BAKU, Azerbaijan, Nov.9
By Leman Zeynalova – Trend:
On average, CO2 contributes 65 percent and methane 34 percent of greenhouse gas emissions from “upstream” processes – the exploration, drilling and development, production and extraction, surface processing, and transport to the site of refining, Trend reports with reference to the International Energy Agency (IEA).
These emissions accounted for 5 percent of total global fuel combustion emissions in 2015. Overall, greenhouse gas emissions associated with the energy used for oil production represent about 15 percent of well-to-tank emissions. In addition, CO2 may be emitted when gas is flared or methane escapes as fugitive or vented emissions. Together, such emissions can constitute around 40 percent of well-to-tank greenhouse gas emissions for providing oil-derived gasoline and diesel.
Crude oil transport represents around 5 percent of total well-to-tank emissions. Overall, refining typically represents around one-third of the well-to-tank emissions of oil products. Refining starts with separation of crude oil into various hydrocarbon fractions (crude distillation). Complex refineries add a step to convert low-value fractions into high-value ones (upgrading).
Emissions from condensate splitters and natural gas liquids fractionation plants were also considered in the assessment although these units mostly produce lighter products – such as ethane, liquefied petroleum gas (LPG) and naphtha – rather than conventional road transport fuels. Refining emissions are then allocated among the final products – including gasoline, diesel and kerosene – according to the processes required to produce each product. For example, the well-to-tank emissions of gasoline are higher than those of diesel, reflecting the more energy-intensive refining process units (e.g. hydrocracking) used to produce gasoline products.
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