Net energy analysis must not compare apples and oranges

Energy return on investment (EROI) is a critical measure of the comparative utility of different energy carriers including fossil fuels and renewables. However it must not be used to compare carriers that cannot be put to similar end-use. Additionally, combining carriers to arrive at estimates of ‘average’ or ‘minimum’ EROIs can be problematic

Energy pay-back time: methodological caveats and future scenarios

Energy pay-back time (EPBT) has almost universally been adopted as the indicator of choice to express the energy performance of photovoltaics (PV). In this paper, an in-depth review of the methodology and all underlying assumptions and conventions is presented. A prospective analysis of the potential evolution of the EPBT of PV over the next four decades is then performed, assuming optimistic grid penetration figures and taking into account expected technological improvements. Results show that combining the two opposing effects of a reduction in cumulative energy demand for PV manufacturing and an increase in grid efficiency will likely result in severely limited reductions, or even possible increases, in the EPBT of PV. This is entirely due to how EPBT is operationally defined, and it has nothing to do with the actual energy performance of PV in the future

Addressing a Counterproductive Dichotomy in the Energy Transition Debate

There appears to be growing polarization in a large swath of the recent scientific literature on the renewable energy transition, where two opposed “camps” may be identified, i.e. that of the “systemic pessimists”, who champion the broad concepts of carrying capacity and the limits to growth, but often harbour what appears to be pre-conceived scepticism towards renewable energies, and that of the “technological optimists”, who instead typically focus more narrowly on the immediate goal of phasing out fossil fuels, and see great potential for renewable energies to achieve that, but often fail to address other issues of ultimate planetary limits. It is argued here that this is a false dichotomy that is damaging to the reputation of both “camps”, and which risks devaluing and trivializing the most important question of all, namely how to achieve long-term sustainability. This paper calls for the rekindling of a more constructive debate that starts from the recognition that both sets of core arguments (respectively, those centred on the limits to growth and those pointing to the viability of renewable energies) are often simultaneously true, and which moves the goalposts further, to establish to which extent a more sustainable future is indeed possible, and which systemic changes (including, but not limited to, phasing out fossil fuels) will be required to achieve it

A prospective net energy and environmental life-cycle assessment of the UK electricity grid

National Grid, the UK’s largest utility company, has produced a number of energy transition scenarios, among which “2 degrees” is the most aggressive in terms of decarbonization. This paper presents the results of a combined prospective net energy and environmental life cycle assessment of the UK electricity grid, based on such a scenario. The main findings are that the strategy is effective at drastically reducing greenhouse gas emissions (albeit to a reduced degree with respect to the projected share of “zero carbon” generation taken at face value), but it entails a trade-off in terms of depletion of metal resources. The grid’s potential toxicity impacts are also expected to remain substantially undiminished with respect to the present. Overall, the analysis indicates that the “2 degrees” scenario is environmentally sound and that it even leads to a modest increase in the net energy delivered to society by the grid (after accounting for the energy investments required to deploy all technologies)

Life-cycle carbon emissions and energy return on investment for 80% domestic renewable electricity with battery storage in California (U.S.A.)

This paper presents a detailed life-cycle assessment of the greenhouse gas emissions, cumulative demand for total and non-renewable primary energy, and energy return on investment (EROI) for the domestic electricity grid mix in the U.S. state of California, using hourly historical data for 2018, and future projections of increased solar photovoltaic (PV) installed capacity with lithium-ion battery energy storage, so as to achieve 80% net renewable electricity generation in 2030, while ensuring the hourly matching of the supply and demand profiles at all times. Specifically—in line with California’s plans that aim to increase the renewable energy share into the electric grid—in this study, PV installed capacity is assumed to reach 43.7 GW in 2030, resulting of 52% of the 2030 domestic electricity generation. In the modelled 2030 scenario, single-cycle gas turbines and nuclear plants are completely phased out, while combined-cycle gas turbine output is reduced by 30% compared to 2018. Results indicate that 25% of renewable electricity ends up being routed into storage, while 2.8% is curtailed. Results also show that such energy transition strategy would be effective at curbing California’s domestic electricity grid mix carbon emissions by 50%, and reducing demand for non-renewable primary energy by 66%, while also achieving a 10% increase in overall EROI (in terms of electricity output per unit of investment)

Prospective LCA of the production and EoL recycling of a novel type of Li-ion battery for electric vehicles

The transport sector as a whole – and within it passenger cars in particular – is currently responsible for a large share of the total greenhouse gas emissions of many developed and developing countries, and a transition to electric vehicles (EVs) is often seen as a key stepping stone towards the de-carbonization of personal mobility. Research is on-going in the continuous development and improvement of lithium ion (Li-ion) batteries, which may use a range of several different metals in conjunction with lithium itself, such as: lithium manganese oxide (LMO), lithium iron phosphate (LFP), lithium nickel cobalt manganese oxide (NCM), and lithium nickel-cobalt-aluminium oxide (NCA). Within the MARS-EV research project, a new cell chemistry has been developed and tested, using a lithium cobalt phosphate (LCP) formulation. This work presents the first life cycle assessment (LCA) for such LCP batteries, including a newly-developed hydrometallurgical battery recycling process which enables the end-of-life recovery of not only the valuable metals, but also of the graphite component, thereby avoiding the associated CO2 emissions

Dealing with waste products and flows in life cycle assessment and emergy accounting: methodological overview and synergies

This paper considers the different approaches taken in dealing with waste products and flows in Life Cycle Assessment (LCA) and Emergy Accounting (EMA), from a methodological point of view, and aims to develop more standardized and synergistic procedures. LCA deals with the waste issue from the point of view of the impact of their disposal, as well as the potential benefit (‘environmental credit’) afforded by the avoided extraction and processing of additional primary resources when waste is recycled or its energy content recovered. The ‘environmental burden’ associated to the entire production and consumption chain leading to the waste item is generally not included in LCAs of waste management systems, due to the boundary being placed – consistently with the intended goal – around the actual disposal processes (including recycling alternatives and associated environmental credits). Instead, Emergy Accounting, a donor-side approach with its implicit boundary set at the biosphere level, in principle keeps track of the entire supply-chain at all times, considering even waste flows as products (or co-products), and calculating their intensity factors and assessing their role within the ecosystem's web and hierarchy. However, when the focus is limited to evaluating processes under human control, within the narrower space and time boundary of human-dominated production and consumption processes, waste products can arguably be regarded as something to be recycled or disposed of to minimize the environmental burden. When this is the case, and particularly in comparative analyses, the emergy perspective thus becomes closer to the LCA perspective and interesting methodological synergies may emerge. A clearly defined set of emergy algebra rules for waste products and flows, and specifically for recycling, was found to be still lacking in the available emergy literature. We propose here that a better and more consistent methodological solution may be arrived at by leveraging the work done in LCA

Single-use vs reusable transport packaging: a comparative life cycle analysis

This paper deals with a comparative analysis of two different packaging and transport scenarios, which exemplifies the mplications of choosing between single-use and reusable packaging. In particular, transport of a batch of chemicals by means of disposable fibre drums vs. reusable steel drums is investigated from a life cycle perspective, and the associated environmental impact in terms of Global Warming Potential, Acidification Potential, Gross Energy Requirement and solid waste generation is assessed. Results prove beyond reasonable doubt that, even in the case of durable packaging containers requiring the use of comparatively energy-intensive materials for their production, the reuse scenario is characterized by lower environmental impact indicators across the board, and as such is the most advisable and environmentally sound option.Postprint (author’s final draft