یک مطالعه مقایسه ای بر روش های اتحادیه اروپا و ژاپن برای ارزیابی کاهش انتشار CO2 و صرفه جویی در انرژی در صنعت آهن و فولاد

Information on energy consumption and carbon dioxide (CO2) emissions from the iron and steel industry may become important to the assessment of energy saving and the design of emissions trading schemes. This paper focuses monitoring aspects, used two methods to calculate CO2 emission, the European Union Emission Trading Scheme and a method developed by the Japanese Iron and Steel Federation, to investigate the effect of the accounting method on the assessment of energy saving by four model steel mills with different levels of energy efficiency. Depending on the calculation method used, the calculated energy savings and calculated CO2 emissions for a given mill were found to differ from 5% to 15% and 4% to 14% respectively, simply by using different calculation methods. Methodologies that evaluate only CO2 emission and track emissions by process may not fully account for energy saving efforts such as using waste heat, generating power using byproduct gases, and energy management efforts applied over the whole mill rather than on a single process. Points of concern in the iron and steel industry are identified in the areas of calculating energy saving, determining CO2 emissions, and setting benchmarks.

Steel is widely used in our lives, and was a crucial material in human technological development. Steelmaking involves many processes that use large amounts of energy, including sintering, coke production, and reduction of iron ore. Steelmaking is estimated to have consumed 29 EJ globally in 2009, or 6% of total global energy consumption, and while emitting 2.5 Gt-CO2 of greenhouse gases (WSA, 2011). Therefore, the possibility of energy saving and CO2 emission reduction in the iron and steel industry has long attracted interest, both within academia and at the plant operations level. The levels of energy consumption and CO2 emission from steelmaking may become important fundamental information in the pursuit of energy savings and climate change mitigation, because these data could be used to assess overall energy saving performance and in the design of emission trading schemes. However, different assumptions and methods of calculation, such as determining individual processes, the degree of integration, and boundary definitions, result in different estimates of energy consumption and CO2 emission (Tanaka, 2008 and Siitonen et al., 2010). No calculation method is currently used as the global standard. Instead, a number of calculation methodologies are used around the world, including the European Union Emission Trading Scheme (EUETS) and the methodology adopted by the Japanese Iron and Steel Federation, which is used as a reporting format for the World Steel Association, and for the voluntary initiative by Keidanren (Japan Business Federation) also submitted to national committees related to deliberations on CO2 emissions. Some of these methodologies may not fully or uniformly assess energy saving efforts in steel plants operating under different conditions. This paper presents results of a calculation of CO2 emission using the methods of both the European Union Emission Trading Scheme 1 and the Japanese scheme in order to show the effects of these different accounting methods. Energy usage and CO2 emissions were calculated for a set of model steel mills having different energy balances, using the methodology from the Emissions Reporting Form of EUETS and the method of the Japanese Iron and Steel Federation. The latter method is currently under discussion as a candidate for a standardized methodology for energy and CO2 accounting at the International Organization for Standardization (ISO) and the World Steel Association. This study addresses the appropriateness of the methodologies and clarifies points of concern in calculating energy consumption, CO2 emission, and energy saving, as well as in defining and using benchmarks and consumption rates in the steelmaking industry.

We considered four hypothetical model steel mills with the same production output and with different levels of energy saving, and we calculated energy consumption and CO2 emission using two EUETS methodologies and the Japanese methodology. The following points were uncovered that are important to ongoing discussions of carbon trading systems. First, methodologies that consider CO2 emission only may not fully account for power generation by use of by-product gas or the recovery of exhaust heat. These energy saving measures result in reduction of energy costs. However, if a scheme regulates CO2 emission only, incentives to invest in energy saving will decrease if no credit is given for the accompanying reduction in CO2 emission. Next, unlike performing a balance calculation over the entire steel mill, deriving the balance per process or per activity does not account for the use of by-product gas, because utilities and internal losses that are not apportioned to any process are overlooked. Assessing over the entire installation, and assessing from an energy viewpoint in addition to CO2 emission, are essential to recognize and support continued energy efficiency improvement. This especially applies in a situation where the CO2 value is not ideally passed on to the generated power or fuel cost. We strongly urge that these issues will be fully considered in the future design and revision of emissions trading schemes within and between countries.