We derive our energy from many resources with varying environmental challenges related to air and water pollution, land use, carbon dioxide emissions, resource extraction, supply, and related safety and health issues. Each resource needs to be evaluated within the sustainability paradigm. Coal (45 percent) and gas (23 percent) are the two primary fossil fuels for electricity production in the United States. Coal combustion produces nearly twice the carbon emissions of gas combustion. Increasing public opinion and regulatory pressure to lower carbon emissions are shifting electricity generation toward gas and away from coal. Oil for transportation and electricity generation are the two biggest primary energy users and producers of carbon emissions in the United States. Transportation almost completely depends on oil and internal combustion engines for its energy. Oil concentration in a few world regions creates a transportation energy security issue. Nuclear electricity offers the sustainable benefit of low-carbon electricity at the cost of storing spent fuel out of the environment for hundreds of thousands of years. Reprocessing spent fuel offered the advantages of higher energy efficiency and reduced spent fuel storage requirements with the disadvantage of a higher risk of weapons proliferation through the diversion of the reprocessed fuel stream.
Strong interest in renewable energy arose in the 1970s as a response to the shortage and high price of imported oil, which disrupted the orderly operation of the economies and societies of many developed countries. Today there are new motivations, including the realization that growing greenhouse gas emission accelerates global warming and threatens climate change, the growing dependence of many countries on foreign oil, and the economic drain of foreign oil payments that slow economic growth and job creation. There are three ultimate sources of all renewable and fossil energies: sunlight, the heat in the earth’s core and crust, and the gravitational pull of the moon and sun on the oceans. Renewable energies are relatively recently developed and typically operate at lower efficiencies than mature fossil technologies. Like early fossil technologies, however, renewables can be expected to improve their efficiency and lower their cost over time, promoting their economic competitiveness and widespread deployment. The future deployment of renewable energies depends on many factors, including the availability of suitable land, the technological cost of conversion to electricity or other uses, the costs of competing energy technologies, and the future need for energy.
EEA. (2013). Combined heat and power. Retrieved from http://www.eea.europa.eu/data-and-maps/indic ators/combined-heat-and-power-chp-1. Available under Creative Commons Attribution License 3.0 (CC BY 3.0). Modified from original.
Theis, T. & Tomkin, J. (Eds.). (2015). Sustainability: A comprehensive foundation. Retrieved from http://firstname.lastname@example.org. Available under Creative Commons Attribution 4.0 International License. (CC BY 4.0). Modified from original.