Scenario analysis 231 Overview

The scenario analysis presented within this paper is for the basket of six greenhouse gases only and relies, principally, on the scientific understanding contained within AR4. The analysis does not take account of the following the radiative forcing impacts of aerosols and non-CO2 aviation emissions (e.g. emissions of NOx in the upper troposphere, vapour trails and cirrus formation) 5 the most recent findings with respect to carbon sinks 6 previously underestimated emission sources 7 and the...

Physical and thermodynamic constraints

While any individual air capture technology will face a host of engineering challenges, there are two fundamental factors that make air capture more difficult than conventional post combustion CO2 capture processes first, the energy and materials cost of moving air through an absorber, and second the thermodynamic barrier due to the low concentration of CO2 in air. In this section we describe the physics that constrains an idealized air capture system with respect to these two factors. There is...

Global modelling

Most of the studies mentioned in the previous sections calibrated their estimates of the climate response to geo-engineering aerosol (Crutzen 2006 Wigley 2006) based upon historical observations of the aerosol produced by volcanic eruptions. Crutzen and Wigley focused primarily upon the surface temperature cooling, resulting from the aerosol's shielding effect. Trenberth & Dai (2007) analysed historical data to estimate the role of the shielding on the hydrological cycle, and concluded that...

Rotor lift and drag

The lift forces of a spinning cylinder are very much higher than those of a textile sail or an aircraft wing having the same projected area. Potential theory predicts that the lift per unit length of rotor should be 2n times the product of the surface speed of the rotor and far-field wind speed. This means that, for a constant rotor speed, it will rise with the first power of wind speed rather than with the square. If rotor surface speed and wind speed are kept in proportion, square law...

Carbon neutral hydrocarbons 721 Overview

We define CNHCs as those whose oxidation does not result in a net increase in atmospheric CO2 concentrations. Hydrocarbon fuels can be made carbon neutral either directly by manufacturing them using carbon captured from the atmosphere, or indirectly by tying the production of fossil fuels to a physical transfer of atmospheric carbon to permanent storage. The indirect route allows for a gradual transition from the current infrastructure, based on petroleum, to a sustainable system based on...

Advanced power cycles

The aim of carbon capture and sequestration technologies is to create a (near) zero-emissions coal-fired power plant. If higher efficiency in existing plants represents a short-term strategy to limit power plant carbon dioxide emissions then the zero-emissions plant is the medium-term solution. If we accept the arguments presented here that coal burning will continue well into the middle of this century, it is important that these technologies are brought into service as quickly as possible. In...

Rationale physical carbon arbitrage

Capturing CO2 from the air at a concentration of 0.04 may seem absurd given that after roughly two decades of research and development there are still no full scale commercial power plants with CO2 capture - for which the exhaust gas CO2 concentrations are greater than 10 - and only a handful of large commercial pilots appear to have financing in place to move ahead. The basic thermodynamics and physics suggest that capturing CO2 from the air need not be much harder than post-combustion capture...

Biology of diatom species

All OIF experiments have reported stimulation of the entire phytoplankton assemblage by iron addition although biomass accumulated almost exclusively in diatoms. Clearly, this algal group is subject to lower mortality rates than the smaller nano- and picophytoplankton of the microbial food web that, because of their larger surface volume ratios, should be more competitive in resource uptake, and should have higher growth rates than the much larger diatoms (Smetacek 1999). It follows that only...

Designing future OIF experiments

All experiments used the fertilization technique employed in IronEx releasing a solution of weakly acidified FeSO4 into the propeller wash of the ship steaming along tracks at intervals of 1-3 km, for instance, spiralling outward from a drifting, surface-tethered buoy. One would expect the weakly acidified iron solution to be quickly neutralized by mixing with alkaline seawater and the dissolved iron oxidized to its insoluble state, i.e. colloidal rust particles that would be difficult for...

The concept of iron limitation

Iron has long been suspected to be a growth-limiting factor in the ocean based on well-established facts its conversion to highly insoluble ferric hydroxide (rust) in alkaline, oxygenated seawater and its obligate requirement by all organisms. Furthermore, the consistently higher plankton productivity of near land compared with open ocean waters of the SO was taken as evidence for the provisioning of trace elements (including iron) from the land and their limiting role away from it (Hart 1942)....

CO2 fuels

The production of synthetic fuels via CO2 hydrogenation requires hydrogen addition and oxygen removal (Inui 1996). We consider the production of octane (C8H18) as a simple proxy for synthetic fuels that could replace current automobile gasoline in practice, fuels with a range of hydrocarbons of approximately this molecular Table 7.1 Comparison of synthetic fuels from CO2 hydrogenation (HHV Lide 2000) Table 7.1 Comparison of synthetic fuels from CO2 hydrogenation (HHV Lide 2000) b Molar ratio...

An example

We are currently developing an air-capture process based around NaOH capture with a titanate-based hydroxide regeneration system (Keith et al., 2005 Stolaroff etal., 2008 Mahmoudkhani and Keith, 2009). This is a multistep chemical process with many components similar to or identical to existing components used in current chemical processes. The first step in the process is a system that contacts a strong hydroxide solution with atmospheric air, referred to as the contactor. This device will...