Getting an extra ‘Nip’ from Whisky

The waste from Scottish whisky production will be converted to produce an advanced biofuel that is very close to gasoline in energy density.

Each year the Scottish whisky industry produces about 1.6 billion liters of ‘pot ale’ and 500,000 tonnes of ‘draff’ as waste by-products. Celtic Renewables, a spin-off company from Edinburgh Napier University, is using an updated version of a commercial process from the last century to convert that waste into butenol for use in the chemicals industries or as a fuel.

Advantages over ethanol

Biobutanol is non-corrosive. It has a lower vapor pressure and higher flashpoint than ethanol, making it easier to store and handle. Biobutenol is approved as a bio-blend for fuels in the UK. The US Environmental Protection Agency approves blends of up to 16% biobutenol with gasoline. By comparison, ethanol is limited to 10% blends. Butanol can also be blended with a greater range of fuel grades than ethanol. Because it is so similar to gasoline, biobutanol can be stored in gasoline tanks and pumped through gasoline pipelines (ethanol cannot).

The US Navy has developed methods to convert one variant of biobutanol into jet fuel. It can also be converted to diesel, or used in a range of chemical products and plastics.

Celtic Renewables’ butanol production process is well-tested. Between the 1920s and the 1980s, acetone-butanol-ethanol (ABE) production was common across the world. However, in the 1960s a flow of cheap solvents from the expanding petrochemical industry made ABE production uncompetitive. It continued in markets such as South Africa and the USSR where access to fossil fuel was difficult. The last ABE plant in China closed in 2004.

Innovation creates a market

However, scientific improvement of the fermentation process is driving down the cost of ABE, while the demand for sustainable chemicals and fuels is opening new markets. Edinburgh Napier University researched the fermentation process over a number of years before the establishment of Celtic Renewables.

In Scotland alone, the market for biobutanol as a fuel-blend could be more than $85 million per year. Biofuels Digest predicts biobutanol production will grow rapidly from pilot stage today to more than 500 million gallons by 2014. That’s about 60% more butanol by 2014 than the entire US biodiesel market today.

Many companies struggling to produce ethanol from corn at competitive prices are looking at retrofitting biobutanol production into their plants because of the added value and flexibility of the end-product.

One of the attractions of biobutanol is that it can be produced from a wide range of residues, including wood, sugar cane bagasse and green bio-waste. One US biobutanol producer is exploiting paper mill waste flows. Once up and running, they predict biobutanol production in the $2 per gallon range. Around the world, the search is on for waste residues with unused sugars that can be converted to biobutanol to eliminate the need for food crops as a biofuel feedstock.