Page 83 - Materials Chemistry, Second Edition

Life Cycle Assessment: Principles, Practice and Prospects
70
Table 6.8 End-of-life assumptions for alternative bags
Reuse (as a
bin liner for
Landfill Recycled Composting household
Alternative bags % % % Litter % waste)% A
All degradable polymers 70.5 0 10 0.5 19
HDPE singlet bag 78.5 2 0 0.5 19
Kraft paper bag with 39.5 60 0 0.5 0
handle
PP fibre ‘green bag’ 99.5 0 0 0.5 0
Woven HDPE ‘swag bag’ 99.5 0 0 0.5 0
LDPE ‘bag for life’ 97.5 2 0 0.5 0
Calico bag 99.5 0 0 0.5 0
LDPE, low density polyethylene; HDPE, high density polyethylene; PP, polypropylene
A
Subsequently avoids HDPE bin liners. In the landfill environment and source-separated organics composting it is
assumed that degradable polymers will degrade like food waste (i.e. 90% of the polymer will degrade).
‘bag for life’). The findings for greenhouse gas emissions indicate that reusable bags, except for
calico, still have a lower impact upon the environment than HDPE singlet bags or degradable
polymers. Greenhouse impacts are dominated by carbon dioxide through electricity and fuels
consumption, methane emissions through degradation of materials in anaerobic conditions
(e.g. landfill), and nitrous oxide (N O) emissions in fertiliser applications on crops (Fig. 6.11).
2
Degradable polymers with starch content produce more greenhouse gas emissions due to
methane emissions during landfill degradation and N O emissions from fertilising crops. A
2
sensitivity analysis was performed to determine the effect of reusing Kraft paper bags. In the
results in Fig. 6.11 it is assumed that the Kraft paper bags are single trip bags. In the sensitivity
it is assumed that each bag will be reused a second time (i.e. that only 260 bags are required in

Figure 6.12 Litter characterisation values for all bags. The values chosen here have been
estimated in the absence of definitive data on the subject and are presented to show how the
potential marine impact may vary under these assumptions. PBS/A, starch polybutylene succinate/
adipate; PBAT, starch with polybutylene adipate terephthalate; PE, polyethylene; PLA, polylactic
acid; HDPE, high density polyethylene; PP, polypropylene; LDPE, low density polyethylene.

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