Economy
& Energy
Year IX -No
58:
October-November
2006
ISSN 1518-2932
No
58 Em
Português|
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Economy
& Energy |
No
58 Em
Português |
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Evaluation of CO2 Emission between 1970 and 2004 Using the Extended Top-Down Process
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Text for Discussion: Evaluation of CO2 Emissions Using the Top-Down Extended Process Between 1970 and 2004 Olga
Mafra, Frida Eidelman e Carlos Feu Alvim Summary 4 - Use of the ben_eec Programme in the Calculation of Carbon Content 4.1 Calculation of Energy Sources Data Using the ben_eec Programme 4.2 Cálculation of Carbon Content in the ben_eec Programme 5.1 Energy Content per Carbon Content in Fuels 6 – Cálculation of the Top-Down Emissions 6.1 – Carbon Retained in Non Energy Use List of Tables Available at the Internet 1 - Introduction This report is part of the data survey for the Carbon Balance revision, object of the Partnership Contract 13.0020.00/2005 between the Economy and Energy – e&e –organization and the Ministry of Science and Technology – MCT. It is specifically listed as Goal 1 – “Estimate of C and CO2 Emissions in Energy Use and Transformation from 1970 to 2004 by the Top Down Extended Process”. The activities foreseen for this phase are: use of carbon balance in energy production, transformation and use in Brazil in order to evaluate emissions in the period and using the above mentioned approach. 2 - Perliminaries The MCT has previously signed the No 01.0065.00-2003 Agreement with the e&e Organization aiming at calculating the carbon balance in the Brazilian Energy Matrix regarding the Brazilian Inventory of the greenhouse effect gases. One of its objectives was to detect eventual incoherence in the initial Inventory by comparing the Top-Down Extended (TDE) and Bottom-Up (using coefficients) processes. In the first calculation, the Top-Down process was extended so that it would evaluate carbon emissions in the transformation and consumption of energy. The Bottom-Up methodology using coefficients was applied to the emissions inventory from 1990 to 1994. So, emission coefficients were deduced for the various gases responsible for the greenhouse effect gases by unit of consumed energy and by fuel listed in the Energy Balance. The result of the previous agreement identified a series of incoherence and omissions that the present Agreement will try to resolve. The objective of the present study is to consolidate a Carbon Balance that can be an instrument to emissions evaluation, helping the establishment of policies for that area. This Partnership Contract foresees as the first goal the elaboration of the Carbon Balance using the TDE methodology. From the previous study it was concluded that the application of this methodology permitted the calculations of emissions by a process equivalent to the Top-Down by the IPCC methodology using some lines of the Carbon Balance and retention and oxidizing coefficients. This methodology was adopted in Brazil for calculating its inventory and the corresponding results are presented in Reference 1. Comparison of results has shown a good agreement of data regarding emitted carbon and its CO2 equivalent, around 1.3%. However, concerning analysis by fuel some divergences were detected which is tried to be clarified in the present study. Furthermore, the present Partnership Contract foresees the improvement and use of computer programs to automate emissions calculations aiming at assisting in the calculation of the next inventories. It is expected that once the incoherence is eliminated in the use of coefficients or conflicting procedures in the two methodologies, some points that need clarification will be defined, including experimental measurements. This technical note calculates the Top-Down emissions, revises some of the coefficients and presents the calculation methodology so that future studies can easily incorporate changes in the technical coefficients that are considered convenient. 3 - Methodology The IPCC (Intergovernmental Panel on Climate Change) Top-Down methodology makes the accounting of the primary and secondary fuel that are introduced in the economic system in order to satisfy the needs of the human activities (even the non-commercial ones) and of how much carbon leaves the system. Once introduced in the national economy, in a determined year, the carbon content of a fossil fuel either is emitted to the atmosphere or is retained in some way, for example, through the increase of fuel stock, its transformation in non-energy products or its partial retention in non-oxidized form in the combustion residues. The use of the Top-Down (TD) methodology recommended by IPCC in its 1996 revision permits to estimate the CO2 emissions as a function of data regarding the energy supply in the country and a few data concerning their form of use. The data used are from BEN (National Energy Balance) edited by the Ministry of Mines and Energy – MME. The values supplied by BEN are originally given in natural units that correspond to those used in their origin (mass in tons and volumes in cubic meters). In some cases, where energy sources are grouped, the units used are ton equivalent petroleum (tep) and a special criterion must be established for calculating emissions. The Top-Down (TD) methodology calculates the Apparent Consumption of a country by energy source from the equation: Apparent Consumption = Production + Imports – Exports – International Bunkers + Stock Variation In practice this concept coincides with data from the Total Internal Supply BEN/MME where: Total Internal Supply = Production + Imports – Exports (in BEN Bunkers are included) – Non Used – Re-injection The “Non Used” and “Re-injection” concepts refer specifically to the Natural Gas accounting that, as will be examined below, can be separately treated. However, in order to calculate using the TD process, production excludes re-injection of Natural Gas in the wells and the non-used energy (gas flow to the atmosphere or burned in flares during extraction are not accounted for by TD and are treated separately). This equivalence will be shown below when a practical case will be analyzed. In a simplified way, the Top-Down methodology can be described as follows: a) Calculation of fuels apparent consumption in their natural measurement units; b) Conversion of the apparent consumption to a common energy unit - terajoules(TJ); c) Transformation of the apparent consumption of each fuel to carbon content by multiplying by the specific emission factor of that fuel; d) Calculation of the carbon amount of each fuel destined to non-energy utilization and subtraction of that amount from the carbon of the apparent consumption in order to calculate the real carbon content that can be emitted; e) Correction of this value in order to consider the incomplete combustion, calculating the true carbon quantity that is actually oxidized in the combustion f) Conversion of the oxidized carbon to CO2 emissions. In the adopted methodology, the emissions are calculated by multiplying the values - expressed in energy relative to the final use of the energy sources and some transformation – by coefficients adequate to the fuels used in Brazil or default coefficients recommended IPCC. 4 - Use of the ben_eec Program in the Ca;culation of Carbon Content 4.1 calculation of Energy Data Using the ben_eec Program The BEN / MME (49 sectors and 46 accounts) data base supplies data in natural units from 1970 until 2005. These data are annually published and constitute the National Energy Balance presently elaborated by the Energy Research Enterprise – EPE, for the Ministry of Mines and Energy - MME. The ben_eec program whose operation manual was presented in the Technical Note 3, annex to the Report No1 of the Partnership Contract E&E/MCT, was previously developed by ECEN Consultoria Ltda for the Economy and Energy Organization e&e. This program was already used in several energy planning studies and it is available at http://ecen.com in the previous version. The present version improves the calculation structure and facilitates the data revision. Using original data expressed in natural units (mass, volume or, in case of aggregations, in ton equivalent petroleum – tep) and coefficients for each energy source and year, the program converts data to energy units (Mcal) using energy/mass or energy/volume coefficients. Presently, the MME used as base the low heat value (LHV) but previously the values were given in high heat value (HHV). These data are used in the conversion of the usual data from the energy source balance that is the ton equivalent petroleum presently defined as: 1 tep = 10.000 Mcal with the energy content measured in LHV values Previously, BEN/MME used the relationship: 1 tep (old) = 10.800 Mcal with the energy content measured in HHV values Furthermore, the adopted equivalence for electricity took into account the quantity of fuel oil necessary for generating electricity. Presently, the conversion is made directly in energy. Thus the following equivalence: 1 kWh=860 kcal=0,086 tep (new) Previously, the adopted equivalence was: 1 kWh was equivalent to 3132 kcal = 0,29 tep (old) The previous literature (such as reference document concerning the initial inventory of greenhouse effect gases emissions) used old units such energy coefficients relative to HHL and values in tep (old). For this reason, the program supplies to the user results in this unit and in tep (new) and LHV. It should be noted that the LHV and HHV are not equivalent and may have other applications for the user. The ben_eec program also converts energy to equivalent energy (that takes into account the average relative efficacy of the energy sources in each sector) and in carbon content that is used for calculating emissions and test the coherence based on the conservation of carbon atoms in the involved chemical reactions in the use of the energy source. The MME supplies annually the values used in the conversion to tep. This means that the old tep and HHV coefficient values are available until 2002. As these values were subsequently converted to new tep, the new tep and the implicit LHV values are also available for all years. Based on these values of the LHV/HHV ratio for each fuel and extrapolating to the years subsequent to 2002 it is possible to supply data for all the years in the old and new units. For each j fuel and i year, there is a coefficient c(i.j) such that [Energy in tep] (i,j) = [Quantity in Natural Units] (i,j) × c(i.j) Furthermore, the r(i,j) = [Energy in new tep](i,j) / [Energy in old tep ](i,j) ratio permits to convert from new tep to old tep and, based on the energy equivalence previously mentioned, it is possible to supply the energy values in Mcal for both the LHV and HHV. This conversions are automatically carried out by the program. Besides that, the ben_eec software permits to construct tables chosen by the user and make several aggregations, including renewable and non-renewable energy that are important regarding emissions accounting. In Table 4.1 it is illustrated how the program calculates the values in different energy equivalence in the different presentation formats. In this technical not are not shown examples regarding electricity, hydraulic and nuclear energies that are of no interest to the present study since in these cases there is neither carbon content nor emissions directly involved. Table 4.1: Illustration of calculation carried out by the ben_eec program in energy and carbon conten
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