Sustainability of the four generations of biofuels – A review

Biomass-derived aviation fuels: Challenges and perspective

The present investigation provides an overview of the current technology related to the green diesel, from the classification and chemistry of the available biomass feedstocks to the possible production technologies and up to the final fuel properties and their effect in modern compression ignition internal combustion engines. Various biomass feedstocks are reviewed paying attention to their specific impact on the production of green diesel. Then, the most prominent production technologies are presented such as the hydro-processing of triglycerides, the upgrading of sugars and starches into C15–C18 saturated hydrocarbons, the upgrading of bio-oil derived by the pyrolysis of lignocellulosic materials and the “Biomass-to-Liquid” (BTL) technology which combines the production of syngas (H2 and CO) from the gasification of biomass with the production of synthetic green diesel through the Fischer-Tropsch process. For each of these technologies the involved chemistry is discussed and the necessary operation conditions for the maximum production yield and the best possible fuel properties are reviewed. Also, the relevant research for appropriate catalysts and catalyst supports is briefly presented. The fuel properties of green diesel are then discussed in comparison to the European and US Standards, to petroleum diesel and Fatty Acid Methyl Esters (FAME) and, finally their effect on the compression ignition engines are analyzed. The analysis concludes that green diesel is an excellent fuel for combustion engines with remarkable properties and significantly lower emissions.

https://www.mdpi.com/1996-1073/12/5/809/pdf

Green Diesel: Biomass Feedstocks, Production Technologies, Catalytic Research, Fuel Properties and Performance in Compression Ignition Internal Combustion Engines

The undeniable environmental ramifications of continued dependence on oil-derived jet fuel have spurred international efforts in the aviation sector towards alternative solutions. Due to the limited options for decarbonisation, the successful implementation of bio-aviation fuel is crucial in contributing to the roster of greenhouse gas emissions mitigation strategies for the aviation sector. Since fleet replacement with low-carbon technologies may not be a feasible option, due to the long lifetime and significant capital cost of aircraft, ‘drop-in’ alternatives, which can be used in the engines of existing aircraft in a seamless transition, may be required. This paper presents a detailed analysis of the supply chain components of bio-aviation fuel provision: feedstocks, production pathways, storage, and transport. The economic and environmental performance of different potential bio-feedstocks and technologies are investigated and compared in order to make recommendations on short- and long-term strategies that could be employed internationally. Hydroprocessed esters and fatty acids production pathway, utilising second-generation oil-seed crops and waste oils, could be an effective immediate solution with the potential for substantial greenhouse gas emissions savings. Microalgal oil could potentially offer far greater yields of bio-aviation fuel and reductions in greenhouse gas emissions, but the technology for large-scale algae cultivation is inadequately mature at present. Fischer-Tropsch production pathway using lignocellulosic biomass has the potential for the highest greenhouse gas emissions savings, which could potentially be the solution within the medium- to long-term plans of the aviation industry, but further research and optimisation are required prior to its large-scale implementation due to its limited technological maturity and high capital costs. In practice, the ‘ideal’ feedstocks and technologies of the supply chains are heavily dependent on spatial and temporal criteria. Moreover, many of the parameters investigated are interlinked to each other and the measures that are effective in greenhouse gases emissions reduction are largely associated with increased cost. Hence, policies must be streamlined across the supply chain components that could help in the cost-effective and sustainable deployment of bio-aviation fuel.

/pdf/bio-aviation-fuel-a-comprehensive-review-and-analysis-of-the-3c8r1ql1sy.pdf

Bio-aviation Fuel: A Comprehensive Review and Analysis of the Supply Chain Components

The recent pandemic caused by COVID-19 has globally affected air transport mobility as well as the airline industry in general. Numerous restrictions have been implemented in airline transport, which is potentially leading toward severe long-term impacts on the global airline industry. In this paper, air transport mobility was analyzed regarding Europe (EU) based on the available data from the relevant sources associated with the airline industry. Data were analyzed in specific periods from January to April of 2020, which corresponded with the initialization of the pandemic in the EU and later in its full development. Specifically, two airports were selected in Croatia as case studies to analyze the impact of COVID-19 more thoroughly on mobility together with the estimation of carbon footprint during the pandemic and the year before the pandemic state. The results revealed that COVID-19 gradually affected air transport mobility in the EU where a peak was reached in April with a reduction in the number of flights in the EU region reaching more than 89%. Cargo traffic was not significantly affected by the pandemic, and was even increased in some cases due to the supply of medical equipment in the fight against the disease. The analyzed case study revealed the reduction in air transport mobility for selected airports to be more than 96%, which directly affected the reduction of CO2emissions to factor 1.81 for the commercial airport of Zagreb and 3.49 for the seasonal airport of Split. A normalization of air transport mobility is expected to be reached through a 1-year period with a continued reduction in the number of flights ranging from 15% to 25%, based on the projections and expectations from relevant EU associations.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/er.5706

Impact of coronavirus (COVID-19) pandemic on air transport mobility, energy, and environment: A case study

This article presents results of a European Commission Joint Research Centre study to analyse the Greenhouse Gas (GHG) emissions and energy efficiency of various options for alternative aviation fuels. Interest in alternative aviation fuels is growing, as the sector seeks viable options to reduce increasing GHG emissions. For biofuels non-biogenic emissions arise from cultivation, harvesting and transport of the feedstock, as well as from their conversion into biofuel. It is important to consider whether any emissions reductions benefits are justified by the energy efficiency of each alternative. This article is focussed on American Society for Testing and Materials (ASTM) certifiable alternative drop-in biojet fuels [1] , i.e. non-fossil hydrocarbon fuels which have (i) the same chemical structure and (ii) can be blended with conventional jet fuels, (iii) can use the same jet fuel supply infrastructure, and (iv) do not require modification of the aircraft. The results indicate that the biofuels studied tended to exhibit lower GHG than conventional jet fuels although indirect effects or existing uses of materials were not included in this study. Some biofuels performed better at reducing GHG than others (for example biofuels from wastes and residues). A large and important effect on emissions is seen due to land type used for cultivation and whether methane capture is used for certain pathways. GHG savings results vary due to the Life Cycle Analysis (LCA) methodology chosen for dealing with emissions and co-products. Certain pathways are notably more energy intensive than others and strong GHG reduction does not always coincide with high energy efficiency. An overview of industry initiatives and critical EU legislation relating to aviation biofuels is given. The insights from this work are expected to be of use for decision-makers considering investment options in this sector.

Considerations on GHG emissions and energy balances of promising aviation biofuel pathways

The use of biofuels in transport is being promoted as a means of tackling climate change, diversifying energy sources and securing energy supply. Biofuels production also provides new options for using agricultural crops. However, it also gives rise to environmental, social and economic concerns which are the subject of intense debate worldwide. This study provides a detailed overview of biofuels production and consumption and of related policies worldwide. It also contains comprehensive analysis and discussion of key aspects affecting the overall sustainability of biofuels. These include, in particular, their impact on agricultural markets, emissions from indirect land-use change, and greenhouse gas emissions

The impact of biofuels on transport and the environment, and their connection with agricultural development in Europe

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Considerations on GHG emissions and energy balances of promising aviation biofuel pathways

The impact of biofuels on transport and the environment, and their connection with agricultural development in Europe