September 29, 2007

Woody Biomass: Feedstock for BioEnergy


This article contains the text and some images from the second half of a speech I presented at the Energy from Biomass and Waste conference in Pittsburgh, PA on September 27. It follows from the first half of the presentation titled Woody Biomass: Fuel for Wildfires which shows recent increased wildfire activity and the consequent greenhouse gas emissions from public forests. It suggests that private industry has a strong role to play to help deploy the necessary woody biomass harvesting processes and infrastructure of biomass conversion facilities to make proper forest management economically sustainable.

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Woody Biomass: Feedstock for BioEnergy

I believe that the conversion of biomass to energy represents not only a sustainable, clean alternative to fossil fuel energy but that implementing these emerging technologies can help us solve environmental and ecological challenges of the new millennium.

How can we capture forest fuels to lessen the threat of megafires while simultaneously generating clean, renewable bioenergy?

U.S. Patchwork of Renewable Energy
Right now we are seeing a surge in the development of many decentralized renewable energy installations (click map to enlarge). Wind energy on the coast and wind corridors of the interior, solar energy in the Sun Belt, corn ethanol in the Corn Belt.

But what about the unfilled regions on our patchwork of regional renewable energy projects? What technologies will fit there?

The revitalization of the Corn Belt is illustrative of what could happen in the forest regions of the country-
hundreds of biorefineries, billions of gallon of liquid fuel, stronger feedstock prices, revitalized communities, tens of thousands of jobs, rising land equity and stronger communities.

Photovoltaic vs. Photosynthesis arrays
I come from Studio City, California which is also the home to the environmentalist Ed Begley, Jr. I have had lunch with Ed and seen him give several presentations. At one he stunned his audience. He said “It may surprise many of you to hear that I am a BIG supporter of nuclear energy…" “...as long as it is kept 93 million miles away from Earth.”

Sure enough, Ed has some solar arrays on the roof of his home which convert sunlight into electricity. Here is a picture of him cleaning the arrays because otherwise their efficiency drops dramatically.

I am all for solar cell research to help lower their manufacturing expense and raise their energy conversion efficiency. Solar arrays are good at converting light to electricity but not good at storing the electricity. Here are listed some of their other drawbacks:
• Cells are not renewable
• Expensive to manufacture & install
• Dormant at night
• Cannot store electricity
• Limited climate and regional applicability

I submit that leaves are natures also “solar cells” using sunlight, carbon dioxide, and water to create stored energy in the form of sugar. Trees are “solar arrays” that have many advantages over photo voltaic arrays. They reproduce. They work in many more climatic regions of the world, produce and recycle their own solar collectors (leaves), store their energy in the form of sugars, clean the air of greenhouse gases, transpire water at night, and sequester half their dry weight in combustible carbon.

In so many ways, trees are the perfect solution to global warming and the effort to produce renewable energy.

Woody biomass availability
Let me be clear, when we talk about collecting woody biomass we aren’t talking about logging trees.

The USDA identified woody biomass as small diameter trees and underbrush, the residues of the logging and forest products industries, and urban wood waste. In their Billion Ton Report they estimated that there was over 367 million tons of woody biomass produced each year in the U.S. Here, as abroad, it is the number one renewable energy technology for creating steam, heat, and electricity. And it is growing.

With woody biomass being produced at so many locations throughout the country it is easy to see that their conversion to electricity and biofuels could fill significant patches on our national renewable energy “quilt.”

In fact, for generations, the forest products industry has utilized burning woody biomass to generate steam, heat, and electricity. The biggest drawback with combustion is the emissions it generates - but modern systems include scrubbers for removing toxins and particulate matter. New wood burning systems are being installed to replace coal burning facilities.

As concerns about global warming grows, many companies are looking at gasification systems for more efficient heat recovery and cleaner emissions control. The whole point of gasification systems is to capture emissions so they can be converted into synthesis gas - a clean burning, renewable alternative to natural gas (which is a fossil fuel).

If we add to forest biomass the potential biomass tonnage from growing hybrid poplar and other energy crop trees we could easily see in excess of half a billion tons of woody biomass available for bioenergy conversion each year. Efforts are underway to create new fast growing hybrid trees specifically designed to maximize carbon sequestration, bolster pest, drought, and fire resistance - and streamline processing efficiency.

There is plenty of marginal land throughout the U.S. where hybrid crops could be grown - supplying new energy crop options where other alternatives are not workable. Such “plantations” would help fix the land against erosion, improve water and air quality, and provide enhanced carbon sequestration capacity.

Furthermore, the sugar storage capacity of woody biomass and hybrid trees is a potent source of feedstock for conversion to biofuels. But how do we do that?

Woody biomass conversion technologies
Let’s compare the three generations of conversion technologies for creating biofuels from biomass.


Generation 1 - Sugar Fermentation In sugar fermentation the corn, sugar, or starch is warmed in water with yeast and fermented into an alcohol that is then distilled into pure ethanol. It is a batch process moving from vat to vat that takes approximately 2 days to complete. The primary residues of the process are converted into livestock feed called distiller dried grains (or DDG).

There are concerns about this method of creating ethanol:
1. The feedstock cannot be blended with any other feedstock.
2. The feedstock could be used as food .
3. The amount of energy contained in the ethanol is only slightly more than the energy expended producing it (a factor of 1.3).
4. It is a water-intensive process when you consider the cultivation of the feedstock and the inputs during fermentation.

But, the yield is high and it is a mature technology with over 100 commercial-scale biorefineries in operation and dozens more coming online each year.

Other conversion processes involve converting cellulosic feedstock (like woody biomass) into biofuels. The way that wood stores energy is by photosynthesizing sugars stored in two forms - hemicellulose and cellulose - with a combustible called lignin supplying the fibrous support of the tree.


Generation 2 - Biochemical Cellulosic Conversion The second generation of biomass conversion technologies involves breaking down wood’s molecular bonds using biochemical agents.

The difference between this process and sugar fermentation is the simple addition of the two-day breakdown step (represented in the blue zone). Here enzymes and acids separate the sugars from the lignin - the sugars are fermented and distilled into ethanol while the lignin is combusted to generate steam to heat fermentation. Principal research is focused on developing more efficient enzymes that can be produced at low cost.

Here is how Generation 2 compares with Generation 1.
1. The feedstock can include woody biomass, industrial and urban waste wood.
2. It takes longer but because the sources of cellulose do not require much cultivation and are usually already exist as residues of other processes, so the energy return is roughly five times that of sugar fermentation.
3. It uses more water during the multi-vat process - but there isn’t much water use during forest growth.
4. A major expense is the price of producing the enzymes which include high research overhead and royalties. That price will come down.

There are pilot plants in operation at private and educational research facilities around the world.


Generation 3 - Thermochemical Cellulosic Conversion The 3rd generation technologies use thermochemical processes - primarily gasification or pyrolysis - to break down the biomass into a synthesis gas, or syngas (composed mostly of carbon monoxide and hydrogen), which is converted into ethanol.

Again, a gasifier heats up the feedstock, which can be a blend, with high heat (2,500°F) to create the syngas. Instead of the syngas being sold as a product of gasification, it is exposed to a catalyst or fermented using bacteria that convert it into ethanol and and water.

Range Fuels uses a catalyst to enact the conversion. BRI uses a patented microorganism to ferment the syngas to ethanol.


1. Unlike Generation #1 and #2, the feedstock for generation 3 can be blended with all sorts of alternative raw materials - tires, autofluff, pet coke, municipal solid wastes, etc. - which makes feedstock procurement much more sustainable over the long haul.
2. The specific blend affects the yield with higher energy-content feedstock producing higher yields.
3. It is continuous requiring mere minutes for processing rather than days for generations #1 and #2.
4. It uses very little water - in fact it captures extra water as a product of fermentation.

The Agenda 2020 Technology Alliance of the American Forest and Paper Association recently published the” Forest Products Industry Technology Roadmap.” It illustrates where two conversion steps - one using biochemical and the other thermochemical processes - could be inserted into a standard pulp mill workflow to create new profit streams.

It also forecasts the return the plant management could expect for a typical tons per day volume. This could revitalize the paper and pulp industry. The real key to economic feasibility the commitment of the marketplace to renewable fuels.

In summary …
1. We can limit wildfires by thinning forests
2. Woody biomass stores abundant energy
3. We can use woody biomass to create heat, produce steam, and generate electricity
4. Emerging technologies will produce ethanol from woody biomass
5. Successful deployment of new wood-based technologies can revive stagnant industries
6. New industries can strengthen new communities

Here’s a final thought:

In 1803, Thomas Jefferson signed the Louisiana Purchase - effectively doubling the land area of the United States. He predicted it would take 1,000 years to settle the new territory. We laugh at his miscalculation - after all, it seems that we have settled his land and started to retreat from it - preferring urban life over rural.

But he might have been right. Maybe we are about to engage in renewed settlement of the nation’s rich rural midsection. We have 800 years to go and renewable energy made from woody biomass can play a big role in supplying renewable energy for that future while providing us with the means to manage our environmental sustainability.

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technorati , , , , , , , , decentralization

7 comments:

Mark Fitz said...

This is a great post. In depth and well done.

toi said...

According to a presentation at the Florida Farm to Fuel Summit in 2007, a company called Green Circle in Florida's panhandle is currently exporting 500 million tons of wood pellets from Fla. to Europe each year, today, used for heat generation and such. It is only because carbon dioxide is an unregulated constituent that it isn't used in the state and nearby. Europe is willing to pay more for the product in an effort to comply with carbon trading requirements.

toi said...

correction - the Green Circle plant in Florida is under construction, not yet in operation. Here is a good article about it: http://www.biomassmagazine.com/article.jsp?article_id=1331

C. Scott Miller said...

Thanks for the comment.

I was at that conference, too, and wrote an article on it at http://biostock.blogspot.com/2007/07/floridas-farm-to-fuel-summit.html including mention of the Green Circle Plant.

Wood pellets have their advocates in the U.S. as an alternative to heating oil and as a fuel for co-firing with coal at power plants. But because it is combusted it is not really seen as a longterm zero emission technology solution.

Just like Europe is inclined toward diesel over gasoline, it is also culturally and technologically inclined toward wood chips over other heating alternatives. In fact, Americans deploy very few CHP technoogies compared to the deployments in Europe.

Leo in Florida said...

Since 2005 Choren GmbH has been constructing a wood gassification to liquid fuels plant in Freiberg German (www.choren.com). They have patnered with Shell, Air Liquide (O2) and Lurgi (gassifiers), and BASF / Englehard. Both VW and Daimler have road tested the fuel called "Sun Diesel" straight up! Cycle time from wood chip to fuel drop is reported as 400 minutes. Fisher-Tropsch conversion of the syngas is well known science and currently practiced by Sasol in S. Africa (check stock SSL). I don't believe any enzymatic process will give the overall conversion rate,yield, and economics. I would invest in forest products before this makes the news.
LRB BSChemE, MBA

Fast Growing Trees said...

If only more people sat up and took notice of this energy option. Voices are continuously being raised about the importance of trees and their necessity for human survival these days. Unfortunately, they are just mere whispers in the breeze for all the reaction that actually needs to take place.
A commendable job you are doing ut here Scott. I wish you all the very best in your efforts.

Tim Hurst said...

This post is thorough and a valuable resource. And I will enjoy visiting again.

However, it strikes me that the first map of the US Patchwork of Renewables seems to 'miss the boat' on quite a bit of US renewable energy capacity. I know you cannot indicate the location of every source and generator of renewables in the country, but existing sources are considerably undervalued, especially in the upper midwest and mountain west (considerable wind, solar and geothermal resources).