Biochar Systems as Options for Carbon Dioxide Removal

Biochar Systems as Options for Carbon Dioxide Removal Johannes Lehmann and Dominic Woolf Cornell University, USA

Climate Mitigation: Harnessing Big Fluxes Entry Points: A: Soil CDR and emission reduction through pyrolysis: reduce CO 2 /N 2 O/CH 4 return of the charred OM B: Soil CDR and emission reduction through soil application: B1: reduce soil GHG emissions (CO 2 /N 2 O/CH 4 ) B2: increase CO 2 capture by plants through photosynthesis Lehmann, 2007

Climate Change Mitigation Life Cycle Woolf et al, 2010, Nature Communications 1, 56

Molecular Properties Low temperature Corn-350-BC High Corn-600-BC temperature A (corn-350-bc) B (corn-600-bc) Small cluster sizes: 18-40 C from oak wood and corn residues at 350 C and 600 C 25 to 52 C from chestnut wood between 500 C and 700 C 20 or more C in Midwestern Mollisol and an Amazonian Dark Earth 5 nm 5 nm C (oak-350-bc) D (oak-600-bc) Nguyen et al, 2010, EST 44, 3324 3331 McBeath et al, 2011, OG 42, 1194-1202 Mao et al, 2012, EST 46, 9571-9576

Persistence in Soil Biochar with higher condensation (=low H/Corg ratios) have greater persistence 500 (Only experiments longer than one year, 2-pool model, 10 C) Lehmann et al, 2015, Routledge

Priming of Existing Soil OC by Biochar Average reduction -3.8% (95% CI = -8.1 0.8%) Wang et al., 2016 Global Change Biology 8, 512-523 Whitman et al, 2015, Routledge

Priming of Existing Soil OC by Biochar Greater SOC while root biomass unchanged Negative priming of SOM by 6% and increased recovery of root-derived C by 20% Nine years after one-time biochar application of 10 t ha -1 Weng et al., 2017 Nature Climate Change 7, 371-376

Soil Nitrous Oxide Emissions with Biochar Average reduction 54% (n=30 studies) Cayuela et al. 2015, Agr. Ecosys. Env. 191, 5-16

Electron Flux through Biochar Sun et al, 2017, Nature Communications 8, 14873

Life-Cycle Assessment: Energy Balance GJ per Mg of dry, ash-free feedstock example system based on slow pyrolysis at 450 C followed by tar-cracking at 800 C (Woolf et al., 2014 ES&T)

S Yard waste Late stover Early stover Switch grass A Switch grass B Yard waste gen. cons. avoid fos fuel Life-Cycle Assessment: avoid compost Greenhouse Gases (b) gen. emit. reduct. emit. reduct. emit. reduct. emit. reduct. emit. reduct. Net = + 4043 Greenhouse gases (kg CO 2 e t -1 dry feedstock) 0 300 600 900 Net = - 864 Net = - 793 Net = - 442 Net = + 36 Net = - 885 syngas heat LUC & field emiss. agrochems field ops other stable C avoid foss fuel gen. & comb. land-use seq. reduced soil N2O emiss. avoid compost (kg CO 2 e t -1 DM biomass) Pyrolysis+biochar: -864 Combustion: -987 Offsetting NG for heat Assumes energy can be utilized! Effects on crop growth or soil GHG not included! Roberts et al, 2010, Environmental Science and Technology 44, 827 833

Cumulative Avoided Emissions (Pg CO 2 -Ce/100yrs) Cumulative (Pg C CDR and Avoided Emissions: Global 0.95 Pg C yr -1 Biochar Combustion Emissions 0yrs) Woolf et al, 2010, Nature Communications 1, 56

Cumulative (Pg C CDR and Avoided Emissions: Landuse Cumulative Avoided Emissions (Pg CO 2 -Ce/100yrs) Tg C yr -1 Biochar Combustion 60 55 50 110 70 70 110 230 230 Emissions 0yrs) Woolf et al, 2010, Nature Communications 1, 56

Biochar to Soil Photosynthesis Energy+Emissions Photosynthesis Energy Emissions BECCS vs BEBCS? Bioenergy-Biochar Systems (BEBCS) Nearly 50% of total energy generated About 50% of carbon sequestered Bioenergy with Carbon Capture and Storage (BECCS) Nearly 100% of total energy generated About 100% of carbon stored Energy Energy Potential plant growth increases non-co 2 GHG decreases eventual (but slow) CO 2 evolution Potential CO 2 leakage

BECCS vs BEBCS? BECCS: o Large industrial investment and technical capabilities (technoeconomic discussion) o Failure on transport and storage (risk discussion) o Geostrategic decision how to utilize photosynthetically fixed organic carbon (societal discussion) BEBCS (and without bioenergy): o Limited scalability for individual boilers, materials handling (techno-economic discussion) o Distributed (adoption discussion) o Deviation to bioenergy (risk discussion)

Relative Economic Viability Earlier Adoption of Biochar Systems than BECCS at lower C prices BEBCS: Bioenergy-Biochar Systems BECCS: Bioenergy with Carbon Capture and Storage BES: Bioenergy Systems Woolf et al, 2016, Nature Communications 7, 13160

Biochar in Context: Soil Management Biochar on upper end of soil-based approaches Highly distributed Paustian et al, 2016, Nature 532, 49-57

Abatement rates (t CO 2 e ha -1 yr -1 ) Biochar in Context: Land Management Combinations? Exclusions? World Bank 2012, Report 67395-GLB

Basic Research Needs on Soil o Mechanisms of N 2 O reduction in the presence of biochar (increases found with high biochar N) and how to maximize these o Mechanisms of CH 4 changes in the presence of biochar (both increase and decreases observed) o Mechanisms of negative priming that can be leveraged to decrease mineralization of native SOC and plant C input (root and leaf litter, exudation) o Mechanisms of biochar effects on soil microorganisms, water, and metal biogeochemistry

Basic Research Needs on Biochar Systems o Spatial modeling of distributed biomass potential for pyrolysis and its alternative uses o Spatially-explicit techno-economic modeling of biochar systems and its alternatives

Applied Research + Developm. Needs (M&E) o Industrial-scale bioenergy with biochar production Product consistency Energy budget Problematic wastes (animal manures; sewage sludge; pine bark beetle kill; invasive species; fire reduction; etc.) o Biochar product development for large-scale distribution (small/medium-scale distribution, such as garden stores and commercial greenhouses is already happening) Materials handling through to soil application Fate of biochar at a landscape scale (mineralization, 3-waypriming, leaching, wind and water erosion) Establishing persistence (mineralization) under different soil environments (climate, soil mineralogy, texture, terrain)

Relative Economic Viability Relative Net Present Value BEBCS: Bioenergy-Biochar Systems BECCS: Bioenergy with Carbon Capture and Storage BES: Bioenergy Systems Woolf et al, 2016, Nature Communications 7, 13160

Avoided Emissions and CDR: Sensitivity Woolf et al, 2010, Nature Communications 1, 56

Soil Responsiveness to Biochar Intervention Woolf et al, 2010, Nature Communications 1:56

Severity of Fertility Constraints Soil Benefits in GHG Balance At 0: combustion = pyrolysis+biochar Gas Oil Coal Soil Benefits Essential! (in many systems) C Intensity of Offset Energy Woolf et al, 2010, Nature Communications 1, 56

Electron Flux through Biochar Sun et al, 2017, Nature Communications 8, 14873

Electron Transfer Rate (cm s -1 ) Bacterial Growth Rate (ma h -1 ) Electron Flux Microbial Growth Sun et al, in prep

Microbial Signaling acyl-homoserine lactone E. coli Masiello et al, 2013 ES&T

Biochar Persistence How Much is Needed? Long term Annual Application and Net Sequestration (fraction per year) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 50 Application 20 50 10 100 Mean residence times Proportion of labile C (MRT of 20 yrs) 5 200 0 100 200 300 400 500 Years 0 500 1000 10,000 Lehmann et al, 2010, in: Imperial College Press

Biochar Persistence How Much is Needed? * Life Cycle Assessment of GHG emissions 20% mineralization Roberts et al, unpubl. data

Biochar Persistence How Much is Needed? Sensitivity analyses Table - Sensitivity analysis results. Parameter Value Net GHG (kg CO2e t -1 DM) Change from baseline (%) Net revenue ($ t -1 DM) Change from baseline (%) biochar yield 20-971 -10 28-26 (%) 25-1076 0 37 0 30-1180 10 47 26 stable C 70-1014 -6 36-3 (%) 80-1076 0 37 0 95-1169 9 39 5 reduced soil 0-1047 -3 37-2 N2O emissions 1-1076 0 37 0 (yrs) 5-1193 11 40 6 $20 t -1 CO 2 e 5 t biochar ha -1 Roberts et al, unpubl. data