In recent years, Carbon Capture and Storage (Sequestration) (CCS) has been proposed as a potential method to allow the continued use of fossil-fuelled power stations whilst preventing emissions of CO 2 from reaching the atmosphere. Gas, coal (and biomass)-fired power stations can respond to changes in demand more readily than many other sources of electricity production, hence the importance of retaining them as an option in the energy mix. Here, we review the leading CO 2 capture technologies, available in the short and long term, and their technological maturity, before discussing CO 2 transport and storage. Current pilot plants and demonstrations are highlighted, as is the importance of optimising the CCS system as a whole. Other topics briefly discussed include the viability of both the capture of CO 2 from the air and CO 2 reutilisation as climate change mitigation strategies. Finally, we discuss the economic and legal aspects of CCS.

We present a framework for PERMANOVA power estimation tailored to marker-gene microbiome studies that will be analyzed by pairwise distances, which includes: (i) a novel method for distance matrix simulation that permits modeling of within-group pairwise distances according to pre-specified population parameters; (ii) a method to incorporate effects of different sizes within the simulated distance matrix; (iii) a simulation-based method for estimating PERMANOVA power from simulated distance matrices; and (iv) an R statistical software package that implements the above. Matrices of pairwise distances can be efficiently simulated to satisfy the triangle inequality and incorporate group-level effects, which are quantified by the adjusted coefficient of determination, omega-squared (ω2). From simulated distance matrices, available PERMANOVA power or necessary sample size can be estimated for a planned microbiome study.

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Using biomass to provide energy services is a strategically important option for increasing the global uptake of renewable energy. Yet the practicalities of accelerating deployment are mired in controversy over the potential resource conflicts that might occur, in particular conflicts over land, water, and biodiversity conservation. This calls into question whether policies to promote bioenergy are justified. Here we examine the assumptions on which global bioenergy resource estimates are predicated. We find there is a disjunct between the evidence that global bioenergy studies can provide and policy makers' desire for estimates that can straightforwardly guide policy targets. We highlight the need for bottom-up assessments informed by empirical studies, experimentation, and cross disciplinary learning in order to better inform the policy debate. 1 Conflicting aspirations for bioenergyUsing biomass to provide energy services is one of the most versatile options for increasing the global uptake of renewable energy and an important component in many climate change mitigation and energy supply scenarios [1][2][3][4] . The International Energy Agency (IEA), for example, estimates that biomass could contribute an additional 50EJ (~10%) to global primary energy supply by 2035, and states that "the potential supply could be an order of magnitude higher" 4 . Governments of the world's largest economies have also introduced policies to incentivise bioenergy deployment, motivated by concerns about energy security and climate change, and by the desire to stimulate rural development 5,6 . Yet the potential contribution from biomass to global energy supply is controversial. Sources of contention include concern about the inter-linkages between biomass, bioenergy and other systems. Most notably, land and resource conflicts are foreseen between bioenergy and food supply, water use, and biodiversity conservation. The fear is that the benefits offered by increased biomass use will be outweighed by the costs [7][8][9][10] . It is also argued that the wide range of estimates of biomass potential and the lack of standardised assessment methodologies confuses policy makers, impedes effective action and fosters uncertainty and ambivalence 11 . These broad points contribute to a general sense of unease about the future role of bioenergy, and whether it presents a genuine opportunity or is a utopian (or for some dystopian) vision that stands little chance of being realised.Here we analyse how scenarios for increasing bioenergy deployment are contingent on anticipated demand for food, energy, and environmental protection, and expectations of technological advances. We use a systematic review methodology 12,13 to identify and analyse the most influential estimates of the global bioenergy potential that have been published over the last 20 years. The technical and sustainability assumptions that lie behind these estimates are exposed and their influence on calculations of potential described. We find that the range of estimates is primar...

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An effective energy technology strategy has to balance between setting a stable long term framework for innovation, while also responding to more immediate changes in technology cost and performance. Over the last decade, rather than a steady progression along an established learning curve, PV costs and prices have been volatile, with increases or plateaus followed by rapid reductions. The paper describes, and considers the causes of, recent changes in PV costs and prices at module and system level, both international trends and more place-specific contexts. It finds that both module and system costs and price trends have reflected multiple overlapping forces. Established forecasting methodsexperience curves and engineering assessmentshave limited ability to capture key learning effects behind recent PV cost and price trends: production scale effects, industrial reorganization and shakeouts, international trade practices and national market dynamics. These forces are likely to remain prominent aspect of technology learning effects in the foreseeable futureand so are in need of improved, more explicit representation in energy technology forecasting.

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