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This chapter de-mystifies respirometry equations, showing how they can be derived using a simple mental trick: concentrating the analysis on the principal gas that is neither consumed nor produced by animals. The effect of dilution of oxygen by carbon dioxide, the enrichment of carbon dioxide by the consumption of oxygen, and the effects of water vapor on the concentrations of both gases, are described and quantified. A system of eight equations is derived that allow oxygen consumption and carbon dioxide production to be calculated in practically any feasible flow-through respirometry system.

Coal has two main energy applications, with about 90% used for electricity generation and 10% used for commercial and residential heating. In terms of electricity generation in the United States, coal is responsible for about 28%, a significant decrease from 53% twenty years earlier when it was the leading energy for producing electricity. There are two primary commercial methods for generating electricity from coal including pulverized coal combustion and fluidized bed coal combustion. To safely burn coal, sulfur, nitrogen, and heavy metals are removed at the electric plant. The sequestering of sulfur and nitrogen are important steps for limiting acid rain and ground level ozone. To generate electricity, the United States has about 360 coal plants with about 790 generators, of which greater than 90% use pulverized coal technology. Most coal is transported by rail.

Natural gas, which is primarily methane, is used in the electric power industry, various industrial applications, residential heating, and, to a small extent, as a transportation fuel. In terms of electricity generation for the United States, natural gas is responsible for about 35%, a large growth from only 15% twenty years earlier. In 2015 natural gas overtook coal and is now the primary energy for producing electricity. It is a relatively clean burning energy type and, compared to coal and petroleum crude oil, it contains small amounts of sulfur and nitrogen and no heavy metals such as selenium, mercury, and cadmium. To support the use of natural gas to generate electricity, the United States has about 1,800 plants with close to 6,000 generators and 1.6 million miles of pipelines.

By using modern gas analyzers and variations of constant volume techniques described in Chapter 2, simple and high-throughput measurement of the metabolic rates of organisms ranging in size from bacteria to large insects and even small vertebrates are easily implemented. It is also possible to measure water loss rate and carbon dioxide production using only an oxygen analyzer. These respirometry techniques can be deployed in the field as well as the laboratory. Both manual and automated, computerized implementations of constant volume techniques for metabolic rate measurement are covered in full step-by-step detail, and appropriate analytical protocols for oxygen, carbon dioxide, or both oxygen and carbon dioxide analysis systems are also described in detail.

This chapter demystifies respirometry equations, showing how they can be derived using a simple mental trick: focusing the analysis on the principal gas that is neither consumed nor produced by animals. The effect of dilution of oxygen by carbon dioxide, the enrichment of carbon dioxide by the consumption of oxygen, and the effects of water vapor on the concentrations of both gases are described and quantified. A system of eight equations is derived that allow oxygen consumption and carbon dioxide production to be calculated in practically any feasible flow-through respirometry system.