Multi-Objective Synthesis of a Company’s Supply-Network by Accounting for Several Environmental Footprints

Annamaria Vujanovića, Lidija Čučekb, Bojan Pahora, Zdravko Kravanjab,*

aPerutnina Ptuj d.d., Potrčeva cesta 10, 2250 Ptuj, Slovenia

bFaculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia

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 self-sufficient 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 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 supply-network 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 large-scale 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 supply-networks (biogas and cogeneration plants, and photovoltaic panels), and from transportation. Total footprints are considered representing the sum of burdening and unburdening effects.

Results

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.

Figure 1: Relative direct and total footprints vs. additional energy-producing units

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.

Figure 2: Relative profit vs. relative total footprints

Acknowledgments

The authors are grateful for the financial support from theEuropean Social Fund, theSlovenian Technology Agency – TIA (PhD research fellowship contract No P-MR-10/89), theSlovenian Research Agency – ARRS (programmes P2-0032 and P2-0377), and from theEC FP7 project ENER/FP7/296003/EFENIS ‘Efficient Energy Integrated Solutions for Manufacturing Industries – EFENIS’.

References

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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.