Figure 1. Material flows during the production of RDF
[7]
MARKUS
HIEBEL, ASJA MROTZEK, VOLKMAR KEUTER
Abstract: Material flow management is a method to compare different choices of
action by their ecological and economic effects. This article describes the
method and the possibilities to manage material flows in waste and wastewater
management systems. Aims and the procedure how to deal with waste flows in
waste management networks are described. The example of the production of
refuse derived fuel is given.
The method of material flow management has been applied to the material
flows and environmental aspects looking at the example of foundries.
I. INTRODUCTION
The management and the knowledge
of the different material flows is a standard procedure in industrial
processes. In environmental questions the material flow management is discussed
since 1972 after publication of the report “The Limit of Growth” [6]. Energy
and material flow models of this report show under unaltered global
circumstances dramatic consequences for mankind. So the main goal of the
sustainable development is to reduce the use of primary resources and energy as
well as a reduction of emissions into the environment.
Sustainable development is
based on three pillars:
·
economic
criteria
·
ecological
criteria
·
social criteria
These
criteria have to be weighted for a sustainable decision between different
action alternatives.
II. GOALS AND TOPICS
Material
flows are part of a defined system with one or more processes affecting the
material flows. On the one hand these processes can be transport processes
changing the place of the material flow but not the material flow itself.
Otherwise there are processes which affect the material flow directly (e. g.
the composition or state of aggregation of a substance). The material flow
system can be described with scientific-technical parameters but it has to be
connected with economic, ecological and social criteria to evaluate and optimize
the material flow system.
The
following requirements are relevant for material and energy flow analyses [3]:
·
the use of
renewable resources must not exceed their quotas of regeneration
·
non-renewable resources
should only be used to the extend that adequate alternatives are created
·
emissions in
the environment should be adapted to the capacity of environmental media
·
anthropogenic
interferences should respect relevant natural reaction cycles
·
avoidance of
risks and dangers for human health
One
example for that is the choice of treatment alternatives for wastes. Questions
are: Is it better to incinerate the waste or should we better use composting,
fermentation or recycling options? This choice is influenced by the market
price, availability of treatment options, the environmental effects on the
different media (soil, water and air) as well as the effects on the population
(disamenity effects). The participation of the population is crucial while
planning waste treatment facilities like landfills or incineration plants. If
there are missing treatment installations it is possible to separate the waste
into its different fractions. This is done for trade waste and leads to the
production of a refuse derived fuel (RDF) with a high quality standard and to
the production of a middle calorific fraction. The RDF can later be transported
and efficiently incinerated in co-combustion processes like cement kilns or
coal-fired power plants. The next figure shows the material flows entering and
leaving a RDF-production plant.
The
German waste management act (closed substance cycle waste management act) takes
environmental aspects into consideration. It proposes a waste hierarchy giving
priority to waste minimization, recycling and recovery. Disposal of waste on
landfills is the last option. The law does not recommend methods which could be
used to take the “right” decisions to choose the waste treatment options to
reach the aims (minimizing environmental impacts and economic costs). The
method of material flow management as one solution will be explained in the
following.
Figure 1. Material flows during the production of RDF
[7]
III. METHOD
The
first step is the abstraction of the industrial processes which consists of
different specific transfer and transformation steps. Here it is necessary to
chose representative processes e. g. for the collection and the treatment
of waste. It is also necessary to look at the benefits of recovery
possibilities (avoidance of landfilling, substitution of material production or
energy generation). Therefore it is very important to clearly define the system
boundaries. After these steps, the processes have to be described with their
input and output flows (energy and material requirements, emission etc.).
Environmental effects can be weighted e. g. with factors like global
warming potential or ozone depletion potential. These effects can then be
resumed in impact categories like green house effect or acidification.
Figure 2. Structure of foundry model [acc. to 2]
Apart
from the ecological dimension which is described by the inventory balances of
the processes, it is also necessary to look at the economic treatment costs and
benefits.
After
the description of the material flows and the processes in the network their
costs and benefits can be calculated. There are of course challenges how to
valuate the single dimensions (social, economic and ecological issues).
The
system theory allows the “zooming” into the processes. That means that it is
possible to look at the whole network or to look at single processes so that an
optimization is possible at different levels.
IV.
CASE STUDY: VIETNAMESE FOUNDRIES
Casting of metallic
substances belongs to the so-called primary shaping technologies, where
substances are transferred directly from the formless liquid state into a
defined formation. Metals are transferred into a liquid state by smelting and
casting molds are produced.
The main issue of the material and energy balances in foundries is the
development of a complete and consistent input-output analysis. In
consideration of the production specific correlations of resources, products,
residues and emissions all necessary inputs and outputs are determined.
Therefore all present operational data had been evaluated and later checked in
a systematic analysis for integrity and consistence. Missing data have to be
completed by measurements, calculations or assumptions [5].
Figure 3. Example
of material flow analysis in Vietnamese foundry
Complete data collection might lead to so far hidden environmental
impacts such as dissipative heat, diffuse material emissions and water
leakages.
Within the Integrated Water Resources Management (IWRM) project “Vietnam
Water” material and energy balances had been conducted in industrial areas in
the Northern Province of Nam Định. Basis for this activity is that the river
water in this province does not meet the Vietnamese standard for fresh water
quality. The river water quality is decreasing seriously also by untreated
sewage from agriculture [1]. In handicraft villages as the village Tống Xá
channel water is loaded especially with different heavy metals and cyanides,
exceeding the limits by up to 50 times [4].
Since January 2007 scientists from the
The sampled data from the foundries were defined, sorted and analyzed by
Fraunhofer UMSICHT. First results of the investigation are presented in Fig. 3
and 4. The next steps are the comparison of these data with the existing
foundry model (cp. Fig. 2) and also with existing foundries in
Table 1. Well-investigated
foundries in Tống Xá
|
Company |
Estate
area (m2) |
Total
staff |
Living
on site |
Production
|
Total
energy consumptoin (MWh/a) |
Specific
energy consumption (MWh/t) |
|
1 |
2080 |
67 |
17 |
2200 |
6895 |
3 |
|
2 |
1150 |
29 |
4 |
300 |
9360 |
31 |
|
3 |
1600 |
30 |
2 |
750 |
2020 |
3 |
|
4 |
1150 |
27 |
6 |
200 |
425 |
2 |
|
5 |
1100 |
31 |
2 |
300 |
720 |
2 |
|
6 |
1400 |
32 |
1 |
400 |
600 |
2 |
|
7 |
1150 |
31 |
2 |
250 |
648 |
3 |
|
8 |
720 |
35 |
10 |
300 |
55 |
|
|
9 |
1000 |
42 |
9 |
n/a |
900 |
|
|
10 |
800 |
23 |
8 |
720 |
2581 |
4 |
|
11 |
1000 |
24 |
3 |
n/a |
2040 |
|
|
12 |
660 |
42 |
7 |
180 |
301 |
2 |
|
13 |
n/a |
n/a |
n/a |
760 |
7536 |
10 |
V. CONCLUSION
The idea of material flow
management is a promising concept to deal with the challenges of waste
management. It takes issues of the sustainable development into account and it is
a flexible instrument which can be used for different tasks.
Material and energy flow
management has been successfully applied to different industrial sectors. In
the IWRM project it will help to detect hidden environmental impacts as unknown
contaminated water flows and economization potentials.
Acknowledgements
The authors would like to
thank the German Federal Ministry of Education and Research which is funding
the project “IWRM - Vietnam Water” under the Reference No. FKZ 02 WM 0767.
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