Enzyme Cocktails for Ethanol | Green Energy News

March 4, 2010 – Vol.14 No.50

ENZYME COCKTAILS FOR ETHANOL.
by Bruce Mulliken, Green Energy News

It’s census time again here in the US. The Feds will be taking a tally of people so it knows how money and resources are best distributed. But perhaps the Census Bureau should include material possessions as well, such as how many gasoline-fed internal combustion engines are owned.

Most of the cars and trucks in the US are fueled by gasoline. But then there are other engines, everything from lawn mowers and weed wackers to outboard motors and snow mobiles. Including the more than 200 million vehicles powered by gasoline there are probably 300 million engines powered by America’s most popular fuel. And that’s just the US. Globally there’s what, over a billion gasoline/petrol-fed engines in service? I’m wildly guessing 1.3 billion engines to feed.

There’s plenty of market space for alternative fuels.

So far, in terms of a liquid fuel for spark-ignited engines, there is no commercially-available replacement for gasoline other than gasoline-ethanol blends, such as ethanol light (about 10 percent ethanol, E10) to 100 percent ethanol (E100) for flex-fuel vehicles in Brazil. In the US E85 is the highest blend available at the pump, and those pumps are rare.

Sure, there are some fuel system modifications needed so that gasoline engines can run on strong ethanol blends, but compared with converting them to run on gaseous fuels like natural gas or liquified petroleum gas (Propane), the modifications are minor. (Other liquid replacement fuel possibilities like butanol are not commercially available.)

Ethanol has received considerable bad press in recent years, most notably that corn-derived ethanol can be responsible for more carbon emissions than gasoline in a full life cycle analysis. As is typical with reporting in the US, one bad word can taint an entire industry.

Other complaints are that it is generally a bad idea to use a food for fuel, and fuel consumption with ethanol is more than with gasoline. And, of course, ethanol costs too much, needing a perpetual Federal subsidy.

The key words in the complaints are “corn ethanol,” but “corn” is often dropped leaving “ethanol” to take the battering in the press making people think that all ethanol is evil. It isn’t. Other bio sources of ethanol fare much better in terms of overall carbon emissions reduction. The US EPA says, for instance, that Brazilian sugarcane ethanol has a 61 percent reduction of total life cycle greenhouse gas emissions compared with gasoline, when including emissions from indirect land use.

Full life cycle studies that follow ethanol making from its plant source to fermentation to distillation to distribution and finally burning as a fuel can be extremely complex – every little factor needs to be examined. (For instance, what are the emissions from an average diesel farm tractor?)

But, it is reasonable to think that, generally, the less energy needed to grow a fuel crop (or NO energy if the resource is a waste product) combined with the least amount of carbon-based energy is needed to convert that resource into fuel, along with accounting for the lower energy content of ethanol, then life cycle emissions should be the lower than gasoline. After all, the plant sources to make ethanol fuel are carbon neutral. That alone is a good starting point in ethanol’s favor.

Of course any effort to replace gasoline with ethanol isn’t only about lowering life cycle emissions it’s also about energy security. If nations can grow their own fuel they won’t be exporting money by the container load. Brazil seems to know this.

The problems associated with ethanol from corn has led to the effort to make cellulosic ethanol, or better put, ethanol made from plant sources we don’t eat, such as everything from wood to grasses to waste paper.

The key to ethanol making is a good source of sugar (like that Brazilian sugar cane) which in nonfood sources is not easy to come by. Though sugar is available in these nonfood sources it’s locked up in the plant’s cell walls. Enzymes are needed to break down those walls and release the fermentable sugar.

There are all kinds of enzymes including those in our stomachs that break down wide varieties of food. Like the enzymes in our stomachs, what’s being looked for by ethanol researchers are plant-derived enzyme cocktails that will break down a variety of different feed stocks for fuel.

At the University of Central Florida professor Henry Daniell has been working on these cocktails that can include multiple enzymes.

A press release from UCF says this:

“ Depending on the waste product used, a specific combination or "cocktail" of more than 10 enzymes is needed to change the biomass into sugar and eventually ethanol. For example, orange peels need more of the pectinase enzyme, while wood waste requires more of the xylanase enzyme. All of the enzymes Daniell's team uses are found in nature, created by a range of microbial species, including bacteria and fungi.”

In his research Daniell cloned the enzyme genes from wood-rotting fungi and bacteria then produced enzymes in tobacco plants.

“Producing these enzymes in tobacco instead of manufacturing synthetic versions could reduce the cost of production by a thousand times, which means the cost of making ethanol should be significantly reduced,” Daniell said.

Tobacco is an ideal producer of the needed enzymes. It’s grows easily – an estimated 40 metric tons of biomass are produced annually per acre. It’s not a food crop. Tobacco farmers could keep growing it and sell it as fuel source instead of for smoking.

Dr. Daniell’s plant-derived enzyme cocktails could break down switch grass, straw, paper, even waste orange peels for the sugar stored in them.

“There's also an abundance of waste products that could be used without reducing the world's food supply or driving up food prices. In Florida alone, discarded orange peels could create about 200 million gallons of ethanol each year,” Daniell said.

Daniell’s team conducts its research at the Burnett School of Biomedical Sciences at UCFs College of Medicine.

Links:

University of Central Florida
http://www.ucf.edu

UCF Burnett School of Biomedical Sciences
http://www.biomed.ucf.edu/index.php?option=com_frontpage&Itemid=1