Grass-4-Fuel

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At this time, we have successfully and are working to:

1. Convert Switchgrass, Soybean stalks, and Corn Stalks to sugar (precursor to alcohol/ethanol) on a laboratory scale
2. Trying varying means of pretreatment, hydrolysis, and fermentation. 
3. Grown Switch grass
4. Produce Cellulase enzymes
5. Converted resulting sugars to alcohol

Up until recently we executed each step on its own, however now we’re working to test combining steps in an effort to save time, cost, reduce complexity, and most importantly to see if this front end process to producing cellulosic ethanol could effectively be executed in an ensiled environment for SSF (simultaneous saccharification and fermentation) or CBP (Consolidated Bioprocessing) locally on the farm.  Reasons for doing so are that current traditional process (listed below) is costly and complex. To be more competitive, Cellulosic Ethanol production needs to become cheaper and/or more simplified. Here we’re working towards both with the consequence being we might not produce as much per unit initially, but can produce enough to combine with reuse of substrates to make other bioproducts for heat & power production.
 

The underlying goal of this work is to understand the process and identify feasibility for establishing this process on a residential and community basis, where centralized processing could be set up to utilize both dedicated energy crops and agricultural left overs to produce ethanol and other products that could serve as income and energy sources for local farms and a local community.
 

Click here to view details describing how Cellulosic Ethanol fits into the overall concept of Energy Farming, where energy is farmed at a given location from available resources such as solar, wind, geothermal, and biofuels, and from this concept, jobs and revenue can be created for a community

What is Cellulosic Ethanol

Cellulosic Ethanol is fuel that is produced from the cellulose in plants & biomass, as opposed to traditional ethanol that is produced from the starch or from sugarcane.  The process to make ethanol from Switchgrass and from other biomass begins different than that for ethanol from corn, since deriving sugars from lignocellulosic sources such as Switchgrass is more complicated than the same process for corn, as detailed further below.
 

Lignocellulosic substrates are made up of cellulose, hemicelluloses, and lignin, each of which need to be made available to the next step in the process called Hydrolysis before any fermentation to alcohol can begin. In order to make cellulose, hemicelluloses, and lignin available, each is broken down by a variety of Pretreatment methods. Once this is done, the next step (Hydrolysis step) converts exposed cellulose into simple sugars (namely hexose (C6) and pentose (C5) sugars) so that each can then be fermented into alcohol. After Hydrolysis, the last two processing steps are typical to the brewing process, where the results of Pretreatment and Hydrolysis are first fermented into a wort (beer), and then distilled into alcohol.
 

• Harvesting
As detailed on the Switchgrass trials page, we are currently growing Switchgrass in Hammond NY, and also have Reed Canary Grass growing as well as sweetcorn.  For these home trials, I have chopped the grasses and corn stalks and then sent the resulting forage through the hammer mill for fine processing & breakdown of the material. 

• Pretreatment (Traditional Process)
The hammered feedstocks were then mixed with hydrated lime and placed in covered barrels & other containers for several months, this to simulate an ensiled environment. 

• Hydrolysis (Traditional Process)
Here the pretreated substrate was mixed with distilled water, pH and temperature stabilized, and then a Cellulase enzyme was added. Using the hydrolysis set up shown in the gallery below, hydrolysis (agitation, combined with keeping the temperature/hotplate at 50 - 55 degrees Celcius, and PH as close to 5.0 as possible) was conducted for about 24 hours in each case so that the enzymes could do their work and convert exposed cellulose to sugars. During and after the hydrolysis I used a diabetes BG meter to successfully measure the presence of sugar in the slurry.

• Fermentation (Traditional Process)
To ferment the Hydrolyzed Switchgrass, corn stalks, and soybean stalks, I used a standard homebrew (for beer) fermentation bucket with CO2 trap. Resulting alcohol readings are shown in the gallery below.

• Distillation
Distillation of the fermented worts is done using an electric hot plate (for better temperature control) and a standard distillation column that is used in homebrewing of beer.

• Processing Left Overs
Both traditional and SSF/CBP Process above result in left over solids once fermentation is complete.  To make best use of the same crop (part of ‘energy farming’ concept) I will work soon to efficiently dry these solids so that they can then be densified into pellets for use in heating our ho

Advantages of producing Cellulosic Ethanol from biomass:
▪  It is said that greenhouse gas emission are reduced by 80% over gasoline, vs. 20-30% at best for corn
▪  Many cellulosic sources such as Switchgrass and Reed Canary Grass do not have to be planted every year - meaning energy does not need to be spent on tilling and planting
▪  Cellulosic sources have a strong, anchoring root system that minimize erosion.
▪  Cellulosic sources do not require large amounts of water or pesticides
▪  Biofuels such as those derived from Switchgrass, Reed Canary Grass, and other Cellulosic sources  can be used in most modern engines with minimal adjustment to the engine
▪  The net energy gain from Cellulosic Ethanol is far greater than that from corn ethanol
▪  Ethanol yield per acre is greater that from corn based ethanol
▪  Less fertilizer, herbicides, & chemicals are required for grass based ethanol than for corn
▪  Emissions are lower in sulfur and mercury
▪  When using Switchgrass as a feedstock, one acre of Switchgrass has the energy equivalent of 2-6 tons of coal
▪  In 2005 the USDA estimated that about 30 percent of US oil consumption could be replaced by Switchgrass and other cellulosic biofuels, and the USDA also stated that this method would not cut into the production of our food supplies.

Traditional Cellulosic Ethanol enzymatic process:
1. Pretreatment - This step separates the biomass and its components by disrupting the sheath found around the biomass material. The reason for this is to expose the plants Cellulose for Hydrolysis and to make the most surface area possible available to enzymes or chemicals in the Hydrolysis step.
 

Pretreatment is typically accomplished via one of or a combination of the following means:
     ▪  Physical milling (milling)
     ▪  Thermo physical (steam)
     ▪  Chemical (acids, ect)
     ▪  Biological (microbes)
 

2. Hydrolysis - Hydrolysis converts the complex carbohydrates of the biomass to fermentable sugars - specifically, it breaks down the plants Hemicellulose to its C5 sugars (xylose, mannose, arabinose and galactose) and Cellulose to its C6 sugars. This conversion is accomplished via several of methods, where the choice of method typically is biological or chemical in nature. Examples are:
 

Chemical (Acid) Hydrolysis
     1) Dilute Acid
     2) Concentrated Acid
 

Enzymatic Hydrolysis
In this process, enzymes are used to hydrolyze the cellulose (C6 Sugar) and hemicellulose (C5 sugars).  The list of enzymes that have been tried and can be used is extensive. Examples of this list are contained in a list of patents & applications for cellulase and hemicellulase enzymes & technologies that are listed on pages 77-79 in David M. Mousdale's book. In this list, over 30 patents and patent applications are listed for Cellulase Enzymology, a dozen for Hemicellulases, and several patents and patent applications are listed for Hemicellulase Enzymology. Many of these are found on forest floors and some are classified are used for degrading lignin (David M. Mousdale's book, pages 78 & 81) .
 

Some examples of Cellulase and Hemicellulase are:
 

     Cellulase:
               ▪  Trichoderma reesei - produces cellulase enzymes
               ▪  Bacteria
               ▪  Insects
               ▪  Plants
 

     Hemicellulase:
               ▪  Bacteria
               ▪  Yeasts and Fungi
               ▪  Marine Algae
               ▪  Wood-digesting insects
               ▪  Higher Plants (in germinating seeds)
 

3. Fermentation - Sugars are converted to alcohol and water. Yeast is added to facilitate this  process.

4. Distillation - The water and alcohol are separated at this step

5. Byproduct and Residue Processing – Fermentation puts off CO2 that can be captured & sold, and I’d also like to utilize from home trials, results of drying & densifying left over solids for use as a heat and fuel source for electrical generation (via gasification) for the cellulosic ethanol production process, and for producing pellets & briquettes for sale to home owners as a heat source.

Traditional Corn ethanol process steps:

1. Milling - corn is first ground into flour (meal) and then water, enzymes, and ammonia are added to form a mash. Enzymes are required to convert the starch to a simple sugar (dextrose) and ammonia is added for pH control and as a nutrient for the yeast
2. Cooking - this step is performed to reduce bacteria levels prior to fermentation
3. Fermentation - Sugars are converted to alcohol and water. Yeast is added to facilitate this process.
4. Distillation - The water and alcohol are separated at this step
5. Byproduct and Residue Processing - This final step involves processing the leftovers from the  process - typically called distillers grain.

Resources:
Organizations working to advance the production and use of grass biofuels:
• Association of Warm Season Grass Producers: https://www.awsgp.org/
• Cornell University: http://forages.org/index.php/grass-biofuels
• Ontario Biomass Producers Co-Operative: www.ontariobiomassproducersgroup.wildapricot.org/
• Grass Energy Google Forum: https://groups.google.com/forum/#!forum/Grass-Energy

Companies who currently produce Enzymes for this process are:
▪  Iogen - http://www.iogen.ca/
▪  Genecor - http://www.genencor.com/wps/wcm/connect/genencor/genencor
▪  Novozymes - http://www.novozymes.com/
▪  Dyadic International Inc - http://www.dyadic.com/wt/home
▪  Verenium - http://www.verenium.com/

Sample Processes
1) The following url shows a process diagram and also speaks to the benefits of Cellulosic Ethanol:  
http://zfacts.com/p/85.html
 

2) The Iogen Process, as summarized on pages 157-168 of David M. Mousdale's book, uses:
Feedstock: Wheat Straw
Pretreatment: A dilute Acid and heat pretreatment via high pressure steam
Hydrolysis: Separate Cellulose Hydrolysis and Fermentation
Fermentation: Saccharomyces yeast
 

3) A good description of the complete process is also detailed at:  
 http://science.howstuffworks.com/environmental/green-tech/energy-production/cellulosic-ethanol2.htm
 

4) The complete Wikipedia description of the process is found at:  
 http://en.wikipedia.org/wiki/Cellulosic_ethanol