Quantifying the energy consumption and greenhouse gas emissions of changing wastewater quality standards.

Regulations to ensure adequate wastewater treatment are becoming more stringent as the negative effects of different pollutants on human health and the environment are understood. However, treatment of wastewater to remove pollutants is energy intensive, so has added significantly to the operation costs of wastewater treatment plants. Analysis from six of the largest wastewater treatment works in South East England reveals that the energy consumption of these treatment works has doubled in the last five years due to expansions to meet increasingly stringent effluent standards and population growth. This study quantifies the relationship between energy use for wastewater treatment and four measures of pollution in effluents from UK wastewater treatment works (biochemical oxygen demand, ammoniacal nitrogen, chemical oxygen demand and suspended solids). The linear regression results show that indicators of these pollutants in effluents, together with the extension of plants to improve wastewater treatment, can predict over 95% of energy consumption. Secondly, using scenarios, the energy consumption and greenhouse gas emissions of effluent quality standards are estimated. The study finds that tightening effluent standards to increase water quality could result in a doubling of electricity consumption and an increase of between 1.29 and 2.30 additional MTCO2 per year from treating wastewater in large works in the UK.

Reaching a 1.5°C target: socio-technical challenges for a rapid transition to low-carbon electricity systems.

A 1.5°C global average target implies that we should no longer focus on merely incremental emissions reductions from the electricity system, but rather on fundamentally re-envisaging a system that, sooner rather than later, becomes carbon free. Many low-carbon technologies are surpassing mainstream predictions for both uptake and cost reduction. Their deployment is beginning to be disruptive within established systems. 'Smart technologies' are being developed to address emerging challenges of system integration, but their rates of future deployment remain uncertain. We argue that transition towards a system that can fully displace carbon generation sources will require expanding the focus of our efforts beyond technical solutions. Recognizing that change has social and technical dimensions, and that these interact strongly, we set out a socio-technical review that covers electricity infrastructure, citizens, business models and governance. It describes some of the socio-technical challenges that need to be addressed for the successful transition of the existing electricity systems. We conclude that a socio-technical understanding of electricity system transitions offers new and better insights into the potential and challenges for rapid decarbonization.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

Simulating flexibility, variability and decentralisation with an integrated energy system model for Great Britain.

Energy system models allow the development and assessment of ambitious transition pathways towards a sustainable energy system. However, current models lack adequate spatial and temporal resolution to capture the implications of a shift to decentralised energy supply and storage across multiple local energy vectors to meet spatially variable energy demand. There is also a lack of representation of interactions with the transport sector as well as national and local energy system operation. Here, we bridge these gaps with a high-resolution system-of-systems modelling framework which is applied to Great Britain to simulate differences between the performance of decarbonised energy systems in 2050 through two distinct strategies, an electric strategy and a multi-vector strategy prioritising a mix of fuels, including hydrogen. Within these strategies, we simulated the impacts of decentralised operation of the energy system given the variability of wind and across flexibility options including demand side management, battery storage and vehicle to grid services. Decentralised operation was shown to improve operational flexibility and maximise utilisation of renewables, whose electricity supplies can be cost-effectively converted to hydrogen or stored in batteries to meet peak electricity demands, therefore reducing carbon-intensive generation and the requirement for investment in expanding the electricity transmission network capacity.

Thirty years of climate mitigation: lessons from the 1989 options appraisal for the UK.

In April 1989, the UK Prime Minister, Margaret Thatcher, convened a full cabinet meeting on climate change addressed by leading scientists. The presentation on mitigation of carbon dioxide emissions was made by the Head of the Energy Technology Support Unit (ETSU), Ken Currie, and identified the key potential options for mitigation by 2020. In this paper, we compare the mitigation potential identified for each proposed option with the 2019 outturn. The largest mitigation options identified were improved end use energy efficiency across the economy and the generation and use of low carbon electricity. Our analysis finds that these have been the key options adopted. Reductions in primary energy use, resulting from improvements in energy efficiency were concentrated in the period 2005-2012 which in 1989 were widely considered to be ambitious. Decarbonisation of electricity has been achieved by the displacement of coal, initially by gas and more recently by renewable electricity. Renewable electricity has exceeded 1989 expectations in the last 5 years and is now the biggest source of CO2 reductions from electricity generation. The contribution envisaged by nuclear electricity has not occurred, largely due its failure to compete in liberalised generation markets. In all cases, the policy environment has been important. We draw lessons for mitigation options to achieve the goal of net zero emissions in the next 30 years. The contribution of demand side and other modular options will remain crucial, as mass-produced technologies tend to improve more quickly than those requiring large construction projects. Environmental, social and political factors will be important, so analysis should not be a purely techno-economic assessment.