process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327

Contents lists available at ScienceDirect

Process Safety and Environment Protection

journal homepage: www.elsevier.com/locate/psep

Sustainable processes—The challenge of the 21st century

for chemical engineering

Gernot Gwehenberger, Michael Narodoslawsky ∗

Graz University of Technology, Inffeldgasse 21b, A-8010 Graz, Austria

a b s t r a c t

The 21st century inherits stark challenges for human society: environmental degradation, global warming and shrink-
ing fossil resources. All these problems are paired with a dramatic growth of the economy in China and India, home
to 2.3 billion people. We need to make more from less and we need to do this while reducing our impact on nature
by the order of magnitudes.
This challenge is particularly tough for chemical engineering. This sector is on the one hand responsible for provid-
ing most of the products of daily consumption, the base for modern agriculture as well as energy carriers for power
generation, transport, heating and cooling. On the other hand chemical engineering has a considerable impact on
the environment, via its resource consumption, its emissions and the impact of its products.
Chemical engineering will have to explore new ways in order to stay ahead of these challenges. The paper discusses
some of the aspects of the changes that process engineering will face in the 21st century as it will widen its raw
material base to include more renewable resources and simultaneously reduce its environmental impact. As a result,
the structure of process industry will be transformed dramatically. Existing design principles and methods will also
be challenged and adapted to the new challenges of sustainable development.
Given the strong impact that the challenge of sustainable development will pose to process technology engineering
education will have to change accordingly. For the first time in decades, process engineers will again be faced with
developing new processes rather than process optimization. They will need to understand how to integrate processes
into the ecosphere, how to set up raw material logistics and will have to deal with stake holders outside industry. The
process concept will become more encompassing and include the life cycle of products. All these new skills must be
taught to students today to make them fit for their carrier in the 21st century.
© 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Keywords: Sustainable processes; Renewable resources; Process synthesis; Process evaluation

1. Introduction • a strong penchant for systemic thinking, as evidenced by the

systemic approach to chemical processes in the “founding
Chemical engineering has from its beginnings been shaped by charter” of chemical engineering, the book “The Principles
characteristics that have a distinctly “modern” ring to us as we of Chemical Engineering” by (Walker et al., 1923) that gave
turn into a new and challenging century. Among them are as rise to the fundamental concept of unit operations;
follows: • a distinctly problem-oriented approach that utilises the
contributions from many disciplines, experiments as well
as modelling and innovation to solve pressing problems of
• a strong interdisciplinary streak, as chemical engineering society like energy provision, environmental protection and
bridged gaps between chemistry, physics and mechanical increasingly also the provision of high-tech materials and
engineering; pharmaceuticals.

∗
Corresponding author.
E-mail address: Narodoslawsky@tugraz.at (M. Narodoslawsky).
URL: http://www.ipt.tugraz.at (M. Narodoslawsky).
Received 15 November 2007; Accepted 11 March 2008
0957-5820/$ – see front matter © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.psep.2008.03.004
322 process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327

These characteristics have helped chemical engineering to increasingly volatile markets and an upward tendency in the
branch out into a number of other fields, like food industry, the prices of this basic commodity.
pharmaceutical sector and environmental engineering. They For the chemical sector this requires a re-orientation of its
have also been responsible for the strong presence of chemical raw material base. A change to natural gas seems to be short
engineers in the general discourse about sustainable develop- sighted, as the same sources predicting “peak oil” also predict
ment. a “peak gas”, just another 20–30 years down the line. A fall
Today these characteristics will serve the chemical engi- back to coal will require high costs in the face of global warm-
neering profession well as it faces a profound change in the ing fears, as coal makes an over proportional contribution to
framework in which it operates. Three challenges will be espe- CO2 accumulation in the atmosphere and abatement tech-
cially formidable and will shape chemical engineering in this nologies like CO2 capturing and sequestering are expensive
century. They are as follows: and probably unpractical for the chemical sector.
Obvious candidates for a sustainable resource base
for chemical industry are therefore renewable, biogenic
• The change of the raw material base: Today chemical indus-
resources. Such a change in the raw material base however
try is mainly dependent on fossil oil and gas as its main
entails a profound revolution in the structure of processes,
raw material base. Both resources will face their production
the technologies employed and the economical framework of
peak during this century, forcing process industry to look
process industry. Some important problems must therefore
for alternative resources.
be solved if this shift in the raw material base should become
• Life cycle stewardship: The pressing problems of environ-
reality.
mental degradation, especially global warming, require new
approaches towards providing services to society. There
2.1. Competition for limited resources
are two overriding principles for chemical industry in the
21st century: highest possible efficiency and lowest pos-
For one, these resources constitute a “limited infinity”:
sible environmental impact. Both can only be fulfilled if
although they may be provided for infinite time, their produc-
the sector will take over the responsibility for his products
tivity is limited. The chemical sector here enters competition
from the generation of raw materials to the re-integration
not only with the energy sector (who also sees renewables
of residues and wastes. Thus chemical engineering will
as alternative resources) but with the food sector, too (see
become concerned not only with constructing processes but
Table 1).
with developing and optimizing whole life cycles of prod-
As can be seen from this table, future pressures on renew-
ucts.
able resources may become severe. Even if a decrease of the
• New construction principles: For the first time since many
energy spent per D of GDP of 50% is factored in the increase in
decades process industry will have to generate new indus-
energy demand will be dramatic, from about 7 Gt carbon/year
trial structures for whole value chains. Besides economic
in fossil fuel to up to 37 Gt C/a on the base of biomass or
optimization the reduction of the ecological impact over
coal. If the world population also grows to approximately 10
the whole life cycle will become a necessity. This means
billion people agricultural production will have to increase
for chemical engineering to apply new principles for the
accordingly, to at least 9 Gt C/a. If taken together, this will bring
construction of its processes: process synthesis and ecolog-
annual consumption of carbon perilously close to the annual
ical process evaluation will become prominent tools for the
biomass production of 60 Gt C/a. Such a scenario will thus call
chemical engineer in the 21st century.
for almost total appropriation of natural carbon production by
man and may therefore be infeasible.
In the following chapters, these challenges and some Table 1 clearly points towards a critical raw material com-
approaches how to meet them will be discussed. petition that the global society and industry in particular
will face over the next decades. Biogenic resources will cer-
2. A sustainable raw material base tainly become important players in energy as well as chemical
industries. They are however no “drop in” alternative that
Since WW II crude oil has become the main resource base for will consistently and completely replace fossil raw materi-
chemical industry. It is interesting to note at this point that the als. The chemical sector, though playing a more visible role
“love story” between crude oil and chemical industry is rela- in future, will still remain sort of a junior partner to the other
tively short: in fact the chemical sector followed the general competitors, namely the food and the energy sector. It will
raw material source of society from agricultural resources to provide high-tech materials for other industries and most of
coal to crude oil. the energy carriers for transport. Chemical industry however
Most studies about the availability of crude oil (e.g. needs a material resource base (contrary to the energy sec-
Schindler and Zittel, 2000) point out, that we will experience tor, who can also deal with direct solar radiation) and will
a peak in production of this resource in the first quarter of therefore have to enter this competition.
the 21st century. The way up to this “peak oil” will be acceler- Three important consequences for chemical engineering
ated by the growing demand in countries like China and India arise from this new competitive renewable raw material base:
with their double digit economic growth and their tremendous
markets. • Utilising technology flexibility to avoid competition.
It is important to note that “peak oil” does not mean that It is obvious that some competitors, namely the food sec-
crude oil will no longer be available: quite contrary, peak tor and also the pulp and paper and construction sector
oil will designate a point of maximum production of this have very strict requirements for their raw material base.
resource. However it will also designate a time when produc- Whereas the former is restricted to the utilisation of edible
tion cannot anymore follow the ever increasing demand of a parts of plants and animals, the latter are restricted to for-
global society. The consequences of this situation are evident: est products of a certain quality for most of their products.
 process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327 323

Table 1 – Current and future (2050) consumption factors for carbon-based resources in Gt C/a, following Siirola (2007)
Demand Today 2050

Total carbon consumption (energy + chemical industry) 7 (fossil) 37 (from coal or biomass)
Transportation 12
Chemical production 0.3 1.5
Crop production 6 9
Annual terrestrial biomass production 60

The energy sector is less restricted by raw material quality harvested or produced in any case but are currently not or
than by logistical and economical requirements. not sufficiently utilised. Taking these resources into consid-
From all these competitors the chemical sector is the most eration the chemical sector may well profit from a general
flexible one in utilising raw materials. Chemical engineering increase of the importance of biogenic resources and avoid
has in the past already shown its prowess in transform- competition with other sectors for limited resources.
ing unwieldy raw materials into valuable products. It may • Utilising resources fully.
therefore turn to materials that may either not be used by In all cases where competition increases, efficiency of utili-
other competitors or that are “byproducts” or even wastes sation is a key to success. The same holds true for the switch
of the utilisation of biogenic resources of other industries. A towards biogenic raw materials for chemical industry: as
sampling of these “new raw materials” that may well form the raw materials become scarcer, engineering will have to
the bulk of chemical industry raw material base in 2050 is squeeze out more products from less resource.
shown in Table 2. One important strategy to achieve this goal of utilising every
As a matter of fact, the switch to biogenic raw materi- raw material to its utmost potential is to create “cascades
als can even make chemical engineering more profitable. of utilisation”. This means that a given raw material will be
Unlike fossil raw materials biogenic resources show a high treated in a way that generates different products on dif-
degree of structure. Chemical engineering may therefore in ferent levels of complexity until the whole raw material is
future not only look at efficient ways to synthesise prod- transformed in sellable products or energy services.
ucts from small molecules but also increasingly for ways A good example for this strategy is the concept of the “Green
to utilise the “natural synthesis power” of plants and other Biorefinery” (Kromus et al., 2002). This concept (see Fig. 1)
biogenic resources. The more other sectors mobilise renew- utilises green biomass like grass or leafy residues from crop
able raw materials the more chemical engineering will have plants such as beets to produce a spectrum of different
to look into ways to utilise all the high molecular building chemicals, fibres and energy.
blocks in their byproducts and wastes, such as fibres, com- This approach however is neither new nor alien to chemical
plex organic molecules and natural polymers, to name only engineering. Any crude oil refinery utilises its raw material
a few. completely. The real challenge will be to find the product
Table 2 points towards the large variety of raw materi- spectra with the highest overall added value for every raw
als available for utilisation in chemical industry. All these material and the process networks that generate them.
raw materials (and many more, depending on the specific • Reducing energy demand and adapting to solar energy pro-
regional agricultural system as well as industrial structure vision.
in question) have in common that they have either a well As fossil resources become expensive, global warming
established and cheap harvesting method or that they are becomes a serious consideration and biogenic resources
become increasingly sought after the chemical sector has to
adapt his energy demand accordingly. By and large chemi-
Table 2 – Examples for “new biogenic raw materials” for
cal industry has been at the forefront of increasing energy
the chemical sector in future
efficiency in its processes. Nevertheless energy saving will
Raw material category Material
remain an important agenda for chemical engineering in
Underutilised crops/resources Gras the future.
Algae Almost all integrated utilisation concepts for renewable
Sugar beets resources have one or more byproducts that may be used
Residues from agriculture/forestry Low quality forest residues to provide energy. Chemical processes will increasingly
Straw from corn, cereals, become intertwined with energy provision, as the exam-
oil seeds, . . . ple of the Green Biorefinery shows. The challenge here
Corn cobs will be to find the right pathways to utilise the energy
Leafs from beets, potatoes,
provided by these processes. One possible bottleneck here
...
Cuttings from wine yards,
is the combined provision of heat and power wherever a
orchards, . . . byproduct is thermally utilised. Power demand will def-
initely increase at a higher rate than demand for heat.
Residues from industries Tallow
This means that one of the major challenges for chemi-
Slaughterhouse residues
Oil seed cake cal engineers in the future will be to find interesting and
Dried distillers grain rewarding ways to sell heat that may be generated by their
Pomace processes.
Tanning residues In many cases though chemical processes will still demand
Residues from society Organic municipal waste more energy than they generate. Cheap energy in future
Garden cuttings will be linked to direct utilisation of solar energy. This
Used vegetable oil will require either energy storage or adapting processes to
324 process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327

Fig. 1 – Flow sheet of a “Green Biorefinery” (Mandl et al., 2006).

the time-dependent provision of thermal or photovoltaic calorific value (as a measure of the useful content) and the
energy (Müller et al., 2004). moisture content of some biogenic raw materials compared
to light fuel oil. It is evident from this table that with biogenic
2.2. Logistical optimization of processes resources transport becomes a major issue: transport vehi-
cles use less of their capacity (as the densities are low) and a
Fossil resources are typical “point” resources, meaning that considerable part of the load is water that is of no use in the
they are extracted in a small geographical area (the coal mine, process.
the oil or gas field) far from areas of consumption and then The low transport densities indicate that the usual mea-
transported to refineries and finally to the consumers. Con- sure of “ton-kilometer” is no longer applicable as the limiting
trary to that, biogenic resources (as well as almost all other factor for transportation is no longer weight but space. An
renewable resources based on solar radiation) are typical “dis- illustrative picture of the problem is shown in Fig. 2, where the
persed” resources, meaning that they are provided by large energy to transport 1 MJ (as a measure of the useful content of
swathes of land with a relatively low productivity per area unit. a certain raw material) is shown.
This means that they have to be collected, possibly refined This figure shows two important facts: transport with ships
and then transported to production sites. From these sites the (ship 1 denotes river ship and ship 2 stands for ocean going
resulting products will be transported to retailers and con- ships) still gives insignificant energy demands for transporta-
sumers. tion when medium dense renewable resources like corn are
In the case of fossil resources logistics are much the same transported. The transport of low-density raw materials like
for any point on earth, meaning that logistics do not play any straw or even wood pellets with tractors (e.g. from the farm
formative role for the process industry. This is however very to a processing site) or trucks however uses large amounts of
different in the case of biogenic raw materials: not only differ energy. In order to highlight this even more one may suppose
the raw materials depending on regional natural endowments; an efficiency to convert biogenic raw materials to transport
their transport requirements are also complex and divers. fuel of 30%. If the processing plant is 60 km from the farm, this
One major problem of many biogenic resources is their means that the transport already uses up 6% of the content of
relatively low transport density, paired with relatively high the raw material!
moisture content. Table 3 summarises the densities, the

Table 3 – Logistical parameters for different biogenic raw

materials
Material Humidity Calorific Density
(%, w/w) value (MJ/kg) (kg/m3 )

Straw (grey) 15 15 100–135

Wheat 15 15 670–750
Rape seed 9 24.6 700
Wood chips 40 10.4 235
Split logs (beech) 20 14.7 400–450
Wood pellets 6 14.4 660
Fig. 2 – Energy to transport 1 MJ energy content of biogenic
Light fuel oil 0 42.7 840
raw materials 1 km.
 process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327 325

With this in mind it becomes clear that transport logistics vide for recycling of nutrients to the grasslands, fields, forests
become a shaping factor for process structures in the future. and aquatic systems which yield the resources utilised in
This is all the more evident when considering that there is not chemical processes. This requirement will profoundly influ-
only the necessity to collect the raw materials but also to redis- ence the choice of technologies, the structure of the process
tribute possible residues like biogas manure or ashes from network transforming raw materials to products and even the
combustions back to the fields in order to maintain the fer- choice of the right size of chemical factories.
tility of agricultural land. Again this usually means transport One of the major misunderstandings in this respect is
of low-density goods and/or goods with high water content. that all processes that use biogenic sources are automatically
All this boils down to new process network architecture for “green” and sustainable. An illustrative example for the pit-
utilising biogenic raw materials: falls of applying old design approaches to a new framework
is shown in Fig. 3. This figure shows the ecological footprint
for the provision of various fuels calculated with the Sus-
1. harvest and separate industrially interesting residues
tainable Process Index (Narodoslawsky and Krotscheck, 1995;
(corn, straw, corncobs, leaves, etc.);
Krotscheck and Narodoslawsky, 1996). This index calculates
2. pre-process, compact (and possible store) raw materials
the area necessary to embed a process sustainably into the
close to the farms in order to obtain transportable interme-
ecosphere. The SPI takes raw material provision (differenti-
diates; use possible energy surplus (e.g. from biogas plants)
ated between renewable, fossil and mineral resources), energy
locally or provide to transport grids (gas and electricity);
provision, durable means of production and emissions and
return valuable substances as fertilisers to the fields;
wastes into account. Fig. 3 compares on well-to-wheel base
3. transport intermediates to central processing units where
conventional fuels like gasoline and diesel with bio-ethanol
divers and valuable products are obtained that will then
production in different plant sizes as well as with different
enter global markets; utilise possible energy surplus for
technologies and biodiesel production on the base of different
other industrial processes or provide to transport grids (gas
raw materials using the SPI.
and electricity).
This figure shows that fossil fuels exert the largest pressure
on the environment (the two left bars in Fig. 3). The differences
3. Life cycle responsibility in fuels based on biogenic raw materials however differ widely.
Bars 3–5 from left show the influence of different raw mate-
The ever louder call for environmental sustainability has a rials: bar 3 stands for biodiesel from fat (tallow) which is a
special meaning for chemical engineering: it is a key factor in byproduct of the rendering process of slaughterhouse waste;
the interaction between man and nature. The responsibility bar 4 stands for biodiesel from rape seed grown convention-
of chemical engineering will only increase as the raw material ally and bar 5 measures the ecological impact of biodiesel
base is switching towards a larger role for biogenic resources. from used vegetable oil collected from households and restau-
Through this switch the chemical industry is no longer just rants. It is obvious that the byproduct-based biodiesel has a
responsible for the environmental impact of its conversion lower ecological impact than the one based on conventional
processes. It becomes a main actor in utilising the natural agriculture. In the latter case, high pesticide and fertiliser
income, namely biogenic resources created by solar radiation requirements for the crop drive up the ecological footprint.
via the fertility of land and viability of oceans. This new role The lowest ecological footprint is achieved with biodiesel
burdens chemical engineering with at least a partial respon- from used vegetable oil, a typical biogenic waste from soci-
sibility to maintain fertility and viability of agricultural and ety. In this case the ecological pressure for generating the
natural systems. oil has already been allocated to the primary use as food;
In practical terms this new responsibility requires from the the only impact for the raw material provision is here the
chemical engineer to keep the quality of the environmental collection of the used oil. One can very easily see that
compartments soil, water and atmosphere intact and to pro- the new process network architecture derived in the pre-

Fig. 3 – Ecological footprint for different fuels (all bio-ethanol production alternatives on corn base).
326 process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327

vious chapter makes also sense from the ecological view plant, the higher the efficiency in converting the resources to
point. products and hence the lower the ecological impact.
Bar 6 shows the ecological footprint for biogas as a fuel. In Life cycle responsibility therefore poses completely new
this case the low input to generate grass (which is the base for questions to the chemical engineer. Besides reducing the
biogas in this case) is reflected in a very low ecological pressure ecological impact of the processes themselves, the chemical
for the whole fuel system. engineer has also to consider the logistics of obtaining the
The other bars depict ecological pressures for bio-ethanol raw materials and to ship residues back to fields and forests
production. Bars 7 and 8 measure the impact of conventional, in the right quality and quantity. On top of that the chemi-
medium scale plants (60,000 t/a ethanol production). The dif- cal engineer has to observe the economy of scale and balance
ference in this case is that bar 8 factors in the sale of DDGS it against the “ecology of scale” that may in many cases run
(dried distillers grain with solubles) as a product, which con- counter to the former.
sequently bears a part of the ecological pressure according to
the revenue obtained by selling it. The market for this prod- 4. New methods for new challenges
uct however will become increasingly narrow as bio-ethanol
capacities grow all over the world. In general, it can be seen New challenges require new tools to tackle them. Two tools
that by switching to biogenic resources without changing will come increasingly in demand if one follows the argument
the process structure a moderate reduction in the ecological of this paper that major challenges for chemical engineering in
impact of fuel systems can be achieved (approximately 30%). the 21st century will be the change in the resource base and a
This reduction is however far from the necessary dramatic much larger and formative role for considerations of sustain-
reduction called for in the future. able development: process synthesis and ecological process
Inspection of the other bars reveals some interesting evaluation.
insight to where the future of chemical industry may lay. Without going into detail on these two tools on which a
They are grouped into different technological alternatives at large body of literature already exists, we will only highlight
different scales, from 1000 to 5000 to 10,000 t/a ethanol pro- some requirements that these tools will have to satisfy to help
duction. Bars 9–11 show the impact of an ethanol pant, where bring about sustainable processes.
all residues from the raw material (corn) and the necessary
crop rotation are fed into a biogas unit that provides process 4.1. Process synthesis for integrated production
heat as well as electricity that may be sold. Bars 12–14 stand networks
for an alternative, where a biogas unit is fed by DDGS to pro-
vide process heat for the ethanol production. Bars 15–17 show Process synthesis has a long history in chemical engineer-
the ecological impact of a process where straw from corn is ing and is currently mostly employed for process integration,
utilised as a heat source for the bio-ethanol production and process intensification and optimisation tasks. If however
bars 18–20 show the footprint of a plant that again uses DDGS renewable resources become a major raw material base for
in a biogas unit that also produces electricity with the surplus chemical industry we will face a wholly different task: design-
energy. ing new plants with new and possibly untested technologies.
All these bars from 9 to 20 show processes that supply If we look at the requirements for process synthesis under
their own energy from locally provided biogenic sources (with these considerations we can see the following aspects:
the exception of bar 12, where the chosen source does not
supply enough energy). What can be seen clearly is the dra- • Rendering results with fuzzy technology data.
matic difference between small-scale plants entirely based on There is a clear time pressure to come up with viable
renewable resources and processes (bars 7 and 8) that use solutions for the utilisation of renewable resources as the
biogenic raw materials however supply their process energy environmental concerns become more serious and the
still by conventional fossil sources (in our case natural gas). It prices for fossil resources skyrocket. Although there are
must be stated here that the provision of biogenic energy car- many technology ideas in the research pipeline, there is a
riers from the residues of harvesting the main crop for large distinct problem in finding viable production networks: sin-
plants is difficult as the transport intensity becomes a severe gle processes alone will not be competitive with (still cheap
problem. and well optimized) fossil competitors and production net-
Within the “sustainable alternatives” we still can discern works that may successfully spread the costs for (expensive)
some interesting differences. Note that for bars 9–11 the trend renewable resources over more products require complex
concerning the ecological footprint as a function of the scale and possibly spatially dispersed process architectures. In
of the process is reversed to the rest of the cases. This alter- order to offer support in this situation process synthesis
native (biogas unit that utilises all biogenic material available) tools must generate optimized process structures on the
actually shows the least ecological footprint, due to the fact base of data that are still based on laboratory-scale research
that it produces a large amount of electricity and that there- and simulation.
fore the ecological impact is shared by different products. In • Integrating transport and plant sizing.
this case transport has a strong influence on the footprint, Transport will become a major factor shaping the architec-
especially as the biogas manure has to be transported back ture of process networks on the base of renewable resources.
to the fields. This means that the larger the plant, the longer This requires that process synthesis tools will have to inte-
the transport and hence the higher the ecological impact. This grate transport aspects into the optimisation of process
technology is clearly interesting, however only in very small structures.
scale. An important problem in this respect is to find the right size
For the other alternatives transport plays a decidedly and the right geographical distribution of different parts of
smaller role, as smaller amounts of residues have to be trans- the process network. The 21st century will see dispersed
ported back to the fields. This clearly means that the larger the interlinked process networks, the time of the chemical plant
 process safety and environment protection 8 6 ( 2 0 0 8 ) 321–327 327

as we have known it will possible come to an end. Process 5. Conclusion and discussion
synthesis must give the answers to the construction of these
networks, based on technology insight, the insight into the The 21st century will pose new and formidable challenges
agrarian system and the logistical framework in a certain to chemical engineering: a change in the raw material base,
region. increasing environmental considerations and the necessity to
• Integrating time dependencies and scheduling problems. apply new methodological approaches. This century will how-
Another important problem linked to renewable resource ever also bring new and increased importance to chemical
utilisation will be the time-dependent availability of certain engineering. It will penetrate into still more industries like the
raw materials. This means that process synthesis will not electronic industry, the pharmaceutical industry and biotech-
only have to deal with spatially dispersed process networks nology. It will also increase its importance for other industrial
but will also deal with scheduling problems of adapting pro- sectors, namely agriculture and food production.
cess chains to varying raw material supplies over a year. This paper concentrated on one plausible pathway for
Halasz et al. (2005) have dealt with these requirements to chemical engineering, namely a more prominent role of
process synthesis tools. This paper shows what strong sup- renewable resources. Although this is a plausible line of devel-
port process synthesis can deliver to the tasks of chemical opment, it is by no means the only possible way for chemical
engineering. It shows however also how much still has to engineering in this century: contenders that may be as plau-
be done in this field. sible include an industrial system more dependent on coal
and/or alternative fossil carbon sources such as tar sands and
4.2. Engineering compatible ecological process oil shale. Nuclear energy may also play a certain role in future
evaluation energy systems. Although such a future will be dramatically
different from that sketched in this paper the challenges for
Life cycle assessment has become a versatile tool to report chemical engineering will be strikingly similar: a change in the
the ecological aspects of production in many fields. The future raw material base, a different logistical situation and possible
task of chemical engineers, however, is to construct process re-adjustment of the process structures to the requirements
networks from scrap that are sustainable. There is a marked of the new resource systems.
difference between tools that are used for reporting purposes In the light of challenges and chances of future develop-
compared to those that an engineer may use to construct and ment we must adapt. Chemical engineering has long been a
optimise a chemical process. The following aspects may help thoroughly technical discipline with a strong interdisciplinary
to guide the development of “engineering compatible” tools streak. This base will help us to integrate even more systemic
that are still scarce: methodology and to acquire the necessary social skills to deal
with new partners from agriculture to logistics to environmen-
• Impact aggregation. tal sciences and regional development.
Chemical processes have diverse impacts on the environ-
ment, however, engineers need to balance these impacts References
against each other in order to optimise processes: in the ever
increasing number of cases engineers have already created Halasz, L., Povoden, G. and Narodoslawsky, M., 2005, Resour
highly efficient processes so that a reduction of one pres- Conserv Recycl, 44: 293–307.
sure usually leads to an increase in another. This means Kromus, St., Narodoslawsky, M. and Krotscheck, Ch., (2002). Grüne
that engineers need tools that aggregate different impacts Bioraffinerie—Integrierte Grasnutzung als Eckstein einer
in a logical and scientifically sound way in order to discern nachhaltigen Kulturlandschaftsnutzung, Berichte aus Energie- und
Umweltforschung (BMVIT, Vienna/A).
between ecologically better and worse alternatives.
Krotscheck, C., 1997, Environmetrics, 8: 661–681.
• Flow sharp resolution of environmental pressures. Krotscheck, C. and Narodoslawsky, M., 1996, Ecol Eng, 6: 241–258.
Chemical engineers deal with material and energy bal- Mandl, M., Kromus, St., Koschuh, W., Boechzelt, H.,
ances as their main tool in conceiving and optimizing Narodoslawsky, M., and Schnitzer, H., 2006, Process Synthesis
processes. It is therefore necessary for engineers to have a Tool for Biorefineries, Lecture at the Biorefinica,
tools at hand that measure the impact of each and every Osnabrück/D.
flow the process exchanges with the environment. This Müller, T., Weiß, W., Schnitzer, H., Brunner, C., Begander, U. and
Themel, O., (2004). Produzieren mit Sonnenenergie Berichte aus
information is essential to discover “ecological hotspots”,
Energie- und Umweltforschung (BMVIT, Vienna/A).
meaning raw materials, products, emissions or wastes Narodoslawsky, M. and Krotscheck, C., 1995, J Hazard Mater, 41:
that exert a disproportionate ecological pressure. Only 383–397.
through this knowledge can the engineer focus on fix- Schindler, J. and Zittel, W., (2000). Fossile Energiereserven und
ing the real problems and avoid dealing with second-rate mögliche Versorgungsengpässe, Studie für den Deutschen
impacts. Bundestag. (LB-Systemtechnik, Ottobrunn/Germany).
Siirola, J.J., 2007, Sustainability in the Chemical and Energy
Industries, Plenary Lecture NASCRE-2 Merriot Hotel, February
An interesting overview for the possible application of dif-
4–8, Houston/TX.
ferent highly aggregated environmental evaluation measures Walker, W.H., Lewis, W.K. and McAdams, W.H., (1923). Principles of
to engineering is given by Krotscheck (1997). Chemical Engineering. (McGraw-Hill, New York).