Electricity from straw

February 3, 2009
The new biogas plant is the first-ever to run exclusively on waste material such as corn stalks. There is no need to add edible crops. Credit: Fraunhofer IKTS

Researchers have developed the first-ever biogas plant to run purely on waste instead of edible raw materials -- transforming waste into valuable material. The plant generates 30 percent more biogas than its predecessors. A fuel cell efficiently converts the gas into electricity.

"Corn belongs in the kitchen, not in biogas facilities" - objections like this can be heard more and more frequently. They are protesting against the fermentation of foodstuffs in biogas plants that generate electricity and heat. One thing the opponents are afraid of is that generating electricity in this way will cause food prices to escalate. In collaboration with several small and medium-sized enterprises, research scientists at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden have developed the first-ever biogas plant that works entirely without edible raw materials.

"In our pilot plant, we exclusively use agricultural waste such as corn stalks - that is, the corn plants without the cobs. This allows us to generate 30 percent more biogas than in conventional facilities," says IKTS head of department Dr. Michael Stelter. Until now, biogas plants have only been able to process a certain proportion of waste material, as this tends to be more difficult to convert into biogas than pure cereal crops or corn, for instance.

This is not the only advantage: The time for which the decomposing waste material, or silage, is stored in the plant can be reduced by 50 to 70 percent. Biomass is usually kept in the fermenter, building up biogas, for 80 days. Thanks to the right kind of pre-treatment, this only takes about 30 days in the new plant. "Corn stalks contain cellulose which cannot be directly fermented. But in our plant, the cellulose is broken down by enzymes before the silage ferments," Stelter explains.

The researchers have also optimized the conversion of biogas into electricity. They divert the gas into a high-temperature fuel cell with an electrical efficiency of 40 to 55 percent. By comparison, the gas engine normally used for this purpose only achieves an average efficiency of 38 percent. What is more, the fuel cell operates at 850 degrees Celsius. The heat can be used directly for heating or fed into the district heating network. If the electrical and thermal efficiency are added up, the fuel cell has an overall efficiency of up to 85 percent.

The overall efficiency of the combustion engine is usually around 38 percent because its heat is very difficult to harness. The researchers have already built a pilot plant with an electricity output of 1.5 kilowatts, enough to cover the needs of a family home. The researchers will present the concept of the biogas plant at the Hannover-Messe on April 20 to 24. In the next phases of the project, the scientists and their industrial partners plan to gradually scale up the biogas plant to two megawatts.

Source: Fraunhofer-Gesellschaft

Explore further: Researchers obtain patent for new process that converts waste heat into hydrogen

Related Stories

Boosting the efficiency of solar panels

October 27, 2015

A UConn researcher has developed a light-harvesting antenna that could double the efficiency of existing solar cell panels and make them cheaper to build.

Student moves from theory to proof in fuel cell research

October 19, 2015

Sadia Kabir is exploring a new world in the basement of Farris Engineering Building. The Ph.D. engineering student works in the research group headed by University of New Mexico Distinguished Professor of Chemical and Biologicall ...

Recommended for you

Nevada researchers trying to turn roadside weed into biofuel

November 26, 2015

Three decades ago, a University of Nevada researcher who obtained one of the first U.S. Energy Department grants to study the potential to turn plants into biofuels became convinced that a roadside weed—curly top gumweed—was ...

Glider pilots aim for the stratosphere

November 20, 2015

Talk about serendipity. Einar Enevoldson was strolling past a scientist's office in 1991 when he noticed a freshly printed image tacked to the wall. He was thunderstruck; it showed faint particles in the sky that proved something ...


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (1) Feb 03, 2009
A great step forward.
5 / 5 (1) Feb 03, 2009
Now if it could process my fecal waste, and filter my water, maybe I could live off the gird....someday.
4 / 5 (1) Feb 03, 2009
Oops, i mean if it could be scaled down and put in my closet.
not rated yet Feb 06, 2009
Straw is already used in a large variety of places.... bedding for animals, traction in mud, barrier to stop flooding and erosion... some places are even building whole houses from bales of straw and coating them with clay.

Will there be enough straw to go around?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.