Partner Reported Opportunities (PROs) PRO Fact Sheet No. 206 for Reducing Methane Emissions 

Zero Emissions Dehydrators 

Technology/Practice Overview 

Description 

Produced natural gas is saturated with 

water, which must be removed in 

preparation for transmission. The oil 

and gas industry relies heavily upon

glycol dehydrators using triethylene 

glycol (TEG) to remove water from gas. 

Dehydrators can produce significant 

methane emissions from the venting of

still column vapors, as well as leaks from

gas-driven glycol circulation pumps and 

pneumatic controls. Some of these 

emissions include methane, volatile 

organic compounds (VOCs) and 

hazardous air pollutants (HAPs). 

Zero emissions dehydrators combine 

several technologies to virtually 

eliminate methane emissions. This 

equipment includes flash tanks, electric 

pumps and electric control valves, which

reduce emissions by avoiding use of 

pneumatic gas. Zero emissions 

dehydrators are also designed to collect

all condensable components from the 

still column vapor and use the remaining

non-condensable still vapor (methane

and ethane) as fuel for the glycol reboiler. 

A water exhauster removes water from 

the wet glycol stream and yields high

glycol concentrations without the use of 

a gas stripper. Electric circulation 

equipment are used instead of gas driven

pumps to eliminate gas emissions from 

natural gas-driven diaphragm pumps. 

Another option is to replace methane

with compressed air as the operating gas 

for pneumatic controls. This eliminates 

significant methane emissions from 

valves and controllers. 

Estimated 

Gas Price 

Annual 

Methane 

Savings 

Value of 

Annual 

Gas Savings* 

Estimated 

Implementation Cost 

Incremental 

Operating 

Cost 

Payback 

(months) 

$7.00/Mcf 33,900 — 

37,300 Mcf $253,000 —$278,000 $22,065—$63,300 $165—$6,500 <1 — 4 Months 

$5.00/Mcf 33,900 — 

37,300 Mcf $180,500 —$199,000 $22,065—$63,300 $165—$6,500 1 — 5 Months 

$3.00/Mcf 33,900 — 

37,300 Mcf $108,300 —$119,200 $22,065—$63,300 $165—$6,500 2 — 8 Months 

Economic and Environmental Benefits 

Economic Evaluation 

 Reduced maintenance costs 

 Reduced fuel cost for the re-boiler 

Additional Benefits: 

Estimated annual methane emission reductions 31,400 Mcf per average application 

Natural Gas and Methane Savings 

* Whole gas savings are calculated using a conversion factor of 94% methane in pipeline quality natural gas. 

Compressors/Engines 

Dehydrators 

Directed Inspection & 

Maintenance 

Pipelines 

Pneumatics/Controls 

Tanks 

Valves 

Wells 

Other 

Applicable Sector(s) 

Production 

Processing 

Transmission 

Distribution 

Other Related Documents: 

Reroute Glycol Skimmer Gas, 

PRO No. 201 

Convert Natural Gas-Driven 

Chemical Pumps, PRO No. 202 

Pipe Glycol Dehydrator to Vapor 

Recovery Unit, PRO No. 203 

Portable Desiccant Dehydrators, 

PRO No. 207 

Convert Pneumatics to Mechanical Controls, PRO No. 301 
 

 

 

 

 

 

 

PRO Fact Sheet No. 206 Continued 

Zero Emissions Dehydrators (Cont’d) 

Operating Requirements 

Glycol dehydrators require electric utilities or an enginegenerator set to achieve zero emissions. A five kW 

generator set for electrical power will allow the 

conversion of all gas fueled pumps to electric as well as 

the use of electric controllers. An electric compressed air 

system with storage vessels for fuel air can also be used

to actuate various controls throughout the system. 

Flash tank separators capture methane that flashes or 

evaporates from rich glycol (water wet glycol) in an 

energy-exchange pump. Flash tank separators recover 

about 90 percent of methane emissions and reduce VOCs 

by 10 to 40 percent. These installations require an

outlet for low pressure gas such as a vapor recovery unit, 

compressor suction or fuel line. 

Some partner companies install glycol still column 

condensers to comply with current regulation of HAP 

emissions. Still column condensers require routing of

the non-condensable methane and ethane to a low 

pressure fuel line, VRU or flare. Desiccant dehydrators

can be used in place of glycol dehydrators. Desiccant 

dehydrators eliminate the use of glycol in the process

which also eliminates most of the methane emissions 

associated with dehydrators. Refer to the Lessons 

Learned paper, Replacing Glycol Dehydrators with 

Desiccant Dehydrators. The water content of produced 

gas that can be removed by desiccant dehydrators 

depends upon the temperature and pressure of the gas 

and the type of desiccant. Desiccant dehydrators are 

most effective for higher pressure, lower temperature 

conditions and comparatively low flow rates. 

Applicability 

New dehydrators can be designed to eliminate methane,

VOC, and HAP emissions. In addition, existing glycol 

The average methane content of natural gas varies by natural gas 

industry sector. The Natural Gas STAR Program assumes the 

following methane content of natural gas when estimating methane savings for Partner Reported Opportunities. 

Production 79 % 

Processing 87 % 

Transmission and Distribution 94 % 

Methane Content of Natural Gas 

dehydrators can be retrofitted with zero emissions 

technology through modifications of the gas stream

piping, valves, pumps, and controllers, as well as 

modification of the fuel used, and/or the dehydrating

media. Partners can apply zero emission dehydrator 

technologies to various onshore and offshore production,

processing and gas transportation settings. 

Methane Emissions 

The reductions in natural gas losses are calculated 

assuming a conventional dehydrator processing 28 

MMcf/day (million cubic feet per day) with a glycol 

circulation rate of 4 gpm (gallons per minute). The zero 

emissions dehydrator eliminates emissions from glycol

circulation pumps, gas strippers, and most of the still 

column effluent. 

Economic Analysis 

Basis for Costs and Savings 

A conventional dehydrator of similar size (processing 28

MMcf/day) shows losses of 5.95 scf (standard cubic feet) 

Table 1. Zero Emission Dehydrator Technology Examples; Partner-Reported Costs and Savings 

Option Capital Costs Annual O&M Cost Annual Methane 

Emission Savings 

Install Flash Tank $6,500 - $18,800 Negligible 1,191 – 10,717 Mcf 

Install Electric Pump $1,400 - $13,000 $165 - $6,500 360 – 36,000 Mcf 

Glycol Still Column Condenser $14,000 - $25,000 not reported 400 – 5,033 

TOTAL $21,900 - $56,800 $165 - $6,500 1,951 – 51,750 

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PRO Fact Sheet No. 206 Continued 

Zero Emissions Dehydrators (Cont’d) 

per gallon of glycol that is circulated with a Kimray 

pump at 4 gpm. The conventional dehydrator also has 

gas losses of 4 scf per gallon of glycol that is circulated

through the gas stripper. A zero emissions dehydrator 

avoids these gas losses by eliminating Kimray pumps 

and gas strippers. Condensate is also recovered from the 

still column vapor at 2.88 gal/hr (gallons per hour) while 

the non-condensable vapor is used to fuel the glycol reboiler in the zero emissions dehydrator. Two to four 

cubic feet per minute of gas venting is eliminated by

replacing gas pneumatic controllers with electric 

controls. Examples of Natural Gas STAR Partner 

reported emissions savings and corresponding 

implementation costs for different zero emission 

dehydrator technologies are provided in Table 1. 

Discussion 

Installation costs for a zero emissions dehydrator are 

similar to those for a conventional dehydrator with a

thermal oxidizer. Electric motors and controllers offer 

several benefits as compared to gas-powered devices;

they are more reliable and efficient and provide lower 

operating and maintenance costs. The cost of electric 

Conventional Glycol Dehydrator System 

power is generally offset by increased methane and 

condensate production sales. Overall benefits of zero 

emission dehydrators include: 

Rapid return on investment through gas savings, 

Increased operational efficiency 

Reduced O&M costs 

Reduced Compliance Cost for HAPs and BTEX 

EPA provides the suggested methane emissions estimating methods contained 

in this document as a tool to develop basic methane emissions estimates only. 

As regulatory reporting demands a higher-level of accuracy, the methane emission estimating methods and terminology contained in this document may not 

conform to the Greenhouse Gas Reporting Rule, 40 CFR Part 98, Subpart W 

methods or those in other EPA regulations. 

Source: U.S. EPA, Environmental Technology Verification (ETV) Program 

(CO, CO2 , NOx ) 

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PRO Fact Sheet No. 206 Continued 

Zero Emissions Dehydrators (Cont’d) 

Quantum Leap Dehydrator System (A Zero Emissions Dehydrator) 

(CO, CO2 , 

NOx ) 

Source: U.S. EPA, Environmental Technology Verification (ETV) Program 

2011
 

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