BC Explains: biofuels
13 April 2018
Author: Rachel Boagey
In the first of a series of BC explainer features, Rachel Boagey takes a look at what biofuels actually are, what they're made from and if they're a viable fuel type going forward in the industry.
In the late noughties, biofuels commanded a high proportion of airtime. They were an ideal, low-carbon replacement for the decreasing stockpiles of conventional fossil fuels.
However, anxieties grew that first- generation biofuels - usually developed from food crops - increased food prices and were often as polluting as fossil fuels, when considering all production factors.
Reinforcing this sentiment, in 2016, a Royal Academy of Engineering report stated that some biofuels, such as diesel made from food crops, led to more emissions than those produced by fossil fuels. The report also suggested that increased biofuel production should make more use of waste, such as used cooking oil and timber.
However, with a UK government push to further lower CO2 and NOX pollutants from vehicles, electrification appears to be the answer. Unfortunately, it can't be the 'here and now' due to various obstacles such as range and infrastructure, which are far from being solved.
In this case, could biofuels begin to make more sense in the industry as a stepping stone?
What is a biofuel?
The term 'biofuel' has come to mean two things in the UK: a mix of fossil fuel and biofuel, for example a 5% blend biodiesel with 95% normal diesel ;or 100% pure biofuel, which is known as a biodiesel.
This dual meaning can be misleading, says Anthony Machin, biofuels expert and head of content at the intelligence company Glass's.
"The availability of 4.75% biodiesel is common, as the government's Road Transport Fuel Obligation (RTFO) requires that the UK have 4.75% of biofuels across the nation," he says. "As the RTFO secures a 4.75% blend by law, blends higher than 5% would be a way of looking to the future."
Under the RTFO order, the biofuel blend sold in the UK is blended into petrol and diesel at a rate of 4.75%. A rise towards the 10% EU-wide target by 2020 has stalled, due to the
The main environmental advantage of a biofuel is that it is carbon neutral, with all the carbon dioxide emitted during use of the fuel being balanced by the absorption from the atmosphere during the fuel crop's growth. "Biodiesel does not add any carbon because it utilises the amount of carbon that naturally circulates between the atmosphere and the biosphere known as photosynthesis," says Machin.
However, there are an overwhelming number of studies showing the use of neat biodiesel and biodiesel blends slightly increases the generation of nitric oxide and nitrogen dioxide. Any combination of which constitutes oxides of nitrogen (NOX). Without dwelling on technicalities, research suggests NOX increases can range anywhere from less than 1 to 15% higher than conventional fossil diesel.
"For cars, as a stepping stone before electric, there are some advantages to biofuels, namely the carbon neutrality; however, the potential increases in NOX could outweigh the advantages shown," says Machin. "In the goods vehicle sectors, biofuel could still have a use for a long time to come where battery technology versus payload versus range are questions still without answers."
In practice, the process of growing the crop requires the input of fossil fuels for fertilisers, harvesting, processing and fuel distribution, but ultimately, biofuels limit pollutant emissions since they contain no lead and only a small amount of sulphur. They also have a high oxygen content so mi them with conventional fuels does improve combustion and thus reduces emissions of particulates, carbon monoxide and other pollutants.
For example, a 5% biofuel blend would result in a carbon reduction of around 2.5% (biodiesel) and 4% (bioethanol). Much greater emission reductions are possible for biodiesels if waste oils are used, as the source material would otherwise be
First-generation biofuel blends follow EU legislation on a volume basis, and the blended biofuel must fulfil a rigorous set of standards to avoid damaging the engine and the fuel system in which it is used. Now in their second generation, there are numerous types of biofuels and various countries around the world are all using different types of biofuels. For example, for decades, Brazil has turned sugarcane into ethanol, and some cars there can run on pure ethanol rather than as an additive to fossil fuels.
Second-generation biofuels, which are also known as advanced biofuels, are 'greener', in that they are made from sustainable base materials such as various different types of biomass. They can supply a larger proportion of global demand sustainably, affordably, and with greater environmental benefits. In addition, because biofuels come from virgin plant material, they are renewable. Unfortunately though, most second-generation fuels are under development and not widely available for use. The list includes:
- Cellulosic ethanol: usually made from wood, grass, or inedible parts of plants.
- Algae-based biofuels: multiple different fuels made from algae including jet fuel. More expensive, but may yield ten to 100 times more fuel per unit area than other biofuels
- Biohydrogen: made from algae breaking down water. Used in place of the hydrogen produced from fossil fuels.
- Methanol: inedible plant matter.More toxic and less energy dense than ethanol.
- Dimethylfuran: Made from fructose found in fruits and some vegetables. It has an energy density that is close to that of gasoline. It's toxic to the respiratory tract and nervous system.
- Fischer-Tropsch biodiesel: Waste from paper and pulp manufacturing. Process is chemical reaction, making hydrocarbon from carbon monoxide and hydrogen.
Yet, there are a couple of environmental hiccups in this otherwise positive picture. Online comparison tools such as Biodiesel Filling Stations offer a list of UK outlets for all higher-percentage blends and shows that there there are almost no bioethanol stations in the UK since the supermarket chain Morrisons stopped supplying E85 in 2010.
"As a marketing ploy and a way of reducing its environmental impact, McDonald's continues to reduce, reuse and recycle in their restaurants and across their whole business," says Machin. One method they have found is to recycle their used cooking oil into biodiesel used to fuel more than half of their delivery trucks, effectively using the cooking oil twice.
Citroen is a manufacturer that markets powertrains designed to run on biofuels; biodiesel for HDi diesel engines and bioethanol for petrol engines. It has developed petrol engines able to use fuel containing up to 10% ethanol (E10 fuel). The use of E10 fuel cuts CO2 'well-to-wheel' emissions by around 6%.
In some markets, such as Brazil and Sweden, Citroen also sells vehicles using 'FlexFuel' technology, which can run on fuel containing up to 85% ethanol.
Audi is entering a renewed collaboration agreement with French Global Bioenergies to further broaden the flexibility of its biofuels technology for greener cars.
"For cars, as a stepping stone before electric, there are some advantages to biofuels, namely the carbon neutrality."
In the future, second-generation biofuels are likely to be made available. These could use the whole plant as well as biomass and seaweed, which are still at research stages. Many manufacturers, such as Citroen, are trying to ensure their engines are compatible with these fuels as soon as they reach the industrial production stage, by around 2020-30.
If fossil fuels are to be phased out, the cheapest and fastest alternative to get to market will win. Of all the renewable fuels, biofuels are the most commercially ready.
Electric cars come a close second, with many car makers already selling them, though the ones already on sale are a tad on the expensive side and the infrastructure is still not in place for every car to be electric. Of course, hybrid cars can run off a combination of biofuels and renewable electricity, also currently bridging the gap between combustion and electric engines, but their high price, and lack of infrastructure are still large factors affecting their success.
Therefore, it's likely that until the government's 2040 ban on petrol and diesel vehicles, the prioritisation of the right kinds of biofuels through subsidies and caps will occur, and the industry should be able to minimise their drawbacks and maximise their advantages over petroleum fuels. While the ban may mean the end of biofuels, should be seen as an important opportunity for their continued development and their place in further reducing CO2 and NOX emissions until electric cars are ready to take their place.