Venezuela: Preliminary National Greenhouse Gas Inventory

Martha Perdomo

Nora Pereira

Yamil Bonduki

Ministry of Environment and Renewable Natural Resources
Ministry of Energy and Mines

SUMMARY: This paper presents a summary of the "Preliminary Inventory on Sources and Sinks of Greenhouse Gases in Venezuela," whose final version will be submitted to the United Nations Framework Convention on Climate Change (UNFCCC), as an official document of the Venezuelan Government. This inventory is one of the components of the National Study to Address Climate Change. The gases included in this inventory are carbon dioxide, methane, nitrous oxide, nitrogen oxides, carbon monoxide, and nonmethane volatile organic compounds. Chlorofluorocarbons are excluded as they are controlled by the Montreal Protocol. Table 1 provides a summary of greenhouse gas emissions by source category. The energy sector is the most important anthropogenic source in the country. Emissions mainly come from the use of energy as fuel, land-use change, and from fugitive emissions generated by oil and gas production. Carbon dioxide is the most important gas, its emissions originate primarily from fuel combustion and forest clearing.[Table 2] Methane has also an important contribution to national emissions of greenhouse gases, and it originates primarily from oil and gas production and agricultural activities. This national inventory represents a valuable tool to predict future greenhouse gas emissions under various economic development scenarios and to identify the best mitigation strategies that the country could implement to reduce its emission levels.


Atmospheric concentrations of greenhouse gases have been increasing as a result of a wide range of human activities and have become particularly noticeable after the 1950s. This increase is believed to alter the redistribution of energy in the atmosphere and, consequently, affect climate by altering some related natural phenomenon, such as the mean global temperature, and changes in frequency and distribution of precipitation, circulation and weather patterns, and hydrological cycle, among others.

The possibility of a global climate change, as a result of anthropogenic emissions of greenhouse gases, has become a major concern within the international scientific community in the last few years. Such concern was the basis for the creation of the Intergovernmental Panel on Climate Change (IPCC) and for the process of international negotiations that led to the approval of the United Framework Convention on Climate Change (UNFCCC). The Government of Venezuela also signed the Convention which was ratified by the National Congress on December 1994.

As the Convention requires all parties to develop and publish national inventories of anthropogenic greenhouse gas emissions as well as national plans to reduce or control emissions, the Ministry of Environment and Renewable Natural Resources and the Ministry of Energy and Mines developed the Country Study to Address Climate Change. The study was initiated in October 1993, with the financial and technical assistance of the Government of the United States, through the U.S. Country Study Program (USCSP), and the Global Environmental Facility (GEF), through the United Nations Environmental Programme (UNEP).

A team of experts from several Venezuelan ministries and institutions are in charge of conducting this study, with the following objectives:

A study of this kind is very important for a developing country like Venezuela, whose current national plans include programs of industrial development, increased public services, and expansion of petroleum industry activities. All of these national development programs will likely increase greenhouse gas emissions, unless programs of conservation, efficient use of energy, and methane gas control are implemented simultaneously. These development plans have also affected forest areas extensively as the establishment of a wide range of economic activities have been traditionally linked to land clearing.

The final project reports are intended to be released as official documents of the Government of Venezuela as a first step to implementing the guidelines set forth in the United Nations Framework Convention on Climate Change.


The estimation of emissions from all sources was based on the methodology provided by the IPCC Draft Guidelines for National Greenhouse Gas Inventories (IPCC/OECD, 1994). Some default values provided by the methodology for specific variables and emission factors were used in the inventory as local data were not always available. In many cases, the required data were specifically generated for the inventory through literature search, site visits, or interviews with experts. In a few cases, specific studies were performed in order to produce or validate some of the data.

The results of this inventory are also presented in accordance with the IPCC guidelines, following the reporting instruction tables. Besides the analysis and estimates of 1990 greenhouse gas emissions and sinks, the document to be submitted to UNFCCC provides a global picture of the main anthropogenic activities responsible for these emissions in the country and a description of particular situations that could introduce additional elements in the inventory process. It also provides specific discussions on methodologies, data used, and information sources for each category.

The international standards set for the inventory process, based on a common methodology, seek to ensure that all mechanisms and approaches adopted by the countries to evaluate their greenhouse gas emissions are consistent and transparent and that their results can be compared on a systematic manner.


The following section summarizes the emission estimates and presents a brief discussion on the relative importance of each source category within the national inventory of greenhouse gas emissions.

Carbon Dioxide

Carbon dioxide contributes to nearly one third of the natural greenhouse effect. A continuous increase of its concentration in the atmosphere, produced by anthropogenic activities, has been observed from the beginning of the industrial period. At a global level, since then, the concentration of carbon dioxide has increased by more than 25 percent, mainly due to the use of fossil fuel. Venezuela generated 190,813 Gg of carbon dioxide in 1990. The main sources are energy-combustion and land-use change (Figure 1).

Energy Sector
The use of fossil fuels constitutes the main anthropogenic source of greenhouse gases. Within this, carbon dioxide is the most important contributor; emissions of this gas occur during the combustion process, when the carbon contained in the fuel is combined with oxygen. The quantity of carbon in fossil fuels varies significantly by fuel type. Coal contains the greatest amount of carbon per unit of energy, while crude oil and natural gas contain 25 percent and 50 percent less than coal, respectively.

In Venezuela, the energy sector emitted 107,334 Gg of carbon dioxide in 1990, which represented 56 percent of national emissions of this gas. Energy combustion generated 105,976 Gg (98.7 percent of the energy sector), while gas flaring in the oil and gas systems produced the remainder 1,358 Gg (1.3 percent of the sector).

Carbon dioxide emissions from combustion are mainly caused by the use of oil and natural gas. The former generated 53,313 Gg, while emissions from natural gas were estimated to be 50,742 Gg, which represented 50 percent and 48 percent of these emissions, respectively. Coal represented only 2 percent of these emissions since coal consumption in the country is very low. Regarding emission estimates of carbon dioxide by sectors, as shown in Figure 2, the emissions come mainly from the transportation sector (36 percent) and the operations of the energy industry (38 percent).

Stationary Sources. In 1990, stationary sources emitted 51,560 Gg of carbon dioxide, mainly from the use of oil (31 percent) and natural gas (67 percent). The greatest amount of emissions within the stationary sources corresponds to the energy industry, which generated 30,516 Gg. The sources of emissions in this industry are related primarily to electricity generation (19,519 Gg) and oil and gas production (10,997 Gg).

The second largest source is the manufacturing industry, which generated 16,775 Gg of CO2. Most of these emissions come from energy used for steam generation (41 percent) and direct heat (44 percent). The industrial categories that produce the greatest quantities of emissions are: basic metallic; food, beverages and tobacco; chemicals and nonmetallic mineral industries, which all together generated 86 percent of the emissions from the manufacture sector.

The residential sector generated 3,678 Gg of CO2 while the commercial and service sectors emitted 572 Gg. Regarding the fuel types used in this sectors, petroleum is the main emitter, followed by natural gas.

Mobile Sources. The 1990 emissions of carbon dioxide from mobile sources were estimated to be 29,205 Gg; 88 percent corresponds to national transportation and the remainder to different types of international transport. Gasoline vehicles are the most important emitter, with 21,760 Gg.

Emissions from national transportation are basically generated by road transportation (93 percent). The emissions released from private vehicles are the most important within this sector, with 10,593 Gg of carbon dioxide in 1990, which represented 39 percent, followed by the emissions from heavy duty trucks, with 27 percent. Emissions from public transportation are the least significant, as they only contributed with 14.4 percent.

Land-Use Change and Forest Management
Human activities that alter the biosphere for food, fuel, and fiber production have been increasingly contributing to the concentration of greenhouse gases in the atmosphere. Carbon dioxide is considered to be the most important gas associated with land-use changes. Three categories are considered in the national inventory: forest clearing, forest management, and conversion of grasslands to cultivated lands. Land-use change is largely responsible for greenhouse gas emissions in Venezuela. The forest conversion process that the country has witnessed during the last decades has increased significantly as land pressure to establish different economic activities has determined the fate of large forest areas. Furthermore, land clearing for agricultural use is the most important activity leading the process of land-use change.

Forest Clearing. The forest area of the country is roughly 58 million hectares, which represents more than 60 percent of the national territory. About 70 percent of the forest land is found in the south of the country, where the Venezuelan Amazonian Basin is located.

The annual rate of forest clearing in Venezuela has not been consistently documented. The country was divided into three main geographical regions, according to specific sources of information on forest-clearing rates: Northwest, northeast, and south, in order to derive an average deforestation rate. The analysis estimated an average cleared area of approximately 517.000 hectares per year (excluding the southern region), which represents a deforestation rate of less than 1 percent per year. This value was used to provide an approximation of greenhouse emissions in the country due to forest clearing until a more detailed study on deforestation rates at a national level is performed. An initiative is already being coordinated to achieve this goal in the near future.

The amount of carbon dioxide emitted by forest clearing has been estimated to be 84,792 Gg in 1990, which represents about 44 percent of national CO2 emissions. Being one of the most important sources of carbon dioxide and other gases as well as one of the most complex areas, a number of issues will still need to be refined in order to improve the estimates and update the inventory.

Managed Forests. Carbon dioxide uptake from managed forests has been estimated to be 5,380 Gg in 1990, which represents an offset of about 6 percent and 3 percent of CO2 emissions from forest clearing and all sources, respectively. Although its importance as a carbon dioxide sink may not seem relevant within the national greenhouse gas emission context, the potential contribution of forest management to offsetting CO2 emissions is quite large. The total forest area managed by commercial forest product industries during the 1970‹ 90 period has reached 215,000 hectares. On the other hand, forest plantations have reached, for the same period, about 430.000 hectares. More than 90 percent of the area corresponds to commercial plantations while the rest has been established for protection purposes.

Conversion of Grasslands to Agricultural Lands. Conversion of grasslands to cultivated lands is not a significant source of carbon dioxide in the country, as agricultural activities have been rather marginal within the national economic development context. Most of the agricultural activities in these areas are related to extensive cattle raising, which does not involve land tilling. However, some important crops have been established on open savannas, especially during the 1984‹ 89 period, when government subsidies resulted in a substantial increase of agricultural production. Based on local data for soil carbon content, the estimated net converted area, and a rate of soil loss carbon of 2 percent per year, emissions were calculated to be 1,200 Gg of carbon dioxide. As the data used are not very reliable, the result obtained is highly uncertain and should be viewed as a general approximation of the magnitude of emissions from this source.


Methane is the second most important gas responsible for global warming, accounting for about 15 percent of the "radiative forcing" added to the atmosphere in the 1980s, at a global level. Methane levels are increasing substantially, as its concentration have more than doubled in the past 300 years and continue to increase by about 1 percent per year. Although global methane emissions are much smaller than global carbon dioxide emissions, its overall contribution to global warming is large since it is 22 times more effective at trapping heat in the atmosphere over 100- year time horizon when direct and indirect effects are accounted for.

Methane emissions in Venezuela were estimated to be 3,168 Gg for 1990. The major anthropogenic sources are: fugitive emissions from production and processing of oil and natural gas and emissions from agricultural activities (Figure 3).

Energy Sector
The energy sector emitted 1,838 Gg of methane in 1990, which represented 58 percent of national methane emissions. Fugitive emissions are the most important source of this gas with 99.3 percent while fuel combustion only generated 0.7 percent.

Oil and gas systems are the main methane emitters, especially during production activities, which generated around 83 percent of the total fugitive emissions. Emissions corresponding to processing, transportation, and distribution of natural gas represented 17 percent. The contribution of coal mining is very small, due to the low level of production of this fuel in the country.

The use of fossil fuel in transportation is the most important source of emissions of the non-CO2 originated by combustion, mainly those generated by incomplete combustion, such as methane. The mobile sector is the second largest emitter of methane with 9.8 Gg, representing 81 percent of combustion emissions; gasoline vehicles produced the biggest amounts, especially private vehicles, which generated 4.9 Gg.

Methane is the most important greenhouse gas produced by the agricultural sector and is responsible for the emission of 951 Gg, which represents 30 percent on the national methane emissions. Management of domestic livestock and animal manure contributes 90 percent of the methane emissions from agricultural activities. Rice cultivation and savanna burning are a less important source of methane, releasing 7 percent and 3 percent of the emissions from agricultural activities, respectively. Field burning of agricultural residues are a negligible source of methane and other greenhouse gases as this practice is not common in the country.

Enteric Fermentation. Emissions from enteric fermentation in domestic animals are estimated to be 826 Gg of methane, which represents about 26 percent of national methane emissions and 87 percent of methane emissions from agricultural activities. The more detailed approach of the IPCC methodology, referred to as Tier 2, was applied in order to derive methane emissions from cattle. Dairy and beef cattle are the major contributors, accounting for 97 percent of total emissions from enteric fermentation. Methane emissions from other domestic animals include buffalo, sheep, horses, swine, goats, mules, and asses. The approach used to calculate the emissions from these noncattle sources was based on the Tier 1 method, and consequently a less detailed analysis was performed. Methane emissions from these animals have been calculated to be 23.2 Gg, about 3 percent of methane emissions from enteric fermentation in all domestic animals.

Manure Management. Methane emissions from animal manure are estimated to be 26.7 Gg, which represents only 3 percent of the total amount generated by domestic livestock and less than 1 percent of national methane emissions. Manure in the country is usually not treated or stored in anaerobic environments. Thus, almost all livestock manure is managed as solid on pastures and ranges. Of the different animal categories included in this estimate, cattle and swine manure are the most significant emitters, accounting for approximately 55 percent and 34 percent of total methane emissions from animal manure, respectively.

Rice Production. Rice fields generate about 67 Gg of methane per year and represent 2 percent of national methane emissions. Rice is one of the country's major crops and most of its production is concentrated in two regions with similar climate patterns and cultivation practice. Rice fields are commonly irrigated or rainfed with a depth of less than one meter of floodwater, which is a basic condition to generate methane through the anaerobic decomposition of organic matter in the fields. Although some variations were found in the number of days flooded per year, this period has an average of nearly 90 days, corresponding to a continuously flooded regime. Rice is not cultivated under intermittently flooded or dry regimes in the country.

Savanna Burning. More than one-fourth of the country (approximately 22 million hectares) is covered by savannas, found in most geographical regions, but mainly in the Llanos of the central part of the country. Extensive cattle raising has been traditionally established on savanna areas, which involves burning during the dry season, as a common agricultural practice to eliminate weeds and pests and encourage growth of new grass. This periodical burning of a great portion of savanna areas releases important non- CO2 trace gases. Carbon dioxide, which is also emitted in large quantities, is not taken into account in the greenhouse gas inventory for this sector because it is reabsorbed by the vegetation regrowth between the burning cycles. Methane emissions from this source were estimated to be 31 Gg, which represents only 1 percent of methane national emissions.

The proportion of the savanna areas burned in Venezuela is highly uncertain as there are not reliable national statistics that compile, on a regular basis, the frequency and extent of savanna burning. Consequently, a satellite imagery study (Landsat TM, 1:250.000 scale) was performed on about half of the savanna area of the country in order to determine this figure. An extrapolation of the study's results indicates that approximately 3.1 million hectares of savanna are annually burned, which represents only 13 percent of the country's savanna area. These results are very controversial as the proportion of savanna burned appears to be very low, especially when compared to the regional data provided by the IPCC methodology. From this source, savannas are burned worldwide every 1 to 4 years on average (IPCC/OECD, 1994).

Burning of Agricultural Residues in the Fields. The contribution of this source to greenhouse gas emissions in the country is rather negligible as only 0.2 Gg of methane were generated by agricultural waste burning. Most of the agricultural residues are not burned since they are commonly used to feed cattle and other animals or plowed back into the field during land tilling. The only two crops whose residues are indeed burned for different reasons are sugar cane and cotton. Sugar cane fields are traditionally burned before the harvest for both practical and safety reasons. Cotton residues are also burned but mainly for sanitary reasons in order to eliminate any possible pest or weed that may affect the health and yield of the following crop.

Landfills do not constitute a significant source of methane in the country since a great fraction of solid wastes is still disposed of in open dumping. Sanitary landfilling generates 221 Gg of methane, which represents about 7 percent of national emissions. Twenty landfills were identified, with a wide size range. The smallest of these receives an average of less than 3,000 Ton of solid wastes per year while more than 1 million Ton per year are placed in the biggest landfill. The latter alone, which serves the capital's metropolitan area, accounts for more than 40 percent of the total landfilled waste in the country.

Other Sources
Other activities that generate methane in the country are related to land-use change and wastewater management. Biomass burning that occurs in conjunction with forest clearing has been included in the national inventory. Emissions from this practice were estimated to be 158 Gg, which represents nearly 5 percent of national methane emissions. This estimate will be updated once the deforestation rate data are validated. Wastewater treatment is a negligible emitter of greenhouse gases as only 0.2 Gg of methane were generated by this source.

Nitrous Oxide
Nitrous oxide is another important infrared absorbing trace gas that contributes to the greenhouse effect. According to the World Meteorological Organization (WMO) its current atmospheric concentration is about 8 percent greater than during the preindustrial era. Nitrous oxide is approximately 270 times more powerful than CO2 at trapping heat in the atmosphere over a 100-year time horizon. The current rate of accumulation of N2O in the atmosphere is about 0.2 percent to 0.3 percent per year.

Although the estimates are relatively uncertain, nitrous oxide emissions in Venezuela were calculated to be 4.54 Gg for 1990. The most important contributor is the agricultural sector, especially the use of fertilizer (agricultural soil management). Nitrous oxide is also produced directly from biomass burning in the nonenergy sector and combustion of fossil fuels (Figure 4). Nevertheless, the mechanisms that cause its formation from these sources are not well understood. N2O production is highly temperature-dependent.

Energy Sector
The Venezuelan energy sector is the least important contributor to nitrous oxide emissions with 0.64 Gg, representing 14 percent of the national emissions in 1990. Within this sector, 66 percent comes from mobile sources, especially road vehicles (93 percent); the highest proportion corresponds to heavy-duty trucks. Contrary to the industrialized countries estimates, where fuel consumption, mainly from aged 3-way catalytic converters, is an important emitter, in Venezuela this source is the least relevant since the vehicle fleet has not yet incorporated catalytic converter control.

Stationary sources emitted 0.22 Gg of nitrous oxides (34 percent of the combustion emissions) where 46 percent comes from energy and transformation industries, 38 percent from manufacture industry, and 18 percent from residential and commercial sectors.

Agricultural Soil Management
In 1990, nitrous oxide emission from the use of chemical fertilizers were estimated to be 2.3 Gg. This is the main source of nitrous oxide in Venezuela, and represents 50 percent of total N2O emissions in the country and approximately 85 percent of the agricultural sector's emissions. Organic fertilizers are not included in this estimate due to the lack of the required data. Although some crop residues and animal manure are used in certain agricultural fields, this type of fertilizer does not usually enter the commercial market, and consequently, no reliable source of information is available to estimate the total amount of organic fertilizer and the equivalent nitrogen content.

Other Sources
Other sources of nitrous oxides in the country are related to biomass burning as a result of land use change and agricultural practices. Both forest burning that occurs in conjunction with land clearing and savanna burning account for 1.2 Gg of nitrous oxide, which represents about 27 percent of this gas national emissions. Agricultural waste burning is a negligible source of nitrous oxide.

Carbon Monoxide and Nonmethane Volatile Organic Compounds

Carbon monoxide and nonmethane volatile organic compounds (NMVOCs) are unburned gaseous fuels that are emitted in small quantities due to incomplete combustion. They contribute to the formation of urban smog and hence they have been the target of emission control policies in some countries. The impact of these gases on global climate is indirect. The most important of these effects is their role as precursors of tropospheric ozone. In this role, they contribute to ozone formation and alter the atmospheric lifetimes of other greenhouse gases. However, many uncertainties are associated with quantifying the indirect effects.

Carbon monoxide emissions in Venezuela were estimated to be 4,101 Gg for 1990, where agriculture acclivities and land use change contributed with 55 percent while energy combustion represented 45 percent of national emissions (Figure 5). All nonmethane volatile organic compounds are emitted by the transport sector, which generated 250 Gg in 1990.

Energy Sector
In energy combustion, emissions of these gases are directly influenced by usage patterns, technology type and size, vintage, maintenance and operation of the technology, and usage patterns. Emissions can vary by several orders of magnitude for facilities that are improperly maintained and poorly operated such as the case of many older units. Carbon monoxide emissions from the Venezuelan energy sector were basically generated by the transport sector, which produced 98 percent; the remainder 2 percent corresponded to stationary sources, especially from the manufacture industry. It is important to mention that almost all emissions of carbon monoxide (98 percent) and NMVOCs (96 percent) are generated by gasoline vehicles.

The need to manage a wide range of variables and the numerous conditions that could affect the yield of each mobile sources category, especially those related to road transport, make very difficult any attempt to generalize the emission characteristics in this area. A similar situation is observed for stationary sources since the emission factors provided by the IPCC methodology are not sufficiently disaggregated. Some adjustments were made in order to perform the emission estimates.

Savanna Burning
Savanna burning represents an important source of carbon monoxide in the country. This agricultural practice generates 820 Gg or 20 percent of national carbon monoxide emissions. However, since the proportion of savanna burned calculated for the country is believed to be underestimated, the emissions from this source could increase significantly once more reliable data is incorporated in the national inventory. If the default value of 50 percent burned on average per year is used to perform the estimate, as provided by the IPCC methodology for the Latin American region, carbon monoxide emissions from this source would be four times higher than the result obtained in this preliminary inventory. This issue will need further discussions in order to provide a more reliable estimate of greenhouse gases from savanna burning.

Land-Use Change
Forest burning that occurs in conjunction with land clearing is responsible for more than a third of the national carbon monoxide emissions, as 1,380 Gg of the gas were emitted from this source in 1990. Contrary to savanna burning, emissions from this source may be overestimated as a result of the rather high value obtained for deforestation rate in the country. Although the average cleared area used for the inventory still does not cover the entire country, discussions with several experts have pointed out the fact that some methodological limitation of the deforestation rate study may be responsible for inconsistencies in the results. An initiative is already underway to clarify this issue in the near future.

Nitrogen Oxides

Nitrogen oxides have been the target of environmental policies for their role in forming ozone, as well as for their direct acidification effects. NOx are also produced by incomplete combustion. In Venezuela, NOx emissions in 1990 were estimated to be 360 Gg, generated mainly by combustion of fossil fuels, with 90 percent of national emissions of this gas. The remainder 8 percent corresponded to biomass burning in the nonenergy sector (Figure 6).

Energy Sector
Similarly to carbon monoxide and NMVOCs, nitrogen oxides are a technology-dependent gas. Their emissions depend in part on the nitrogen contained in the fuel. Electricity generation and industrial fuel combustion activities also provide combustion conditions conducive to NOx formation. Excess air and high temperatures contributes to high NOx emissions. They are also produced from incomplete combustion.

As mentioned above, the most important NOx source is the combustion of fossil fuels, with 126 Gg from stationary sources and 199 Gg from mobiles. Electricity generation contributed with 55 percent of the emissions from the stationaries. In mobile sources, 98 percent was produced by road transportation where the principal source is gasoline heavy-duty vehicles.

Other Sources
As in the case of nitrous oxide, biomass burning associated to land- use change and agricultural practices constitutes another source of nitrogen oxides emissions. Forest burning that occurs in conjunction with land clearing, savanna burning, and agricultural waste burning account for 25 Gg of nitrogen oxides, which represents about 8 percent of this gas national emissions.


This preliminary national inventory provides a comprehensive picture of Venezuelan greenhouse gas emissions and constitutes a powerful tool to evaluate and plan the best mitigation strategies that the country could develop to reduce and control its emission levels. Nevertheless, some weaknesses and limitations still represent an important problem to be addressed in order to improve the reliability of the information used as well as the methodologies applied in some cases.

Most source categories are likely to present qualitative and quantitative limitations reflected in the calculation of greenhouse gas emissions. However, the uncertainties associated with the emission estimates were not quantified due to the limited available information and the difficulty of identifying the level of reliability for most of the data used in the inventory. Besides limitations associated with the methodology, the poor quality of some of the data is probably highly responsible for the uncertainties of the results. Special efforts should be made in the near future to solve this crucial issue and produce more accurate national estimates.

In the case of the energy sector, indepth studies have already been initiated for the main carbon dioxide emission sources, with the objective of validating the data and generating more appropriate emission factors. Similarly, as land- use change represents a significant source of carbon dioxide, an effort to determine more reliable data on deforestation rates is being coordinated by the Ministry of Environment and Renewable Natural Resources. Methane emission estimates could also be improved through the implementation of specific projects to generate additional and more reliable data for the oil and gas industry‹ the main source of methane. A project will be formulated shortly to address this issue in conjunction with the Venezuelan Oil Industry.


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March 1995

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