|Fig. 1: Average Tomato Plant Growth Over a 6 Week Period in Hveragerdi, Iceland.  (Source: A. Makalinao)|
Since the 1970s, geothermal energy has been lauded as a readily available, low-carbon energy source that can one day replace fossil fuels as a baseload energy supply. However, geothermal energy also has the potential to serve several other facets of society. Due to the unique nature of the energy source, geothermal power has the ability to provide new opportunities to the industries of agriculture, aquaculture, batteries, minerals, and mining.
Within the United States, there are currently 37 greenhouse sites that utilize geothermal energy (13% of total geothermal energy use) with an installed capacity of 119 MWt. Greenhouses as a whole have been shown to be one of the largest low-enthalpy consumers in agriculture, and the addition of geothermal energy only magnifies these benefits since low-enthalpy geothermal is widely available across the U.S. 
In geographical locations with colder climates, several commercial crops such as tomatoes are raised within greenhouses to more easily regulate temperatures. Geothermal direct use has the opportunity to aid in greenhouse processes for long-term payback and low carbon intensity. To quantify these benefits, a study in Hveragerdi, Iceland using geothermal heating was performed in 2009 (Fig. 1); the study resulted in increased average crop height for geothermally heated tomatoes in 3 out of 4 soil types, suggesting that controlled geothermal heating can act as a potential augmentation to current agricultural practices. 
In 2010, 22 countries reported the use of geothermal-enhanced aquaculture with the leading countries being China, USA, Italy, Iceland, and Israel.  The United States utilizes 58 aquaculture sites with an installed capacity of 140 MWt. Aquaculture currently boasts a 35% usage rate of geothermal energy, the largest when compared to other industries supported by geothermal. 
Similar to agricultural trends, geothermal aquaculture has been shown to improve yields of fish and other aquatic animals. The regulated temperatures of geothermal energy lead fish to grow larger in size and reduce rates of disease and death within fish populations. Geothermal aquaculture as a whole has the potential to pair well with current energy production. Water that has been used for heating or electricity can be transplanted to heat fish ponds at virtually no cost. Recent studies have shown thermal energy savings can be as high at 75-85%. 
|Fig. 2: Lithium-ion battery. (Source: Wikimedia Commons)|
Lithium-ion batteries (Fig. 2) are a current form of energy storage in many emerging technologies. Past market projections estimated that lithium-ion batteries had the potential to grow from $877 million in 2010 to $8 billion in 2015; however, the intensive thermal loads required in order to create these batteries limit their penetration within the market. 
A recent study analyzing the effects of geothermal heating on these batteries showed the strong potential of the power source. The study showed that replacing conventional heat with geothermal heat would reduce costs from $0.13/Ah to $0.008/Ah. In addition, the internal rate of return was estimated to increase by 12% while carbon dioxide emission reduced by over 95%. 
Although energy production is the primary objective of geothermal extraction, there is a potentially lucrative market beyond energy. After geothermal heat is successfully removed for use, the fluid is often treated and re-injected back into the ground. Within the geothermal fluid, however, there are plenty of valuable metals such as silica, lithium, manganese, zinc, and sulfur that can be extracted for the global market. 
Silica, the most common metal found in geothermal fluids, shows the most potential within the marketplace. A study involving a Salton Sea 50 MWe power plant and a similarly sized facility in Coso, California, showed profits of $10.2 million per year and $12.9 million per year, respectively, from silica extraction alone. 
The current regulations behind mining, primarily from the Mining Act of 1872, have led to the economic centricity of the industry; however, new trends within energy and the environment are causing a gradual shift of the mining industry to cleaner energy sources. Geothermal energy has a very unique opportunity to serve the entirety of the industry.
Within production stages, geothermal fluids can be used directly to heat metal liquids in copper production and enhance heat leaching for rare earth extraction. Geothermal direct use can also provide heating to reduce energy loads in mines located in colder climates. Ultimately, switching to geothermal energy has huge potential for lowering the environmental impacts of mining within the public eye. 
Due to high upfront cost and lack of high heat reservoirs, geothermal growth within the U.S. and several other countries is often stagnated. However, emerging technologies within the geothermal field present many opportunities beyond energy production. The industries listed above as well as several others often utilize low heat geothermal power, which is more readily available throughout the world. In order to improve geothermal prospects globally, it is important that all aspects of geothermal energy be taken into consideration.
© Aloysius Makalinao. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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