Composting   is   a   well-­‐established   technology   used   for   food   waste   treatment.  

There   is   ample   research   into   the   ecological   assessment   of   composting.    

Nevertheless,   there   are   two   issues   that   need   further   investigation:   system  

boundary  incompleteness,  and  the  exclusion  of  capital  inputs.  

This   work   adopts   a   hybrid   life   cycle   assessment   approach   to   quantifying  

ecological  impacts  of  food  waste  composting  in  the  UK.    The  analysis  is  based  on  

composting   1   tonne   of   domestic   food   waste.     Data   used   for   this   study   was  

obtained   from   ecoinvent   database   v2.2,   WRATE,   an   LCA   tool   designed  

specifically   for  waste  management  studies,  and  a  number  of  UK-­‐based  sources.    

The   modelled   system   includes   construction,   maintenance,   operation   and  

compost   utilization.   Both   food   waste   collection   and   transportation   were  

excluded  from  this  study.    The  EASETECH  LCA  tool  was  used  in  order  to  assess  

the   potential   impact   on   the   categories   of   Global   Warming   Potential   (GWP),  

terrestrial   acidification,   and   terrestrial   eutrophication.     The   robustness   of   the  

model   is   investigated  with   a   sensitivity   analysis.     This   paper   also   investigates  

variations  in  results  based  on  five  different  composting  technologies  in  order  to  

develop  a  generalized  ecological  assessment  method.  

The  results  show  that  Construction,  and  operation  constitute  approximately  95%  

of  GWP  (18.3  kg  CO2-­‐Eq).    The  inclusion  of  capital  inputs  is  accountable  for  20%  

of   GWP.     The   adoption   of   a   hybrid   LCA   approach   has   also   increased   GWP  

captured  by  18%  and  21%  in  the  construction  and  operation  stages  respectively.    

In   addition   to   this,   it   increases   acidification   and   eutrophication   emissions  

captured  by  14.5%,  and  22%  respectively.    Other  findings  by  this  paper  could  be  

potentially   used   to   establish   a   generalized   assessment  method   to   quantify   the  

ecological  burden  of  different  food  waste  composting  processes.  

This   work   provides   strong   evidence   which   demonstrates   the   significant  

contribution   of   capital   goods   to   environmental   burdens.     It   also   illustrates   the  

substantial  benefits  of  applying  a  hybrid  approach.  

Key  words:  Food  Waste,  Life  Cycle  Assessment,  Hybrid-­‐LCA,  EASETECH.  

 

AN ECOLOGICAL ASSESSMENT OF FOOD WASTE COMPOSTING USING A HYBRID LIFE CYCLE ASSESSMENT

UNIVERSITY OF SURREY, GUILDFORD, UK.

Ramy  Salemdeeb  and  Prof.  Abir  Al-­‐Tabbaa   Tuesday, 7th JULY 2015.

Food waste: an environmental challenge

ü Increase in quantity. ü Stringent obligatory targets. ü The availability of various food waste processing options.

“What gets measured, gets managed.”

Food waste: an environmental challenge

Motivation: LCA drawbacks

•  Lack of inventory data.

•  Truncation error due to system incompleteness.

•  Multi-functionality of systems and related allocation-issues.

•  Loss of site-specific information due to aggregation of impacts over the entire life cycle.

Motivation: the Inclusion of capital inputs

•  88% of LCA studies exclude capital input. Even more concerning is that

26% of the studies claim that capital input has insignificant ecological impacts (Laurent et al., 2014).

•  Impacts of capital inputs are firstly addressed by Otama et al. (1997).

•  Environmental impacts, associated with capital inputs, are estimated to be nearly 10% of the total life cycle impacts (McDougall et al., 2001; Finnveden et al., 2005).

•  For instance, a study by Brogaard et al. (2015) estimates that the contribution of capital input to global warming potential for composting and AD are 10-22% and 1-2%, respectively.

Towards a holistic approach

LCA + IOA = Hybrid LCA

LCA IOA

My PhD research objectives

The primary aim of my PhD study is to provide a holistic approach to quantifying the ecological impacts of food waste management options in the UK. The objectives are therefore to:

•  Develop the hybrid-LCA model for the UK food waste management options by integrating input output analysis into the Life Cycle Assessment (LCA).

•  Quantify environmental burdens associated with food waste management infrastructure in support of the analytical power of input output technique.

•  Estimate the overall environmental burden of food waste management options using hybrid-LCA.

•  Investigate ecological benefits of food waste prevention via sustainable consumption using the model.

Methodology

•  The hybrid approach integrates an input-output technique with a process-based method. All stages to set up a food waste treatment technology are included in this study. These stages include: investment, upstream activities, operation, and downstream activities.

•  Technologies included are composting, anaerobic digestion, and incineration.

A diagram shows the components of the system.

Methodology

Methodology

-  A representative system was chosen as the baseline scenario in order to represent the most common technologies in the UK.

-  With high quality data/easy to be compared with other technologies. -  Baseline models were chosen based on literature reviews and consultation.

-  Modelling the system using a hybrid life cycle assessment method. -  The modelling process includes; investment stage-operation stage-output utilization. -  Waste collection and transportation are excluded from this study.

-  Run the model and analyse results.

-  Variation and sensitivity analysis was performed to investigate the variation in results considering different data sources and scenarios.

Selection of a baseline

system

Modelling

Analysis

Variation & sensitivity analysis

Selection a baseline system

Composting Housed Windrow Composting (enclosed) Lifespan: 15 years Capacity: 30,000 t/y Residence time: 84 days

11

Stage  II  (stabiliza.on)  

Aera.on:  14-­‐21  days    

60°C for  28  hrs  

   

 

   

Stage  I  (sani.za.on)  

Aera.on:  14-­‐21  days    

60°C  for  28  hrs  

Stage  III  (Matura.on  pad)  

Matura.on:  8  weeks  

 

 

   

Recep.on  

Food  Waste    

 

Tunnel’s dimensions 21 (l) 6.5 (w)

Four aeration channels/leachate , a radial fan.

Compost  PAS  1100  

 Rejected  material  to  disposal  

 

Analysis & results

Climate Change (GWP 100)  

Terrestrial Acidification (AP)  

Terrestrial Eutrophication (TEP)  

kg CO2-Eq   AE   AE  Total   1.35   0.16   0.91  Construction   8.01   0.03   0.06  Operation   10.31   0.26   0.99  Maintenance   1.88   0.01   0.003  Decommissiong   0.29   0.0004   0.002  Output utilisation   -19.14   -0.13   -0.14  

-25

-20

-15

-10

-5

0

5

10

15

20

25

GWP100(kg CO2-Eq)

AP (AE) TEP (AE)

Emis

sion

s ou

tput

Environmental Burden (unit)

Output utalization

Decommissiong

Maintenance

Operation

Construction

Total

12

-60%

-40%

-20%

0%

20%

40%

60%

80%

100%

GWP AP TEP

Rel

ativ

e co

ntrib

utio

n (%

)

Environmental Burden

Output utalization

Decommissiong

Maintenance

Operation

Construction

Climate Change  

Terrestrial Acidification  

Terrestrial Eutrophication  

GWP100   AP   TEP  

Construction   LCA   82.0   85.5   97.0  EEIOA   18.0   14.5   22.3  

Operation   LCA   78.9   97.4   99.3  EEIOA   21.1   2.6   0.7  

Maintenance   LCA   7.8   12.6   37.6  EEIOA   92.2   87.4   62.4  

0

2

4

6

8

10

12

14

16

Process Based Anaysis

Input-output Analysis

kg C

O2-

Eq

GWP

0

0.05

0.1

0.15

0.2

0.25

0.3

Process Based Anaysis

Input-output Analysis

AE

AP

Analysis & results

0

0.2

0.4

0.6

0.8

1

1.2

Process Based

Anaysis

Input-output Analysis

AE

TEP

Operation

Maintenance

Construction

Result summary

•  The analysis quantitatively confirms that environmental

burdens associated with the consumption of capital goods in the investment stage are significant and should therefore be considered whilst drawing the system boundaries.

•  The adoption of hybrid-LCA reduces the truncation error and

increases ecological burdens captured. Compared to the conventional process-based study, the results of the hybrid LCA have increased by 26.5% for GWP, 5.5% for AP and 1% for TEP,

Variation & sensitivity analysis

Stage 1 • Contribution analysis

Stage 2 • Perturbation analysis

Stage 3 • Sensitivity analysis

Stage 4 • Scenario analysis Source:  (Clavreul  et  al.,  2012)

Stage 1: Contribution analysis

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

GWP AP TEP

mPE

\ ye

ar

Environmental Burden

Construction Operation Maintenance Decommissiong Output utalization Total

Stage 2: Perturbation analysis

•  10% variation was used to determine the effect of an arbitrary change of single parameter values on the model’s result.

•  The sensitivity ratio (SR) was calculated for each parameter using the following equation:

Process parameters   Symbol   SR  Gravel   CS1   0.006309  Chemicals inorganic   CS2   0.002528  Lubricating oil   CS3   0.000927  Concrete   CS4   0.207231  Flat glass   CS5   0.000781  Aluminium   CS6   0.082125  Copper   CS7   0.00099  Lead   CS8   0.000766  Steel, low-alloyed,   CS9   0.588156  Alkyd paint, white, 60% in solvent   CS10   0.000753  Nylon 66   CS11   0.004166  Polyethylene, HDPE, granulate   CS12   0.000913  Polyethylene, LDPE, granulate   CS13   0.113091  Synthetic rubber   CS14   0.001658  Round wood, Scandinavian softwood, under bark, u=70% at forest road, NORDEL   CS15  

0.000758  

Parameters to be further investigated include concrete, aluminium, steel, and polyethylene.

0 0.2 0.4 0.6 0.8 CS1 CS3 CS5 CS7 CS9

CS11 CS13 CS15

SR

Para

met

er

𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦  𝑅𝑎𝑡𝑖𝑜𝑛  (𝑆𝑅) =  ∆𝑟𝑒𝑠𝑢𝑙𝑡

𝐼𝑛𝑖𝑡𝑖𝑎𝑙  𝑟𝑒𝑠𝑢𝑙𝑡∆𝑝𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟

𝐼𝑛𝑖𝑡𝑖𝑎𝑙  𝑝𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟   Source:  (Clavreul  et  al.,  2012)

Stage 3: Sensitivity analysis (construction phase)

0.E+00 1.E-01 2.E-01 3.E-01 4.E-01 5.E-01 6.E-01 7.E-01 8.E-01

GWP Acidification Eutrophication

mPE

\ ye

ar

Environmental impact category

Construction

0

2

4

6

8

10

12

GWP Acidification Eutrophication

mPE

\ ye

ar

Environmental impact category

Operation -25

-20

-15

-10

-5

0 GWP Acidification Eutrophication

mPE

\ ye

ar

Environmental impact category

Output  utilization

Stage 4: Scenario analysis (electricity consumption)

Source: Life cycle sustainability assessment of UK electricity scenarios to 2070 (Stamford and Azapagic, 2014)

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

100%

Reference (2010)

Sc 65(a) Sc 65(b) SC 100

Con

trib

utio

n (%

)

UK electricity scenario

Coal Oil Gas

Nuclear Hydro (natural flow) Solar

Offshore wind Bioenergy Pumped Storage

Other fuels

Modelled  scenarios:

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Ref (2010) Ref (65-1) Ref (65-2) Ref (100)

mPE

/ ye

ar

UK Electricity mix scenario

GWP AP TEP

Results:

Conclusion & future recommendations

•  The study confirms the significant contribution of environmental burdens associated with capital goods to the overall environmental impact of composting and the role of hybrid LCA in reducing truncation error.

•  The hybrid LCA shows that the investment, operation and output utilization

stages are the greatest overall contributors to environmental burdens. The Monte Carlo analysis has identified the parameters within these stages which are most accountable for these emissions.

•  The Sensitivity Analysis demonstrates huge variation within the results. It should therefore be developed in accordance with the objectives of each particular study.

•  As a future recommendation, results should be discussed at the practical

and policy levels in order to integrate environmental sustainability in the decision making process.

References available upon request. Email: rrms2@cam.ac.uk Phone: +44 (0) 1223 765 054

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