EDUCATION: GLOBAL METHANE INVENTORY

Assessing Methane Emissions from Hard Coal

By A. Adams

Note: The following is a student paper which has not been published or peer-reviewed. It is made available for archival purposes only. All results are preliminary. Please do not reference the paper for results or statistics.

1. Introduction

Methane is a greenhouse gas that has a key role in the greenhouse effect despite its low atmospheric concentration Methane is vital in absorbing high amounts or infrared radiation; on a molecule by molecule basis it is more efficient than carbon dioxide (CO₂). Because methane is a greenhouse gas it is significant as a contributor to global warming. The Global Methane Inventory project precisely takes account of the amount of methane that causes the atmosphere to deteriorate gradually. In past investigations, researchers have estimated methane emission rates for rice cultivation, ruminant animals, landfills, and the largest contributor natural wetlands. These major sources displayed results that ranged from stable to unstable. For instance the results for cattle show the emission rates to be sporadic while, the landfills shown results that have a steady increase.

Compared to previous research, determining methane emissions rates from fossil fuels, in general, for the past twenty years, it is reasonably innovative. This type of research has never been implemented. It seems unrealistic for scientist not to engage in this research topic, despite its significance. It is not a straightforward process, as one would assume. There are a number of factors one must take into consideration when doing so.

This particular project looks into methane emissions from fossil fuels between the years 1980 and 1998. More specifically, estimating methane emissions from hard coal. Hard coal is found in underground mines. Methane is released from coal in processes known as normal operations. And the degree of coalification determines the amount of methane generated (EPA 2Energy).

2. Data and Methodology

2a. Methodology

Provided by the methodology of the Intergovernmental Panel on Climate Change (IPCC) calculations for hard coal emissions could be carried out. The IPCC Revised Guidelines workbook supplied factors to estimate the amount of methane is emitted for hard coal during processes like storage, production, transported, and or venting directly into the atmosphere. Production, imports, exports were the specific processes we examined.

The IPCC's 1996 Revised Guidelines workbook on energy instructs us to multiply the total amount of a certain type of coal with an emission factor (depending on region or on the quality of the coal) and then with a conversion factor. This will not give you the entire amount of methane. Hence we are specifically observing the production, which is referred to as mining as well as post mining activities, because production alone could not truly show how much methane is emitted from coal mining. The following equation is the one that was provided by IPCC:

Emissions (Gg CH4) = Emission Factor (m3 CH4 / ton of coal) × ton of coal produced × Conversion Factor (Gg/106 m3 )

 

The amount of methane liberate during mining is primarily dependent upon the amount of methane stored in the coal and the surrounding strata (EPA). The emissions factor tells you per every 1,000 tons of coal, there is a cubic meter of methane produced. Also, since methane is a gas it cannot be measured in meters. The conversion factor converts the cubic meters of into a unit in volume, which was gigagrams (10¹² grams). IPCC provided emission factor for only the few countries listed in table 1. In addition, the EPA provided China's emission factor. Using the range from IPCC Revised Guidelines workbook (10-25) a mean default value of 17 m³ CH₄/ton coal found. This default value was used for the remaining countries.

                                                Table 1 - Methane Emission Rates from Hard Coal

Aside from estimating the amount methane that is emitted from coal production, we calculated the emission rated for post mining activities. These are series of processes that the coal is put through after the production stage. Such activities include ansportation, storage, importation, and exportation. The same equation that was referred to earlier for production was used for post mining activities. Estimating methane emissions from mining activities will not provide the total amount, so post-mining is vital. In the sense that is will differentiate a high emission rate from a very low one.

2b. Data

Statistics were also used from the dataset of the International Energy Agency (IEA). The IEA is a large international organization that is widely used for energy statistics. Data on coal production, imports, and exports was gathered for approximately 140 countries. Being that this is to some extent, a new topic, there are a few downsides. The fact that there are not available results to fairly compare with ours and that there is a chance that there is an error or flaw in the statistics we are using.

3. Results

3a. Global Trends

Figure 1a shows that the production of hard coal in general experienced a steady increase. Graph 1a. shows the production of coal in between the years of 1980 and 1985 decreasing and rising steadily. After 1985 coal production has had a general increase except in 1993 where production declines a few 1,000 tons. Production overall has a 30% increase between 1980 and 1998.

Post-mining emissions as in Figure 2 were low in the sense that it did not exceed 10 Tg. Post-mining emissions, overall, were flat. But if you notice in the 1980's emissions went from 6.5 Tg to about 8 Tg. And in the 1990's it went from 8 Tg to about 8.3 Tg. This tells us that the methane emissions grew faster in the 1980's.

Figure 2a shows trends in global CH₄ emissions very similar to the production plot. Figure 2a shows emissions from hard coal between 1980 and 1985 experiencing a general increase. There was a slight decline in 1983 that ended the next year. Just as Figure 1a emissions grew faster in the 1980's. Figure 2a illustrates in 1980 emissions being 30 Tg and in 1989 40 Tg. In 1990 emissions are at 40 Tg and by 1998 rates barely reach 45 Tg.

3b. Regional Trends

Methane emissions varied from region to region. For instance, in Asia and Middle East CH₄ emissions contributed to the majority of the global emission rates. Figure 2b shows that CH₄ emissions had a steady increase and began to decline in 1998. Asia and the Middle East contributed to about 60% of the global emissions.

Africa (Figure 2c) on the other hand, did not produce much coal. Thus, did not emit as much CH₄ as in Figure 2b. The difference between Africa and Asia and Middle East is that in Africa, emissions rates increased and did not decline in 1998. It was about 10% of Asia and Middle East's total emissions. Being that Africa's emissions did not exceed 3 Tg it is a smaller percentage of the global emissions.

South America (Figure 2d) did not produce much coal, so the amount of methane that is emitted is not a large number. For instance, the scale in teragrams does not go above .0 Tg. There is a relatively flat period between 1989 and 1993. South America's emissions increased greatly but, these were in small numbers.

Unlike, South America , North America does produce a lot of hard coal and therefore the majority of methane emissions from hard coal for North America (Figure 2e). The United States for example was second behind China in production with 160,14,297 tons of coal between 1980 and 1999. This is peculiar, the US produced a lot of coal but emitted no more than 10 Tg of methane.

Europe's methane emission rates (Figure 2f) have been declining since 1989. In the beginning, it rose from about 10 Tg in 1980 to about 12 Tg in 1983. After the decline in 1984 emissions were stable until 1989. Europe contributed to about 13% of the global emissions.

Hard Coal production is not as prevalent in the Oceania (Figure 2g) region as it is in the other regions. Although the CH₄ emissions in Oceania were low, it is important to know that they contributed to a very low percentage of global emissions. In 1998, Oceania was 2.5 Tg out of the 40 Tg, which is about 1%.

4. Discussion

Methane emissions overall have increased. But emissions have slowed beginning in the 1990s. This could be the result to the slowing of the growth rate of atmospheric concentrations of methane. The only predicament with connecting the two events is that every region did not follow the same pattern as the global diagram. Europe displayed results that began to decline in 1987. The remaining regions had emissions that increased. In spite of these regions having an increase in methane emissions that did not cause the global emissions to go up.

Then the question to pose is, what is the cause of this slow growth rate in the atmospheric methane? To answer this question, one observes methane emission rates on a region by region basis. As previously mentioned, Europe's emission rates have been declining since 1989. Along with the rates decreasing Europe contributes a larger amount of methane that is released into the atmosphere. For that reason, one could have a better understanding of slow growth rate.

There is probably confusion about atmospheric concentration of methane. Post-mining emission were low, its maximum 9 Tg. The small contributor such as South America, Africa, and Oceania, if combined would not be 10% of the global emissions. Also, these small contributors increased, some even doubled but these were in small amounts. The other large contributors, North American had emissions that were stable.

5. Conclusion

Therefore, determining exactly how much methane is emitted by fossil fuels like hard coal would enable us to come to a surer conclusion as to how to control the atmospheric concentration of methane. We have knowledge that the growth of atmospheric concentration of methane, inn general, has been slowing down. The most recent measurements indicate a decrease of the global accumulation of atmospheric CH₄ during the years 1991 and 1992, and a return to 1% year increase afterward (Steele et al., 1992; Dulgokencky et al., 1994; Lowe et al., 1994) With this in mind policy makers take on the belief that they should not have to worry about changing fuel usages.

As a New York Times article displays Bush opposing to an international plan to phase out fossil fuels and increase financing to a clearer, nonpolluting energy sources (U.S. Opposes Plan for Financing of Clean Energy Over Fossil Fuels). Who is to confidently say that methane emissions are going to continue to decline. What happens when a country starts increasing coal production.

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