Issue: Jun 2011

The design of biofuels for the automotive industry

by Tony Davidson

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Visit our Download Center for more articles, whitepapers and interviews: design and development of biofuels for the automotive industry presents a variety of questions that must be answered in a collaborative process between the automotive industry, the petroleum industry, and policy makers on a global scale. The EU Renewable Energy Directive (RED) has targeted a biofuel content of transport fuels of 10% by 2020. With the majority of European states failing to reach the 2010 target of 5.75%, this raises several considerations in terms of the processes required to deliver the integration of biofuels into the overall fuel mix.

The infrastructure of supply and distribution must be in place to support biofuels, and research into fuels which can ‘drop in’ to existing supply lines needs significant development. The overall energy efficiency of biofuels must be assessed on an industrial scale. Currently there are demonstration projects in place for most second generation biofuels, although many of the processes of manufacture are at laboratory stage, and the fuels cannot be considered economically or environmentally viable until the whole production process is streamlined for cost and energy efficiency. The greenhouse gas overhead of the entire production process must also be considered; many first generation biofuels reduce carbon emissions far less than first thought due to the release of carbon gases during production.

It is also a problem of political and social consideration, due to the sheer volume of biomass that must be produced in order to manufacture enough biofuel to satisfy demand. Energy crops cannot be allowed to become competitive with food over the use of agricultural land, particularly in developing countries. Policy makers must also look at the fiscal benefits and rewards for the petroleum industry and the automotive industry to facilitate the introduction of biofuels.

The automotive industry has developed several prototypes and some commercially available vehicles designed specifically for use with biofuels, which represents a positive outlook for the future; but there is also a need to develop fuels that can integrate into existing infrastructures and be used in existing vehicles. To this end there is still a requirement to facilitate industrial scale production and supply of first generation biofuels in the mid-term.

Biofuels and practical uses

European heavy duty engine manufacturers permit a maximum 5% blend of biodiesel with mineral diesel, in line with EN590 mineral diesel specification, to maintain warranty on their engines. In Germany, however, biodiesel is made from pure oil seed rape to conform to the European standard EN14214, and it is used commercially as a B100 mix. Scania and DAF are two vehicle manufacturers who have approved the use of 100% RME biodiesel in new engines, which have more tolerant components. Other manufacturers such as Renault are more conservative, only approving a B30 mix at this stage on certain new models.

In terms of engine performance, biodiesel reduces emissions and can improve lubrication and reduce engine wear. It has a higher cetane index than mineral diesel, giving it better ignition and combustion properties and reducing ‘engine knock’ characteristics.

Bio ethanol
Bio ethanol can be used in a mix with petrol, and older spark-ignition engines can tolerate a 5% blend of ethanol with petrol. Newer cars can accept a 10% blend (E10), while flexible fuel vehicles first developed in Sweden are now commercially available and can run on E85; an 85% ethanol and 15% petrol mix. Fuel consumption is considered to be worse than conventional fuel by a factor of 1.5 for pure ethanol, 1.4 for E85. Ford, Saab and Volvo are three manufacturers supporting the use of bio ethanol as a transport fuel, by manufacturing FFVs that can run on E85. Saab’s 9-5 Bio power model

Sustainability may prove to be the biggest obstacle of using bio ethanol on an industrial scale. It is generally derived from crops like sugar cane and corn, and there are concerns over biodiversity and carbon neutrality due the amount of land that would need to be redeveloped for crop growth.

Biobutanol is subject to more and more research and development as a viable alternative to bio ethanol. It has several properties that give it and advantage over other existing biofuels. It can be created from raw cellulose biomass as well as food-based feedstocks, which means it has the potential to be more viable on an industrial scale. It has a low water affinity, so can be used with existing pipelines and infrastructure. Biobutanol can be mixed at 85% with mineral petrol, without the need to modify engines, and has 25% higher energy content than bio ethanol. Butanol has a higher flashpoint and a lower vapour pressure than ethanol, so is much easier to store and safer to handle. While ethanol needs to be blended with petrol shortly before being used, butanol can be blended at a refinery and utilise the same supply lines and retail pumps already in use. Several demonstration plants are in operation to develop the technology to mass produce biobutanol for use as a transport fuel. It is expected to be commercially available by 2013.

Biogas produced by anaerobic digestion of landfill waste, agricultural and manure waste, and food waste presents a viable and sustainable feedstock. The UK produces 30 million dry tonnes of such waste per year, which could produce 6.3 million tonnes of oil equivalent of methane gas. This volume could potentially supply 16% of transport fuel demand, but there are several problems surrounding the use of biogas. It can only be used with specially designed vehicles, or those that were originally designed to run on natural gas. Although more economical than diesel by 40% and petrol by 55%, the initial capital outlay for vehicles and the lack of refuelling stations present logistical problems for practical use. Dual fuel vehicles such as Volkswagen’s bi-fuel Golf have two separate fuel systems, with a back up petrol system should the gas supply run out. In use for several years, these bi-fuel vehicles are the only solution in the interim until natural gas, and therefore biogas, becomes widely available. 

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