Carbon Dioxide Removal

There is a wide gap between the aspirational goals of the Paris agreement (i.e., stabilization at less than 2°C) and the Nationally Determined Contributions (NDCs) to reduce CO2 emissions. As a result, it is becoming more and more apparent that we will shoot right past the 2°C target. As a result, there has been a significant increase in interest in CO2 removal (CDR) technologies. These technologies have the capacity to remove CO2 from the atmosphere and, at least theoretically, correct in any overshoot of the 2°C goal. The CDR technologies most often cited are (from Smith, et al., “Biophysical and economic limits to negative CO2 emissions”, Nature Climate Change, 6, January (2016).): • BECCS: Bioenergy with carbon capture and storage • DAC: Direct air capture of CO2 from ambient air by engineered chemical reactions • EW: Enhanced weathering of minerals, where natural weathering to remove CO2 from the atmosphere is accelerated and the products stored in soils, or buried in land or deep ocean • AR: Afforestation and reforestation to fix atmospheric carbon in biomass and soils • Ocean: Manipulation of carbon uptake by the ocean, either biologically (that is, by fertilizing nutrient-limited areas) or chemically (that is, by enhancing alkalinity) • Agriculture: Altered agricultural practices, such as increased carbon storage in soils • Biochar: Converting biomass to recalcitrant biochar, for use as a soil amendment. This talk will focus on the technologies from the above list related to carbon dioxide capture and storage (CCS). Two of the above technologies have CCS at their core, BECCS and DACS. EW includes carbonate mineralization, which is part of the CCS portfolio. Finally, there is some overlap with Ocean, since not so long ago storing captured CO2 in the ocean was under serious consideration. This talk will present a high-level technological assessment for these CCS related CDR options. The talk will also discuss the following key questions: • What are the economics of these technologies? • Can these technologies scale to gigaton levels? • Will these technologies present public acceptance issues

A Path Forward for Low Carbon Power from Biomass

The two major pathways for energy utilization from biomass are conversion to a liquid fuel (i.e., biofuels) or conversion to electricity (i.e., biopower). In the United States (US), biomass policy has focused on biofuels. However, this paper will investigate three options for biopower: low co-firing (co-firing scenarios refer to combusting a given percentage of biomass with coal) (5%–10% biomass), medium co-firing (15%–20% biomass), and dedicated biomass firing (100% biomass). We analyze the economic and greenhouse gas (GHG) emissions impact of each of these options, with and without CO[subscript 2] capture and storage (CCS). Our analysis shows that in the absence of land use change emissions, all biomass co-combustion scenarios result in a decrease in GHG emissions over coal generation alone. The two biggest barriers to biopower are concerns about carbon neutrality of biomass fuels and the high cost compared to today’s electricity prices. This paper recommends two policy actions. First, the need to define sustainability criteria and initiate a certification process so that biomass providers have a fixed set of guidelines to determine whether their feedstocks qualify as renewable energy sources. Second, the need for a consistent, predictable policy that provides the economic incentives to make biopower economically attractive

Using auxiliary gas power for CCS energy needs in retrofitted coal power plants

Adding post-combustion capture technology to existing coal-fired power plants is being considered as a near-term option for mitigating CO[subscript 2] emissions. To supply the thermal energy needed for CO[subscript 2] capture, much of the literature proposes thermal integration of the existing coal plant’s steam cycle with the capture process’ stripper reboiler. This paper examines the option of using an auxiliary natural gas turbine plant to meet the energetic demands of carbon capture and compression. Three different auxiliary plant technologies were compared to integration for 90% capture from an existing, 500 MW supercritical coal plant. CO[subscript 2] capture (via a monoethylamine (MEA) absorption process) and compression is simulated using Aspen Plus. Thermoflow software is used to simulate three gas plant technologies. In some circumstances, it is found that using an auxiliary natural gas turbine may make retrofits more attractive compared to using thermal integration. The most important factors affecting desirability of the auxiliary plant retrofit are the cost of natural gas, the full cost of integration, and the potential for sale of excess electricity.Research Council of Norway (Statoil (Firm: Norway)Massachusetts Institute of Technology. Carbon Sequestration Initiativ

Economic predictions for heat mining : a review and analysis of hot dry rock (HDR) geothermal energy technology

The main objectives of this study were first, to review and analyze several economic assessments of Hot Dry Rock (HDR) geothermal energy systems, and second, to reformulate an economic model for HDR with revised cost components.A general evaluation of the technical feasibility of HDR technology components was also conducted in view of their importance in establishing drilling and reservoir performance parameters required for any economic assessment (see Sections 2-5). In our review, only economic projections for base load electricity produced from HDR systems were considered. Bases of 1989 dollars ($) were selected to normalize costs.Following the evaluation of drilling and reservoir performance, power plant choices and cost estimates are discussed in Section 6. In Section 7, the six economic studies cited earlier are reviewed and compared in terms of their key resource, reservoir and plant performance, and cost assumptions. Based on these comparisons, we have estimated parameters for three composite cases. Important parameters include: (1) resource quality--average geothermal gradient (oC/km) and well depth, (2) reservoir performance--effective productivity, flow impedance, and lifetime (thermal drawdown rate), (3) cost components--drilling, reservoir formation, and power plant costs and (4) economic factors--discount and interest rates, taxes, etc. In Section 8, composite case conditions were used to reassess economic projections for HDRproduced electricity. In Section 9, a generalized economic model for HDR-produced electricity is presented to show the effects of resource grade, reservoir performance parameters, and other important factors on projected costs. A sensitivity and uncertainty analysis using this model is given in Section 10. Section 11 treats a modification of the economic model for predicting costs for direct, non-electric applications. HDR economic projections for the U.S. are broken down by region in Section 12. In Section 13, we provide recommendations for continued research and development to reduce technical and economic uncertainties relevant to the commercialization of HDR

An issue of permanence: assessing the effectiveness of temporary carbon storage

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).In this paper, we present a method to quantify the effectiveness of carbon mitigation options taking into account the "permanence" of the emissions reduction. While the issue of permanence is most commonly associated with a "leaky" carbon sequestration reservoir, we argue that this is an issue that applies to just about all carbon mitigation options. The appropriate formulation of this problem is to ask 'what is the value of temporary storage?' Valuing temporary storage can be represented as a familiar economic problem, with explicitly stated assumptions about carbon prices and the discount rate. To illustrate the methodology, we calculate the sequestration effectiveness for injecting CO2 at various depths in the ocean. Analysis is performed for three limiting carbon price assumptions: constant carbon prices (assumes constant marginal damages), carbon prices rise at the discount rate (assumes efficient allocation of a cumulative emissions cap without a backstop technology), and carbon prices first rise at the discount rate but become constant after a given time (assumes introduction of a backstop technology). Our results show that the value of relatively deep ocean carbon sequestration can be nearly equivalent to permanent sequestration if marginal damages (i.e., carbon prices) remain constant or if there is a backstop technology that caps the abatement cost in the not too distant future. On the other hand, if climate damages are such as to require a fixed cumulative emissions limit and there is no backstop, then a storage option with even very slow leakage has limited value relative to a permanent storage option

Scenario analysis of carbon capture and sequestration generation dispatch in the western U.S. electricity system

AbstractWe present an analysis of the feasibility of dispatch of coal-fired generation with carbon capture and sequestration (CCS) as a function of location. Dispatch es for locations are studied with regard to varying carbon dioxide (CO2) prices, demand load levels, and natural gas prices. Using scenarios with a carbon price range of $0 to$ 100 per ton - CO2, we show that a hypothetical CCS generator would be dispatched on a marginal cost basis given a high enough carbon price but that the minimum carbon price required for dispatch varies widely by location and system demand

Modeling the release of CO2 in the deep ocean

The idea of capturing and disposing of carbon dioxide (CO2) from the flue gas of fossil fuel-fired power plants has recently received attention as a possible mitigation strategy to counteract potential global warming due to the "greenhouse effect." One specific scheme is to concentrate the CO2 in the flue gas to over 90 mol %, compress and dehydrate the CO2 to supercritical conditions, and then transport it through a pipeline for deep ocean disposal. In Golomb et al. (1989), this scheme was studied, with emphasis on the CO 2 capture aspects. In this follow-on study, we concentrate on the mechanisms of releasing the CO 2 in the deep ocean.Golomb et al. only considered the release of individual liquid CO 2 droplets in the region below 500 m. In this study, we consider all depths in both the liquid and vapor regions, and we model the entire plume in addition to individual droplets or bubbles. The key design variables in the model that can be controlled are: (1) release depth, (2) number of diffuser ports, N, and (3) initial bubble or droplet radius, ro. The results show that we can lower the height of the plume by increasing the number of diffuser ports and/or decreasing the initial bubble or droplet radius. Figure S-1 summarizes the results for a release depth of 500 m. With reasonable values for N and r. of 10 and 1 cm respectively, we can keep the plume height under 100 m. Since our goal is to dissolve all the CO2 before it reaches the well-mixed surface layer at approximately 100 m, we can release our C02 at depths as shallow as 200 m. However, the residence time of the sequestered CO2 in the ocean is also a function of depth. For releases of CO2 less than 500 m deep, we can estimate a residence time of less than 50 years, and for a release from about 1000 m, a residence time from 200 to 300 years. These residence times may be increased by releasing in areas of downwelling or by forming solid CO 2-hydrates which will sink to the ocean floor. For depths greater than 500 m, CO2-hydrates may form but we have ignored them due to lack of data.We estimate that the local CO2 concentration will increase about 0.2 kg/m 3 . Added to the background concentration of 0.1 kg/m 3 , the resulting total concentration will be about 0.3 kg/m 3 , much less than saturation levels of about 40 kg/m 3 . Similarly, SO2 and NOx concentration increases will be about 1 .10 - 3 kg/m3 and 2 10- 4 kg/m 3 , respectively. Given an ambient current of 10 cm/s, horizontal dispersion will dilute these concentration increases by a factor of two at a distance of about 4 km downstream.In implementing a CO2 capture and sequester scheme based on an air separation/ flue gas recycle power plant, the price of electricity would double. The reasons for this doubling are: (1) 44% due to derating of the power plant because of the parasitic power required to capture C02, mainly for air separation and CO compression, (2) 42% due to capital charges and operation and maintenance costs (excluding fuel) of the power plant modifications, including air separation and CO2 compression, and (3) 14% due to capital charges and operation and maintenance costs of a 160 km pipeline for deep ocean disposal. These numbers assume that no additional control measures are required to mitigate potential environmental problems are associated with deep ocean disposal of CO02.Funded by the Mitsubishi Research Insitute, Society and Technology Dept

Stakeholder attitudes on carbon capture and storage -- An international comparison

This paper presents results from a survey on stakeholder attitudes towards Carbon Capture and Storage (CCS). The survey is the first to make a global comparison across three major regions; USA, Japan, and Europe. The 30-question survey targeted individuals working at stakeholder organizations that seek to shape, and will need to respond to, policy on CCS, including electric utilities, oil & gas companies, CO2-intensive industries and non-governmental organizations (NGOs). The results show generally small differences across the regions and between the different groups of stakeholders. All believed that the challenge of significant reductions in emissions using only current technologies was severe. There is a widespread belief both that renewable technologies such as solar power and CCS will achieve major market entry into the electricity sector within the next 10 to 20 years, whereas there is more skepticism about the role of hydrogen and especially nuclear fusion in the next 50 years. All groups were generally positive towards renewable energy. Yet, there were some notable areas of disagreement in the responses, for example, as expected, NGOs considered the threat of climate change to be more serious than the other groups. North Americans respondents were more likely to downplay the threat compared to those of the other regions. The Japanese were more concerned about the burden that would be placed on industry in the coming decade as a result of emissions constraints and NGOs were more likely to believe that the burden would be light or very light. NGOs believed CCS to be far more attractive than nuclear fusion power but much less than renewables. As expected, the risk for leakage from reservoirs was ranked number one of the risk options given.Alliance for Global SustainabilityNational Institute of Advanced Industrial Science and Technology (Japan)Carbon Sequestration InitiativeAlliance for Global Sustainability (AGS project “Pathways to Sustainable European Energy Systems” funding