Crude and vacuum stack capture
Crude and vacuum electric heating
Base emissions Tonnes/hour CO captured Boiler increase Scope 2 increase
Base emissions Tonnes/hour 221 Stack CO avoided -37 Scope 2 increase 119
221 -33
Carbon capture
8
11
Net change
82
Net change
-14 207
Finding the optimal balance
New emissions
303
New emissions
(No fuel gas aring)
Crude and vacuum SMR H ring
Base emissions Tonnes/hour 221 Stack CO avoided -3 7 Boiler change Scope 2 increase -3 0 50 Additional SMR CO
Hydrogen ring
Electri cation
Net change
10
New emissions
231
Figure 3 Balancing Scopes 1 and 2 emissions
from the facility. This can be achieved by either providing emission-free energy sources such as zero-carbon intensity hydrogen and electricity or capturing the resulting emissions before they are released into the air via carbon capture. Misleading internal approaches Here is the catch. By purchasing more electricity from the grid to energise modified fired heaters, the increase in Scope 2 emissions outweighs the decrease in Scope 1 emissions, as shown in Figure 3 . This scenario leads to higher product carbon intensities. Using hydrogen-fired heaters and boilers also raises CO₂ emissions due to the fossil energy required to operate the steam methane reformer (SMR) combined with the CO₂ emissions produced by the reaction. If natural gas is purchased and the SMR is used to produce the necessary hydrogen, CO₂ emissions will increase. Even with systems such as amine absorption in place, only half of the expected CO₂ may be captured. This is By purchasing more electricity from the grid to energise modified fired heaters, the increase in Scope 2 emissions outweighs the decrease in Scope 1 emissions
due to the extra boiler load required for amine regeneration steam and the electricity needed for compressing the captured CO₂. After energy efficiency improvements are completed, the ‘going-it-alone’ strategy faces fast-diminishing returns. To further reduce emissions, solutions from outside the facility gates must be sought. This approach incorporates new low-carbon energy sources like wind and solar power and uses low- carbon hydrogen produced from electrolysers that employ ‘green’ electricity. Another option includes capturing CO₂ emissions and either using them as chemical process feedstocks or sequestering them in the earth’s crust. Solutions must be explored outside the facility’s boundary. Outside-the-box approaches Carbon capture (CC) is a mature technology that carries low risk and reliable operations. The downside of the approach is that these units can require large areas of plot space near the emissions source because of the size and cost of the towers and ducting. Often, that plot space is unavailable. Furthermore, they are capital intensive. For instance, recent projects aiming to capture 1 million tonnes of CO₂ per year cost about USD 500 million, and that is only the beginning. Finding a destination for the captured CO₂ is equally as important to prevent its re-entry into the atmosphere.
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