Carlos E. Escobar Toledo*, Lol-chen Alegría*, Bárbara Ramírez*

1. 34th IAEE International Conference. Institutions,Efficiency and Evolving Energy TechnologiesStockholm, June 19 - 23, 2011 ON EXERGY AND SUSTAINABLE DEVELOPMENT: SOME METHODS TO EVALUATE ENERGY EFFICIENCY AND NON-RENEWABLE RESOURCES WASTE WHEN USING SOME PLASTICS. Carlos E. Escobar Toledo*, Lol-chen Alegría*, Bárbara Ramírez* Departamento de Ingeniería Química. Facultad de Química Universidad Nacional Autónoma de México *We thank to PAPIIT project number IN102710.

2. ABSTRACT • This paper explores the role of energy utilization in sustainable development and the potential sources to increase energy efficiency*. • It also deals with the exergy analysis of plastic materials used for the manufacture of a lot of stuff used in our day-to-day life. *This work follows Dewulf J. (2004)’ same concerns

3. ABSTRACT • Results of some plastics- short life uses, are presented considering the proposed methodology and the utilization of Multicriteria decision making to decide among possible substitutes more exergy and energy effective.

4. FRAMEWORK From scientific point of view, it deals with exergy analysis of plastic materials used for the manufacture of some stuffs along its life cycle, including all the manufacture chains. • The same analysis is applied for other products can be used to substitute those materials.

5. FRAMEWORK • For decision making aid, multi-criteria analysis is used for each alternative/case during the total life cycle (LCA); the criteria are: the Exergy loss (Irreversibility) (1), together with real quantity of energy used in the manufacture processes (2), the material balance including the quantity of resources, renewable or not, (3), emissions of Greenhouse gases in the life cycle (4) and an economic measure (5).

6. OBJECTIVES • The main hypothesis is that the efficient use of energy, to avoid energy and raw material waste, are essential for long-term global sustainability. • With this framework, plastic disposable grocery bags and bottles for individual use, are analyzed to asses if those items are efficient on the energy efficiency viewpoint, considering also pollution and waste problems, within their full life cycle. • During production of those items, a waste of non renewable resources and Green House Gas (GHG) emissions are present. • There are also different materials or ways to use plastics getting longer use life cycle, saving energy and avoiding pollution, using technology-driven sustainability without wasting non renewable resources and energy.

7. SUSTAINABILITY AND TECHNOLOGY Since the Brundlandt report on sustainability for the United Nations in 1987, sustainability is a multidisciplinary topic: • It Includes technological challenges in products and processes, in such a way that developed technology has to guarantee the delivery of goods and services in a manner that does not endanger the possibilities of future generations.

8. METHODOLOGY FRAMEWORK Material and Energy Balance * Resources Extraction, production, distribution of manufactured goods and disposal (“From cradle to grave”). Material and Energy Balances Process /product information Natural Resources Conservation Natural resourcesconservation Sustainable Development Sustainable development Exergy Balance EXERGY balance Air Emissions Life Cycle Assessment* Life Cycle Assessment* GHG Emissions Efficient use of energy. Efficient use of energy Economic analyses of Alternatives Economic Analyses of Alternatives

9. Gather information • Production Processes • Thermodynamic variables • Production costs Added Value or cost/profit computation Life cycle definition ENERGY balance EXERGY balance MATERIAL balance S Irreversibility Crude oil Equivalent Crude oil Equivalent Crude oil Equivalent GENERALMETHODOLOGY GHG EMISSIONS MULTICRITERIA SELECTION

10. MethodsExergy and energyanalyses • An Exergy balance, from which the irreversibility rate of a steady flow process can be calculated, is derived by combining the steady flow energy equation (First Law) with the expression for the entropy production rate (Second Law). • Exergy is then, defined as the maximum work potential of a material or of a form of energy in relation with its environment. Where: • H,S = Enthalpy and Entrophy evaluated at non-equilibrium state • H0, S0 = Enthalpy and Entrophy evaluated at equilibrium state • T0 = reference Temperature Ex= DH-T0DS = (H-H0) – T0(S-S0)

11. Exergy is divided mostly in two streams: physical Exergy and chemical Exergy. Physical Exergy Chemical Exergy T P X T0 P0 X T0 P0 X1 T0 P0 X0 T P0 X Mechanical Exergy Thermal Exergy Reactional Exergy Concentration Exergy For the majority of natural resources, chemical Exergy is the most important contribution to its exergetic value.

12. EXERGY LIFE CYCLE ANALYSIS • On basis of the life cycle approach in combination with Exergy analysis, a method is developed, called the Exergetic Life Cycle Analysis (ELCA). • The irreversibility during the complete life cycle allows to evaluate the degree of thermodynamic perfection of the production processes and to conduct the assessment of the whole process chain (Cornelissen, 1999).

13. Definition • For the purpose of this presentation, plastic bags are defined as supermarket and retail shopping bags. • The functional unit (f.u.) for grocery bags are: Reusable bags: a repeated use of 300 times 900 plastic bags (with or without additives) 675 paper bags And in the case of PET bottles: 1 Kg (26 bottles of 1 Lt)

14. Problem Dimension in Mexico The consumption of H&LDPE’s are 600,000 Ton/year. Then, grocery bags consumption is 107,100 millions/year, considering 900 grocery bags are equivalent to 5.04 Kg, average. Only 5% of them are recycled According of “Centro Empresariaal del Plástico”, in 2009 PET bottles consumption, were 375,360 ton (9,700 millions bottles). PET bottles post consumption that are disposed are 7.8 billions/year.

15. RESULTS • Polyehtylene production: Considering 900,000 Ton/year, the grocery bags consumption is 160,000 millions, it signifies 19,000 barrels/day of crude oil equivalent of the exergy “disposed” in one year,representing an exergy loss of 1’492,937 bpce/year and 149 millions US$/year (with a crude oil price 100 US$/barrel. Ethylene was obtained from light naphtha by conventional cracking/front-end deethanization, LDPE was produced by a high pressure process, autoclave reactor. We obtained a total of Exergy losses of 244 MJ/f.u. (including emissions), for the Polyethylene production chain.

16. ENERGY AND MATERIAL BALANCES OF ONE functional unit THROUGH ITS LIFE CYCLE. • From PE material balance, we have 0.207 crude oil barrels/PE bags (f.u.), equivalent to 17.46 US$/f.u., taking an export price of crude oil of 84.4US$/bl. • From the energy balance, we obtained 110.63 MJ/PE bags (f.u.); that quantity and considering a crude oil heat value of 6263.6 MJ/bl, equals to 0.0176 barrels of crude oil per f.u. or 3.5 bl/ton PE. • Considering 160 billions bags consumed/year, it is equivalent to dispose into the landfill 4,754,2612 US$/day (!).

17. EXERGY BALANCE FOR ALL THE ALTERNATIVES • The production of unbleached Kraft paper wastes the highest quantity of Exergy, which represents a much more relevant input than PE bags from the view point of Exergy consumption. • The production of polyethylene bags with an oxo degradant additive has the highest Exergy embedded on emissions. • It is clear that the production of 1 polypropylene bag that is equivalent to the use of 900 PE bags, involves the lowest losses of Exergy.

18. Results

19. Partial ranking Total ranking

20. Alternatives with the highest priority. Exergy Diagram for LCA of one grocery bag made from polypropilene

21. PET Life Cycle Assessment • Functional Unity • “To Contain and transport 26,000 liters of water to drink” • The flow of reference corresponding to materials under study is: 1 Ton. of PET = = 2.31 Ton. of Al 14.84 Ton. of glass 1Kg PET = 26 bottles of 1 liter

22. Primary production of PET bottles. Other products and fuels Terephthalic Acid Mixed Xylenes REFINERY p-xylene CRUDE OIL Dry Gas (CH4) Propane n-butane iso-butane n-pentane iso-pentane Hexane PET Blow process WETNATURAL GAS CRYOGENIC PLANT • EthyleneÓxyde Ethylene Ethylenglicol Ethane

23. Primary production of glass bottles. SiO2 RAW MATERIALS Na2CO3 Glass bottles Melting CaCO3 Feldespato Primary production of aluminum cans. NaOH Bauxite Coke Hall-Heroult Process RAW MATERIALS Bayer process Cans CaO Na2CO3

24. PET PRODUCTION CHAIN Atmospheric emissions 27569 MJ CRUDE 674716 MJ Xylene 34386.11 MJ p-Xylene 26545 MJ Terephthalic Acid 18122 MJ PET 23705 MJ Methanol 1083.75 MJ Diethylene Glycol 786 MJ Ethylene 10843 MJ Ethylene Oxide 6563MJ Ethylenglycol 6553 MJ NATURAL GAS 45115 MJ Ethane 13799 MJ Crude Ethylenglycol 334 MJ EXERGY, ENERGY AND MATERIAL BALANCES OF ONE TON (36,000 bottles) OF PET THROUGH ITS LIFE CYCLE.

25. Results for virgin and recycled materials (MJ/fu) PET GLASS AL PET GLASS AL PET AL GLASS

26. Data to Decision Lab

27. Multicriteria Results PROMETHEE II Ranking (primary and secondary Four criteria used: a) Irreversibility (MJ/u.f.), weight: 30% b) Energy (MJ/u.f.), weight: 30% c) Atmospheric Emissions (Kg. de CO2 eq/u.f.), weight: 30% d) Profit ($/u.f.) 10% weight Only primary Only secondary Primary & secondary

28. CHEMICAL RECYCLING OF PET PET RECYCLING (MAINLY CHEMICAL) IS A VERY IMPORTANT ALTERNATIVE TO ANALYZE. (*) To obtain the same product.

29. CONCLUSIONS According to the ranking obtained in PROMETHEE Software, the bags made from Propylene and Cotton are the best material based on the criteria considered (Irreversibility, real energy, mass balance, and unit product value). The exergy analysis shows that the PET recycling process is an important option in the waste disposal since the additional exergy required is only 4.70 MJ/Kg. Also products obtained trough de recycling process are of sufficient quality to be used again in the production of PET.

30. CONCLUSIONS • Exergy Analysis is a good measure to get a sustainable development. It is then, a very useful tool, which can be successfully used in performance evaluation of waste materials with a very short life cycle. • Exergy losses provides not only a measure of both, the energy availability and resource depletion but it is also the most suitable criterion to improve the technological efficiency of the industrial production system. In this way, the Exergy analysis, associated with the energy and mass balances, represents an important advancement in the multi-criteria analysis of products. • The analysis of different alternative materials for the manufacturing of retail shopping bags showed how the selected production processes accounted for Exergy destruction and therefore to resource depletion.

31. THANKS!