CO2 Enrichment Levels Research Articles

Computational investigations of enrichment effects for CO2 methanation in Sabatier microchannel reactors

The Sabatier micro-reactor for CO2 reduction through methanation, in manned mission applications, has gained a lot of interest due to higher yields of fuel and improved logistics. Three-dimensional (3D) computational fluid dynamics (CFD) calculations of flow, heat transfer and chemical reactions are performed here to understand and evaluate the potential of H2 and CO2 enrichment to increase the efficiency of the CO2 methanation in Sabatier microchannel reactors. The model is first validated by comparing calculations of the stoichiometrically-fueled reaction with previously conducted experiments at varying temperatures and pressures. A comprehensive set of studies at different H2 and CO2 enrichment levels, temperatures ranging from 200 to 400∘C and gauge pressures of 1 bar and 5 bar is carried out. Results show that yields and conversions of almost 100% are achievable with the highest H2 enrichment levels at the highest temperature and pressure tested here, with a desirable control of CO emission.

Carbon Dioxide Enrichment Combined with Supplemental Light Improve Growth and Quality of Plug Seedlings of Astragalus membranaceus Bunge and Codonopsis lanceolata Benth. et Hook. f.

Astragalus membranaceus Bunge and Codonopsis lanceolata Benth. et Hook. f. are two medicinal species used to remedy inflammation, tumor, and obesity in Eastern medicine. Carbon dioxide (CO2) and supplemental lighting are two methods to enhance the growth, yield, and quality of crops. However, few studies have focused on the synergistic effects of CO2 and the supplemental light source on plug seedlings of medicinal species. In this study, uniform seedlings were grown with no supplemental light (the control) or under one of three supplemental light sources [high pressure sodium (HPS), metal halide (MH), or mixed light-emitting diodes (LEDs)] combined with one of three levels of CO2 (350, 700, or 1050 μmol·mol−1). The supplemental light (100 μmol·m−2·s−1 photosynthetic photon flux density) and CO2 were provided simultaneously from 10:00 pm to 2:00 am every day. The results showed that the supplemental lighting (LEDs, MH, and HPS) greatly improved the seedling quality with greater dry weights (of the shoot, root, and leaf), stem diameter, leaf area, and Dickson’s quality index (DQI) than those of the control in both species. An enriched CO2 at 1050 μmol·mol−1 accelerated the growth and development of plug seedlings, evidenced by the increased root and leaf dry weights, stem diameter, and DQI compared to the those from the other two CO2 enrichment levels. Moreover, LEDs combined with 1050 μmol·mol−1 CO2 not only increased the contents of soluble sugars but also the starch content. However, an enriched CO2 at 700 μmol·mol−1 was more suitable for the accumulation of total phenols and flavonoids. Furthermore, LEDs combined with 700 or 1050 μmol·mol−1 CO2 increased the chlorophyll, quantum yield, and stomatal conductance at daytime and nighttime for A. membranaceus and C. lanceolata, respectively. In conclusion, the data suggest that LEDs combined with CO2 at 1050 μmol·mol−1 is recommended for enhancing the growth and development of plug seedlings of A. membranaceus and C. lanceolata.

Climatic role of terrestrial ecosystem under elevated CO2 : a bottom-up greenhouse gases budget.

The net balance of greenhouse gas (GHG) exchanges between terrestrial ecosystems and the atmosphere under elevated atmospheric carbon dioxide (CO2 ) remains poorly understood. Here, we synthesise 1655 measurements from 169 published studies to assess GHGs budget of terrestrial ecosystems under elevated CO2 . We show that elevated CO2 significantly stimulates plant C pool (NPP) by 20%, soil CO2 fluxes by 24%, and methane (CH4 ) fluxes by 34% from rice paddies and by 12% from natural wetlands, while it slightly decreases CH4 uptake of upland soils by 3.8%. Elevated CO2 causes insignificant increases in soil nitrous oxide (N2 O) fluxes (4.6%), soil organic C (4.3%) and N (3.6%) pools. The elevated CO2 -induced increase in GHG emissions may decline with CO2 enrichment levels. An elevated CO2 -induced rise in soil CH4 and N2 O emissions (2.76 Pg CO2 -equivalent year-1 ) could negate soil C enrichment (2.42 Pg CO2 year-1 ) or reduce mitigation potential of terrestrial net ecosystem production by as much as 69% (NEP, 3.99 Pg CO2 year-1 ) under elevated CO2 . Our analysis highlights that the capacity of terrestrial ecosystems to act as a sink to slow climate warming under elevated CO2 might have been largely offset by its induced increases in soil GHGs source strength.

CO2 enrichment and reduced seawater pH had no effect on the embryonic development of Acropora palmata (Anthozoa, Scleractinia).

The effects of decreased pH, caused by carbon dioxide (CO2) dissolution in seawater (known as ocean acidification (OA)), on the development of newly fertilized eggs of the Caribbean reef-building coral, Acropora palmata, was tested in three experiments conducted during the summers of 2008 and 2009 (two repeats). Three levels of CO2 enrichment were used: present day conditions (400 µatm, pH 8.1) and two CO2-enriched conditions (700 µatm, pH 7.9, and 1000 µatm, pH 7.7). No effects on the progression or timing of development, or embryo and larval size, were detected in any of the three experimental runs. The results show that the embryos and larvae of A. palmata are able to develop normally under seawater pH of at least 0.4 pH units lower than the present levels. Acropora palmata larvae do not usually begin to calcify after settlement, so this study only examined the non-calcifying part of the life cycle of this species. Most of the concern about the effects of OA on marine organisms centers on its effect on calcification. Negative effects of OA on the embryonic development of this species were not found and they may not manifest until the newly settled polyps begin to calcify.

Impact of Elevated Carbon Dioxide on Primary, Secondary Metabolites and Antioxidant Responses of Eleais guineensis Jacq. (Oil Palm) Seedlings

A split plot 3 by 3 experiment was designed to investigate the relationships among production of primary metabolites (soluble sugar and starch), secondary metabolites (total flavonoids, TF; total phenolics, TP), phenylalanine lyase (PAL) activity (EC 4.3.1.5), protein and antioxidant activity (FRAP) of three progenies of oil palm seedlings, namely Deli AVROS, Deli Yangambi and Deli URT, under three levels of CO2 enrichment (400, 800 and 1,200 µmol·mol−1) for 15 weeks of exposure. During the study, the treatment effects were solely contributed by CO2 enrichment levels; no progenies and interaction effects were observed. As CO2 levels increased from 400 to 1,200 µmol·mol−1, the production of carbohydrate increased steadily, especially for starch more than soluble sugar. The production of total flavonoids and phenolics contents, were the highest under 1,200 and lowest at 400 µmol·mol−1. It was found that PAL activity was peaked under 1,200 µmol·mol−1 followed by 800 µmol·mol−1 and 400 µmol·mol−1. However, soluble protein was highest under 400 µmol·mol−1 and lowest under 1,200 µmol·mol−1. The sucrose/starch ratio, i.e., the indication of sucrose phosphate synthase actvity (EC 2.4.1.14) was found to be lowest as CO2 concentration increased from 400 > 800 > 1,200 µmol·mol−1. The antioxidant activity, as determined by the ferric reducing/antioxidant potential (FRAP) activity, increased with increasing CO2 levels, and was significantly lower than vitamin C and α-tocopherol but higher than butylated hydroxytoluene (BHT). Correlation analysis revealed that nitrogen has a significant negative correlation with carbohydrate, secondary metabolites and FRAP activity indicating up-regulation of production of carbohydrate, secondary metabolites and antioxidant activity of oil palm seedling under elevated CO2 was due to reduction in nitrogen content in oil palm seedling expose to high CO2 levels.

Increased carbon dioxide concentration improves the antioxidative properties of the Malaysian herb kacip fatimah (Labisia pumila Blume).

A randomized complete randomized design (RCBD) 3 by 3 experiment was designed to investigate and distinguish the relationships among production of secondary metabolites (total phenolics, TP; total flavonoids, TF), gluthatione (GSH), oxidized gluthatione (GSSG), soluble carbohydrate and antioxidant activities of the Malaysian medicinal herb Labisia pumila Blume under three levels of CO2 enrichment (400, 800 and 1,200 µmol mol−1) for 15 weeks. It was found that the treatment effects were solely contributed by interaction of CO2 levels and secondary metabolites distribution in plant parts, GSH, GSHH and antioxidant activities (peroxyl radicals (ROO), superoxide radicals (O2), hydrogen peroxide (H2O2) and hydroxyl radicals (OH). The records of secondary metabolites, glutahione, oxidized gluthathione and antioxidant activities in a descending manner came from the leaf enriched with 1,200 µmol/mol CO2 > leaf 800 µmol/mol CO2 > leaf 400 µmol/mol CO2 > stem 1,200 µmol/mol CO2 > stem 800 µmol/mol CO2 > stem 400 µmol/mol CO2 > root 1,200 µmol/mol CO2 > root 800 µmol/mol CO2 > root 400 µmol/mol CO2. Correlation analyses revealed strong significant positive coefficients of antioxidant activities with total phenolics, flavonoids, GSH and GSHH indicating that an increase in antioxidative activity of L. pumila under elevated CO2 might be up-regulated by the increase in production of total phenolics, total flavonoids, GSH, GSHH and soluble sugar. This study implied that the medicinal potential of herbal plant such as L. pumila can be enhanced under elevated CO2, which had simultaneously improved the antioxidative activity that indicated by the high oxygen radical absorbance activity against ROO, O2, H2O2, and OH radicals.

Enhancement of Leaf Gas Exchange and Primary Metabolites under Carbon Dioxide Enrichment Up-Regulates the Production of Secondary Metabolites in Labisia pumila Seedlings

A split plot 3 by 3 experiment was designed to investigate and distinguish the relationships among production of primary metabolites (soluble sugar and starch), secondary metabolites (total phenolics, TP; total flavonoids, TF) and leaf gas exchange of three varieties of the Malaysian medicinal herb Labisia pumila Blume, namely the varieties alata, pumila and lanceolata, under three levels of CO2 enrichment (400, 800 and 1,200 µmol mol−1) for 15 weeks. The treatment effects were solely contributed by CO2 enrichment levels; no varietal differences were observed. As CO2 levels increased from 400 to 1,200 µmol mol−1, the production of carbohydrates also increased steadily, especially for starch more than soluble sugar (sucrose). TF and TP content, simultaneously, reached their peaks under 1,200 µmol exposure, followed by 800 and 400 µmol mol−1. Net photosynthesis (A) and quantum efficiency of photosystem II (fv/fm) were also enhanced as CO2 increased from 400 to 1,200 µmol mol−1. Leaf gas exchange characteristics displayed a significant positive relationship with the production of secondary metabolites and carbohydrate contents. The increase in production of TP and TFs were manifested by high C/N ratio and low protein content in L. pumila seedlings, and accompanied by reduction in cholorophyll content that exhibited very significant negative relationships with total soluble sugar, starch and total non structural carbohydrate.

Physiological characterisation of two rose (Rosa hybrida L.) cultivars grown under different levels of CO2 enrichment

SummaryThe rose cultivars ‘Arjun’ (indigenous) and ‘First Red’ (exotic) were grown in a phytotron and exposed to 370 (ambient), 1,000, or 1,500 µmol mol−1 CO2 to study their physiological response in relation to CO2 enrichment. ‘Arjun’, grown under 1,000 µmol mol−1 CO2 achieved a maximum height of 95.0 cm, compared to 83.3 cm under ambient CO2. The total number of leaves and leaf area were highest at 1,500 µmol mol−1 CO2 in both cultivars. Photosynthesis, chlorophyll concentration, and specific leaf weight (SLW) were measured at the flowering stage. Maximum photosynthetic rates were achieved at 1,000 µmol mol−1 CO2 (11.59 and 10.42 µmol CO2 m−2 s−1 in ‘Arjun’ and ‘First Red’, respectively), compared to 3.66 and 4.96 µmol m−2 s−1, respectively at ambient CO2 levels. Chlorophyll a, chl b, and total chlorophyll concentrations in leaves increased in both cultivars at 1,500 µmol mol−1 CO2, while chl a/b ratios decreased due to CO2 enrichment. SLW was higher in both cultivars at 1,000 µmol mol−1 CO2 compared to ambient CO2. Root dry weight was significantly higher at 1,000 µmol mol−1 CO2 in both cultivars than at ambient CO2, whereas root volume was maximum (28.2 cm3/plant) in ‘First Red’ at 1,500 µmol mol−1 CO2 compared to ‘Arjun’ (23.3 cm3/plant). Cultivar CO2 interactions were also significant for all parameters measured.The indigenous rose cultivar ‘Arjun’ responded positively in terms of growth and photosynthetic rate to CO2 enrichment under optimum growing conditions. Physiological characterisation can thus provide useful information to select rose cultivars to be grown under modified environments to achieve their maximum yield potential.

The microfood web of grassland soils responds to a moderate increase in atmospheric CO2

AbstractThe response of the soil microfood web (microflora, nematodes) to a moderate increase in atmospheric CO2 (+20%) was investigated by means of a free air CO2 enrichment experiment. The study was carried out in a seminatural temperate grassland for a period of 4 consecutive years (1 year before fumigation commenced and 3 years with fumigation). Several soil biological parameters showed no change (microbial biomass, bacterial biomass) or decline (microbial respiration) in the first year of elevated CO2 treatment as compared with controls. Each of these parameters were higher than controls, however, after 3 years of treatment. The relative abundance of predaceous nematodes also decreased in year 1 of the experiment, increased in year 2, but decreased again in year 3. In contrast, the relative abundance of root hair feeding nematodes, at first, increased under elevated CO2 and then returned to the initial level again. Increased microbial biomass indicates enhanced C storage in the labile carbon pool of the active microfood web in subsequent years. According to measurements on the amounts of soil extractable C, changes in resource availability seem to be key to the response of the soil microfood web.We found a strong response of bacteria to elevated CO2, while the fungal biomass remained largely unchanged. This contrasts to findings reported in the literature. We hypothesize that this may be because of contrasting effects of different levels of CO2 enrichment on the microbial community (i.e. stimulation of bacteria at moderate levels and stimulation of fungi at high levels of CO2 enrichment). However, various CO2 effects observed in our study are similar in magnitude to those observed in other studies for a much higher level of atmospheric carbon. These include the particular sensitivity of predaceous nematodes and the long‐term increase of microbial respiration. Our findings confirm that the potential of terrestrial ecosystems to accumulate additional carbon might be lower than previously thought. Furthermore, CO2‐induced changes of temperate grassland ecosystems might emerge much earlier than expected.

New contributions to propagation of pineapple (Ananas comosus L. Merr) in temporary immersion bioreactors

Plantlets propagated in temporary immersion bioreactors (TIB) have better performance than those propagated by conventional methods such as micropropagation. This is as a result of a better handling of the in vitro atmosphere and the nutrition. The object of this study to further improve the cultivation conditions by introducting photomixotrophism as an intermediate link of photoautotrophic growth during ex vitro acclimatization. For this purpose the effects of light were evaluated by different parameters such as photosynthetic photon flux density (PPF), sucrose concentration, and CO2 enrichment levels on CO2 evolution inside the culture vessels. It was observed that CO2 diminished upon light exposure and increased in the dark according to the photoperiod during each cycle of immersion. With this approach it was possible to increase the photomixotrophism in the pineapple plantlets propagated in TIB. It was demonstrated that light is the factor with more influence on plant quality, although under these conditions they seem to use more of the nutrients of the medium than their photoassimilates. The propagation of pineapple in TIB involves three phases: proliferation, pre-elongation, and final growth of the buds. In each phase the cultivation conditions were determined to substitute for sterilization by autoclaving, to improve the quality of the plants, to elevate the efficiency of the process, and to reduce production costs. The buds that grew in the temporary immersion bioreactor with the presence of Vitrofural (G-1) achieved the best indicators of growth. Significant increases were observed in the leaf area, dry mass of the buds, and chlorophyll contents.

Soil carbon CO2fertilization factor: The measure of an ecosystem's capacity to increase soil carbon storage in response to elevated CO2levels

This research introduces the concept of a “CO2fertilization factor for soil carbon” (σCF). The σCFis a measure of an ecosystem's capacity to increase soil carbon storage in response to elevated carbon dioxide levels. This paper describes the mathematical derivation of σCFand illustrates how σCFcan be determined experimentally, using data from a white oak study. I have developed this concept to compare the results of carbon dioxide enrichment experiments having different soil carbon turnover times, different levels of CO2enrichment, and different lengths of exposure to elevated carbon dioxide levels. The σCFcan also be used to estimate increases in soil carbon uptake due to observed contemporary increases in atmospheric carbon dioxide levels. Although the approach used here may seem oversimplified, I present it as a simple way of estimating the extent to which elevated levels of CO2could increase soil carbon storage. I have determined a σCFof 1.18 for a white oak ecosystem using soil carbon and radiocarbon measurements. If major terrestrial ecosystems have similar σCFvalues, CO2fertilization may be transferring enough carbon from the atmosphere to soil to balance the global carbon budget.

The effects of propagation temperature, CO2concentration and early post-harvest night temperature on the fruit yield of January-sown cucumbers

SummaryGrowth and fruiting responses of four January-sown cucumber cultivars to two propagation temperatures (day 21°C, night 19°C and day 24°C, night 17°C), three levels of CO2 enrichment (400, 1000 and 1600 vpm) and three stages of post-planting night temperature reduction (0, 3 and 6 weeks after first harvest) were examined in a glasshouse experiment. Early (4-week) fruit yield and monetary returns were significantly increased when the higher day temperature treatment was combined with the 1600 vpm CO2. The early advantage was soon lost and after 20 weeks harvesting there were no differences between the propagation temperature treatments. After two weeks of CO2 treatment total dry weight of aerial parts, leaf area and stem length were increased by 88, 73 and 69% respectively when the CO2 level was raised from 400 to 1000 vpm. A further rise from 1000 to 1600 vpm produced no further increases indicating that 1000 vpm is probably near the optimum concentration for growth at the temperatures applied. In the early (4-week) harvest period, fruit yield and gross monetary returns increased by c. 30% when CO2 was raised from 400 to 1000 vpm but there was little or no difference between plants grown in 1000 or 1600 vpm. The early yield advantage from enrichment at 1000 vpm CO2 was maintained throughout the season (20 weeks of harvesting). The most economic level of CO2 enrichment for January-sown cucumbers was c. 1000 vpm. Lowering night temperature at the start of harvesting reduced fruit yield and monetary value compared with lowering the temperature 3 or 6 weeks after fruit picking commenced. The estimated savings in fuel from this treatment were too small to offset the loss of revenue from the crop. The most economic time to reduce night temperature in the January-sown crop was 3 weeks after the start of harvesting.