How Fermenting Paper Gets You Fuel
What happens usually with waste paper from offices and homes? We expect it to be recycled and then encounter it again as exactly that: recycled paper. But when looking at fuel, we may not get the idea that this fuel once may have been paper. Since 1996 that has been an option, though.
The Conventional Cycle of Paper
Here’s a wonderful infographic from the UK.
For all the DIYers out there: You even can recycle paper yourself and turn them into paper logs for cold winters, as shown here.
An Unconventional Cycle of Paper
Back in 1996, scientists interestingly found a way to economically fuel your car with paper-turned fuel.
“Now all our waste office paper can be turned economically into car fuel, say researchers at the University of Florida in Gainesville.”
Simplified this looks like this:
Paper + fermentation with genetically engineered bacteria → ethanol
This is the economical way to turn paper into fuel with ethanol being added to the petrol to make it burn more cleanly and efficiently.Earlier, a similar attempt was made using yeast which turned out to be uneconomical as the system needed expensive enzymes. To get one litre of ethanol, the yeast-based process by Ingram and his team of microbiologists from Florida University only consumes 25 per cent of the enzymes. With savings that high, the bacterial conversion can become a financially viable option.The only bacterial strain (Zynomonas mobilis) that has yeast-like [enzymes] for converting sugars into alcohol was found in Mexico, where it had been used for centuries to ferment agave into pulque which is brewing a tequila-like drink. The downside to it is its delicacy, though. It wouldn’t survive the process. So a more robust bacterium (Klebsiella oxytoca Strain P2) had to be found to have the delicate alcohol-producing genes transferred into (after having been isolated). There is plenty of Klebsiella oxytoca Strain P2 in pulp and paper mills. Let’s try to simplify this procedure from Andy Coghlan’s great article to make the science also accessible to non-scientists like me.
How Fermentation Turns Paper Into Fuel
- Paper is mixed with hot water.
- Paper turns into a mushy pulp.
- Cellulose and hemicellulose polymers are found in the cell walls of trees need to be broken down.
- An enzyme is a substance produced by a living organism which acts as a catalyst to bring about a specific biochemical reaction. They are the kick-starter.
- In the yeast process, only the expensive enzyme βgalactosidase can break down cellobiose (pairs of connected glucose molecules plus various other molecules, pentoses and hexoses e.g.).
- Enzymes (cellulases, extracted from fungi) break down carbohydrate polymers in a dilute acid solution into simpler sugars.
- K. oxytoca is a genetically modified bacterium.
- K. oxytoca has genes that break down simple sugars which yeast cannot do.
- Cellulase is recycled to achieve even higher savings. Enzymes are not strong enough to break down lignocellulose fibres, so centrifuging does the job.
- In this step, ethanol is distilled from the liquid from the centrifuge.
- Distilling is purifying a liquid by heating it so that it vaporizes, then cooling and condensing the vapour, then collecting the resulting liquid.
- There is still active cellulase attached to the fibres. This is added to the next paper batch, so that less fresh enzymes need to be used.
- These simpler sugars are brewed into ethanol by help of the new K. oxytoca genes.
The ‘Economical’ in Numbers
On the production side:
Bacterial process: just 8 cents need to be spent on enzymes per litre of ethanol produced.Yeast process: 30 cents need to be spent on enzymes per litre of ethanol produced. A whole litre of ethanol costs around 30 cents.It is said that from 100% paper, 80% are turned into fuel which exceeds the expectations of scientists and satisfies those who want to make profit from this technology.
On the consumption side:
BC International, a Massachusetts company holds the licence to commercialize this technology, as its vice president is convinced that paper or agricultural waste turned into ethanol has the potential to compete with the price of conventional ethanol made from corn. Depending on each country, a specific percentage of ethanol is added to petrol to decrease pollution and enhance combustion. In the US for instance it is 15 per cent by volume of ethanol that is added to petrol.
Your Take-Away
Now that you know how to make good use of waste paper, you can apply it to your everyday life. One of the big benefits of fermentation in connection to food is that, by preserving food, you make sure that nothing goes to waste. So why not learn from food fermentation and apply it to your household by stopping precious paper from going to waste? Or why not even preserving our world in a way and make it last longer - thanks to fermentation?
Content by Martina Hollweck; Images by Michael Gaida and Sarah Richter.