Is Bioenergy in Scott Valley's Future?

Part 3: Gasification---Abundant, Clean, Adaptable Energy

Last in a three-part series

By Ric Costales

Recently, the USFS and OreCal RC&D secured a grant for a feasibility study for a bioenergy project in Scott Valley. They selected gasification as the generating process, and will use it to produce heat. The reason heat rather than electrical power or combined heat and power (CHP) was selected was to keep the initial biomass project as simple and inexpensive as possible. Gasification was chosen as the process because it is a proven technology, relatively simple, highly adaptable to a variety of applications, is extremely clean and, most importantly, we have a massive supply of readily available fuel.

Since gasification has the potential for widespread use in our area, it is important for the community to understand the basic principles, advantages and drawbacks. This background will help prepare for the development of unutilized biomass resources in the most efficient manner possible.

History

Unknown to most people, gasification of biomass has been around since 1840. Literally astonishing is that in Europe during WWII, wood or charcoal powered an estimated 100,000 vehicles. Worldwide from 1940-1946, more than a million gasifiers were providing motive power, electricity and heat. In Denmark during this time, 95% of all farm machinery, tractors, trucks, stationary engines, and boats were powered by woodgas. In fact, up until 1970, charcoal-burning taxis were still common in Korea.

Because the United States has never suffered fossil fuel shortages we have not felt the need to use this remarkably simple technology. It has always been cheaper and easier to burn dinosaurs rather than wood. That will someday change. Because the change may be looming on the horizon, a lot of attention has been brought to gasification.

The Basics

Though there are many types of gasifiers, the principles are all the same. Biomass is combusted in a low oxygen/high heat environment. Complete combustion normally results in high percentages of carbon dioxide and water. However, because of the gasifier¹s unique design, the carbon, hydrogen, and oxygen atoms in the molecular structure of the biomass are converted into relatively high percentages of hydrogen, methane and carbon monoxide. These gases are flammable and are the source of the energy available from gasification.

The combination of these gases, called "producer gas" or "woodgas," can then be burned directly to produce heat or steam, or can be funneled into an internal combustion engine (ICE) to power it just the same as any fuel. All forms of ICE's, including diesels, can be modified to operate with producer gas.

Some gasifiers are designed to produce a more concentrated form of woodgas called synthesis gas or "syngas." Syngas has approximately 30% more heating value than woodgas although it has only about 2/3 the value of natural gas. Syngas can also be efficiently compressed and stored for later use in much the same way as propane.

Uses

As already mentioned, woodgas or syngas can be burned in ICE¹s or to make heat. Either of these uses have all sorts of applications in Scott Valley. For example, as prices to connect to the power company skyrocket and electrical rates soar, home grown power systems are becoming more appealing. A 15 kilowatt gasifier genset was tested in Hoopa and proved to be efficient and reliable. A 50 kW plant will be installed at the Opportunity Center in Mt. Shasta in 2005.

Gasifiers can also power water pumps directly or can power gensets to run electrical pumps. Etna High School could save thousands of dollars every year by firing its boiler with woodgas rather than propane. Many schools from Montana to Vermont have done exactly that.

Businesses that need large amounts of heat as well as electricity, such as CalForest with their greenhouse operation, can especially benefit from the 80+% efficiency of gasifiers when they are used in combined heat and power (CHP) applications.

Advantages

As well as broad adaptability to small-scale power applications, current gasification technologies are very clean sources of energy. As well as meeting or exceeding all current California emissions standards, gasification of woody biomass is considered "greenhouse gas neutral." This means that while gasification produces greenhouse gases, the gases produced are no more than what the biomass source would produce naturally through decomposition.

Another advantage of the technology is that it would allow a significant offset to the costs of forest health and fuel reduction projects by finding an economic use for the currently unusable material generated.

Best of all, gasification allows for a renewable source of domestically produced energy that helps support a local economy. What could be better than that?

So what¹s the catch?

If this is such a proven technology with so many benefits, why haven¹t we been using this for years? The answer is that like other technologies that have been developed but still sit on the shelf, there are some bugs that still need to be worked out before gasification becomes common.

Tars and particulates that are suspended in the woodgas when it is produced are hard on engines. Gas cleanup and conditioning head the list of thermochemical research projects at the National Renewable Energy Lab (NREL) as well as numerous private companies.

Additionally, virtually all gasifiers demand fairly uniform standards when it comes to dimensions and moisture content of the fuel. Moisture must be below 20% and the fuel must be large enough that it allows sufficient gas flow through the feedstock, but not so large that the pieces can get bound up in the gasifier.

Together, both issues demand somewhat complicated processing and handling of the biomass. The choice is currently between a significant loss of biomass by filtering for the proper size chips or the added expense of the manufacture of pellets that would allow full utilization.

The Future

It is a virtual certainty that the challenge of economically using biomass to produce energy will be solved in some way. Gasification is one of the brightest prospects. Whether gasification will prove to be the "holy grail" that energy technocrats are seeking remains to be seen. What is most likely, however, is that gasification along with other biomass technologies will combine to form an increasing, far more significant percentage of our national energy portfolio.

Perhaps we here in Scott Valley can help the process along.

For more information on themochemical conversion of biomass and other renewable forms of energy, visit the National Renewable Energy Lab.

Note: A workshop on Bioenergy sponsored by the Scott River Watershed Council will be held Saturday, April 3 from 10 am to 4 pm at the Scott Valley Grange in Greenview. Lunch will be provided.

Biomass Press Release #1

Biomass Press Release #2

Biomass Fact Sheet