Monday, April 30, 2007

Bioenergy potential of maize

Mette Hedegaard Thomsen1, Jens Bo Holm-Nielsen2, Michael Madsen3, Piotr Oleskowicz-Popiel2, and Anne Belinda Thomsen1. (1) Biosystems Department, Risoe National Laboratory, P.O. Box 49, 4000 Roskilde, Roskilde, Denmark, (2) ACABS, Aalborg University Esbjerg, Niels Bohrs vej 8, 6700 Esbjerg, Denmark, (3) ACABS, Aalborg University Esbjerg,, Niels Bohrs vej 8, 6700 Esbjerg, Denmark

In Denmark, production of bioenergy mainly exists in form of incineration of straw, wood chips, and wood pellets in CHP plants. Energy crop cultivation is taking place to a very limited extend, since the economical feasibility compared to other available feedstocks is considered poor. Recent trials in Germany and Austria have shown that the yield per hectare from energy maize can be increased to 30 tonnes of dry matter per hectare by incorporating natural genes. Danish growth conditions for maize for animal feeding purposes yields 12-15 t DM/ha, but it has the potential of rising to 16-20 t DM/ha in the context of biorefining. 
Tabulations were made for the bioenergy potential from maize under Danish conditions. The present biogas yield is considered to be 2640-3690 Nm3/ha of methane, whereas implementation of the mentioned genes and refinement of the Good Farming Practice easily can increase the yield to 4220-5270 Nm3/ha of methane. These estimates are based on the assumptions that 1 kg of organic dry matter yields 290 L STP of methane, a methane percentage of 55 in the biogas, and that TS = 1,10 * VS.

 Maize silage has been evaluated for its potential as a feedstock in production of 2nd generation bioethanol in laboratory experiments performed at Risø National Laboratory. Pre-treatment of maize silage was performed at different temperatures, reaction times, and catalyst additions (Na2CO3, O2). Chemical analyses, enzymatic hydrolysis, and SSF with Bakers Yeast were performed in order to determine ethanol yields form this promising feedstock.