Bagasse is an abundant Florida biomass by-product of sugar extraction from sugarcane. Over a million tons of bagasse (dry basis) are annually produced by the Florida Sugar Industry and used as boiler fuel for steam and power cogeneration.

Bagasse can be converted to ethanol through a series of steps:

1. Pretreatment to make cellulose digestible and dissolve hemicellulose to sugars;

2. Enzymatic hydrolysis to break down cellulose into its constituent sugars;

3. Fermentation of all sugars to ethanol; and

4. Distillation of the fermentation broth to recover ethanol.

The key challenge to the successful commercialization of cellulosic ethanol technology, regardless of feedstock, is the efficient conversion of cellulose and hemicellulose to fermentable sugars during pretreatment.

The extent to which these polymers are successfully hydrolyzed defines more than 50% of the manufacturing cost of the produced ethanol. Although several pretreatment processes have been developed to date, none has been optimized for sugarcane bagasse because this feedstock, although abundant in Florida, is not as common in most of the country.

The project team will evaluate the most promising thermochemical and thermomechanical processes for bagasse pretreatement, and then scale up to pilot size the pretreatment that yielded the best lab results to confirm process scalability, generate samples for large-scale hydrolysis and fermentation work, and determine commercialization potential.

The project team’s evaluation will be based on a set of technical and financial criteria they have developed based on their collective experience with cellulosic ethanol processing:

• High sugar yield from hemicellulose;
• High cellulose digestibility;
• Avoidance of side-reactions;
• Minimal waste generation;
• Minimal capital and operating cost; and
• Process flexibility to accommodate additional Florida biomass species as supplements to bagasse, such as corn tops and trash, corn and sorghum stalks, and grasses.

The award was one of eight grants made by state through the Renewable Energy Technologies Grant Program established by the 2006 Florida Energy Act. The state received 74 grant applications for the program.

Resources:

• Assessment and Development of Pretreatment for Sugarcane Bagasse to Commercialize Cellulosic Ethanol Technology

• Florida Renewable Energy Technologies Grants Program

• Florida announces first winners of renewable energy grants