Lithospheric Dripping Under the North American Craton Discovered with Seismic Full-Waveform Tomography

     New research published in Nature Geoscience based on seismic full-waveform tomography showing active cratonic thinning of the North American stable craton has been found to be consistent with the phenomenon of lithospheric dripping. The American Geophysical Union defines a craton as

“… a large, coherent domain of Earth's continental crust that has attained and maintained long-term stability, having undergone little internal deformation, except perhaps near its margins due to interaction with neighbouring terranes.”

Cratons are tectonic plates that are the most stable away from their margins. Typically, they are very old Precambrian-aged granite-greenstone terrains. Once the density, composition, and thermal properties become stable, the crust is considered a craton. There are about 35 cratons identified around the world. The current study considers the craton known as the North American plate under which the Farallon plate began subducting around 180 million years ago.

Lithospheric dripping involves the interaction between the earth’s crust and the deeper mantle. It occurs when the underside of Earth's rocky crust is heated to a threshold temperature where it the underside of the crust starts to melt and eventually forms a “drip” that eventually breaks off and falls deeper into the planet. A 2D cross-section of the dripping under the North American craton is shown below.

     The Farallon plate, a very old oceanic plate, is almost entirely subducted under the North American plate. The Farallon plate began as a mid-ocean ridge around 180 million years ago, the basic time it takes for an oceanic plate to complete its cycle of subducting under a continental plate, as I learned in geology classes.

     According to Wikipedia, seismic tomography can be used to image the subducted plate as long as it has not achieved thermal equilibrium with the mantle.

“Seismic tomography can be used to image the remainder of the subducted plate because it is still "cold," meaning that it has not reached thermal equilibrium with the mantle. This is important for the use of tomography because seismic waves have different velocities in materials of different temperatures, so the Farallon slab appears as a velocity anomaly on the tomography model.”

     The dripping is causing lithospheric thinning under the craton. The dripping is concentrated over the U.S. Midwest. The following figures show the changes from millions of years ago (at least 30, I can’t tell fully since Nature likes to make it so you can’t see figures) compared to the present.

     The abstract of the paper, Seismic full-waveform tomography of active cratonic thinning beneath North America consistent with slab-induced dripping, is shown below.

Abstract

Continental cratons are characterized by thick lithospheric roots that remain intact for billions of years. However, some cratonic roots appear to have been thinned or completely removed in the geological past. The mechanisms for thinning have been difficult to distinguish for these past events. Here we present a full-waveform seismic tomographic model for North America that allows the resolution of fine-scale structures and reveals an extensive craton-thinning event that is ongoing. The seismic images show extensive drip-like features that suggest the transport of lithospheric materials from the base of the craton beneath the central United States to the mantle transition zone, and thus active lithospheric thinning. Geodynamic modelling suggests that the dripping may be mobilized by large-scale mantle flow induced by the sinking of the Farallon slab that is currently in the lower mantle. Dripping lithosphere could be further facilitated by prior lithospheric weakening, for example by volatiles released from the slab. Our seismological observations of active extensive thinning of cratonic lithosphere support lithospheric removal could be a result of external mantle processes, which we hypothesize may include the deep mantle effects of subduction.

     Thorsten Becker, a professor at the University of Texas at Austin’s Jackson School of Geosciences Department of Earth and Planetary Sciences and Institute for Geophysics noted:

“This sort of thing is important if we want to understand how a planet has evolved over a long time. It helps us understand how do you make continents, how do you break them, and how do you recycle them [into the Earth.]”

 

 

References:

 

Earth’s Crust is Dripping Under Midwest US, Scientists Discover. Michelle Starr. Science Alert. April 2, 2025. Earth's Crust Is Dripping Under Midwest US, Scientists Discover

Seismic full-waveform tomography of active cratonic thinning beneath North America consistent with slab-induced dripping. Junlin Hua, Stephen P. Grand, Thorsten W. Becker, Helen A. Janiszewski, Chujie Liu, Daniel T. Trugman & Hejun Zhu. Nature Geoscience (2025). Seismic full-waveform tomography of active cratonic thinning beneath North America consistent with slab-induced dripping | Nature Geoscience

North America is Dripping from Below, Geoscientists Discover. Texas Geosciences. University of Texas at Austin. April 1, 2025. North America is Dripping from Below, Geoscientists Discover | Jackson School of Geosciences | The University of Texas at Austin

Farallon plate. Wikipedia. Farallon plate - Wikipedia

North American plate. Wikipedia. North American plate - Wikipedia

What is a craton? How many are there? How do they relate? And how did they form? Bleeker, W. ; Davis, B. W. American Geophysical Union, Spring Meeting, May 2004. What is a craton? How many are there? How do they relate? And how did they form? - Astrophysics Data System

Contamination from Waste-to-Energy Facilities (Incinerators): New Studies in Europe Show High Dioxin, PFAS, and Heavy Metals Levels in Soil, Water, Vegetation, and Food

     I had assumed that WTE facilities in Europe, especially the more advanced ones, had adequate pollution abatement systems. A series of new independent studies in France, Spain, and the Netherlands suggests that the systems are not adequate. The studies were conducted by ToxicoWatch Foundation with support from Zero Waste Europe. Global Data reports that:

“Dioxin concentrations in soil, moss, and backyard chicken eggs exceeded EU safety limits at all three locations.”

“In Paris’ Ivry-sur-Seine district, a schoolyard playground was found to contain contamination levels exceeding legal thresholds. In Harlingen, PFAS levels in water reached 138 times the Dutch legal limit for drinking water.”

“Meanwhile, in Zubieta, a backyard egg sample from Hernani recorded the highest dioxin concentration measured by the ToxicoWatch Foundation in over a decade.”

“Heavy metals such as lead, mercury, and arsenic were also found in areas close to homes, parks, and schools. The presence of these hazardous substances in public spaces raises concerns about long-term exposure, particularly for vulnerable groups such as children.”

At one sight they found that dioxin levels in soil had increased sevenfold since 2013.

“The Zubieta incinerator, which became operational in 2020, showed significant environmental pollution. Moss samples contained dioxin levels up to 300 times higher than baseline measurements taken before the plant began operating.”

    Thus, we can see that this pollution is coming from new modern facilities. This is concerning. Based on these studies there are new calls for more monitoring and regulations. Zero Waste Europe is advocating for real-time monitoring of persistent organic pollutants (POPs) from WTE plants, particularly during non-standard operations, which are often linked to emission spikes. Due to its presence in consumed food, they also want to implement regular biomonitoring in affected areas.

     The ongoing debate between landfilling and WTE might be affected by these studies. Both can be highly polluting, but WTE pollution seems to get into the environment and in foods and human bodies much faster. This is certainly a serious public health concern.

     The conclusions from the 2024 interim report of the areas around the WTE plant at Zubetia, Spain are given below.

     “The findings of this interim biomonitoring study (2024), conducted in the region surrounding the Zubieta incinerator, reveal exceedances of dioxins, perfluoroalkyl substances (PFAS), and heavy metals in the environment. 

     The results from backyard chicken eggs analysed using the DR CALUX bioassay show a significant increase in dioxins, including PCDD/Fs and dioxin-like PCBs (dl-PCBs). At Hernani, located 3,500 metres east of the waste incinerator, the highest dioxin concentration ever recorded in backyard chicken eggs during 13 years of TW biomonitoring across Europe was measured. 

     At Zubieta Press Site - where this five-year study began in 2019 with zero-measurements - a clear upward trend in dioxin levels is evident since the start of the waste incinerator's operations in 2020.  PFAS were detected in all examined backyard chicken eggs. In Hernani and Andoain, PFAS concentrations exceed the EU’s maximum permissible limits.  In 2024, PFAS were also detected in a drinking water source located on a hill near Andoain, an area previously considered pristine. 

     In 2019, no dioxins were found in mosses (Bryophytes) or pine needles (Pinus radiata). In the years that followed, dioxin levels in the moss increased by up to a factor of 300. Although levels have since decreased, PCDD/F concentrations in mosses remain 30 times higher than in 2019, prior to the incinerator’s operation. 

     Rising trends in heavy metals were also observed in water, soil, mosses, and sediment. In water samples, elevated concentrations of zinc (Zn) and lead (Pb) were detected. In soil, increases in cadmium (Cd), silver (Ag), manganese (Mn) and mercury (Hg) were noted.  In moss, elevated levels of arsenic (As), barium (Ba), nickel (Ni) and tin (Sn) were observed. In sediment, the presence of cobalt (Co) and manganese (Mn) was remarkable.

     The contamination by Substances of Very High Concern (SVHC) such as dioxins, PFAS and heavy metals – is not limited to eggs or moss but reflect a broader issue of persistent organic pollutant (POP_ deposition in the environment of Zubieta. This rising pollution trend underscores the urgent need for a thorough investigation into the semi-continuous flue gas measurement data from the Zubieta incinerator. Such an investigation is essential to determine whether the facility complies with legal obligations to eliminate or at least minimise emissions of hazardous substances - including dioxins (PCDD/F/dl-PCB), heavy metals and PFAS - into the environment.”

 

  

 

References:

 

European incinerators linked to dioxin and PFAS pollution. Mohamed Dabo. Global Data. April 1, 2025. European incinerators linked to dioxin and PFAS pollution

ToxicoWatch Foundation. ToxicoWatch | Toxicology

Biomonitoring research on persistent organic pollutants (POPs) in the surrounding environment of the WtE waste incinerator in Zubieta 2024. Interim report. ToxicoWatch. 8b2c54_cb08f19250ee4ef89ae354aab2eb1e51.pdf

Greenhouse Gas Releases from Exposed Groundwater Discharged During Low Stream Flow Conditions: New Research Quantifies Releases

     New research shows that seeping groundwater can be a significant source of greenhouse gases, including CO2, methane, and nitrous oxide (N2O). Groundwater flowing through sediment and rock near rivers accumulates carbon and nitrogen. Past research showed that groundwater connected to rivers usually mixes with the river water, limiting gas releases. However, during low-flow conditions, groundwater can seep out along stream banks at or above the river surface.

     The research involved measuring greenhouse gas emissions along riverbanks at three locations in the Farmington River watershed in Connecticut and Massachusetts, focusing on areas above the water level during the summer flow season. The research team utilized handheld infrared cameras to identify streambanks with exposed groundwater discharges, or seeps. They then measured changes in the concentrations of CO2, methane, and N2O, as well as discharge rates. They also collected groundwater samples and analyzed them for concentrations of dissolved carbon, oxygen, and nitrogen.

     The abstract from the paper in the March 2025 issue of American Geophysical Union’s JGR Biogeosciences, Preferential Groundwater Discharges Along Stream Corridors Are Disregarded Sources of Greenhouse Gases, is given below.

 

Abstract

Groundwater delivery of greenhouse gases (GHGs) to stream banks and riparian areas, before mixing with surface waters, has not been well quantified. We measured preferential groundwater delivery of GHGs to stream banks within three stream reaches, and found that stream banks with discharging groundwater emitted more CO2 and were sources of N2O compared to stream banks without actively discharging groundwater, which emitted less CO2 and were N2O sinks. At one of our stream reaches, groundwater CO2 and N2O concentrations were 1.4–19.2 and 1.1–40.6 times higher than those in surface water, respectively, and groundwater delivery rates of CO2 and N2O were 1.5 and 1.6 times higher than surface water emissions per unit area. On average, 21% (range 0%–100%) of CO2 and N2O were emitted at the stream bank before mixing with surface waters. Preferential groundwater GHG emissions may contribute substantially to stream corridor emissions and may be underestimated when using a channel-centric approach to estimate riverine GHG budgets.

     The researchers noted that estimates of riverine greenhouse gas emissions should be updated to account for these above-water-level groundwater seeps.

“Overall, our results indicate that groundwater discharge occurring along stream banks has the potential to contribute greatly to river GHG emissions and is unaccounted for in current approaches that measure GHG emissions from surface water channels.”

 

Key Points

·        Stream banks with actively discharging groundwater acted as localized N2O sources, while adjacent nondischarging stream banks acted as sinks

·        On average, 21% of groundwater discharge CO2 and N2O are emitted from the stream bank before mixing with surface water

·        Preferential groundwater discharges have higher concentrations and areal delivery rates of CO2 and N2O than adjacent surface water

  

 

References:

 

Seeping groundwater can be a hidden source of greenhouse gases. Sarah Derouin. Phys.org. March 31, 2025. Seeping groundwater can be a hidden source of greenhouse gases

Alaina M. Bisson et al, Preferential Groundwater Discharges Along Stream Corridors Are Disregarded Sources of Greenhouse Gases, Journal of Geophysical Research: Biogeosciences (2025). Preferential Groundwater Discharges Along Stream Corridors Are Disregarded Sources of Greenhouse Gases

 

Corporate Conservation Projects and Environmental Benefits Trading: Credits, Budgets, Planning, Challenges, and New Opportunities

 

     There are many global environmental problems that need solutions. These include the effects of climate change and extreme weather, wastewater pollution, sewage, solid waste disposal problems, deforestation, lack of access to clean cooking fuels, contaminated industrial sites, agricultural issues like fertilizer runoff and soil erosion, wells leaking oil, saltwater, and methane, and biodiversity loss. Mitigating and reversing some of these issues yields quantifiable environmental benefits, including greenhouse gas emissions reduction benefits. The value of those benefits is agreed upon in various carbon trading systems. The same is sometimes done in various “green trading” schemes, such as air pollution emissions trading, which can also be referred to as environmental benefits trading. Corporations are well known for purchasing ‘carbon offsets’ to offset their emissions by investing in carbon emissions reduction projects.

     Conservation consulting companies such as the Wildlife Habitat Council, which recently merged with the World Environment Center to become Tandem Global, advise corporate clients on conservation projects. The CEO Margaret O’Gorman published a book in 2020, Strategic Corporate Conservation Planning: A Guide to Meaningful Engagement. A section from the description is below:

“Leading corporations have begun to leverage nature-based remediation, restoration, and enhanced lands management to meet a variety of business needs, such as increasing employee engagement and establishing key performance indicators for reporting and disclosures.”

“With limited government funding available for conservation and increasing competition for grant support, corporate efforts can fill a growing need for environmental stewardship while also providing business benefits. Strategic Corporate Conservation Planning presents a comprehensive approach for effective engagement between the public and private sector, encouraging pragmatic partnerships that benefit us all.”

 

Less Focus on Tackling Environmental and Social Risks in 2024

     With ESG efforts declining in the U.S. especially, there is probably less focus on conservation projects in general. One group found that interest has dropped significantly over the last few years. According to an article in the Evening Standard:

“Proposals aimed at tackling environmental and social risks saw record-low support from asset managers at shareholder meetings last year, according to an analysis.”

“ShareAction, which campaigns for responsible investment, found that only 1.4% – four of the 279 shareholder resolutions it assessed – received majority support in 2024, down from 21% in 2021.”

“ShareAction’s annual Voting Matters report, released on Tuesday, found that four of the world’s largest asset managers – BlackRock, Fidelity Investments, State Street Global Advisors and Vanguard – voted against shareholder proposals aimed at protecting human rights, nature and climate last year.”

Thus, it seems that the asset managers are voting more and more against such proposals. Most denial of such proposals came from the U.S. However, asset managers like BlackRock justified voting against them, saying some were too costly for the benefits provided. Overreach was also mentioned.

“For the 2024 proxy year, we found that most environmental and social shareholder proposals were overreaching, lacked economic merit, or were unlikely to promote long-term shareholder value,” they {BlackRock} said.”

 

Green Trading/Environmental Benefits Trading

     According to Tio Markets:

“Green trading is an increasingly popular approach to investing that emphasizes environmental sustainability and social responsibility. It is a form of trading that takes into account the environmental impact of the companies and industries being invested in, with a focus on promoting green technologies and sustainable practices.”

Green trading is also known as environmental trading or eco-trading. These markets rely on quantifying environmental benefits. Green trading began as mutual fund investments that screened out projects that did not meet certain environmental criteria, similar to what is known as socially responsible investing, in this case environmentally responsible investing. Corporate transparency and disclosure are required for companies in these markets. Now, there are many types of green trading including green stocks, green bonds, environmental commodities, and green mutual funds. Green stocks mean investing in green companies such as renewable energy developers. Green bonds are specifically designed to finance environmental projects. New regulations and corporate support aid environmental benefits trading and investment by encouraging it. New technologies to measure and monitor those benefits improve accountability and transparency.  

 

Nature-Based Economic Policies

     International organizations like the UN and the World Bank have encouraged nature-based economic policies to stem the loss of biodiversity and ecosystem services. The World Bank points out that low-income countries stand to lose the most in ecosystem service collapse. Their argument given in the 2021 report The Economic Case for Nature is that focusing on these matters will result in both natural and financial rewards compared to not acting. They have focused on the 30x30 goal, the need to protect 30 percent of the planet for nature by 2030. 

     According to the Business for Nature website:

“Business for Nature, The World Economic Forum and The World Business Council for Sustainable Development have developed guidance for 14 sectors that build on the high-level actions businesses should take to credibly help halt and reverse nature loss and contribute to an equitable, nature-positive economy.”

These sectors include agri-food, automotive, built environment, cement and concrete, energy, fashion and apparel, financial services, forest products, household and personal care, mining and metals, pharmaceuticals, travel and tourism, waste management, and water utilities and services. They have a workflow to assess, commit, transform, and disclose. Examples from the agri-food and built environment sectors are shown below.

     They note that many governments adopted the Global Diversity Framework in December 2022. This was developed by the UN’s Convention on Biological Diversity and is related to the UN’s sustainable development goals. The UN describes the Global Diversity Framework as

“…an enhanced mechanism for planning, monitoring, reporting and reviewing implementation, the necessary financial resources for implementation, strategic frameworks for capacity development and technical and scientific cooperation, as well as an agreement on digital sequence information on genetic resources.”

     The World Economic Forum’s 2020 report The Future of Nature and Business focused on ecosystem restoration and avoided land and ocean use, agriculture, forests, consumption, supply chains, the built environment, urban utilities, circularity, metals and minerals, and sustainable materials.

 

Corporate Environmental Science and Collaboration with Government Agencies: ConocoPhillips as a Case Study

     Energy companies and other companies with high levels of Scope 3 emissions are scrutinized more than others and expected to accurately report and address those emissions. Many of these companies are involved in collaborative studies and projects with government agencies and are addressing their environmental and biodiversity impacts as well as their greenhouse gas emissions.

     Another way corporate conservation projects can be useful is in conducting scientific studies to determine the environmental and biodiversity impacts of a company’s infrastructure. Oil & gas company ConocoPhillips has several examples of this on their website. In some cases, a better understanding was developed of the actual risks vs, the perceived risks of company operations. ConocoPhillips studied the nesting, brood-rearing, habitat types, and local migration patterns of sharp-tailed grouse in North Dakota. They can utilize that knowledge to minimize their impact on the grouse. They have other similar projects as well. The company also utilizes formal agreements with the U.S. Fish & Wildlife Service and/or other federal or state agencies that include stipulations governing the timing of certain development activities within specific species habitats or sensitive areas.

     ConocoPhillips has what they call a mitigation hierarchy that includes four types of biodiversity and environmental impact mitigation: avoid, minimize, restore, and offset. The above-mentioned grouse project is an example of avoiding impacts. How they minimize impact is explained below:

“We minimize biodiversity impacts through measures taken to reduce the duration, intensity and/or extent of the footprint of our operations. New drilling technology, data analytics techniques and integrated planning have helped to optimize and reduce our infrastructure footprint and improve reservoir development efficiency through multi-well pads, longer lateral wells, multi-lateral wells, tankless pads and central facilities.”

     Restoration is through reclaiming and remediation of impacted lands and habitats. They note projects involving reclaiming gravel mines (used for toads and well pads) and others involving regional habitat restoration. They have also conducted surveys to measure impacts and are involved in other stewardship projects including seeding native species, controlling invasive species, and fencing.

     Where disturbance can’t be mitigated, they can utilize offsets. They have an internal Biodiversity Offset Guideline to evaluate offsets, whether to meet regulatory requirements or as a strategic business preference.

 

 

References:

 

Long-time conservation strategist to lead new nature nonprofit: Margaret O’Gorman will lead Tandem Global, created through the merger of Wildlife Habitat Council and World Environment Center. Heather Clancy. Trellis. February 11, 2025. Long-time conservation strategist to lead new nature nonprofit | Trellis

Sector actions towards a nature-positive future. Business for Nature. Business For Nature

The Future Of Nature And Business. New Nature Economy Report II. In collaboration with AlphaBeta. World Economic Forum. 2020. WEF_The_Future_Of_Nature_And_Business_2020.pdf

The Economic Case for Nature: A global Earth-economy model to assess development policy pathways. The World Bank. 2021. World Bank Document

Plans to tackle environmental risks ‘got record-low support from asset managers’.  Rebecca Speare-Cole. Evening Standard. February 17, 2025. Plans to tackle environmental risks ‘got record-low support from asset managers’

Green trading: Explained. TIO Staff. TIO Markets. July 27, 2024. Green trading: Explained

Managing biodiversity – related risks and impacts. ConocoPhillips. Managing biodiversity-related risks and impacts | ConocoPhillips

Strategic Corporate Conservation Planning: A Guide to Meaningful Engagement. February 6, 2020. Margaret O'Gorman. (Amazon book description). Strategic Corporate Conservation Planning: A Guide to Meaningful Engagement: O'Gorman, Margaret: 9781610919401: Amazon.com: Books

Kunming-Montreal Global Diversity Framework. U.N. Convention on Biological Diversity. Kunming-Montreal Global Biodiversity Framework

Plans to tackle environmental risks ‘got record-low support from asset managers’. Rebecca Speare-Cole. Evening Standard. February 17, 2025. Plans to tackle environmental risks ‘got record-low support from asset managers’

U.S. Government Declares Tax War on Rest of World: Fair Trade vs. Chaotic Economic Nationalism

    Trump’s ‘Day of Liberation’ is upon us. Everyone stands to lose, according to the vast majority of economists. It is a risky experiment. It has alienated most of our “friends” who no longer seem like friends. I have nothing against reciprocal tariffs since they can level the playing field and make trade more fair, but these punitive tariffs are nuts. Trump has championed the use of tariffs as a threat, mostly to allies. The level of disruption from this tariff war seems to already be high. The stock market has not been doing well. Prices at the grocery store are already rising again. Both of these hit me hard. The mood is one of doom. This isn't some carefully crafted plan by shrewd economists, it's a chaotic leverage play by a leader not well-versed in economics and non-mainstream economic advisors.   

“The Federal Reserve told us that inflation was transitory in 2021. They were wrong. Very wrong. In 2022, they ate crow and embarked on the most hawkish monetary policy since Fed Chair Paul Volcker broke inflation back in the 1980s.”

“Higher interest rates successfully wrestled inflation down below 3% from 8% in 2022, allowing the Fed to switch gears to rate cuts last fall. However, prices have been creeping higher, putting pressure on already cash-strapped consumers.”

“A total of 172,017 people lost their jobs in February, according to Challenger, Gray & Christmas, the most in the month of February since 2009.”

     Jim Cramer thinks the effects of these widespread tariffs will be “horrendous.” These notions, which were pushed by Howard Lutnick, Peter Navarro, and others, about tariffs leading to prosperity and the notion of an External Revenue Service, are bunk. International trade is about to be disrupted in a big way. If I had more money, I would buy some things before they kick in. I don’t understand the usefulness of punishing our best trade partners, Canada and Mexico. This level of reorganization of international trade orchestrated by a few extremely wealthy men seems to have few upsides. Sure, some sectors will benefit but others will be hurt, some badly.

     Fair trade is a worthy goal. As economists well know, trade imbalances generally do not reflect fairness. Free trade is also a worthy goal, one that benefits all countries involved. Using tariff threats as leverage is not generally recognized as a useful action. Tariffs are the same thing as import taxes. There is no difference. Retaliation will involve both reciprocation of rates and searching for new buyers, and new markets for products. The level of disruption won’t be small. With increasing inflation, rising unemployment, and a high level of market uncertainty, it seems unlikely that things will get better soon unless he abandons the big tariffs. It also seems unlikely that he will do that since it would admit defeat. Free trade is one of the things that made the world prosperous. To take that away is just not smart.

      JP Morgan Chase CEO Jamie Dimon, when asked about tariffs, said “Uncertainty is not a good thing.” Stagflation and recession are very real possibilities. Dimon thinks the effects on businesses will be worse than the effects on consumers. The 25% tariff on all steel and aluminum imports is not looking good for American workers.

“Alcoa CEO William Oplinger has said that tariffs could mean 100,000 Americans lose their jobs, including 20,000 aluminum industry workers, given that 58% of aluminum imports are produced in Canada.”

     Many American industries rely on affordable imported steel and aluminum. The oil & gas industry is one that relies heavily on imported steel. While onshoring steel production and other manufacturing has its merits, low cost is not one of them due to higher U.S. labor costs. U.S. oil and gas CEOs recently cast doubt about tariffs in an anonymous survey.  As I noted in my previous post about tariffs: “nobody wins with a headbutt.”

  

    

      

 

References:

 

Jim Cramer offers blunt one-word reaction to 20% tariffs. Todd Campbell. The Street. April 2, 2025. Jim Cramer offers blunt one-word reaction to 20% tariffs

Jamie Dimon sends curt 6-word response to tariff war. Todd Campbell. THe Street. March 13, 2025. Jamie Dimon sends curt 6-word response to tariff war - TheStreet

 

Thermoradiative Diode Technology: Applications, Projects, and Possibilities of Mid-Infrared Radiative Heat for Power

  The concept of a thermoradiative cell to harvest energy from infrared radiation to the thermal sink of deep space was first described in 2014-2015. A thermoradiative cell is basically a photovoltaic cell that is run in the thermodynamically reversed direction. According to Geoffrey A. Landis of NASA’s John Glenn Research Center (2022):

“It is based on the concept that an ideal photovoltaic cell is a heat engine, operating on a temperature difference between photons (e.g., from the sun) as a high temperature source, and the external environment as a low temperature sink. Since an ideal heat engine will operate when the high and low temperature sides of the engine were reversed, Strandberg showed that a device identical in structure to a photovoltaic cell would operate with sources reversed. Thus, the thermoradiative cell has heat as the energy input and photons as the waste heat output (figure 1). The cells radiate heat to a lower temperature, which he assumed to be the low temperature of deep space.”

“A photovoltaic cell absorbs light and produces electrical power. In the process, of course, since thermodynamics demands that no energy converter can be a hundred percent efficient, it also produces waste heat. We can therefore think of a solar cell as a thermodynamic heat engine that converts sunlight (at an effective temperature of 6000 K, the temperature of the sun) into electrical power, and rejecting waste heat on the “cold” side, typically at room temperature, around 300 K. But, thermodynamically, a heat engine is reversable: if you switch the hot side and the cold site, it will still produce power. Thermodynamically, then, it should be possible to heat the photovoltaic device, to make it emit (infrared) light, and in the process produce electrical power. The concept sounds absurd [5]; but nevertheless it is based on sound physical principles.”

     This technology can be used for terrestrial energy, converting waste heat into energy, and for converting heat from isotope or nuclear power sources to electricity for spacecraft. Its use in space is deemed the most promising due to the presence of the heat sink of deep space. Using these devices on planet surfaces will result in significant efficiency losses. However, they can be used on moons or asteroids without atmospheres. Thermoradiative arrays can operate at high heat source temperatures between 300K and 1000-1500K. They are high-temp, low band gap vs. solar PV cells which are low-temp, high band gap. A thermoradiative device consists of a p-n diode, where its surface area is open to space (or, generally, any cold-temperature radiative heat sink). Like PV cells thermoradiative cells have no moving parts. Below is a list of research needs for this immature technology. Thermoradiative conversion may become as good as or better than thermoelectric and thermophotovoltaic conversion.

     Thermoradiative diodes emit photons in the mid-infrared range of the spectrum. This emitted infrared energy can produce electricity. Here on Earth the applications would be very limited to small power needs like charging small devices with low power needs. Diodes made of mercury cadmium telluride (HgCdTe) have been tested for such uses. Another potential application is supplemental power for satellites in low-Earth orbit, which typically cycles between 45 minutes of sun exposure and 45 minutes of darkness. In terms of understanding physics, thermoradiative technology fills in a gap in our knowledge:

“In plots of current against voltage for optoelectronic devices, light-emitting diodes (LEDs) occupy the first quadrant (positive voltage; positive current), solar cells the second (positive voltage; negative current), and light detectors the third (negative voltage; negative current). But the fourth quadrant (negative voltage; positive current) is empty. That’s where thermoradiative diodes will fit in.”

     As I understand it, the early experiments only produced a small amount of power barely detectable, and with a very low efficiency of about 1.8%. However, researchers think they can get it closer to theoretical limits which can mean that it can be used to produce about 10% of the power of an equivalent solar PV cell, or basically a 10% power increase. That is not much on Earth but it can be significant in space.

     A December 2024 paper in Nature evaluated the power outputs of thermoradiative diodes under different terrestrial atmospheric conditions. They concluded that the power output varies with humidity, but the ideal bandgap remains around 0.094 eV.

    

 

References:

 

The ‘solar cells in reverse’ that can generate power at night. Nature Portfolio. The ‘solar cells in reverse’ that can generate power at night

Evaluating potential power output of terrestrial thermoradiative diodes with atmospheric modeling. Jamie A. Harrison, Phoebe M. Pearce, Fei Yang, Michael P. Nielsen, Helen E. Brindley, and Nicholas J. Ekins-Daukes. iScience. Volume 27, Issue 12, 20 December 2024, 111346. Evaluating potential power output of terrestrial thermoradiative diodes with atmospheric modeling - ScienceDirect

Semiconductor thermoradiative power conversion. Michael P. Nielsen, Andreas Pusch, Phoebe M. Pearce, Muhammad H. Sazzad, Peter J. Reece, Martin A. Green & Nicholas J. Ekins-Daukes. Nature Photonics volume 18, pages1137–1146 (2024). Semiconductor thermoradiative power conversion | Nature Photonics

Thermoradiative Power Conversion from HgCdTe Photodiodes and Their Current–Voltage Characteristics. Michael P. Nielsen, Andreas Pusch, Muhammad H. Sazzad, Phoebe M. Pearce, Peter J. Reece, and Nicholas J. Ekins-Daukes. ACS Photonics. Vol 9. Issue 5. May 9, 2022. Thermoradiative Power Conversion from HgCdTe Photodiodes and Their Current–Voltage Characteristics | ACS Photonics

Harvesting renewable energy from Earth’s mid-infrared emissions. Steven J. Byrnes, Romain Blanchard, and Federico Capasso. PNAS. February 3, 2014. Harvesting renewable energy from Earth’s mid-infrared emissions | PNAS

Thermoradiative Arrays: a New Technology for Conversion of Heat into Electrical Power. Geoffrey A. Landis. NASA. 2022. Thermoradiative arrays

Bizarre night-time solar cell generates power in a backwards process. Loz Blain. New Atlas. May 18, 2022. Bizarre night-time solar cell generates power in a backwards process