“We speak for the rocks,” so says Dr Pri Utami, a renowned geologist, head of the Geothermal Research Centre at Gadjah Mada University (UGM) in Yogyakarta, Indonesia. She was answering a question about the Centre's partial funding by Geo Dipa Energy, an Indonesian state-owned enterprise. "They don't have the right to dictate our conclusions, we speak for the rocks", she said.

Geo Dipa operates many geothermal projects across Indonesia. This included a geothermal powerplant that started service in 2002, located in the Dieng Plateau - a highland region in Java marked by intense volcanic activity, with hot water deep below the surface.

How do these facilities work? The underground hot water is pumped through wells 1.5 to 2 km deep and converted to steam, which drives turbines to generate electricity. Afterwards, the steam is cooled in a condenser and turned back into liquid water, which is reinjected underground. Excess heat is dissipated in a cooling tower, releasing visible white plumes of water vapor into the air. Compared to highly polluting coal-burning plants, geothermal power stations emit much lower levels of greenhouse gases. They are an inexhaustible energy source, independent of the weather. By harnessing Earth’s natural heat, they represent a vital component of Indonesia’s strategy to transition away from coal, which still dominates the country’s electricity mix. 

The geothermal project has brought an unexpected positive impact to Dieng. During the cooling process mineral sediments, including silicate appear. Excessive silicate is unsuitable for soil, so it's considered as a waste, but researchers have found a creative way to use it. Dr. Ronny Martien, a nanobiotechnology expert at UGM, along with colleagues from UGM and Geo Dipa, developed a liquid booster to enhance soil fertility. It significantly reduces the dependence on chemical fertilizers and pesticides. The waste has been turned into a benefit!  The booster has been used since 2024 and it's much celebrated. A video skillfully mixing art, culture and geothermal science has been shot by Dr. Citra Aryandari from the Indonesian Institute of Arts in Yogyakarta. And there is more: in a 36-scond short clip produced by UGM, a local farmer expresses his gratitude to the university for the booster. Geo Dipa distributes it free of charge to the local farmers, "in order to smooth communication with the locals, tells Dr Ronny Martien. As we'll see later, the relationship between Geo Dipa and the community has sometimes been bumpy.

White plumes of water vapor released by cooling towers (Photo: Patrice Victor)

“In their imagination”

Mr. Bapak Surip, head of the Dieng Volcano Observatory Office, is also highly laudatory of the Dieng geothermal project. According to him, it has only positive impacts. He adds, however, that "a minority of people oppose the project; they think it has a negative impact, but it's in their imagination". Such a statement is surprising regarding such a large industrial project, and it's inconsistent with Geo Dipa’s own monitoring reports.

In its Environmental monitoring report published in September 2025 Geo Dipa acknowledges negative impacts generated from well testing activity, including potential exposure to hydrogen sulfide (H₂S). H₂S is a gas with a rotten egg odor which poses environmental risks. Drilling rigs may cause intermittent release of H₂S, but its emission can be natural too, coming from the volcanoes. For instance, in December 2024, H₂S and other toxic gases were reported in several craters in Dieng. So is it not always easy to trace the origin, from industrial activity or from volcanoes?

In 2023, during well testing related to Dieng 2, a new project under way, H₂S releases exceeded the occupational limit set by the World Health Organization (WHO). In the 4^th quarter of the same year, the concentration of PM10 air pollution – particles with a diameter of up to 10 microns – air pollution particles at some locations was over the WHO guidelines.

From the last measurements provided by Geo Dipa in 2025, the H₂S concentration is far below the official standard in residential area, well location, and ejector area. The report also recognizes that the development of Dieng 2 may cause negative effects and risks. For instance, it notes that nitrite, nitrate, ammonia, and phosphate levels in surface water failed to meet standards. For ground water the monitoring shows that in several locations, turbidity, iron, color and pH were exceeding the Indonesian quality standards.

Besides pollution, tragic incidents happen:

- In June 2016, an explosion occurred at a well pad in Pawuhan village due to the release of a gas safety cap. Six workers were burned and several crops were destroyed. Geo Dipa compensated 500 affected residents, but the compensation took a long time and wasn't much, according to the farmers.

- In March 2022, again in Pawuhan, a gas pipe leaked. One worker died because of H₂S poisoning. Eight were hospitalized. Many, including local residents, suffered injuries and nausea.

- More recently, on 22 February 2024, one more H₂S leak happened in another geothermal facility run by another company in Marapi District, Sumatra. More than 100 residents were poisoned.

Man-induced or natural phenomena?

Many residents underline a shortage of water during the dry season. It is a normal phenomenon in the region, but it seems to have been aggravated by the project’s massive water demands. Here again the data to confirm this assessment is either lacking or inaccessible. The question of "man-induced or natural?" arises not only for water scarcity and H₂S release, but also for moderate tremors which are common in Dieng. According to some residents, including Dafiq, a political science student from Dieng, small earthquakes often occur just after drilling and very close to the site. They could be induced by drilling, but here too, data is not available to confirm it, so the hypothesis cannot be ruled out. Furthermore, some opponents to geothermal energy cite the cancellation of a geothermal project in November 2017 in Pohang, South Korea, after it induced a devastating magnitude 5.5 earthquake. But this technology was different; it included fracking – the injection of high-pressure fluid – which can increase seismic risk. Fracking has not been performed in Dieng. Nevertheless, a document published on 4 October 2024 by Project Multatuli, an Indonesian online media, states that fracking has been used in Dieng, which is inaccurate, and the link provided doesn't mention it.

Cover of a press release by JATAM (mining advocacy network)  for the International Geothermal Convention in Jakarta in September 2025

Faced with seemingly worsening environmental conditions, residents remain deeply divided. Rizal, a biotechnology postgraduate student at UGM, maintains that, prior to the project, there was little soil, water, or air pollution. Here too data is lacking or inaccessible to verify this statement. According to Dafiq, "in order not to affect tourism, people lie when they claim they don't feel the impact of the project". Polarization has reached such a point that any geothermal activity is demonized. In a September 2025 press release, a major Indonesian environmental watchdog, JATAM (Mining Advocacy Network), stated:  "The exploitation of natural landscapes and water, the deterioration of air and water quality that poisons the human body, and the forced occupation of people's living spaces are just a few examples of the dirty nature of the geothermal mining industry". Surprisingly, its review of coal mining is much less aggressive, suggesting geothermal energy may serve as a scapegoat linked to the low level of consideration for the residents and the risks they incur.

Conversely, Geothermal Research Center experts interviewed by Prachatai unanimously minimize the inconveniences and hazards of the project and dismiss opponents:

"The local community has not much knowledge because they haven't been to the university. The toxic gases were there before the project",

"Inconvenience linked to the project is just in the mind of the people, it's easy to blame Geo Dipa. In this kind of project there are always complaints when the local population don’t get direct advantage, such as cheap electricity.",

"Some people would mention dryness as a negative impact, but do they really know the cause?"

Most residents may not have the scientific knowledge, but their experience of living near the geothermal facilities is easily dismissed. Geologists speak "for the rocks" and they are true to their feeling with such a statement. Yet the Geothermal Research Centre is at least in part funded by Geo Dipa, and this kind of situation often creates a well-documented unconscious bias. Disregarding critical voices against Geo Dipa amounts to some extent to shielding it from opposition.

Prachatai talked to random people on the street in Pawuhan village. Two ladies in their forties: "We have some trouble breathing which started 2 years ago". What's the cause? "It's probably because of the volcanoes".

Another passer-by in his thirties, Mr Yandri (pseudonym), who did not want his real name published because people are divided, said "Since 2022 I feel sometimes headache, and shortness of breath. Nevertheless since 2024 the main problem is water [just after the extension of the project to Dieng 2]".

Industrial facilities near residential areas pose significant hazards. From a safety perspective, drilling locations and injection wells are dangerously close to homes and water sources, but suitable remote sites are scarce in highly populated Java. Nevertheless, the Geothermal Law No. 21/2014, adopted in 2014, removed many prior constraints on geothermal activities. They are no longer considered mining activities and can now occur near conservation forests. This shift has sometimes left local communities feeling their rights are disregarded, to the point that in 2023, the World Bank withdrew funding from the Wae Sano geothermal project on Flores Island after residents protested because of its proximity to homes, and environmental and social disruptions. Eventually the project came to a stop.   

The People's Library

A mural inside the People’s library (Photo: Patrice Victor)

Against this backdrop, dissatisfaction among some residents in Dieng was predictable. In 2018 (it was the end of the drilling phase of Dieng 1, the first project), a dozen youths - including Dafiq and Rizal – launched the People's Library in Bakal village to boost literacy and environmental awareness, especially among farmers and school students who often neglect these issues. In the following years the group  produced a documentary, a magazine and a book, organized a series of demonstrations and even staged a protest to halt operations, blocking the company's heavy equipment from entering the project area. Alfarhat, head of JATAM's Campaign Division, notes: "Depending on the situation, in Indonesia peacefully voicing demands often falls on deaf ears". Tensions escalated as plainclothes police and military visited the library to intimidate, warning the activists against "disseminating communist propaganda"— a reference to Indonesia's ban on communist materials. Another time, soldiers asked for money in exchange for their "protection" at a library festival. Tension peaked in 2023 before subsiding. The library currently faces no further threats or blackmail.

Criticism, distrust, demonstration… why such a clash surrounding Dieng's supposedly green geothermal project? Dr Pri Utami explains: "The lack of baseline environmental data and the absence of a clear land use policy as a foundation for the development of the Dieng region have resulted in all accusations being directed toward the existence of the geothermal project". When the project began, Geo Dipa deployed technicians, trucks and equipment to the plateau with minimal engagement, if any, with the local population, thus a gap has grown between the enterprise and the farmers. Eventually UGM and Geo Dipa improved communication, including by organizing meetings with the residents. Some of them have been involved as contractors or unskilled workers. Today Geo Dipa recognizes a lack of information on land acquisition for Dieng 1, the initial project, and possible downsides for the communities during Dieng 2 construction – and it also recognizes somewhat belatedly, the need for more frequent and detailed environmental and social risk assessments.

Geothermal energy offers national level benefits and aligns with global efforts to cut greenhouse gas emissions, whereas hazardous effects remain localized near facilities. Local communities are often overlooked as key stakeholders, with little consideration for their well-being. Industrial safety is  not a priority in Indonesia and people who may be exposed to potential injury and damage face a lack of transparency and have not much influence in the decision making process. Hence a feeling of injustice.