Useful Exergy as an Intermediate Input in a Two-Sector Model of the United States Economy

Conventional economic growth models treat production/consumption as abstractions linked only by money flows, disregarding their connection to the physical world. Nevertheless, the existing literature suggests that energy flows can influence production and links useful exergy prices with economic growth. Useful exergy is energy measured at the stage where it produces an end-use (and is a measurement of energy quality). Not all approaches in the literature use this metric and they often consider energy as a primary input (despite it being an intermediate input). We explore the relationship between energy flows and economic growth for the US through a framework where useful exergy, the output of an “extended energy sector” (where all effects of increasing primary-to-final-to-useful exergy efficiency are located), is an intermediate input for a “non-energy sector”. Together, they encompass the entire economy. We conclude that the share of investment in the extended energy sector grew with the overall economic growth throughout 1960–2020, while the labour share decreased. The non-energy sector contributed the largest share of consumption, exports, imports and labour. In recent years, the energy sector has overtaken it in terms of investment. Our two-sector model has important implications for current climate policy, namely regarding the Integrated Assessment Models on which it is based

An ecological-thermodynamic approach to urban metabolism : measuring resource utilization with open system network effectiveness analysis

Cities have evolved as centers of economic growth and often described as open systems where the intake of resources is heavily dependent on flows imported from the external environment. The question is, how much of the resource available in cities is effectively utilized? In response, this paper develops an ecological-thermodynamic approach to assess the ability of a system to make full use of the resources available and reduce the demand for new resources. In this work, open system network effectiveness analysis is introduced as a novel assessment method to investigate the cities’ producer and consumer behaviors by studying the resource flow connections and the interactions between the socio-economic sectors. Investigation on the urban flows network evaluates the ability of the system to utilize the resource imported through the effectiveness of utilization indicator and the ability to convert the resource imported to useful products through the effectiveness of conversion indicator. The effectiveness indicators, utilization and conversion, represent the consumption and production characteristics of the system respectively. This is tested through a case study conducted for Singapore city over the time period 2005-2014. The effectiveness results show that the city, on average, has utilized 45% of the maximum extractable usefulness from the resources imported throughout the years, with the lowest effectiveness, 39%, and the highest effectiveness, 50%, in the years 2007 and 2014 respectively. The trajectory of effectiveness results throughout the years suggests a trade-off relationship between the producers and consumers to balance the production and consumption of resources in the city

Mapping resource effectiveness across urban systems

Cities and their growing resource demands threaten global resource security. This study identifies the hotspots of imports in cities to redirect resources to where they are most needed, based on the system overall resource effectiveness to maximise the use of all resources available. This paper develops a taxonomy of resource-use behaviour based on the clustering patterns of resource utilisation and conversion across interconnected urban systems. We find high tendencies of consumer-like behaviour in a multi-city system because tertiary sectors are concentrated in urban areas while the producing sectors are located outside and hence, results in high utilisation but low output. The clustering taxonomy emphasises that the absence of producers in the system causes cities to rely on the imported resources for growth. Cities can be resource-effective by having a more diversified industrial structure to extend the pathways of resource flows, closing the circularity gap between the suppliers and consumers

Estimation of useful-stage energy returns on investment for fossil fuels and implications for renewable energy systems

The net energy implications of the energy transition have so far been analysed at best at the final energy stage. Here we argue that expanding the analysis to the useful stage is crucial. We estimate fossil fuelsʼ useful-stage energy returns on investment (EROIs) over the period 1971–2020, globally and nationally, and disaggregate EROIs by end use. We find that fossil fuelsʼ useful-stage EROIs (~3.5:1) are considerably lower than at the final stage (~8.5:1), due to low final-to-useful efficiencies. Further, we estimate the final-stage EROI for which electricity-yielding renewable energy would deliver the same net useful energy as fossil fuels (EROI equivalent) to be approximately 4.6:1. The EROIs of electricity-yielding renewable energy systems, based on published estimations, are found to be higher than the determined EROI equivalent, even considering the effects of intermittency under a range of energy transition scenarios. Results suggest that the energy transition may happen without a decline in net useful energy, countering the view that renewable energy systems cannot replace fossil fuels without incurring a substantial energy penalty

Integrated assessment modelling of degrowth scenarios for Australia

Empirical evidence increasingly indicates that to achieve sufficiently rapid decarbonisation, high-income economies may need to adopt degrowth policies, scaling down less-necessary forms of production and demand, in addition to rapid deployment of renewables. Calls have been made for degrowth climate mitigation scenarios. However, so far these have not been modelled within the established Integrated Assessment Models (IAMs) for future scenario analysis of the energy-economy-emission nexus, partly because the architecture of these IAMs has growth ‘baked in’. In this work, we modify one of the common IAMs–MESSAGEix–to make it compatible with degrowth scenarios. We simulate scenarios featuring low and negative growth in a high-income economy (Australia). We achieve this by detaching MESSAGEix from its monotonically growing utility function, and by formulating an alternative utility function based on non-monotonic preferences. The outcomes from such modified scenarios reflect some characteristics of degrowth futures, including reduced aggregate production and declining energy and emissions. However, further work is needed to explore other key degrowth features such as sectoral differentiation, redistribution, and provisioning system transformation

Downscaling down under: towards degrowth in integrated assessment models

IPCC reports, to date, have not featured ambitious mitigation scenarios with degrowth in high-income regions. Here, using MESSAGEix-Australia, we create 51 emissions scenarios for Australia with near-term GDP growth going from +3%/year to rapid reductions (−5%/year) to explore how a traditional integrated assessment model (IAM) represents degrowth from an economic starting point, not just energy demand reduction. We find that stagnating GDP per capita reduces the mid-century need for upscaling solar and wind energy by about 40% compared to the SSP2 growth baseline, and limits future material needs for renewables. Still, solar and wind energy in 2030 is more than quadruple that of 2020. Faster reductions in energy demand may entail higher socio-cultural feasibility concerns, depending on the policies involved. Strong reductions in inequality reduce the risk of lowered access to decent living services. We discuss research needs and possible IAM extensions to improve post-growth and degrowth scenario modelling

Global energy consumption of the mineral mining industry: Exploring the historical perspective and future pathways to 2060

The mining industry globally is responsible for significant energy consumption, and is an important source of greenhouse gas emissions. Considering that future mineral demand is likely to increase and that the final energy consumption per unit mass of mineral extracted (energy intensities of mining) is also forecast to increase as a result of a decrease in mineral resource deposit qualities, the mining industry’s final energy consumption will increase in the future. But the scale of that future increase remains unexplored. In this study, we (i) provide the first bottom-up assessment of the mining industry’s final energy consumption globally (1971–2015), (ii) use 1.5°C consistent socio-economic scenarios to conduct an exploratory study of future possible pathways for the mining industry’s final energy consumption, and (iii) review the extent to which such energy consumption is considered in energy-economy models. We find that the mining industry is currently responsible for approximately 1.7% of global final energy consumption. However, the mining industry’s final energy consumption is likely to increase significantly, by a factor in the range 2–8 by 2060, depending on the future economic trajectory, on the evolution of energy intensities, and on future recycling rates. We also find that mineral material flows and their associated energy requirements (including the mining industry’s energy consumption) are insufficiently covered in many energy-economy models. Our work suggests that the limited representation of material flows and associated energy requirements is currently an important blind spot in energy-economy modelling and may hinder the efforts of the community to build consistent energy transition pathways

Exploring the effects of mineral depletion on renewable energy technologies net energy returns

The energy transition poses a set of new challenges related to mineral scarcity and depletion. The process of mineral depletion is notably characterised by increasing energy consumption per tonne of valuable minerals mined (i.e. energy intensity of mining), due to the decline in the quality of mined deposits. As renewable energy technologies are heavily reliant on a range of minerals, some of them scarce, the net energy returns (i.e., the share of energy available to provide energy services) of renewable energy technologies may be significantly affected by this decline.the increases in the energy intensities of mining therefore raise the question of how the future net energy returns of renewable energy technologies may be affected. This may in turn jeopardize the ability of renewable energy technologies to provide sufficient net energy, and hence, support decent living standards. The aim of this article is therefore toIn response, we explore, using net energy analysis techniques combined with Life Cycle Analysis data, the effects of mineral depletion on the net energy returns of four renewable energy technologies: solar photovoltaic, concentrated solar power, onshore wind, and offshore wind. The results indicate that the effects of mineral depletion on the net energy returns of renewable energy technologies will be marginal. Indeed, even for very high increases in the energy intensities of mining, the share of net energy returns decreases by less than 3 percentage points by 2060 for each technology analysed — 2.3% for wind offshore, 1.6% for solar photovoltaic and concentrated solar power, and 1.1% for wind onshore. These results are validated with a Monte Carlo simulation conducted on the energy intensities of mining. In addition, the article discusses that technological factors, such as improvements in metallurgical energy efficiencies and material intensities of manufacturing have the potential to somewhat offset the effects of mineral depletion. Hence, although constraints related to mineral scarcity and depletion may be critical for the energy transition, concerns regarding the impacts of these issues on the net energy returns of renewable energy appear to be unfounded