Nutrient Recovery from Pyrolysis Systems
Jatara Wise1, Don Vietor1, Sergio Capareda2, Tony Provin1, Derek Husmoen1, Matthew Keough1, Clyde Munster2, & Akwasi Boateng3
(1) Soil & Crop Sciences, (2) Biological & Agricultural Engineering, College Station, TX, (3) USDA-ERRC,Wyndmoor, PA
Results
Abstract
Bioenergy crops such as high-energy sorghum (HES),
bioenergy rice, corn stover, and switchgrass can be thermochemically converted by pyrolysis to produce bio-oil,
synthesis gas from non-condensable gases, and bio-char. The
bio-char fraction can be recycled back to the production field
to improve soil physical qualities and nutrient status. While
various publications have demonstrated the beneficial effect of
pyrolysis bio-char on soil physical properties, there has been
limited data published on the recovery of mineral nutrients
from pyrolysis co-products. This work quantified the recovery
of nutrients (P, K, Ca, and Mg) in pyrolysis co-products from
various feedstocks using two distinct reactors. Nutrient mass
balances, on a biomass basis, were calculated to estimate
nutrient recovery efficiencies. The results revealed P
recoveries of 93% (fixed-bed reactor) and 58% (fluidized-bed
reactor) for pyrolyzed HES. Recoveries for K, Ca, and Mg
varied among feedstocks and between reactor types,
suggesting nutrient recovery is dependant on both feedstock
characteristics and reactor type.
Materials and Methods
1) All feedstocks (corn stover, switchgrass, HES, and rice stover) were
analyzed for nutrients using a sulfuric acid digestion.
2)Corn stover, rice stover and HES was pyrolyzed using laboratory scale
fixed-bed reactor.
• Bio-char was analyzed for nutrients using sulfuric acid digestion.
• Bio-oil was ashed and prepared and analyzed for nutrients using
Inductively Coupled Plasma Spectroscopy (ICP).
• Non-condensable gas nutrient concentrations were analyzed using
Inductively Coupled Plasma Spectroscopy (ICP).
3)Corn stover, switchgrass, HES was pyrolyzed using a state-of-the-art
fluidized-bed, fast pyrolysis reactor.
• Bio-char was analyzed for nutrients using sulfuric acid digestion.
• Bio-oil was ashed and prepared and analyzed for nutrients using
Inductively Coupled Plasma Spectroscopy (ICP).
• Nutrient concentrations in non-condensable gases were not measured.
•
•
•
•
Pyrolysis is the thermo-chemical decomposition of
biomass at high temperatures in the absence of oxygen.
Pyrolysis is a preferable renewable energy conversion
process due to its short conversion time and small scale
and mobile units could potentially reduce transport and
handling costs.
Species
%P
Std Dev
%Mg
Std Dev
30.25a
12.77
63.18a
26.62
63.30a
25.42
HES
93.63a
20.00
5.02c
1.75
68.89a
11.33
44.04b
13.12
Rice
52.22b
3.36
18.57b
0.96
45.63b
5.68
47.61b
3.17
† Numbers followed by the same letter within column were not statistically different
(P=0.05).
Table 2. Mean percent recovery of total feedstock P, K, Ca, and Mg in
pyrolysis co-products from fluidized-bed, fast pyrolysis.
Species
%P
Std Dev
Corn
70.78a†
14.81
55.13a
3.25
HES
Switch
grass
58.55a
8.45
54.81a
35.54b
35.54
10.99b
%K
Std Dev
% Ca
Bio-char and bio-oil combined
Std Dev
%Mg
Std Dev
68.47a
17.67
65.54a
7.1
8.04
60.15a
4.72
39.26b
3.55
1.72
44.58b
5.66
21.98c
0.97
Discussion and Conclusion
•
•
Figure 1. Schematic diagram for laboratory scale fixed-bed reactor.
Bio-char can be re-applied back to the production fields
to:
•
Supply organic carbon for sequestration
Replenish soil essential mineral nutrients
The recovery of feedstock P from corn and rice stover and HES coproducts was relatively high and similar to previous reports for slow
and fast pyrolysis of corn stover biomass (Husmoen, 2011, Mullen et al.,
2009) (Table 1).
However, the recovery of feedstock K from slow pyrolysis of corn stover,
HES, and rice straw were seemingly low compared to previous reports
of corn stover (Table 1) (Husmoen, 2011, Mullen et al., 2009, Schnell et
al., 2011).
P and K recoveries were also low when compared the fluidized-bed
pyrolysis of fresh and stored swithcgrass biomass (Agblevor et al.,
1995).
Relatively low K recoveries in co-products of corn stover and HES for
slow- compared to fast-pyrolysis indicated reactor type or conditions
could affect nutrient recovery (Tables 1 and 2).
Additionally, variation among species between reactor types indicated
interactions between biomass source and reactor type could affect
nutrient recovery and efficiencies of recycling through bio-char.
Conclusion
•
Hypothesis and Objectives
H0 : Variation of biomass species and reactor type have no
effect on the percent recovery of mineral nutrients.
The objectives of this study were to:
 Quantify the recovery of feedstock nutrients (P, K,
Ca, and Mg) from pyrolysis co-products from
various feedstocks using two distinct reactors.
 Evaluate if pyrolysis bio-char is suitable for
recycling plant essential nutrients back to the soil.
% Ca
20.54
•
•
Std Dev
50.09b†
The crops analyzed in this study are high-energy sorghum
(HES), switchgrass, corn stover, rice stover.
Ha : There is some effect.
%K
Corn
•
•
Std Dev
Co-products combined
It is believed that the majority of mineral nutrients reside
in the bio-char (Coleman et al., 2010).


•
pyrolysis co-products from fixed-bed, slow pyrolysis.
† Numbers followed by the same letter within column were not statistically different
(P=0.05).
Introduction
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Table 1. Mean percent recovery of total feedstock P, K, Ca, and Mg in
•
•
Recovery of feedstock nutrients varies amongst species, but
species ranking differed among reactor type.
Nutrient recoveries among combinations of feedstock source
and reactor types differed among P, K, and Mg.
Additional research is needed to evaluate factors contributing to
recovery differences between nutrients and reactor types and
feedstocks.
Acknowledgements
•
Figure 2. Layout for fluidized-bed system (Boateng et al., 2007).
•
I would like to thank Mr. Bill Allen for his tireless assistance and
advice.
USDA National Needs Fellowship, Sloan Foundation, SunGrant (North
Central Region), and Hispanic Leaders in Agriculture and the
Environment (HLAE) for financial support.
References
•
Please contact Jatara Wise (jwise@tamu.edu) for references.