Energy, fossil fuels, and environmental impacts

From the ancestral manmade fires used for heating, cooking, and lighting, to the experimental nuclear fusion reactors of the 21^st century, energy has always been the engine of human activities. Thermodynamically speaking, energy is a physical change, meaning that it can never be “produced” sensu stricto, only converted.

Energy comes in different forms – kinetic, potential, mechanical, electric, nuclear, magnetic, etc. – that can be used in combination or after conversion from one to another in a plethora of industrial applications. The electric form of energy is

and of global mitigation policymaking (Section 3.1 in Intergovernmental Panel on Climate Change (2000)).

3 particularly convenient as it allows long-distance distribution without substantial loss, it is scalable, and easily convertible to heat (e.g. using resistors) or work (e.g.

using engines). Energy conversion is omnipresent in human activities, and it has actually been observed that energy use explains economic growth in a much better way than the two classical factors of production, capital and labour, do (Stern 2011; Ayres and Voudouris 2014; Giraud and Kahraman 2014). As of 2014, more than 80% of the global primary energy supply consists of fossil fuels (International Energy Agency 2015). As such, energy conversion and supply is the main cause of greenhouse gas emissions; in particular, electricity generation represents 25% of the anthropogenic greenhouse gas emissions in 2010, and 47% of the global 10 Gt C increase from 2000 to 2010. The unbridled use of fossil fuels since the industrial era has contributed singlehandedly to increasing the global warming potential of our atmosphere by releasing the products of their combustion.

Perhaps more worrisome, the IPCC reports that the “increased use of coal relative to other energy sources has reversed the long-standing trend of gradual decarbonisation of the world’s energy supply” (IPCC 2014b), coal combustion alone eclipsed the entirety of global mitigation efforts. This indicates clearly that phasing out coal combustion (or at least capturing the greenhouse gas emissions thereof) is, or should be, the top priority in global policy, and one of the most significant parameters in energy scenarios.

A large-scale deployment of low-carbon energy supply, together with a reduction of energy demand, appears to be necessary to achieve a shift that would keep global warming below 2°C. Furthermore, this deployment needs to occur urgently; any fossil-fired power plant built today (without carbon dioxide capturing equipment) will only further jeopardize the world’s capability to reach current climate targets.

The many greenhouse gas-reducing options available to society range over a wide spectrum of mitigation potential and economic costs. In general, most end-use efficiency improvement measures come at a negative cost (i.e. with economic co-benefits), while a global energy transition requires massive investments (see Figure 3), in monetary and material terms. Societies simply cannot afford a second energy

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transition after the upcoming one, at least fossil-based, either environmentally or even economically.

Figure 2. Electricity mix and greenhouse gas emissions.a) Allocation of total GHG emissions in 2010 (49.5 Gt CO2 eq/yr) across industrial sectors. Electricity and heat production contributes the most. b) Allocation of the same total emissions to reveal how each sector’s total increases or decreases when adjusted for indirect emissions. c) Total annual anthropogenic greenhouse gas emissions (Gt CO2 eq./yr) by group of gases 1970–2010, along with associated uncertainties (whiskers). From IPCC (2014b).

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Figure 3. Global GHG abatement cost curve beyond a business-as-usual scenario in 2030. Adapted from McKinsey & Company (2010).

With the large-scale deployment of a technology appears its learning curve (or experience curve): the observation that each doubling of the installed capacity will reduce the cost of installation by a fixed rate, mainly through process improvement and economy of scale mechanisms. Photovoltaics have for example followed their own “Moore’s law” (in which the reduction is correlated with time rather than capacity) quite faithfully for the past 50 years; the cost of the installed kilowatt of solar panels has been decreasing by roughly 10% a year since the 1970s (Farmer and Lafond 2016). Furthermore, some technologies undergo fast efficiency improvements. To take the example of photovoltaics again, this phenomenon is well illustrated by the National Renewable Energy Laboratory of the United States’ (NREL) efficiency chart plotting the maximum efficiency attained for each photovoltaic technology, continuously updated² . Of course, these constant efficiency improvements are also a factor of cost reduction, entertaining the learning curve. These effects are taken into account in the scenarios from the International Energy Agency (IEA) used in this thesis.

2 Latest update available at http://www.nrel.gov/ncpv/images/efficiency_chart.jpg

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Figure 4. Published electricity-related LCA studies, comparison with the whole body of LCA literature. Source: Scopus, total results for the queries “life cycle assessment” and “life cycle assessment of electricity”, and the 5-year average ratio of annual results, as of early 2016.

Archetypal of the climate-energy-resource conundrum, fossil fuels have attracted the attention of life cycle assessment practitioners, especially since the emergence of fossil-free and low-carbon options for stationary power generation. The diversification of commercially available options indeed offers great opportunities for energy planning, to which environmental assessments may be of great relevance as decision-support tools. Life cycle assessment is also an adequate way to compare fossil and renewable electricity generation on a fair basis, since most impacts occur during the use phase for the former, and the production phase for the latter. Unsurprisingly, the 2005-2015 decade has seen a boom in electricity-related environmental assessment, particularly life cycle assessment (LCA), publications in academic journals. As seen in Figure 4, LCA studies of electricity systems (or related, including grid, storage, efficiency…) represented about 4 in 100 LCA publications in 2005, up to almost 1 in 10 in 2015. This rise in interest for the assessment of electricity systems has been accompanied by an increase in available life cycle inventory (LCI) data, as well as inevitable discrepancies across primary data, adapted data, and results made available in the recent literature. To remediate the disparity of data, detrimental to the studies’ comparability, harmonization efforts have recently been undertaken. NREL has carried out a

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7 major harmonization project of published studies of renewable energy (Heath et al. 2014), summarised in a 2012 special issue of the Journal of Industrial Ecology (Lifset 2012). Life cycle assessment studies often vary in the characteristics of analysed technologies, and the method they employ to compute results.

Harmonisation (and more specifically meta-analyses) aims at streamlining these characteristics and methods to bring coherency in the growing pool of LCA results, allowing for comparison and decision support in a policy-making context.

It is partly with these streamlining challenges in mind that the work presented here has been carried out.