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University of Minnesota Biomass

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Hello Casey,

Sorry it has taken me so long to get back to you. I sent your questions around to some of the other researchers I work with. Prof. Vance Morey and Dr. Nalladurai Kaliyan have been doing a lot of work on biomass densification here at the UofMN
Here are some answers to your questions:

what does HHV stand for? I am trying to figure out what is the yearly input in tons of biomass needed to just fuel the heat needs of a plant?

HHV stands for Higher Heating Value which is the amount of heat released during combustion. See this link for more detail: http://en.wikipedia.org/wiki/Heat_of_combustion
You can find a graph showing the amount of biomass fuel needed to supply the heat needs of a 50 million gallon per year dry grind ethanol plant in the ASABE paper I have attached. If you use only corn stover it is about 400 tons (363 metric tonnes) per day

When you all are looking at this study do you envision bales being stored at the field through out the year and a fleet of trucks will delivery them to the ethanol plant at the time they are needed rather than bulk storing at the ethanol plant?

We assumed that the biomass would be densified into pellets or briquettes at a facility separate from the ethanol plant. The ethanol plant would have enough storage to hold about a weeks worth of densified biomass fuel.

Densification, is grinding the way to go with that in order to keep transportation costs lower or can you just delivery bales to the plant where you have a stationary grinder on site?

A response from Prof. Morey:
Grinding is a preliminary step in densification. Grinding probably leads to lower bulk density than bales in the first step. That is something we are working on. I not a big fan of moving a pelleting or briquetting device to the site of the bales to make the pellets or briquettes. I think there is an intermediate stage of grinding followed by compacting the material at the local site, but not forming briquettes, in order to transport to a central facility for making the briquettes. I think this will be operated like a separate business even if it owned by the same people who own the ethanol plant.
He asked the question that a lot of people ask which is if you get the bales delivered to the ethanol plant why do you need to densify. I think we will find that feeding densified material (pellets or briquettes) in to the combustor or gasifier will be important to have predictable performance at the plant. The cost reductions resulting from predictable performance will justify the densification cost. We still need to do the analysis to see if this turns out to be true.

Pellets? Do they add another unnessecary step in this process? Could you turn the biomass to pellets in order to store in a silo on site using the bulk delivery to the site scenario?

Portable pelleting operation, what do you think of a semi trailer with a pelleting system built on it to grind and pellet at the feedstock location and you delivery pellets instead of ground biomass?

This is going to require a lot of trucks and baling equipment, do you see an opportunity for a contract company to provide these services to an ethanol plant. Essentially creating a partnership where a secondary company sources feedstock to the plant and the plant makes the investment in the gasification equipment. Or do you see the ethanol company trying to take on this whole process?

We assume it will be a contracted company, but the ethanol plant will be very closely involved.

Let’s say you are trying to meet the needs of a 50 million gallon facility, what is the radius in miles of the plant that you would need to collect from. I understand this will be based on a % of land you are harvesting off.

This depends on how much biomass farmers are willing to take off their land each year.
Lets say the plant is surrounded by corn fields. The corn yield is 150 bushels/acre, half the above ground weight of the corn plant represents grain, the other half is corn stover. If the farmer is willing to take off 50% of the corn stover each year you would have about 2.1 tons per acre available. The plant needs 132,000 tons per year. So you need about 63,000 acres to draw from. If the area is pure corn ground the radius would be 5.6 miles.

Thanks for taking the time to reply


Written by Casey McConnell

April 29, 2008 at 2:48 am

Posted in Bioenergy

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