Science - March 15, 2010

Bring on the green waste

In the course of a four-year PhD research project, the chances of discovering anything really spectacular are slim, but Kirsten Steinbusch did her research under a lucky star. During her research with the Environmental Technology department, she found a new method of turning organic waste into energy using volatile fatty acids, formed when microbes break down the waste. These substances stink to high heaven - Greenpeace uses them to drive away whalers - but Steinbuch was able to apply micro-organisms and some hard chemistry to transform them into a lucrative product: biodiesel. She is due to receive her PhD on Friday 19 March.

PhD researcher Kirsten Steinbusch
Fermenting stew
'Extracting energy from green waste is sustainable, but it has to be energy efficient; you should not have to put more energy into it than comes out of it', Steinbusch explains. 'I think I have found the method for doing this.' First she let microorganisms loose on the waste. They turn big molecules such as sugars, proteins and fats, into smaller molecules. Under the right conditions, without oxygen, what you end up with is mostly fatty acids, hydrogen and carbonic acid.
At first, Steinbusch concentrated on turning the volatile fatty acids into alcohol, but that did not get her far: she got very little alcohol out of them. 'When we did some more measurements in the fermenting stew - on the initiative of a student - we suddenly discovered relatively large amounts of somewhat bigger fatty acids such as caproate and caprylate', the researcher explains. 'This is a fabulous find, because you can use these substances for all kinds of purposes.' They can be raw materials for paints and dyes, and you can also make biofuels from them. To do this, the mixture must be heated to over 300°, after which the molecules pair up and form biodiesel.
Eureka moment
This was a real Eureka moment for Steinbusch. 'I went crazy. This makes it all worthwhile', she says enthusiastically. 'It was not yet known that a mix of innumerable microorganisms in a stew of rotting waste could consistently produce an end product like this.' This was reason enough for Environmental Technology to patent the method. It has many advantages over alcohol production from vegetable matter.  The raw material, green waste, is relatively cheap and the extraction of the end product is easier and cheaper than is the case with bio-alcohol. Another advantage is that the method makes no use of agricultural land and is therefore not in competition with food production or rainforest.
 Buying the patent
The PhD researcher has big plans for the process she discovered. She has decided to buy back a patent that environmental technology took out on the method from the University. Her newly established company, Waste2chemical, will continue to develop and exploit the technology in close collaboration with the University.