1.1 Scope of the analysis and background of renewable solutions
This report examines the role of renewable solutions for road transport that are commercially available today, or that are likely to be commercialised by 2020 at reasonable cost. The analysis therefore focuses on conventional and advanced liquid biofuels, biomethane and electrifi-cation of transport using renewable power generation.
Liquid biofuels are not new. Their use goes back to the earliest era of the use of internal combustion engines in the 19th century, and Brazil has had significant shares of ethanol use for decades. However, the growth in biofu-els production over the last 13 years has been driven by government policies. These aim to improve energy security and the diversity of fuel supplies, reduce oil and/ or refined product imports, promote rural economic and social development and reduce greenhouse gas (GHG) emissions. This policy support began in Organisation for Economic Co-operation and Development (OECD) countries, but more and more developing countries have already enacted support policies or are developing them.
Biofuels can be split into two broad categories: conventional biofuels derived from food or animal feed crops2 and advanced biofuels which use lignocellulosic feedstocks (Figure 1.1 and Figure 1.2). Since this report examines conventional and advanced biofuels that have already been commercialised or will be before 2020 at a reasonable cost, the analysis does not examine bio-hydrogen (via gasification and reforming or electrolysis using electricity from solar or wind) or biofuels from algae, which are at an earlier stage of research, development and demonstration (Figure 1.2).
Figure 1.1: Biofuel pathways from feedstock to products
Source: Based on Schwaiger, 2011.
1. Biomass-to-liquids; 2. Fischer-Tropsch; 3. Dimethylether; 4. Bio-synthetic gas.
Figure 1.2: Maturity of different biofuel pathways
Source: Based on IEA, 2011.
Conventional bioethanol and biodiesel, also referred to as first-generation liquid biofuels, are produced from mature processes at commercial scales. For bioethanol, the process comprises the conversion of sugar or starch derived from cereals/grains, sugarcane, sugarbeet, cassava, and others, via fermentation into alcohol and subsequent distillation to ethanol. For biodiesel, the feedstocks used include vegetable oil derived from oil palm, soybeans, rapeseed, Jatropha seeds and others, as well as waste cooking oil, animal fats and other sources of vegetable and animal fats and oils. The feedstock can either be converted into Fatty-Acid Methyl Ester (FAME), via transesterification of the raw material, or processed via hydrotreatment into a biodiesel with properties close to that of fossil diesel. Conventional biofuels also include methanol and butanol produced from starch or sugar through similar processes, and biomethane production from anaerobic digestion.
Advanced bioethanol and biodiesel, also referred to as second-generation biofuels, are produced using conversion technologies that are only just being commercialised or are still in the research and development (R&D), pilot or demonstration phase. This category includes bioethanol produced from the biochemical conversion of lignocellulosic feedstock such as wood, straw, bagasse and similar materials of biological origin into sugars followed by the fermentation into alcohol and distillation into ethanol. Methanol and butanol produced via similar processes are also included in this category, as well as any gasoline-type biofuels produced via thermo chemical conversion of biomass (i.e. gasification followed by a fuel synthesis), or through processes using micro-organisms such as algae and bacteria.
Advanced biodiesel includes synthetic diesel or kerosene-type fuels derived via gasification and subsequent catalytic fuel synthesis or via pyrolysis and subsequent upgrading/refining. Also included in this category are algae-based fuels and diesel-type biofuels produced from sugar using microorganisms.
Virtually all biofuels produced today are conventional, whereas advanced biofuel production is entering the early phase of commercial deployment. A range of commercial-scale plants are online or coming online in the next three years (Bacovsky, 2013 and Brown and Brown, 2013).
Biofuels derived from food crops have net benefits in terms of emissions reductions and energy balance.3 However, they are extremely sensitive to food price movements and there is little opportunity for cost reduction, as the technology is relatively mature; only incremental improvements in process economics can be expected. Looking further into the future, the reliance on food crops will limit the potential contribution of these types of biofuels to total transport demand.
Advanced biofuels are still expensive today and only just being commercialised. However, they offer the potential for significantly lower and more stable feedstock costs and could meet a much larger proportion of transport demand, given that feedstocks can be sourced from a wide range of biomass sources. This is because advanced biofuels use lignocellulosic feedstocks from wastes/residues or from energy crops that do not have to be grown on pasture or arable land. The challenge is still to prove the efficiency, reliability and commercial attractiveness of the different pathways for advanced biofuels.
Biogas is composed mostly of methane and carbon dioxide produced from organic material. It can be upgraded and purified to become biomethane for use as a transport fuel in internal combustion engine (ICE) powered vehicles. It is compressed, to improve the energy density, and used in a dedicated biomethane vehicle or dual-fuel vehicle.
The key challenges for biogas are that to be used as a transport fuel, it requires natural gas or biomethane-based fuelling infrastructure and flex-fuel or dedicated natural/biomethane vehicles. Alternatively, existing vehicles can be converted to run on biogas, but at a cost and with a loss in storage space and range to accommodate the storage tank.
The two most promising routes for the production of bi-ogas for transportation are anaerobic digestion (AD) of organic matter and the gasification of woody biomass to produce synthetic biogas. AD is commercially mature and is already used around the world to produce biogas from organic wastes (e.g. refuse, sewage and other ef-fluents) and this is the option examined in this paper.
The use of electricity from renewable sources as an energy source for vehicles, either in PHEVs or EVs, is an important option to decarbonise the transport sector.4 It also has significant co-benefits in terms of reducing local pollutant emissions and reducing the negative health impacts of local pollutant emissions from internal combustion engine powered vehicles.
The key challenge is to improve the performance of the batteries used in PHEVs and EVs to provide greater range than today at lower costs. PHEVs combine an often downsized ICE with the capability for all-electric driving in charge depleting mode from a battery recharged from the grid. Depending on battery size and driving patterns, PHEVs can cover a majority of vehicle kilometres on electricity alone. Meanwhile, the retention of an ICE means that the total range of the vehicle on electricity and liquid fuels is comparable to today's ICE vehicles.
With EVs, the ICE is dispensed with and electricity from the battery provides all of the energy required for driving through one or more electric motors. The EVs battery is recharged from an electricity source (grid-connected or off-grid), from regenerative braking and potentially from integrated PV panels. The main advantages of EVs are that:
- they have zero local pollutant emissions;
- they are much quieter than a vehicle with an internal combustion engine (ICE); and
- their electric motors are much more efficient than an ICE and cheaper as well.
These advantages have to be offset by the early stage of vehicle battery technology development, with their low energy and power densities compared to liquid fuels, and relatively high costs. However, cost reduction potentials are good given that commercialisation of mass-produced PHEVs and EVs is only just beginning. An advantage of the electrification route is that the basic technology components are relatively mature, with the exception of batteries, while the existing experience with batteries from consumer products means that there are a range of potential battery suppliers and significant investment in innovation and R&D to develop battery technologies optimised for PHEVs and EVs.
2 For simplicity, biofuels produced from the wastes of the food or animal feed component of the crops are included in this category (e.g. used vegetable oil, yellow grease, etc). The reason for this is that their supply is essentially limited to the food and animal feed crop.
3 The Global Bio-Energy Partnership (GBEP) has extensive analysis and recommendations of the sustainability issues surrounding biofuels.
4 Hybrid electric vehicles (HEV) combine a battery with an electric motor and an ICE. However, there is no external electricity source, as the battery is charged from the ICE or with regenerative breaking. These are therefore not in the scope of this report.