Bioalcohols: the Future of Fuel?

The use of biofuels has been kick-started by the launch of a UK-based plant, set to trigger larger future operations. Annabel Hardy investigates how these crop-based fuels could offer a revelatory new, low-emission future for renewables.


In September 2007, Britain's first-ever bioethanol plant at Wissendon, East England, welcomed the first tanker that would carry the first of what is predicted to be 55,000t of bioethanol a year from the British Sugar plant.

It was an event that, while producing only a small amount of fuel, had a great number of observers. British Sugar is merely warming the seat for a much larger project in conjunction with BP and DuPont that is due to commence operation in the UK's city of Hull in 2009.

This is not to say that work will not begin sooner. With the European Commission recently granting regulatory clearance for a new US$400m BP/British Sugar/DuPont bioethanol plant, work is about to get under way. Contracts for equipment and machinery will be finalised and construction on the plant is due to begin early in 2008, with commissioning and start-up planned for late 2009.

The plant has a planned commercial capacity of 420 million litres of bioethanol a year from wheat feedstock, which could be converted to biobutanol as the technology develops. Front-end engineering and design work (FEED) is being carried out by global engineering and construction company Aker Kvaerner, with joint venture partner, Praj Industries from India providing the technology, process package and key equipment. Both companies completed a feasibility study for the complex in December 2006.

The facility is being built from scratch, alongside BP's existing chemicals site at Saltend, although engineers will have access to the existing infrastructure. Local grain-trading business Frontier Agriculture and marketing company AB Agri are also expected to enter into definitive agreements with the joint venture facility to source feedstock and sell the byproducts of the process.

COMMERCIALISATION OF BIOBUTANOL

Biobutanol is produced through the fermentation of starch and sugars by Clostridium bacteria, a process that enabled the production of acetone for munitions during the First World War. The alcohol bioethanol has been used as a petrol additive to increase octane ratings for nearly a century, most notably in Second World War Japanese fighter planes.

It has, however, been uneconomical to produce biobutanol at the same low prices as oil, which is why it has not previously been commercialised in large-scale biofuel applications. Today it accounts for less than 2% of transportation fuels. Nevertheless, under the EU directive, it is expected that these will be at least 5.75% biofuel by 2010 and 10% in 2020.

Most of the biofuel used in gasoline today is represented by ethanol, though biobutanol is being developed by BP and DuPont as it has several advantages:

  • It does not increase vapour pressure when added to gasoline, meaning that special gasoline base blends are required to prevent an increase in emissions of volatile organic compounds (VOCs).
  • Its tolerance to water contamination means that it can be blended into gasoline at larger concentrations (10% v/v in Europe and 11.5% in the US) without any change in the engine design, storage tanks or retail station pumps.
  • It can also be blended into fuel alongside ethanol and enhances the performance of the ethanol blends by reducing ethanol's impact on vapour pressure, a problem which can hamper a wider use of ethanol in existing gasoline distribution channels.

Biobutanol offers better fuel economy than gasoline-ethanol blends, improving vehicle fuel efficiency and mileage.

"It is expected that transportation fuels will be at least 5.75% biofuel by 2010 and 10% in 2020."

GOING GREEN

Biofuels can potentially produce lower greenhouse gas (GHG) emissions than conventional fuels such as gas or diesel, although they have also been widely criticised for contributing to extensive farming and raised food prices in developing countries. According to BP data, biofuels from conventional crops such as corn or vegetable oils have a 10–90% GHG emission reduction on a well-to-wheels or crop-to-car basis compared to gas and diesel.

BP intends to undertake further vehicle and infrastructure product testing on 830,000 US gallons of biobutanol imported from China. The testing will build upon previous engine tests using conventional biobutanol, which suggest that biobutanol performs similarly to unleaded petrol. Test data has indicated that the energy density of biobutanol is closer to unleaded gasoline – around 26–27MJ/litre, compared to 21–22MJ/l for bioethanol and 32–33MJ/l for gasoline.

BALANCING THE FOOD CHAIN

As the bioethanol plants take off, concern has been raised that demand for wheat in the UK could wipe out UK wheat exports by about 2010. The Hull plant is predicted to consume about 1 million tonnes of wheat a year, equivalent to 5% of the UK's annual wheat production. BP and Associated British Foods have rejected suggestions that it could lead to a sharp rise in wheat prices, saying that there is enough surplus to cover it.

Another solution would be for farmers to increase their crops towards high-starch wheat varieties that produce higher yields per hectare. The NFU estimates that there is about 1.2 million hectares of spare arable land on which to grow wheat for the production of bioethanol.

Whatever the final outcome, the new plant at Hull will finally give the power industry some key figures to work with for renewable projects of the future.