Transport fuel supply today, in particular to the road sector, is dominated by oil, which has proven reserves that are expected to last around 40 years. The combustion of mineral oil derived fuels gives rise to CO2 emissions and, despite the fact the fuel efficiency of new vehicles has been improving, so that these emit significantly less CO2 , total CO2 emissions from transport have increased by 24% from 1990 to 2008, representing 19.5% of total European Union (EU) greenhouse gas emissions.
The EU objective is an overall reduction of CO2 emissions of 80-95% by the year 2050, with respect to the 1990 level. Decarbonisation of transport and the substitution of oil as transport fuel therefore have both the same time horizon of 2050. Improvement of transport efficiency and management of transport volumes are necessary to support the reduction of CO2 emissions while fossil fuels still dominate, and to enable finite renewable resources to meet the full energy demand from transport in the long term.
Alternative fuel options for substituting oil as energy source for propulsion in transport are:
1.-Electricity/hydrogen, and biofuels (liquids) as the main options.
- Electricity and hydrogen are universal energy carriers and can be produced from all primary energy sources. Both pathways can in principle be made CO2 free; the CO2 intensity depends on the energy mix for electricity and hydrogen production. Propulsion uses electric motors. The energy can be supplied via three main pathways:
- Battery-electric (with electricity from the grid stored on board vehicles in batteries) Power transfer between the grid and vehicles requires new infrastructure and power management
- Fuel cells powered by hydrogen, used for on-board electricity production. Hydrogen production, distribution and storage require new infrastructure.
- Overhead Line / Third Rail for tram, metro, trains, and trolley-buses, with electricity taken directly from the grid without the need of intermediate storage.
- Biofuels could technically substitute oil in all transport modes, with existing power train technologies and existing re-fuelling infrastructures. Use of biomass resources can also decarbonise synthetic fuels, methane and LPG. First generation biofuels are based on traditional crops, animal fats, used cooking oils. They include FAME biodiesel, bioethanol, and biomethane.
2.-Synthetic fuels, as a technology bridge from fossil to biomass based fuels, substituting diesel and jet fuel, can be produced from different feedstock, converting biomass to liquid (BTL), coal to liquid (CTL) or gas to liquid (GTL). Hydrotreated vegetable oils (HVO), of a similar paraffinic nature, can be produced by hydrotreating plant oils and animal fats. Synthetic fuels can be distributed, stored and used with existing infrastructure and existing internal combustion engines.
3.-Methane (natural gas and biomethane) as complementary fuels. Methane can be sourced from fossil natural gas or from biomass and wastes as biomethane. Biomethane should preferentially be fed into the general gas grid. Methane powered vehicles should then be fed from a single grid. Additional refuelling infrastructure has to be built up to ensure widespread supply.
4.-Liquefied Petroleum Gas (LPG) as supplement. LPG is a by-product of the hydrocarbon fuel chain, currently resulting from oil and natural gas, in future possibly also from biomass. LPG is currently the most widely used alternative fuel in Europe, accounting for 3% of the fuel for cars and powering 5 million cars.
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