Biomass Energy

Biomass offers tremendous opportunity as a major, near-term, carbon-neutral energy resource. Florida has more biomass resources than any other state, ~7% of the U.S. total. As such, harnessing these resources should be a key component of Florida’s energy strategy. Efficient biomass conversion depends on locally available resources due to high shipping costs of biomass. Cellulosic ethanol and gasification processes are just entering the early commercial phase and offer many opportunities for improvement. These improvements are directed at reducing capital costs and facilitating commercial deployment, thus creating new industry and new employment for Florida. Florida could produce over 8 billion gallons ethanol per year from Cellulosic Biomass (> 10 billion tons biomass/yr).image00212

Florida’s Inedible Biomass Feedstocks:

  • Municipal waste, green waste
  • Bagasse and sugarcane waste
  • Citrus pulp
  • Forest residues & thinnings
  • Invasive trees and plants
  • Animal waste
  • Agricultural residues
  • Energy crops from trees such as pines and hardwoods
  • Agricultural crops such as grasses, corn, sweet sorghum, and sweet potato.

 Florida

  • Consumes 8.6 billion gal/yr of gasoline
  • Consumption is growing by 300 million gal/yr
  • Depends almost exclusively on other states and nations for supplies of oil and gasoline

 Cellulosic Ethanol from Biomassimage0034

 Cellulosic ethanol is a biofuel produced from inedible parts (lignocellulose) of plants. Lignocellulose is composed mainly of cellulose, hemicellulose and lignin. Switchgrass, woodchips,  sweet sorghum, orange peels are some of the more popular cellulosic materials for ethanol production.  Cellulosic ethanol has the advantage of abundant and diverse raw material compared to sources like corn and cane sugars. 

 By using a variety of regional feedstocks for refining cellulosic ethanol, fuel can be produced in nearly every region of the country.  Though it requires a more complex refining process, cellulosic ethanol contains more net energy and results in lower greenhouse emissions than traditional corn-based ethanol.  E-85, an ethanol-fuel blend comprised of 85-percent ethanol, is already available in more than 1,000 fueling stations nationwide and can power millions of flexible fuel vehicles already on the roads.

1.3 Billion dry tons biomass/year produces 130 Billion gal of fuel ethanol or 1.0 Billion tons of chemicals or some combination.

 Dr. Lonnie Ingram, Distinguished Professor of microbiology at UF and member of the National Academy of Sciences, has spent the last two decades inventing and refining what many believe is the most promising approach yet to converting all that plant waste material into cellulosic ethanol.

“The net positive energy from cellulosic energy has been estimated by the Department of Energy at about 85 percent, with 15 percent to grow crops, transport and produce,” Ingram says. “Corn is the exact opposite, 15 percent positive energy compared to 85 percent to grow the corn.”

Cellulosic ethanol is chemically identical to corn ethanol and offers all of the same benefits – renewable, clean-burning – without the massive energy requirement and food competition. And Florida is the nation’s biomass giant.  Florida produces more biomass per year than any other state in the country.  Estimates are that as much as 10 billion gallons of ethanol a year from biomass resources could be produced in Florida, and much of that would be from material that is currently going to landfills, like yard waste.”

 Biofuel Pilot Plants at the University of Florida

image0045The Florida Legislature awarded UF $20 million for the construction of a fully integrated biofuels pilot plant to demonstrate the production of cellulosic ethanol.  The pilot plant will be used to develop and improve conversion processes and to assist industry in the validation and use of diverse Florida feedstocks.   The pilot plant is being built next to a leading specialty cellulose producer, Buckeye Technologies Inc. in Perry, Florida. The plant will be able to process 3 tons of sugarcane bagasse or 5 tons of wood products per day. It is expected to open at the start of 2012.

A biofuel pilot plant with 100 liters of ethanol/batch capacity was built in the Department of Agricultural and Biological Engineering as a part of the State’s Energy Center of Excellence and  located in Frazier-Rogers Hall on the UF main campus in Gainesville.  The Biofuel Pilot Plant serves as a platform to accelerate successful commercialization of bioethanol. The pilot plant is used to develop and improve production processes, test production feasibility from various plant substrates and residues available in Florida, and demonstrate all unit operations needed for commercialization.

 Ethanol from Corn

1.4 billion bushels of corn needed to produce 4 billion gallons of ethanol

14% of total corn production is used for ethanol production

3 plants are under construction in Florida using shipped corn

 Thermochemical conversion of biomass

Another approach to producing liquid fuels from biomass is via the thermochemical route. In this approach the biomass is first converted to syngas (a mixture of CO and H2) through a partial combustion process. The syngas can then be converted to a variety of chemicals and fuels using catalytic conversion processes.

Technology challenges in Thermochemical Conversion

Many of biomass products are rich in lignin and hence more suited to conversion via the thermochemical process as opposed to biochemical conversion. Unlike the thermochemical process, biochemical or fermentation processing of most cellulose biomass feed stocks have not yet been established. Additionally, thermochemical methods are faster and easier to control than biological methods.

In the thermochemical process, biomass feed stocks are first partially oxidized to form a mixture of carbon monoxide and hydrogen (syngas) and then converted to clean burning liquid hydrocarbon fuels ranging from ethanol, gasoline, kerosene, and diesel through JET A-1 or JP8 jet fuel. This is  accomplished via the well known and established Fischer-Tropsch synthesis (FTS) process developed in Germany in 1920s and commercialized in South Africa during the 70s.  The key technology development here is two-fold: (1) Tailoring the design of the gasifier to suit variety of biomass produced in Florida. This involves fine tuning of processing conditions (contact method, temperature, pressure, biomass to oxygen ratio etc.) to achieve optimum production of syngas while minimizing pollutant formation and maximizing energy production. (2) The design and optimization of the unique catalysts, reactors and processing conditions required for converting the syngas to meet the demands for a variety of liquid fuels.

The potential impact on agriculture and energy production in Florida are significant. The long term implications point to decreasing the dependence on imported oil and liquid fuels and the development of a flourishing renewable energy industry tailored specifically to take advantage of the unique biomass production and feedstock capacity available in US.

The conversion of low value biomass to high value clean burning liquid fuels such as gasoline or diesel has significant economic potential not just for Florida but for the nation as a whole. Florida has the unique advantage of being able to produce substantial amounts of biomass which can be considered as a renewable energy source with much less green house gas emissions associated with its use.

Besides growing the biomass, there are many existing additional sources that can be effectively utilized to make liquid fuels. These include: biomass produced from forest residues, municipal green waste, bagasse from the sugar cane industry, which is currently used as low grade fuel, agricultural residues such as citrus peels and animal waste. These materials are not convertible to ethanol using the conventional  fermentation techniques and hence their use does not compete with global food production. The limiting factor is that low cost conversion of such lingo-cellulosic material has not been demonstrated on a commercial scale. The variable nature of the biomass source and the distributed nature of the raw materials are factors that have prevented the commercialization of large scale facilities for biomass conversion.

 Table below gives the availability and prices of different biomass feed stocks that could be used for this technology:

Delivered Price

Urban Wood Waste

dry ton/yr

Mill Wastes

dry ton/yr

Forest Residue

dry ton/yr

Agricultural Residue

dry ton/yr

Switch grass

dry ton/yr

Cumulative

Dry ton/yr

<$20/ton

2,757,950

4,000

0

0

0

2,761,950

<$30/ton

4,596,584

1,412,000

515,000

0

0

6,523,584

<$40/ton

4,596,584

1,412,000

755,000

14,824

0

6,778,408

<$50/ton

4,596,584

2,678,000

975,700

14,824

1,268,290

9,533,398

 

For the first step of gasification of biomass, fluidized gasifiers are most commonly used. The gasification technology involves high temperature (600-900 oC). The syngas produced contains mostly H2, CO, CO2 and H2O but with tars, ammonia and particulates as impurities. The impurities are the primary barrier for direct use of the gas in Fischer-Tropsch Synthesis (FTS). Therefore technology to reduce the production of these impurities is critical to the success of this conversion process.

The investigators at USF has been studying this problem and developed some novel approaches to address this issue.  A novel  proposed process utilizes a breakthrough development resulting from many years of research. Essentially CaO is used as a catalyst and sorbent to promote the production of H2 while breaking up the tars and hence lowering particulate formation. This has been demonstrated on an experimental scale at the Clean Energy Research Center at USF. USF has also been studying the technology for FTS over the last 2 years on a grant funded by NASA. This work has resulted in the development of novel cobalt catalysts for FTS that were proven on bench scale reactors.

image002Figure on the left shows the effect of adding CaO to the feed. The tars are significantly reduced (on the sample on the right) in the condensate from the product gas when CaO is added to the feed.

 

Fischer-Tropsch Synthesis for production of liquids from biomass

image0037The general overall reaction paths include CO activation, CxHy hydrogenation, hydrocarbon coupling, and termination pathways as shown in Figure.  Over 45 years of outstanding research effort has helped to resolve many important issues concerning the overall reaction chemistry. This step is crucial since little is known about the liquefaction of biomass derived syngas in the literature.

image0046Figure on the right shows a sample of clean fuel produced from bench scale studies using CO and H2 mixtures using a Cobalt catalyst developed in the Clean Energy Research Center at USF.

The main deterrent for commercialization of biomass conversion processes is the cost of conversion. We will focus on developing maximum energy yield from select crops. By experimenting with different conversion techniques the yield and efficiency can be optimized while minimizing pollutant generation and energy consumption during the conversion process.  Please note that since all the carbon used in this process comes from Biomass the overall process is carbon neutral. Hence any additional capture of CO2 will contribute towards reducing global CO2 emissions. By combining high yield crops with a high efficiency conversion process this project has the potential to reduce the nation’s dependence on foreign oil. Water use is significantly less when compared to biochemical route to ethanol from biomass. Energy used is also less because the costly water separation step is avoided.