Mexico and Costa Rica aim to build on their position as Latin America's leading producers of geothermal power to help meet the challenges they face of curbing planet-warming emissions and making their energy supplies secure.
Latin America relies on hydropower for 55 percent of its total electricity generation, and the burning of fossil fuels for around 40 percent, according to the Inter-American Development Bank.
At present, geothermal makes up only 5 percent of installed power capacity in Central America, according to the Economic Commission for Latin America and the Caribbean.
But this could change, given growing political interest in reducing greenhouse gas emissions and the goal adopted by governments in the new Paris climate change agreement to keep global temperature rise "well below" 2 degrees Celsius above pre-industrial times.
The planet's core heat delivers a clean, limitless and continual supply of energy along a string of mountains and active volcanoes in Latin America. Geothermal power is not vulnerable to the effects of climate change such as worsening droughts, or changes in the surface temperature of the Earth.
Harnessing this energy from deep under their own territories could prove a cost-effective way to power the economies of Mexico and Central American states from a domestic source, experts say.
"One of the main benefits is that countries can ... become independent from the fluctuations of foreign markets," said Emilia Rodríguez, a Costa Rican lawyer specializing in renewables. "It also supplies the cleanest and greenest energy."
Geothermal has the smallest greenhouse gas footprint per kilowatt of any power generation technology, according to the Geothermal Energy Association, an association of U.S. companies developing geothermal resources worldwide.
In 2015, 73 percent of Costa Rica's energy generation came from hydropower and 13 percent from geothermal. Even so it already ranks seventh among the 25 countries producing geothermal power, according to the International Geothermal Association.
Last year the nation's sole electricity provider went 255 consecutive days without burning any fossil fuels to generate power. The country of 5 million inhabitants wants to become the first in the world to achieve carbon neutrality, and has said it aims to do this by 2021.
Becoming carbon neutral will also help the country adapt to the impacts of climate change, said Laura Lizano, energy director at Costa Rica's Ministry of Environment and Energy.
"We want geothermal to remain an important source for the country. Central America is very vulnerable to climate change and this source could be an important asset to deal with extreme weather," Lizano said.
With more than 100 hotspots, volcanoes, cinder cones and hot springs identified in Costa Rica, geothermal can play a critical role in reaching a sustainable clean energy mix, experts say.
But engineering consultant Paul Moya, who witnessed the kick-off of geothermal exploration in Costa Rica in the 1970s, said the country faces challenges to optimizing development of the power source.
Current law forbids the exploitation of geothermal power inside Costa Rica's national parks and protected areas, Moya said. The expansion of the Las Pailas project, a geothermal power station with a projected capacity of 55 megawatts (MW), is located adjacent to the Rincón de la Vieja National Park.
"It is a legal constraint. We know we have a lot of potential but our hands are tied because we are not allowed to do deep research in protected areas. There is no way to confirm the concrete geothermal potential because we cannot get into the parks," Moya said.
For decades, Costa Rica and Mexico have been the region's two geothermal leaders. Mexico's Ministry of Energy (SENER) points to studies that suggest there is a potential of 1 gigawatt of geothermal energy for every active volcano. Mexico has around 25 volcanoes.
The country ranks third among producers of geothermal electricity globally, with just over 1,017 MW of installed power capacity and 839 MW currently in operation. It built Latin America's first geothermal plant in the early 1970s.
Renewables account for 18 percent of Mexico's energy mix, according to SENER, but the government aims to produce 35 percent of its electricity from non-fossil fuel sources by 2024.
A law passed in 2014 allows private investors to enter the emerging energy market. This is likely to bring about an increase in the proportion of Mexico's power derived from geothermal energy, from 2 percent to more than 10 percent, said renewable energy expert Beatriz Olivera, who teaches at the National Autonomous University of Mexico.
But some environmentalists oppose business involvement in the exploitation of natural resources, Olivera noted, amid concerns over how geothermal licensing will sit with environmental protection and human rights, and the best way to democratize access to energy.
"The law was not widely discussed by society," she said. "It seems to have been an imposition from the top down."
"I am not sure if the Mexican government and the judiciary will be able to regulate, enforce and punish private companies' activities," she added.