Steve Peterson USDA – ARS – NCAUR

1. Comparison of gasification and pyrolysis methods for preparing biochar from corn stover and wheat straw Steve Peterson USDA – ARS – NCAUR

2. Uses beyond carbon sequestration • rubber composite filler – particle size a problem • filtration media for filtration applications, particle size is not as important as surface area Applications of biochar

3. Uses beyond carbon sequestration • rubber composite filler • filtration media for composite fillers, large particles = poor reinforcement as filtration media, large, porous particles OK as long as they’re permeable to the medium Applications of biochar

4. Uses beyond carbon sequestration • rubber composite filler • filtration medium • peat moss substitute Later in the program… Applications of biochar

5. feedstock pyrolysis gasification Pyrolysis vs. gasification

6. + biomass (H2, CH4) O2 (gas) biochar (solid) bio-oil (liquid) heat • Pros: • oxygen is omitted, increasing the carbon yield • temperature control is accurate and variable • Cons: • batch method limits throughput • controlled environment = $$ • bio-oil can be problematic during processing Pyrolysis: pros and cons

7. open air system is cheaper and easier to run • can facilitate higher thoughput • scale up is easier and more cost-effecttive • side products are burned off Pros: TLUD = Top Lit UpDraft Cons: • no temperature control, high temps are limited • biochar typically has higher ash content secondary air primary air “AVUD” design by Paul Anderson Gasification: pros and cons image courtesy of www.cleanstove.org

8. wheat straw (WS) corn stover (CS) • both feedstocks are cheap and plentiful • our collaborator has provided us with both glycerin and glycerin-free pelletized forms of WS Feedstocks used

9. corn stover (CS) wheat straw (WS) wheat straw + glycerin (WS+G) Feedstocks used

10. Feedstocks: CS, WS, WS+G Biochar production method: Pyrolysis (retort oven) Gasification (TLUD) 400, 500, 600, and 700°C temperature is not controlled; subject to gasification process Temps: Experimental design

11. T4 T (°C) T3 T2 T1 Monitoring TLUD temperature global time

12. total surface area micropore surface area (micropore  pore with d < 2 nm) Surface area/porosity

13. Observations • CS surface area  with T • WS samples peak below 700°C • micropore % roughly 55-70% • WS+G TLUD markedly higher surface area Surface area/porosity

14. down up CS, 500°C Water sorption trends

15. CS significantly more water-sorptive than WS and WS+G • For CS and WS, water-sorption peaks at 600°C • Water-holding capacity is highest at 400°C and decreases with increasing temperature (not shown) Water sorption trends

16. Ash is an undesired component of biochar consisting of metal oxides; tends to dilute the effects of carbon • Assume limiting oxygen in the process will help reduce ash; retort > TLUD Ash content

17. Higher surface area & micropore SA with retort methods vs. TLUD • Lower ash content with retort method (except for WS+G sample) • Appears that the addition of glycerin to WS increases the biochar ash content • CS much more water sorptive than WS and WS+G Bottom line: is the “lower quality” char from gasification a deal-breaker with the given applications? Conclusions/Summary

18. Paul Wever, Chip Energy AJ Thomas & Ashley Maness Mike Jackson Steve Vaughn HydroStraw, LLC Jason Adkins Nancy Holm, IBG, and ISTC Acknowledgements