<\/a><\/p>\nGHG Emissions and Biomass in the Brazilian Energy System<\/h2>\nL.P. Rosa<\/h3>\n
1 – Introduction
\nFirst of all I would like to acknowledge in behalf of COPPE- the Graduate Institute of Engineering of Federal University of Rio de Janeiro the invitation to make this presentation in the seminar of this working group of IEA here in Vancouver. In the case of Brazil, environmental questions made the country the center of various international discussions, especially in relation to the devastation of the Amazon forest through burning, cattle raising and mining or the construction of large hydroelectric plants. This was an important point raised and discussed at UNCED – 92 in Rio de Janeiro, in the context of the negotiations over the Climate Change Convention. Meanwhile, CO2 emission to the atmosphere from the use of petroleum natural gas, coal, firewood and charcoal, in the Brazilian Energy Sector, has a relatively little impact. The country\u2019s electricity generation is predominantly hydro. The subject of this paper is the biomass and GHG emission in Brazil, including firewood, alcohol and sugar cane bagasse, which are important to avoid emissions from fossil fuels, but we would like to refer also to the problem of CO2 and CH4 emission through the decomposition of the biomass submerged by the dams of the hydroelectric plants in the Amazon. With respect to the ongoing international discussions, there are two noteworthy Brazilian programs for reducing CO2 emissions: the fuel alcohol program and the use of hydroelectric plants instead of plants using fossil oil for the generation of electricity. However, both are undergoing crises because the disturbing consequence of deregulation and free market international forces, which are pushing Brazil towards an increasing use of fossil fuels, which are CO2 emitters, in place of endogenous renewable energy, such as hydro and biomass, which are not. Energy use in Brazil contributes but slightly for the intensification of the greenhouse effect. Considering only CO2 emissions, COPPE’s study (Rosa and Cecchi, 1994 and Rosa and Santos, 1995) estimates 73 Mt C\/year for 1990. This corresponds to a bit over 1% of the world emissions. The relatively low contribution of energy use for CO2 emissions can be explained by the large share of hydroelectricity and of renewable biomass in the Brazilian energy matrix. More than 90% of the electricity consumed in the country is generated by hydroelectric plants. Fuel alcohol is responsible for supplying about half the energy used by Brazilian cars. Sugar cane bagasse accounts for more than 6% of the total national energy consumption. According to the above mentioned study of COPPE, in 1990, CO2 emissions in Brazil were distributed as follows by sources: Petroleum 58%; Firewood 16%; Charcoal 10%; Coal 12%; Natural gas 4% (Rosa, Schechtman and Cecchi, 1995). A common mistake is to consider firewood as being completely non-renewable, produced through deforestation and which leads to exaggerating its share in CO2 emissions. Conversely, when the influence of firewood is not taken into account, another problem arises, found in prospective projections and in the elaboration of scenarios, i.e., the sectorial distortion and that of energy sources when analyzing the impact of the Brazilian energy system on the greenhouse effect.<\/p>\n
2 – Comparative Advantage of Hydro and Biomass Energy in Brazil
\nThe Brazilian case is interesting for electricity generation and transport, because hydro and sugar-cane alcohol are used. Neither of these energy products contributes to CO2 emissions (or their contribution is so insignificant that it can be neglected for practical purposes). Energy substitution can decrease and efficiency improvement increases. Among fossil fuels, coal has the largest, while the natural gas has the smallest. Oil has an intermediate position. Combined cycle plants with gas turbines give efficiency values higher than conventional thermoelectric plants. But hydro and sugar-cane products, as well as nuclear energy, has zero emission. Assuming an average value for the CO2 emission by all energy forms with net CO2 emission we can do a rough approximation for emission calculation. For electricity generation in Brazil, the following energy sources are used: hydro (89,9%); nuclear (4.9%); oil products (2.2%); coal (1.8%); biomass (1.1%); renewable biomass (bagasse) (0.3%); natural gas (0,1%). The fraction of energy with emission in Brazil corresponds to nearly 5%, while in the USA, it amounts to almost 75%. Using the approximation above refered Brazil is therefore more efficient than the USA in respect of CO2 emissions per unit of electric energy generated (t C\/MWh) by the factor: 0.75 \/ .05 = 15. In car transport, Brazilian fuel consumption is approximately half alcohol and gasoline, while in the USA, it \/is almost 100% gasoline. So the relation between CO2 per gigajoule in the USA and Brazil is: 1.0 \/ 0.5 = 2. The above rough calculations provide only an order of magnitude. Energy policy in Brazil is changing to satisfy the present orientation of multilateral and international organizations, with the goal of reducing the state’s role in the economy. The outcome is proposals for deregulating the electric energy generation and fuel supply. A World Bank Report of 1990 has recommended that Brazil must change from hydro to thermoelectric energy, using coal, oil products and natural gas in the new plants. There are two different reasons for this recommendation. Hydro power has the inconvenience of causing environmental impacts when large dams are constructed in the Amazon, where the major part of the still unused Brazilian hydro potential is concentrated. Brazil presently uses only about 20% of this hydro potential, which amounts to 213 GW. On the other hand thermoelectricity is much more attractive to private investment in electricity generation. Although the investment cost is low, the energy price is high, depending on the cost of the fuel. It depends on the international oil price, which also exhibits strong uncertainty. A revision of the Brazilian electric energy plan, brought about by the economic and political crisis of the Brazilian state electricity companies, has decided to delay the construction of 49 hydroelectric projects for a long time span. Meanwhile, three thermoelectric plants using oil have been substituted, and four coal plants were retained in the revision (Rosa and Tolmasquim, 1993). In the same way, the use of alcohol in transport is also endangered, because it costs more than gasoline. With no government protection, the free market must induce a progressive elimination of alcohol, substituting it with gasoline. As a concrete result of the policy of weak state intervention in the fuel market, the participation of alcohol fueled vehicles in total car sales has been decreasing. It was 96% in 1985, 88% in 1988, 55% in 1989 and about 20% in 1990. In 1989-90, there was a shortage in alcohol supply, due to the government no long stimulating sugar-cane production. So deregulation and privatization of energy in LDCs could have a negative consequence for global warming since pure market forces will push out biomass and hydro. There will therefore be an increase of CO2 emission per unit of energy used if the present tendency continues.<\/p>\n
3 – CO2 and CH4 from Biomass Decomposition in Hydroelectric Reservoir in Amazon
\nIn a previous work (Rosa and Schaeffer, 1994) we have shown that the traditional GWP index for CH4 is inappropriate for dealing with emissions from hydroelectric reservoirs when comparing them with greenhouse emissions from fossil fueled power plants. The original definition of GWP for CH4 is based on the ratio of the instantaneous radiative forcing of a pulse emission of CH4 and that of an equal and simultaneous emission of CO2 integrated up to an arbitrarily determined time horizon. However, it is obvious that the pattern of gas emissions from a hydroelectric reservoir is totally different from the pattern of emissions from a fossil fueled power plant. While CO2 emissions from the combustion of fossil fuels in a thermal power plant are released uniformly over the entire period of operation of the plant, the production of both CH4 and CO2 from the bacterial decomposition of flooded forest biomass in a hydroelectric reservoir is concentrated in time and decay over a period much shorter then the lifespan of the reservoir. Therefore, in order to compare the cumulative heating effects of emitted amounts of CH4 and CO2 with each other, three factors must be considered: a) the instantaneous radiative forcing due to a unit increase in the concentration of the gases; b) the decay time functions of the gases in the atmosphere and, last but not least; c) the emission patterns of the gases. In the case of hydroelectric reservoirs the magnitude and pattern of emissions will vary depending on biomass density and type of the flooded area, soil type, length of flooding (whether continuous or intermittent) and depth of flooding. There is some consensus that greenhouse gas emissions to the atmosphere from some hydroelectric reservoirs may be far from negligible (Oud, 1993; Rudd et al., 1993). There is less agreement, however, on the cumulative heating effects of those emissions over time per unit of energy produced compared to greenhouse gas emissions by fossil fueled electricity generation (Rosa and Schaeffer, 1994). It may be worthwhile, therefore, to investigate how hydroelectric reservoirs in the Amazon region in Brazil stand against fossil fueled power plants with respect to the cumulative heating effects of greenhouse gas emissions. We have made a comparison between the integrated radiative forcing from emissions from three hypothetical hydroelectric reservoirs similar (in terms of characteristics of reservoirs and extent and types of landscape flooded) to three real hydroelectric reservoirs in the Amazon region in Brazil (two existing and one projected) with low, medium and high ratios of energy produced to flooded area, and CO2 emissions from combined cycle natural gas and coal fired power stations over two different time horizons. The reason for assuming hypothetical, rather than real, hydroelectric power stations is to allow a wide range of estimates using different biomass densities (since forest biomass varies greatly in different parts of the region) as well as different rates for bacterial decomposition of forest biomass to CH4. By applying our generalized GWP inde we have been able to express the CH4 fluxes as “CO2 equivalents” and compare their warming effects with those from the CO2 fluxes. Results are strongly dependent on assumptions and on time horizons. For reservoirs with medium and high ratios of energy produced to flooded area, the estimated integrated radiative forcing per unit of energy produced were 0.22-1.50 (Mt C pa)\/MWh and 0.04-0.25 (Mt C pa)\/MWh equivalent units respectively over 100 years. These estimates are clearly much lower than the cumulative heating effects of electrical generation by fossil fueled power plants: 4.45- 10.23 ( Mt C pa) \/ MWh. For a reservoir with a low ratio of energy produced to flooded area , however, the estimated integrated radiative forcings per unit of energy produced were 0.91-6.27 (Mt C pa)\/TWh equivalent units over 100 years. These estimates may be lower or similar in order of magnitude to the greenhouse effect of fossil fuelled electrical generation, depending on biomass density and CH4 production in the flooded area, fossil fuelled electrical generation technology and time horizon of concern. In any case, however, the longer the planning horizon the better hydroelectricity becomes and the worse thermoelectricity becames. This is a direct consequence of both the distinct pattern of emissions between hydroelectricity and thermoelectricity, and also a consequence of the different atmospheric lifetime of CH4 as compared to CO2.<\/p>\n
REFERENCES:<\/p>\n
\n- Rosa, L.P. and Tolmasquim, M.T., Energy Policy, March 1993<\/li>\n
- Rosa, L.P. and Schaeffer, R., Ambio, Vol. 23, N* 2, March 1994 and Energy Policy, Vol. 23, No. 2, 1995.<\/li>\n
- Rosa, L.P.; Schechtman, R. and Cecchi, J.C. COPPE Report, 1995<\/li>\n
- Rosa. L.P. and Ribeiro, S.K., International Environment Academy, Gen\u00e8ve, 1991; Revista Brasileira de Energia, Especial, 1992<\/li>\n
- Rosa, L.P. and Santos, M.A., Sixth Global Warming International Conference, San Francisco, 1995<\/li>\n
- Rosa. L.P. and Cecchi, J.C., Ci\u00eancia Hoje, 1994.<\/li>\n
- Oud, E. (1993) – Global warmning: A changing climate for hydro, Water Power & Dam Construction, pp. 20-23<\/li>\n
- Rudd, J.W.M.; Harris, R.; Kelly, C.A.; and Hecky, R.E. (1993), Are hydroelectric reservoirs significant sources of greenhouse gases?, Ambio 22 (4), pp. 246-248<\/li>\n
- World Bank, Report, Energy in Brazil, 1990<\/li>\n<\/ul>\n
\n
\n<\/a><\/p>\nTowards a Standard Methodology for Greenhouse Gas Balances of Bioenergy Systems in Comparison with Fossil Energy Systems<\/h2>\nB. Schlamadinger, M. Apps, F. Bohlin, L. Gustavsson, G. Jungmeier, G. Marland, K. Pingoud, I. Savolainen<\/h3>\n
In this paper, which was prepared as part of IEA Bioenergy Task XV (“Greenhouse Gas Balances of Bioenergy Systems”), we outline a standard methodology for comparing the greenhouse gas balances of bioenergy systems with those of fossil energy systems. Emphasis is on a careful definition of system boundaries. The following issues are dealt with in detail: time interval analysed and changes of carbon stocks; reference energy systems; energy inputs required to produce, process and transport fuels; mass and energy losses along the entire fuel chain; energy embodied in facility infrastructure; distribution systems; cogeneration systems; by-products; waste wood and other biomass waste for energy; reference land use; and other environmental issues. For each of these areas recommendations are given on how analyses of greenhouse gas balances should be performed. In some cases we also point out alternative ways of doing the greenhouse gas accounting. Finally the paper gives some recommendations on how bioenergy systems should be\u00a0 optimized from a greenhouse-gas-emissions point of view.<\/p>\n","protected":false},"excerpt":{"rendered":"
Forestry, Forest Products And Energy: Greening The Greenhouse Task XV: Greenhouse Gas Balances of Bioenergy Systems 30 – 31 May 1997 – Westin Bayshore Hotel, Vancouver, Canada Jointly organized by JOANNEUM RESEARCH Graz, Austria NATURAL RESOURCES CANADA Edmonton, Alberta, Canada \u00a0 \u00a0 \u00a0 \u00a0 Workshop Program FRIDAY, 30 MAY 1997 Welcome and Introduction Mike […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"acf":[],"_links":{"self":[{"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/pages\/5111"}],"collection":[{"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/comments?post=5111"}],"version-history":[{"count":9,"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/pages\/5111\/revisions"}],"predecessor-version":[{"id":5123,"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/pages\/5111\/revisions\/5123"}],"wp:attachment":[{"href":"https:\/\/task38.ieabioenergy.com\/wp-json\/wp\/v2\/media?parent=5111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}