ABSTRACT
Biofuels are good examples of modern biomass due to their conversion efficiency and their potential positive results related with sustainability. The biofuels analyzed in this text include liquid fuels used in road transport, biomethane (also used in transport sector), jet biofuels, and wood pellets; an overview of recent developments and an assessment of future trends are presented for each of them. Among these biofuels, the current largest contributions are from liquid biofuels (about 135 × 109 L consumed in 2015, 66% as ethanol, energy basis) and wood pellets (28 million tonnes consumed in 2015). Biomethane has been consumed in the transport sector in few countries, in specific cases, and jet biofuels are a promising alternative for reducing greenhouse gas (GHG) emissions in civil aviation. The role of bioenergy in the future energy matrix will depend on meeting sustainability requirements and, among them, its contribution to reducing GHG emissions needs to be both significant and cost-effective. Alternatives such as biomethane and pellets do not require substantial technological breakthroughs, but for reaching the commercial stage of second-generation biofuels and jet biofuels production, there are still significant research and development challenges. The difficulties are even larger for second-generation biofuels to be consumed in road transport because the market has been constrained due to the aversion to first-generation ones (produced from sugars, starches, and vegetable oils) and also due to the understanding that electric vehicles could be a superior solution for reducing emissions in the road transport sector. However, it is estimated that electric vehicles will not represent more than 25% of the world fleet of light-duty vehicles in 2040 and, thus, other options are required for reducing GHG emissions. Why not, sustainable liquid biofuels?
