Gregg Marland

Carbon dioxide emission rates for conventional and synthetic fuels

With rising concern about the increasing atmospheric concentration of CO2 and its potential impact on global climate, there have been suggestions that the CO2 emission rates be considered in selecting among fuel-producing technologies. Many previous comparisons have been inadequately drawn. We discuss criteria for carefully drawn comparisons and compute CO2 emission rates in kgC/109 joules for a variety of conventional or synthetic fuel processes. Although the total CO2 release per joule is on the order of 1.8 (±0.2) times as much for burning liquid fuels from coal as for liquid fuels from crude oil, useful comparisons among synthetic fuel processes are not easy and the results are subject to changes in boundary conditions of resource availability, plant location, environmental requirements, output slate desired, economics, etc.

Fossil Fuel Combustion: Recent Amounts, Patterns, and Trends of CO2

Several types of human activity have introduced perturbations that impinge on the natural global carbon cycle. During the past century or so, one of the major perturbations has been the release of carbon from long-term storage through the combustion of fossil fuels. During the next 100 years fossil fuel use will almost certainly be the major source causing increased levels of CO2 in the atmosphere.

Constraints on Fossil Fuel Use

The exponential growth of fossil fuel use over recent decades has resulted in a 4.3 percent annual increase in the carbon dioxide emitted to the atmosphere. The question addressed here is: When (and to what extent) will constraints limit the use of fossil fuels and the subsequent production of CO2? We discuss three types of possible constraints: resource constraints, fuel demand constraints, and environmental constraints. An analysis of the next 50 years suggests that resource constraints will not provide severe limits. The impacts of atmospheric carbon dioxide will not reach levels that cause mankind to take action soon. Fuel-demand constraints will probably limit the use of fossil fuels to levels that keep the atmospheric carbon dioxide concentration below 450 ppm(v) for the next 50 years. In spite of this conclusion we see a continuing, long term problem and urge that full efforts be made to understand and continually monitor the CO2 problem and to be alert to any changes that may require action.

Greenhouse gases in the atmosphere: what do we know

In addition to carbon dioxide there are a number of gases (e.g., N/sub 2/O, CH/sub 4/, CF/sub 2/Cl/sub 2/, CFCL/sub 3/, etc.) which could affect the radiation balance of the earths atmosphere. Recent measurements indicate that the atmospheric concentrations of these gases are increasing. Incomplete understanding of the sources, sinks, and/or chemical interactions of these gases in the atmosphere makes it difficult to relate human activities to future concentrations and to climatic effects. Atmospheric modeling suggests that during the past decade the trace gases should have had a warming effect that was half as much as CO/sub 2/. To illustrate the magnitude and complexity of the human involvement, the authors reviewed the budget of N/sub 2/O in the atmosphere. Anthropogenic production of N/sub 2/O occurs primarily in the combustion of fossil fuels and in the use of nitrogen fertilizers but acid rain, sewage treatment, electric power transmission, forest clearing, and other activities all impact the global N/sub 2/O budget. Although estimates of N/sub 2/O sources are subject to large uncertainty, the total anthropogenic contribution may be approaching 50% of the natural releases.

The question mark over coal: Pollution, politics, and CO2

Abstract There is a growing concern about the effect of fossil-fuel burning, and the consequent increase in carbon dioxide (CO 2 ) concentration in the atmosphere. This increasing concentration is now well-documented, and although the evidence of actual or potential climate changes is not conclusive, the growth in energy consumption magnifies the importance of the possible dangers. This article highlights two aspects of the issue. The CO 2 increase will be mainly produced by coal. And whereas the increase in atmospheric CO 2 is now being imposed upon the world principally by the USA, the USSR, and Western Europe, the developing countries will probably be important contributors by early in the next century. Using world energy resource estimates and projections of the global production of CO 2 from fossil-fuel burning in the year 2025, the authors argue that it will be difficult to achieve an international consensus and commitment to deal with the issue. This is because of the relationship between economic growth, industrialisation, and the production of CO 2 , and because of the distribution of the beneficial and harmful effects of any climatic change.

Net energy analysis of in situ oil shale processing

Although the domestic resources of shale oil are large, there has been some question regarding the magnitude of the energy subsidy that must be committed in order to extract the contained oil. This study shows that for a 50,000 b/d, modified in-situ extraction facility in 20-gal-per-ton Green River Shale, the energy yield is about 8.6 times the energy subsidy and that about 21 percent of the in-place oil can be thus recovered. If the mined-out shale is retorted at the surface rather than being discarded, the recovery factor rises to 37 percent and the net energy ratio should rise significantly as well. It is difficult to compare these figures with those for aboveground retorts because oil burned in place for retorting never enters the energy accounts. However, the resource commitment per unit of recovered energy is more easily compared and is essentially indicated by the reciprocal of the recovery fraction.

Prospects for the near-term commercialization of shale oil in the United States

Although the United States has large resources of shale oil, several decades of development effort have yet to result in a viable industry. Because both the cost of the oil and the environmental impact of its production are not well known and seem to remain perennially at the margin of acceptability, the matter of commercialization has become a political issue. A variety of economic incentives and government programs to encourage commercial development have been proposed—some implemented—and several industrial corporations are proceeding cautiously. Conflicting political, economic, and environmental views, however, continue to preclude a decisive commitment, and it does not appear at this time that significant quantities of shale oil will be available in the next decade or probably even longer.