Conservation of Feedstock Nutrients in Pyrolysis Biochars

Jatara Wise, PhD 31-7-2012

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 Reactors Fixed-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 Hypotheses Objective

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

Hypotheses

• H 0 : The conservation of nutrients, on a feedstock basis, does not depend on feedstock, pyrolysis conditions, or reactor design.

• H a : There is some dependence.

Experimental Design Fixed-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

Conservation of bio-char nutrients

P Std Dev K Std Dev Ca Std Dev Mg % Corn stover 49.9c

† Switchgrass 159.8a

HES 90.5b

Rice stover 52.1c

20.5

64.9

20.3

3.4

30.1a

Bio-char co-product 12.8

60.8a

10.7c

4.8d

18.4b

2.8

1.8

0.9

67.0a

55.9a

40.7b

26.7

8.0

12.6

2.8

61.5b

83.1a

38.3c

45.1c

† P=0.05

Std Dev 26.1

20.1

12.2

2.5

Fluidized-bed, Fast Pyrolysis

Conservation in bio-char and bio-oil

Mg Species P Corn stover 65.4a

† HES 56.5a

Switchgrass 30.1b

Std Dev K Std Dev % Ca Std Dev 16.8

Bio-char co-product (Wyndmoor, PA) 53.1a

3.9

63.2a

10.6

9.7

6.7

54.0a

8.9b

8.3

1.2

57.9a

38.5b

8.2

5.8

57.8a

36.0b

14.3c

Std Dev 3.0

5.3

1.4

† P=0.05

1.

2.

3.

4.

Conclusions

– Feedstock dependence Switchgrass is different from HES, Corn stover, Rice Biomass – Reactor design dependence Hence, conservation cannot be simply and arbitrarily assumed for a given feedstock or reactor design – Correlation to feedstock fiber properties (cellulose, hemicellulose, sugars, lignin) Correlation analysis, MLR 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 K 2 SO 4 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