Science Publishes “Net Zero Emissions” Paper, NH3 Seen in Prominent Role

Ammonia energy received prominent mention in a review article published in the June 29, 2018 edition of Science magazine.  Science is the flagship publication of the American Association for the Advancement of Science.  The paper, whose main body is almost 7,000 words long, is entitled “Net zero emissions energy systems.”  While the paper’s overall mission is to examine “the special challenges associated with an energy system that does not add any CO2 to the atmosphere,” the specific concerns that set it in motion relate to the idea that “energy services essential to modern civilization entail emissions that are likely to be more difficult to fully eliminate.”  The paper is a detailed investigation of technological solutions that can be applied in these areas.  Ammonia is highlighted as an “energy-dense liquid fuel” that could meet the needs of long-distance transportation services including aviation, long-distance trucking, and shipping.

Any paper published in Science is significant given the magazine’s stature and wide readership in the scientific community.  “Net zero emissions energy systems” is the more so because of who wrote it and how they came to the task.  The “who” is a group of 32 pedigreed individuals from a variety of universities, research laboratories, and other institutions clustered in California with outposts across the United States and as far away as the United Kingdom.

The “how” starts with a 1998 paper published in Nature by a group of 11 authors entitled “Energy implications of future stabilization of atmospheric CO2 content.”  The paper took on the challenge of quantifying the amount of “carbon-emission-free power” that would be needed “by the middle of the twenty-first century” to meet “atmospheric CO2-stabilization targets in the 750–350 p.p.m.v. range.”  (Atmospheric CO2 concentrations in September of that year were 364 ppm and by the end of 2017 had reached 405 ppm.)  The paper’s conclusion was a call to action: “The magnitude of the implied infrastructure transition suggests the need for massive investments in innovative energy research.”

The paper’s lead author was Martin Hoffert, Professor of Physics at New York University.  Second on the author list was Ken Caldeira, then a Physicist/Environmental Scientist at Lawrence Livermore National Laboratory and now a Senior Scientist at the Carnegie Institution for Science, both in the San Francisco Bay Area in California.

Among those who took note of the Hoffert-Caldeira paper in 1998 was Nate Lewis, Professor of Chemistry at the California Institute of Technology.  In an interview last week with Ammonia Energy, Lewis said that, having become acquainted with Caldeira over the years, he thought to contact him in 2016 with the twentieth anniversary of the paper’s publication looming, “Ken and I had the idea to try to convene a meeting of experts to see where we stand,” Lewis said.  It was clear that “a lot of turf had been covered by groups like the [U.S.] Department of Energy and the IPCC [Intergovernmental Panel on Climate Change] to get to 50 or 60% decarbonization.  But if the goal is zero carbon emissions, we wanted to know how difficult it would be to get there.”

The two men agreed that this was a matter that warranted more discussion and a larger set of stakeholders.  They invited another of the field’s practitioners, Steve Davis, Professor of Earth System Science at the University of California Irvine, into the effort, and the three set about compiling an invitation list for a possible conference.  Possibility became reality when the Aspen Global Change Institute (AGCI) agreed to serve as the event’s host.  AGCI is a non-governmental organization based in Colorado whose mission is to “facilitate critical scientific discussions on subjects in Earth systems science.”

Click to enlarge. “Difficult-to-eliminate emissions in current context.”  Figure 2 from “Net Zero Emissions Energy Systems.”  Science.  29 Jun 2018: Vol. 360, Issue 6396.

The “Getting Near Zero – Decarbonizing the Last 20%” workshop came to order on July 31, 2016 with about 30 invitees in attendance.  According to its contemporaneous purpose statement, the goal was “to assess the feasibility of decarbonizing the last, and most difficult-to-eliminate, portion of energy-related carbon dioxide emissions. The meeting will focus on the technical feasibility of economically achieving near-zero emissions from the energy sector. Challenges to eliminating these last emissions include (1) exploiting and integrating intermittent electricity resources to achieve high reliability via supply- and demand-based strategies, (2) decarbonizing transportation sectors not amenable to electrification (long-distance trucking, aviation, shipping, etc.), (3) decarbonizing heavy industries such as steel or cement manufacture, (4) possible scale up of nuclear and CCS, and/or (5) carbon dioxide removal from the atmosphere.”

While the meeting description was critical, mindset was also important, Lewis said.  “When we framed the meeting, we said, ‘no PowerPoints, no standard talks.’  We wanted diverse viewpoints and we didn’t want people dug into fixed positions.”

Lewis said one theme that recurred throughout the discussion was the need for balance between “development of disruptive technologies” and refining of existing technologies. The risk with the latter approach was lost time and sunk investment that may only yield “the first 60-80%” of the solution.  “If you do that,” he said, “how much harder do you make the second half of the journey?”

Another theme was the need for cross-sector integration.  For example, if a nuclear generating station were to be integrated with a hydrogen plant, the station’s output in the off-hours could be turned into fuel for the mobility sector.  “We did come to that insight,” Lewis said.  “It was a pretty new concept and method of framing a set of opportunities.”

The workshop adjourned on August 5, 2016.  Work on the distillation of conclusions started immediately, with Davis taking the lead with the first two drafts of the manuscript.  Workshop participants had been informed of the aspiration for widely shared authorship and the process of contributing and commenting that this would entail.  The daunting challenge of taking a group of this size through an editorial exercise of this nature was leavened by the “enthusiasm and consensus” that had formed around the findings, Lewis said.  Once a draft was in circulation, “there were some wording negotiations, to be sure, and a few red line issues for selected attendees.”  But the group “generally worked through the issues collegially and not adversarially or confrontationally to get to the final wording.”  When the process had run its course, he said, “we ended up keeping almost everyone on board.”

Eric Ingersoll attests that the manuscript went through “many, many drafts.”  Ingersoll is Managing Director of the consulting firm LucidCatalyst Inc. and co-founder of Energy Options Network, “an incubator created to multiply and accelerate the portfolio of zero carbon energy options available to tackle climate change.”  Ingersoll is number 20 on the alphabetized list of Science co-authors.  (Just above him is the lead author of the 1998 Nature paper, Martin Hoffert.)

In an interview with Ammonia Energy, Ingersoll recalled a long conversation at an earlier conference where he first met Lewis.  An entrepreneur with a background in compressed air energy storage (CAES), Ingersoll had delved deeply into the economics of hybrid CAES-wind-energy systems while exploring the feasibility of CAES for a number of large wind developers.  He had considered “ideas like large amounts of battery storage and massive buildouts of long-distance transmission” and concluded that they were “very unlikely” to pan out as solutions of choice.  On the hand, ammonia looked like it might be “ideally suited to serve as an energy storage medium, and would enable the use of existing installed gas turbine capacity to ‘firm’ wind and solar.”

Thus, when the discussion at the AGCI workshop turned to the need for energy-dense liquid fuels for aviation, long-distance transport, and shipping, Ingersoll suggested ammonia as one possible option. Ammonia seemed to fit with the workshop’s stated openness to “disruptive technologies,” and it lends itself to scenarios of cross-sector integration.  “Ammonia addresses so many of the profound difficulties we face when we try to imagine the full decarbonization of the energy system being accomplished in just a few decades, it just started to make more and more sense to the group,” Ingersoll said.

Once drafted, the paper included ammonia on the list of potentially relevant energy-dense liquid fuels, along with “the hydrocarbons we now use, as well as hydrogen, ammonia, and alcohols and ethers.”  In its consideration of ammonia, the paper mentions that as a fuel it “may be directly used in an engine or may be cracked to produce hydrogen.”  It also cites the need to “carefully control . . . its thermolysis . . . so as to minimize production of highly oxidized products such as NOx.”

The Science paper concludes with this paragraph:

A successful transition to a future net-zero emissions energy system is likely to depend on the availability of vast amounts of inexpensive, emissions-free electricity; mechanisms to quickly and cheaply balance large and uncertain time-varying differences between demand and electricity generation; electrified substitutes for most fuel-using devices; alternative materials and manufacturing processes including CCS for structural materials; and carbon-neutral fuels for the parts of the economy that are not easily electrified. The specific technologies that will be favored in future marketplaces are largely uncertain, but only a finite number of technology choices exist today for each functional role. To take appropriate actions in the near-term, it is imperative to clearly identify desired endpoints. If we want to achieve a robust, reliable, affordable, net-zero emissions energy system later this century, we must be researching, developing, demonstrating, and deploying those candidate technologies now.
Net Zero Emissions Energy Systems.”  Science.  29 Jun 2018:
Vol. 360, Issue 6396.

Click to enlarge. “Schematic of an integrated system that can provide essential energy services without adding any CO2 to the atmosphere.” Figure 1 from “Net Zero Emissions Energy Systems.”  Science.  29 Jun 2018: Vol. 360, Issue 6396.

The role of ammonia in this vision is clear to Ingersoll.  ”Ammonia could be really critical,” he said. “It enables us to use existing chemical processes and existing fossil fuels (assuming you have carbon capture on your ammonia plant) to make a fuel that can be stored more or less indefinitely and burned in highly dispatchable peaking power plants.  That’s a capability we really don’t have from any other source.  And then on the next level, we’re going to be able to use ammonia to collect energy and not just distribute and store energy.  If we can build the entry level use of ammonia in targeted applications, that will create a market for green ammonia so that, as costs come down and decarbonization requirements get tougher, we’ll be able to use it in more places, more of the time.”

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