aaqr.org/VOL14_No2_March2014/8_AAQR-13-09-OA-0283_533-549.pdf

Is truth sometimes stranger than fiction?

Believe it or not, the United States Environmental Protection Agency has recently begun to recommend the solar-powered, or other renewable energy-driven, conversion of Carbon Dioxide, as recovered from whatever handy source, into hydrocarbon fuels; that, following research funded in part by, and performed in partnership with, the Consortium for Clean Coal Utilization (CCCU) at Washington University in St. Louis, Missouri.

And, three primary members and sponsors of the CCCU, as can be learned via:

Consortium for Clean Coal Utilization; "Established in December 2008, the Consortium for Clean Coal Utilization is a center for research in advanced coal and carbon capture technologies. The goal of the consortium is to foster the utilization of coal as a safe and affordable source of energy, and as a chemical feedstock, with minimal impact on the environment. The Consortium operates under the umbrella of the International Center for Advanced Renewable Energy and Sustainability, which Washington University established in June 2007 to encourage and coordinate University-wide and external collaborative research on energy, environment, and sustainability. The establishment of the Consortium was made possible through commitments from the lead sponsors: Arch Coal, Peabody Energy, and Ameren. Funding goes to support a variety of research projects, advanced research facilities, and outreach activities relating to the clean utilization of coal. The research projects are led by faculty at Washington University, and performed in collaboration with faculty from the international partner universities";

are the major Coal mining companies Arch Coal and Peabody Energy, and, the multi-state electricity provider, Ameren.

(https://www.ameren.com/-/media/corporate-site/Files/AboutAmeren/AmerenCorporateFactSheet.pdf).

Unfortunately, news of the US EPA's changing views about Carbon Dioxide were published, not in the United States of America, but, seriously, in China.

Actually the news was published in Taiwan, on the island historically known as Formosa, and more recently as the Republic of China - a once staunch ally of ours which the USA sort of cravenly turned it's back on some years ago, in a kowtow to the Peoples Republic of, i.e.,Red, China.

The details are exposed in, as excerpted from the link:

"'Comparison of CO2 Photoreduction Systems: A Review';

Aerosol and Air Quality Research; 2014; Copyright Taiwan Association for Aerosol Research

(by) Wei-Ning Wang, et. al.; Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO, USA (and) Office of Research and Development, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH, USA

(NOTE: Since this piece was written, in part, by the US EPA, it does contain some of the usual and expected boilerplate genuflections to global warming hysteria and the role CO2 emissions from human industry might play in it. Interestingly, though, they don't single out Coal-based power generation as a culprit, but do catalogue instead a list of various CO2-emitting industries. It might be unrealistic to expect, that, since the EPA has beaten the Coal-CO2-Global Warming drum for so long, they would completely surrender the issue in abject capitualtion. One must suppose that they are motivated to attempt maintaining some  appearance of dignity, and perhaps we should try to understand and allow for their face-saving gestures.)

Abstract: Carbon dioxide (CO2) emissions are a major contributor to the climate change equation, and thus strategies need to be developed in order to reduce increases in CO2 levels in the atmosphere.

One of the most promising approaches is to convert CO2 into useful products in engineered processes. The photocatalytic reduction of CO2 into hydrocarbon fuels is a promising way to recycle CO2 as a fuel feedstock by taking advantage of the readily available solar energy.

This article reviews the basics of CO2 photoreduction mechanisms, limiting steps, possible strategies to enhance photoreduction efficiency, and the state-of-the-art photocatalytic systems for CO2 reduction. In particular, a comparison between different catalytic systems, including biological (plants and algae), inorganics (semiconductors), organics (molecular complexes), and hybrid (enzyme/semiconductors) systems is provided.

Introduction: Fossil fuels, such as coal, petroleum, and natural gas, are the major conventional energy sources in the world due to their availability, stability, and high energy density.

(We are not reproducing passages no doubt insisted upon by the EPA, which attempt to highlight the climate evils wrought by our use of fossil fuels. They use that reasoning to justify their promotion herein of recycling Carbon Dioxide into synthetic hydrocarbon fuels such as Substitute Natural Gas. Instead of making an indecorous retreat, they are offering herein, in partnership with some major components of the Coal industry, what might well be a mutually beneficial compromise that could, in fact, be beneficial economically to the entire USA. Don't be offended if you open and read the full document. They are cracking the door and testing the water - - very, very cautiously. They have assiduously painted themselves into a tight corner over the years relative to the Carbon Dioxide issue; and, like people everywhere in all walks of life, they no doubt feel the need to preserve their own dignity, and their own political capital.)

As fossil fuels will continue to be used globally in the near future, it is imperative to consider efficient CO2 mitigation methodologies (and) to evaluate methodologies for conversion of the captured CO2 to useful products.

A proposal to regulate anthropogenic CO2 emissions from existing and future electricity generating
power plants as a part of a greater initiative to reduce and displace CO2 emissions globally (has been)suggested. Several strategies to accomplish this are being considered.

Carbon dioxide reduction can be realized by several different ways, such as biological reduction by plants and thermal, electrochemical or photocatalytic reduction using synthetic systems.

(By "reduction", they mean chemical reduction, which is the opposite of oxidation. It is a technical term which means, in essence, making un-reactive chemical molecules more reactive. Co-incidentally, chemical reduction of CO2 into, say, Methane, would also result in a physical reduction in the amount of CO2 that exists in the environment. We've previously documented all of the CO2-recycling pathways noted by the EPA and Washington University, as in, for just a few examples of, respectively, the "photocatalytic" and "electrochemical" methods::

USDOE Pittsburgh 2015 Photosynthetic Fuels from CO2 | Research & Development | News; concerning: "United States Patent 8,986,511 - Visible Light Photoreduction of CO2 Using Heterostructured Catalysts; 2015; Inventors: Christopher Matranga, et. al., Pittsburgh and Bethel Park, PA; Assignee: The United States Department of Energy, Washington, DC; Abstract: The method provides for use of sensitized photocatalyst for the photocatalytic reduction of CO2 under visible light illumination. ... Government Interests: The United States Government has rights in this invention pursuant to the employer-employee relationship of the Government to the inventors as U.S. Department of Energy employees and site-support contractors at the National Energy Technology Laboratory. ... A particular interest is the photocatalytic reduction of CO2 for the production of hydrocarbons and other valuable products using inexpensive and abundant semiconductors such as TiO2 and ZnO. Such processes provide a potential means to reduce atmospheric CO2, as well as providing an attractive alternative to purely chemical means of converting CO2 to hydrocarbons. ... It is a further object of this disclosure to provide a method of photocatalytically reducing CO2 under visible light illumination utilizing a sensitized photocatalyst in a CO2 and H2O environment. ... The method may be utilized to produce product molecules following the photocatalytic reduction of CO2 with visible light illumination. In a particular embodiment, the product molecules are comprised of hydrocarbons, such as CH4 (Methane), CH3OH (Methanol)"; and:

The USDOE Converts More Coal Exhaust CO2 into Gasoline | Research & Development | News; concerning: "United States Patent Application 20140272734 - Electrochemical Device for Syngas and Liquid Fuels Production; 2014; Inventors: Robert Braun, William Becker, and Michael Penev, CO; (USDOE National Renewable Energy Laboratory and Colorado School of Mines); Abstract: The invention relates to methods for creating high value liquid fuels such as gasoline, diesel, jet and alcohols using carbon dioxide and water as the starting raw materials and a system for using the same. These methods combine a novel solid oxide electrolytic cell (SOEC) for the efficient and clean conversion of carbon dioxide and water to hydrogen and carbon monoxide, uniquely integrated with a gas-to-liquid fuels producing method".) 

Among these options, CO2 photoreduction is gaining increasing attention since it can potentially consume alternative forms of energy by harnessing solar energy, which is abundant, cheap, and ecologically clean.

In a typical semiconductor-based photocatalyst system, the catalyst needs to absorb light energy, generate
electron-hole pairs, spatially separate them and transfer them to redox active species across the interface. In spite of its economic and environmental benefits, the photocatalytic pathways, however, are very complex and always suffer from low efficiency due to several limiting factors ... .

There are several reviews on CO2 photoreduction ... covering both fundamental CO2 photoreduction mechanisms and practical photocatalyst development. This article intends to provide a state-of-the-art overview of the basics of CO2 photoreduction pathways, and a comparison of different CO2 photoreduction
systems as listed below: (1) Biological systems, including mainly algae; (2) Inorganic photocatalysts, mostly transition metal oxides (or semiconductors), in particular TiO2-based catalysts; (3) Organic photocatalysts, including mainly metalorganic complexes; and (4) inorganic and organic/biological hybrid, or the so-called biomimetic systems, consisting of enzyme-activated or dye-sensitized semiconductors. A
summary and outlook of CO2 photoreduction have been made for future development of efficient photocatalytic systems.

As shown in (included illustrations and equations) various products could be formed based on (multi-electron transfer or MET) photoreduction reactions.

Carbon monoxide (CO) is the most common product, since the reaction needs only two protons and two electrons.

(As we've seen in a number of reports, such as:

Standard Oil Electrolyzes CO2 to Carbon Monoxide | Research & Development | News; concerning: "US Patent 4,668,349 - Electrocatalytic Reduction of CO2 by Square Planar Transition Metal Complexes; 1987; Inventors: Edward Cuellar and Verna Gaylor, OH; Assignee: The Standard Oil Company, Cleveland; Abstract: A process for the electrocatalytic reduction of carbon dioxide comprises immersing a transition metal complex with square planar geometry into an aqueous or nonaqueous solution which has been acidified to a (specified) hydrogen ion concentration ... , adding the carbon dioxide, applying an electrical potential of from about -0.8 volts to about -1.5 volts ... , and reducing the carbon dioxide to carbon monoxide";

It's been known for quite a while that we can generate Carbon Monoxide from Carbon Dioxide in electrolytic processes with voltage requirements low enough that they could certainly be powered by low-grade photovoltaic electricity. And, as in:

USDOE Carbon Monoxide + H2O = Alcohol | Research & Development | News; concerning: "United States Patent 4,656,152 - Catalyst for Producing Lower Alcohols; 1987; Inventor: Jerome Rathke, et. al., Illinois; Assignee: The United States of America, as represented by the Secretary of the USDOE; Abstract: A process and system for the production of the lower alcohols such as methanol, ethanol and propanol involves the reaction of carbon monoxide and water in the presence of a lead salt and an alkali metal formate catalyst combination";

It’s been known equally as long that Carbon Monoxide, once we've made it from Carbon Dioxide, can rather easily and directly be used and consumed in the synthesis of, among other things, fuel alcohols.)

Formic acid (HCOOH) is also a common product found in the CO2 photoreduction system, which consumes the same amount of protons and electrons, but requires slightly higher reduction potential than that for CO formation.

Some products may be formed through multiple reactions. For example, methane (CH4) could be formed (through illustrated reactions).

Comparison Between Different Systems:

(Algal) systems for photoconversion is discussed first. Many algae species have been thoroughly
investigated for their use in production of biofuels. This motivation stems from two premises: firstly, algae require CO2 to grow, thus removing CO2 from the atmosphere; secondly, while the algae grow, many species produce oils and other refinable byproducts that can be used as potential biofuel sources.

In a synthetic system, light energy is used to excite electrons in the photocatalyst which are then used to
reduce CO2. Thus, light energy is stored in the bonds of the reduced CO2 products. It is apparent that the steps carried out in these synthetic systems very much resemble what is accomplished with algae.

(In) general, synthetic systems conversion rates fall below the algal systems. However, it should be noted that in order to produce well performing algae systems a lot of resources must be consumed. The tanks for the algae must be cleaned frequently in order to prevent such as water and nutrients buildup that blocks light penetration (and) for just one gram of algae up to an entire liter of water is required. Therefore, a lot of space and water resources are required (and) CO2 uptake occurs in the algal biomass that requires cumbersome separation steps for the extraction of the oil product. Furthermore, algae systems are in general less
robust in stability compared to synthetic systems.

Semiconductor systems: There are many types of synthetic systems covered in the literature. The most common and thoroughly researched synthetic systems are semiconducting materials, such as TiO2 (Titanium Dioxide). ... TiO2 is a commonly used wide bandgap semiconductor for CO2 photoreduction because of its relatively low cost, high availability, resistance to photo-induced corrosion and low toxicity.

(We've documented the use of Titanium Dioxide as a "semiconductor" used in light-driven CO2 utilization processes in a number of earlier reports. For a more general review of the topic, see:

Stanford University Solar CO2 to Hydrocarbon Fuels | Research & Development | News; concerning: "Semiconductors and Catalysts for the Production of Solar Fuels; Prof. Thomas F. Jaramillo, Kendra Kuhl, Etosha Cave, David Abram; Dept. of Chemical Engineering; Stanford University; Topsoe Catalysis Forum; Munkerupgaard, Denmark; Jaramillo Research Group: Reactions of Interest: CO2 + nH+ + ne (=) CxHy + CaHbOH + cH2O; Fuel Production From Renewable Resources: nCO2 + m(H+ + e) = alcohols + hydrocarbons + H2O".)

Current photocatalytic systems for the reduction of CO2 are not limited to just TiO2. There are many other
semiconductor-based systems reported in the literature. Some of these semiconductors include Cadmium Sulfide, Zinc Oxide, Gallium Phosphide, Silicon Carbide, Tungsten Oxide, and various other metal oxides.

Hybrid Systems: A more trendy area of research for CO2 photoreduction includes incorporating enzymes to carry out the catalytic step. The goal behind using enzymes is to set a benchmark of what synthetic systems should be capable, based on the fact that enzymes have evolved to perform the catalytic step with high efficiency. Enzymes are highly substrate specific, show high rates of conversion,  and have evolved to be highly efficient at carrying out their catalytic functions. Thus they are an attractive option for proof- of-concept CO2 photoreduction systems.

(We've reported on a few of what might be thought of as "Hybrid Systems" for more efficiently recycling Carbon Dioxide into hydrocarbons through the combination of biological and physical processes. One example would include:

USDOE Hires Massachusetts Bugs to Convert CO2 to Alcohol | Research & Development | News; concerning: "United States Patent Application 20120288898 - Microbial Production of Multi-Carbon Chemicals and Fuels from Water and Carbon Dioxide Using Electric Current; 2012; Inventors: Derek Lovley and Kelly Nevin, MA; (Presumed eventual Assignee of Rights: University of Massachusetts - Amherst)"; which contains additional information and reference links regarding the topic of what has become known as: "Microbial Electrosynthesis (ME) Technology", which "represents a new form of photosynthesis that uses renewable solar energy to convert carbon dioxide emissions to fuels and other useful products", and "is much more efficient than biomass-based energy strategies" since it "produces organic products directly", "does not require cultivatable land and avoids environmental degradation, such as pollution of water resources, associated with intensive agricultural processes".)

Summary and Outlook: Photoreduction of CO2 is a promising approach to reduce carbon emission while simultaneously recycles it as a fuel feedstock by harnessing readily available solar energy.

The reduction mechanisms, however, are complex, involving various limiting steps. Overcoming the limiting steps is the major task for developing efficient photocatalyst systems. Several strategies have been reviewed for this purpose, including selection of semiconductors with suitable band edges, coating electron sinks, forming heterogeneous junctions, designing novel morphologies, and developing hybrid structures. A state-of-the-art comparison betweenbdifferent photocatalytic systems for CO2 reduction was nmade aiming to demonstrate the advances in this area and provide an overview of the research trend for future development of photocatalysts for CO2 photoreduction in a large scale.

The authors would like to acknowledge the support from the Consortium for Clean Coal Utilization (CCCU) at Washington University in St. Louis. ... Partial support from US EPA through Pegasus contract EP-011-006 is acknowledged."

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In point of fact, plans for both "CO2 photoreduction in a large scale" and "hybrid" electrochemical reduction of CO2 on what could prove to be a truly grand scale, for the production of hydrocarbon fuels and chemicals, are being formulated and proposed virtually around the world.

We'll be reporting on at least some of those developments in reports eventually to follow. But, one point herein should perhaps not be missed:

The United States Environmental Protection Agency concurs that Carbon Dioxide, as we can conveniently harvest from some industrial exhaust gases and even from the environment itself, can now be seen and treated as a valuable raw material resource from which, in processes powered by "solar energy", we can, on an industrial and commercial basis, synthesize valuable chemical and energy products, such as, for instance, substitute natural gas "methane".

Aren't we United States citizens of United States Coal Country entitled at least to be told, openly and publicly, about such potentials - - potentials for the use of our byproduct Carbon Dioxide which could lead to new industries and new jobs in Coal Country, and to increased freedom for the entire USA from abject reliance on OPEC oil and on environmentally questionable, if not plainly hazardous, practices currently employed for the extraction of shale natural gas?

The United States Environmental Protection Agency, alien as it might seem, appears to have opened the door at least a crack for exploration of that whole issue, even if they did so, apparently in partnership with an organized group of Coal partisans, the Consortium for Clean Coal Utilization, via presentation of their thoughts in a journal published by an organization, the Taiwan Association for Aerosol Research, now so far away from the main stream of American life and thought it surprises us, here, who actively search for such things, that we somehow managed to stumble across it.  

But, now that it's been found, maybe we should all do our best not to lose it, and, to make at least some effort to see if we can help to get some of what was revealed by the EPA herein reduced to industrial, commercial practice, for the economic benefit of Coal people, and for the economic and military security of the entire United States of America.


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