Biological Sequestration Research Articles

Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age

The Southern Ocean regulates the ocean's biological sequestration of CO2 and is widely suspected to underpin much of the ice age decline in atmospheric CO2 concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the 15N/14N of fossil-bound organic matter in the stony deep-sea coral Desmophyllum dianthus, a tool for reconstructing surface ocean nutrient conditions. The central robust observation is of higher 15N/14N across the Southern Ocean during the Last Glacial Maximum (LGM), 18-25 thousand years ago. These data suggest a reduced summer surface nitrate concentration in both the Antarctic and Subantarctic Zones during the LGM, with little surface nitrate transport between them. After the ice age, the increase in Antarctic surface nitrate occurred through the deglaciation and continued in the Holocene. The rise in Subantarctic surface nitrate appears to have had both early deglacial and late deglacial/Holocene components, preliminarily attributed to the end of Subantarctic iron fertilization and increasing nitrate input from the surface Antarctic Zone, respectively.

Carbon dioxide (CO2) biofixation by microalgae and its potential for biorefinery and biofuel production.

Carbon dioxide (CO2) using biological process is one of the promising approaches for CO2 capture and storage. Recently, biological sequestration using microalgae has gained many interest due to its capability to utilize CO2 as carbon source and biomass produced can be used as a feedstock for other value added product for instance biofuel and chemicals. In this study, the CO2 biofixation by two microalgae species, Chlorella sp. and Tetraselmis suecica was investigated using different elevated CO2 concentration. The effect of CO2 concentration on microalgae growth kinetic, biofixation and its chemical composition were determined using 0.04, 5, 15 and 30% CO2. The variation of initial pH value and its relationship on CO2 concentration toward cultivation medium was also investigated. The present study indicated that both microalgae displayed different tolerance toward CO2 concentration. The maximum biomass production and biofixation for Chlorella sp. of 0.64gL-1 and 96.89mgL-1d-1 was obtained when the cultivation was carried out using 5 and 15% CO2, respectively. In contrast, the maximum biomass production and CO2 biofixation for T. suecica of 0.72gL-1 and 111.26mgL-1d-1 were obtained from cultivation using 15 and 5% CO2. The pH value for the cultivation medium using CO2 was between 7.5 and 9, which is favorable for microalgal growth. The potential of biomass obtained from the cultivation as a biorefinery feedstock was also evaluated. An anaerobic fermentation of the microalgae biomass by bacteria Clostridium saccharoperbutylacenaticum N1-4 produced various type of value added product such as organic acid and solvent. Approximately 0.27 and 0.90gL-1 of organic acid, which corresponding to acetic and butyric acid were produced from the fermentation of Chlorella sp. and T. suecica biomass. Overall, this study suggests that Chlorella sp. and T. suecica are efficient microorganism that can be used for CO2 biofixation and as a feedstock for chemical production.

An informatics-based analysis of developments to date and prospects for the application of microalgae in the biological sequestration of industrial flue gas.

The excessive emission of flue gas contributes to air pollution, abnormal climate change, global warming, and sea level rises associated with glacial melting. With the ability to utilize NOx as a nitrogen source and to convert solar energy into chemical energy via CO2 fixation, microalgae can potentially reduce air pollution and relax global warming, while also enhancing biomass and biofuel production as well as the production of high-value-added products. This informatics-based review analyzes the trends in the related literature and in patent activity to draw conclusions and to offer a prospective view on the developments of microalgae for industrial flue gas biosequestration. It is revealed that in recent years, microalgal research for industrial flue gas biosequestration has started to attract increasing attention and has now developed into a hot research topic, although it is still at a relatively early stage, and needs more financial and policy support in order to better understand microalgae and to develop an economically viable process. In comparison with onsite microalgal CO2 capture, microalgae-based biological DeNOx appears to be a more realistic and attractive alternative that could be applied to NOx treatment.

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Seasonal variations, origin, and fate of settling diatoms in the Southern Ocean tracked by silicon isotope records in deep sediment traps

AbstractThe Southern Ocean plays a pivotal role in the control of atmospheric CO2 levels, via both physical and biological sequestration processes. The biological carbon transfer to the ocean interior is tightly coupled to the availability of other elements, especially iron as a trace‐limiting nutrient and dissolved silicon as the mineral substrate that allows diatoms to dominate primary production. Importantly, variations in the silicon cycling are large but not well understood. Here we use δ30Si measurements to track seasonal flows of silica to the deep sea, as captured by sediment trap time series, for the three major zones (Antarctic, AZ; Polar Frontal, PFZ; and Sub‐Antarctic, SAZ) of the open Southern Ocean. Variations in the exported flux of biogenic silica (BSi) and its δ30Si composition reveal a range of insights, including that (i) the sinking rate of BSi exceeds 200 m d−1 in summer in the AZ yet decreases to very low values in winter that allow particles to remain in the water column through to the following spring, (ii) occasional vertical mixing events affect the δ30Si composition of exported BSi in both the SAZ and AZ, and (iii) the δ30Si signature of diatoms is well conserved through the water column despite strong BSi and particulate organic carbon (POC) attenuation at depth and is closely linked to the Si consumption in surface waters. With the strong coupling observed between BSi and POC fluxes in PFZ and AZ, these data provide new constraints for application to biogeochemical models of seasonal controls on production and export.

Biological sequestration and retention of cadmium as CdS nanoparticles by the microalga Scenedesmus-24

Biological sequestration of cadmium (Cd) and retention of adsorbed cadmium as cadmium sulphide (CdS) nanoparticles inside the cell by a lipid-producing green algae Scenedesmus-24 is reported. The microalga was able to grow in the growth media containing 30 mg L−1 of cadmium without any growth inhibition. Adsorption of Cd(II) was dependent on the pH of the medium, initial concentration of cadmium, density of algal biomass (biosorbent dose), and contact time. The adsorption follows Langmuir isotherm pattern with an estimated maximum cadmium adsorption capacity at 50 mg g−1. The kinetics of adsorption followed Lagergren’s pseudo-second-order model. FTIR analysis revealed the presence of different functional groups on the algal biomass which may be responsible for adsorption of Cd(II). After adsorption, the bound metal ions were retained in the microalgal biomass as CdS nanoparticles. Presence of CdS nanoparticle was confirmed by XRD and TEM analysis. The results of the present study conclusively demonstrate that the microalga Scenedesmus-24 may be a promising candidate for sequestration of cadmium from cadmium polluted water and also its recovery as precious CdS nanoparticles.

Algae as biofuel

The combustion of fossil fuels contributes to climate change by introducing greenhouse gases to the atmosphere, and the need for an alternative fuel source is increasingly important. Biomass, either terrestrial or aquatic is considered a potential renewable energy source for biofuel production. Microalgae or seaweed (Macroalgae) are considered superior compared with terrestrial plants – in terms of solar energy storage, nutrient assimilation and potential for biofuel production – due to their higher photosynthetic efficiency, higher biomass yield and rates. The use of algae for biofuel production is expected to play an important role in securing energy supply in the next decades. For example, not only in the processing of those algae directly related to biofuels production but also in the possibility of combining this processing with pollution control, in particular with biological sequestration of CO2 emissions and other greenhouse gases, or wastewater treatment. Energy from biomass (biological, including biofuels and non-biological processes including gasification, combustion, and so on) is expected to provide more than a half share of the total energy to achieve the desired target. The various aspects associated with the design of algae production units are described in this paper, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented in this paper – for example applications in teh biological sequestration of CO2 and in wastewater treatment. In addition, the use of microalgae as food additives and for aquaculture is also discussed.

Bio-sequestration of CO2 Using Carbonic Anhydrase in situ Encapsulated Inside Electrospun Hollow Fibers

Carbonic anhydrase catalyzed bio-sequestration of CO2 to form HCO3-, followed by trapping as solid CaCO3 is one of the most promising technologies for CO2 capturing. The effects of reaction condition on the CO2 hydration using free carbonic anhydrase were systematically investigated. In order to improve the stability of the enzyme and facility its recycling, the carbonic anhydrase was in situ encapsulated inside hollow fibers via a novel co-axial electrospinning technology. Compared with the free enzyme, the immobilized carbonic anhydrase showed much improved thermal stability and suffered much reduced inhibitory effects from cation ions, such as Cu2+ and Fe3+. After 11 reuses, the immobilized enzyme retained about 81.9% of its original activity by comparing the amount of formed CaCO3 precipitation. In the presence of immobilized carbonic anhydrase, both calcite and vaterite CaCO3 solid were formed; while in the absence of enzyme or with free carbonic anhydrase, only calcite CaCO3 was observed.

Synthesis of observed air–sea CO<sub>2</sub> exchange fluxes in the river-dominated East China Sea and improved estimates of annual and seasonal net mean fluxes

Abstract. Limited observations exist for a reliable assessment of annual CO2 uptake that takes into consideration the strong seasonal variation in the river-dominated East China Sea (ECS). Here we explore seasonally representative CO2 uptakes by the whole East China Sea derived from observations over a 14-year period. We firstly identified the biological sequestration of CO2 taking place in the highly productive, nutrient-enriched Changjiang River plume, dictated by the Changjiang River discharge in warm seasons. We have therefore established an empirical algorithm as a function of sea surface temperature (SST) and Changjiang River discharge (CRD) for predicting sea surface pCO2. Syntheses based on both observations and models show that the annually averaged CO2 uptake from atmosphere during the period 1998–2011 was constrained to about 1.8 ± 0.5 mol C m−2 yr−1. This assessment of annual CO2 uptake is more reliable and representative, compared to previous estimates, in terms of temporal and spatial coverage. Additionally, the CO2 time series, exhibiting distinct seasonal pattern, gives mean fluxes of −3.7 ± 0.5, −1.1 ± 1.3, −0.3 ± 0.8 and −2.5 ± 0.7 mol C m−2 yr−1 in spring, summer, fall and winter, respectively, and also reveals apparent interannual variations. The flux seasonality shows a strong sink in spring and a weak source in late summer–mid-fall. The weak sink status during warm periods in summer–fall is fairly sensitive to changes of pCO2 and may easily shift from a sink to a source altered by environmental changes under climate change and anthropogenic forcing.

Filtering fens: Mechanisms explaining phosphorus-limited hotspots of biodiversity in wetlands adjacent to heavily fertilized areas

The conservation of biodiverse wetland vegetation, including that of rich fens, has a high priority at a global scale. Although P-eutrophication may strongly decrease biodiversity in rich fens, some well-developed habitats do still survive in highly fertilized regions due to nutrient filtering services of large wetlands. The occurrence of such nutrient gradients is well-known, but the biogeochemical mechanisms that determine these patterns are often unclear. We therefore analyzed chemical speciation and binding of relevant nutrients and minerals in surface waters, soils and plants along such gradients in the large Ramsar nature reserve Weerribben-Wieden in the Netherlands.P-availability was lowest in relatively isolated floating rich fens, where plant N:P ratios indicated P-limitation. P-limitation can persist here despite high P-concentrations in surface waters near the peripheral entry locations, because only a small part of the P-input reaches the more isolated waters and fens. This pattern in P-availability appears to be primarily due to precipitation of Fe-phosphates, which mainly occurs close to entry locations as indicated by decreasing concentrations of Fe- and Al-bound P in the sub-aquatic sediments along this gradient. A further decrease of P-availability is caused by biological sequestration, which occurs throughout the wetland as indicated by equal concentrations of organic P in all sub-aquatic sediments.Our results clearly show that the periphery of large wetlands does indeed act as an efficient P-filter, sustaining the necessary P-limitation in more isolated parts. However, this filtering function does harm the ecological quality of the peripheral parts of the reserve. The filtering mechanisms, such as precipitation of Fe-phosphates and biological uptake of P, are crucial for the conservation and restoration of biodiverse rich fens in wetlands that receive eutrophic water from their surroundings. This seems to implicate that biodiverse wetland vegetation requires larger areas, as long as eutrophication has not been seriously tackled.

DNA assembly of nanoparticle superstructures for controlled biological delivery and elimination

The assembly of nanomaterials using DNA can produce complex nanostructures, but the biological applications of these structures remain unexplored. Here we describe the use of DNA to control the biological delivery and elimination of inorganic nanoparticles by organizing them into colloidal superstructures. The individual nanoparticles serve as building blocks, whose size, surface chemistry, and assembly architecture dictate overall superstructure design. These superstructures interact with cells and tissues as a function of their design, but subsequently degrade into building blocks that can escape biological sequestration. We demonstrate that this strategy reduces nanoparticle retention by macrophages and improves their in vivo tumour accumulation and whole-body elimination. Superstructures can be further functionalized to carry and protect imaging or therapeutic agents against enzymatic degradation. These results suggest a new strategy to engineer nanostructure interactions with biological systems and highlight new directions in the design of biodegradable and multifunctional nanomedicine.

Sequestration of atmospheric Carbon dioxide by microbial carbonic anhydrase

The increase in atmospheric concentrations of carbon dioxide contributes to global warming to a large extent. In this context biological sequestration of carbon dioxide hold promise as a means for addressing this problem. In the present study atmospheric carbon dioxide sequestration is achieved with the help of carbonic anhydrase produced by Bacillus schlegelii. A maximum activity of 0.0453 µ mol/ml/min was observed at pH 9 and 37 0 C. The enzyme was active up to 70 0 C.

Influence of enzyme concentration on bio-sequestration of CO2 in carbonate form using bacterial carbonic anhydrase

One of the most promising biological sequestration technologies of CO2 is the enzyme catalyzed CO2 sequestration into stable and environmentally friendly mineral carbonates. The present manuscript focused on the biocatalytic precipitation of CaCO3 by extracellular carbonic anhydrase (CA) which was extracted and purified from the culture of Bacillus cereus. The kinetics of CaCO3 precipitation catalyzed by the bacterial CA in the presence of different enzyme concentrations was investigated through the gaseous diffusion system. The polymorph and morphology of CaCO3 crystals obtained in the precipitation process were also analyzed using XRD, FTIR and FESEM. The results showed that the change in the amount of deposited Ca2+ during the process of CaCO3 precipitation catalyzed by bacterial CA of different concentrations was well fitted with the exponential model. The enzyme concentrations of 0.2–2.0U/mL were beneficial to CaCO3 precipitation, however, overhigh enzyme concentration (8.0U/mL) was not conducive to CaCO3 precipitation. The integrated results of XRD, FTIR and FESEM analysis showed that there were significant differences in the morphologies of CaCO3 crystals among different enzyme concentrations. Vaterite was present at the lower concentration of CA, and the higher concentration of CA favored the formation of calcite. Therefore, different polymorphs and morphologies of CaCO3 crystals can be produced in the presence of different concentrations of CA. Furthermore, the role of bacterial CA in CaCO3 precipitation was related to the electrostatic adsorption of Ca2+ on CA enzyme protein and the preferential adsorption of CA enzyme protein on the crystal faces, in addition to the enzymatic catalysis.

Crystallographic snapshots of metalloenzyme complexes involved in biological carbon dioxide sequestration

The Wood‐Ljungdahl pathway in acetogenic bacteria involves nine enzymes working together to convert two molecules of carbon dioxide and coenzyme A into acetyl‐CoA, which can subsequently be assimilated as cell carbon or converted to other products such as acetate or ethanol or butanol, depending on the acetogenic strain. Harnessing the ability of acetogens to produce commercially useful multicarbon compounds from carbon dioxide has long been of interest to the biotechnology community. The Drennan laboratory, in collaboration with the Ragsdale group, has solved crystal structures of metalloenzymes of this pathway, both alone and in complex, in order to gain mechanistic insight into the chemistry involved in these remarkable transformations, as well as to understand the molecular movements that allow these enzymes to act in concert. From structures of carbon monoxide dehydrogenase in complex with acetyl‐CoA synthase, we have obtained molecular pictures indicating how a unique Ni‐Fe‐S cluster can carry out reduction of carbon dioxide. From structures of our methyltransferase complexes, we have visualized the molecular movements that must occur for one‐carbon units to be passed from enzyme to enzyme.

CO2uptake in the East China Sea relying on Changjiang runoff is prone to change

[1] Limited knowledge exists concerning the unusually large CO2 uptake capacity in the East China Sea (ECS), which is the eminent continental shelf pump for efficient transfer of atmospheric CO2 to the deep ocean. Here we show evidence of strong control of river runoff on the CO2uptake capacity of the ECS. From 8-years of observations in the productive ECS shelf, we present the first dataset to show the complete seasonal cycle of CO2 flux, which gives an annual flux of 2.3 ± 0.4 mol C m−2 y−1 as a net sink of atmospheric CO2. Further, we found biological sequestration of CO2 taking place in the highly productive Changjiang river plume in warm seasons due to the riverine nutrient enrichment. Consequently, changes in the plume area due to changes in the Changjiang River Discharge (referred to as the Discharge hereafter) strongly affect the CO2 uptake capacity. As the Discharge may decrease due to the Three Gorges Dam operation, the Changjiang plume will probably also decrease, resulting in reduction in CO2 uptake capacity and even a shift from a CO2 sink to a source.

Managing Climate Change Through Biological Sequestration: Open Space Law Redux

Climate change management involves strategies that mitigate its causes and adapt human communities to its consequences. This article describes a legal strategy that does both: a national biological sequestration policy. This policy will increase the amount of carbon dioxide emissions that biological sequestration currently removes from the atmosphere and will enable human settlements to adapt to the harsh effects of a changing climate, while realizing a number of other objectives that open space preservation achieves. The article sketches the influences of international and national climate change law, which largely ignore the benefits of biological sequestration on privately owned land in developed countries. It then turns to an analysis of climate change and its consequences before exploring how mitigation and adaptation can be accomplished by preserving and enhancing the natural landscape in both rural and urban areas. Open Space Law presents policy makers with readily available tools to protect the sequestering environment: the natural and man-made landscapes that capture and store carbon organically and provide ecosystem resiliency. This body of law has emerged spontaneously over the past few decades, responding to countless local perturbations, largely unaided by cogent federal strategies. The local and state initiatives that have evolved to preserve and enhance open space provide the basis for a broader sequestration policy, one that builds on available legal technology and existing norms to respond to the looming global perturbation of climate change.

Temperature and nutrient stoichiometry interactively modulate organic matter cycling in a pelagic algal–bacterial community

A microcosm experiment was conducted to investigate the interactive effects of rising sea‐surface temperature and altered nutrient stoichiometry on the biogeochemical cycling of organic matter in a pelagic algal–bacterial assemblage. Natural seawater, containing a mixed bacterial community, was inoculated with an axenic culture of the bloom‐forming diatom species Skeletonema costatum. A factorial combination of three temperatures, simulating weak to strong warming as projected for the end of the 21st century, and either nitrogen (N)‐replete or ‐deficient growth conditions were applied. Depending on the type of nutrient limitation, the mixed algal–bacterial communities displayed pronounced differences in the accumulation and microbial utilization of organic matter in response to warming. Under N‐deficient conditions, the build‐up of organic matter occurred, irrespective of temperature, dominantly in the particulate pool, and only small amounts of dissolved material accumulated. The subsequent bacterial consumption of organic matter was low, as indicated by measurements of bacterial secondary production and extracellular enzyme activities, and remained also largely unaffected by an increase in temperature from 4°C up to 12°C. Contrastingly, warming resulted in a distinct temperature‐dependent increase in the accumulation of dissolved organic carbon compounds under N‐replete growth conditions. Moreover, rising temperature notably stimulated the bacterial activity, indicating an enhanced flow of organic matter through the microbial loop. These findings suggest that there will be strong shifts in the biogeochemical cycling of organic matter in the upper ocean in response to increased temperature and nutrient loading that will affect pelagic food‐web structures and the biological sequestration of organic matter.

Legal issues in carbon farming: Biosequestration, carbon pricing, and carbon rights

This paper critically analyses the proposed Australian regulatory approach to the crediting of biological sequestration activities (biosequestration) under the Australian Carbon Farming Initiative and its interaction with state-based carbon rights, the national carbon-pricing mechanism, and the international Kyoto Protocol and carbon-trading markets. Norms and principles have been established by the Kyoto Protocol to guide the creation of additional, verifiable, and permanent credits from biosequestration activities. This paper examines the proposed arrangements under the Australian Carbon Farming Initiative and Carbon Pricing Mechanism to determine whether they are consistent with those international norms and standards. This paper identifies a number of anomalies associated with the legal treatment of additionality and permanence and issuance of carbon credits within the Australian schemes. In light of this, the paper considers the possible legal implications for the national and international transfer, surrender and use of these offset credits.

Legal issues in carbon farming: Biosequestration, carbon pricing, and carbon rights

This paper critically analyses the proposed Australian regulatory approach to the crediting of biological sequestration activities (biosequestration) under the Australian Carbon Farming Initiative and its interaction with state-based carbon rights, the national carbon-pricing mechanism, and the international Kyoto Protocol and carbon-trading markets. Norms and principles have been established by the Kyoto Protocol to guide the creation of additional, verifiable, and permanent credits from biosequestration activities. This paper examines the proposed arrangements under the Australian Carbon Farming Initiative and Carbon Pricing Mechanism to determine whether they are consistent with those international norms and standards. This paper identifies a number of anomalies associated with the legal treatment of additionality and permanence and issuance of carbon credits within the Australian schemes. In light of this, the paper considers the possible legal implications for the national and international transfer, surrender and use of these offset credits.

Biological sequestration of carbon dioxide in geological formations

This paper presents the results of experimental investigation and analysis of challenges for utilizing enzyme bovine carbonic anhydrase for sequestration of CO 2 in saline formations. Several sets of controlled bench-top experiments were conducted, and results are presented in this paper, where effects of various parameters including pH, concentration of enzyme, and temperature on enhancing hydration and subsequent precipitation of CO 2 in the form of calcium carbonate were tested. A mathematical model describing the extent and rate of precipitation was developed upon analyzing the results of these tests. Subsequently, core flood tests were conducted where effect of enzyme on precipitation of CO 2 in Berea cores, and its impact on porosity and permeability of the porous media were investigated. These tests indicated that the pressure drop across cores was increased about 2–4 times, which is an indication of precipitation of CO 2 in the form of calcium carbonate in porous media. In addition to above tests, effect of timing and scheme of the injection on extent of CO 2 precipitation in porous media was tested. It was observed that co-injection of CO 2 and enzyme solution leads to higher pressure drop across the cores in tests reported here. Finally, the learning of above tests has been used to outline a series of potential challenges and propose solutions for effective utilization of enzyme bovine carbonic anhydrase for safe sequestration of CO 2 in saline formations.