34th IAEE International Conference. Institutions, Efficiency and Evolving Energy Technologies Stockholm, June 19 - 23, 2011. ON EXERGY AND SUSTAINABLE DEVELOPMENT: SOME METHODS TO EVALUATE ENERGY EFFICIENCY AND NON-RENEWABLE RESOURCES WASTE WHEN USING SOME PLASTICS.
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.
*This work follows Dewulf J. (2004)’ same concerns
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.
Since the Brundlandt report on sustainability for the United Nations in 1987, sustainability is a multidisciplinary topic:
* Resources Extraction, production, distribution of manufactured goods and disposal (“From cradle to grave”).
Material and Energy Balances
Process /product information
Natural Resources Conservation
Life Cycle Assessment*
Life Cycle Assessment*
Efficient use of energy.
Efficient use of energy
Economic analyses of Alternatives
Economic Analyses of Alternatives
Added Value or cost/profit
Life cycle definition
Ex= DH-T0DS = (H-H0) – T0(S-S0)
For the majority of natural resources, chemical Exergy is the most important contribution to its exergetic value.
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)
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.
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.
EXERGY BALANCE FOR ALL THE ALTERNATIVES
Exergy Diagram for LCA of one grocery bag made from polypropilene
14.84 Ton. of glass
1Kg PET = 26 bottles of 1 liter
Primary production of PET bottles.
Other products and fuels
Dry Gas (CH4) Propane n-butane iso-butane n-pentane iso-pentane Hexane
Primary production of glass bottles.
Primary production of aluminum cans.
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.
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
Primary & secondary
PET RECYCLING (MAINLY CHEMICAL) IS A VERY IMPORTANT ALTERNATIVE TO ANALYZE.
(*) To obtain the same product.
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.