Introduction to greenhouse gas markets and cap-and-trade
Most production processes create by-products as well as the intended product. Some of these by-products have value (e.g., distiller dried grains, a by-product of ethanol production, have value as a livestock feed); others are considered waste and entail an expense for their disposal. Frequently the least expensive way to dispose of by-products has been to release them into the environment. Examples include the emissions of sulfur and particulate matter into the air when burning coal to create electricity and the introduction of chemicals into rivers through sewer systems.
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