The 'Holy Grail' of biofuels

So, why is fermenting waste so exciting for the whole renewable fuels industry? It is now painfully clear, even to the US President, that an ever-warming planet and decreasing fossil fuel reserves are problematic for the oil industry. We need alternative energy sources that are clean, sustainable, easy to handle and cost-effective - and we need them kinda quickly.

Some years ago, bioethanol was hailed as the answer. However, the predicament of creating extra arable land by cutting down CO2-producing rainforests and using edible crops to fuel our cars and trucks is increasingly apparent, particularly as three-quarters of the world's population rely on agriculture to live and do not drive cars.

Food riots are becoming increasingly commonplace, and have intensified in the past few months, while the possible link between high food prices link and bioethanol production is a regular news item and is on the agenda of several global meetings this year, including the G8 summit in July.

Cellulosic ethanol (CE) has emerged as a possible new answer, with potential sources ranging from corn and sugar cane leftovers to grasses and other plants grown specifically (and cheaply) for that purpose. Cellulose is indeed the most abundant organic molecule on the planet and scientists know how to turn it into ethanol.

However, it is not all that easy to turn the complex polysaccharides in cellulose into fermentable sugars, and certainly not in a cost-effective way. In fact, reducing the cost of cellulose hydrolysis remains the biggest hurdle to the future of the CE industry.

Research organisations are leading the way to a solving these problems, backed now by powerful global initiatives, governments and multinational companies. It seems that the powers that be and the money behind them have realised the importance of plant-based biomass as an inexpensive and environmentally friendly energy source that does not affect the food and feed chain.

According to Dale, CE is the "holy grail of bioethanol at the moment".

Commercial CE plants are already in operation in Canada and Spain using wheat straw, with many others planned in US and Europe.

"Biomass represents a vastly bigger resource than crops grown specifically for conversion to ethanol, and much of this waste is just left to rot or be burnt," Dale says.

"Sugarcane is probably the best example of that. In Australia, the waste is burnt - about 50 per cent for power to power the mills and the other 50 per cent to get rid of it. Some groups are setting up co-generation plants to take some of the excess power generated from the waste and put it back into the grid but this is quite expensive from a capital equipment perspective."

Others are adding enzymes to the waste in massive amounts. However, even with recent scientific improvements in the efficiency of natural enzymes from fungi or other sources, the amount of enzyme needed for a useful-size plant is neither economical nor practical.

"On current estimates, you would need 15 metric tonnes of enzyme every day and the enzyme fermentation plant would be bigger than the ethanol plant!" In fact, the US Department of Energy Biofuels program recently identified the high cost of cellulose enzymes as the key barrier to economic production of CE.