Economy & Energy
Year IX -No 62:
June - July 2007 
ISSN 1518-2932

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Presentation of the Preliminary Version of Carbon Balance for Discussion

Carbon Balance

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Carbon Balance

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Annexes  1970- 2005

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Text for Discussion :

Carbon Balance

Summary

1.Introduction.

2. Methodology.

2.1 Carbon Balance.

2.2 Emissions by the Top-Down Extended Methodology.

2.3 Greenhouse Effect Emissions in the Bottom-Up by Coefficients Methodology.

2.4 Biomass Treatment

3. Carbon Emission.

3.1 Data Aggregation and Chosen Years.

3.2 Emissions Calculation.

3.3 Sectorial Carbon Emissions.

3.4 Carbon Emissions by Fuel Type.

3.5 Summary of Carbon Emissions.

4. CO₂ Emissions.

4.1 Carbonic Gas Accounting.

4.2 Comparison with the Inventory Values.

4.3 Form of CO₂ Balance Presentation.

4.4 Evolution of CO₂ Emissions by Fuel

4.5 Evolution of CO₂ Emissions by Sector (Account)

4.6 Summary of CO₂ Emissions.

5. CH₄ Emissions.

6. CO Emissions.

7. NMVOCs Emissions.

8. Results and Methodological Apendix.

9 Using the bal_eec Program to Obtain Results.

10 Acronyms and Symbols Used

 1.Introduction

Brazil participates in the United Nations Framework Convention on Climate Change and had committed itself to carry out periodically a survey of the anthropic emissions of greenhouse effect gases.

The Ministry of Science and Technology – MCT, is responsible for the coordination of this study that includes several governmental and private organs.

An important part of emissions from human activities is related to energy production, transformation and use. In order to evaluate these emissions it is necessary to use the data from the National Energy Balance – BEN, edited by the Ministry of Mines and Energy for more than thirty years and now under the responsibility of the Energy Research Enterprise – EPE.  

The Energy Balance is based on an important characteristic of energy, namely its conservation, established by the First Law of Thermodynamics. It permits to make a balance considering energy in its primary forms (petroleum, wood, hydro energy, natural gas, mineral coal, etc.) and its transformation that converts it to secondary forms easier to use (gasoline, charcoal, electricity, coke, etc.) that are finally used in the different sectors of human activities (residences, industries, vehicles, etc.)

Most of the greenhouse effect emissions are related to gases that contain carbon (mainly carbon dioxide and methane). The so-called fossil energy sources (mineral coal, petroleum and natural gas) have their energy stored in carbon molecules taken from the atmosphere by the photosynthesis effect.

The carbon mass in these processes, as it happens with energy, is also conserved and so it is possible to make a Carbon Balance in the energy sources activities and in other types of activity where there is gas emission. In all complex chemical reactions regarding raw material (e.g.: petroleum), its transformation (in refineries) and finally its emission to the atmosphere at the final use as a gas (mainly CO₂) and considering a small amount of retention, the carbon mass follows the Lavoisier Principle: it is transformed, it is not created and it does not disappear.

Carbon Balance  in energy activities can be, as it is the case in Energy Balance, an important evaluation and planning instrument regarding emissions associated with energy. Carbon Balance gives a historical photograph (rather a film) along the years of emissions in the energy area in the Brazilian territory that contribute to the greenhouse effect. For each year it gives emissions maps by energy sector and for each type of gas. 

For the first time the Balance presents a historical view of emissions by energy source and by activity of the different gases in the 1970/2005 period. On the other hand it points out the important role of biomass in Brazil where carbonic gas is initially removed from the atmosphere and is emitted later on, most of it in the form of CO₂. In the exports of energy sources from biomass, the “negative emissions” will be credited to the Brazilian energy activities. The calculation of the Carbon Balance has also permitted the identification of several errors and omissions regarding the emissions of greenhouse effect gases.

The presentation of emissions in the form of Carbon Balance unifies the Top-Dow approach that measures the quantity of carbon that “enters” the system, and the Bottom-Up approach where, considering the sectors of the human society activities, it is identified the type of emission per energy source using data concerning the performance of the equipment utilized. In the present study the Bottom-Up analysis was carried out using emission/energy coefficients for each sector and energy form calculated by the MCT for the 1990/1999 period. The emission of gases containing carbon (CO₂, CH₄, CO and NMVOCs[1]) is calculated by extrapolating these coefficients for the previous and subsequent years of the mentioned period. The values should be considered only as indicative ones, since it is assumed a “freezing” of the technologies used.

The inclusion of data from the Useful Energy Balance, also organized by the MME, associated with data relative to the equipment used in each sector and each use per energy source, will permit to produce more reliable data about these emissions that could be included in future calculations.

Calculations are carried out by a software that is easy to use and where more complete data referring to the 1970/2005 period are available.

This study was possible due to the Partnership Contract 13.0020.00/2005 signed by the Economy and Energy – e&e – OSCIP Organization and the Ministry of Science and Technology – MCT.

2. Methodology

The detailed methodology to obtain the data is described in the reports of the Partnership Contract between e&e and MCT relative to Carbon Balance Consolidation. A summary is presented in what follows.

2.1 Carbon Balance

                Schematically the original energy data are converted to carbon mass through the use of carbon mass /energy coefficients for each energy source. These coefficients are given in tC/toe (ton of carbon per ton oil equivalent)^[2]. The carbon masses so obtained are accounted for in the same way as the Energy Balance accounting summarized in Figure 1:

Figure 1: Scheme of the National Energy Balance used for carbon mass

However, it should be noticed that the so called “losses” in the case of energy balance should be found in thermal energy as in the case of electricity power plants or leakage or escape in the use and transport of energy fuels. In the case of carbon balance most of these losses return to the atmosphere and should be accounted for in the emissions. In the example of the power plants there is no carbon in the generated electricity and all carbon mass of the fuel used should be accounted for in the emissions.

Since the Energy Balance is not concerned in principle with the carbon mass balance, it would be no surprise at all that when the usual coefficients are used (recommended as default values by the Intergovernmental Panel on Climate Change – IPCC, or those specific for Brazil) some differences are found, some of them significant, between the carbon mass of the primary energy and that of the secondary one and the carbon mass accounted for in the different uses. The carbon balance analysis made it possible a series of corrections in the mass/energy coefficients based on studies  that involved mainly biomass and its products.

Once the carbon balance is established, it is possible to evaluate the emissions considering that all carbon has been converted to CO₂except for a small fraction of the fuels used (around 1%) that is not oxidized and is supposed not to return to the atmosphere. There is also a fraction that is not used as energy source and is retained and integrated in materials where retention is considered definitive. This methodology is called Top-Down by the IPCC and will be briefly described below.

2.2 Emissions by the Top-Down Extended Methodology

The use of the Top-Down (TD) methodology recommended by the IPCC in its1996 revision permits to estimate CO₂ emissions as a function of data concerning only the energy supply in the country and a few data about the form in which it is used. This methodology consists of accounting the primary and secondary fuels that enter the economic system of a country to satisfy its needs generated by human activities (even the non-commercial ones) and how much carbon leaves the system. Once introduced in the national economy in a given year the carbon contained in a fossil fuel is either emitted to the atmosphere or is retained in some way; for example, it is added to the fuel stock, it is transformed into non-energy products or it is partially retained in non-oxidized form in combustion residues. The energy data used are taken from the BEN.  

The Top-Down (TD) methodology calculates the Apparent Consumption of a country per energy source using the formula;

Apparent Consumption = Production + Imports – Exports      
– International Bunkers + Stock Variations

Practically this concept coincides with that of the Total Internal Supply of BEN/MME where:

Total Internal Supply = Production + Imports – Exports (in BEN it includes Bunkers) + Stock Variations - Non Used – Re-injection

The “Non-Used “ and “Re-injection” concepts refer specifically to the accounting of natural gas that normally is treated separately in the TD process. In the Carbon Balance the re-injection of natural gas into the wells was excluded and the non-used energy (gas that escapes to the atmosphere or is burned in flares during extraction) was accounted for in the present version as entirely converted to CO₂.

In a simplified way, the Top-Down methodology suggested by the IPCC can be described as follows:

Calculation of the carbon mass of each fuel in a common energy unit – terajoules (TJ);

Calculation of the carbon quantity of each fuel to be used in non energy ends and subtraction of this carbon mass amount (given by a coefficient for each non energy use) in order to determine the real quantity of emitted carbon;

For fuels to be used for energy purposes, the amount of fuel that is non-oxidized in the combustion will be subtracted using oxidizing factor ;

The oxidized carbon quantity is converted to CO₂ emissions by multiplying the carbon mass by 44/12^[3].

In the methodology used here emissions are considered at the consumption level instead of in the total energy supply one. In the case of petroleum, for example, the emissions in the TD process would be calculated as the carbon contained in petroleum minus 1% of retention (factor commonly used for liquid fuels). Part of the petroleum is converted into naphtha that is used for non energy ends and one fraction is not emitted; this retention is subtracted separately. That is, the petroleum item is responsible for a large part of the TD accounting emissions. In the TD Extended process adopted in the Carbon Balance there are no emissions assigned to petroleum but they are assigned to its products in each sector where they are used. The non-oxidized fraction is also calculated based on the fuel (primary or secondary ) consumption in the sector where it is used (e.g. 1% of gasoline in road transport).

The carbon emission so calculated can be converted to CO₂ as in the Top-Down process. The calculation has shown that the two methodologies are equivalent in terms of global emissions if emissions associated with losses and adjustments are considered ^[4].

2.3 Greenhouse Effect Emissions in the Bottom-Up by Coefficients Methodology

The option adopted in the Carbon Balance was to use energy/emission coefficients of specific gases (CO₂, CO, CH₄ and NMVOCs) taken from the Bottom-Up approach to account for their emissions.

For the Brazilian Initial Declaration to the United Nations Framework Convention on Climate Change (MCT, November 2004), the General Coordination of Global Climate Change – CGMGC/SEPED/MCT consolidated the inventory of emissions that contribute to the greenhouse effect. The inventory’s data were arranged ^[5] in the form of emission/energy coefficients where it was possible to obtain the emission of the different gases, using data from the National Energy Balance – BEN/MME, in mass of each one of them; then they were transformed in fractions of emitted carbon for each gas and applied to the carbon mass obtained by the mass/energy correspondence, as summarized below.

The emitted gases that contain carbon, except the NMVOCs, have a well known relationship between the carbon mass and the total one, namely:

CO₂ →c1 = 12/44

CO   →c2 =12/28

CH₄ →c3 = 12/16  

For the NMVOCs it was assumed a fraction of carbon mass (c4=0,85) based on the average emissions in industry.

If m1, m2, m3 and m4 are the masses of those emitted gases, one has the carbon mass conservation:

m1.c1 + m2.c2 + m3.c3 + m4.c4 = MC*(1-fnox-fret)

where, MC is the carbon mass in the fuel used in the sector minus the non oxidized fraction (fnox) and the retained one (fret).

In general, the fuel fractions chosen are those recommended by the IPCC taking into account some Brazilian peculiarities, most of them concerning biomass. In most cases it is 1% for liquids and 0.5% for gases. The non-oxidized fractions (energy products) and those retained (non-energy products) are shown in item 8. It should be noticed that the retention factor was supposed = 1(by default), that is 100% retention in the cases where its value is not known so that eventual non energy uses in previous years when emissions were not calculated may be detected^[6].

Emissions of waste from alcohol production, composed mainly of CO₂ from  the fermentation of molasses and sugarcane liquor, were also calculated.

The emission coefficients of the Bottom-Up process supplied by the staff of the Inventory Emissions were presented in the usual BEN structure. The Ministry of Mines and Energy supplies the Balance’s original data in an amplified structure of 49 “accounts” and 47 energy sources that was used in the Carbon Balance. The coefficients used for gases emissions were expanded and the values available for the aggregate as those of its components were adopted^[7] so that this structure could be used.

The emission coefficients supplied by CGMGC/SEPED/MCT referred to energy balance data available at the time of the Inventory that still used the HCP ( high calorific power) concept and ton oil equivalent (old toe = 10800 Mcal) in the denomination adopted in the present report. The emitted carbon fraction was calculated using these data. The carbon mass fraction does not depend on the energy unit and the conversion to carbon mass is carried out for each energy source using the new values already adopted by BEN from 2003 on, base year 2002, using the low calorific power and 1toe = 10000 Mcal.

2.4 Biomass Treatment

The CO₂ emissions are the main purpose of the present report since it has been detected that for different energy sources the sum of carbon atoms in emissions corresponded to values that exceeded 30% the carbon contained in the fuel. This is due to double inclusion that is somehow inherent to the IPCC approach where the CO₂ emission data from the Top-Down approach are used as those of the Bottom-Up approach. This procedure produces some doubts concerning the results, since the emissions of other carbon compounds can be added to evaluate the greenhouse effect.

The option adopted here separates the emissions as it is supposed to happen in their origin. So the CO₂, CO, CH₄ and NMVOCs emissions are estimated so that the sum of carbon mass is equal to that contained in the fuel and subtracting the retained and oxidized carbon.

In the carbon balance approach it should be taken into account that in the production of the raw material the carbonic gas of the atmosphere is absorbed. The biomass production is therefore accounted for as “negative emission”. The inclusion of this negative emission makes it clear the role of biomass and its emissions avoiding the incorrect use of emissions from biomass^[8].

However, in the sectorial evaluation it should be clear the separation between emissions from biomass and that from fossil fuel. An alternative adopted here in some cases is to represent the “negative emissions” referring to biomass production in the energy sector.

3. Carbon Emission

3.1 Data Aggregation and Chosen Years

A summarized picture of emissions expressed in carbon mass can be produced by choosing some sectors and grouping the energy sources. The following sectors were chosen:

·          Amplified energy sources (production, transformation and use in the energy sector);

·          Residential;

·          Commercial and Public;

·          Agriculture and Husbandry;

·          Transports and

·          Industrial.

The fuels were aggregated in:

·          Biomass;

·          Natural Gas;

·          Petroleum and Products of Petroleum and Natural Gas;

·          Mineral Coal and Products.

1994 (last year of the initial inventory) and 2005 (last year with data available from BEN) were chosen as reference years.

3.2 Emissions Calculation

The bal_eec software, developed by the ECEN Consultoria Ltda, was used for the emission calculation; it is a modification of the program previously developed for calculating the balance in equivalent energy.

The program was modified so that, besides the energy, equivalent energy and carbon balances, it could calculate emissions of the greenhouse effect gases CO₂, CH₄, NMVOCs, CO, NOx and N₂O per energy source and per account.

The program permits to construct tables for the above mentioned gases using specific coefficients for the 1990/1999 period that are extrapolated for the other years. It can construct tables and graphics for the different accounts and energy sources for each one of the GHE gases.

The program also calculates emissions of greenhouse effect gases (CO₂, CO, CH₄, NMVOCs) from energy activities. Furthermore, it calculates emissions of nitrogen compounds that are of no interest for carbon balance but contribute to the greenhouse effect. The sum of the carbon contained in these gases is the carbon emitted to the atmosphere.

3.3 Sectorial Carbon Emissions

In Table 3.1 it is shown for the years 1994 and 2005 the sectorial emissions that contribute to the greenhouse effect (non-renewable sources).

The shares of the different sectors in the emissions of 1994 and 2005 are compared in Figure 3.1. The two more important sectors are Transport and Industrial that maintained their share, 40% and 31%, respectively. Transport and Industry are responsible for 71% of carbon emissions from energy activities. Of the other sectors, the energy one had a higher share (from 12% to 17%) and in absolute value its emissions have doubled from 1994 to 2005. The other sectors reduced their share in emissions, particularly the Residential one where emissions remained practically stable in absolute terms (4,200 Gg/year). The residential sector decreased its share from 7% to 5%. The growth of the energy sector was mainly due to the higher use of thermal energy that almost tripled in the considered period. The consumption growth in transport was headed by road transport. In Industry the sectors that contributed most to emissions were those connected with metallurgy, particularly pig iron, that grew 312% in the considered period.

Table 3.1 Carbon Emissions by Sector (Gg/year) 1994 and 2005

Figure 3.1: Comparison of the sector’ shares in the emissions of greenhouse effect in 1994 and 2005

The largest share in Industry is that of the steel sector (pig iron and steel) that in 1994 was responsible for half of the emissions. There was a decrease in the shares of this activity but it still is the main responsible for emissions in Industry.

The carbon emissions variation (non-renewable sources) by sector can be seen in Table 3.2 and in Figure 3.2.

Table 3.2 Carbon Emissions by Sector, Non Renewable Sources,
 1970 /2005 Period in Gg/year

In Figure 3.2 it can be observed the effect of the second petroleum prices shock (1979) that lead to significant changes in fossil fuel consumption. The growth crisis at the beginning of the 2000s and the following petroleum price shock also affected emissions. The structural changes that were characterized by the Real Plan (1994) produced a significant growth in the Transport emissions (increase of the vehicle fleet and reduction of the alcohol share) as well as the already mentioned larger use of electric thermal generation.

Figure 3.2: Evolution of carbon emission from fossil sources where it can be noticed the  influence of the petroleum shock  on oil prices and on the economy

Table 3.3 Carbon Emissions by Sector, Non Renewable Sources and Biomass,
 1970- 2005 Period in Gg/year

In Table 3.3 the emissions by sector of the renewable sources and biomass from 1970 to 2005 (every 5 years) are presented. The biomass production is included with a negative sign in the emissions relative to biomass production. The calculated total is rather lower than the emissions of renewable sources because part of the captured carbon does not return to the atmosphere, according to the adopted retention hypothesis (due to non oxidizing and non energy use).

3.4 Carbon Emissions by Fuel Type

Figures 3.3 and 3.4 show the shares in the total emissions by type of fuel, including biomass, with indicative representation (transparent) that should not be accounted for in the calculation of greenhouse gases. It should be observed in the figures that the 1979 and the present petroleum price shocks have caused a return to the use of biomass whose historical trend has been that of reduction.

In Figures 3.5 and 3.6 the shares in carbon emissions are compared with shares in energy (measured as total energy supply) by energy of origin. It should be noted the vigorous penetration of natural gas. It is also noticeable the different shares of natural gas and mineral coal in emissions and energy, explained by the carbon content per energy unit, namely 15.3 tC/Tj for natural gas and 25.8 tC/Tj (69% larger) for mineral coal.

Figure 3.3: Total carbon emissions, including that of biomass that are presented as transparent to show that it does not contribute to the greenhouse effect 

Figure 3.4: Share of energy activities in the total carbon emissions where it is evident the effect of petroleum prices in the intensification of its use at the start of 1990s and 2000s

Figure 3.5: Share of fossil fuels in the generation of greenhouse effect gases, with percent indication for the year 2005

Figure 3.6: Share of fuels (energy)in the total energy supply; it should be noted the minor relative importance of coal and the major importance of natural gas relative to the previous  graphic (emissions)

In Figures 3.5 and 3.6 are shown the percent shares of fuels regarding emissions and energy in the last year (2005). For the petroleum and natural gas products they are equal (in the adopted approximation). For natural gas the energy share is 17%, higher than that of emissions (14%); the opposite occurs for mineral coal that has a share of 11% in energy and 16% in emissions. This difference is due to the coal’s higher carbon content per unit energy relative to natural gas.

Tables of emissions by fuel and sector in 2005 are shown in item 8 (total values). In item 8 are also shown the annual carbon balance (carbon content in fuels) and carbon emissions. The tables for all years are available at http://ecen.com.

Table 3.4 : Carbon Emissions, for the 1970 -2005 period
 by fuel, in Gg/year

3.5 Summary of Carbon Emissions

Table 3.5 and Figure 3.7 summarize carbon emissions by sector and fuel type in the year 2005.

Table 3.5: Summary of Carbon Emissions for the 2005 year in Gg/year

Figure 3.7: Summary of Carbon Emissions in the year 2005 in Gg/year

4. CO₂ Emissions

4.1 Carbonic Gas Accounting

The CO₂ emissions are those with the highest mass involved and they give the largest contribution to the greenhouse effect due to their long stay in the atmosphere and they are the main subject of the present report. These emissions were those that had major corrections relative to the values of the Initial Inventory as the adjustments of excess emitted gas mass were made on the CO₂ mass.

The option adopted in the Balance was to separate emissions as it is supposed to happen in the origin. Therefore the data cannot be directly compared with the CO₂ mass calculated by multiplying the emitted carbon mass by 44/12.

It is taken into account that the gas is absorbed by the atmosphere in biomass production as raw material. In the accounting of greenhouse effect gases emissions this absorption should be accounted for as negative CO₂ emission. The inclusion of this negative emission shows more explicitly the role of biomass and its emissions, avoiding the unjustified use of emissions from biomass.

However, in the sectorial evaluation it should be clear the separation between emissions from biomass and those from fossil fuels. An alternative, adopted here, is to represent “negative emissions” in the energy sector regarding biomass production.

4.2 Comparison with the Inventory Values

Comparisons with the Inventory values should be made based on emissions assigned to “non renewable” sources. This comparison is made in Table 4.1 for the years 1990 and 1994 and for the 1990/1994 period. Some considerable differences deserve comments:

·          In natural gas it was included emission due to the “non used” item (NG burning) that was considered as totally composed of CO₂ in a preliminary approach. Fundamentally it is natural gas burned in the platforms or wells due to transportation difficulties or other operational reasons. If these emissions are not considered, the difference between the calculated value and that of the Inventory is 6%.

·          The discrepancy regarding gasoline exist because in the Inventory the CO₂ emission corresponds to the total carbon contained in the fuel. As the carbon quantity emitted in the form of CO is 34.9%, besides 2.8% emitted in the form of CH₄ , there is a overestimation of 40% in the sum of contained carbon. 

·       In coke oven gas there was a significant change in the mass/energy coefficient, as indicated in the e&e report relative to Goal 2 (issue N⁰ 60 of the e&e periodical).

·          In general the emission values are lower (in 5%) than those of the Inventory because they do not consider the carbon fraction of the other emitted gases.

·          In the “Others” item there was a different allocation of energy sources.

Table 4.1: CO₂ Emissions Calculated and Published in the Inventory –
Comparison by Energy Source - Non Renewable Sources - Unit: Gg/year

In Table 4.2 the data by sector are compared with those of the Initial Inventory.

Table 4.2: CO₂ Emissions Calculated (Non Renewable) and Published in the Inventory –  Comparison by Sector - Gg/year

4.3 Form of CO2 Balance Presentation

Table 4.3 summarizes for the year 2005 the emissions presentation form that takes into account the absorption of carbonic gas from the atmosphere by biomass that represents, in the adopted systematic, the negative emissions of carbonic gas. The production of renewable sources has a negative sign. Added to non used natural gas, one has emissions up to the energy balance line denominated total energy supply^[9].

It could be expected that the non renewable column would be equal to zero since after biomass utilization it is supposed that the carbon returns to the atmosphere. However, it should be remembered that part of the biomass is not oxidized and would not return to the atmosphere (by the adopted systematic) as it happens with all fuels. The coefficients used for solid biomass have a typical value of 0.87 which means that 13% of the total processed would be permanently subtracted from the atmosphere^[10]. In the CO₂ accounting one should also consider that part of the carbon was substituted in the atmosphere by other compounds that contain carbon and in the long term they are transformed into CO₂. In the data of Table 4.3 the quantity that did not return to the atmosphere in the form of carbonic gas is about 8% of the removed mass.

Tables with similar details as those of the Annual Energy Balance are presented in item 8 at the end of the present report.

 Table 4.3: Summary Table of CO₂ Emissions in the Year 2005

4.4 Evolution of CO2 Emissions by Fuel

Table 4.4 summarizes CO₂ emissions for chosen years in the 1970/2005 period. Figure 4.1 shows the evolution of CO₂ emissions separated in renewable and non renewable sources. It should be noted that the negative value for renewable sources is justifiable by the adopted criteria, namely assign as negative the “emissions” in the biomass production.

                Figure  4.1 CO₂ emissions for renewable and non renewable sources where it can be noticed the negative values for renewable ones due to carbon absorption by the atmosphere which is not completely compensated by emission in the energy use due to partial retention (non oxidized or non energy applications) and due  to carbon emitted as another form of gas

Table 4.4: CO₂ Emissions by Fuel for the 1970/2005 Period in Gg/year