Cellulosic Feedstocks for Bioenergy in Florida: Perennial Grasses

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Cellulosic Feedstocks for Bioenergy in Florida
Perennial Grasses

• Lynn Sollenberger and Zane Helsel
• University of Florida/IFAS and Rutgers University

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Objectives

• Discuss the merits of grasses for bioenergy
• Describe six candidate grasses for use as
  cellulosic feedstock in Florida
• Discuss adaptation and issues regarding
  establishment, production, and production
  constraints for each grass

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Introduction

• Why cellulosics?
• Can be grown on marginal land not suited for row
  crops
• Production does not divert food crops to energy
  use
• Florida climate well suited for biomass production

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Introduction

• Why perennial grasses?
• Establish quickly and produce an annual harvest
• Rapid growth, greater efficiency of water and
  nitrogen use (most are C4 plants) than
  broadleaf/woody plants
• Do not need to be planted each year
• Ecosystem services

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Ecosystem Services of Grasses
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Introduction

• Ecosystem Services
• Carbon (C) sequestration
• Perennial grasslands deposit large amounts of C
  in the rooting zone (Miscanthus sequestered 4
  tons soil C/acre in 15 yr)
• 22 of total global soil organic C resides under
  grasslands!!

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Ecosystem Services

• Water quality
• Water capture, minimizing particulate flow to
  surface water
• Filtration, removing potential pollutants from
  shallow ground water
• Reduce likelihood of ground water contamination
  from dairy or industrial effluent irrigation

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Ecosystem Services

• Soil quality
• Reduce soil erosion, increase water infiltration
  and preserve topsoil
• Increase soil fauna, soil C, and soil moisture

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The Grasses

• Elephantgrass
• Energycane
• Erianthus

• Giant Reed
• Miscanthus
• Switchgrass

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Approach

• Individually introduce the six grasses and their
  general characteristics
• Collectively compare and contrast their
  adaptation, establishment, and harvest management

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Elephantgrass/Napiergrass Pennisetum purpureum

• C4 perennial

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Elephantgrass - Characteristics

• Can grow to 18-feet tall
• Has thick, fleshy rhizomes that do not move
  laterally beyond the bunch
• Seeds are small and quickly lose viability, so
  propagated using above-ground stems
• Named varieties exist and have been tested

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Elephantgrass Constraints to Use

• Vegetative establishment
• Currently listed on the IFAS do not plant list
  for South Florida (not clear if improved types
  have invasive potential can be managed to avoid
  any chance of spread)

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Energycane Saccharum spp.

• C4 perennial

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Energycane - Characteristics

• Energycane - Saccharum hybrids selected to
  produce high amounts of cell wall biomass rather
  than sucrose.
• L79-1002 is a productive, cold tolerant
  energycane hybrid (commercial sugarcane X wild
  Saccharum from Argentina) tested extensively in
  Florida others currently being tested in S.
  Florida

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Energycane Constraints to Use

• Vegetative establishment
• Some types (not L79-1002) are less cold tolerant
  than elephantgrass and somewhat less productive

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Erianthus - Erianthus arundinaceum

• C4 perennial grass

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Erianthus - Characteristics

• Up to 18-feet tall deep rooted growth early in
  spring semi-erect growth habit
• Close relative to sugarcane source of cold
  tolerance in sugarcane breeding programs no
  named varieties
• Propagated by rooted crowns or above-ground stems

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Erianthus Constraints to Use

• Vegetatively established
• Sometimes more difficult to establish with stem
  cuttings than elephantgrass or sugarcane
• Semi-erect growth habit can leads to lodging and
  difficulty harvesting mature biomass

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Giant reed - Arundo donax

• C3 perennial, also called Spanish cane, wild cane
  or giant cane

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Giant reed - Characteristics

• 12-16 feet tall, can grow up to 20 feet
• Strongly rhizomatous,
• forms spreading mat

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Giant reed - Characteristics

• 12-16 feet tall, can grow up to 20 feet
• Strongly rhizomatous, forms spreading mat
• Seed rarely viable, propagated by rhizomes,
  above-ground stems, or tissue culture propagules
• No named varieties

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Giant reed Constraints to Use

• Considered a major invasive weed in CA and TX
  watersheds can be managed in production fields
• Rhizomes are vigorous and hard to kill movement
  of soil containing rhizomes results in spread
• Most likely to be a problem when planted areas
  are being converted to other purposes

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Miscanthus Miscanthus X giganteus

• C4 perennial grass sometimes confused with
  elephantgrass or called E-grass

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Miscanthus - Characteristics

• Mature height - 12 feet tall
• Sterile hybrid, propagated only by rhizomes slow
  to establish (not invasive)
• Of interest in Europe because of annual harvests
  and low moisture and minerals if spring harvested
  (after winter dry down)

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Miscanthus Constraints to Use

• No existing varieties selected for FL conditions
• Vegetatively propagated using rhizomes
• Lower yielding (??) than most other candidate
  grasses

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Switchgrass Panicum virgatum

• C4 perennial grass

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Switchgrass - Characteristics

• Can grow to 6 feet tall
• Is a bunch grass but it has short rhizomes and a
  deep root system
• Seed propagated
• Alamo is the best adapted variety for Florida
  (developed from a native Texas population)

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Switchgrass Constraints to Use

• Slow establishment, lower yielding
• Rust (fungus) and dry down are problems in humid
  climate
• FL is at the edge of zone of adaptation
• Less known about switchgrass in FL than crops
  like elephantgrass, energycane, sweet sorghum,
  sugarcane, etc.

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Environmental Adaptation
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Planting Practices
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Harvest Management/Yield
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Biomass Energy from Perennial Grasses

• Advantages
• Energy positive (captures solar energy)
• Comparatively more efficient use of inputs on
  marginal land
• Relatively low maintenance once established
• Ecosystem services (water, soil, wildlife, C
  sequestration, low pollutants)

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Biomass Energy from Perennial Grasses

• Challenges
• Expensive to establish require nutrients/water
  for production
• Low energy density (1/3 to ½ that of coal on a
  dry basis)
• Transportation, handling, and water (All biomass
  is local)
• Lack of improved varieties and limited knowledge
  of management in some cases

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Questions
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Other References

• Elephantgrass - http//edis.ifas.ufl.edu/AG302
  Biomass and Bioenergy 53-21.
• Energycane - http//edis.ifas.ufl.edu/AG303
• Erianthus http//edis.ifas.ufl.edu/EH213
• Giant Reed http//edis.ifas.ufl.edu/AG307
• Miscanthus Global Change Biology 132296-2307.
• Switchgrass - http//edis.ifas.ufl.edu/AG296