2
4
‘2030’ Fuel/power emission factor Worst case fuel/power emission factor
Max H Cl case (3 tCO /tH )
3
38%
1
Data labels: % of CO intake
2
16%
CH 1% 4% 15%
56% 50%
51%
Xylenes
33%
14%
41%
23%
32%
82%
14% 3%7% 9%
21%
0
1
Carbon- ation
Urea Polyols PPC
41%
MeOH FT
Oxo (butanal)
-6% -7%
29%
0%
0% 0% 0%
0
CH
FT
Carbon-
Urea
PPC
MeOH
Oxo (butanal)
Polyols
-1
ation Xylenes
outside the site. In Figure 1, the utility import- related emissions were subtracted from the CUI, as shown. Note that the hydrogen consumed was assumed to be imported green hydrogen with a zero carbon footprint. Naturally, emissions related to imported electricity and fuel/steam will depend on their CI. Table 3 shows the CI of these utilities in the 2030 and 2050 scenarios. It should be noted that the 2030 scenario assumes an initial degree of decarbonisation of the utility imports, whereas the 2050 scenario forecasts total decarbonisation. A worst-case scenario has been considered as a sensitivity case assuming coal is used to produce electricity while heavy residual oil is the imported fuel. Figure 3 shows the carbon footprint of the utility imports in the 2030 and worst-case scenarios. The data labels show the level of these emissions, expressed as a percentage of the gross carbon intake (i.e. not corrected for the utilities). In the 2030 scenario, the utility imports offset up to 23% of the carbon intake in the case of Oxo synthesis. If 100 tonnes of CO 2 is sent to the Oxo unit, where it is converted into n-butanal, the steam, power, and fuel intake will generate 23 tonnes of CO 2 outside the Oxo facility. In the worst-case scenario, the offset reaches 82% of the carbon intake for carbonation. The high penalty in the case of carbonation is due to the relatively high use of electricity compared to the CO 2 consumed. Impact of hydrogen imports on carbon emissions The CUI chart in Figure 1 assumes hydrogen imports are carbon-free. The CI of grey Figure 3 Carbon emissions related to power/fuel imports, t CO2 / t product
hydrogen varies from 8 to 12 t CO2 /t H2 , depending on the feed type and unit efficiency. Figure 4 shows the ‘max CI case’ impact with green hydrogen emitting 3 t CO2 /t H2 , the upper limit for green hydrogen under the EU taxonomy (Johansen, 2021). The graph shows that the CI of ‘green hydrogen’ has a major impact on the CI of hydrogen-intense processes. In the ‘max CI case’ for methane production, 56% of the carbon intake is offset by the emissions associated with the production of the imported hydrogen. Additionally, the offset exceeds 40% for the methanol, xylenes, and FT synthesis. This means these carbon utilisation technologies will effectively become net CO 2 emitters if fed with grey hydrogen. Capex An Association for the Advancement of Cost Engineering (AACE) Class IV, equipment- based, inside battery limits (ISBL) capital cost estimation was done for the nine technologies. Figure 5 compares the specific investment costs for the different technologies. The low relative costs for some of the technologies are due to simpler processes operating at low temperatures. Processes utilising predominantly gas streams are more capital Figure 4 Worst-case carbon emissions related to green hydrogen, t CO2 / t product
2030
2050
Worst
Scenario
Scenario
case
Electricity Fuel / steam
0.26 0.14
0.00 0.00
1.00 0.28
Table 3 Emission factors including worst case, tCO 2 /MWh
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