Contribution of Sustainable Fuels for the Future of the Energy Sector

Introduction

The negative impact of anthropogenic CO2 emissions has been established beyond any doubt. It is now clear that the energy consumption patterns of humanity will have to change very quickly and on a global scale if the worst effects of climate change are to be avoided.

The still growing energy demand, driven by the expansion of consumer societies, has been mostly satisfied by fossil sources, such as coal, oil, and natural gas. Fossil fuels are used intensively since the dawn of the industrial era and are the main sources of anthropogenic CO2 emissions, which has led to a search for suitable renewable energy alternatives. It is important to stress that there are other forces behind the drive for renewable energy besides climate change, such as geopolitical tensions, scarcity of resources or citizens awareness. Also, the search for renewable energy sources and technologies is not the sole area of activity in the fight against climate change. Ecosystem preservation, sustainable agricultural practices, or waste valorization to comply with circular economy objectives, are just a few examples.

The energy policy of countries in general, including Portugal, is based on security of energy supply, sustainability, and competitiveness. Thus, to produce renewable energy all those factors must be considered. Renewable energy, besides its environmental advantages, works towards a diversification of primary resources, the constitution of strategic reserves and the decreased of dependence on imports (Gulbenkian, 2022).

In 2015, the Paris Agreement (PA) defined that paradigm changes in society are necessary to contain the effects of climate change. The main goal of the Paris Agreement is to limit global warming to 2 or preferably to 1.5 degrees Celsius, compared to pre-industrial levels. The European Union (EU) and all its member states have signed and ratified the Paris Agreement and are committed to its implementation through some strategies as the reduction the greenhouse emissions. Thus, EU countries have agreed to set the EU on the path to becoming climate-neutral economy and society by 2050, through the decarbonization of the energy sector (UNFCCC- United Nation Climate Change, 2022).

The path for a carbon neutral economy is based on the electrification of energy use (with electricity increasingly coming from renewable energy sources) and the use of sustainable fuels in those sectors that are not prone to electrification (such as aviation or some branches of industry).

Finding suitable substitutes of fossil fuels that can be used in existing infrastructure and equipment and are free of CO2 emissions is the main aim of the search for sustainable renewable alternative fuels. Sustainable fuels will be a central factor for the decarbonization of the energy sector and compliance with the objectives of the Paris Agreement. They can simultaneously be used for power generation and as an energy carrier where the utilization of new technologies and energy sources is required and will have a more important role in the future as they are likely to be utilized on a greater scale (UNFCCC- United Nation Climate Change, 2022). The need for new types of fuels to substitute fossil fuels is particularly important in the aviation sector due to the greater difficulty of electrification of the sector. Currently there are a variety of alternative fuels the mostly used are Green Hydrogen, Ammonia, biodiesel, bioethanol, synthetic fuels (Stancin, Mikuleié, Wang, & Duié, 2020).

It is necessary to clarify the distinction between renewable, sustainable, and alternative fuel. In accordance with European Commission, renewable fuels are fuels produced from renewable energy sources. Renewable energy sources are non-fossil sources that are naturally replenished on a human timescale (wind, solar, geothermal, wave, tidal, hydropower, biomass). A fuel can be defined as renewable only when it is based on renewable sources. To be sustainable, a renewable fuel should not increase the concentration of CO2 in the atmosphere (Al-Breiki & Bicer, 2021) as well as other pollutants (European Commission, 2019b). Sustainable fuels are produced from renewable and/or alternative feedstocks, such as plant and vegetable waste, which are sustainably sourced. Alternative or non-conventional fuels are fuels such as electricity, hydrogen, biofuels, natural gas, synthetic fuels, ammonia, with the potential for long-term replacement of petroleum fuels regardless of the energy and feedstock used and possible fuel combinations. (Directives, 2014)