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Is Natural Gas Critical to Reducing U.S. Carbon Emissions?

John Miller's picture
Owner-Consultant Energy Consulting

During my Corporate career I provided manufacturing with power generation facilities’ technical-operations services and held different technical and administrative management positions.  In order...

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Total U.S. carbon emissions peaked during the mid 2000’s.  The reduction of carbon emissions has been attributed to factors such as the recent large expansions of wind and solar power.  Other factors that have also significantly reduced U.S. carbon emissions since 2005 are energy efficiency increases, expanded biofuels and replacing coal with natural gas.  While renewable energy and biofuels are strongly supported by State and Federal Governments, the recent boom in natural gas production from shale reserves has faced increasing criticisms and growing political opposition. 

For the U.S. to substantially reduce its future carbon emissions, higher carbon intensity coal and petroleum fossil fuels must to be replaced with lower carbon alternatives.  Besides further increasing renewables energy supplies and increasing energy efficiency, can U.S. total carbon emissions be substantially reduced without increased lower carbon natural gas? 

Brief History of U.S. Carbon Emissions – the generation of carbon emissions from the consumption of fossil fuels has generally increased in tandem with the overall population and the economy’s growth.  Refer to the following graph.


Source: EIA MER data Table 12.1

Between 1981 and 2005 the U.S. total population increased from 230 to 295 million and the total national GDP doubled.  Total U.S. carbon emissions increased from 4,500 to 6,000 million metric tons per year (MMT/yr.) during the same period.  Due to the oil crises of the 1970’s-early 1980’s the U.S. implemented many regulations intended to replace petroleum oil with alternatives fuels and supported-mandated energy efficiency increases.  Petroleum alternatives included alcohols, LPG, natural gas and electricity.  Over the past decade, State and Federal Governments have increasingly supported different renewable energy sources including biomass and wind/solar power, and further increases in energy efficiency.  All of these petroleum alternatives and efficiency improvements helped lead to peaking of total U.S. carbon emissions and very significant reductions since 2005.

Other factors that have significantly contributed to reduced U.S. carbon emissions are the recent new growth in domestic natural gas production-consumption and EPA regulations that have restricted new coal power plant construction.  The rapid increase in domestic natural gas production from shale reserves has significantly impacted the economics of coal fuels used for power and heat in recent years.  This recent shale natural gas boom has not only reversed the depletion trend of conventional natural gas production from a few years ago, but has actually flooded markets supplies.  This has caused natural gas price declines towards (inflation adjusted) historic lows.  These factors have made coal-to-natural gas ‘fuels switching’ very economically attractive to the Power and Industrial sectors.

Factors That Have Affected Recent U.S. End-use Sectors’ Carbon Emissions – Total U.S. carbon emissions recently peaked due to the combination of Government energy policies and free market factors.  Since 2005 the consumption of higher carbon fossil fuels has begun to decline very significantly, which has caused individual U.S. end-use Sectors’ carbon emissions to also decline.  Refer to the following graph.


Source: EIA MER data Tables 12.1 thru 12.6.  Carbon emissions based on ‘primary energy’ consumption only.

The carbon emissions of all end-use Sectors have decreased since 2005.  The largest reductions appear to be due to the Electric Power and Transportation sector’s emissions, followed by the Industrial, Residential and Commercial sectors. 

AllU.S. end-use Sectors’ carbon emissions have been impacted by a broad range of factors.  These include expanding renewable energy, increasing efficiency, and replacing coal with lower carbon alternatives.  The following summarizes some of the most significant factors which have successfully reduced carbon emissions in each end-use Sector 2005-2012:

  • Residential – natural gas and petroleum heating oil consumption has declined significantly.  These fossil fuels have been replaced by geothermal and electric heat pumps, and reduced by a large increase in residences’ thermal efficiencies; increased insulation and appliance efficiencies.  Distributed solar PV has also increased.
  • Commercial – coal and petroleum heating oil consumption has declined significantly.  Reduced consumption is largely due to energy efficiency increases.  One of the largest improvements has been a very significant increase in biomass based energy used for heat and distributed power generation.  In addition the use of geothermal heat systems has expanded significantly.
  • Industrial – petroleum and coal consumption has declined very significantly.  This has been due to large energy efficiency increases across most Industries and ‘fuels switching’ from coal and petroleum to natural gas.  Significant increases of biomass energy have also reduced the need for fossil fuels.
  • Transportation – petroleum motor fuels consumption has very significantly decreased due to increasing CAFE (fuel efficiency) standards.  The expansion of liquid biofuels has also significantly reduced petroleum consumption.  The replacement of petroleum with alternative natural gas fuels has made a small contribution towards total reduced carbon emissions.  The impact of electric vehicles has surprisingly been relatively insignificant.
  • Power – the largest reduction to carbon emissions is due to coal-to-natural gas ‘fuels switching’ and construction of higher efficiency power plants.  Expansion of renewable power, overwhelmingly due to expanded wind power, has been the second largest factor to reduced Power Sector carbon emissions. 

Another general factor that has affected overall end-use Sectors and markets fossil fuels use has been a change of Consumer behavior.  Beside the impacts of the recent economic recession (high unemployment and reduced income), Consumer concerns for the environment has also possibly reduced fossil fuels consumption and increased energy efficiency.

Innovative Technologies Impact on Carbon Emissions – there is no question that innovation and creative improvements have contributed substantially to renewable energy development and expansions.  Significant improvements have also contributed to the thermal efficiency and carbon emission reductions of replacing coal with state-of-art natural gas power generation technology.  The largest improvement has been upgrading older basic and relatively inefficient fossil fuels fired boilers & steam turbine generators with state-of-art combined cycle natural gas (CCNG) turbine power generation plants.  To illustrate refer to the following graph.


Source: EIA MER data Tables 2.6 and 7.2b.  The energy efficiency is estimated based on the unit heat:power value of 3413 Btu per KWH.

The above graph shows the significant difference between average U.S. CCNG and coal power plant efficiencies.  Since about 2000 the penetration of CCNG power plants has grown quite substantially.  The efficiency of conventional coal power plants has remained relatively constant until recent years.  Increasingly strict environmental regulations, which have required installation of emissions controls, have slightly decreased average coal power plant energy efficiencies.

In addition to thermal efficiency another factor that affects the reduction in carbon emissions of coal-to-natural gas ‘fuels switching’ are the physical ‘carbon factors’.  The EIA carbon factors for coal and natural gas are 95 and 53 kgCO2/MBtu respectively.  The combination of carbon factors and thermal efficiency has contributed to the carbon emissions differences per unit power generation of coal & natural gas.  Refer to the following graph.


Source: EIA MER data Tables 12.6 and 7.2b.  Note: NG – natural gas

The carbon emissions of average conventional coal power plants are now over twice that of natural gas power plants per KWH.  The combination of increased efficiency and reduced fuel costs have been major factors to the rapid replacement of coal with natural gas in recent years. 

Major Contributing Factors to Actual U.S. Carbon Emission Reductions – U.S. carbon emissions from the consumption of fossil fuels have declined by 700 MMT/yr. since 2005.  The reduction of carbon emissions has been due to four primary factors: 1) Improved Energy Efficiency, 2) Coal-to-Natural Gas Fuels Switching, 3) Increased Renewable Power + Heat, and, 4) Increased Liquid Biofuels.   Based on my detailed analysis of each end-use Sector’s energy consumption, the following table was developed to show the four different carbon emission reduction categories’ impacts on reducing U.S. carbon emissions 2005-2012.


Source: EIA MER data Tables 2.2-2.6 and Tables 12.2-12.6.  Note: Power sector natural gas efficiency+carbon factor impacts are classified as coal-to-NG fuel switching only since these are dependent variables.  Liquid biofuels impact is based on 20% average carbon emission reduction of the full lifecycle balances per the EISA 2007 standard for conventional ethanol.

The above table shows that 50% of the total reduced U.S. carbon emissions over the past 7 years are due to reduced Electric Power sector’s emissions.  This improvement resulted at nearly constant total U.S. power generation rates between 2005 and 2012.  The second largest (22%) reduction in U.S. carbon emissions is due to improvements in the Transportation sector, followed by the Industrial sector (18%). 

The table also shows that coal-to-natural gas ‘fuels switching’ is the largest contributing factor category (47%) towards reduced total U.S. carbon emissions 2005-2012.  The second largest contributing factor is increased ‘energy efficiency’.  Although renewable power/energy and biofuels have been very strongly supported and have increased significantly, these two factors have only contributed to 12% and 2% respectively towards total reduced U.S. carbon emissions over the past 7 years. 

U.S. Carbon Emissions Without Natural Gas – without the contribution of coal-to-natural gas ‘fuels switching’ over the past 7 years total U.S. carbon emissions could have increased up to 328 MMT/yr., or the costs of electric power and natural gas heating fuels would have increased substantially.  If the recent boom in domestic shale (natural) gas had not occurred or was not allowed to develop, the U.S. would have been forced to import increasing and substantial amounts of liquefied natural gas (LNG) after about 2005.  Without shale gas U.S. conventional natural gas production would have continued to deplete well below domestic demand levels.  Importing LNG to meet growing demand could have increased natural gas heating and power costs by over double current retail market prices.

Renewable energy development would have also been affected significantly without increased shale gas.  Variable wind and solar power cannot displace baseload coal power directly and requires 100% intermediate-peaking natural gas backup power in order to reliably supply existing power grids.  Without natural gas power backup, increasing levels of variable wind/solar power would compromise power grid stabilities-reliabilities (i.e. increased black-outs).  Biofuels also consumes significant amounts of natural gas during overall lifecycle cultivation-through-production & distribution.  Only hydro, biomass and geothermal renewable power sources or nuclear power can feasibly replace coal power directly without the need for natural gas backup.

With the recent and planned EPA regulations that make new and many existing coal power plants uneconomical, the U.S. will be required to displace this critical baseload power capacity by either importing increasing amounts of LNG and/or substantially expanding all non-coal power sources, other than variable wind and solar power.

Feasible Reductions of Future U.S. Carbon Emissions – significantly reducing U.S. total future carbon emissions will require a Federal ‘energy policy’ that builds on the successes of recent years.  This should include not only continued increases in energy efficiency and further development of reasonably cost effective renewable energy, but also, new support for current-future shale gas production.  Until the U.S. either substantially expands hydroelectric power and associated pumped storage or realistically develops alternative Industrial scale electric power storage, expanded renewable wind and solar will continue to require essentially 100% CCNG power backup.

To comply with current and future EPA regulations that will prevent new construction and likely shutdown significant existing coal power plants, this capacity must be replaced by either baseload renewable power (geothermal, biomass or hydropower), expanded nuclear power, and/or increased CCNG power capacity.  Of these feasible alternatives to existing coal power, new CCNG power plant capacity is currently the most cost effective.  To ensure that the needed domestic shale gas supplies are available to meet future growing U.S. demand the Federal Government needs to change its current strategies towards the Natural Gas Industry and the developing hydraulic fracturing technology.  Rather than just putting up barriers to current and future shale gas development, the Federal Government needs to work with the Natural Gas Industry and help facilitate the development of critical domestic natural gas supplies in an environmentally responsible manner.  Only through a cooperative partnership between the responsible Federal Agencies and the Natural Gas Industries will the U.S. be capable of making the greatest progress towards reducing total future carbon emissions and ensuring the critically needed natural gas supplies are available during the interim until alternative renewable energy supplies are truly capable of replacing the need for all fossil fuels.


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J Elliott's picture
J Elliott on Mar 13, 2013

Natural gas looks like a key element to reducing current and future carbon dioxide emissions.  Are developing plans to possibly export America’s growing natural gas production from shale deposits consistent with reducing our future greenhouse gas emissions?

Ivor O'Connor's picture
Ivor O'Connor on Mar 13, 2013

Nice work digging up the graphs and applying the proper references. 


You did not mention the three most important solutions to reducing carbon in your summarizing paragraph though. That is solar, wind, and HVDC power lines. I think it is because you don't see either wind or solar as a "baseload" power source. However if you look at energy production as a whole and not at one singular power plant then the laws of large numbers come into play and solar plus wind can be counted on as a baseload. The tying together of wind and solar in physically remote areas is done with HVDC power lines. HVDC allows electricity to be transported about 10x further than the current 100 year old power grid technology we use. So instead of talking about a west coast and east coast grid we could be talking about a north american and south american grid. Anywher there is sun shining or wind blowing in north america it would be about the same as wind or sun shining in your current localality. 

Ron Wagner's picture
Ron Wagner on Mar 13, 2013

I love wind and solar, but they have not allowed Europe to match our level of pollutant reductions. Not even close. In fact theri illogical policies have them importing our dirty coal.

Ron Wagner's picture
Ron Wagner on Mar 13, 2013

China burns almost as much coal as the whole world combined. Guess where that pollution ends up, all over the world. They have many sources of natural gas and are making it a priority to switch, but we will see. They are already way ahead of us in the CNG and LNG vehicle area. 

We actually have enough natural gas to export without affecting our own supply. Many nations are exporters and those who aren't either will be, or will be attempting to meet their own needs. Biogas can actually play a large role in the world. It is underutilized, economical, and carbon neutral. It has an added cachet in Europe. 

Japan is working on developing methane hydrates, and just had some success a couple of days ago. The USA and many nations are working on that. Methane hydrates contain more natural gas than all land based forms. 

Leo Klisch's picture
Leo Klisch on Mar 13, 2013

Minnesota Power In NE Minnesota just filed there 10 year resource plan to the PUC. They decided to shut down two smaller coal plants rather than install emission controls minus CO2. The big Boswell "baseload" coal plant at around 1000mw will continue to burn coal from most likely the parent companies coal mine in North Dakota. . Also have 400mw of North Dakota wind with 100 to 200mw more planed. Some hydro existing but 250mw of Manitoba hydro planed. Over the next decade they do plan to incorporate natural gas generation first to fire existing boilers then CCGT's to the ultimate goal of 1/3 coal,1/3 gas, 1/3 renewables, but only as load increases. To keep the 54 year old Boswell plant going, some $350 million will need to be spent on emission hardware not counting CO2 of course. So unless there is a cost of carbon,it will take maybe two decades to reach this goal. Seems they should just accelerate there plan by shutting down the 1000MW coal spending the $350 million on CCGT's and more renewables This seems like the classic case you explained above to replace coal with CCGT's since I believe they have the gas available. 

John Miller's picture
John Miller on Mar 13, 2013

J E, depending on how aggressive the EPA is in shutting down existing coal power plants and whether new nuclear base-load power generation capacity is allowed or actually develops, the need for future natural gas supply could increase quite substantially.  Without large increases in nuclear power, the need for U.S. natural gas consumption could double current rates if the vast majority of existing coal power were to shutdown in the next 10-20 years.  This situation will make any future natural gas exports problematic.  In the short-term, the export of natural gas appears to be justified based on normal free market principles.  As more coal plants shutdown, the current and near future excess natural gas supplies could rapidly disappear due to increasing domestic demand.  This situation would eventually lead to discontinuing all exports.

John Miller's picture
John Miller on Mar 13, 2013

Ronald, agreed displacing petroleum motor fuels with natural gas has continued to lag within the U.S. compared to other countries.  The use-development of biogas appears to be significantly promising as an expanded future renewable energy source.  Biogas is however generally limited to heating fuels applications since in its raw form it contains large amounts of CO2, NH3 and other co-product gases that depressed its unit volume heating value.  To be efficiently used as an alternative to petroleum motor fuels, the raw biogas needs to be processed and purified, which unfortunately consumes significant addition energy.

The developing of methane hydrate production could conceivable be the next energy boom following hydraulic fracturing of shale (natural) gas.  The potential methane hydrate recovery technology also has the added benefit of potentially recovering the methane hydrates before they breakdown naturally.  Some scientists believe that future breakdown of methane hydrates will lead to large increase in methane greenhouse gas releases due to increasing world temperatures.

John Miller's picture
John Miller on Mar 13, 2013

Ivor, yes based on current U.S. power grid hardware and AC technologies I do not believe that variable wind and solar have the capability to displace baseload power generation supply.  Baseload power must have the capability to be reliably scheduled to meet daily changes in demand (independent of the weather or time of day).  The use of high voltage direct current (HVDC) transmission systems theatrically could allow increased penetration of variable wind and solar into baseload power generation capacity if the systems were properly designed to balance out routine and non-routine system supply-demand load variations.  Solar has the advantage of generating maximum power during normal daily peaking power demand periods (late AM and mid PM).  Wind has the advantage of producing power after the sun goes down to displace the lost solar power.  Few existing systems appear to be designed to take advantage of these normal performance variables.

The problem statement for better balancing variable wind/solar power is that their location and capacities, and associated HVDC transmission as you have recommended, have not been designed as part of larger regional or an overall U.S. power grid supply-demand macro system.  Instead, renewable wind/solar has generally been designed and developed as standalone generation facilities.  The integration of new variable wind/solar generation capacity into adjacent power grids generally relies on existing AC transmission systems and is left up to the individual local or sub-regional Power Utility Companies to balance and manage their systems supply-demand stabilities.  This often means taking advantage of existing natural gas intermediate and peaking power capacity, without any cost considerations to the supplier of the variable and unreliable renewable wind/solar power.  Since most power grids are primarily designed and operated to supply on-demand, uninterruptable power to most customers, the variable wind and solar increases the magnitude and timing of overall supply-demand balances and control dynamics complexities.

Ivor, you are likely correct that if the U.S. power systems were designed overall to better balance variable wind/solar with more efficient HVDC transmission systems the need of backup natural gas intermediate-peaking power could be substantially reduced.  The U.S. generally has the expertise and tools to design the systems such as the NERC.  The problem is that State and Federal Governments have yet to develop a nationwide plan to significantly expand variable renewable wind/solar power.  Instead, we have a number of random regulatory actions the result in random, uncoordinated construction of wind/solar without consideration for need of a nationwide master plan, including development of extensive HVDC transmission systems.

Ron Wagner's picture
Ron Wagner on Mar 13, 2013

I have several stories about very large biogas programs by very large dairies that are cost competitive. The biogas is to be used in CNG stations and by many large dairy trucks.There will be many CNG stations supported by these companies. I think this is going to be a big trend, and the cachet will be valuable to the natural gas fueling movement. It will also be a trend in agriculture, given time.

Here are some references:


John Miller's picture
John Miller on Mar 14, 2013

Wind Smith, having one third coal, gas and renewables appears fairly aggressive towards the penetration of renewables, particularly if the vast majority comes from variable wind power.  It will be interesting to follow the Minnesota Power development in future years to witness how much hydropower makes up the renewables mix and how much power they import from outside their normal regional market.  In my experience having up to 20% variable wind is a real challenge for most Utilities to reasonably manage their power grid's balances and stabilities.  

John Miller's picture
John Miller on Mar 14, 2013

Ronald, thanks much for the informative references on biogas production.  I agree that dairies and cattle feedlots provide a niche opportunity for efficiently producing biogas that can be used to power heavy duty dairy trucks.  A unique benefit that the compressed methane biogas provides is the ability to displace petroleum diesel fuels normally required by heavy duty trucks.  Other apparently more popular biofuels, such as ethanol, normally are limited to displacing petroleum gasoline in lighter duty vehicles only.

Bob Meinetz's picture
Bob Meinetz on Mar 14, 2013

Ronald, I may have found something to agree with you on.

Biogas, as part of the biological carbon cycle, has no net effect on carbon concentrations over a time span of decades.

Natural gas from fracking is a completely different animal. It represents additional carbon which has been sequestered for millions of years, and is now being released into the ecosystem.

If we're going to take control of climate change recognizing these distinctions - and crafting policy around them - is critical.

Rick Engebretson's picture
Rick Engebretson on Mar 14, 2013

There are additional purposes for this food/energy infrastructure development.

First, health. Livestock, and the people who work with them, prefer not walking around in shit and piss, like urban consumers. Septic systems work, and produce "natural gas." So if you expect healthy food in the future, expect "natural gas," too.

Secondly, nutrient capture. The livestock stink is nitrogen that should be used for crop production. And treated waste is better fertilizer than untreated waste.

Modern dairy production is extremely sophisticated. On farm energy use includes hot water and refrigeration, with 24/7/365 electric power needs. Driving trucks using biogas might be a stretch. Selling reliable electric power is not.

But it takes time and money and labor to build this infrastructure. And the 1% that do it need to feed the 99% experts in the mean time.

Kind of like the useless ethanol discussion on TEC.


Jessee McBroom's picture
Jessee McBroom on Mar 14, 2013

Thank you for the article John. It looks like utulization of Natural Gas and Efficiency are out best options for the immediate future. This scenario then begs to question the long term sale of CNG or LNG to othewr countries with respect to our long term sustainability plans without some Cleaner and Far Less Expensive method of meeting our Energy Needs actually developed and in place to supplant the Natural Gas Producers would be selling on the open market. If the natural gas is to be such a critical component in our long term survival strategy as a Nation. I'm sure some sales would be beneficial ro developers; but vast as the deposits are; they are still limited resources. I do reccomend some strategy for supplanting the new found Bonanza In Natural Gas be the undoing of this plan if we do not anticipate global supply and demand and its' affect on this approach to emissions reduction. We can stretch these resrves further by hydrogen augmentation produced by 24/7 continuous operation systems such as Hydro Power and Geothermal. Intermittant Renewables may also be emploted to Generate Hydrogen in off demand hours. This would in essence allow for natural gas fueled Transportation and Industry Sectors to improve their Emissions Profile as well. I look dorward ro increased efficiencies in energy production as well as the increased efficiencies in energy consumption.

John Miller's picture
John Miller on Mar 14, 2013

Ronald, besides the issue of carbon emissions another factor that is not often discussed are the general environmental regulations of Europe and most of the world vs. the U.S.  The U.S. has some of the strictest environmental standards in the world.  That is why stack emissions in the EU, Russia, China, India, etc. contain far more SOX, NOX, CO, VOC and PM than the U.S.  The downside of weaker environmental standards is of course the negative health impacts on local populaces.

John Miller's picture
John Miller on Mar 14, 2013

Jessee, you raise some very important issues.  As with all other fossil fuels the total supplies of natural gas are ultimately limited.  The recent growths of shale gas and tight oil are due to innovative breakthroughs in gas & oil recovery technologies.  But even with these newly developed technologies, the available oil & gas reserves are still finite and will eventually be depleted.  In the mid-term the challenge is how do we stretch these limited natural energy resources to mitigate future supply shortage crises?  The obvious answer is reduced consumption through increased energy efficiency and developing new alternative energy sources or useful processes.  Your suggestion of producing hydrogen from variable renewable power sources is a very credible example.  Hydrogen can definitely be produced by electrolysis of water from renewable power when this source of electricity supply exceeds demand.  This alternative is effectively a very feasible option to storing electric power.  As you are probably aware this hydrogen energy cycle currently consumes much more energy than can be be produced from a hydrogen fuel cell.  This technology, however, could benefit significantly from further increased research to improve the water-hydrogen conversion process and the current state-of-art fuel cells efficiencies.  The possibilities and rewards could be quite substantial.

Jessee McBroom's picture
Jessee McBroom on Mar 14, 2013

Thank you John. As coinicidental data; the DOE Fuel Cells Technologies Office just released its' report today on blending hydrogen and natural gas just after I posted this remark. I received it in my email inbox; moments ago. You may find it of interest as well.

Leo Klisch's picture
Leo Klisch on Mar 14, 2013

Last year Iowa got 24.5% of there power from wind in the state.  Based on wikipedia info the average capacity factor calculates to 31%. They have 5137mw wind operating. If all were running to max on a particular day with average load the percent contribution of wind would be 79%. Given the peaks and valleys of daily load, I would think that there are many hours were wind output is equal to or greater than load. Iowa does export power so that's how they handle the high wind days. Now if the whole MISO region was at 24.5%, balance and stability could be a problem. But because the MISO region is big enough to have varying weather, it could allow a much higher percent wind. 

Ron Wagner's picture
Ron Wagner on Mar 14, 2013

Europe is in a very ironic and logically untenable situation. They need to fully develop biogas, shale gas, coal seam gas etc. Burning coal needs to cease, yet their policies are bonkers. Too much dependency on wind and solar has allowed us to beat them to cleaner air. We still need to close up a lot of old dirty coal plants too though. 

I really didn't know that their coal plants were not up to our emission standards. Can you give me a reference that compares them? Do you think that our modern coal plants need to be replaced with natural gas plants?

Ron Wagner's picture
Ron Wagner on Mar 14, 2013

Glad to here you approve of biogas. It is my favorite form of gas. I think that the potential volume should be mazimized with government requiring that all appropriate waste be used either as biogas, or recycled somehow, it it is economically possible. Packaging should also be minimized when possible IMHO. 

John Miller's picture
John Miller on Mar 14, 2013

Wind Smith, the 24.5% average renewable wind power penetration level puts the MISO region well above the average for the U.S. and most the world.  I’m not sure how much hydropower pumped storage is available in the region, but you probably know that during higher average wind velocity periods that this renewable power capacity could exceed demand.  That being the case means feathering or idling significant wind capacity during the oversupply periods.  If additional power storage were available this currently unusable wind capacity could be saved and used during low-no wind periods.  Beyond hydropower pumped storage, much more research and development is needed to make new, alternative industrial scale power storage a cost effective reality.

Pieter Siegers's picture
Pieter Siegers on Mar 14, 2013

John, although this is really a very interesting and detailed article which shows that progress has been made on various energy fields, in the long run however I do see a problem and that is simply the natural gas (and other fossil fuels) still do emit gases we do not want to increase over time.

I mean the good thing about energy management these days is the fact that closing coal mines and plants, replace coal with natural gas, and increasing efficiency to lower emissions is very very plausible, of course, but in the long run we will have to find a sustainable replacement, because although the emissions are decreasing nowadays, they will eventually go up again because of reaching a minimum and then as demand grows, the emissions will increase again.

So again I come as always to the same conclusion. We don't want any fossil fuel on the long run. We don't need them in the end. Renewables together with increased ability to store the energy captured from the sun - be it solar, wind or hydro - will be sufficient to all of our energy needs, now and in the future.

New product development around graphene is a very good example of what should be done to really change to a clean energy production, on the long run.


John Miller's picture
John Miller on Mar 14, 2013

Pieter, as you are aware the displacement of fossil fuels and associated carbon emissions is currently constrained by available technologies, energy conversion & consumption efficiencies, and costs.  Industrial scale power storage to supplement or add to current hydropower pumped storage will be key to this transition.  Your suggestion of developing ‘graphene’ materials and applications appears to definitely have many potentially valuable clean energy possibilities.  If graphene research and development successfully achieves upgrades in electronics, molecular sieves, solar PV, etc. we could see some real improvement in controlling electric power systems & utilization, improved solar power generation/reduced costs, more efficient purification of renewable biofuels/biogas/water desalination, and many other important energy related devices.

John Miller's picture
John Miller on Mar 14, 2013

Ronald, my personal experience with European environmental controls is primarily related to the Refining and Auto Industries.  Unlike the U.S. which has ‘fuel switched’ from higher sulfur residual (No.6) fuel oil to low sulfur natural gas years ago, the EU Industries still utilize huge volumes of No.6 fuel oil for heat, steam and power generation.  Their fixed stack emissions standards are similar to the U.S. environmental standards about 20+ years ago.  Most EU vehicles historically cannot meet U.S. tailpipe emission standards.  The use of diesel in the EU is also far greater than the U.S. and their diesel fuel spec’s are much looser than EPA required ultra low sulfur diesel (sulfur, aromatics, etc.) standards.  Similar differences are found with EU conventional gasoline vs. U.S. oxygenated RFG.  Unfortunately my data files on U.S. vs. EU (UK, Ireland, Germany, etc.) stack, mobile and fuel standards are hardcopy and not available on-line.

As far as coal, the UK made the largest change from coal power generation to North Sea natural gas some years ago.  Other EU countries did not or were not able to make this transition.  A most recent article I read covers the possible plans that many EU countries’ may further increase current coal power capacity in the near future.  To contrast EU vs. U.S. coal plant environmental controls I suggest comparing a recent EU standard summary vs. environmental standards found on the EPA website.  One of the largest differences between EU and U.S. regulations is ‘BAT’ (what the EU calls their regulatory strategy of requiring the ‘Best Available (Control) Technologies’; vs. the EPA that has increased past U.S. BACT standards to MACT (the ‘Maximum Available Control Technologies’).

As far as your last question, the EPA clearly has a regulatory strategy to shutdown increasing amounts of coal power generation capacity.  In the shorter term this capacity will need to be replaced with natural gas.  In the longer term I believe the U.S. will be required to possibly expand nuclear and renewable power to replace large amounts of existing baseload coal power.

Nathan Wilson's picture
Nathan Wilson on Mar 15, 2013

The natural gas export question brings up a sticky ethical dilemma.  If we (our government) restrict export, we'll maintain isolation between our gas market and the more expensive global market, thus holding our prices down (in addition to the pollution benefit).  On the other hand,   many developing countries have much dirtier and more dangerous coal industries, which would presumably loose market share if we increased the world supply of cheap natural gas (i.e. it would reduce pollution much more and save many more lives than burning the gas domestically).


On the question of blending hydrogen with natural gas:  remember that gaseous hydrogen has the worst volumetric energy density of any fuel!  For gaseous H2 to work as transportation fuel, it must be compressed to 10,000 psi (triple the pressure of cng), and used with a fuel cell (50% more efficient than an ICE, internal combustion engine).  Since cng at 3600 psi is already beyond the pain threshold, added hydrogen would be unacceptable.

Natural gas/H2 blends have been studied for direct heating applications (but only with low H2 concentration, like 5% by energy).  Still, with the poor storability of H2, it's hard to see this working out well.

A better way to store renewable energy on a seasonable basis would be to make ammonia (either from electolysis hydrogen, or using a reverse ammonia fuel cell).  Maybe too stinky for home heating, but fine as an industrial fuel, district heating, combined heat & power, etc.  Maybe even an automotive fuel some day.

John Miller's picture
John Miller on Mar 15, 2013

Nathan, as far as potential U.S. natural gas exports benefiting Developing countries carbon emissions that depends on whether this action truly displaces coal consumption or merely accelerates their overall fossil fuels consumption by providing a cost effective gaseous fuel that provides different opportunities to grow their economies.  Their existing infrastructures, energy mixes and government-business strategies will all affect the final outcome.

Blending hydrogen into natural gas presents a number of challenges and potential hazards.  Besides lowering the unit volume heating value as you have noted, the impact on the mixed fuel’s ‘flash point’ needs to be safely addressed (I suspect this may be the primary reason why studied blends you referenced were limited to 5% H2).  Use of neat hydrogen as an ICE motor fuel was studied in some detail back in the 1970’s-1980’s.  For a number of reasons the best option determined at the time was the use of fairly costly fuel cells vs. ICE options.  Are you aware of any more recent studies?

You appear to strongly advocate ammonia as a potential renewable energy source.  I’m curious, can you reference a recent full lifecycle ‘well-to-wheel’ or equivalent energy balance (hopefully from someone other than the Argonne National Lab.)?  Hydrogen production from water electrolysis has a very significantly negative ‘net energy value’ (NEV).  How does ammonia’s NEV compare?

Nathan Wilson's picture
Nathan Wilson on Mar 15, 2013

John, here is a reference from 2008 by Pate and Bartels that I recommend on ammonia as a fuel: 

I don't know of any recent H2-ICE work, but this paper argues that the difficulties and efficiency losses involved in transporting and storing H2 mean that ammonia will essentially always be cheaper at the retail point of sale.  Add in the fact that ammonia has more than double the energy density of 10,000 psi H2, and the only reason left to consider H2 is to show off hi-tech PEM fuel cells.

In terms of energy balance, of course it is worse than hydrogen at the factory gate, but better at the retail outlet (unlike hydrogen, ammonia can travel easily by truck, train, boat, etc; and can be stored in very large non-pressurized tanks with only minor refrigeration cost).  Converting H2 to ammonia (NH3) liberates 15% of the energy as high-grade heat, so with heat recovery, the process is about 90% efficient, which is about the same as compressing H2 and pumping it thru a short pipeline, and much better than liquefying it.

For making ammonia from natural gas, the only source I have is Argonne (what's the problem with them?).  ANL-339 says natural gas to H2 is 71.5% efficient; times 90% for NH3 conversion makes 64%, which beats Fischer-Trops diesel at 63%, but is slightly worse than methanol at 67%.

In terms of cost effectiveness of ammonia from renewable energy, of course in the US today it can't compete with ammonia from fossil fuel, but that is also true to a lesser extent of renewable electricity.  PV and solar, are more cost effective at displacing fossil fuel in electricity than fuel production, but at high penetration they can produce a lot of off-peak power which should sell at a discount.  Nuclear power is a somewhat cheaper way to make ammonia, particularly in countries like China that have low labor cost, and therefore low cost nuclear power.  For the near term though, ammonia is a way to use fossil fuels with carbon-capture for non-centralized applications.

Nathan Wilson's picture
Nathan Wilson on Mar 15, 2013

When we upgrade our home computers or other electronics, we usually get more features for the same cost.  Not so with grid updates.  A grid that can transfer power across the continent will cost much more than the current grid.  

NREL's 20% wind study from a few years ago assumed a new 765kV AC grid backbone.  This level of grid upgrade added 20% to the cost of wind power, yet only managed to carry wind power an average of 200 miles.  800kV HVDC systems have a lower cost per MW*mile, but a higher cost per mile; in other words, to get the higher performance of HVDC, the system is more expensive.

Still, this probably beats the cost of pumped-hydro storage.

John Miller's picture
John Miller on Mar 15, 2013

Nathan, thanks for the feedback.  It does not look like there have been any recent new breakthroughs in the production of ammonia.  Yes, ammonia has a higher heat density, but still is challenged by costs and supply chain economics as you noted.  Due to its corrosive properties ammonia presents new material spec. challenges for use as an ICE motor fuel, but hardly insurmountable.  My issue with Argonne’s GREET model is that a couple years ago when I was working a project to produce conventional ethanol, I found some of their data not reasonably representative of U.S. Refining.  One of the design constraints for new ethanol bio-refineries is compliance with the EISA 2007 20% GHG reduction standard compared to petroleum gasoline; full lifecycles.  Upon finding some significant errors in the GREET model I sent the ANL organization a more credible-accurate U.S. Refining commercial data source to help them correct the apparent errors and improve their model’s balances.  They showed no interest in improving their energy balances (and associated GHG errors).  I have lost confidence with their GREET model as a result and normally seek alternatives if available. 

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