyo and acid rain in Scandinavia all pointed to the need for international action to curb the problems. Then in the 1980’s the potential threat of greenhouse warming and ozone depletion added to the need to consider the emission of pollutants both to air and water. (It is worth noting that, like today, pollution control measures are controversial. Burning coal was prohibited in London in 1273 but it was not until the Clean Air Act of 1956 that the prohibition became reality!)
The methodology for evaluating the global release of these pollutants is identical to that for calculating energy consumption and so energy analysis expanded to encompass their computation. As a result, the term energy analysis fell into disuse and the terms eco-balance, eco-profile, cradle to grave analysis, life cycle analysis and life cycle assessment appeared, all essentially describing the same type of work. In the present work, the term eco-profile has been used rather than life-cycle analysis because the systems examined follow the production sequence only to the point where the polymer resin is ready for sale to the converter. The use and final disposal are not considered and so the results do not represent a complete life cycle analysis.
IMPACTS AND INVENTORIES
In 1990, the first ever meeting of some of the practitioners in this field of study met at a conference in Vermont, USA[ix]. It was this conference that first coined the term life cycle assessment. Perhaps the most important conclusion of this meeting was recognition that although the inputs to and outputs from any industrial system can be measured or estimated, the causal link between many of these parameters and observable environmental impacts was simply unknown.
There is therefore a need to separate this type of work into three distinct phases.
1. The inventory phase – where the aim is to provide a detailed description of the inputs of energy and raw materials into the system and the outputs of solids, liquids and gaseous wastes from the system.
2. The interpretation phase – where the inventory results are linked to identifiable environmental problems.
3. The improvement phase – where the system is modified in some way in an attempt to reduce the environmental impacts.
Once the improvement phase has been completed, the inventory phase is now repeated on the modified system not only to see if the desired effects have been produced but also to identify any unwanted deleterious side effects that have accidentally been introduced. This simple cyclic sequence of operations led to the now well known triangle shown in Figure 1. Although subsequent researchers have modified this simple idea, sometimes to the point where it is unintelligible, the basic simplicity of the concept still underlies life-cycle assessment.
Of the three phases, the methodology for the inventory phase is well established and based on the detailed work of the last thirty years. In contrast, the interpretation phase is still less well developed. In general, the nostrum that less-is-better, which had been widely used in energy analysis can readily be applied to energy and resource use. However, while its application to air, water and solid waste emissions seems attractive, there is only a remote possibility of being able to reduce all of these characteristics simultaneously, because they are usually interlinked. Without some guidance about the relative global importance of the different emissions, suggested courses of action to improve the current state could well make matters worse. For example, flue gas desulphurisation is technically simple and removes sulphur oxides from flue gases by reacting them with limestone. Unfortunately, the reaction produces carbon dioxide. Thus there is a choice to be made between sulphur oxides which are known precursors of acid rain and carbon dioxide, a known greenhouse gas.
Figure 1
Sequence of procedures developed at the first SETAC conference
It should also be noted that during the 1990’s, the International Standards Organisation, ISO, set up a technical committee to agree formal standards for life cycle assessment. Of direct interest in the present work are the standards 14040 to 14043.[x]
INDUSTRIAL SYSTEMS
The principles on which energy analysis was based have been described in detail elsewhere[xi] and with a few refinements, these same principles are still used in life cycle calculations. The basic concept underlying the methodology is that of the system.
Although manufacturing industry is primarily concerned with products, it is the production system that is of importance in this type of analysis. A system is defined as any collection of operations which when acting together performs some defined function. Here it is the emphasis on the function that is important because if any two systems are to be compared then they must be performing equivalent functions. For this reason, a system whose function is to produce 1 kg of PVC cannot be compared with a system whose function is to produce 1 kg of aluminium. It is meaningless to say that PVC is better or worse than aluminium on the basis of such a comparison because the system that produces PVC can never produce aluminium and vice versa.
It is important to recognise that this systems approach is generally applicable to all life cycle assessments. Somewhat confusingly, ISO introduced the term product system originally defined as a collection of materially and energetically connected unit processes that perform one or more defined functions[xii]. As an after thought, which is usually overlooked, the definition was broadened to say that for the purposes of life cycle assessment, the term ‘product’ used alone includes not only product systems but can also include service systems. This broadening of the definition is important because life cycle assessment can be used to examine more abstract systems such as communications and transport where there is no obvious concrete product.
Schematically, any industrial system can be represented as shown in Figure 2 where the collection of operations of interest are enclosed in the box labelled ‘industrial system’. The outline of the box denotes the system boundary and separates the system from its surroundings – the system environment. The system environment acts as the source of all inputs to the system and the sink for all outputs from the system. It is clear therefore that when the system is operating, it directly affect the system environment. The input side of the system represents the consumption of energy and raw materials, factors that are involved in all discussions about resource conservation and use. The output side of the system represents the emissions into the environment and these are of direct concern in pollution arguments.
Figure 2
Schematic representation of a simple industrial system
The physical description of the system, or inventory, is a quantitative description of all flows of materials and energy across the system boundary either into or out of the system itself. Note that this definition of a system is identical to that used in conventional thermodynamics and much of the formalism of thermodynamics is directly applicable to life cycle inventories. As a consequence, it is necessary to devise relatively few new procedures to manipulate the data. Many of the arbitrary decisions introduced by some analysts in recent years arise from a lack of appreciation of the close ties between life cycle analysis and thermodynamics.
Because the system is a physical system, it must obey all of the physical laws. That is, it must obey the law of conservation of mass and the laws of thermodynamics. These laws provide a useful check on the validity of any description because if any of the laws are violated, then the description is invalid.
In some instances, the system boundary can be identified as a physical boundary. It may, for example, enclose all of the operations carried out by a particular piece of machinery or in a specific factory. On the other hand, it frequently cannot be so identified. For example, a transport operation can be represented by a system whose function is to change the geographical location of a material. Alternatively, a complex industrial process may be analysed into a set of simpler operations, none of which exist in isolation in reality but, for the purposes of the analysis are treated as if they do. (See later under Partitioning)