Global hydrogen reservoirs in basement and basins

The authors are grateful to the Science and Technology Facilities Council (STFC) for funding, through Grant NE/G00322X/1. Samples were kindly contributed by K. Condie, M.J. Hole, and D. Muirhead. We are grateful to reviewers for their criticism.Peer reviewedPublisher PD

Hydrogen from Radiolysis of Aqueous Fluid Inclusions during Diagenesis

Acknowledgments We are grateful to J. Bowie and J. Still for skilled technical support and the staff at ICL-UK’s Boulby mine (especially Thomas Edwards), STFC’s Boulby underground Laboratory and the UK Centre for Astrobiology MINAR programme team (especially Sean Paling) for their support and supervised access to the site. The critical comments of two reviewers helped to improve the manuscript. Author Contributions John Parnell undertook the sampling. Nigel Blamey performed all analytical work. John Parnell wrote the manuscript.Peer reviewedPublisher PD

Reactivation of Limestone-Derived Sorbents using Hydration: Preliminary Results From a Fluidised Bed

A simple method of CO~2~ capture is by using the calcium looping cycle. The calcium looping cycle uses CaCO~3~ as a CO~2~ carrier, via the reversible reaction CaO(s) + CO~2~(g) = CaCO~3~(s), to extract CO2 from the exhaust stream and provide a pure stream of CO~2~ suitable for sequestration. 
A problem associated with the technology is that the capacity of the sorbent to absorb CO~2~ reduces significantly with the number of cycles of carbonation and calcination. The energy penalty of the cycle is considerably increased by cycling unreacted sorbent: hydration of unreactive sorbent has emerged as a promising strategy of reducing this penalty by regenerating the reactivity of exhausted sorbent.
A small atmospheric pressure fluidised bed reactor has been built and tested, that allows repeated cycling between two temperatures up to 1000 °C. 
Work presented here focuses on the effects of variation of the calcination temperature before hydration. Hydration has been found to more than double the reactivity of a spent sorbent cycled under the mildest conditions studied (calcination temperature of 840 °C). However, as calcination temperature is increased the observed reactivation decreases until little reactivation is observed for the sorbent cycled at 950 °C. The primary reason for this appears to be a substantial increase in friability of particles, with reactivity normalised for mass losses appearing similar independent of cycling temperature

Evidence for Seismogenic Hydrogen Gas, a Potential Microbial Energy Source on Earth and Mars

M thanks the STFC for a PhD studentship and the NASA Astrobiology Institute for additional funding (NNAI13AA90A; Foundations of Complex Life, Evolution, Preservation and Detection on Earth and Beyond). Alison Wright, Roger Gibson and Edward Lynch are thanked for contributing samples. We thank three anonymous reviewers for their insightful comments.Peer reviewedPostprin

Sampling methane in basalt on Earth and Mars

Peer reviewedPublisher PD

Valuing remnant vegetation in Central Queensland using choice modelling

In the Desert Uplands region of Central Queensland, many pastoralists are clearing vegetation in order to improve cattle grazing production. A choice modelling study was undertaken to provide estimates of the benefits of retaining remnant vegetation that are appropriate for inclusion in a cost benefit analysis of tighter clearing restrictions. Attributes included in the choice model were reductions in the population size of non‐threatened species, the number of endangered species lost to the region, and changes in regional income and employment. A nested logit model was used to model the data in order to avoid violations of the independence of irrelevant alternatives condition. The estimated benefits are reported for several tree clearing policy regimes that are more stringent than those currently applied.Resource /Energy Economics and Policy,

Methane in sulphides from gold-bearing deposits, Britain and Ireland

We are grateful to J. Armstrong and C. Rice for provision of samples. J. Johnston is thanked for skilled technical support.Peer reviewedPostprin

A shrinking core model for steam hydration of CaO-based sorbents cycled for CO2 capture

Calcium looping is a developing CO2 capture technology. It is based on the reversible carbonation of CaO sorbent, which becomes less reactive upon cycling. One method of increasing the reactivity of unreactive sorbent is by hydration in the calcined (CaO) form. Here, sorbent has been subjected to repeated cycles of carbonation and calcination within a small fluidised bed reactor. Cycle numbers of 0 (i.e., one calcination), 2, 6 and 13 have been studied to generate sorbents that have been deactivated to different extents. Subsequently, the sorbent generated was subjected to steam hydration tests within a thermogravimetric analyser, using hydration temperatures of 473, 573 and 673 K. Sorbents that had been cycled less prior to hydration hydrated rapidly. However, the more cycled sorbents exhibited behaviour where the hydration conversion tended towards an asymptotic value, which is likely to be associated with pore blockage. This asymptotic value tended to be lower at higher hydration temperatures; however, the maximum rate of hydration was found to increase with increasing hydration temperature. A shrinking core model has been developed and applied to the data. It fits data from experiments that did not exhibit extensive pore blockage well, but fits data from experiments that exhibited pore blockage less well

Cement, CCS and CO2 Uptake, Including an Update on the EU LEILAC Project

Portland cement manufacture is responsible for around 7% of anthropogenic CO2 emissions, a percentage which is rising. The majority of direct emissions come from the calcination of limestone to form calcium oxide and calcium silicates, the main constituent of Portland cement. However, after cement is hydrated to make concrete, it can react with carbon dioxide in the air to re-form calcium carbonate, completing a cycle. This carbonation mechanism can be measured and the rate at which the global inventory of concrete absorbs CO2 can be estimated – the results of such an exercise will be shown in this presentation. That said, concrete carbonation only counterbalances a small fraction of emissions from concrete production, the majority of which come from cement manufacture. Incremental improvements in composition and efficiency are not sufficient to reduce CO2 emissions by the extent necessary to hit a 1.5–2 °C temperature rise target – CCS is the only practical technology to achieve this ambition. The technological options for the cement-CCS will be presented. Three options – calcium looping, an oxy-fueled kiln, and direct capture – will be described and discussed in depth, including discussion of the effects of various highly integrated processes on the strength and other properties of the cement produced; for calcium looping and oxyfueled kilns, it will be shown that there are negligible effects on the quality of the cement produced. Direct Capture will be presented and discussed in detail, as part of a recently funded project in the process of producing results. This process is being developed as part of Leilac (Low Emissions Intensity Lime and Cement), a EU Horizon 2020 research and innovation project. This €21m project has received €12m from the EU (H2020 No 654465), with the balance provided by the consortium partners. It runs for five years from 2016 to 2020 and the project team includes industrial, technology and research & development partners. The objective is to pilot a breakthrough carbon capture technology that can capture the process emissions from the calcination of limestone, without imposing a significant energy or capital penalty. The pilot plant will be hosted by Heidelberg Cement at Lixhe in Belgium. Imperial College is carrying out research on the kinetics of calcination under the conditions of interest, suitability of product for destination industries, defining reference technologies for modelling and modelling of the radiative heat transfer in the reactor. Here, we shall present an overview of the project and the current status

Paradigm shift in determining Neoproterozoic atmospheric oxygen

ACKNOWLEDGMENTS We thank the Geological Survey of Australia for permission to sample the Empress 1A and Lancer 1 cores, the Natural Sciences and Engineering Research Council of Canada for financial support (grant #7961–15) of U. Brand, and the National Natural Science Foundation of China for support of F. Meng and P. Ni (grants 41473039 and 4151101015). We thank M. Lozon (Brock University) for drafting and constructing the figures. We thank the editor, Brendan Murphy, as well as three reviewers (Steve Kesler, Erik Sperling, and an anonymous reviewer), for improving the manuscript into its final form.Peer reviewedPublisher PD