skip to main content

Title: Sustainable biochar to mitigate global climate change

Production of biochar (the carbon-rich solid formed by pyrolysis of biomass), in combination with its storage in soils, has been suggested as a means to abate anthropogenic climate change, while simultaneously increasing crop yields. The climate mitigation potential stems primarily from the highly recalcitrant nature of biochar, which slows the rate at which photosynthetically fixed carbon is returned to the atmosphere. Significant uncertainties exist, however, regarding the impact, capacity, and sustainability of biochar for carbon capture and storage when scaled to the global level. Previous estimates, based on simple assumptions, vary widely. Here we show that, subject to strict environmental and modest economic constraints on biomass procurement and biochar production methods, annual net emissions of CO2, CH4 and N2O could be reduced by 1.1 - 1.9 Pg CO2-C equivalent (CO2-Ce)/yr (7 - 13% of current anthropogenic CO2-Ce emissions; 1Pg = 1 Gt). Over one century, cumulative net emissions of these gases could be reduced by 72-140 Pg CO2-Ce. The lower end of this range uses currently untapped residues and wastes; the upper end requires substantial alteration to global biomass management, but would not endanger food security, habitat or soil conservation. Half the avoided emissions are due to the net Cmore » sequestered as biochar, one-quarter to replacement of fossil-fuel energy by pyrolysis energy, and one-quarter to avoided emissions of CH4 and N2O. The total mitigation potential is 18-30% greater than if the same biomass were combusted to produce energy. Despite limited data for the decomposition rate of biochar in soils and the effects of biochar additions on soil greenhouse-gas fluxes, sensitivity within realistic ranges of these parameters is small, resulting in an uncertainty of ±8% (±1 s.d.) in our estimates. Achieving these mitigation results requires, however, that biochar production be performed using only low-emissions technologies and feedstocks obtained sustainably, with minimal carbon debt incurred from land-use change.« less
Authors:
; ; ; ;
Publication Date:
OSTI Identifier:
990551
Report Number(s):
PNNL-SA-68680
KP1702020; TRN: US201020%%409
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature Communications, 1:Article No. 56; Journal Volume: 1
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; BIOMASS; CARBON DIOXIDE; CARBON SEQUESTRATION; CLIMATIC CHANGE; CROPS; ECONOMICS; FOOD; GASES; HABITAT; LAND USE; METHANE; MITIGATION; NITROUS OXIDE; PYROLYSIS; RESIDUES; SENSITIVITY; SOIL CONSERVATION; SOILS; STORAGE; WASTES biochar; climate change mitigation; carbon sequestration; bioenergy; CO2; N2O; CH4; carbon dioxide; nitrous oxide; methane; soil carbon; biomass; pyrolysis; greenhouse gases