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S-1
a Singapore Membrane Technology Centre, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798
Scheme S1. Procedure for establishing SG LCI for electricity production .............................................................................................................................. 3
Table S1. Assumptions for establishing SG LCI for electricity production .............................................................................................................................. 4
Table S2. Assumptions for electricity from heavy fuel oil in SG ............................................................................................................................................... 5
Table S3. Assumptions for electricity from natural gas in SG .................................................................................................................................................. 6
Table S4. Characterization models used in Life cycle impact assessment ............................................................................................................................ 7
Table S5. Contribution analysis of US, SG, and ES scenarios a,b ........................................................................................................................................... 8
Table S5. Contribution analysis of US, SG, and ES cases a,b (continued) .............................................................................................................................. 9
Table S6. The impact break down of crude oil production in ODP ........................................................................................................................................ 10
Figure S1. The contribution of individual processes under different salinity levels .............................................................................................................. 11
Table S1. Assumptions for establishing SG LCI for electricity production
Processes Comments
Singapore electricity production mix
(1) The assumptions for developing datasets of electricity from heavy fuel oil are summarized in Table S1-S1
(2) The assumptions for developing datasets of electricity from natural gas are summarized in Table S2-S1. The Wobbe Index of natural gas is assumed to be 45.2 MJ/m
3 1.The natural gas composition is assumed to be the same with Chan’s study
2 .
(3) The overall performance of Orimulsion is about 9% lower than heavy fuel oil 3. Therefore, the data used to represent electricity from Orimulsion is
modified from the heavy fuel oil dataset in French scenario.
(4)The photovoltaic electricity generation in Singapore is modelled as German scenario
(5) The datasets of electricity from waste incineration and diesel combustion are modelled as Switzerland scenario, which is the only available data in Ecoinvent database.
↑ Electricity transmission
and distribution (1) ABB is a major contractor for the management and operation of Singapore’s electricity transmission and distribution network
4. Therefore, all the
construction of transmission and distribution network in Singapore is assumed to use the same technology as Switzerland. However, some changes were made to simulate local context. Firstly, wood poles and wood preservative process are removed because the transmission and distribution network in Singapore are all underground cables; secondly, extra excavation process was added for digging trenches for cables.
(2) The overall electricity power transmission and distribution loss in Singapore is about 5% 5. Since the transmission distance in Singapore is limited,
the loss of transmitting electricity at high voltage is assumed as 2%, while the electricity loss during medium-voltage is 3%
Table S2. Assumptions for electricity from heavy fuel oil in SG
Processes Comments
Electricity, oil, at power plant It is calculated based on power plant efficiency (33%) 6
↑ Heavy fuel oil, burned in power plant Senoko Power, the largest oil-fired power generation company in SG, employs the technology of Hitachi steam
7. It is appropriate to use
Japanese (JP) dataset as a proxy for SG. In addition, the dataset for JP oil-fired power plant is the same as that in French (FR) scenario in Ecoinvent database. The FR dataset is modified to fit SG context. The release of NOx and SOx is reduced to 30% with the help of retaining technology
↑ Heavy fuel oil, at regional storage This process mainly accounts for the impacts imposed by transporting heavy fuel oil from refinery to end user. Ecoinvent provide datasets
for Europe (RER) and Switzerland (CH) scenario. Since the impacts of transportation is proportional to distance, the CH scenario is used as the proxy for SG scenario
↑ Heavy fuel oil, at refinery The technology used in SG is assumed the same with FR. Therefore, this datasets is established based on the modification of RER
scenario. ↑
Crude oil production Share of oil imported in Singapore: Middle East (RME) - 88%, Malaysia (MY) – 5%, Indonesia (ID) – 2%, China(CN) – 1%, Vietnam (VN) – 1%, Russia (RU) – 1%, others – 2%
8. The transportation of crude oil from exploration site to refinery is modelled as Europe scenario.
Table S3. Assumptions for electricity from natural gas in SG
Process Comments
Electricity, natural gas, at
power plant
It is calculated based on power plant efficiency (50%) 9
↑
Natural gas, burning in
power plant
Singapore’s gas-fired power plant is modelled as German (DE) scenario since two of largest power generation company in Singapore, Senoko Power 10
and Power Seraya 7, are identified as using Siemens Combined-Cycle Plants.
↑
Natural gas, high pressure,
at consumer
Both SG and JP are the Asian countries with highest population density 11
, so the SG dataset of natural gas distribution network is calculated based
on that in JP scenario, assuming the length of pipelines is proportional to the territorial area.
↑
Natural gas, production MY
and ID, at long-distance
pipeline
About 75% of natural gas is imported from ID, while 25% is from MY 12
. It is assumed that half of the natural gas pipelines transported from Malaysia /Indonesia to Singapore are onshore pipeline, while another half are offshore pipelines. The leakage of Singapore’s natural gas transportation is assume to be similar to reference
13.
↑
Natural gas, at production
MY and ID
The composition of natural gas is relatively constant and carries similar impacts, so the developed datasets using the similar technology is adopted to mimic the upstream process of natural gas in SG scenario. it was Royal Dutch Shell that began the gas exploration and production there
14, the
production of natural gas in MY and ID is modelled as Netherlands (NL) scenario.
↑
Natural gas, production NL It is assumed that 70% of natural gas is produced offshore, while another 30% is onshore.