7.4.3.5 HFC-23 emissions from HCFC-22 manufacture

On average, 2.3% HFC-23 (GWP = 11,700 (IPCC, 1995)) is produced as a byproduct of HCFC-22 manufacture. The EDGAR database estimated 2000 emissions at 78 MtCO₂-eq (21 MtC-eq) (EDGAR, 2005), while the US EPA estimated 96 MtCO₂-eq (26 MtC-eq) (US EPA, 2006a). HCFC-22 has been used as a refrigerant, but under the Montreal Protocol its consumption is scheduled to end by 2020 in developed countries and over a longer period in developing countries. However, production of HCFC-22 for use as a feedstock in the manufacture of fluoropolymers, plastics and HFCs is expected to grow, leading to increasing emissions through 2015 in the business-as-usual case. Data on production rates and control technologies are contained in the IPCC Special Report on Safeguarding the Ozone Layer and the Global Climate System (IPCC/TEAP, 2005). Capture and destruction by thermal oxidation is a highly effective option for reducing HFC-23 emissions at a cost of less than 0.20 to 0.35 US$/tCO₂-eq (0.75 to 1.20 US$/tC-eq) (IPCC/TEAP, 2005, US EPA, 2006a).

7.4.4 Petroleum refining

As of the beginning of 2004, there were 735 refineries in 128 countries with a total crude oil distillation capacity of 82.3 million barrels per day. The U.S (20.5%), EU-25 (16.4%), Russia (6.6%), Japan (5.7%) and China (5.5%) had the largest shares of this capacity (EIA, 2005). Petroleum industry operations consume up to 15 to 20% of the energy in crude oil, or 5 to 7% of world primary energy, with refineries consuming most of that energy (Eidt, 2004). Comparison of energy or CO₂ intensities among countries is not practical because refining energy use is a complex function of crude and product slates and processing equipment. Simple metrics (e.g., energy consumed/barrel refined) do not account for that complexity. The shifts towards heavier crude and lower sulphur products will increase refinery energy use and CO₂ emissions. One study indicated that the combination of heavier crude and a 10 ppm maximum gasoline and diesel sulphur content would increase European refinery CO₂ emissions by about 6% (CONCAWE, 2005).

Worrell and Galitsky (2005), based on a survey of US refinery operations, found that most petroleum refineries can economically improve energy efficiency by 10–20%, and provided a list of over 100 potential energy saving steps. Key items included: use of cogeneration, improved heat integration, combustion optimization, control of compressed air and steam leaks and use of efficient electrical devices. The petroleum industry has had long-standing energy efficiency programmes for refineries and the chemical plants with which they are often integrated. These efforts have yielded significant results. Exxon Mobil reported over 35% reduction in energy use in its refineries and chemical plants from 1974 to 1999, and in 2000 instituted a programme whose goal was a further 15% reduction, which would reduce emissions by an additional 12 MtCO₂/yr. (Eidt, 2004). Chevron (2005) reported a 24% reduction in its index of energy use between 1992 and 2004. Shell (2005) reported energy efficiency improvements of 3 to 7% at its refineries and chemical plants. Efficiency improvements are expected to continue as technology improves and energy prices rise.

Refineries typically use a wide variety of gaseous and liquid byproducts as fuel. Byproducts that are not used as fuel are flared. Reducing the amount of material flared will increase refinery energy efficiency and decrease CO₂ emissions, and has become an objective for refinery management worldwide, though flare reduction projects are often undertaken to reduce local environmental impacts Munn (2004). No estimate of the incremental reduction in CO₂ emissions is available.

Refineries use hydrogen to remove sulphur and other impurities from products, and to process heavy hydrocarbons into lighter components for use in gasoline and distillate fuels. The hydrogen is supplied from reformer gas, a hydrogen-rich byproduct of catalytic reforming, and a process for upgrading gasoline components. If this source is insufficient for the refinery’s needs, hydrogen is manufactured by gasification of fossil fuels. US refineries use about 4% of their energy input to manufacture hydrogen (Worrell and Galitsky, 2005). Hydrogen production produces a CO₂-rich stream, which is a candidate for CCS (see Section 7.3.7).