Research status, hot spots, difficulties and future development direction of microbial geoengineering

Microbial geoengineering technology,as a new eco-friendly rock and soil improvement and reinforcement technology,has a wide application prospect.However,this technology still has many deficiencies and is difficult to achieve efficient curing,which has become the bottleneck of large-scale field application.This paper reviews the research status,hot spots,difficulties and future development direction microbial induced calcium carbonate precipitation(MICP)technology.The principle of solidification and the physical and mechanical properties of improved rock and soil are systematically summarized.The solidification efficiency is mainly affected by the reactant itself and the external environment.At present,the MICP technology has been preliminarily applied in the fields of soil solidification,crack repair,anti-seepage treatment,pollution repair and microbial cement.However,the technology is currently mainly limited to the laboratory level due to the difficulty of homogeneous mineralization,uneconomical reactants,short microbial activity period and large environmental interference,incidental toxicity of metabolites and poor field application.Future directions include improving the uniformity of mineralization by improving grouting methods,improving urease persistence by improving urease activity,and improving the adaptability of bacteria to the environment by optimizing bacterial species.Finally,the authors point out the economic advantages of combining soybean peptone,soybean meal and cottonseed as carbon source with phosphogypsum as calcium source to induce CaCO3.

Geoengineering: Basic science and ongoing research efforts in China

Geoengineering （also called climate engineering）, which refers to large-scale intervention in the Earth＇s climate system to counteract greenhouse gas-induced warming, has been one of the most rapidly growing areas of climate research as a potential option for tackling global warming. Here, we provide an overview of the scientific background and research progress of proposed geoengineering schemes. Geo- engineering can be broadly divided into two categories： solar geoengineering （also called solar radiation management, or SRM）, which aims to reflect more sunlight to space, and carbon dioxide removal （CDR）, which aims to reduce the CO2 content in the atmosphere. First, we review different proposed geoengineering methods involved in the solar radiation management and carbon dioxide removal schemes. Then, we discuss the fundamental science underlying the climate response to the carbon dioxide removal and solar radiation management schemes. We focus on two basic issues： 1） climate response to the reduction in solar irradiance and 2） climate response to the reduction in atmospheric COe. Next, we introduce an ongoing geoengineering research project in China that is supported by National Key Basic Research Program. This research project, being the first coordinated geoengineering research program in China, will systematically investigate the physical mechanisms, climate impacts, and risk and governance of a few targeted geoengineering schemes. It is expected that this research program will help us gain a deep understanding of the physical science underlying geoengineering schemes and the impacts of geoengineering on global climate, in particular, on the Asia monsoon region.

A synthetical geoengineering approach to evaluate the largest hydraulic fracturing-induced earthquake in the East Shale Basin, Alberta

On 2019-03-04,the largest induced earthquake(ML4.18)occurred in the East Shale Basin,Alberta,and the underlying physical mechanisms have not been fully understood.This paper proposes a synthetical geoengineering methodology to comprehensively characterize this earthquake caused by hydraulic fracturing.Based on 3D structural,petrophysical,and geomechanical models,an unconventional fracture model is constructed by considering the stress shadow between adjacent hydraulic fractures and the interactions between hydraulic and natural fractures.Coupled poroelastic simulations are conducted to reveal the triggering mechanisms of induced seismicity.It is found that four vertical basement-rooted faults were identified via focal mechanisms analysis.The brittleness index(BI)along two horizontal wells has a high magnitude(BI>0.5),indicating the potential susceptibility of rock brittleness.Due to the presence of overpressure,pre-existing faults in the Duvernay Formation are highly susceptible to fault reactivation.The occurrence of the earthquake clusters has been attributed to the fracturing fluid injection during the west 38^(th)-39^(th) stage and east 38^(th) stage completions.Rock brittleness,formation overpressure,and large fracturing job size account for the nucleation of earthquake clusters,and unconventional natural-hydraulic fracture networks provide fluid flow pathways to cause fault reactivation.This workflow can be used to mitigate potential seismic risks in unconventional reservoirs in other fields.

Implications of geoengineering under the 1.5 ℃ target： Analysis and policy suggestions

The Paris Agreement introduced a 1.5 ℃ target to control the rise in global temperature, but clear arrangements for feasible implementation pathways were not made. Achieving the 1.5 ℃ target imposes high requirements on global emission reduction. Nationally Determined Con- tributions of all Parties are far from the 1.5 ℃ target, and conventional emission reduction technologies and policies will also have difficulty in fulfilling this task. In this context, geoengineering is gaining interest in the international arena. The Paris Agreement includes afforestation, carbon capture, utilization and storage, and negative emission technologies such as bio-energy with carbon capture and store. All of these techniques are CO2 removal technologies that belong to geoengineering. Solar radiation management, which is highly controversial, has also attracted increased attention in recent years. Although the outline of the IPCC Special Report on 1.5 ℃ does not include a specific section on geoengineering issues yet, geoengineering is an unconventional technical option that cannot be avoided in research and discussions on impact assessment, technical options, ethics, and international governance under the 1.5 ℃ target. On the basis of analyzing and discussing abovementioned issues, this paper proposes several policy suggestions for China to strengthen research on and response to geoengineering.

From the new Austrian tunneling method to the geoengineering condition evaluation and dynamic controlling method

The new Austrian tunneling method （NATM） is widely applied in design and construction of underground engineering projects. When the type and distribution of unfavorable geological bodies （UGBs） associated with their influences on geoengineering are complicated or unfortunately are overlooked, we should pay more attentions to internal features of rocks grades IV and V （even in local but mostly controlling zones）. With increasing attentions to the characteristics, mechanism and influences of engineering construction-triggered geohazards, it is crucial to fully understand the disturbance of these geohazards on project construction. A reasonable determination method in construction procedure, i.e. the shape of working face, the type of engineering support and the choice of feasible procedure, should be considered in order to mitigate the construction-triggered geohazards. Due to their high sensitivity to groundwater and in-situ stress, various UGBs exhibit hysteretic nature and failure modes. To give a complete understanding on the internal causes, the emphasis on advanced comprehensive geological forecasting and overall reinforcement treatment is therefore of more practical significance. Compre- hensive evaluation of influential factors, identification of UGB, and measures of discontinuity dynamic controlling comprises the geoengineering condition evaluation and dynamic controlling method. In a case of a cut slope, the variations of UGBs and the impacts of key environmental factors are presented, where more severe construction-triggered geohazards emerged in construction stage than those predicted in design and field investigation stages. As a result, the weight ratios of different influential factors with respect to field investigation, design and construction are obtained.

Simulated effect of sunshade solar geoengineering on the global carbon cycle

Solar geoengineering has been proposed as a potential mechanism to counteract global wanning. Here we use the University of Victoria Earth System Model （UVic） to simulate the effect of idealized sunshade geoengineering on the global carbon cycle. We conduct two simulations. The first is the A2 simulation, where the model is driven by prescribed emission scenario based on the SRES A2 COz emission pathway. The second is the solar geoengineering simulation in which the model is driven by the A2 CO2 emission scenario combined with sunshade solar geoengineering. In the model, solar geoengineering is represented by a spatially uniform reduction in solar insolation that is implemented at year 2020 to offset CO2-induced global mean surface temperature change. Our results show that solar geoengineering increases global carbon uptake relative to A2, in particular CO2 uptake by the terrestrial biosphere. The increase in land carbon uptake is mainly associated with increased net primary production （NPP） in the tropics in the geoengineering simulation, which prevents excess warming in tropics. By year 2100, solar geoengineering decreases A2-simulated atmospheric CO2 by 110 ppm （12%） and causes a 60% （251 Pg C） increase in land carbon accumulation compared to A2. Solar geoengineering also prevents the reduction in ocean oxygen concentration caused by increased ocean temperatures and decreased ocean ventilation, but reduces global ocean NPE Our results suggest that to fully access the climate effect of solar geoengineering, the response of the global carbon cycle should be taken into account.

Glacier geoengineering to address sea-level rise:A geotechnical approach

It is remarkable that the high-end sea level rise threat over the next few hundred years comes almost entirely from only a handful of ice streams and large glaciers.These occupy a few percent of ice sheets’coastline.Accordingly,spatially limited interventions at source may provide globally-equitable mitigation from rising seas.Ice streams control draining of ice sheets;glacier retreat or acceleration serves to greatly increase potential sea level rise.While various climatic geoengineering approaches have been considered,serious consideration of geotechnical approaches has been limited e particularly regarding glaciers.This study summarises novel and extant geotechnical techniques for glacier restraint,identifying candidates for further research.These include draining or freezing the bed;altering surface albedo;creating obstacles:retaining snow;stiffening shear margins with ice;blocking warm sea water entry;thickening ice shelves(increasing buttressing,and strengthening fractured shelves against disintegration);as well as using regional climate engineering or local cloud seeding to cool the glacier or add snow.Not all of these ideas are judged reasonable or feasible,and even fewer are likely to be found to be advisable after further consideration.By describing and evaluating the potential and risks of a large menu of responses e even apparently hopeless ones e we can increase the chances of finding one that works in times of need.

Geoengineering and the blockchain: Coordinating Carbon Dioxide Removal and Solar Radiation Management to tackle future emissions

Geoengineering is a proposed response to anthropogenic global warming (AGW). Conventionally it consists of two strands: Solar Radiation Management (SRM), which is fast-acting, incomplete but inexpensive, and Carbon Dioxide Removal (CDR), which is slower acting, more expensive, and comprehensive. Pairing SRM and CDR offers a contractually complete solution for future emissions if effectively-scaled and coordinated. SRM offsets warming, while CDR takes effect. We suggest coordination using a blockchain, i.e. smart contracts and a distributed ledger. Specifically, we integrate CDR futures with time and volume-matched SRM orders, to address emissions contractually before release. This provides an economically and environmentally proportionate solution to CO2 emissions at the wellhead, with robust contractual transparency, and minimal overhead cost. Our proposal offers a 'polluter pays' implementation of Long & Shepherds SRM 'bridge' concept. This 'polluter geoengineers' approach mandates and verifies emissionslinked payments with minimal friction, delay, or cost. Finally, we compare alternative market designs against this proposal, finding that this proposal offers several advantages. We conclude that blockchain implementation of the 'polluter geoengineers' approach is attractive and feasible for larger wellhead contracts. We also identify a handful of advantages and disadvantages that merit further study.

Security of solar radiation management geoengineering

Solar Radiation Management (SRM) geoengineering is a proposed response to anthropogenic global warming (AGW)(National Academy of Sciences, 2015). There may be profound - even violent - disagreement on preferred temperature. SRM disruption risks dangerous temperature rise (termination shock). Concentrating on aircraft-delivered Stratospheric Aerosol Injection (SAI), we appraise threats to SRM and defense methodologies. Civil protest and minor cyberattacks are almost inevitable but are manageable (unless state-sponsored). Overt military attacks are more disruptive, but unlikely - although superpowers' symbolic overt attacks may deter SRM. Unattributable attacks are likely, and mandate use of widely-available weapons. Risks from unsophisticated weapons are therefore higher. An extended supply chain is more vulnerable than a secure airbase - necessitating supply-chain hardening. Recommendations to improve SRM resilience include heterogeneous operations from diverse, secure, well-stocked bases (possibly ocean islands or aircraft carriers);and avoidance of single-point-of failure risks (e.g. balloons). A distributed, civilianoperated system offers an alternative strategy. A multilateral, consensual SRM approach reduces likely attack triggers.

Distributed governance of Solar Radiation Management geoengineering:A possible solution to SRM’s“free-driver”problem?

Geoengineering(deliberate climate modification)is a possible way to limit Anthropogenic Global Warming(AGW)(Shepherd,2009;National Research Council,2015).Solar Radiation Management geoengineering(SRM)offers relatively inexpensive,rapid temperature control.However,this low cost leads to a risk of controversial unilateral intervention—the“free-driver”problem(Weitzman,2015).Consequently,this creates a risk of counter-geoengineering(deliberate warming)(Parker et al.,2018),resulting in governance challenges(Svoboda,2017)akin to an arms race.Free-driver deployment scenarios previously considered include the rogue state,Greenfinger(Bodansky,2013),or power blocs(Ricke et al.,2013),implying disagreement and conflict.We propose a novel distributed governance model of consensually-constrained unilateralism:Countries’authority is limited to each state’s fraction of the maximum realistic intervention(e.g.,pre-industrial temperature).We suggest a division of authority based on historical emissions(Rocha et al.,2015)—noting alternatives(e.g.,population).To aid understanding,we offer an analogue:An over-heated train carriage,with passenger-controlled windows.We subsequently discuss the likely complexities,notably Coasian side-payments.Finally,we suggest further research:Algebraic,bot and human modeling;and observational studies.

Mutual feedback between algal blooming and global warming

Global warming and algal blooms have been two of the most pressing problems faced by the world today.In recent decades,numerous studies indicated that global warming promoted the expansion of algal blooms.However,research on how algal blooms respond to global warming is scant.Global warming coupled with eutrophication promoted the rapid growth of phytoplankton,which resulted in an expansion of algal blooms.Algal blooms are affected by the combined effects of global warming,including increases in temperatures,CO_(2)concentration,and nutrient input to aquatic systems by extreme weather events.Since the growth of phytoplankton requires CO_(2),they appear to act as a carbon sink.Unfortunately,algal blooms will release CH4,CO_(2),and inorganic nitrogen when they die and decompose.As substrate nitrogen increases from decompose algal biomass,more N2O will be released by nitrification and denitrification.In comparison to CO_(2),CH4has 28-fold and N2O has 265-fold greenhouse effect.Moreover,algal blooms in the polar regions may contribute to melting glaciers and sea ice(will release greenhouse gas,which contribute to global warming)by reducing surface albedo,which consequently would accelerate global warming.Thus,algal blooms and global warming could form feedback loops which prevent human survival and development.Future researches shall examine the mechanism,trend,strength,and control strategies involved in this mutual feedback.Additionally,it will promote global projects of environmental protection combining governance greenhouse gas emissions and algal blooms,to form a geoengineering for regulating the cycles of carbon,nitrogen,and phosphorus.

Effects of solar radiation modification on the ocean carbon cycle:An earth system modeling study

Solar radiation modification(SRM,also termed as geoengineering)has been proposed as a potential option to counteract anthropogenic warming.The underlying idea of SRM is to reduce the amount of sunlight reaching the atmosphere and surface,thus offsetting some amount of global warming.Here,the authors use an Earth system model to investigate the impact of SRM on the global carbon cycle and ocean biogeochemistry.The authors simulate the temporal evolution of global climate and the carbon cycle from the pre-industrial period to the end of this century under three scenarios:the RCP4.5 CO_(2) emission pathway,the RCP8.5 CO_(2) emission pathway,and the RCP8.5 CO_(2) emission pathway with the implementation of SRM to maintain the global mean surface temperature at the level of RCP4.5.The simulations show that SRM,by altering global climate,also affects the global carbon cycle.Compared to the RCP8.5 simulation without SRM,by the year 2100,SRM reduces atmospheric CO_(2) by 65 ppm mainly as a result of increased CO_(2) uptake by the terrestrial biosphere.However,SRM-induced change in atmospheric CO_(2) and climate has a small effect in mitigating ocean acidification.By the year 2100,relative to RCP8.5,SRM causes a decrease in surface ocean hydrogen ion concentration([H^(+)])by 6% and attenuates the seasonal amplitude of[H^(+)]by about 10%.The simulations also show that SRM has a small effect on globally integrated ocean net primary productivity relative to the high-CO_(2) simulation without SRM.This study contributes to a comprehensive assessment of the effects of SRM on both the physical climate and the global carbon cycle.

小规模平流层注入气溶胶实验有助于地球工程研究

2018年12月12日,国际著名学术期刊Nature刊登了'2018年度十大科学长篇专题报道:这一年最难忘的科学故事'(https://www.nature.com/articles/d41586-018-07748-5).Nature评选出2018年度最受欢迎的十大科学长篇专题报道:从首个遮挡太阳的实验,到传统中医的兴起,再到拯救消失的野生动物.

The carbon dioxide removal potential of Liquid Air Energy Storage: A high-level technical and economic appraisal

Liquid Air Energy Storage(LAES)is at pilot scale.Air cooling and liquefaction stores energy;reheating revaporises the air at pressure,powering a turbine or engine(Ameel et al.,2013).Liquefaction requires water&CO2 removal,preventing ice fouling.This paper proposes subsequent geological storage of this CO2–offering a novel Carbon Dioxide Removal(CDR)by-product,for the energy storage industry.It additionally assesses the scale constraint and economic opportunity offered by implementing this CDR approach.Similarly,established Compressed Air Energy Storage(CAES)uses air compression and subsequent expansion.CAES could also add CO2 scrubbing and subsequent storage,at extra cost.CAES stores fewer joules per kilogram of air than LAES–potentially scrubbing more CO2 per joule stored.Operational LAES/CAES technologies cannot offer full-scale CDR this century(Stocker et al.,2014),yet they could offer around 4%of projected CO2 disposals for LAES and<25%for current-technology CAES.LAES CDR could reach trillion-dollar scale this century(20 billion USD/year,to first order).A larger,less certain commercial CDR opportunity exists for modified conventional CAES,due to additional equipment requirements.CDR may be commercially critical for LAES/CAES usage growth,and the necessary infrastructure may influence plant scaling and placement.A suggested design for low-pressure CAES theoretically offers global-scale CDR potential within a century(ignoring siting constraints)–but this must be costed against competing CDR and energy storage technologies.

Comparison of the carbon cycle and climate response to artificial ocean alkalinization and solar radiation modification

Carbon dioxide removal and solar radiation modification(SRM)are two classes of proposed climate intervention methods.A thorough understanding of climate system response to these methods calls for a good understanding of the carbon cycle response.In this study,we used an Earth system model to examine the response of global climate and carbon cycle to artificial ocean alkalinization(AOA),a method of CO_(2)removal,and reduction in solar irradiance that represents the overall effect of solar radiation modification.In our simulations,AOA is applied uniformly over the global ice-free ocean under the RCP8.5 scenario to bring down atmospheric CO_(2)to the level of RCP4.5,and SRM is applied uniformly over the globe under the RCP8.5 scenario to bring down global mean surface temperature to the level of RCP4.5.Our simulations show that with the same goal of temperature stabilization,AOA and SRM cause fundamentally different perturbations of the ocean and land carbon cycle.By the end of the 21st century,relative to the simulation of RCP8.5,AOA-induced changes in ocean carbonate chemistry enhances global oceanic CO_(2)uptake by 983 PgC and increases global mean surface ocean pH by 0.42.Meanwhile,AOA reduces land CO_(2)uptake by 79 PgC and reduces atmospheric CO_(2)concentration by 426×10^(−6).By contrast,relative to the simulation of RCP8.5,SRM has a minor effect on the oceanic CO_(2)uptake and ocean acidification.SRM-induced cooling enhances land CO_(2)uptake by 140 PgC and reduces atmospheric CO_(2)concentration by 63×10^(−6).A sudden termination of SRM causes a rate of temperature change that is much larger than that of RCP8.5.A sudden termination of AOA causes a rate of temperature change that is comparable to that of RCP8.5 and a rate of ocean acidification that is much larger than that of RCP8.5.