Multi-Objective Synthesis of a Company’s Supply-Network by Accounting for
Several Environmental Footprints
Annamaria Vujanovića, Lidija Čučekb, Bojan Pahora, Zdravko Kravanjab,*
Perutnina Ptuj d.d., Potrčeva cesta 10, 2250 Ptuj, Slovenia
Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17, 2000
Maribor, Slovenia
zdravko.kravanja@um.si
a
b
Published in Process Safety and Environmental Protection (2014), Volume 92, Issue 5, Pages 456-466
Summary
This contribution presents the multi-objective synthesis of a company's supply network by integrating
renewables (biomass and other waste, and solar energy) and accounting for several environmental
footprints. The synthesis is based on a Mixed-Integer Linear Programming (MILP) problem. A
previously developed model by the authors for achieving energy self-sufficiency by integrating
renewables into companies’ supply networks has been extended for the evaluation of environmental
impacts, such as energy, carbon, nitrogen, and water footprints. The achievement of an energy selfsufficient supply network has been considered whilst significantly reducing environmental impacts.
The presented model is applied to multinational poultry-meat producing company. Direct (burdening)
and indirect (unburdening) effects that form total effects on the environment are considered for the
evaluation of environmental footprints. The results showed significant unburdening of the
environment in terms of carbon and nitrogen footprints but, however, higher burdening in terms of the
water footprint.
Background
Nowadays, industries started planning and designing their activities in a way to minimize negative
environmental impacts due to environmental control costs and regulations (Tokos et al., 2013). The
maximization of the profit is still the main intention of companies, whilst the second objective is
becoming the decreasing of environmental burdens. There is, therefore, a need for multi-objective
optimization (MOO) (Kiraly et al., 2013a) to make the best decisions from several viewpoints.
More and more companies have started to utilize accessible alternative energy sources that are
available within nearby regions, to apply them in more efficient ways, such as e.g. biomass for biogas
production within anaerobic digestion, and photovoltaics (PV) (Graebig et al., 2010). The usage and
environmental footprints of fossil-based power generation will need to be reduced especially for
mitigating climate change (Eslick and Miller, 2011) and for improving the quality of the environment.
Reducing the footprints is amongst the goals for achieving better sustainability. Several footprints are
introduced for the environmental impacts assessments, such as carbon – CF, water – WF, nitrogen –
NF and others (Čuček et al., 2012).
Aims
In this study several environmental impacts are evaluated for utilization of the produced biogas and
installed PV-panels for heat and power generation. Several footprints are considered such as CF, NF,
WF and energy footprint (EF). All these footprints consider burdening and unburdening effects
(Kravanja, 2012) and therefore those alternative energy production technologies could be selected that
Suggested citation: Vujanović, A., Čuček, L., Pahor, B., & Kravanja, Z. (2014). Multi-Objective
Synthesis of a Company's Supply-Network by Accounting for Several Environmental Footprints.
Process Safety and Environmental Protection, 92(5), 456-466.
exhibit significant unburdening capabilities and have the more positive total effects. The relationships
between different footprints are also investigated.
The main objective of this work was to perform the multi-objective synthesis of a company’s supplynetwork by integrating renewables in order to achieve an energy self-sufficient supply-network whilst
significantly reducing environmental impacts. It was applied to a large-scale food industry, the main
activity of which is the producing of fresh meat and meat products. It also includes various renewable
energy production possibilities, such as reusing of the manure for electricity and heat production and
photovoltaic (PV) electricity production.
Methods
A multi-objective synthesis (MOO) of an industrial supply-network was applied to an existing largescale meat producing company. The industrial supply-network’s baseline includes one biogas plant
was taken into account and upgraded by integrating the potentially available renewable energy sources
within the nearby region, such as photovoltaic panels, animal and organic waste, and waste heat. The
rooftop surfaces of industrial objects located at different locations were used for electricity production
via PV panels. Due to the excess of accumulated manure as a side-product of the poultry industry,
additional potential locations were proposed for biogas and cogeneration plants. District heating of the
nearby settlements was proposed for low-grade heat produced from the additional biogas plants.
For the MOO, mathematical programming approach was used based on a MILP framework. The
synthesis was based on previous work by the authors (see Kiraly et al., 2013b) and had now been
extended in order to evaluate several footprints (EF, CF, WF and NF) originating from the company’s
supply-network and for multi-objective synthesis, where the main criterion was maximizing the
economic profit and the footprints are minimized as additional criteria. It should be noted that only
those footprints were accounted for that originated from the renewables’-based integrated supplynetworks (biogas and cogeneration plants, and photovoltaic panels), and from transportation. Total
footprints are considered representing the sum of burdening and unburdening effects.
Results
3
2.8
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
Relative total footprint
Relative direct footprint
MOO was applied to an industrial case study of an existing food industry’s network, which is spread
around its surrounding regional supply-network. The economic profit, direct, total and direct/total
footprints are assessed in regard to the installations of additional renewable energy-producing units.
Relative direct and total footprints vs. additional energy producing units are shown in Figure 1.
3
2.75
2.5
2.25
2
1.75
1.5
1.25
1
0.75
0.5
0.25
0
-0.25
-0.5
-0.75
Additional energy-producing units
Relative direct CF
Relative direct WF
Additional energy-producing units
Relative
directtotal
NF CF
Relative
Relative total WF
Relative total NF
Figure 1: Relative direct and total footprints vs. additional energy-producing units
Suggested citation: Vujanović, A., Čuček, L., Pahor, B., & Kravanja, Z. (2014). Multi-Objective
Synthesis of a Company's Supply-Network by Accounting for Several Environmental Footprints.
Process Safety and Environmental Protection, 92(5), 456-466.
The relative increase in direct footprints can be seen when installing new units. However from total
perspective production of renewable heat and electricity would, in general, reduce CF and WF and
bring unburdening in terms of these footprints. On the other hand, total WF would increase and that
would mean that the currently-used heat and electricity would have better impact on the environment
in terms of WF.
Figure 2 shows the effects on the environment of utilizing the renewables in terms of the relative total
CF, total NF, total WF, total EF (electricity-transportation and heat). These footprints are shown in
relation to the profit and newly-installed energy producing units. Certain footprints indicate that
unburdening surpasses the burdening of the environment and the break-even points can be shown at
zero relative total footprints.
1.045
Relative profit
1.04
FSP_PV
BREED3_PV
1.035
1.03
1.025
CHP3
CHP5
1.02
1.015
CHP4
1.01
1.005
1
-1.25
CHP1
-0.75
-0.25
0.25
0.75
1.25
1.75
2.25
2.75
Relative total footprint
Relative total WF
Relative total ELTRF
Relative total CF
Relative total HF
Relative total NF
Figure 2: Relative profit vs. relative total footprints
Acknowledgments
The authors are grateful for the financial support from the European Social Fund, the Slovenian
Technology Agency – TIA (PhD research fellowship contract No P-MR-10/89), the Slovenian
Research Agency – ARRS (programmes P2-0032 and P2-0377), and from the EC FP7 project
ENER/FP7/296003/EFENIS ‘Efficient Energy Integrated Solutions for Manufacturing Industries –
EFENIS’.
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Suggested citation: Vujanović, A., Čuček, L., Pahor, B., & Kravanja, Z. (2014). Multi-Objective
Synthesis of a Company's Supply-Network by Accounting for Several Environmental Footprints.
Process Safety and Environmental Protection, 92(5), 456-466.
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Suggested citation: Vujanović, A., Čuček, L., Pahor, B., & Kravanja, Z. (2014). Multi-Objective
Synthesis of a Company's Supply-Network by Accounting for Several Environmental Footprints.
Process Safety and Environmental Protection, 92(5), 456-466.