Carbon Dioxide Splitting Research Articles

Surface Dielectric Barrier Discharge (sDBD) for Flow Control in Plasma Conversion

Dielectric barrier discharges (DBD) are often used for gas conversion, such as carbon dioxide splitting, volatile organic compound removal or ozone generation. Due to the tiny plasma filaments in DBD discharges, efficient mixing of the gas flow with the plasma is essential. This is studied by using a surface dielectric barrier discharge (sDBD) with an electrode design similar to plasma actuators to optimize plasma-flow interaction. The flow pattern has been measured by Schlieren diagnostics and compared to a fluid dynamic simulation. Gas conversion efficiency has been tested by monitoring the conversion of 0.7% CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} admixed to an N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} gas stream via infrared spectroscopy in the exhaust. The actuator design of the electrodes induces a significant plasma force on the fluid, which results in the formation of vortices above the electrodes, as reproduced in the simulation. It is shown that the height of the vortices created in the velocity field can characterize the mixing process, which dominates the conversion efficiency of carbon dioxide at different gas flow rates.

Pressure-enhanced performance of metal oxides for thermochemical water and carbon dioxide splitting

Pressure-enhanced performance of metal oxides for thermochemical water and carbon dioxide splitting

Polarity dependence of CO2 conversion in nanosecond pulsed large gap dielectric barrier discharges

The splitting of carbon dioxide was investigated for a coaxial dielectric barrier discharge, which was operated with nanosecond high-voltage pulses of 500 ns and amplitudes up to 20 kV at ambient temperature and atmospheric pressure. A non-thermal plasma could be established across a gap distance of 4 mm and a length of 90 mm for gas flows of 30–210 sccm of pure CO2 and with admixtures of Argon. The application of high-voltage pulses of either positive or negative polarity resulted in distinct differences in effective conversion and CO production. The highest observed conversion of 6.6%, corresponding to a CO production of 7%, was achieved for positive high-voltage pulses of 20 kV that were applied with a repetition rate of 3 kHz for a ratio of CO2:Ar of 1:2 at a flow rate of 30 sccm. Conversely, an operation with negative high-voltage pulses, for otherwise the same operating parameters, resulted in an effective conversion of only 5.3% and CO production of 5.4%. The corresponding conversion rates for specific energy input (SEI), concerning different operating parameters, could be related to reaction enthalpies that were calculated from thermodynamic functions. The differences in polarity were associated with discharge characteristics, i.e., plasmas appeared more filamentary for positive high-voltage pulses. In this case, a visible plasma could also be established for much lower pulse amplitudes.Graphical

Selection of iron-based oxygen carriers for two-step solar thermochemical splitting of carbon dioxide

The two-step solar thermochemical cycle is a prospective clean energy technology that enables the direct splitting of water and carbon dioxide for solar fuel production. However, immature oxygen carriers fundamentally restrict the solar-to-fuel conversion efficiency and thus prevent this technology from immediate industrial uptake. Focusing on the conventional iron-based oxygen carriers, this study intends to find a modified oxygen carrier with low reaction temperature requirements and excellent reaction performance, so as to attain dual optimization in terms of thermal efficiency and chemical efficiency. The thermochemical reaction characteristics of six common ferrites and four metal dopants are compared via thermogravimetric analysis under the same programmed temperature control. For further practical applications of the selected oxygen carrier, a foam-structured material with SiC as support is prepared and subsequently experimented in a self-designed 18-kW thermochemical system. The results indicate that the modified oxygen carriers obtained by direct doping of CoFe2O4 with 50wt% NiO exhibit optimal reaction performance, giving the highest CO yield of 439μmol/g. Additionally, the foam-structured material enable a peak CO yield of 7.0 mL min−1 g−1 and CO2 conversion of 45.5% at a reduction temperature of only 1100°C, which might be attributed to the micron-scale pore structure as well as the generation of aluminosilicate crystal structures.

Cost effective decarbonisation of blast furnace – basic oxygen furnace steel production through thermochemical sector coupling

We present here a first-principles study of the sector coupling between a thermochemical carbon dioxide (CO2) splitting cycle and existing blast furnace – basic oxygen furnace (BF-BOF) steel making for cost-effective decarbonisation. A double perovskite, Ba2Ca0.66Nb0.34FeO6, is proposed for the thermochemical splitting of CO2, a viable candidate due to its low reaction temperatures, high carbon monoxide (CO) yields, and 100% selectivity towards CO. The CO produced by the TC cycle replaces expensive metallurgical coke for the reduction of iron ore to metallic iron in the blast furnace (BF). The CO2 produced from the BF is used in the TC cycle to produce more CO, therefore creating a closed carbon loop, allowing for the decoupling of steel production from greenhouse gas emissions. Techno-economic analysis of the implementation of this system in UK BF-BOFs could reduce steel sector emissions by 88% while increasing the cost-competitiveness of UK steel on the global market through cost reduction. After five years, this system would save the UK steel industry £1.28 billion while reducing UK-wide emissions by 2.9%. Implementation of this system in the world's BF-BOFs could allow the steel sector to decarbonise in line with the Paris Climate Agreement to limit warming to 1.5 °C.

Investigation of CO2 Splitting on Ceria-Based Redox Materials for Low-Temperature Solar Thermochemical Cycling with Oxygen Isotope Exchange Experiments

The surface exchange and bulk transport of oxygen are highly relevant to ceria-based redox materials, which are envisaged for the solar thermochemical splitting of carbon dioxide in the future. Experimental investigations of oxygen isotope exchange on CeO2-δ, Ce0.9M3+0.1O1.95-δ (with M3+ = Y, Sm) and Ce0.9M4+0.1O2-δ (with M4+ = Zr) samples were carried out for the first time utilizing oxygen-isotope-enriched C18O2 gas atmospheres as the tracer source, followed by Secondary Ion Mass Spectrometry (SIMS), at the temperature range 300 ≤ T ≤ 800 °C. The experimental K˜O and D˜O data reveal promising results in terms of CO2 splitting when trivalent (especially Sm)-doped ceria is employed. The reaction temperatures are lower than previously proposed/reported due to the weak temperature dependency of the parameters K˜O and D˜O. The majority of isotope exchange experiments show higher values of K˜O and D˜O for Sm-doped cerium dioxide in comparison to Y-doped and Zr-doped ceria, as well as nominally undoped ceria. The apparent activation energies for both K˜O and D˜O are lowest for Sm-doped ceria. Using Zr-doped cerium oxide exhibits various negative aspects. The Zr-doping of ceria enhances the reducibility, but the possible Zr-based surface alteration effects and dopant-induced migration barrier enhancement in Zr-doped ceria are detrimental to surface exchange and oxygen diffusion at lower temperatures of T ≤ 800 °C.

Thermochemical activation of CO2 into syngas over ceria-supported niobium oxide catalyst: An integrated experimental-DFT study

Thermochemical splitting of a mixture of CO2 and water into syngas (and methane) remains a viable approach toward an industrial-scale treatment of CO2 emission. However, most deployed catalysts encompass expensive metallic ingredients such as Pd or Pt. In an integrated experimental-modelling approach, this work reports a high conversion of CO2 over alternative and cost-effective configurations. Ceria-based catalysts are proven to be effective in numerous catalytic processes owing to the facile switch in the Ce redox cycle. Evolution of H2 and CO from thermochemical splitting of water and carbon dioxide is an important process in the production of syngas and in fuel cell applications. In this study, NbOx ceria catalysts are prepared, characterized, and applied for production of syngas via the thermochemical splitting of CO2 and gaseous water. It was observed that presence of Nb in the ceria matrix up to 12 wt%, increases the reaction yield at higher temperature (up to 79% CO2 conversion with 80% selectivity to syngas at 600 ºC). Moreover, the catalytic reaction was found to display a higher selectivity towards syngas over the ceria supported catalysts. The attained conversion is higher than other ceria-supported catalysts such as Rh-CeO2, CeO2-ZrO2, and V2O5-CeO2. Mapped-out reaction pathways by DFT calculations portray accessible routes into syngas. Results provided herein should be useful to optimize a continuous process for the valorization of CO2 into syngas over relatively affordable a catalytic formulation.

Recent advances in the solar thermochemical splitting of carbon dioxide into synthetic fuels

Recent years have seen a sharp rise in CO2 emissions into the atmosphere, which has contributed to the issue of global warming. In response to this several technologies have been developed to convert CO2 into fuel. It is discovered that the employment of a solar-driven thermochemical process (S-DTCP) that transforms CO2 into fuels can increase the efficiency of the production of sustainable fuels. The process involves the reduction of metal oxide (MO) and oxidizing it with CO2 in a two-step process using concentrated solar power (CSP) at higher and lower temperatures, respectively. This study summarizes current advancements in CO2 conversion methods based on MO thermochemical cycles (ThCy), including their operating parameters, types of cycles, and working principles. It was revealed that the efficiency of the solar conversion of CO2 to fuel is not only influenced by the composition of the MO, but also by its morphology as well as the available surface area for solid/gas reactions and the diffusion length. The conversion mechanism is governed by surface reaction, which is influenced by these two parameters (diffusion length and specific surface area). Solar energy contributes to the reduction and oxidation steps by promoting reaction kinetics and heat and mass transport in the material. The information on recent advances in metal oxide-based carbon dioxide conversion into fuels will be beneficial to both the industrial and academic sectors of the economy.

Industrial carbon monoxide production by thermochemical CO2 splitting – A techno-economic assessment

This research presents the splitting of carbon dioxide (CO2) by Ba2Ca0.66Nb0.34FeO6 (BCNF1) at the 100 g scale and the techno-economic assessment of a carbon-neutral carbon monoxide (CO) production facility based upon this perovskite. BCNF1 was found to convert 10.1 % of CO2 to CO with 100 % selectivity at 800 °C, which was sustained for five thermochemical cycles showing little sign of degradation. This oxidation reaction was found to proceed via a zero order reaction mechanism at 800 °C, with an activation energy of 46.6 kJ/mol. This activation energy for CO2 splitting is lower than all bar one of the perovskites investigated in the literature, explaining the lower oxidation temperature required and higher CO yields of this material. Economic evaluation of an industrial scale-up system based on this data suggested profitability despite high sensitivity to electricity prices, as expected. A 150 m3/hr plant would produce CO at $0.15 per kg at the average industrial US electricity price of $0.068/kWh. This is significantly cheaper than reported costs of electrochemically produced CO in the literature. As electricity prices fall due to abundant renewables, larger production volumes become optimal, with $1.3 million a year profits for a 500 m3/hr plant at $0.05/kWh.

Carbon dioxide splitting and hydrogen production using a chemical looping concept: A review

The gradually increasing atmospheric concentration of greenhouse gases has caused global climate change and subsequent environmental problems. To negate the emission of greenhouse gases from human activities, converting captured carbon into value-added products and changing our energy paradigm from fossil fuels to hydrogen both are significantly investigated. Chemical looping technology can offer several advantages since CO/H2 production efficiency can be enhanced due to the inherent product separation and autothermal operation. This report presents a brief review of the chemical looping process combined with CO2 or H2O splitting to provide CO or H2, respectively. Thermodynamic analysis was carried out to determine viable transition metal oxides. Various oxygen carriers for the chemical looping CO2/H2O splitting were categorized according to their structural characteristics. In addition, studies on different reactors, including fluidized-, moving bed-, and fixed bed-types which have proven their potential for realizing large-scale operation of chemical looping processes were summarized. Based on past advances and additional aspects of chemical looping, the authors strongly believe that this process offers a promising commercial technology that will contribute to carbon neutrality.

Combined heat and mass transfer analysis of solar reactor integrating porous reacting media for water and carbon dioxide splitting

Radiative heat flux transfer across a chemical reacting media is a complex system mostly characterized by phenomena including in-situ heating and chemical species micro-mass transport. To solve simultaneously the issue associated with radiative heat transport and chemical conversion intensification, this study developed a combined heat and mass transfer process of a solar reactor integrating Fe-Co-CuO coated SiC porous reacting media. It is demonstrated providing a larger convective heat transfer interface in the oxidation region could result in excessive solar energy absorption with a significant reduction in H2O and CO2 conversion. From the mechanistic aspect, there exists a trade-off between heat transfer enhancement and chemical conversion performance improvement. While re-radiation heat loss at the reactor front face was found as a major factor affecting efficient solar energy conversion, the performance indicators of the reactor are strongly influenced by the permeability of the reacting media. The higher the chemical products evolution in the reacting media, the higher the solar fuel conversion efficiency of up to 33.52% can be gained using a cavity having a porous media of Ф = 0.9 porosity and dp = 0.019 mm under 30 kW/m2 radiative heat flux. This study provided comprehensive insights into solar in-situ heating and thermal transport combining chemical species micro-mass transport mechanisms in a thermochemical reactor.

Towards chemical equilibrium in thermochemical water splitting. Part 1: Thermal reduction

The efficiency of many processes strongly depends on their thermodynamic reversibility, i.e., proximity to equilibrium throughout the process. In thermochemical cycles for water and/or carbon dioxide splitting, thermochemical air separation, and thermochemical energy storage, operating near equilibrium means that the oxygen chemical potential of the solid and gas phases must not differ significantly. We show that approaching this ideal is possible in thermal reduction only if the reaction step occurs at a specific, reaction coordinate- and material-dependent temperature. The resulting thermal reduction temperature profile also depends on the ratio of gas and solid flows. • Method to achieve reversible/equilibrium reduction in water splitting cycles. • Reversible isothermal reduction is not feasible in practice. • Strong technical and physical limitations on the amount of sweep gas. • Limited impact of gas purity on reduction extent at fixed flow/maximum temperature. • High reduction temperatures expand the solution space for high cycle efficiency.

Sorbent-based oxygen separation with YBC114 for energy storage systems

In this work, we aimed to design, build, and evaluate an oxygen separation system to provide an inert sweep gas with low oxygen partial pressure (pO2) to redox-active thermochemical energy conversion reactors for a range of applications, including two-step redox cycles for thermochemical energy storage, water splitting, and carbon-dioxide splitting. The separation is based on an oxygen-selective sorbent, YBaCo4O7+δ (YBC114), which has excellent oxygen sorption and desorption properties demonstrated in our previous work. The oxygen separation performance of YBC114 was comprehensively studied by thermogravimetric analysis, sorption breakthrough experiments, and temperature swing sorption - desorption cycles. The results reveal that YBC114 can produce inert sweep gas with an oxygen concentration of less than 100 ppmv for at least 20 min during the thermal swing adsorption (TSA) cycle with the current sorption bed configuration, and the performance is consistent from cycle to cycle. The optimal sorption and desorption temperatures for the TSA process with YBC114 are determined to be 300 °C and 500 °C, respectively. Although challenges remain for the current separation system (e.g., high sorption temperature and slow kinetics), this study demonstrates the potential to use the oxygen-selective sorbent to produce an inert sweep gas, the feasibility of the oxygen separation concept, and guides new sorbent material development to make this application economically practical. A simple procedure is described for designing the YBC114 oxygen separation process.

Synergies between Direct Air Capture Technologies and Solar Thermochemical Cycles in the Production of Methanol

Methanol is an example of a valuable chemical that can be produced from water and carbon dioxide through a chemical process that is fully powered by concentrated solar thermal energy and involves three steps: direct air capture (DAC), thermochemical splitting and methanol synthesis. In the present work, we consider the whole value chain from the harvesting of raw materials to the final product. We also identify synergies between the aforementioned steps and collect them in five possible scenarios aimed to reduce the specific energy consumption. To assess the scenarios, we combined data from low and high temperature DAC with an Aspen Plus® model of a plant that includes water and carbon dioxide splitting units via thermochemical cycles (TCC), CO/CO2 separation, storage and methanol synthesis. We paid special attention to the energy required for the generation of low oxygen partial pressures in the reduction step of the TCC, as well as the overall water consumption. Results show that suggested synergies, in particular, co-generation, are effective and can lead to solar-to-fuel efficiencies up to 10.2% (compared to the 8.8% baseline). In addition, we appoint vacuum as the most adequate strategy for obtaining low oxygen partial pressures.

A kinetic model for evolution of H2 and CO over Zr-doped ceria

Among notable catalytic assisted processes by ceria-abased materials are the production reactions of H2 and CO from solar thermochemical splitting of water and carbon dioxide, respectively, for applications pertinent to hydrogen fuel cell and synthesis of syngas. Doping ceria with isovalent cations, most notably Zr, was shown to enhance the yield of O2, H2, and CO. Via sophisticated measurements techniques, literature provided several global-like rates for the overall evolutions of H2 and CO. However, these values remain without a mechanistic verification by means of first-principles calculations. Herein, we map out mechanisms and construct a detail chemistry kinetic model for the dissociative adsorption of H2O and CO2 over pure and Zr-decorated ceria surfaces. The overarching objective of the kinetic model is to deduce temperature-dependent profiles that account for the experimentally observed evolution of O2, H2, and CO during the redox cycles of ceria and to reveal the effect of Zr dopants. Ce surface atoms in the latter incur higher positive charges, and hence more affinity to capture gas phase molecules. Splitting of H2O into a gas phase H2 over the Zr-substituted surface ensues in two consecutive steps through activation energies of 77.7 kJ/mol and 191.2 kJ/mol. Our computed rate constant for evolution of H2 over ceria amounts to 2.67 mL/g. min, within the narrow range of the experimental values scattered between 1.5–5.4 mL/g. min. Formation of H2 and CO arises at a ∼ 100 K lower temperature over the Zr-doped surface in reference to pure ceria. The developed kinetic model is expected to describe - on a precise atomic basis - the H2O/CO2 redox cycles of ceria-based materials and the promoting effects of dopants.

Reaction performance and lattice oxygen migration of MnFe2O4 oxygen carrier in methane-carbon dioxide reaction system

Chemical looping partial oxidation of methane (CLPOM) coupled with carbon dioxide splitting process was proposed in this work to achieve high H2/CO ratio syngas and CO production simultaneously. Manganese ferrite (MnFe2O4) oxygen carrier with a spinel structure was prepared by using a co-precipitation phase inversion method for this methane-carbon dioxide reaction system. The reaction performance of oxygen carrier was investigated in fixed bed reactor combined with the analytical methods of XRD, TPR, H2-TG and XPS. The results revel that spinel structure MnFe2O4was successfully prepared and Fe is the main active spices to release lattice oxygen. TG analysis confirms that 43.3% of lattice oxygen can release from MnFe2O4 in H2 atmosphere with highest release rate 0.4%/min at 721 °C. The maximum conversion of CH4 and CO2 are 63% and 99% achieved in CLPOM coupled with CO2 splitting process and temperature makes a positive effect on the reaction process. Moreover, the reaction stability of MnFe2O4 oxygen carrier are verified in 10 cycles reaction of CLPOM coupled with CO2 splitting with the reaction path MnFe2O4→(FeO)0.798-(MnO)0·202/FeO →MnFe2O4. Moreover, The MnFe2O4 oxygen carriers with different reduction stages were analyzed by XPS to reveal lattice oxygen migration mechanism, which indicates that the bulk lattice oxygen of oxygen carrier gradually dissociated and migrated to the outer surface in reaction process where reacts directly with methane or converts to oxygen adsorption OII. The valence of Mn has not changed in the whole reaction process, whereas, Mn species forms the synergistic effect with Fe to improve the conversion of CH4 and CO2, promoting the oxidization of Fe2+ to Fe3+ in CO2 atmosphere. MnFe2O4 oxygen carrier is a promising candidate for the CLPOM coupled with CO2 splitting process.

Recent progress on nanostructured bimetallic electrocatalysts for water splitting and electroreduction of carbon dioxide

The exploitation of renewable energy as well as the elimination of the harmful impact of excessive carbon emission are worldwide concerns for sustainable development of the ecological environment on earth. To address that, the technologies regarding energy conversion systems, such as water splitting and electroreduction of carbon dioxide, have attracted significant attention for a few decades. Yet, to date, the production of green fuels and/or high energy density chemicals like hydrogen, methane, and ethanol, are still suffering from many drawbacks including high energy consumption, low selectivity, and sluggish reaction rate. In this regard, nanostructured bimetallic materials that is capable of taking the full benefits of the coupling effects between different elements/components with structure modification in nanoscale are considered as a promising strategy for high-performance electrocatalysts. Herein, this review aims to outline the important progress of these nanostructured bimetallic electrocatalysts. It starts with the introduction of some important fundamental background knowledge about the reaction mechanism to understand how these reactions happen. Subsequently, we summarize the most recent progress regarding how the nanostructured bimetallic electrocatalysts manipulate the activity and selectivity of catalytic reactions in the order of bimetallic alloying effect, interface/substrate effect of bi-component electrocatalyst, and nanostructuring effect.

A First‐Principles‐Based Sub‐Lattice Formalism for Predicting Off‐Stoichiometry in Materials for Solar Thermochemical Applications: The Example of Ceria

AbstractTheoretical models that reliably can predict off‐stoichiometry in materials via accurate descriptions of underlying thermodynamics are crucial for energy applications. For example, transition‐metal and rare‐earth oxides that can tolerate a large number of oxygen vacancies, such as CeO2 and doped CeO2, can split water and carbon dioxide via a two‐step, oxide‐based solar thermochemical (STC) cycle. The search for new STC materials with a performance superior to that of state‐of‐the‐art CeO2 can benefit from predictions accurately describing the thermodynamics of oxygen vacancies. The sub‐lattice formalism, a common tool used to fit experimental data and build temperature‐composition phase diagrams, can be useful in this context. Here, sub‐lattice models are derived solely from zero‐temperature quantum mechanics calculations to estimate fairly accurate temperature‐ and oxygen‐partial‐pressure‐dependent off‐stoichiometries in CeO2 and Zr‐doped CeO2. Physical motivations for deriving some of the “excess” sub‐lattice model parameters directly from quantum mechanical calculations, instead of fitting to minimize deviations from experimental and/or theoretical data, are identified. Important limitations and approximations of the approach used are specified and extensions to multi‐cation oxides are also suggested to help identify novel candidates for water and carbon dioxide splitting and related applications.

Thermally-driven adsorption/desorption cycle for oxygen pumping in thermochemical fuel production

The two-step cycle for solar-thermochemical fuels production and thermochemical energy storage benefits from low oxygen partial pressure in the high-temperature thermal reduction step. To be practical, low oxygen partial pressures must be reached by energetically efficient and economically affordable methods—a challenge currently not met by either mechanical vacuum pumping or by inert gas sweeping. To address this challenge, we have examined a promising, thermally-driven surface adsorption/desorption approach. Providing that appropriately designed materials can be identified as expected, this approach would substantially advance solar-thermochemical fuel production (water and carbon dioxide splitting), thermochemical energy storage, and related technologies.

A Review of Solar Thermochemical CO2 Splitting Using Ceria-Based Ceramics With Designed Morphologies and Microstructures.

This review explores the advances in the synthesis of ceria materials with specific morphologies or porous macro- and microstructures for the solar-driven production of carbon monoxide (CO) from carbon dioxide (CO2). As the demand for renewable energy and fuels continues to grow, there is a great deal of interest in solar thermochemical fuel production (STFP), with the use of concentrated solar light to power the splitting of carbon dioxide. This can be achieved in a two-step cycle, involving the reduction of CeO2 at high temperatures, followed by oxidation at lower temperatures with CO2, splitting it to produce CO, driven by concentrated solar radiation obtained with concentrating solar technologies (CST) to provide the high reaction temperatures of typically up to 1,500°C. Since cerium oxide was first explored as a solar-driven redox material in 2006, and to specifically split CO2 in 2010, there has been an increasing interest in this material. The solar-to-fuel conversion efficiency is influenced by the material composition itself, but also by the material morphology that mostly determines the available surface area for solid/gas reactions (the material oxidation mechanism is mainly governed by surface reaction). The diffusion length and specific surface area affect, respectively, the reduction and oxidation steps. They both depend on the reactive material morphology that also substantially affects the reaction kinetics and heat and mass transport in the material. Accordingly, the main relevant options for materials shaping are summarized. We explore the effects of microstructure and porosity, and the exploitation of designed structures such as fibers, 3-DOM (three-dimensionally ordered macroporous) materials, reticulated and replicated foams, and the new area of biomimetic/biomorphous porous ceria redox materials produced from natural and sustainable templates such as wood or cork, also known as ecoceramics.