Practice-based vs performance-based standards for carbon sequestration projects

AbstractInterest in deployment of carbon capture and sequestration (CCS) is at odds with the lack of regulations to guide deployment. This can be resolved by a practice-based regulatory framework focused on data collection, prediction, and iteration. Such a regulatory framework could require operators to undertake behaviors that would empower initial regulatory efforts and tell potential operators what to do and why, not how to do it or to what precision. The most important practices comprise prediction and validation. This approach would have several positive effects, including encouraging would-be operators to invest in site selection, planning, modeling and prediction, monitoring, and regular updating of geotechnical operation

Local Strategy Improvement for Parity Game Solving

The problem of solving a parity game is at the core of many problems in model checking, satisfiability checking and program synthesis. Some of the best algorithms for solving parity game are strategy improvement algorithms. These are global in nature since they require the entire parity game to be present at the beginning. This is a distinct disadvantage because in many applications one only needs to know which winning region a particular node belongs to, and a witnessing winning strategy may cover only a fractional part of the entire game graph. We present a local strategy improvement algorithm which explores the game graph on-the-fly whilst performing the improvement steps. We also compare it empirically with existing global strategy improvement algorithms and the currently only other local algorithm for solving parity games. It turns out that local strategy improvement can outperform these others by several orders of magnitude

Cosmological Relativity: A General-Relativistic Theory for the Accelerating Expanding Universe

Recent observations of distant supernovae imply, in defiance of expectations, that the universe growth is accelerating, contrary to what has always been assumed that the expansion is slowing down due to gravity. In this paper a general-relativistic cosmological theory that gives a direct relationship between distances and redshifts in an expanding universe is presented. The theory is actually a generalization of Hubble's law taking gravity into account by means of Einstein's theory of general relativity. The theory predicts that the universe can have three phases of expansion, decelerating, constant and accelerating, but it is shown that at present the first two cases are excluded, although in the past it had experienced them. Our theory shows that the universe now is definitely in the stage of accelerating expansion, confirming the recent experimental results

Symmetric Strategy Improvement

Symmetry is inherent in the definition of most of the two-player zero-sum games, including parity, mean-payoff, and discounted-payoff games. It is therefore quite surprising that no symmetric analysis techniques for these games exist. We develop a novel symmetric strategy improvement algorithm where, in each iteration, the strategies of both players are improved simultaneously. We show that symmetric strategy improvement defies Friedmann's traps, which shook the belief in the potential of classic strategy improvement to be polynomial

Carbon Capture and Storage

Carbon capture and sequestration (CCS) is the long-term isolation of carbon dioxide from the atmosphere through physical, chemical, biological, or engineered processes. This includes a range of approaches including soil carbon sequestration (e.g., through no-till farming), terrestrial biomass sequestration (e.g., through planting forests), direct ocean injection of CO{sub 2} either onto the deep seafloor or into the intermediate depths, injection into deep geological formations, or even direct conversion of CO{sub 2} to carbonate minerals. Some of these approaches are considered geoengineering (see the appropriate chapter herein). All are considered in the 2005 special report by the Intergovernmental Panel on Climate Change (IPCC 2005). Of the range of options available, geological carbon sequestration (GCS) appears to be the most actionable and economic option for major greenhouse gas reduction in the next 10-30 years. The basis for this interest includes several factors: (1) The potential capacities are large based on initial estimates. Formal estimates for global storage potential vary substantially, but are likely to be between 800 and 3300 Gt of C (3000 and 10,000 Gt of CO{sub 2}), with significant capacity located reasonably near large point sources of the CO{sub 2}. (2) GCS can begin operations with demonstrated technology. Carbon dioxide has been separated from large point sources for nearly 100 years, and has been injected underground for over 30 years (below). (3) Testing of GCS at intermediate scale is feasible. In the US, Canada, and many industrial countries, large CO{sub 2} sources like power plants and refineries lie near prospective storage sites. These plants could be retrofit today and injection begun (while bearing in mind scientific uncertainties and unknowns). Indeed, some have, and three projects described here provide a great deal of information on the operational needs and field implementation of CCS. Part of this interest comes from several key documents written in the last three years that provide information on the status, economics, technology, and impact of CCS. These are cited throughout this text and identified as key references at the end of this manuscript. When coupled with improvements in energy efficiency, renewable energy supplies, and nuclear power, CCS help dramatically reduce current and future emissions (US CCTP 2005, MIT 2007). If CCS is not available as a carbon management option, it will be much more difficult and much more expensive to stabilize atmospheric CO{sub 2} emissions. Recent estimates put the cost of carbon abatement without CCS to be 30-80% higher that if CCS were to be available (Edmonds et al. 2004)

Explaining the Electroweak Scale and Stabilizing Moduli in M Theory

In a recent paper \cite{Acharya:2006ia} it was shown that in $M$ theory vacua without fluxes, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results of \cite{Acharya:2006ia} in more detail and generalizes them, finding an essentially unique de Sitter (dS) vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV - 100 TeV range.Comment: 73 pages, 39 figures, Minor typos corrected, Figures and References adde

Combinatorial simplex algorithms can solve mean payoff games

A combinatorial simplex algorithm is an instance of the simplex method in which the pivoting depends on combinatorial data only. We show that any algorithm of this kind admits a tropical analogue which can be used to solve mean payoff games. Moreover, any combinatorial simplex algorithm with a strongly polynomial complexity (the existence of such an algorithm is open) would provide in this way a strongly polynomial algorithm solving mean payoff games. Mean payoff games are known to be in NP and co-NP; whether they can be solved in polynomial time is an open problem. Our algorithm relies on a tropical implementation of the simplex method over a real closed field of Hahn series. One of the key ingredients is a new scheme for symbolic perturbation which allows us to lift an arbitrary mean payoff game instance into a non-degenerate linear program over Hahn series.Comment: v1: 15 pages, 3 figures; v2: improved presentation, introduction expanded, 18 pages, 3 figure

SITE CHARACTERIZATION AND SELECTION GUIDELINES FOR GEOLOGICAL CARBON SEQUESTRATION

Carbon capture and sequestration (CCS) is a key technology pathway to substantial reduction of greenhouse gas emissions for the state of California and the western region. Current estimates suggest that the sequestration resource of the state is large, and could safely and effectively accept all of the emissions from large CO2 point sources for many decades and store them indefinitely. This process requires suitable sites to sequester large volumes of CO2 for long periods of time. Site characterization is the first step in this process, and the state will ultimately face regulatory, legal, and technical questions as commercial CCS projects develop and commence operations. The most important aspects of site characterizations are injectivity, capacity, and effectiveness. A site can accept at a high rate a large volume of CO2 and store it for a long time is likely to serve as a good site for geological carbon sequestration. At present, there are many conventional technologies and approaches that can be used to estimate, quantify, calculate, and assess the viability of a sequestration site. Any regulatory framework would need to rely on conventional, easily executed, repeatable methods to inform the site selection and permitting process. The most important targets for long-term storage are deep saline formations and depleted oil and gas fields. The primary CO2 storage mechanisms for these targets are well understood enough to plan operations and simulate injection and long-term fate of CO2. There is also a strong understanding of potential geological and engineering hazards for CCS. These hazards are potential pathway to CO2 leakage, which could conceivably result in negative consequences to health and the environmental. The risks of these effects are difficult to quantify; however, the hazards themselves are sufficiently well understood to identify, delineate, and manage those risks effectively. The primary hazard elements are wells and faults, but may include other concerns as well. There is less clarity regarding the legal and regulatory issues around site characterization for large CCS injection volumes. In particular, it is not clear what would constitute due diligence for a potential selection and operation of a commercial site. This is complicated by a lack of clarity around permitting issues and subsurface ownership. However, there are many natural, industrial, regulatory, and legal analogs for these questions. However, solutions will need to evolve within the set of laws and practices current to the State. The chief conclusion of this chapter is that there is enough knowledge today to characterize a site for geological carbon sequestration safely and effective permitting and operation. From this conclusion and others flow a set of recommendations that represent potential actions for decision makers