Harvest strategies for future bioenergy switchgrass crops

Michigan farmers should consider switchgrass production as a potential economic and sustainable option for their future.

As energy demands in the United States continue to grow and available fossil fuels (coal, oil and natural gas) decline, the pursuit of developing and utilizing alternative sources of reliable and renewable energy will become increasingly critical to our country’s energy policy. Ethanol is one of the most popular renewable sources of energy to substitute for liquid fossil fuels. To date, bioethanol fuel has predominately been made from fermentation of corn grain. However, scientific research is now focusing on developing energy efficient and sustainable systems that will process various forms of plant material (biomass) into ethanol.

Cellulose and hemicellulose, two types of complex plant carbohydrates, make up the majority of usable plant biomass. Most current research is centered on deconstructing these complex biomass carbohydrates into readily fermentable carbohydrate components, primarily glucose and xylose. This type of fermentation will produce ethanol derived from the plant’s cellulosic components, hence the name cellulosic ethanol.

Switchgrass (Panicum virgatum) is one of the most popular biomass feedstock candidates for future cellulosic ethanol production. Michigan is highly suitable for switchgrass production for a number of reasons.

  • Switch is fast growing, has a long growing season and will produce quality biomass for 10-plus years.
  • Grows well on marginal lands and nutrient depleted crop fields.
  • It is water efficient, drought resistant and helps boost soil organic matter.
  • It is a perennial crop, requires less fertilization and herbicide inputs than annual grasses, and does not require specialized harvesting equipment.
  • Native to Michigan and has natural resilience to Michigan’s climate, pests and diseases.

However, switchgrass production also has its drawbacks and risks.

  • Requires a minimum of two growing seasons to establish peak biomass production.
  • It’s currently an undervalued feedstock in a volatile or non-existent market.
  • Currently doesn’t have governmental incentives or subsidies.
  • Still requires more research in establishing sustainable farming management techniques.

To address the last drawback point of switchgrass production, Michigan State University is leading research in developing sustainable agricultural management techniques for switchgrass production in the Great Lakes region. Part of maximizing cellulosic ethanol production is maximizing the amount of biomass harvested. Two of the most important aspects in biomass harvest maximization are the timing of harvest and the collection method utilized. Current research has included both a conventional bale technique and a direct chop-and-ensile technique during four specifically chosen harvest timings. Preliminary research suggests that the direct-chop harvest technique may result in higher biomass yields over a traditional bale technique and may be more sustainably advantageous in terms of energy use.

Currently, there is still much research to be done in order to make cellulosic ethanol production an economically and environmentally sustainable liquid fuel production system in the future. However, Michigan farmers today should start to consider if switchgrass production is a potential economic and sustainable option for their future.

See demonstrations and talk with researchers about corn residue management and bioenergy production at the Bioenergy, Cover Crop and Corn Residue Management field day October 4 from 1 to 5 p.m. at the St. Johns Bioenergy Research Farm. Equipment demonstrations including vertical tillage, chopping corn heads, corn stover harvest and cover crop establishment with slurry manure seeding will be conducted. The farm is located on Scott Road, just north of M-21 in St. Johns, Mich. (view map).

The field day is hosted by Michigan State University Extension and sponsored by the Michigan Soybean Checkoff program.

Dr. Thelen's work is funded in part by MSU's AgBioResearch.

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