The United States has the world’s largest coal reserves and Montana the highest potential for mega-mine development. Consequently,
a large-scale effort to convert coal to liquids (CTL) has been proposed to create a major source of domestic transportation
fuels from coal, and some prominent Montanans want to be at the center of that effort. We calculate that the energy efficiency
of the best existing Fischer–Tropsch (FT) process applied to average coal in Montana is less than 1/2 of the corresponding
efficiency of an average crude oil refining process. The resulting CO2 emissions are 20 times (2000%) higher for CTL than for conventional petroleum products. One barrel of the FT fuel requires
roughly 800 kg of coal and 800 kg of water. The minimum energy cost of subsurface CO2 sequestration would be at least 40% of the FT fuel energy, essentially halving energy efficiency of the process. We argue
therefore that CTL conversion is not the most valuable use for the coal, nor will it ever be, as long as it is economical
to use natural gas for electric power generation. This finding results from the low efficiency inherent in FT synthesis, and
is independent of the monumental FT plant construction costs, mine construction costs, acute lack of water, and the associated
environmental impacts for Montana.
Carbon capture and sequestration (CCS) is one of the important options available for partially stemming greenhouse gas emissions from large point sources. The possibility of leaking from deep storage needs to be addressed. The Wadi Namaleh area in southern Jordan provides an interesting case study of how excess CO2 can be trapped in the form of carbonates in the near surface, even when the local geology is not obviously conducive for such a process.Carbonate veins are formed in surface alteration zones of rhyolite host rock in this arid region. The alteration zones are limited to areas where surface soil or colluvium are present. Oxygen, deuterium and carbon isotopes of the carbonates and near-surface ground water in the area suggest that the source of carbon is deep seated CO2, and that the carbonate precipitated in local meteoric water under ambient temperature conditions. Analysis of strontium in the carbonate, fresh rhyolite and altered host shows that the source for calcium is aeolian. Trace elements show that metal and REE mobility are constrained to the alteration zone.Thus, interaction of H2O, CO2 and atmospheric wet and dry deposition lead to the formation of the clayey (montmorillonite) alteration zone. This zone acts to trap seeping CO2 and water, and thus produces conditions of progressively more efficient trapping of carbon dioxide by means of a positive feedback mechanism. Replication of these conditions in other areas will minimize CO2 leakage from man-made CCS sites. 相似文献
Responding to the threat of climate change, conserving freshwater ecosystems and securing adequate energy and water supplies are among the greatest challenges facing modern societies. Yet recognition of the interdependencies between climate, energy and water policy—with resulting synergies and trade-offs—remains limited, leaving societies and governments alike vulnerable to the dangers of conflicted or unintended policy outcomes from sectoral decisions. In this paper, we analyse current Australian climate, energy and water policies to identify the risks of perverse outcomes between the three policy sectors. In doing so we categorise the conflicts and synergies between particular energy generation, carbon sequestration and water supply policies to improve understandings of the challenges facing decision makers in Australia and internationally. Four types of interventions are identified that would enable integration and optimisation of policies, namely: better cross-sectoral knowledge to inform decisions; the identification of technologies with co-benefits; markets with broader cross-sectoral participation (including linking water and carbon markets); and better-integrated governance institutions. 相似文献
Food-insecure households in many countries depend on international aid to alleviate acute shocks and chronic shortages. Some food security programmes (including Ethiopia’s Productive Safety Net Program–PSNP – which provides a case study for this article) have integrated aid in exchange for labour on public works to reduce long-term dependence by investing in the productive capacity and resilience of communities. Using this approach, Ethiopia has embarked upon an ambitious national programme of land restoration and sustainable land management. Although the intent was to reduce poverty, here we show that an unintended co-benefit is the climate-change mitigation from reduced greenhouse gas (GHG) emissions and increased landscape carbon stocks. The article first shows that the total reduction in net GHG emissions from PSNP’s land management at the national scale is estimated at 3.4 million?Mg?CO2e?y?1 – approximately 1.5% of the emissions reductions in Ethiopia’s Nationally Determined Contribution for the Paris Agreement. The article then explores some of the opportunities and constraints to scaling up of this impact.Key policy insights
Food security programmes (FSPs) can contribute to climate change mitigation by creating a vehicle for investment in land and ecosystem restoration.
Maximizing mitigation, while enhancing but not compromising food security, requires that climate projections, and mitigation and adaptation responses should be mainstreamed into planning and implementation of FSPs at all levels.
Cross-cutting oversight is required to integrate land restoration, climate policy, food security and disaster risk management into a coherent policy framework.
Institutional barriers to optimal implementation should be addressed, such as incentive mechanisms that reward effort rather than results, and lack of centralized monitoring and evaluation of impacts on the physical environment.
Project implementation can often be improved by adopting best management practices, such as using productive living livestock barriers where possible, and increasing the integration of agroforestry and non-timber forest products into landscape regeneration.
This work was motivated by considerations of potential leakage pathways for CO2 injected into deep geological formations for the purpose of carbon sequestration. Because existing wells represent a potentially important leakage pathway, a spatial analysis of wells that penetrate a deep aquifer in the Alberta Basin was performed and various statistical measures to quantify the spatial distribution of these wells were presented. The data indicate spatial clustering of wells, due to oil and gas production activities. The data also indicate that the number of wells that could be impacted by CO2 injection, as defined by the spread of an injected CO2 plume, varies from several hundred in high well-density areas to about 20 in low-density areas. These results may be applied to other mature continental sedimentary basins in North America and elsewhere, where detailed information on well location and status may not be available. 相似文献
For the degassing of coal seams, either prior to mining or in un-minable seams to obtain coalbed methane, it is the combination of cleat frequency, aperture, connectivity, stress, and mineral occlusions that control permeability. Unfortunately, many potential coalbeds have limited permeability and are thus marginal for economic methane extraction. Enhanced coalbed methane production, with concurrent CO2 sequestration is also challenging due to limited CO2 injectivity. Microwave energy can, in the absence of confining stress, induce fractures in coal. Here, creation of new fractures and increasing existing cleat apertures via short burst, high-energy microwave energy was evaluated for an isotropically stressed and an unstressed bituminous coal core. A microwave-transparent argon gas pressurized (1000 psi) polycarbonate vessel was constructed to apply isotropic stress simulating ~ 1800 foot depth. Cleat frequency and distribution was determined for the two cores via micro-focused X-ray computed tomography. Evaluation occurred before and after microwave exposure with and without the application of isotropic stress during exposure. Optical microscopy was performed for tomography cleat aperture calibration and also to examine lithotypes influences on fracture: initiation, propagation, frequency, and orientation. It was confirmed that new fractures are induced via high-energy microwave exposure in an unconfined bituminous core and that the aperture increased in existing cleats. Cleat/fracture volume, following microwave exposure increased from 1.8% to 16.1% of the unconfined core volume. For the first time, similar observations of fracture generation and aperture enhancement in coal were also determined for microwave exposure under isotropic stress conditions. An existing cleat aperture, determined from calibrated X-ray computed tomography increased from 0.17 mm to 0.32 mm. The cleat/fracture volume increased from 0.5% to 5.5%. Optical microscopy indicated that fracture initiated likely occurred in at least some cases at fusain microlithotypes. Presumably this was due to the open pore volumes and potential for bulk water presence or steam pressure buildup in these locations. For the major induced fractures, they were mostly horizontal (parallel to the bedding plane) and often contained within lithotype bands. Thus it appears likely that microwaves have the potential to enhance the communication between horizontal wellbore and existing cleat network, in coal seams at depth, for improved gas recovery or CO2 injection. 相似文献
Metabolic activity of Biological Soil Crusts (BSCs) is principally dependent on moisture availability, but also on temperature and light conditions. Less understood is how BSCs respond to elevated atmospheric CO2. This paper reports laboratory experimental results of elevated atmospheric CO2 on carbon fluxes for cyanobacterial BSCs. The study uses newly designed dynamic gas exchange chambers in which the internal atmosphere was controlled. CO2 flux was monitored during controlled experiments in two phases under simulated rainfall events (2 & 5 mm plus control with no wetting) each lasting 3 days with a dry period in between. Phase 1 subjected crusts to 392 ppm CO2 (representing ambient level) in dry air; in phase 2, the CO2 concentration was 801 ppm. Both phases exhibited significant efflux (respiration) of CO2 immediately after wetting, followed by substantial influx (sequestration) of CO2. Samples subject to 2 mm wetting sequestered an order of magnitude more C under elevated CO2 than at ambient CO2; for samples subject to 5 mm wetting, this increase was threefold. The findings highlight the role of BSCs in future carbon budgets by enabling greater sequestration into dryland soils even under enhanced atmospheric CO2 concentrations, following both light and heavy rainfall events. 相似文献
Land use change is one of the major factors that affect soil organic carbon(SOC) variation and global carbon balance. However, the effects of land use change on SOC are always variable. In this study, using a series of paired-field experiments, we estimated the effects of revegetation types and environmental conditions on SOC stock and vertical distribution after replacement of cropland with poplar(Populus tomentosa) and korshinsk peashrub(Caragana korshinskii) in three climate regions(Chifeng City, Fengning City and Datong City of the ′Beijing-Tianjin Sandstorm Source Control′(BTSSC) program area. The results show that SOC sequestration rate ranges from 0.15 Mg/(ha·yr) to 3.76 Mg/(ha·yr) in the soil layer of 0–100 cm in early stage after cropland afforestation in the BTSSC program area. The SOC accumulation rates are the highest in Fengning for both the two vegetation types. Compared to C. korshinskii, P. tomentosa has greater effects on SOC accumulation in the three climate regions, but significantly greater effect only appears in Datong. The SOC density increases by 20%–111% and 15%–59% for P. tomentosa and 9%–63% and 0–73% for C. korshinskii in the 0–20 cm and 20–100 cm soil layers, respectively. Our results indicate that cropland afforestation not only affects SOC stock in the topsoil, but also has some effects on subsoil carbon. However, the effect of cropland afforestation on SOC accumulation varied with climate regions and revegetation types. Considering the large area of revegetation and relatively high SOC accumulation rate, SOC sequestration in the BTSSC program should contribute significantly to decrease the CO2 concentration in the atmosphere. 相似文献