Title: Unit 8 Readings and Lecture
Course: BFM 201 Ethanol Production > Section: BFM 201 Ethanol Production

Unit 8 Readings and Lecture

To Do:
Read Textbook: Ethanol Process Fundamentals – Chapter 11 pages 11.1 – 11.13
Ethanol can be made from any carbohydrate source. These can be broken into three major sources: sugar, starch, and lignocellulosic. Typically, sugar and starch crops are also food crops. Lignocellulosic comes from non-food crops.

Sugar and starch crops are referred to as “first generation” crops for ethanol production.  Sugar crops would include crops such as sugar cane, sweet sorghum and sugar beets. Starch crops would include crops such as corn, wheat, grain sorghum, potato and cassava. In the Midwest, corn is king for ethanol production due to the large number of production acres and the well-established infrastructure built around corn production. In Brazil, sugar cane would be king due the large number of sugar cane production acres (hectares) grown there and in the tropics.

Cellulose-based crops are “second generation” crops for ethanol production. The future of ethanol is in the second generation crops because they come from non-food crops sourced from lignocellulosic biomass. There are two categories of lignocellulosic sources:

1. Waste materials, for example corn stover, other agriculture wastes, woody waste chippings,  forest residue, or even municipal solid waste (WSW).
2. Energy crops, for example short rotation woody crops (SRWC) or energy grasses like switchgrass. Typically, these sources can be grown on land not suited for food crops.
In the future, we will have “third generation” sources for ethanol production such as seaweed and other sources yet being discovered.

There are challenges to processing lignocellulosic sources into ethanol. Cellulose and lignin are strong, flexible and resistant to break down. They provide structure to plants. That is why plants stand tall and strong. Cellulose and lignin are hard to break down, and the processes involved are costly. Two processes currently being used are acid hydrolysis and enzymatic hydrolysis. New technologies are being sought to bring the costs down for the conversion processes involved in breaking down the cellulose and lignin. Other challenges for producing lignocellulosic sources are transportation and storage. Usually lignocellulosic sources are light and fluffy and not conducive to efficient transportation. Also, ethanol production facilities need to work out how to store these sources in such a way as to keep the facility running all year long. For example, stacks of corn stover may need to be stored in the field until needed. Another thing that must be sorted out is any specialized equipment that may be needed to harvest, store and transport the material.

Therefore, finding the ideal feedstock requires much due diligence to determine the cost benefit ratio. Some examples of questions the producer needs to consider are:

- Producers need to look at the alcohol per acre balanced with the cost per acre to grow the crop.
- Will the selected crop fit in with the producer’s current farming practices?
- Will it grow well on his or her land, in his or her geography and weather patterns?
- Will there be any additional water requirements?
- Are there any additional fertilizer requirements?
- Will new equipment need to be purchased?
- What co-products will be made and is there a market for them?

Fortunately, some alternative feedstocks thrive in arid areas or non-productive areas for food crops.

The two major ethanol production processes in the U.S. are dry milling and wet milling. In wet milling, the corn kernels are soaked in water or dilute acid to fractionate out the starch, gluten, protein, oil and fiber before the starch is converted to ethanol. This process tends to be a little more expensive. However the additional co-products mentioned might have a market price that offset the additional cost. For example, the corn gluten is a high value feed, but it cannot be hauled long distances so the market for this feed needs to be close by.  In dry milling, the corn is ground into meal without fractionation of the various parts. The co-product DDGS when dried to 10% moisture can be hauled long distances.
References:

Chapter 11 (2006). In Ethanol process fundamentals: An introduction to ethanol processing. Granite Falls, MN: Minnesota Energy Enterprise Center.

Blume, D., Fuller, R. B., & Winks, M. (2007). Chapter 6 and Chapter 8. In David Blume's Alcohol can be a gas!: Fueling an ethanol revolution for the 21st century. Santa Cruz, CA: International Institute for Ecological Agriculture.

Walker, G. M. (n.d.). Bioethanol: Science and technology of fuel alcohol. Bioethanol: Science and Technology of Fuel Alcohol. Retrieved from http://bookboon.com/en/bioethanol-science-and-technology-of-fuel-alcohol-ebook