Conservation of Feedstock Nutrients in Pyrolysis Biochars

Jatara Wise, PhD31-7-2012

Benefits of Bio-char• Sequester C in soil

• Increase Ca, Mg, P, and K

• Increase Fertilizer efficiency

• Decrease Al toxicity

• Increase Soil Water holding capacity

• Decrease Nitrous oxide emissions

• Reduce bulk density: Soil Dependent

Terra Preta Oxisol

Pyrolysis ReactorsFixed-bed (Auger-fed) Fluidized-bed

Source: Boateng et al, 2007

Slow Pyrolysis system layout

Why Nutrient Conservation?

• Give bio-char a value in fertilizer terms

• Improve soil conditions and crop production

• Sustainable conversion platform

Research Objective and HypothesesObjective• Evaluate the

conservation of feedstock nutrients, mass, and energy in co-products among feestocks using two different reactor designs.

Hypotheses• H0: The conservation

of nutrients, on a feedstock basis, does not depend on feedstock, pyrolysis conditions, or reactor design.

• Ha: There is some dependence.

Experimental DesignFixed-bed, slow pyrolysis• 4 Feedstocks

– Corn stover, Rice biomass, Switchgrass, and HES

• 2 Temperatures– 500 C, 600C

• 2 Flow rates– 1 Lpm, 2 Lpm

→ 4x2x2 Split-Split Factorial Design

→Focused on feedstock

Fluidized-bed, fast pyrolysis• 3 Feedstocks

– Corn, Switchgrass, and HES

• 1Temperature• 1 Flow rate

Fixed-bed, Slow Pyrolysis

Species P Std Dev K Std Dev Ca Std Dev Mg Std Dev

%

Bio-char co-product

Corn stover

49.9c† 20.5 30.1a 12.8 60.8a 26.7 61.5b 26.1

Switchgrass

159.8a 64.9 10.7c 2.8 67.0a 8.0 83.1a 20.1

HES 90.5b 20.3 4.8d 1.8 55.9a 12.6 38.3c 12.2

Rice stover

52.1c 3.4 18.4b 0.9 40.7b 2.8 45.1c 2.5

Conservation of bio-char nutrients

†P=0.05

Fluidized-bed, Fast Pyrolysis

Species P Std Dev K Std Dev Ca Std Dev Mg Std Dev

%

Bio-char co-product (Wyndmoor, PA)

Corn stover

65.4a† 16.8 53.1a 3.9 63.2a 10.6 57.8a 3.0

HES 56.5a 9.7 54.0a 8.3 57.9a 8.2 36.0b 5.3

Switchgrass

30.1b 6.7 8.9b 1.2 38.5b 5.8 14.3c 1.4

Conservation in bio-char and bio-oil

†P=0.05

Conclusions1. Feedstock dependence

– Switchgrass is different from HES, Corn stover, Rice Biomass2. Reactor design dependence

– Hence, conservation cannot be simply and arbitrarily assumed for a given feedstock or reactor design

3. Correlation to feedstock fiber properties (cellulose, hemicellulose, sugars, lignin)– Correlation analysis, MLR

4. Reactor design and construction may contaminate pyrolysis biochar resulting in elevated (>100%) conservations of select nutrients– Release of metal contaminants from tubing– Needs further investigation

5. Low conservation of feedstock K (both reactor designs)– Consistent with literature– Vaporization losses (Gaskin et al., 2007)– KCl and K2SO4 at temperatures above 500°C (Boman, 2005)

6. More complex thermo-chemical reactions– Inside reactor (labile fraction)

Acknowledgements• Committee members

– Don Vietor, PhD (Co-chair)– Tony Provin, PhD (Co-chair)– Sergio Capareda, PhD (member)– Clyde Munster, PhD (member)

• Funding Sources– USDA National Needs Fellowship– Sloan Fellowship– Hispanic Leaders in Agriculture and the Environment (HLAE)– Sun Grant North Central Region

• Group Members– Matt Keough– Derek Husmoen– Ronnie Schnell– Bill Allen