Complex protein fractions from grass, wheat, sugar cane and maize can be used as feedstocks for the chemical industry by means of biorefining. PhD student Ben Brehmer of Wageningen University made this proposition in his thesis.
Now that crude oil production in the world is declining, the development of alternate energy sources is accelerating. The chemical industry, which uses 8% of the fossil energy that is consumed in the industrialised world, cannot replace oil and gas with solar, wind, or nuclear energy. Brehmer believes that the chemical industry will eventually need to use feedstocks from biomass.
The researcher studied a series of crops that could possibly replace fossil raw materials. He determined the quantity of useful protein fractions the crops contain and how much feedstock per hectare they could deliver to the chemical industry. For the time being, the production of chemicals from biomass is too expensive, but Brehmer is exploring which crops could be the most useful in the future.
Brehmer calculated that the best crops for replacing fossil fuels are tropical crops such as oil palm and sugarcane. ‘This is because they grow year-round, which means they have higher production per hectare.’ But crops such as maize, wheat and potatoes also performed well in his test, actually better than the widely used rapeseed. ‘This crop has a low oil yield, while its production requires a relatively large amount of energy.' Brehmer also believes that Yatropha, a crop which he did not study, is unlikely to play a significant role. ‘This is because you cannot mechanise the production of yatropha .’
However, one surprising candidate is grass. It turns out that this crop contains many chemicals that are useful for chemistry and that these compounds are relatively easy to extract. One disadvantage is that the yield per hectare of grass is not very high.
According to Brehmer, the trick is to use all the useful components of the chemical feedstock crops and have the smallest possible amount of crop residue to be incinerated for low-value energy. As an example, he refers to maize production for bioethanol in the United States. ‘This product yields little more energy than it requires to produce. This is because only the starch in the maize kernels can currently be converted into alcohol, after which the remainder of the crop is incinerated. With new technologies, in several years 50% of the maize can be converted into bioethanol’, Brehmer predicts. ‘As a result, you will be able to replace two to three times more fossil fuels per hectare than you can now.'
Another development is also taking place. Brehmer: ‘Bioethanol is still a low-value application. You can also extract ethylene from the ethanol produced from maize and sugarcane, which is a more complex and higher-value product. A precondition is a large-scale and efficient production of bioethanol, with the smallest possible amount of residue. Then it will become profitable to filter more complex fractions for use in chemistry from your biomass.’
Ben Brehmer defended his PhD thesis on Friday 24 October; his supervisor was Prof. Johan Sanders, Professor in the Valorisation of plant-based production chains./ Albert Sikkema
The above article was written by the editorial staff of Resource, the weekly newspaper for Wageningen University and Research Centre. For more information, contact the press and science information officer of Wageningen UR, e-mail: pers.communicatie@wur or the editorial staff of Resource, e-mail: resource@wur.nl. See the archived articles at http://www.resource-online.nl