overview of global existence of pollutant and ghg ... · list the abatement of pollutant or ghg was...

Proceedings World Geothermal Congress 2020

Reykjavik, Iceland, April 26 – May 2, 2020

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Overview of Global Existence of Pollutant and GHG Abatement Facilities in GPPs

Alessandro LENZI1, Marco PACI1, Lilja TRYGGVADOTTIR2, Teitur GUNNARSSON2, Katrin

RAGNARSDOTTIR2

1Enel, 2Mannvit

Urdarhvarf 6, 203 Kopavogur, Iceland

[email protected] , [email protected]

Keywords: Geothermal, Abatement, GHG, Environment, Overview

ABSTRACT

In a project commissioned by Enel Green Power (EGP), Mannvit and EGP conducted a worldwide mapping where information for

geothermal power plants (GPPs), was gathered and inserted into a database for all geothermal fields with installed capacity over

200 MW. The list of GPPs was then extended to fields with installed capacity less than 200 MW, by including some plants that

showed to be of particular interest due to installed abatement systems, the history of installed abatement systems or the type of

fluid. The resulting list of geothermal areas comprises 30 geothermal areas with approximately 125 GPPs (over 265 units). The

gathered available information consisted mainly of basic plant description, year of construction, owner, installed capacity and

information on a few parameters of environmental interest. Despite the conscious addition of plants with abatement systems to the

list the abatement of pollutant or GHG was noted in only 63 GPPs within 13 geothermal areas of the investigated 125 GPPs in 30

geothermal areas.

Italy had most GPPs with operating treatment facilities. This is not surprising since Italy has strict regulations for emission limits

and air quality and H2S/Hg abatement systems have been installed in all Italian GPPs. Of the total 63 GPPs with treatment facilities,

35 of them are in Italy, 19 are in the USA, and further 15 of those 19 are in the Geyser geothermal area. Nevada and California in

the USA have strict ambient air quality standards and most of the GPPs there have H2S abatement systems. The Philippines has no

operating treatment facilities even though some abatement systems have been tested or implemented there, they were however

deemed unnecessary and therefore shut down.

The scarcity of treatment facilities in operation in connection to environmental enhancement of the plants is intriguing. To

investigate the reason why, the incentive for implementation of abatement systems was studied.

Regulations for air emissions and wastewater do not require treatment from most of the GPPs in the countries studied. The

countries studied represent the largest geothermal producers and countries with longest history of geothermal energy utilization

such as USA, Mexico, Philippines, Iceland, Indonesia, Italy, Kenya, New Zealand, Turkey and Japan.

1. INTRODUCTION

As defined by EGP the Best Environmental Performance Project aims to identify the leading energy production from geothermal

resources with regards to environmental performance. For this purpose, a worldwide mapping was conducted constricted with a few

parameters but extended as necessary to include interesting abatement processes.

The main focus of the study was on power plants chosen with respect to a few parameters:

Geothermal fields with installed capacity over 200 MW

Open cycle (dry steam, single or multiple flash), binary cycle or a combination

Gross electric power of the geothermal plants > 5 MW

In operation for at least 1 year

Treatment plants/operation practices adopted to avoid/reduce pollutant or greenhouse gases (GHGs) releases in

atmosphere (where total reinjection is not possible)

Information was gathered and listed for all the geothermal fields with installed capacity over 200 MW. The list of plants was then

further extended by including some plants that showed to be of particular interest due to installed treatment facilities, the history of

installed treatment facilities or the type of fluid. This resulted in the global overview as presented in section 2 and used as basis for

the discussion and conclusions of this article. To study the reasons for detected scarcity of abatement systems two factors were

investigated namely the technology used and regulatory environment in the main countries. The technology matrix and regulatory

review can be found in sections 3 and 4.

2. GLOBAL OVERVIEW

After applying the gathering methodology, as described in the introduction, the resulting list of geothermal areas comprises 30

geothermal areas with approximately 125 GPPs (over 265 units). The gathered available information consisted mainly of basic

plant description, year of construction, owner, installed capacity and information on a few parameters of environmental interest.

Despite the conscious addition of GPPs with abatement systems to the list, abatement of pollutant or GHG was noted in only 63

GPPs within 13 geothermal areas of the investigated 125 GPPs in 30 geothermal areas.

mailto:[email protected]

mailto:[email protected]

Lenzi, Paci, Tryggvadottir, Gunnarsson and Ragnarsdottir

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Figure 1: Overview of the studied geothermal fields and GPPs with abatement systems by country.

The figure above provides an overview of the geothermal fields studied and the GPPs in the studied areas that have abatement

systems of some sort, i.e. regarding air emission or wastewater. The geothermal fields studied are spread around the world and are

marked with a yellow dot in Figure 1. The number of GPPs with abatement systems are marked with a gray triangle, by country.

Italy had most GPPs with operating treatment facilities. This is not surprising since Italy has strict regulations for emission limits

and air quality and H2S/Hg abatement systems have been installed in all Italian GPPs. Of the total 63 power plants with treatment

facilities, 35 of them are in Italy, 19 are in the USA, and further 15 of those 19 are in the Geyser geothermal area. Nevada and

California in the USA have strict ambient air quality standards and most of the GPPs there have H2S abatement systems. The

different types of operational treatment systems within GPPs noted in the overview are AMIS, Stretford, LO-CAT, burn and scrub,

Selectox, Claus, BIOX, boron removal, arsenic removal, biofilter, NCG reinjection, Carbfix and Sulfix. The technology matrix is

better described in next section.

For most of the GPPs studied, verification of whether abatement system is present or not could be completed with available

literature or from power plant layout. For Cerro Prieto, Mexico there was no mention of abatement system in the available literature

and since there is no ambient air quality standard in Mexico we assumed that no treatment is present. Ambient air quality is

however monitored in nearby towns. For the following GPPs; Kizildere II, Turkey and Olkaria III, Olkaria IV and Wellhead Units,

Kenya no gaseous pollutant abatement systems were mentioned in available literature nor shown on power plant layouts. Food

grade CO2 is produced from the geothermal gas from Kizildere II and Dora I in an industrial plant in Kizildere and CO2 are

sometimes piped to a farm to boost flower production in Olkaria III. Since the abatement in Turkey is not conducted at the power

plants and no data was available for the amount piped in Kenya, it was not included for this study. The geothermal power plant in

Kizildere II has a wastewater treatment, boron removal, but since geothermal fluid is fully reinjected this is not considered an

abatement technology. It is therefore concluded that there are no abatement systems present at these power plants.

In total the countries, in which the geothermal fields identified and displayed in the figure above, have a total installed capacity of

13.480 MW which is 93% of total capacity worldwide (14.369 MW) (Richter, 2018). The resulting list of geothermal areas hence

covered around 67% of the total worldwide installed capacity, thereof approximately 37% have some sort of abatement system

installed. The following graph shows the capacity included in the list of geothermal areas by country and the coverage of total

installed capacity in each country.

Country 69% 66% 96% 60% 87% 78% 25% 36% 58%

Coverage

Figure 2: Total worldwide capacity by countries.

Lenzi, Paci, Tryggvadottir, Gunnarsson and Ragnarsdottir.

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Overall, geothermal technologies are considered low emission technologies as the only direct emissions come from the fluids in the

reservoir being harnessed which are small in relation to traditional base load thermal energy power production facilities. The

amount of direct NCG emissions is related to the composition of the geothermal fluid and technology used. Generally, total GHG

emissions from GPPs is less than emissions from fossil fueled power plants such as coal, as no combustion is involved. The NCG

from GPPs normally contains only two GHGs, CO2 and CH4, and since CO2 is more abundant most abatement technologies focus

on that.

Figure 3: Comparison of CO2 emissions from geothermal and fossil fuel power plants (Fridriksson, et al., 2016).

In Figure 3 CO2 emission from fossil fuel power are compared to GPPs, globally and in certain locations. This shows that

geothermal typically has far lower emission than oil, natural gas and coal, even though in some extreme cases such as in Turkey

emissions can be as high as 900-1.300 gCO2/kWh. (Fridriksson, et al., 2016)

3. TECHNOLOGY MATRIX

Even though different technology options in use in GPPs, such as working cycle and cold end option, can reduce emissions, in most

cases some NCGs are released. The primary pollution concern for geothermal power operations has been the emission of hydrogen

sulfide (H2S). In a few plants elemental mercury (Hg) has also been detected and is regulated as the mercury would be emitted with

the NCG if not abated. The used geothermal fluid is reinjected in most GPPs and thus wastewater treatment is not necessary.

Wastewater treatment can however be required where reinjection of the geothermal fluid is not applied. The main wastewater

pollutants from geothermal operations are boron (B) and arsenic (As).

As H2S is the pollutant of most concern in emission from GPPs, it is not surprising that plenty of available abatement technologies

exist. According to Gary J. Nagl (1999) the most widely used H2S abatement system is the liquid redox system, LO-CAT II. It has

even been considered the best available control technology for GPPs by some. It is important to consider both the need for an

abatement system and the best technology based on geothermal fluid, energy conversion technology, local regulations and potential

waste handling. According to a thesis written by Esteban José Rodríguez Pineda (2013) the key variables when selecting an

appropriate H2S system for a geothermal power plant are the economics of the process, the ratio of ammonia-to-hydrogen sulfide in

the geothermal brine and the condenser design.

The following table lists examples of the most practiced and effective H2S abatement processes available in geothermal

applications and the conditions they apply to. It shows that it is important to choose appropriate abatement method for different

geothermal plants and steam composition.

Table 1: H2S abatement processes with preliminary selection criteria, edited excerpt of Table 6 p.49 in a thesis written by

Esteban José Rodríguez Pineda (2013).

Process Condenser

design

Economics Best suitable for1 Comments

Liquid phase

oxidation methods

Surface High capital cost Large plants Applied in some Geyser units and in

Coso geothermal field.

AMIS®

technology

Direct contact Unknown Currently applied in

GPPs in Italy

Process tailored for Italian field

characteristics

1 Best suitable for is strictly connected to the economics i.e. high capital cost is suitable for large plants etc.


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Process Condenser

design

Economics Best suitable for1 Comments

NCG reinjection Surface Low capital and

operational costs Small and large plants Currently only practiced partially in

Hellisheiði. Requires process to be

pumped or gases compressed into the

spent fluid.

Selectox Direct contact High capital cost and

low operational costs Medium to large plants Used in Yanaizu-Nishiyama, a 65 MW

plant in Japan.

Burner/ scrubber Surface and

direct contact

High NH3 content: High capital and low

operational costs

Low NH3 content: Low capital and high

operational costs

High NH3: Small units

Low NH3: Large units

A variation of this process is used in Hachijo-Jima, Svartsengi, Yanaizu-

Nishiyama and the Geyser units using

Dow Rt-2. Direct condenser is preferred.

Dow RT-2 Direct contact High capital cost Large units Applied in some Geyser units.

BIOX Surface and

direct contact

Low capital and

operating cost

Small and large units Used in John L. Featherstone, Salton Sea. Lower efficiency with direct

contact condenser.

Caustic scrubbing Surface and

direct contact

Low capital and high

operating cost

Small units Used in Cobb Creek, Geysers, where

NCG content is low.

As we can see from Table 1 the technology options, such as condenser type, can matter when choosing the suitable H2S abatement

system. The available processes for H2S abatement can be categorized into the following subcategories; liquid phase oxidation,

AMIS, burn and scrub, absorption and Claus and related processes. Scavenger technology also exists but it is not included here as

there is no example of the technology in current geothermal application. The abatement processes for pollutants in NCG and

condensate currently operating in the 63 GPPs within 13 geothermal areas were gathered and reviewed in Table 2 below.

Table 2: Summary of pollutant abatement processes in use in operating geothermal power plants as reviewed in this article.

Process Pollutant

abated

Efficiency Installed

capacity

[MW]2

Comment

Stretford H2S Generally >99%

(up to 99,99% in the

Geyser)

648 Liquid phase oxidation. If mercury is present in the NCG it

will be collected in the Stretford solution. Therefore, it is

often used with upstream mercury beds.

Has proven very successful at the Geysers, with minimum

downtime and little problems. (Pineda, 2013)

LO-CAT/LO-

CAT II

H2S Up to 99,99% 180 Liquid phase oxidation. A buffer is used to control the pH.

SulFerox H2S Up to 99,99% 90 Liquid phase oxidation. In BLM units in Coso

BIOX H2S 95% in NCG

98% in condensate

50 Liquid phase oxidation. Treats both NCG and condensate

used as cooling tower make up water

DOW RT-2 H2S 94% average at Geyser

power plants 242 Combines burn and scrub process with a H2S iron chelate

process to form thiosulfate before reinjection.

AMIS®

technology

H2S and

Hg

90-99% of H2S and

80-98% of Hg

944 Process tailored for Italian field characteristics. Currently

applied in plants owned by EGP.

Selectox H2S >90% in Yanaizu-

Nishiyama

65 The process is based on replacing the Claus first stage

thermal reactor (the furnace) with a catalytic oxidation step.

Sulfix/Carbfix H2S and

CO2 90-99% of H2S

~50% of CO2

303 Absorption in water which is then reinjected. This process has

only been implemented and tested in Hellisheiði, 50% of total

gas treated. The efficiency and replicability of the process depends on gas content, water availability and a proper

composition of the reinjection reservoir able to mineralize the

reinjected gas.

2 Total installed capacity of geothermal power plants studied with operating abatement process.


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Process Pollutant

abated

Efficiency Installed

capacity

[MW]2

Comment

Bioreactor H2S 95% in condensate in

Wairakei

187,5 Absorption process that uses sulfur loving bacteria to oxidize

dissolved H2S to elemental sulfur.

A tubular biofilm reactor used for wastewater in Wairakei,

New Zealand and bioreactor for gaseous abatement in Otake,

Japan.

Caustic scrubbing H2S Can be very high. Variable depending on

amount of reactant

used and gas content.

110 Absorption process that uses caustic soda to react with the

H2S and form sodium bisulfide

Due to reduction in NCG the burner/scrubber was shut down

in Cobb Creek and replaced with caustic scrubbing and iron

chelate in the condensate.

Combustion and

desulfurization

with Mg(OH)2

H2S 90% 3,3 Special variation of burn and scrub method. Operated in

Hachijo-Jima.

SMC (Haldor

Topsoe) H2S >99% 75 Catalytic oxidation and scrubbing, a type of burn and scrub

technology. Pilot plant in Svartsengi, Iceland, 10% of total

gas treated. Applicable for H2S concentrations <2%.

Mercury filter Hg Typically, ~90% 5103 Usually to avoid contamination in sulfur byproduct, mercury

filters containing activated carbon have been installed up- or

downstream of the abatement system.

KEPCO arsenic

removal

As High 110 KEPCO developed an arsenic removal process for the

Hatchobaru Power Plant to use the wastewater for irrigation.

The arsenic abatement mentioned in the table was conducted in Hatchobaru where FeAsO4 precipitate was produced and sandfilters

used to separate the precipitate. This wastewater used to be reinjected completely but an interest for using it for irrigation called for

abatement of arsenic. No information was located for the efficiency of this process. The ion exchange resins utilized for boron

removal from wastewater in Kizildere, Turkey, is excluded from the table since the geothermal fluid is fully reinjected thus it is not

considered an abatement. The efficiency of this process is not available but for similar equipment type Diaion CRB02 the reported

efficiency is 98%. As the mercury filters are often for the sole purpose of providing a cleaner sulfur byproduct it is often not

mentioned in the context of NCG abatement systems and thus other power plants studied might also have it.

GHG abatement within GPPs have recently been in the spotlight and increasing environmental awareness calls for actions to reduce

GHG emissions from GPPs, even though not considered a pollutant. Geothermal GHG treatment systems, in the rare case they are

present, usually focus on CO2, especially in places such as Turkey where CO2 emissions are great. Usually removal of H2S is

required first as it is detrimental for most CO2 applications. Geothermal power plants have been inspired by other fields (e.g.

natural gas) to explore different methods for GHG abatement and processes to turn CO2 to value. In Table 3 the technologies

currently in use in GPPs for carbon capture and utilization are summarized. Similar technologies for agriculture, beverage and food

have been tested in various locations such as in Italy. New processes and innovative technologies are also being developed and

tested such as a pilot process for lithium carbonate production in Salton Sea and algae production in Iceland and Italy (Bassi, et al.,

2018).

Table 3: Technologies currently in use in geothermal power plants for GHG abatement

Geothermal power

plant

Recovery option Abating Operation status

Svartsengi, Iceland NCG from GPP sold for methanol production using amine absorption

for H2S removal (CRI)

CO2 Operational demonstration

plant

Svartsengi, Iceland CO2 rich NCG provided to the Blue Lagoon to e.g. feed algae

(Resource Park, 2019) CO2 Operational

Kizildere and Dora,

Turkey

NCG from GPP sold for production of food grade CO2 CO2 Operational

Olkaria III, Kenya NCG are sometimes piped to a farm to boost flower production CO2 Occasionally

3 At least in Coso, NCPA and Aidlin.


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Binary power plants are increasingly being used to harness geothermal energy, especially in low enthalpy fields. If the gas content

is not too high and the pressure is kept high enough so that the gases never separate from the fluid, these cycles can have near zero

emission. Even though the NCGs are reinjected and not released to the atmosphere, this is not considered an abatement in this study

as the NCGs are never separated from the fluid. Furthermore, the risk remains that the gases are released from the ground in a faster

manner than before, due to being separated from the fluid. This aspect however still needs more research to be proven.

A combined cycle with a backpressure unit and a bottoming binary unit, where the NCGs are extracted from the steam condenser

and compressed back into the condensate stream on its way to the injection wells as installed in Puna, Hawaii is considered as

abatement. This methodology ensures that the gases released from the fluid are reinjected into the ground with the geothermal fluid

ensuring near zero emissions. There are still not many examples of abatement of NCGs by reinjection globally, but it is practiced or

has been practiced in Puna, Coso, Ogachi, Hijiori, Tongonan and Hellisheiði (the only one currently operating). Due to the recent

discussion regarding the urgency to minimize GHGs, techniques like SulFix and CarbFix, as applied in Hellisheiði, might through a

recent research grant increase examples of GHG injection, if successful in its application at other locations.

4. REGULATORY OVERVIEW

Independent of location or country environmental policies and regulations regarding air emissions and emission levels in

wastewater set the bar for whether treatment of exhaust streams is installed in GPPs or not. The treatment is always an added cost

and therefore in general not embarked on unless made necessary by law, regulation, pressure from the public or if it can in some

other way be economical.

The World Health Organization (WHO) is the directing and coordinating authority on international health within the United

Nations’ system. WHO Regional office in Europe published the first Air quality guidelines for Europe in 1987, recognizing the

need of humans for clean air. The aim of the guidelines is to provide a basis for protecting public health from adverse effects of air

pollutants and to eliminate or reduce exposure to pollutants known or likely to be hazardous to human health or wellbeing. The

WHO air quality guidelines are also intended to provide background information and guidance to governments that are setting

standards. Therefore, the national standards are sometimes higher and sometimes lower than the WHO guidelines. The guidelines

for H2S and Hg from the Air quality guidelines for Europe, 2nd edition is provided in the following table. As the global air quality

guidelines have not been updated for other pollutants than particulate matter (PM), ozone (O3), nitrogen dioxide (NO2) and sulfur

dioxide (SO2), the WHO Air quality guidelines for Europe remain in effect (World Health Organization. Occupational and

Environmental Health Team, 2006) .

Table 4: Guideline values for individual substances, extracted from table in (World Health Organization. Regional Office

for Europe, 2000)

Substance Time-weighted average Averaging time

Hydrogen sulfide 150 µg/m3 24 hours

Mercury 1 µg/m3 Annual

For Arsenic, a guideline value is not set by WHO, but it is underlined that it is a human carcinogen and that an air concentration of

1 µg/m3, an estimate of lifetime risk is 1,5*10-3. The WHO guideline also recognizes that “in order to avoid substantial complaints

about odor annoyance among the exposed population, H2S concentrations should not be allowed to exceed 7 µg/m3, with a 30-

minute averaging period”. (World Health Organization. Regional Office for Europe, 2000)

The European Union (EU) has developed an extensive body of legislation which establishes standards and objectives for a number

of pollutants in air. The EU's air quality directives (2008/50/EC Directive on Ambient Air Quality and Cleaner Air for Europe

and 2004/107/EC Directive on heavy metals and polycyclic aromatic hydrocarbons in ambient air) set pollutant concentrations

thresholds that shall not be exceeded in a given period of time. In case of exceedances, authorities must develop and implement air

quality management plans. These plans should aim to bring concentrations of air pollutants to levels below the limit and target

values.

Selected EU standards and the World Health Organization (WHO) guidelines are summarized in the table shown in Figure 4. The

WHO guideline values are generally stricter than the comparable politically agreed EU standards.

While the main geothermal fields studied in this article are spread around the world, they all follow the same international climate

change treaties as all of the countries have signed, accepted or ratified both the United Nations Framework Convention on Climate

Change (UNFCCC) and the Paris Agreement (United Nations Framework Convention on Climate Change, 2018). Thus, most of the

countries studied have some reported GHG emissions from GPPs and some countries also report GHG emissions from the

geothermal sector separately from other energy sources. The countries that report geothermal emissions as part of their national

inventory report are USA, Iceland, New Zealand and Japan. These are the UNFCCC, Annex 1 countries, with the exception of Italy

and Turkey. According to the UNFCCC all Annex 1 parties shall report their national inventory following to the IPPC guidelines

but as there are no formal guidelines regarding reporting emissions from geothermal fields, the reporting can thus be different

between parties. That is because it is still debated whether GHG emissions from geothermal power stations should be considered as

anthropogenic or as natural emissions. The general opinion has been that geothermal energy is a renewable energy resource with

less emission than other alternative (fossil) energy sources and emphasis on regulating and measuring the GHGs has therefore been

low. The awareness of this is changing and in the future further information could be available.


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Figure 4: EU Air Quality Directive compared to WHO Guidelines. (World Health Organisation (WHO), 2016)

Following are the regulatory requirements for GPPs in the countries studied. Also included is the national ambient air quality

standard that applies in these countries of interest. In most countries some water pollution regulations also exist for Hg, As etc.,

however, as most GPPs currently reinject the geothermal fluid, this was not summarized in the same way as for the air emission.

Table 5: Overview of regulatory requirements for geothermal power plants. (Information for Italy to be inserted)

Country USA Mexico Philippines Iceland Indonesia Italy

**

Kenya New

Zealand

Turkey Japan

Geothermal (air) emission limits

H2S None

*

None 150-200 g/GMW-Hr

(grams/hour

per gross

megawatt)

None 35

mg/Nm3

10 kg/h (a)

20 kg/h (b)

30 kg/h (c)

80 kg/h (d)

100 kg/h (e)

3 kg/h (f)

None None

None None

Hg None None 5 mg/Nm3 None None 4 g/h (a)

8 g/h (b)

10 g/h (c)

15 g/h (d)

20 g/h (e)

2 g/h (f)

None None None None

NH3 None None 10 mg/Nm3 None 0,5

mg/Nm3

None None None None None

As None None 10 mg/Nm3 None None None None None None None

Cooling

tower

drift

0,002% (In

California)

None None None None None None None None None

CO2 None None None None None None None None None None

CH4 None None None None None None None None None None

National ambient air quality standard

H2S 1hr: 0,03

ppm 42 µg/m3 (In

California)

1hr: 112

µg/m3 (In

Nevada)

None 30min: 0,13

ppm (200

µg/Nm3)

24hr:

50

µg/m3

1 year:

5 µg/m3

0,02ppm 150 μg/m3 (g)

100 μg/m3 (h)

20 μg/m3 (i)

24 hr:

150

µg/m3

1hr: 7

µg/m3

Short-term

limit: 100

µg/m3

Long-term

limit: 20

µg/m3

0,02-

0,2

ppm

Hg None None None None None 0,2 μg/m3 (l) None 1 year: Inorganic

0,33 µg/m3

Organic

0,13 µg/m3

None None

NH3 None None 30min: 0,28 ppm (200

µg/Nm3)

None 2 ppm 170 µg /m3 (m)

70 µg /m3 (n)

None None None 1-5

ppm


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Country USA Mexico Philippines Iceland Indonesia Italy

**

Kenya New

Zealand

Turkey Japan

As None None None 1 year:

6 ng/m3

None 6 ng/m3 (o) None 1 year:

inorganic 0,0055

µg/m3

None None

Cooling

tower

drift

0,002% None None None None None None None None None

CO2 None None None None None None 8 hr: 5

mg/m3

1 hr: 10

mg/m3

None None None

CH4 None None None None None None None None None None

* Some counties have specific emission limits for geothermal emission, e.g. in Lake County the H2S emission is restricted further to <50 g/MWh and

the content of sweet gas shall not exceed 10 ppmv and the Great Basin Unified Air Pollution Control District sets discharge limits of 100 g/MWh for

H2S.

**Other pollutants like Boron, Antimony and Radon have reference values, limits on emission and guidelines for air quality in in table 4.1 of

Tuscany law DGR 344/2010. (a) <=20 MW plants with natural draft cooling tower, (b) >20 MW plants with natural draft cooling tower, (c) <=20 MW plants with forced draft

cooling tower, (d) 20-60 MW plants with forced draft cooling tower, (e) >60 MW plants with forced draft cooling tower, (f) AMIS outlet, (g) 24h

average, (h) 14 day average, (i) 90 day average, (l) annual average, (m) 24h average, (n) 14 day average, (o) annual average

In Table 5 an overview of the air quality standards and regulated emission level shows the large task at hand within regulation of

emission from GPPs. No regulations for GHG emissions or ambient air quality have been implemented, except in Kenya where an

ambient air quality tolerance for CO/CO2 has been set. Geothermal emission limits of the countries studied are found in Philippines

(H2S, Hg, NH3 & As) Indonesia (H2S & NH3) and California (cooling tower drift). Additionally, a discharge consent was found for

Kawerau geothermal system in New Zealand and a specific restriction for H2S and sweet gas for Lake County, US. For the

countries studied some kind of national ambient air quality standard was found relevant to geothermal industry, except for Mexico.

These countries include ambient air quality standard for H2S and some have for other air pollutants that can be found in geothermal

emissions as well. The incentive for the guidelines or limits can vary between countries, e.g. in New Zealand the guideline for H2S

is quite low since it is because of odor nuisance, whereas in e.g. Iceland the regulation of H2S in air is meant to protect public

health. The strictest regulations for H2S ambient air quality standard are in New Zealand, but it is especially noted in their

regulation that the guideline is based on odor nuisance and may be unsuitable for geothermal areas due to their remoteness.

Despite the greatest incentive for implementation of abatement system may be to avoid incompliance with pollution regulation,

there are not many countries that have stipulated shut-down or fines in case of incompliance. In California the regulations are very

strict and if they are not met, a Notice of Violation will be issued including a fine. In Puna GPP there are also examples of fines due

to violation of H2S emission and suspension of permit due to well blowout (United States Environmental Protection Agency, 2018).

Even though actions in case of incompliance are not always defined, as e.g. in Iceland, then reports of incompliance raise awareness

in the community. Pressure from politicians and the Kyoto protocol and odor complaints from the community has led to

investigation, development and application of abatement systems in Icelandic GPPs. In Turkey there is recently increased pressure

from the investors, international funds and banks, to investigate and abate pollution, mainly CO2, from GPPs.

Normally abatement systems are expensive and if sanctions due to incompliance with pollution regulations cost the operator less

than abatement systems advised there is no incentive to install them. However, abatement of emissions from GPPs could be carried

economically if it benefits the operation of the power plant or if it involves an added income stream. For instance, treatment options

are considered if the chemical affects the reinjection quality of the fluid, i.e. in case of scaling in reinjection wells that are necessary

for the replenishing of the resource. Furthermore, the carbon sales or emission trading systems, such as the Clean Development

Mechanism (CDM) under the Kyoto protocol and the European Union’s Emissions Trading System (ETS), are creating an

interesting scenario for the future. Geothermal projects have been funded via the CDM, such as The Olkaria II Geothermal

Expansion Project in Kenya, even though no treatment facilities are in place there (Huidobro, 2013). It will be of interest to see if

these schemes will set an incentive to install more treatment facilities in GPPs globally. The following figure shows the price

development of CO2 in the ETS from 2013-2018. (Markets Insider, 2018)

Figure 5: Price development of ETS (Markets Insider, 2018).


9

As can be seen in Figure 5 the price of CO2 European emission allowances is rising steeply. The background is speculated to be that

hedge funds have started to show interest in the European Union’s Emissions Trading System (ETS) trading in light of the

2020/2030 goals and thus less amount of ETS quota is on the horizon. There are also reforms coming into effect to curb oversupply

in the system such as a Market Stability Reserve (MSR) which comes into effect in 2019. (Twidale, 2018) The cost of CO2

emission quota has been in the range of 5-8 EUR/t for the last 5 years. The price is currently just above 20 EUR/t, still considerably

lower than CCS cost from recent studies. (Markets Insider, 2018) If the price continues to increase the interest in CCS will pick up

and more companies might consider their possibilities in reinjection or CO2 utilization options, the same can be said for GPPs, if

they can participate in the ETS.

5. DISCUSSION

Of the total 63 GPPs with abatement systems, 35 are in Italy, 19 of them are in the USA and further 15 in the Geyser geothermal

area. This is not very surprising since most of them are H2S abatement systems and Nevada and California in the USA and Italy

have strict ambient air quality standards for H2S. The current ambient air quality standard for H2S in California, USA was adopted

in 1969 and the California Department of Public Health reviewed the scientific literature in 1981 and concluded that the existing

standard was adequate (California Air Resource Board). Furthermore, strict emission limits have been set in Lake County and the

Great Basin Unified Air Pollution Control District, leading to implementation of abatement systems in most GPPs in California.

Italy had most GPPs with operating treatment facilities and furthermore H2S/Hg abatement systems have been installed in all Italian

GPPs. Abatement systems in the studied geothermal facilities are also present in Iceland, Japan and New Zealand. Hence, no

abatement systems were present in the facilities listed in Mexico, Philippines, Indonesia, Kenya and Turkey.

As every geothermal field is different factors such as enthalpy, gas content, gas composition, market, regulations, physical

environment and public opinion all need to be weighed in when choosing appropriate technology. The flexibility of the chosen

technology can also matter due to possible reservoir changes during operation of the power plant. Even though different technology

options in use in GPPs, such as working cycle and cold end option, can reduce emissions, in most cases some NCGs are released. In

closed binary systems, near zero emission may be reached if pressure is kept high enough. In open work cycles other factor such as

the cold end option weigh into how effectively the gas can be extracted and handled. In open cold ends, direct contact condensers,

part of the NCG is dissolved in the cooling water, leading to stripping in the cooling tower if not treated. In closed cold end systems

such as wet cooled surface condenser, dry and hybrid cooling, generally less gas will partition in the condensate. Most GPPs are

equipped with a shell and tube surface condenser and most of the plants that utilize NCG treatment have closed cold end, i.e.

surface or air-cooled condensers.

As the NCG content and composition is highly site specific and the local environment, such as the market, regulation and the

community, affect the suitable technologies at that location. The Stretford, LO-CAT and DOW RT-2 have been implemented in

various GPPs. These technologies were however not suitable e.g. in Hellisheidi and the most fitting option there was to develop a

new abatement technology. The new abatement technologies are often somewhat based on technologies used in other industries.

These new processes are often somewhat based on technologies from other industries and examples of recently developed

processes are CarbFix/SulFix in Hellisheidi, SMC™ process in Svartsengi and the bioreactor in Wairakei. The replicability of the

abatement and reinjection system in Hellisheidi is currently being tested in four different locations in Europe. Currently all the

GPPs in Italy are equipped with AMIS technology.

Currently very few GHG abatement measures are being taken in geothermal energy. The scarcity of GHG emission reduction

systems in GPPs is not very surprising since there is not a great incentive for treating GHG. Also, the fact that geothermal emission

in general is considered a cleaner and more sustainable alternative to e.g. fossil fuels. The importance of GHG abatement is

growing in the geothermal field, especially in cases such as Turkey, where carbonate rocks in the reservoir cause great GHG

emission when the geothermal power is generated. In some geothermal areas in Turkey the emission is greater than in many fossil

fuel operations as was shown in chapter 2. What is more interesting about the available recovery options shown in chapter 3 is that

in over half the cases the NCG is sold to a buyer, more or less untreated, which turns the CO2 to value. Ideas such as in Svartsengi,

where the objective of the plant and the surrounding companies of the Resource Park is to foster a “Society without waste” and

ensuring that all resource streams that flow to and from the companies in the Park are utilised to the fullest extent possible, are

increasingly becoming more popular. (2019) Hellisheiði, Iceland is currently the only GPP that practices partial reinjection of GHG

but researches for replication are currently being carried out. If they are successful hopefully the technique could be used in more

places, minimizing the GHG emission of GPPs. The possibilities for GHG recovery and reinjection are many but the problem is to

find a way that is economical and returns profit as the available technologies for GHG emission treatment are expensive.

The scarcity of treatment facilities in operation in connection to environmental enhancement of the plants is intriguing. It would be

prudent to presume that naturally occurring low NCG would incline operators to put little effort into abatement systems. This

however did not seem to be the deciding factor as for example Salton Sea, USA, which has the lowest NCG reported of the

geothermal areas studied in this article of 0,017-0,02%, has one operating abatement system and even more that are currently not

operating. There are strict air quality regulations in California, USA, which can explain this, but it still comes as a surprise as it was

considered probable that standards were fulfilled without abatement systems. Hellisheidi, Iceland, also has a low NCG content,

approximately 0,5%, and an installed abatement system. CarbFix and SulFix was developed to abate the gases for many different

reasons, one of them being that the public in towns situated close by complained of odor and negative consequences of the H2S.

Furthermore, the development of a new process was built on e.g. the reasoning that there was no market for sulfur cakes in Iceland

and yet another important factor was political interest in fulfilling the Kyoto protocol by reducing CO2 emissions.

The countries studied represent the largest geothermal producers and countries with longest history of geothermal energy

utilization; USA, Mexico, Philippines, Iceland, Italy, Indonesia, Kenya, New Zealand, Turkey and Japan. In most cases, the

regulations for air emissions and wastewater in these countries do not require treatment from GPPs. The countries with geothermal

emission limits for the parameters of interest (H2S, Hg, NH3, As, Cooling tower drift, CO2 and CH4) are the Philippines, Indonesia,

two geothermal areas in New Zealand and some areas in the USA. The strictest regulations for H2S ambient air quality standard are


10

in New Zealand, but it is especially noted in their regulation that the guideline is based on odor nuisance and may be unsuitable for

geothermal areas due to their remoteness. In many cases the air quality standard for H2S is based on odor discomfort and then the

need for abatement system really depends on the location of the power plant, e.g. whether it is close to residential areas or not. The

Geyser field in California, USA has strict air quality limits and in Lake County the emission of H2S is limited to 50 g/MWh, that is

the reason why Geyser has the largest amount of treatment plants. The discharge limit for H2S in Wairakei GPP was proposed by

the owner/operator of the plant because of environmental concerns over sulfide toxicity in the Waikato river and how it would

affect renewal of permits. Thus, a viable solution to mitigate the amount of H2S discharged in the river was sought and Contact

Energy voluntarily agreed to reduce the levels by 80% of existing levels. The WHO is a directing and coordinating authority within

the United Nations and their guideline values for H2S and Hg has sometimes been used as a basis in countries where no emission

limit or air quality standard exists. However, all countries studied here have an ambient air quality standard for H2S except for

Mexico.

In countries, such as the Philippines and Indonesia, that have regulations and limits concerning geothermal emission, one might

presume that most GPPs include abatement systems. However, even though regulations are present that apply to GPPs there are not

many abatement systems in place or operational. The limits in the Philippines and Indonesia are wide enough for their operating

GPPs and the set limits are fulfilled without installing an abatement system. Also of interest is that in the Philippines which has an

emission limit, no abatement system is operational but quite a few systems have been tested or implemented there, they were

however deemed unnecessary and were therefore shut down. Since treatment facilities do always include some added cost, it is

often assumed an un-economical option to treat the NCG or GHG if it is not required. In general, GPPs emit less than other energy

sources for the countries and are therefore not the most regulated or monitored plants. In Japan there is a regulated environmental

quality standard for air and measurements and the main geothermal areas are within national parks or protected areas. In Japan

there are therefore examples of abatement systems both for air emissions and wastewater. In Mexico there is no ambient air quality

standard and no abatement systems. They do however monitor ambient air quality in nearby towns as the Cerro Prieto GPP is very

close to the borders of USA and California where strict air quality regulations are present. It can therefore be concluded that

regulations, and the monitoring of them, seem to have an impact on whether there are abatement systems in place or not, even

though they are not the only important parameter.

Since treatment facilities do always include some added cost, it is often assumed an un-economical option to treat the NCG if not

required. If sanctions due to incompliance with pollution regulations cost the operator less than abatement systems advised there is

not a great economic incentive to install them. Despite this there are not many countries that have stipulated shut-down or fines in

case of incompliance. In the USA there are examples of fines though as deployed in e.g. Puna. (United States Environmental

Protection Agency, 2018) However, in Puna the pressure for improvements in NCG abatement comes from the public due to odor

from the hydrogen sulfide released as the power plant is situated near a residential area. Even though the NCG content is not high in

Puna, the H2S proportion is quite high, causing inconvenience in the neighboring area. In California where the sanctions are stricter

and if they are not met, a Notice of Violation will be issued including a fine. Thus, the multiple abatement systems in California can

be traced to the strict regulations set there. Even though actions in case of incompliance are not defined, reports of incompliance

raise awareness in the community. This happened in Iceland for example where pressure from the community led to investigation,

development and application of abatement systems. In Italy the driving force was the enhancing of the air quality of geothermal

areas and the first AMIS installations (2001-2002) were even conducted before promulgation of the regional law that imposed the

installation of the treatment processes for GPPs. Also, in Turkey there is now increased pressure from the investors, international

funds and banks, to investigate and abate pollution from GPPs in Turkey that have estimated CO2 emission greater than in fossil

fueled power plants. Furthermore, the carbon sales or emission trading systems are creating an interesting scenario for the future. It

will be of interest to see if these schemes will set an incentive to install more treatment facilities in GPPs globally. Other examples

of how abatement of emissions from GPPs could be carried economically is if it benefits the operation of the power plant or if it

involves an added income stream. Therefore, it is concluded that the incentive and pressure to install abatement system can be

economical, from regulation or through public opinion.

In light of the global discussion on climate change and importance of emission reduction one might wonder why treatment systems

in geothermal energy are this rare. The lack of incentive to implement the costly systems to reduce emissions is evident and as

discussed above, either some reward or penalty are needed to push these changes. This confirms the findings of other reports within

the geothermal industry on scarcity of abatement systems in GPPs and the existing knowledge gap regarding emissions from GPPs.

A report on “Greenhouse gases from geothermal power production” made by the World Bank in year 2016 for example calls for

actions in the sector to close the knowledge gaps and utilize better the knowledge at hand regarding measurement, monitoring and

abatement of gases in development of new projects. (Fridriksson, et al., 2016) A research project, GEOENVI, recently launched by

the EU under the Horizon2020 program sets out to provide the tools to do that by investigating better the environmental impact of

geothermal power projects in Europe. (Richter, 2018)

6. CONCLUSIONS

Every geothermal field is different in regard to geology and characteristics of the resource such as enthalpy, gas content and gas

composition. Every geothermal energy project is also different concerning project development environment such as market,

regulations, physical environment and public opinion. These factors all impact the choice of technology, execution of the

development project and operation of the plant, ultimately deciding whether or not to install treatment facilities and then which

kind. The global overview conducted based on parameters as described in chapter 2 discovered that only 63 GPPs within 13

geothermal areas have an operational treatment system. This is mainly attributed to the historical fact that geothermal energy is

considered environmentally friendly, only emitting natural emissions, and therefore no basis is established to install treatment

facilities. Two main exceptions are the USA, where treatment facilities have been present in the GPPs since the 1980s, and Italy,

where AMIS systems have been in operation since 2002 and are installed in all GPPs. With increased awareness of the global

climate crisis the view on importance of treatment facilities is shifting. The same is to say with GHG abatement, even though the

debate of whether geothermal emission in anthropogenic or not seems to have affect that. However, in countries such as Turkey

where the CO2 content in geothermal gas is high, reduction measures are increasingly becoming more vital.


11

As H2S emission is of greatest concern, several processes have been developed and installed. The processes available were

categorized as follows; liquid phase oxidation, AMIS, burn and scrub, absorption and Claus and related processes. The abatement

processes for pollutants in NCG and condensate currently in use in operating GPPs are Stretford, LO-CAT/LO-CAT II, Sulferox,

BIOX, Dow RT-2, AMIS, Selectox, Sulfix/Carbfix, Bioreactor, Caustic scrubbing, Combustion and Desulfurization with Mg(OH)2,

Haldor Topsoe (pilot plant), mercury filter and KEPCO arsenic removal. There are various factors that weigh in during selection of

appropriate abatement system such as NCG content and composition. However even though the NCG content is low the H2S

concentration might be high and abatement thus necessary. New methods are being developed such as CarbFix/SulFix, Haldor

Topsoe and Towerbrom to find a solution that fits the field regarding the market and the physical- and regulatory environment. The

Sulfix/Carbfix process was e.g. designed for the Icelandic market as other options were considered too costly and required waste

handling such as of sulfur cakes that there was no market for in Iceland. The Sulfix/Carbfix method, that has been operational in

Iceland since 2012, is now being researched further for replicability within other geothermal fields and for use with industry.

The few existing treatment facilities in GPPs are concentrated mainly in Italy and USA with some exceptions in Iceland, Japan and

New Zealand. This is not very surprising since most of them are H2S abatement systems and Nevada and California in the USA and

Italy have strict ambient air quality standards for H2S and furthermore strict emission limits for GPPs in some counties/areas in the

USA. There are regulations regarding emissions in other countries such as the Philippines and Indonesia. The regulations there are

wide enough, so the operating GPPs are within the set limits as no operational abatement systems are reported there. In the

Philippines, quite a few systems have been tested or implemented, but were however deemed unnecessary and were therefore shut

down. In Iceland pressure from the community was the driving force for change in regulation, leading to implementation of

abatement system where needed. Currently Turkey is experiencing similar pressure from investors as GHG emissions from some of

the GPPs there are very high. From this it can be concluded that naturally occurring low NCG is not the only factor to consider

since e.g. regulations and public opinion are important parameters.

It is concluded that with more widespread and stricter regulations, in line with the increased awareness of the public, more

processes are expected to be developed, or tailored to fit the various geothermal sites and the conditions present there, and thus

increase the number of installed treatment facilities globally. Incentive of some sort is needed as the implementation of abatement

systems is very costly, either a penalty or reward, such as added income stream. The incentive and pressure to install abatement

system can be economical, from regulation or through public opinion.

REFERENCES

Bassi, N, et al. 2018. Arthrospira platensis cultivation using geothermal CO2 and heat. s.l. : 5th AlgaEurope Conference, 2018.

California Air Resource Board. Hydrogen Sulfide & Health. State of California. [Online] [Citeret: 4. 7 2019.]

https://ww2.arb.ca.gov/resources/hydrogen-sulfide-and-health.

2019. Controlled Thermal Resources. Hell's Kitchen Lithium-Geothermal Stage 1. [Online] 29. 1 2019.

https://www.cthermal.com/the-project/.

Fridriksson, Thráinn, et al. 2016. Technical report 009/16; Greenhouse gases from geothermal power production. Washington :

ESMAP, The World Bank, 2016.

Huidobro, Patricia Marcos. 2013. Kenya's first Carbon Credits from Geothermal Energy Pay for Schools. Development in a

Changing Climate. [Online] 11 2013. http://blogs.worldbank.org/climatechange/kenya-s-first-carbon-credits-geothermal-

energy-pay-schools.

Markets Insider. 2018. CO2 European Emission Allowances. Markets Insider. [Online] 24. 09 2018.

https://markets.businessinsider.com/commodities/co2-emissionsrechte.

Nagl, Gary J. 1999. Controlling H2S emissions in geothermal power plants. 1999.

Pineda, Esteban José Rodríguez. 2013. Review of H2S abatement in geothermal plants and laboratory scale design of tray plate

distillation tower. 2013.

2019. Resource Park. The companies within the Resource Park. [Online] 29. 1 2019. https://www.resourcepark.is/companies/.

Richter, Alexander. 2018. European research project to respond to environmental concerns on geothermal development.

ThinkGeoEnergy. [Online] 11 25, 2018. http://new.thinkgeoenergy.com/european-research-project-to-respond-to-

environmental-concerns-on-geothermal-development/.

—. 2018. Global Geothermal Capacity reaches 14,369 MW - Top 10 Geothermal Countries. ThinkGeoEnergy. [Online] October

2018. http://www.thinkgeoenergy.com/global-geothermal-capacity-reaches-14369-mw-top-10-geothermal-countries-oct-

2018/.

Twidale, Susanna. 2018. What is driving a rally in EU carbon permit prices? Reuters. [Online] 15. 08 2018.

https://www.reuters.com/article/us-eu-carbon-rally/what-is-driving-a-rally-in-eu-carbon-permit-prices-idUSKBN1L015Y.

United Nations Framework Convention on Climate Change. 2018. Parties. UNFCCC. [Online] 2018.

https://unfccc.int/process/parties-non-party-stakeholders/parties-convention-and-observer-

states?field_partys_partyto_target_id%5B512%5D=512&field_partys_partyto_target_id%5B511%5D=511.

United States Environmental Protection Agency. 2018. EPA finds Puna Geothermal Venture violated chemical safety rules.

EPA. [Online] 25. 11 2018. https://archive.epa.gov/epa/newsreleases/epa-finds-puna-geothermal-venture-violated-chemical-

safety-rules.html.

World Health Organisation (WHO). 2016. Air quality standards under the Air Quality Directive, and WHO air quality

guidelines. EEA . [Online] 12. 12 2016. https://www.eea.europa.eu/data-and-maps/figures/air-quality-standards-under-the.


12

World Health Organization. Occupational and Environmental Health Team. 2006. WHO Air quality guidelines for particulate

matter, ozone, nitrogen dioxide and sulfur dioxide : global update 2005 : summary of risk assessment. Geneva : World Health

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Regional Office for Europe, 2000.


13

Table: List of the geothermal power plants studied, and the abatement system installed if present. Geothermal Area,

country

Geothermal Plant Units Installed capacity

[MWe]

Type of abatement system

Hengill, Iceland Hellisheiði 7 303 CarbFix and SulFix

Hengill, Iceland Nesjavellir 3 120

Svartsengi, Iceland Svartsengi 5 76,4 Haldor Topsoe H2S removal pilot plant

CO2 supplied to CRI demonstration plant (to

produce methanol)

West Java, Indonesia Gunung Salak 6 360

West Java, Indonesia Darajat 3 256

West Java, Indonesia Wayang Windu 2 227

Sarulla, Indonesia SIL 7 110

Sarulla, Indonesia NIL-1 7 110

Sarulla, Indonesia NIL-2 7 110

Dieng, Indonesia Dieng 1 60

West Java, Indonesia Kamojang 5 235

Ulubelu, Indonesia Ulubelu I 2 110

Ulubelu, Indonesia Ulubelu I 2 110

Hatchobaru, Japan Hatchobaru 3 110 Arsenic removal in units 1&2

Hachijo-jima, Japan Hachijo-jima 1 3,3 H2S abatement, combustion and desulfurization

with Mg(OH)2

Yanaizu-Nishiyama,

Japan

Yanaizu-Nishiyama 1 30 Selectox and claus H2S abatement system

Otake, Japan Otake 1 12,5 H2S bioreactor

Olkaria, Kenya Olkaria I 5 185

Olkaria, Kenya Olkaria II 3 105

Olkaria, Kenya Olkaria III 4 139

Olkaria, Kenya Olkaria IV 2 140

Olkaria, Kenya Wellhead Units 14 81,1

Cerro Prieto, Mexico Cerro Prieto 1 5 180*

Cerro Prieto, Mexico Cerro Prieto 2 2 220



Kawerau, New Zealand Kawerau 1 106

Rotokawa, New Zealand Nga Awa Purua 1 132

Wairakei, New Zealand Te Mihi 2 166

Wairakei, New Zealand Wairakei A 6 67,2 Bioreactor for H2S removal

Wairakei, New Zealand Wairakei B 4 94 Bioreactor for H2S removal

Wairakei, New Zealand Wairakei binary 1 14 Bioreactor for H2S removal

Makiling-Banahaw,

Philippines

Mak-Ban A 2 126,4

Makiling-Banahaw,

Philippines Mak-Ban B 2 126,4

Makiling-Banahaw,

Philippines

Mak-Ban C 2 110

Makiling-Banahaw,

Philippines Mak-Ban D 2 40

Makiling-Banahaw,

Philippines

Mak-Ban E 2 40

Makiling-Banahaw, Mak-Ban Binary 6 15,73


14

Geothermal Area,

country


[MWe]


Philippines

Leyte, Philippines Malitbog 3 232,5

Leyte, Philippines Mahanagdong A 4 132,5

Leyte, Philippines Mahanagdong B 2 66,25

Tiwi, Philippines Tiwi I 2 110

Tiwi, Philippines Tiwi II 2 110

Tiwi, Philippines Tiwi III 2 110

Leyte, Philippines Tongonan I 3 112,5

Leyte, Philippines Upper Mahiao 4 125

Kizildere, Turkey Kizildere II 1 80

Germencik, Turkey Gurmat 1 1 47,4

Germencik, Turkey Efe 1 1 47,4




Salavatli, Turkey Dora I 1 7,9

Pamukören, Turkey Pamukören I & II 2 48

Geyser, USA Big Geysers #13 1 138 Stretford

Geyser, USA Sulfur Springs #14 1 113 Stretford and Mercury filter

Geyser, USA Quicksilver #16 1 118 Stretford

Geyser, USA Lake View #17 1 118 Stretford

Geyser, USA Socrates #18 1 118 Stretford

Geyser, USA Calistoga #19 1 80 Stretford

Geyser, USA Grant #20 1 118 Stretford

Geyser, USA Sonoma #3 1 78 Stretford

Geyser, USA NCPA I 2 110 Stretford and Mercury filter

Geyser, USA NCPA II 2 110 Stretford and Mercury filter

Geyser, USA McCabe #5&#6 2 110 Burner/scrubber and DOW RT-2

Geyser, USA Ridge Line #7&#8 2 110 Burner/scrubber and DOW RT-2

Geyser, USA Eagle Rock #11 1 110 Burner/scrubber and DOW RT-2

Geyser, USA Aidlin #1 2 20 Burner/scrubber and DOW RT-2

Geyser, USA Cobb Creek #12 1 110 Caustic scrubbing and iron chelate in the

condensate

Geyser, USA Bottle Rock II 1 55**

Geyser, USA Bear Canyon 2 78**

Geyser, USA West Ford Flat 2 110**

Salton Sea, USA John L. Featherstone (Hudson

Ranch I)

1 50 BIOX

Salton Sea, USA Salton Sea I 1 10

Salton Sea, USA Salton Sea II 3 21

Salton Sea, USA Salton Sea III 1 54

Salton Sea, USA Salton Sea IV 1 48

Salton Sea, USA Salton Sea V 1 58

Salton Sea, USA Vulcan 2 40


15

Geothermal Area,

country


[MWe]


Salton Sea, USA CE Turbo 1 10

Salton Sea, USA Del Ranch (Hoch) 1 49

Salton Sea, USA Elmore 1 49

Salton Sea, USA Leathers 1 49

Coso, USA Navy I 3 90 LO-CAT for H2S and activated carbon filter for

Mercury

Coso, USA Navy II 3 90 LO-CAT for H2S and activated carbon filter for

Mercury

Coso, USA BLM 3 90 SulFerox and activated carbon filter for Mercury

Steamboat Springs, USA Galena I (Richard Burdett) 2 30

Steamboat Springs, USA Galena II 1 13,5

Steamboat Springs, USA Galena III 1 30

Puna, USA Puna 12 38**

Larderello, Italy Sesta 1 1 20 AMIS

Larderello, Italy Farinello 1 60 AMIS

Larderello, Italy Nuova Gabbro 1 20 AMIS

Larderello, Italy Nuova Larderello 1 60 AMIS

Larderello, Italy Valle Secolo 1 1 60 AMIS

Larderello, Italy Valle Secolo 2 1 60 AMIS

Larderello, Italy Nuova Castelnuovo 1 14,5 AMIS

Larderello, Italy Nuova Molinetto 1 20 AMIS

Travale-Radicondoli,

Italy

Nuova Radicondoli 1 1 40 AMIS


Italy

Nuova Radicondoli 2 1 40 AMIS


Italy Pianacce 1 18 AMIS


Italy

Rancia 1 1 18 AMIS


Italy Rancia 2 1 18 AMIS


Italy

Travale 3 1 20 AMIS


Italy Travale 4 1 40 AMIS shared with Travale 3


Italy

Chiusdinio 1 20 AMIS

Larderello, Italy Nuova Rossi Lagoni 1 8 AMIS

Larderello, Italy Nuova Serrazzano 1 60 AMIS

Larderello, Italy Monteverdi 1 1 20 AMIS

Larderello, Italy Monteverdi 2 1 20 AMIS

Larderello, Italy Carboli 1 1 20 AMIS

Larderello, Italy Carboli 2 1 20 AMIS

Larderello, Italy Nuova Lago 1 10 AMIS

Larderello, Italy Nuova Monterotondo 1 10 AMIS

Larderello, Italy Nuova S. Martino 1 40 AMIS

Larderello, Italy Cornia 2 1 20 AMIS

Larderello, Italy Le Prata 1 20 AMIS


16

Geothermal Area,

country


[MWe]


Larderello, Italy Nuova Sasso 1 20 AMIS

Larderello, Italy Sasso 2 1 16 AMIS shared with Nuova Sasso

Larderello, Italy Selva 1 1 20 AMIS

Mt. Amiata, Italy Bagnore 3 + orc 1 20 AMIS and NH3 abatement

Mt. Amiata, Italy Bagnore 4 1 40 AMIS and NH3 abatement

Mt. Amiata, Italy Piancastagnaio 3 1 20 AMIS



Total 265 9623,98

* Currently only 1 unit and 30 MW running.

** Not in operation

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