Paper II: Interpretation

3.2.1 RATIONALE

Literature is scarce when it comes to describing and quantifying the environmental consequences of climate change mitigation in a consistent way. In particular, the energy sector will have to undergo massive changes, driven by regional policies that mainly base their decisions on economic arguments. For example, the levelised costs of electricity technologies or the implementation of carbon taxes could play a determinant role in steering energy policies one way or another. A consequence of this economic focus is the negligence of the broader picture, of the full “due diligence” of such policies: what is the stress of such a shift on the biosphere? Can society afford deeply changing energy systems with regard to available materials and resources?

On top of that, the life cycle assessment literature abounds with results on specific technologies, often analysed in a specific context and reliant on study-specific assumptions and idiosyncratic choices of method and background inventory data.

Comparisons between variants of technologies are often imbued with uncertainty, which weakens the general insights offered by such studies. While harmonisation efforts have been conducted (Hsu et al. 2012; Whitaker et al. 2012; Heath et al.

2014), the lack of a unified assessment framework of electricity production technologies is regrettable still. Here we address this research gap.

3.2.2 OBJECTIVES

In this study, we propose a large-scale integrated assessment of future electricity systems. The main objectives, beyond demonstrating the relevance of integrated hybrid LCA for this type of exercise, are:

a. To harmonise heterogeneous hybrid life cycle data and integrate it in a consistent framework,

b. To quantify the environmental co-effects of climate change mitigation under stringent decarbonisation policies,

27 c. To identify the main upcoming challenges of the large-scale deployment of low carbon electricity generation, such as land use or material requirements, in a long-term and region-specific way.

d. To set an agenda for future research on the use of life cycle methods for informing climate change mitigation.

3.2.3 METHODS

The main core of the model used consists of THEMIS, the framework laid out in Paper I (Gibon et al. 2015). Principally, we apply the THEMIS framework to a range of electricity producing technology options, which are implemented to the model via the integration of their hybrid inventories. The exhaustive list of electricity-producing technologies is: photovoltaics (cadmium-telluride, copper-indium-gallium-selenide, polycrystalline silicon), concentrated solar power (parabolic trough, central tower), hydropower, wind power (onshore, offshore gravity-based and steel foundations), as well as coal- (subcritical, supercritical, integrated gasification combined cycle), natural gas-fired power plants (combined cycle). The two latter (fossil-fired) power plants are modelled with and without carbon dioxide capture and storage technology.

These technologies are assumed to represent the electricity mix of nine world regions from 2010 to 2050. Their life cycle inventory varies over this period, to represent improvements such as material efficiency (e.g. thinner photovoltaic modules for the same performance), energy efficiency (lower consumption or higher output), or recycling (either assuming recycling at the end-of-life or the use of recycled material at the fabrication stage). The databases used to represent the future economic and technological world is altered to reflect changes in industry efficiency or pollution control (see Paper I for details).

3.2.4 RESULTS

The paper presents the results of a large-scale, multiregional, integrated hybrid analysis of energy scenarios. Two main sets of results are shown: first, a technology comparison per unit generation, and, second, results of scenario modelling.

INFORMING CLIMATE CHANGE MITIGATION

28

The technology comparison focuses on the environmental impacts of energy technologies per kilowatt-hour provided to the electricity grid, with various background regions, years, and scenarios. The main finding for this first set is that low-carbon technologies have overall lower pollution-related environmental impacts than their fossil-fuelled counterparts. In addition to emitting greenhouse gases, fossil fuel, principally coal, combustion is indeed the source of a variety of other air pollution issues, such as particulate matter emissions, or photo-oxidant creation. Best available natural gas power plants may offer lower environmental impacts in general than coal-fired power plants, at the cost of higher life-cycle nitrogen oxide emissions. Nevertheless, bulk material requirements are higher for low-carbon technologies, namely for wind and solar power plants. This causes 20% to 50% of these technologies’ greenhouse gas emissions. Low-carbon technologies also tend to cause more system- or region-specific impacts than fossil-fuelled technologies: land occupation and natural habitat change depend mainly on the type of system chosen (e.g. ground- vs. roof-mounted for photovoltaics) or the region of implementation (e.g. boreal vs. tropical areas for hydropower, direct normal irradiance (DNI)⁷ for all solar technologies).

Scenario results compare the environmental impacts of the IEA Baseline scenario vs. those of the BLUE Map scenario. For both cases, and for the same variety of environmental impacts as in the technology comparison. It mainly highlight the role of coal power in the global future electricity mix, especially without the application of carbon dioxide capture and storage. Following the BLUE Map scenario would lead to lower environmental impacts globally, but higher (yet manageable) requirements of iron and steel, cement, and copper.

7 DNI is a measure of the amount of solar radiation at a given place; it is directly dependent on latitude, which represents the angle that the Earth’s surface makes with normal sunlight. In fact, the word “climate” itself comes directly from the Ancient Greek klima (κλίμα), which literally means “inclination, slope”.

29

3.2.5 UNCERTAINTY AND LIMITATIONS

Uncertainties mentioned in section 3.1, Paper I, are valid for this study:

uncertainties embedded in life cycle inventories and adjusted databases, as well as in the assumptions made for future mixes and system market shares. Sensitivity analysis was not performed, following the argument that the parameters tested in the study belong more to a storyline than an actual prediction. Data intensity was also a reason for not addressing the issue. The absence of any kind of uncertainty analysis is obviously a limitation, and the results of the study should be seen as an order-of-magnitude idea of the consequences of low-carbon electricity deployment.

3.2.6 POTENTIAL IMPACT OF STUDY

To the authors’ knowledge, the work presented in Paper II is the first attempt at framing and applying a fully integrated hybrid method for the assessment of a set of systems, with the inclusion of long-term scenarios and regional resolution.

Paper II is both a proof-of-concept for a new method and a rough estimate of future emissions and material requirements of a low-carbon electricity global society.