James Weifu Lee and Danny M. Day

Abstract Smokeless (emission-free, clean, and efficient) biomass pyrolysis for biochar and biofuel production is a possible arsenal for global carbon capture and sequestration at gigatons of carbon (GtC) scales. The world’s annual unused waste biomass, such as crop stovers, is about 3.3 GtC y_1. If this amount of biomass (3.3 GtC y-1) is processed through the smokeless pyrolysis approach, it could pro­duce biochar (1.65 GtC y-1) and biofuels (with heating value equivalent to 3,250 million barrels of crude oil) to help control global warming and achieve energy independence from fossil fuel. By using 1.65 GtC y-1 of biochar into soil and/or underground reservoirs alone, it would offset the 8.5 GtC y_1 of fossil fuel CO. emissions by 19%. The worldwide maximum capacity for storing biochar carbon into agricultural soils is estimated to be about 428 GtC. It may be also possible to provide a global carbon “thermostat” mechanism by creating biochar carbon energy storage reserves. This biomass-pyrolysis “carbon-negative” energy approach merits serious research and development worldwide to help provide clean energy and con­trol climate change for a sustainable future of human civilization on Earth.

J. W. Lee (*)

Department of Chemistry and Biochemistry, Old Dominion University,

Physical Sciences Building 3100B, 4402 Elkhorn Avenue, Norfolk, VA 23529, USA

Whiting School of Engineering, Johns Hopkins University,

118 Latrobe Hall, Baltimore, MD 21218, USA e-mail: jlee349@jhu. edu; jwlee@odu. edu

D. M. Day

Eprida Power and Life Sciences, Inc. ,

6300 Powers Ferry Road, #307, Atlanta, GA 30339, USA

J. W. Lee (ed.), Advanced Biofuels and Bioproducts, DOI 10.1007/978-1-4614-3348-4_3, © Springer Science+Business Media New York 2013

1 Introduction

This approach of smokeless (emission-free, clean, and efficient) biomass pyrolysis with biochar application as soil amendment and carbon sequestration agent was initiated through our joint 2002 US provisional patent application followed by a PCT application [1] . One of the key concepts here is to use a biomass-pyrolysis process to produce certain biofuels and more importantly to “lock” some of the unstable biomass carbon, such as dead leaves, waste woods, cornstovers, and rice straws, into a stable form of carbon—biochar, which could be used as a soil amendment to improve soil fertility and at the same time, to serve as a carbon sequestration agent, since biochar can be stable in soil for thousands of years and can help retain nutrients in soil to reduce the runoff of fertilizers from agriculture lands that would otherwise pollute the rivers and water bodies. The general philosophy or the “idea roots” of this approach can trace back to Lee’s early work in 1998 at Oak Ridge National Laboratory (ORNL) in developing the method for reducing CO2, CO, NOx, and SOx emissions, which subsequently resulted in a US Patent that laid a framework of solidifying carbon dioxide and placing it into soil and/or subsoil earth layers for win-win benefits on carbon sequestration, environmental health, and agricultural productivity [2, 3]. In 2002, when Day of Eprida visited Lee’s lab at ORNL, we shared our visions and together extended this approach with the process of smokeless biomass pyrolysis and using biochar fertilizer as soil amendment and carbon seques­tration agent [4, 5].

When this approach of smokeless biomass pyrolysis and using biochar fertilizer as soil amendment for carbon sequestration was fitst proposed, we encountered various skepticisms from our peers, some of them with very good/tough questions, such as “how stable is biochar when used as carbon sequestration agent in soil?” and “how long would your envisioned biochar fertility effect last in soil?” In our minds, there were no doubts that biochar material and its fertility effects (such as cation exchanging capacity) could be stable for hundreds and perhaps thousands of years. However, to provide an absolutely clear answer to this type of questions, it would require a long-term biochar-soil experiment that lasts hundreds of years, which would be practically impossible to complete in our life time. We presented our findings first at the USDA Carbon Sequestration Conference in November of 2002 and included references to the “black carbon” in the prehistoric (pre-Columbian) “Terra Preta” soils in Amazonia [6, 7]. Subsequently, one of us (Day) organized and sponsored the first two US biochar scientific meetings and held briefings around the world to educate and further the use of biochar. The first US biochar and energy production scientific meeting which was sponsored by Eprida (Day) held in June 2004 at the University of Georgia at Athens with about 60 participants from across the world, including Brazil, Austria, Germany, New Zealand, Japan, and the USA. Since then, the approach of smokeless biomass pyrolysis and biochar soil application gradually became a hot research and development topic across the world.

Because biochar is not completely digestible to microorganisms, a biochar-based soil amendment could serve as a permanent carbon-sequestration agent in soils/ subsoil earth layers for thousands of years. As indicated by the recent discovery of biochar particles in “Terra Preta” soils formed by pre-Columbian indigenous agriculturalists in Amazonia, biochar materials could be stored in soils as a means of carbon sequestration for hundreds and perhaps thousands of years. The longest lifetime of biochar material that has been reported with scientific evidence is about

38,0 years, according to the carbon isotope dating of a prehistoric Cro-Magnon man’s charcoal painting discovered in the Grotte Chauvet cave [8]. The black car­bon in a “Terra Preta” soil at the Acutuba site has been dated about 6,850 years ago [9]. At the Jaguariuna soil site in Brazil, some high abundance of charcoal found in the summit soil was dated to occur about 9,000 years ago [10]. These carbon-isotope dating results all indicate how stable and permanent the biochar carbon sequestration can be. Through a 14C-labeling study, the mean residence time of pyrogenic carbon in soils has now been estimated in the range of millennia [11].

Here, we must point out that the practice of the pre-Columbian indigenous agriculturalists may or may not be applicable to achieving our envisioned clean energy production and global biochar carbon sequestration, although the discovery of biochar particles in “Terra Preta” soils seems to provide quite nice support for the proposed approach of smokeless biomass pyrolysis using biochar fertilizer for soil amendment and carbon sequestration. First of all, the biochar materials accumulated in the “Terra Preta” soil were probably resulted from some low-tech processes, including (1) “slash and burn,” (2) “slash and char,” and (3) wild fires. All of these three processes generate large amounts of hazardous smokes that can impact air quality. In the practice of “slash and burn,” trees, bushes, and other green plants are cut down and burned in the field to clear the land for cropland. The burning of biomass in open fields creates large amounts of hazardous smoke similar to a wild fire; the biochar formed through the slash-and-burn techniques represents only about 1.7% of the pre-burn biomass [12]. “Slash and char” is a practice to make charcoal from biomass by use of conventional charcoal kilns [11, 13] , which is better than the practice of “slash and burn,” but would still produce large amount of smoke. Use of conventional charcoal kilns for charcoal production at a gigatons of carbon (GtC) scale would produce large amounts of smoke (pollutants including soot black-carbon particles) that are not acceptable to the environment and air quality, in addition to allowing heat, energy, and valuable chemicals to escape into the atmosphere. A recent study indicates that black-carbon aerosols which can directly absorb solar radiation might have substantially contributed to the rapid Arctic warming during the past 3 decades [14, 15]. Therefore, a smokeless and efficient modern biomass — pyrolysis process is essential to achieve the mission of annually converting gigatons of biomass into biochar and biofuel. Development and deployment of a modern biomass-pyrolysis biofuel/biochar-producing process would enable collecting of the “smoke” (organic volatiles and gases) into the biofuel fraction for clean energy (e. g., hydrogen and/or liquid fuels) production. Therefore, further development and use of this type of smokeless biofuel/biochar-producing biomass-pyrolysis tech­nologies are needed for the envisioned large (GtC) scale mission of mitigating global CO2 emissions, and, at the same time, ensuring good air quality.

Furthermore, the “Terra Preta” soils in Amazonia rain forest region represent only a tiny spot on Earth. What one may learn from there may or may not be useful to the rest of the world because of the differences in climates, soil types, crops and ecological systems, and other factors. More importantly, for the envisioned modern application of biochar as a meaningful arsenal for global carbon sequestration to control global warming, it would require an operation of both biochar production and soil application at GtC scales, which have never been done in any human his­tory. Serious studies across the world are needed before this approach could be considered for practical implementation.

Therefore, in the following, we provide a quick overview of the biomass-pyrolysis “carbon-negative” energy approach and discuss its future research and development opportunities.