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A comparative assessment of GGR technologies

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  • Full or part time
    Dr N Mac Dowell
  • Application Deadline
    No more applications being accepted
  • Funded PhD Project (European/UK Students Only)
    Funded PhD Project (European/UK Students Only)

About This PhD Project

Project Description

Following the 2015 Paris Climate Commitment[1] and more recent developments in 2018[2], the world is comprehensively on a path to limiting climate change to “well-below 2C”.

In this context, it is understood that meeting these ambitious targets means rapidly transitioning to a net-zero carbon emission economy, and to a net-negative scenario shortly thereafter. This implies the deployment of so-called “Negative Emissions Technologies” at very significant scale, with some estimates implying a rate of atmospheric CO2 removal approaching 20 Gt/yr by the end of the century – a rate comparable to the current scale of total positive anthropogenic CO2 emissions.

Many Integrated Assessment Models (IAMs) rely heavily on bioenergy with CO2 capture and storage (BECCS) to deliver negative emissions. However, is important to recognise that there are several alternative options available[3], with so-called direct air capture (DAC) a rapidly emerging technology option.

There is an abundance of isolated analysis of greenhouse gas removal (GGR) technologies such as direct air capture (DAC) of CO2 and bioenergy with CCS (BECCS) in the academic and grey literature.

However, this work typically does not consider the multiple services provided by BECCS, and typically assigns all costs to either the power generation or carbon dioxide removal (CDR) service, implicitly assuming that the other service will be delivered free of charge. This is, of course, unlikely to be true, and therefore equitable comparison of these options requires quantitative assessment and assessment of all services provided.

This study proposes the comparative assessment BECCS and DAC using a 500 MWe pulverised fuel power plant combined with post-combustion CO2 capture using amine solvents as a reference case[4]. A range of biomass supply chains[5] will be considered so as to account for a representative range of CO2 removal and power generation values. The services provided by this technology include CDR and dispatchable, renewable power.

Similarly, in order to balance the two approaches, we will also evaluate a BECCS facility where all available heat and power is repurposed to power a DAC process, thus using all the bioenergy for CDR.

The DAC archetypes considered in this project will include both high- and low-temperature process [6]. For DAC to be equitably to BECCS, it will be required to generate an equivalent amount of power and remove an equivalent amount of atmospheric CO2 as the BECCS reference case. Importantly, all DAC archetypes require substantial amounts of heat as an input, and this study will consider a range of options for providing that heat, initially waste heat and natural gas, but thereafter other renewable sources of power. In these cases, the effect of location on DAC process cost and performance will be explicitly accounted for.

A third case for comparison would be a biomass combined heat and power process combined with CCS, evaluating a range of scales from the 10’s of MW to the GW-scale

All of these processes will then be compared on the basis of cost per tonne of CO2 removed, and avoided, in addition to the cost of heat and/or power generated.

Whilst the foregoing discussion will provide insight into the comparative costs of BECCS and DAC, it does not quantify the value provided by these different technologies in the context of a low carbon economy. To address this gap, we will build upon previous work and explicitly evaluate the value of the various BECCS and DAC technology in the context of a low carbon economy.

All of the forgoing work would be carried out at the process- and national-scales. However, the role and value of the various NETs will likely vary on a country-by-country and region-by-region basis. To provide insight into this regional variation in NETs value, we would propose to include the different GGR archetypes in the MONET framework[8]

The following skills are considered essential for this position

- Outstanding written and verbal communication skills
- Excellent mathematical ability, familiarity with mathematical programming in GAMS/AIMMS is an advantage
- A demonstrable familiarity with climate and energy systems challenges associated with deep decarbonisation

Interested candidates should apply directly to Dr Niall Mac Dowell ([Email Address Removed]) before July 31st 2019 with a copy of their CV and a cover letter explaining their interest in this opportunity.


3. Bui et al, “Carbon capture and storage (CCS): the way forward”, Energy and Environmental Science, 2018
4. Bui et al, “Bio-Energy with CCS (BECCS) performance evaluation: Efficiency enhancement and emissions reduction”, Applied Energy, 2017
5. See Fajardy and Mac Dowell, “Can BECCS deliver sustainable and resource efficient negative emissions?”, Energy and Environmental Science, 2017
6. See Daggash et al, “Closing the carbon cycle to maximise climate change mitigation: power-to-methanol vs. power-to-direct air capture”, Sustainable Energy and Fuels, 2018 for a discussion of these technologies
7. See for e.g., Heuberger et al., “A systems approach to quantifying the value of power generation and energy storage technologies in future electricity networks”, Com. Chem. Eng., 2017
8. See for e.g., Fajardy and Mac Dowell, Energy and Environmental Science, 2017, 2018 and 2018

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