Wednesday, August 20, 2008

Efficient Ethanol

Corn - Photo Credit: MarS via Flickr

We at SDU are big fans of ethanol - if it is made from cellulosic materials. Corn ethanol is problematic. Making ethanol from corn consumes a lot of energy so the pay-off, or the net increase in energy, is small compared with other biofuels. To make corn based ethanol more energy efficient, researchers at Washington University are demonstrating a process used in breweries and wastewater treatment facilities: oxygen-less vats of bacteria that naturally feed on organic waste produced from the fermentation process.

This "new" process is one we have covered many times. (Link) The WU team is using a simple biodigester after the fermentation process. The biodigester uses bacteria in the absence of oxygen to produce methane.

As the bacteria break down waste, methane is released, which can be used to power the distillation process. The methane generated can offset much of the energy required to make ethanol.

From Technology Review:

Largus Angenent, a professor of chemical engineering, and his team at Washington University have tested anaerobic digestion on waste from ethanol plants and found that the process could cut down an ethanol facility's use of natural gas by 50 percent. The team has published the results in the recent issue of the journal Environmental Science and Technology.

Angenent says that the process would serve as a short-term solution until more-efficient biofuel, such as cellulosic ethanol, is commercially viable. "Rather than have hope for new technology that comes to fruition in 10 or 20 years, we need technology we can implement now," says Angenent, who recently became an assistant professor of biological and environmental engineering at Cornell University. "This is an interim process, and it's off the shelf."

Nearly all ethanol biofuel in the United States is made from corn. Typically, the ethanol production yields organic waste that is then consolidated into two parts: a dry, cake-like substance and a syrupy solution, called thin stillage, that's layered on top. The concoction is used as animal feed. Angenent says that a large portion of this feed, particularly thin stillage, which is laden with salts, provides low nutritional value but may have high energy potential for powering a plant when broken down via anaerobic digestion.

To test this theory, the researchers cultivated thermophilic bacteria from a wastewater treatment plant in two small, five-liter anaerobic digesters. Angenent and his colleagues then slowly began feeding waste samples into the digesters, which were kept at 55 °C to maximize the bacteria's activity. As the digesters ran, the team measured the amount of methane released.

Via: Technology Review

Check: Sustainable Design Update

Monday, August 18, 2008

Cow Power Could Provide More Energy Than Offshore Drilling

Cow Power!

From the University of Texas:

Converting livestock manure into a domestic renewable fuel source could generate enough electricity to meet up to 3 percent of North America's entire consumption needs and lead to a significant reduction in greenhouse gas emissions, according to U.S. research published July 24, in the Institute of Physics' Environmental Research Letters.

The journal paper, 'Cow Power: The Energy and Emissions Benefits of Converting Manure to Biogas', has implications for all countries with livestock as it is the first attempt to outline a procedure for quantifying the national amount of renewable energy that herds of cattle and other livestock can generate and the concomitant greenhouse gas emission reductions.

Livestock manure, left to decompose naturally, emits two particularly potent greenhouse gases– nitrous oxide and methane. According to the Intergovernmental Panel on Climate Change, nitrous oxide warms the atmosphere 310 times more than carbon dioxide, methane does so 21 times more.

The journal paper creates two hypothetical scenarios and quantifies them to compare energy savings and greenhouse gas reducing benefits. The first is 'business as usual' with coal burnt for energy and with manure left to decompose naturally. The second is one wherein manure is anaerobically-digested to create biogas and then burnt to offset coal.

Through anaerobic digestion, similar to the process by which you create compost, manure can be turned into energy-rich biogas, which standard microturbines can use to produce electricity. The hundreds of millions of livestock inhabiting the United States could produce approximately 100 billion kilowatt hours of electricity, enough to power millions of homes and offices.

And, as manure left to decompose naturally has a very damaging effect on the environment, this new waste management system has a net potential greenhouse gas emissions reduction of 99 million metric tonnes, wiping out approximately 4 percent of the country's greenhouse gas emissions from electricity production.

The burning of biogas would lead to the emission of some CO2 but the output from biogas-burning plants would be less than that from, for example, coal.

More at: The University of Texas

Photo Credit: Outdooralex at Flickr