Benefits for Depend on a for Plant Growth

Producing Total GHGs & Feedstock Tailpipe Fermen % Increase for Credit for Total GHGs & Source of (crude Emis- t-ation Without Plant % Savings for * or crop) Refining sions emissions Plant Credit Growth Biofuel

Gasoline +4.5 +8 +73.3 - 85.8 - 85.8

EU +61.2 Ethanol +40 +21.2 +71.4 +35.7 168.3 107.1 (+96%) (-29%)

Greenhouse gas emissions and sinks (CO2 eqv.) per mega joule of fuel (specific numbers from EU JRC) Effect of switching from to biofuels grown on otherwise unproductive – Reduced atmospheric CO2 through increased plant growth

emission emission Unproductive 2 2 land New crop growth CO CO

Car, gasoline

Car, ethanol uptake

2 Gasoline Use Ethanol Use CO

2 Figure 2 - Direct effect of switching from gasoline to biofuels that use existing crops – No change in emissions

emission emission

2 2 Crop growth Crop growth CO CO

Car, gasoline uptake

uptake 2 Car, ethanol Gasoline Use 2 CO

CO Ethanol Use

3 Potential -mediated sources of reduced or additional emissions

Crop growth on

emission

existing cropland 2 emission

with price-induced CO . 2 yield gain em CO emission

emission

2

2 2 Crop growth CO CO CO

Conversion to cropland

Car, gasoline & human Reduced respiration, Car, ethanol livestock and uptake

& human 2 uptake

respiration and 2 CO

wastes uptake

2 CO CO Gasoline Use Ethanol Use (vertical arrows indicate carbon uptake and emissions; italics indicates uptake or emission change due to biofuel) ) Benefit v. Cost of Using Land for Ethanol

Typical estimates of US High Yield Cellulosic Allowing “Surplus” Carbon cost of corn ethanol savings ethanol saving with Land to Regrow Forest converting existing without cost no land use cost and or Convert Tropical forest (1140 liters/hectare no net production Savannah after crediting by- emissions (17 t/ha & products) 100 gallons/t) ~1 ~3 >3 5.5 to ton tons of carbon tons of carbon >10 of carbon per per hectare per per tons of hectare/ year hectare/year carbon per = 34 g CO /MJ = 86 gCO /MJ 2 = 86 g CO2/MJ 2 hectare per year =158 to 287

gCO2/MJ

5 Solar conversion efficiencies

Iowa corn Ethanol , 0.125% Most optimistic location future US switchgrass (DOE) (24 tDM/ha and 100 gallons/tonne) 0.35%

Brazilian sugarcane ethanol , 0.2%

PV – 16% gross; 11% net