Environment and HSSE
Using energy more efficiently, and investing in innovative technology, can help us manage emissions
Energy useWe use about 10% of the oil and gas we produce for our own energy needs, and buy some power from other suppliers. Energy is used throughout the group; with the most intensive use in our chemical plants and refineries. Nitrogen oxides and sulphur dioxide, which account for about a third of our total emissions to air, are formed during combustion. These gases are acidic when dissolved in water and can result in acid rain and acidification.
Improving energy efficiency in operations - frequently in combination with the use of low sulphur fuel, special burners and exhaust gas abatement controls - is the key to reducing our emissions of these gases. It also helps us reduce costs.
Product handlingDuring the transport and handling of crude oil, fuels and other hydrocarbon products, a small volatile proportion may be lost and can evaporate in the atmosphere at low temperatures. NMHCs are also emitted as 'fugitive' emissions from small leaks in components at our plants.
Elimination of these minor losses is important for health, safety and environmental reasons. They are often managed using vapor recovery systems that capture and condense the volatile NMHCs for blending back into the product. These systems are commonly used when delivering diesel and petrol fuel to service stations, or transporting crude oil in marine tankers. Instead of being released into air, the NMHCs are returned in our tankers to the oil terminals for recovery as product.
Gas flaringFlaring is the term used to describe the burning off of surplus natural gas found in oil and gas reservoirs. We carry out flaring during exploration and production, and to lesser extent in our refining and chemicals business, for various reasons. For instance, as a safety measure during plant shutdowns or when there is no facility to capture and transport the gas for sale.
Methane, the main compound in natural gas, has a higher global warming impact when vented directly to air rather than burned to form carbon dioxide, because most of the gas flared is methane, the process does less harm to the environment than direct venting. Most flaring is carried out offshore away from towns or cities, but can still contribute to regional acid rain problems when acid gases are flared.
We have reduced gas flaring in our operations over a number of years: by supplying gas to power stations; and through the use of engineering solutions, for example direct return or 're-injection’ of gas to the reservoir. Gas flare recovery systems, which recover and store gas for use as plant fuel or for resale as a product, have also been used.