Bioethanol

Evaluation of the potential of new raw materials and  new microorganisms for bioethanol production.
 

The polysaccharides in lignocellulosic materials (crop residues, house waste, leftovers from forestry industry) can be used for bioethanol production. Efficient pre-treatment and fermentation technologies are being developed for that purpose by BEM members.

Optimisation of pre-treatment of fermentable CHO products
The cellulose cannot be enzymatically hydrolyzed to glucose without a physical and chemical pre-treatment. The physical and chemical protection of cellulose must be removed before subsequent hydrolysis and fermentation steps for bioethanol production. The pre-treatment processes normally applied on the different substrates are acidic hydrolysis, steam explosion and wet oxidation. A problem for most pretreatment methods is the generation of compounds that are inhibitory towards the fermenting microorganisms, primarily phenols. Degradation products that could have inhibitory action in later fermentation steps are avoided during pre-treatment by wet oxidation.

Here at Risø, alkaline wet oxidation (using high temperature, oxygen and carbonate) has been shown to be an efficient pre-treatment method for wheat straw, producing a hydrolysate rich in hemicellulose and highly (67 %) convertible cellulose fibres. The hydrolysate constituted 9 g/L solubilised hemicellulose, 6 g/L carboxylic acids and 0.3 g/L phenolic lignin degradation products. 

A project is under way in cooperation with Elsam, an industrial partner, to develop hydrothermal treatment of wheat straw on a pilot plant scale. The objective of the project is to develop a pilot plant for pre-treatment of plant fibre biomass for bioethanol production and production of solid alkali free biofuel for electricity production.  Elsam uses co-combustion of coal and straw (up to 15%) for  their electricity production, and more straw is wished to be used to this purpose. The reactor removes the high potassium chloride content from the straw, as this damages the boilers by corrosion. The enzymatic convertibility of cellulose and hemicellulose are also determined in the solid fibres and liquid extracts to assess potential ethanol production following the pre-treatment of biomass.

A cooperation between the Chinese authorities and Risø has also been established for optimisation of pre-treatments methods of substrate such as corn stover, an important substrate for ethanol production in China.

  

bioethanol can be produced from straw of ceral crops

pilot plant fro pre-treatment of straw at elsam, partner from industry

 dry freezing of fermantable products for chemical analysis

chemical structure of cellulose

molecule of ethanol

 

 

New raw materials and microorganisms for bioethanol production
The aims of this project are to evaluate the potential of new raw materials and of new microorganisms for bioethanol production.
The first aim of the project is to evaluate the suitability of grass-clover leys as feedstock material for fermentation. Clover/grass mixtures present a double advantage, they decrease the reliance on external sources of nitrogen (produced using fossil fuels) both in the field and in the fermentor. The clover plants are fixing nitrogen from the atmosphere and the ley do not need to receive mineral nitrogen fertilizer in the field. N fertilizers represent about one third of the energy budget of plant production in the developed countries. Harvested grass-clover also typically has a high content of nitrogen in the form of proteins. When material low in nitrogen is used as a substrate for the fermentation, it must be supplied in the form of urea, a major energy cost.

The use of grass/clover mixture as raw material has the potential to increase the energy efficiency of the ethanol production system, by decreasing the reliance on external sources of nitrogen, in the field and during fermentation.

After pre-treatment, a second aim is also to extract and purify hemicelluloses of the substrate to be utilized in the production of biopolymers.

A third aim in the project is to study the ability of a new fungus strain to ferment the pentosan fraction of clover into ethanol. The pentosan is a constituent of hemicellulose typically unavailable to the yeasts used during fermentation for the production of ethanol. The utilization of both the cellulose and hemicellulose fraction is required in an economically viable bioethanol production.

 
Completed
 

Page updated  by   08.10.2010