## 2 Materials and Methods
### Identification of Levers for Reducing GHG Emissions
#### 2.4.2 GHG Emission Reduction Applied Refinery-Wide  
At refinery level, there are several options for lowering GHG emissions, in particular:  
* Refinery energy efficiency improvement: Refineries need energy for distillation, to drive endothermic chemical reactions and to power pumps, compressors, lighting, heating, etc. On average, the energy demand is broadly equivalent to 6-7% of the crude intake, but it could vary between 4-5% for a simple refinery and between 8-9% for a complex refinery with more energy-intensive processes [29]. Much of a refinery's energy demand is satisfied by burning refinery by-products such as fuel-gas and low-value oils. Changes in product demand and product quality regulation impact both the refinery process intensity and energy use. Historically, the average energy efficiency of the EU refining industry has been improving by around 0.5% annually, driven by a combination of energy costs, national energy efficiency programs and carbon costs (e.g., under the EU ETS). Many of the lower-cost opportunities may have already been implemented, leaving only the more challenging and expensive options. However, there is still potential for efficiency improvements by 2050; limited by refinery design and economical deployment, this study assumes that 22% improvement might be technically feasible by 2050 [29]. * Renewable energy use: There are several ways in which renewable energy might be used to provide power and heat in a refinery; for instance, imported fossil power could be replaced by imported low-carbon power, either through decarbonisation of the electricity grid or by a dedicated low-carbon power source. Imported natural gas or fuel oil used to provide fired heat could be replaced by low-carbon fuels (e.g., biogas, low-carbon hydrogen). Conventional heaters fired using hydrocarbon fuels could be replaced by electrical heaters using low carbon electricity. The technical potential for the use of renewable energy assumes that all energy inputs other than those linked to unavoidable self-produced gas and FCC coke are replaced by zero-carbon energy. The technical limit for the average EU refinery to reduce CO\({}_{2}\) emissions by using renewable energy imports is roughly one-third. * Refinery Carbon Capture and Storage (CCS): Nearly all a refinery's direct CO2 emissions could be captured, but implementation is hampered by the wide range of CO\({}_{2}\) sources in a refinery. This leads to either a multitude of CO\({}_{2}\) capture plants and large amounts of CO\({}_{2}\) pipework, or a large amount of infrastructure to gather blue gases for a centralised refinery capture unit [29; 34]. While 100% of refinery CO\({}_{2}\) emissions could be captured (including all of the emissions associated with running the capture plant), a lower level of CO\({}_{2}\) capture would be expected. The JRC report [19] considers that CCS reduces the GHG intensity of SMR hydrogen from 104 to 39.7 gCO\({}_{2 eq}\)/MJ H\({}_{2}\)--70% mitigation. This paper considers two CCS lever cases: in the first case the refinery deploys site-wide CCS but continues to import hydrogen without CCS; in the second case the refinery has its own SMR unit that is included within the site-wide CCS; the providers of imported electricity and steam are assumed not to have CCS in both cases. These two cases lead to a 64% and 83% reduction in refinery CO\({}_{2}\) emissions,respectively. The reductions in refinery emissions have been used to adjust the overall WTW emissions, leading to overall potential for reduction of 4.6 and 5.7 gCO2 eq/MJ jet fuel for the two CCS lever cases, or reductions of 4.0 and 5.3%, respectively. * Large-scale low carbon hydrogen: Hydrogen is used extensively in refineries for hydrodesulphurisation and hydrocracking, so the demand depends on the type of refinery and sulphur content in the processed crudes. Hydrogen production currently accounts for around 19% of refining emissions, which is expected to rise to as much as 30% by 2030 due to growing demand for hydrogen.