Exergetic Life Cycle Assessment

Ahmet Ozbilen, Ibrahim Dincer and Marc A. Rosen

July 2-4, 2012 Osmaniye, Turkiye

1

Outline

 Introduction  Life Cycle Assessment (LCA)  Exergetic LCA (ExLCA)  Case study  Conclusion 2

Introduction

   Life cycle assessment → Investigates and reduces the environmental impacts of a system or process or product  Awareness of environmental concerns increases ‘Greener’ products and ‘greener’ processes The concept of exergy in LCA approach   To identify and understand underlying reasons for many environmental impacts ExLCA identifies exergy utilization and destruction during the life cycle of a system or a product.

3

Life Cycle Assessment (LCA)

    LCA is used to evaluate total environmental impact of a product or process.

LCA is also conducted to decrease overall environmental impact and to identify environmentally critical phases.

Cradle-to-grave analysis (production, transportation, installment, operation, disposal).

Defined by ISO 14000 series.

4

Life Cycle Assessment (LCA)

Goal and scope definition Has four phases;   Goal and scope definition: Specifies objectives, boundaries Life cycle inventory analysis (LCI): Inventory data on energy and material flows   Life cycle impact assessment (LCIA): Evaluates environmental impacts of material and energy flows Improvement Analysis: Results, conclusions, recommendations and improvements Inventory analysis Impact assessment Improvement analysis Life cycle assessment framework.

Interpretation 5

Life Cycle Assessment (LCA)

 CML 2001 Impact Categories Environmental impact category Global warming potential (GWP) (kg CO 2 -eq) Ozone depletion potential (ODP) (kg CFC-eq) Eutrophication potential (EP) (kg phosphate-eq) Acidification potential (AP) (kg SO 2 -eq) Source: Adapted from (Guinee

et al

., 2002) Definition The impact of human emissions on thermal radiation absorption of atmosphere Thinning of the stratospheric ozone layer, which increases the amount of ultraviolet radiation reaching the Earth's surface Comprises all potential impacts of excessive levels of macronutrients The deposition of acidifying pollutants on soil, groundwater, etc.

6

Exergetic LCA

 Linkages between exergy analysis and LCA  ExLCA approach and methodology  Applications of Exergy & LCA  Advantages and benefits of ExLCA 7

Exergetic LCA - Linkages between exergy analysis and LCA

 Environmental impacts can often be decreased by reducing exergy reductions  Increase in exergy efficiency  Less resources (exergy)  Reduction in requirements associated with new facilities for the production, transportation and the distribution of the various energy forms 8

Exergetic LCA – ExLCA Methodology and Approach

 Goal and scope definition: Identical with LCA  Inventory Analysis: Mass and energy balances, simplified black box approach (not always)  Impact assessment: Determination of exergies of the flows, and the exergy destructions and efficiencies of the overall processes and its subprocesses.

 Improvement analysis: Intended to reduce the life cycle irreversibilities 9

Exergetic LCA – ExLCA Methodology and Approach

Raw material acquisition

Inputs for each stage

Materials Energy EXERGY Manufacturing

Outputs for each stage

Intended products Co-products and energy Emissions EXERGY Use/reuse/maintenan ce Recycling/waste management General flow diagram of ExLCA.

10

Exergy and LCA – Applications

        Daniel and Rosen, 2012 – Fuel cycles for automobiles Neelis et al., 2002 – Hydrogen production and storage systems for automotive applications Boyona et al., 2011 – Steam methane reforming process for hydrogen production Granovskii et al., 2007 – Hydrogen production using renewables Peiro et al., 2010 – Production of biodiesel from used cooked oil Beccali et al., 2003 – Plaster materials Carrado et al., 2006 – High-efficiency power plant for H 2 production - (the ZECOTECH cycle).

Dewulf et al., 2001 – Waste treatment plant 11

Exergetic LCA – Advantages

 Not only inputs and emissions, but also consider these quantities from the perspective of exergy.

 The depletion of natural resources is measured directly as a loss of exergy.

 Improving the efficiency of the systems and processes, so as to decrease their environmental impacts, is often aided more by ExLCA.

12

Case Study: ExLCA of a hydrogen production process.

Q Q H 2 O HCl Production Q Drying Q O 2 Production O 2 H 2 H 2 Production Cu Production W el The five-step Cu-Cl thermochemical cycle for H 2 production GaBi 4 model of entire system 13

Case Study: ExLCA of a hydrogen production process.

Exergy diagram of the life cycle of nuclear-based hydrogen production 14

Results and Discussion

Variation of (a) AP and (b) GWP (per 1 MJ exergy of H 2 ) with lifetime of the system 15

Results and Discussion

Variation of GWP and AP with exergy efficiency of hydrogen plant 16

Concluding Remarks

 Thermodynamic analysis throughout the life cycle of a process or system  The main contributor of life cycle irreversibility of nuclear-based hydrogen production is fuel (uranium) processing, for which the exergy efficiency is 26.7%.

 The lowest GWP per megajoule exergy of hydrogen is 5.65 g CO 2 -eq, for a plant capacity of 125,000 kg H 2 /day. The corresponding GWP for a plant capacity of 62,500 kg H 2 /day is 5.75 g CO 2 -eq.

 AP can also reduced from an initial value of 0.041 to 0.027 g SO 2 -eq per megajoule exergy of hydrogen, if the exergy efficiency is increased from 67% to 98%.

17