Selection of Blends of Diesel Fuel and Advanced Biofuels Based on Their Physical and Thermochemical Properties

Abstract

Current policies focus on encouraging the use of renewable energy sources in transport to reduce the contribution of this sector to global warming and air pollution. In the short-term, attention is focused on developing renewable fuels. Among them, the so-called advanced biofuels, including non-crop and waste-based biofuels, possess important benefits such as higher greenhouse gas (GHG) emission savings and the capacity not to compete with food markets. Recently, European institutions have agreed on specific targets for the new Renewable Energy Directive (2018/2001), including 14% of renewable energy in rail and road transport by 2030. To achieve this, advanced biofuels will be double-counted, and their contribution must be at least 3.5% in 2030 (with a phase-in calendar from 2020). In this work, the fuel properties of blends of regular diesel fuel with four advanced biofuels derived from different sources and production processes are examined. These biofuels are (1) biobutanol produced by microbial ABE fermentation from renewable material, (2) HVO (hydrotreated vegetable oil) derived from hydrogenation of non-edible oils, (3) biodiesel from waste free fatty acids originated in the oil refining industry, and (4) a novel biofuel that combines fatty acid methyl esters (FAME) and glycerol formal esters (FAGE), which contributes to a decrease in the excess of glycerol from current biodiesel plants. Blending ratios include 5, 10, 15, and 20% (% vol.) of biofuel, covering the range expected for biofuels in future years. Pure fuels and some higher ratios are considered as well to complete and discuss the tendencies. In the case of biodiesel and FAME/FAGE blends in diesel, ratios up to 20% meet all requirements set in current fuel quality standards. Larger blending ratios are possible for HVO blends if HVO is additivated to lubricity improvers. For biobutanol blends, the recommended blending ratio is limited to 10% or lower to avoid high water content and low cetane number.