The Sustainability of Cellulosic Biofuels

The Biogeochemical Promise of Cellulosic LandscapesPhil Robertson Michigan State UniversityPhil Robertson, Michigan State University

Biodiversity Implications of Cellulosic LandscapesDoug Landis, Michigan State University

Economic Factors Affecting the Competitiveness of Cellulosic BiofuelsMadhu Khanna, University of Illinois

Cellulosic production systems offer significant promise for improving the environmental performancepromise for improving the environmental performance

of intensive agriculture - but it won’t “just happen”

Elements of Biofuel SustainabilityThe Sustainability of Cellulosic Biofuels

• EconomicProfitable

• EnvironmentalCarbon negative (climate stabilizing)Nutrient, water conservativeBiodiversity benefits

• SocialFood, energy securityRural community healthRural community health

High Diversity

The Sustainability of Cellulosic Biofuels

A diversity of production systems

High Diversity, Low Input

Natural grassland

Poplar trees

Switchgrass

Poplar trees

Miscanthus

Low Diversity

Corn

Low Diversity, High Input

C b N t lit d E R t I t t

The Sustainability of Cellulosic Biofuels

Carbon Neutrality and Energy Return on Investment

Energy invested vs. energy returned….

Crop Net Energy YieldCorn grain ethanol 1 4Corn grain ethanol 1.4Soy biodiesel 3.4Cellulose ethanol 10Cellulose ethanol 10Sugarcane ethanol 15

Directly related to carbon neutrality….

Sources of Carbon Cost in Field Crop

The Sustainability of Cellulosic Biofuels

Sources of Carbon Cost in Field Crop Ecosystems

• Soil carbon change• Fuel use• Nitrogen fertilizer• Lime (carbonate) inputs• Lime (carbonate) inputs• Nitrous oxide flux• Methane flux (oxidation &

emission)

The Sustainability of Cellulosic Biofuels

Carbon Costs of Field Crop Activities at KBS

Soil Carbon Fuel

N-Fertil. Lime N2O CH4 Net

Corn-Soy-Wheat 0 16 27 23 52 -4 114

Poplar trees -117 2 5 0 10 -5 -105

Native grasses -220 2 0 0 15 -6 -211Native grasses -220 2 0 0 15 -6 -211

All units are g CO2-equivalents / m2 / y

Source: Robertson et al. Science (2000); unpubl.

Air Quality: Nitrous OxideThe Sustainability of Cellulosic Biofuels

y

IndustryGlobal Anthropogenic Sources

y

Agriculture

Total Annual Impact 1 2 Pg C i (compare to fossil fuel loading = 4 1 Pg C)Total Annual Impact 1.2 Pg Cequiv (compare to fossil fuel loading 4.1 Pg C)

Source IPCC 2001, 2007; Robertson 2004

Nitrous Oxide Fluxes at KBS

The Sustainability of Cellulosic Biofuels

Grain Crops

Nitrous Oxide Fluxes at KBS (1992-2007)

p

Cellulosic CropsCe u os c C ops

Source: Robertson et al. 2000 Science; Grandy et al. 2006 JEQ; and in prep.

Water Quality

The Sustainability of Cellulosic Biofuels

Q y

Perenniality confers lower

• Soil erosion

Perenniality confers lower

• Phosphorus runoff

• Nitrate loss to ground &f tsurface waters

www.nature.org

Nitrate Loss at KBS (1996-2007)

The Sustainability of Cellulosic Biofuels

Grain Crops

Cellulosic Crops

Source: Parr, Basso, Hamilton, Robertson in prep.

Conclusions: The Biogeochemical Promise

The Sustainability of Cellulosic Biofuels

Cellulosic biofuel systems offer improved• CO2 mitigation (high energy return, little or no carbon

d bt)debt)• Water quality (e.g. nitrate conservation)• Air quality (e.g. nitrous oxide abatement)

But not guaranteed; will depend on• Choice of crops (e.g. annual vs. perennial)

M t ti ( id t h t• Management practices (e.g. residue return, harvesttiming and intensity, fertilization rate, irrigation)

• Location (prior crop history)(p p y)