Enhanced CO2 Removal Research Articles

Intraspecific variability in plant and soil chemical properties in a common garden plantation of the energy crop Populus.

Optimizing crops for synergistic soil carbon (C) sequestration can enhance CO2 removal in food and bioenergy production systems. Yet, in bioenergy systems, we lack an understanding of how intraspecies variation in plant traits correlates with variation in soil biogeochemistry. This knowledge gap is exacerbated by both the heterogeneity and difficulty of measuring belowground traits. Here, we provide initial observations of C and nutrients in soil and root and stem tissues from a common garden field site of diverse, natural variant, Populus trichocarpa genotypes-established for aboveground biomass-to-biofuels research. Our goal was to explore the value of such field sites for evaluating genotype-specific effects on soil C, which ultimately informs the potential for optimizing bioenergy systems for both aboveground productivity and belowground C storage. To do this, we investigated variation in chemical traits at the scale of individual trees and genotypes and we explored correlations among stem, root, and soil samples. We observed substantial variation in soil chemical properties at the scale of individual trees and specific genotypes. While correlations among elements were observed both within and among sample types (soil, stem, root), above-belowground correlations were generally poor. We did not observe genotype-specific patterns in soil C in the top 10 cm, but we did observe genotype associations with soil acid-base chemistry (soil pH and base cations) and bulk density. Finally, a specific phenotype of interest (high vs low lignin) was unrelated to soil biogeochemistry. Our pilot study supports the usefulness of decade-old, genetically-variable, Populus bioenergy field test plots for understanding plant genotype effects on soil properties. Finally, this study contributes to the advancement of sampling methods and baseline data for Populus systems in the Pacific Northwest, USA. Further species- and region-specific efforts will enhance C predictability across scales in bioenergy systems and, ultimately, accelerate the identification of genotypes that optimize yield and carbon storage.

Enhanced CO2 Removal Through the Electrolysis of Concentrated Seawater and Accelerated Mineral Carbonation

Enhanced CO2 Removal Through the Electrolysis of Concentrated Seawater and Accelerated Mineral Carbonation

Enhanced CO2 removal in hollow fiber membrane contactors using amine-based nanofluids

Increasing the mass transfer coefficient, improving the rheological properties of the liquid, reducing the possibility of wetting, and reducing the consumption of the absorbent are among the significant effects of using nanofluids in membrane contactors as chemical absorbents. The use of nanofluids allows the system to use higher transmembrane pressures and higher liquid flow rates. In this work, stable amine-based nanofluid were prepared by adding different amounts (0–0.4 wt%) of three nanoparticles (Al2O3, Fe3O4, and MWCNT-COOH) to MEA aqueous solution. Amine-based nanofluids were then used in a membrane contactor to remove CO2 from the gas mixtures. The influence of effective parameters on the separation performance was evaluated in order to better understand how NPs affect CO2 removal. The findings of this work show that the use of nanofluids can improve CO2 removal performance by 5% and thus reduce adsorbent consumption by 20%. The effect of nanoparticle dispersion on mass transfer flux was evaluated using a new enhancement factor (Rnano). Numerical methods were used to provide a suitable equation for Rnano so that it can be combined with general mass transfer equations. The Rnano values obtained for the NPs used in this work were in the range of 0.03–0.05.

CO2 Capture and H2 Recovery Using a Hollow Fiber Membrane Contactor

In this study, hydrogen was recovered and purified by using a membrane contactor unit from CO2-rich gas without the use of any basic chemicals such as amines. The membrane operational parameters were adjusted to achieve high CO2 removal and H2 recovery. The effects of gas flow rate, pressure, gas composition (CO2/H2 ratio), pressure difference between liquid and gas, and gas/liquid ratio on CO2 removal and H2 recovery were investigated. Depending on the gas flow rate, the contact time between gas and liquid could be controlled, changing the absorption amounts of CO2 and H2. Regarding gas composition, an increase in the CO2/H2 ratio from 0.25 to 1 boosted H2 recovery. Furthermore, increasing the CO2/H2 ratio above 1 (from 1 to 3) generally reduced H2 recovery from 98.7% to 83%. Additionally, supplementation with the optimal amount of additive enhanced CO2 removal and H2 recovery. Thus, using a membrane contactor system results in high CO2 removal (82.7–93.5%) and H2 recovery (91.5–98.7%). Moreover, H2 production and separation can be performed in one system, implying that CO2 removal can be performed more efficiently by the membrane contactor. This study offers a new and promising route for producing high-purity H2 while removing CO2.

Engineered living photosynthetic biocomposites for intensified biological carbon capture

Carbon capture and storage is required to meet Paris Agreement targets. Photosynthesis is nature’s carbon capture technology. Drawing inspiration from lichen, we engineered 3D photosynthetic cyanobacterial biocomposites (i.e., lichen mimics) using acrylic latex polymers applied to loofah sponge. Biocomposites had CO2 uptake rates of 1.57 ± 0.08 g CO2 g−1biomass d−1. Uptake rates were based on the dry biomass at the start of the trial and incorporate the CO2 used to grow new biomass as well as that contained in storage compounds such as carbohydrates. These uptake rates represent 14–20-fold improvements over suspension controls, potentially scaling to capture 570 tCO2 t−1biomass yr−1, with an equivalent land consumption of 5.5–8.17 × 106 ha, delivering annualized CO2 removal of 8–12 GtCO2, compared with 0.4–1.2 × 109 ha for forestry-based bioenergy with carbon capture and storage. The biocomposites remained functional for 12 weeks without additional nutrient or water supplementation, whereupon experiments were terminated. Engineered and optimized cyanobacteria biocomposites have potential for sustainable scalable deployment as part of humanity’s multifaceted technological stand against climate change, offering enhanced CO2 removal with low water, nutrient, and land use penalties.

The Effect of MDEA/AMP and Span-80 in Water-in-Oil (W/O) Emulsion for Carbon Dioxide Absorption

Emulsion liquid membrane (ELM) has been widely studied as an alternative method for amine absorption technology in the removal of acid gases such as carbon dioxide (CO2) and hydrogen sulphide (H2S). However, searching for stable ELM formulation with an enhanced CO2 absorption remains as challenge. Therefore, in this study, the aqueous solution containing a mixture of methyl diethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) in sodium hydroxide (NaOH) solution was introduced as a dispersed phase, kerosene as continuous phase and Span-80 acts as a surfactant for the formation of water-in-oil (W/O) emulsion. In this study, the dispersed phase consists of 8% v/v MDEA and 4% v/v AMP and the continuous phase which contains 6% v/v Span-80 produced a stable emulsion and exhibited 65.2% of CO2 removal. This study indicates that the introduction of blended amine able to produce stable emulsion with an enhanced CO2 removal.

Enhanced ectoines production by carbon dioxide capture: A step further towards circular economy

Recycling of greenhouse gases to produce industrially valuable products has become one of the big pillars to achieve circularity. This study demonstrates for the first time the feasibility of producing ectoine with Halomonas stevensii with CO2 as the added carbon source, and CO2 and glucose. Initially, CO2 alone was fed to continuous reactors, adding thiosulphate as the energy source. Maximum CO2 elimination capacities of 24.2 mg CO2 L−1 h−1 were obtained, and ectoine contents up to 7.3% (g ectoine⸱g biomass−1). To enhance ectoine production, CO2 conversion coupled with discontinuous glucose addition was implemented. The amendment of 0.5 g L−1 of glucose at the beginning of reactor operation enhanced CO2 removal to 37.1 mg CO2 L−1 h−1 and increased ectoine contents up to 22%. Our results represent the proof of concept for a CO2 biotransformation platform to produce ectoines, so far unexplored. This can foster the development of more sustainable microbial processes for the production of ectoines helping in the abatement of CO2.

Removal of atmospheric CO2 by engineered soils in infrastructure projects

The use of crushed basic igneous rock and crushed concrete for enhanced rock weathering and to facilitate pedogenic carbonate precipitation provides a promising method of carbon sequestration. However, many of the controls on precipitation and subsequent effects on soil properties remain poorly understood. In this study, engineered soil plots, with different ratios of concrete or dolerite combined with sand, have been used to investigate relationships between sequestered inorganic carbon and geotechnical properties, over a two-year period. Cone penetration tests with porewater pressure measurements (CPTu) were conducted to determine changes in tip resistance and pore pressure. C and O isotope analysis was carried out to confirm the pedogenic origin of carbonate minerals. TIC analysis shows greater precipitation of pedogenic carbonate in plots containing concrete than those with dolerite, with the highest sequestration values of plots containing each material being equivalent to 33.7 t C ha−1 yr−1 and 17.5 t C ha−1 yr−1, respectively, calculated from extrapolation of results derived from the TIC analysis. TIC content showed reduction or remained unchanged for the top 0.1 m of soil; at a depth of 0.2 m however, for dolerite plots, a pattern of seasonal accumulation and loss of TIC emerged. CPTu tip resistance measurements showed that the presence of carbonates had no observable effect on penetration resistance, and in the case of porewater pressure measurements, carbonate precipitation does not change the permeability of the substrate, and so does not affect drainage. The results of this study indicate that both the addition of dolerite and concrete serve to enhance CO2 removal in soils, that soil temperature appears to be a control on TIC precipitation, and that mineral carbonation in constructed soils does not lead to reduced drainage or an increased risk of flooding.

A Minimally Invasive and Highly Effective Extracorporeal CO2 Removal Device Combined With a Continuous Renal Replacement Therapy.

Extracorporeal carbon dioxide removal is used to treat patients suffering from acute respiratory failure. However, the procedure is hampered by the high blood flow required to achieve a significant CO2 clearance. We aimed to develop an ultralow blood flow device to effectively remove CO2 combined with continuous renal replacement therapy (CRRT). Preclinical, proof-of-concept study. An extracorporeal circuit where 200 mL/min of blood flowed through a hemofilter connected to a closed-loop dialysate circuit. An ion-exchange resin acidified the dialysate upstream, a membrane lung to increase Pco2 and promote CO2 removal. Six, 38.7 ± 2.0-kg female pigs. Different levels of acidification were tested (from 0 to 5 mEq/min). Two l/hr of postdilution CRRT were performed continuously. The respiratory rate was modified at each step to maintain arterial Pco2 at 50 mm Hg. Increasing acidification enhanced CO2 removal efficiency of the membrane lung from 30 ± 5 (0 mEq/min) up to 145 ± 8 mL/min (5 mEq/min), with a 483% increase, representing the 73% ± 7% of the total body CO2 production. Minute ventilation decreased accordingly from 6.5 ± 0.7 to 1.7 ± 0.5 L/min. No major side effects occurred, except for transient tachycardia episodes. As expected from the alveolar gas equation, the natural lung Pao2 dropped at increasing acidification steps, given the high dissociation between the oxygenation and CO2 removal capability of the device, thus Pao2 decreased. This new extracorporeal ion-exchange resin-based multiple-organ support device proved extremely high efficiency in CO2 removal and continuous renal support in a preclinical setting. Further studies are required before clinical implementation.

Enhancement of CO2 removal by promoted MDEA solution in a hollow fiber membrane contactor: A numerical and experimental study

In this work, carbon dioxide (CO2) loading capacity of methyldiethanolamine (MDEA) solution promoted by potassium lysinate (KLys) was experimentally measured by using a gas absorption setup at different concentrations and temperatures. The CO2 removal efficiency of the MDEA + KLys solution was investigated for a CO2/N2 gas mixture by using computational fluid dynamic (CFD) simulations in a hollow fiber membrane contactor (HFMC). The effects of operating conditions including solvent concentration, solvent flow rate, gas flow rate, inlet CO2 concentration and module length on the CO2 removal efficiency were also studied. The experimental results revealed that CO2 loading capacity increases with increasing KLys concentration in the solution, while decreases as temperature increases. The simulation results indicated that MDEA + KLys solution has higher CO2 removal efficiency compared to pristine MDEA and MEA solutions. The CO2 removal efficiency increases with increasing solvent concentration, solvent flow rate and module length, whereas decreases as gas flow rate increases. The zeolitic imidazolate framework-8 (ZIF-8), as sorbent, was then incorporated into the MDEA + KLys solution and its effect on the CO2 removal efficiency was also examined. The MDEA + KLys + ZIF-8 nano-absorbent showed higher CO2 removal efficiency than that of MDEA + KLys absorbent, where introducing 0.4 wt.% ZIF-8 enhanced CO2 removal from ⁓96% to ⁓99%. The results of this work suggest that both MDEA + KLys absorbent and MDEA + KLys + ZIF-8 nano-absorbent are promising candidates for CO2 absorption processes. However, for practical use as well as a complete investigation, their behavior should be assessed by using other parameters of solvent such as reactivity with CO2, corrosion rate, and regeneration performance.

Effects of various anions and cations in ionic liquids on CO2 capture

Blends of ionic liquids (ILs) with monoethanolamine (MEA) in 1-hexanol were employed to enhance CO2 removal in comparison with that of pure MEA. A series of hydrophobic and hydrophilic 1-alkyl-3-methylimidazolium-based ionic liquids ([Cn-mim][Ac], [Cn-mim][Cl], and [Cn-mim][Tf2N] with n = 2 or 4) were studied to investigate the absorption/desorption performance, which is known to be affected by changes in the type of anion used and the alkyl chain length in the cation. Three different weight percentages of ILs were added to 20 wt% MEA, and the maximum amine concentration in the liquid was obtained as 30 wt/wt%. The absorption capacity (or equilibrium solubility) was noted to be highly dependent on the selection of the anion, whereas the choice of cation had a minor effect. The results revealed that the addition of IL significantly improved the CO2 capture performance, and indicated a favorable loading ratio. The [bmim][Ac] IL was found to result in the highest CO2 equilibrium loading (0.89 mol CO2/(mol [bmim][Ac])) compared to that in other blends. Moreover, the interactions between CO2 and the blend systems were characterized using Fourier transform infrared spectrometry (FTIR) to analyze the reusability and potential performance losses of the solvent systems.

Chemical Absorption of CO2 Enhanced by Nanoparticles Using a Membrane Contactor: Modeling and Simulation.

In the present work, membrane resistance was estimated and analyzed, and the results showed that total membrane resistance increased sharply when membrane pores were wetted. For further study, a two-dimensional (2D) mathematical model was developed to predict the chemical absorption of CO2 in aqueous methyldiethanolamine (MDEA)-based carbon nanotubes (CNTs) in a hollow fiber membrane (HFM) contactor. The membrane was divided into wet and dry regions, and equations were developed and solved using finite element method in COSMOL. The results revealed that the existence of solid nanoparticles enhanced CO2 removal rate. The variables with more significant influence were liquid flow rate and concentration of nanoparticles. Furthermore, there was a good match between experimental and modeling results, with the modeling estimates almost coinciding with experimental data. Solvent enhanced by solid nanoparticles significantly improved the separation performance of the membrane contactor. There was around 20% increase in CO2 removal when 0.5 wt% CNT was added to 5 wt% aqueous MDEA.

Anodic vs cathodic potentiostatic control of a methane producing microbial electrolysis cell aimed at biogas upgrading

A fully biological Microbial Electrolysis Cell (MEC) aimed at biogas upgrading has been operated under different operating conditions in order to enhance CO2 removal from a synthetic biogas. Specifically, CO2 reduction into CH4 occurred at the MEC biocathode with the oxidation of organic substrates in the anodic chamber partially sustaining the energy demand of the process. In the cathode chamber, methane formation was the main driver of current generation which, in turn, sustained alkalinity generation and related CO2 sorption. This study mainly focused on the minimization of the anodic and cathodic overpotentials to maximize the process efficiency. To accomplish this objective, an innovative strategy of MEC polarization was adopted, consisting in the shift of the potentiostatic control of the process from the anode (at +0.2 V vs SHE) to the cathode (at −0.65, −0.90 and −1.00 V vs SHE), along with the control of the fluid dynamic conditions of the anode chamber. An almost complete (99%) energy recovery was obtained by methane production with the cathode potential controlled at −0.65 V vs SHE. Finally, at the MEC cathode, current was utilized to reduce CO2 into CH4 (with a cathodic capture efficiency of about 70%) as well as to promote CO2 sorption into HCO3−. The latter represents the main CO2 removal mechanism that accounted for 85% of the CO2 removal.

Demonstration of 99% CO2 Removal from Coal Flue Gas by Amine Scrubbing

Abstract A post-combustion CO2 capture campaign was conducted at the National Carbon Capture Center (NCCC) with 5 m PZ (piperazine) using the advanced flash stripper configuration. 68 steady-state runs were identified and 90% or to 99.1% CO2 removal was achieved with a 12 m of packing in the absorber. A 20% increase in solvent rate enhanced CO2 removal from 90% to 99% and the rich loading decreased from 0.40 to 0.38 mol CO2/mol alkalinity. With high removal, the temperature profile from modeling indicated there was a mass transfer pinch in the absorber, which means 12 m packing is more than needed even for 99% removal. The rich loading did not decrease significantly at high CO2 removal, therefore the energy cost for regeneration remained practically unchanged. The material balance around the absorber based on CO2 loaded calculated from density and viscosity closed within 2.3%. The rate-based Aspen Plus® model under-predicted the number of transfer units in the absorber by an average of 16%. This was caused by the difference between CO2 concentration measured by titration and calculated from density and viscosity. With the advanced flash stripper (AFS), the process heat duty was between 1.9 and 2.5 GJ/t CO2 and did not increase more than 5% at higher CO2 removal. Due to the fast reaction kinetics of PZ, the 12 m absorber was overdesigned for 99% CO2 removal and the rich loading was unchanged at high removal. Further, the superior design of the AFS recovered the latent heat of water vapor and minimized the energy consumption for solvent regeneration. Therefore, it is feasible to capture 99% of the CO2 from coal-fired flue gas with PZ scrubbing at a reasonable energy cost.

Demonstration of 99% CO2 removal from coal flue gas by amine scrubbing

A post-combustion CO2 capture campaign was conducted at the National Carbon Capture Center (NCCC) with 5 m PZ (piperazine) using the advanced flash stripper configuration. 68 steady-state runs were identified and 90% or to 99.1% CO2 removal was achieved with a 12 m of packing in the absorber. A 20% increase in solvent rate enhanced CO2 removal from 90% to 99% and the rich loading decreased from 0.40 to 0.38 mol CO2/mol alkalinity. With high removal, the temperature profile from modeling indicated there was a mass transfer pinch in the absorber, which means 12 m packing is more than needed even for 99% removal. The rich loading did not decrease significantly at high CO2 removal, therefore the energy cost for regeneration remained practically unchanged.The material balance around the absorber based on CO2 loaded calculated from density and viscosity closed within 2.3%. The rate-based Aspen Plus® model under-predicted the number of transfer units in the absorber by an average of 16%. This was caused by the difference between CO2 concentration measured by titration and calculated from density and viscosity.With the advanced flash stripper (AFS), the process heat duty was between 1.9 and 2.5 GJ/t CO2 and did not increase more than 5% at higher CO2 removal. Due to the fast reaction kinetics of PZ, the 12 m absorber was overdesigned for 99% CO2 removal and the rich loading was unchanged at high removal. Further, the superior design of the AFS recovered the latent heat of water vapor and minimized the energy consumption for solvent regeneration. Therefore, it is feasible to capture 99% of the CO2 from coal-fired flue gas with PZ scrubbing at a reasonable energy cost.

Influence of liquid-to-biogas ratio and alkalinity on the biogas upgrading performance in a demo scale algal-bacterial photobioreactor

The influence of the liquid-to-biogas ratio (L/G) and alkalinity on methane quality was evaluated in a 11.7 m3 outdoors horizontal semi-closed tubular photobioreactor interconnected to a 45-L absorption column (AC). CO2 concentrations in the upgraded methane ranged from <0.1 to 9.6% at L/G of 2.0 and 0.5, respectively, with maximum CH4 concentrations of 89.7% at a L/G of 1.0. Moreover, an enhanced CO2 removal (mediating a decrease in CO2 concentration from 9.6 to 1.2%) and therefore higher CH4 contents (increasing from 88.0 to 93.2%) were observed when increasing the alkalinity of the AC cultivation broth from 42 ± 1 mg L−1 to 996 ± 42 mg L−1. H2S was completely removed regardless of the L/G or the alkalinity in AC. The continuous operation of the photobioreactor with optimized operating parameters resulted in contents of CO2 (<0.1%–1.4%), H2S (<0.7 mg m−3) and CH4 (94.1%–98.8%) complying with international regulations for methane injection into natural gas grids.

Anaerobic Digestion of Slaughterhouse Wastewater: CO&lt;sub&gt;2&lt;/sub&gt; Capture of Biogas Using &lt;i&gt;Chlorella vulgaris&lt;/i&gt;

Biogas quality from anaerobic digester influenced the combustion of biogas. A high percentage of CO2 in biogas indicates the low quality of biogas. Abatement of CO2 using microalgae, such as Chlorella vulgaris could enhance the quality of biogas. The aim of this research was to observe the ability of C. vulgaris on CO2 removal from slaughterhouse wastewater biogas. In this research, two anaerobic digesters were provided with the different condition of biogas collector bag. The first digester was combined with only biogas collector bag, while another digester was combined with C. Vulgaris. Slaughterhouse wastewater volume in each digester was 3.5 L. Observation time was 15 days and the samples were collected for every 5 days. The result showed that anaerobic digester was able to remove 63% of COD. Biogas composition of slaughterhouse wastewater after incubation for 15 days was 52.70% of air, 46.85% of CH4and 0.45% of CO2. C. Vulgaris enhanced CO2 removal from biogas up to 7%. The density of C. vulgaris decreased to 51 cell/mL. The biogas composition was probably influenced by the density of C. vulgaris.

Influence of water-film-forming-unit on the enhanced removal of carbon dioxide from mixed gas using water absorption apparatus

ABSTRACTThis research uses tap water to absorb carbon dioxide from mixed gas (N2 and CO2) in an absorption apparatus coupled with a water-film-forming-unit (WFFU). The objective is to assess the benefits of using a WFFU to enhance CO2 removal efficiency at low pressure conditions. Based on our results, the WFFU significantly improves CO2 capture at 0.30 MPa in a water absorption system with two WFFUs. The CO2 removal efficiency was 20% greater than for systems without WFFUs. Moreover, statistical data attained by the Taguchi analysis method showed that the number of WFFUs used in the absorption system has the greatest influence on CO2 removal efficiency (contribution percentage = 50.65%) compared to gas pressure, initial CO2 concentration, gas-to-liquid ratio, and liquid temperature. We also thoroughly investigated the effects of these factors on CO2 removal performance. The optimum conditions for CO2 removal efficiency in a system equipped with two WFFUs are low temperature, low gas-to-liquid ratio, low gas pressure (0.25–0.30 MPa), and high inlet CO2 concentration. These findings could provide an effective method for capturing CO2 from exhaust gases, and thus help mitigate global warming.

A Procedure for the Development of a Low-Cost Treatment Technology of Raw Biogas for Application in a Gas Engine. A Case of Sizing a Carbon Dioxide Removal Unit

A test laboratory (lab) for carbon dioxide (CO2) adsorption from raw biogas onto a novel adsorbent was used to size a CO2 removal unit in the development of a low-cost biogas treatment technology. The novel adsorbent was made out of clay and burnt maize cob particles, impregnated with hot natural alkaline solution of pH 10 ± 0.5, degassed, and then activated at a temperature of 250°C, thereby making it low cost. The activated absorbents were spherical balls of average diameter 17 mm, density 410 kg/m3, and surface area 128 m2/g, and contained exchangeable ions due to the presence of clay and increased pore sizes due to impregnation, degassing, and activation. The effect of pressure drops on CO2 removal, the breakthrough curve, and the absorption isotherm were studied. As a result, reduced pressure drops enhanced CO2 removal and 102 Pa/m was the suitable pressure drop; pressure drops less than 102 Pa/m were impractical because the biogas did not exit. The breakthrough curve was in typical s-shape and thus satisfied its use for determining the adsorption rate constant (k1) to be 0.001952 l/mg s and the maximum percent of CO2 removal to be 87.8% at 102 Pa/m pressure drop and temperatures ranging from 20 to 28°C. The isotherm was found to closely conform to the definition of the Freundlich equation with the Freundlich coefficient of 0.01809 (l/g)n, where n = 1.37 at the same temperature range. Therefore, the determined k1 and fitted Freundlich isotherm can be used to size the CO2 adsorption unit under these conditions.

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Abstract : Learning Objectives: ARDS remains a significant medical problem in ICU patients and requires mechanical ventilation which by itself may be injurious. ALCO2R is a unique strategy to reduce ventilator settings to minimize additional lung damage in patients with ARDS. We tested the hypothesis that ALCO2R does not induce an inflammatory response in target organs. Methods:Conscious spontaneously breathing sheep (n=6) were connected to a Hemolung (Alung Technologies, Pittsburgh, PA) membrane lung (ML) via heparin-coated tubing and a dual lumen catheter inserted in the right jugular vein. A hemofilter (Purema, Nx Stage Medical, Lawrence, MA) was set up in series after the ML with a pump for recirculation of ultrafiltrate and reinfusion before the ML. 1.5 mEq/min of lactic acid was infused into the ultrafiltrate to acidfy blood locally and enhance CO2 removal by the ML. Animals were subjected to ALCO2R or standard CO2 removal without acidification for 12 hr periods twice over a 48 hr period and each sheep served as its own control. Sheep were then euthanized and liver and lungs were flash frozen and analyzed for select indices of oxidative stress and cytokines. Results: The efficiency of CO2 removal was 70% higher during ALCO2R than without acid. Cardiac output and oxygen consumption were about 6 8% higher during ALCO2R than without acid. pHa was normal and lactate higher in ALCO2R and markers of kidney and liver function were within the normal range. Lung and liver indices of lipid peroxidation, antioxidant status, as well as glutathione levels and indices of nitrosative stress were similar to historic controls. Lung and liver IL-1 and IL-8 as markers of inflammation were not significantly elevated over the normal range in either tissue. Conclusions: Spontaneously breathing sheep subjected to ALCO2R were able to maintain ventilator status with improved efficiency in CO2 removal.