Michigan bioenergy crop comparison

Dennis Pennington<pennin34@msu.edu>, Michigan State University Extension - February 20, 2014

Explore the differences and compare the potential of each bioenergy crop.

Advancements in technology to convert biomass to biofuel, electricity or heat are driving up demand for a dedicated supply of biomass. The cellulosic ethanol industry is beginning to mature with several pilot scale facilities already operating and at least three commercial scale facilities scheduled to open in 2014. A tremendous amount of research has been conducted on a wide range of potential biomass crops. It is important to consider climate, topography, soil types, landowner objectives and potential yield when determining what type of biomass crop might fit a particular situation. It is also important to consider what type of technology is being used by a local bioenergy company. Different technologies favor different types of biomass.

To that end, the Michigan State University Extension On-Farm Bioenergy Research Trials were established in 2008 with three sites, but quickly expanded to 10 sites scattered across Michigan. Data from these plots have been compiled for the purpose of comparing the potential yield of each crop for biofuel and biopower (electricity or heat) purposes. Reported yield is an average of all site locations for all years, including the establishment years. For most of these crops, we compare four to six years of data. Conversion factors were drawn from various sources, but primarily from the National Renewable Energy Lab (NREL) Theoretical Ethanol Yield Calculator and Biomass Feedstock Composition and Property Database.

It is useful to evaluate and compare how each crop stacks up against each other. Some are perennial crops, others are annual crops. Some are woody crops, others are grass crops. Each crop has advantages and disadvantages, which is described in more detail at the Bioenergy Training Center, Unit BIOEN2. The crops listed in Table 1 are sorted by biofuel yield from highest to lowest. Note that there are three annual and two perennial crops in the top five. This could be important for newly established biomass conversion facilities, where they might convince a farmer to contract production for a year or two (annual crop) until they can build the acres of perennial crops.

Table 1. Energy potential and yields for various biomass crops grown in Michigan.

Biomass crop	Energy potential	Michigan
Annual (A) Perennial (P)	Biofuel / Biopower	Biomass yield (dry tons per acre)	Biofuel (gallons per acre)	Biopower (MMBTU/a)
Tropical maize (A)	Ethanol: 100 gal/ton⁴ Biopower**: 15.8 MMBTU/ton⁵	7.4	740	117
Sweet Sorghum (A)	Ethanol (from juice): 24-32 gal/ton¹ Ethanol (total plant): 130 gal/ton	6.9	607	NA
Giant Miscanthus (P)	Ethanol: 106 gal/ton^4,7Biopower**: 15.4 MMBTU/ton⁵	5.7	604	88
Sorghum (A)	Ethanol (forage sorghum): 88 gal/ton⁴	5.5	484	NA
Switchgrass (P)	Ethanol:104 gal/ton⁴ Biopower**:16.1 MMBTU/ton⁵	4.2	437	68
Willow (P)	Would be similar to poplar	4.0	420	68
Poplar (P)	Ethanol: 105 gal/ton⁴Biopower**: 16.9 MMBTU/ton⁵	4.0	420	68
Corn Grain (A)	Ethanol: 124 gal/ton⁴ Biopower**: 14 MMBTU/ton	131.0***	367	51
Corn Stover	Ethanol: 113 gal/ton⁴Biopower**: 15.7 MMBTU/ton⁵	3.1	350	49
Wheat Straw (A)	Ethanol: 96 gal/ton⁴Biopower**: 14.9 MMBTU/ton⁵	1.0	96	15

* Based on 91 gallon ethanol per ton
** Values are High Heating Values (HHV)
*** Bushels/acre
NA = not applicable. These crops would not be used for biopower.

It is important to note the yields of these crops are averages from these plots in Michigan. Consult your local MSU Extension office for support in determining the potential yields, advantages and disadvantages of each crop for your particular fields. More detail about climate, growing season, fertility, pest management and environmental concerns and benefits can be found in the Crop Comparison Matrix.

For more information, contact Dennis Pennington at pennin34@msu.edu or 269-838-8265.

References

Handbook of Bioenergy Crops, N. El Bassam
Farm-Scale Production Cost of Switchgrass for Biomass, BioEnergy Research
Net energy of cellulosic ethanol from switchgrass, Proceeding of the National Academy of Sciences of the United States of America.
Fractional yield and moisture of corn stover biomass produced in the northern U.S. corn belt, Biomass and Bioenergy
Hydrolysis of Miscanthus for bioethanol production using dilute acid presoaking combined with wet explosion pre-treatment and enzymatic treatment, Bioresource Technology
Factsheet/ Biomass: Miscanthus, Iowa State University Department of Agronomy

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).