The Pyrolysis-Bioenergy-Biochar Pathway to Carbon-Negative Energy Final Report May 31, 2019 Research Institutions Iowa State University University of California, Berkeley Indiana University - Purdue University Indianapolis Investigators Department of Agronomy, Iowa State University: David A. Laird, Professor; Sotirios Archontoulis, Assistant Professor; Fernando E Miguez, Associate Professor; Natalia Rogovska, Assistant Scientist; Santanu Bakshi, Postdoctoral Research Associate; Chumki Banik, Postdoctoral Research Associate; Rivka B. Fidel, Postdoctoral Research Associate; Deborah M. Aller, Graduate Research Assistant; Hamze Dokoohaki, Graduate Research Assistant; Isaiah L. Huber, Graduate Research Assistant; Garret Lies, Undergraduate Assistant. Department of Mechanical Engineering, Iowa State University: Robert C. Brown, Distinguished Professor; Mark Mba-Wright, Associate Professor; Wenqin Li, Graduate Research Assistant. Department of Economics, Iowa State University: Dermot J. Hayes, Professor; Amani E. Elobeid, Lecturer; Wendong Zhang, Assistant Professor; Alejandro Plastina, Assistant Professor; Ryan Goodrich, Graduate Research Assistant; Wendiam Sawadgo, Graduate Research Assistant. School of Public and Environmental Affairs, Indiana University - Purdue University Indianapolis: Jerome Dumortier, Assistant Professor. Department of Agricultural & Resource Economics, University of California, Berkeley: David Zilberman, Professor. Abstract Avoiding irreversible climate change requires >50% reduction in anthropogenic greenhouse gas (GHG) emissions by the year 2050 and the net removal of GHGs from the atmosphere by the end of the 21st century. This challenge is particularly daunting given that energy derived from fossil fuels is at the core of all modern economies and some sectors of the economy, such as transportation, will be almost impossible to completely decarbonize. To address this challenge, we investigated the integrated pyrolysis-bioenergy-biochar platform (PBBP) to determine whether this system can produce economically viable carbon-negative energy products. The PBBP has the potential to be carbon negative because the biomass feedstock used in the PBBP contains carbon, which came from the atmosphere via photosynthesis, and carbon in the biochar co-product has a half life ranging from centuries to millennia when biochar is used as a soil amendment. Major accomplishments during the project include the design and development of a biochar module within the Agricultural Production Systems sIMulator (APSIM), a widely used and publically available cropping systems model. The APSIM Biochar Model provides for the first time a means of systematically investigating complex soil-biochar-crop-climate-management interactions, and critically a means of estimating the agronomic and environmental impacts of soil biochar applications at scales ranging from a single pedon to global. Developing the biochar model required a mechanistic understanding of complex biochar, soil, crop, management, and climate interactions. To this end, we conducted a series of laboratory studies to assess the diversity of biochar physical and chemical properties and a series of laboratory-incubations, greenhouse pot experiments, and agricultural field trials to understand how biochar amendments and biochar properties influence soil processes and plant growth. Key products of this research include quantitative relationships relating the highest pyrolysis temperature and biomass feedstock properties to biochar alkalinity, anion and cation exchange capacity, nitrate and ammonium sorption capacity, and ratios of labile to recalcitrant biochar carbon and nitrogen. We developed a hot water extraction procedure that can be used to rapidly quantify the size and C:N ratios of the labile and recalcitrant biochar fractions, which are critical input parameters for the APSIM Biochar Model. The APSIM Biochar Model was calibrated and validated using results from long-term field trials and shown to accurately predict biochar effects on soil bulk density, soil pH, soil water content, and nitrogen availability across multiple years and soil types. Predictions of biochar impacts on crop growth and grain yields at the field plot scale were less accurate but captured general trends. This is not surprising given the number of environmental and management factors that influence crop yields at the plot scale. To address biochar impacts on crop yields more accurately at regional and national scales, we integrated the APSIM Biochar Model with the pSIMS platform and built a separate stochastic Bayesian network model that predicts the probability of a crop yield response to biochar for the entire U.S. with 10m X 10m resolution. Combined these products will help businesses to site pyrolysis plants by determining where there is a potential market for biochar and by determining the optimum type of biochar for soils and cropping systems at local and regional scales. The biochar industry exists today at relatively small scale. Vanguard pyrolysis plants are targeting value-added biochar products for niche applications, rather than soil applications on production agricultural fields. To enhance the probability of success for these early pyrolysis plants, we investigated and developed protocols for producing zero-valent iron (ZVI) biochar complexes and high anion exchange capacity (AEC) biochars as potential value-added biochar products. The ZVI biochars were shown to be effective for remediating water contaminated with trichloroethylene (and potentially other chlorinated organic compounds) through reductive dehalogenation and arsenic (and potentially other heavy metals) through complexation and precipitation. The high AEC biochars have potential for removal of oxyanions from industrial and agricultural effluents by anion exchange. Techno-economic analysis (TEA) of the PBBP was used to determine the minimum fuel selling price (MFSP) and lifecycle GHG emissions for a 1000 dry ton per day fast pyrolysis plant. Both MFSP and GHG emissions were shown to be strongly dependent on the ash content and O:C ratio of the biomass feedstock. The TEA results indicate a trade-off between economic and environmental benefits based on feedstock selection. The estimated MFSP for 346 different feedstocks ranged from $2.3/gal to $4.8/gal of liquid fuels in the diesel/gasoline range. The TEA demonstrated that the PBBP has the potential to produce carbon negative energy products even when indirect land use and synergistic agronomic and environmental effects of soil biochar applications are discounted. Economic analysis integrated the APSIM mechanistic and the stochastic Bayesian network biochar models with the CARD/FAPRI Agricultural Outlook Model, a general equilibrium macroeconomic model, to predict farmer’s “willingness to pay” to apply biochar on their fields and the resulting impact of the PBBP on CO2-e emissions and nitrate leaching. It was found that biochar applications to areas with high probability of crop yield response in the U.S. could offset a maximum of 2% of the current U.S. anthropogenic CO2-e emissions per year. Scaling the PBBP to achieve much larger offsets of anthropogenic CO2-e emissions is possible but will require policy changes that include incentives for carbon negative energy production and credits for soil carbon sequestration. Introduction Avoiding irreversible climate change requires >50% reduction in anthropogenic greenhouse gas (GHG) emissions by the year 2050 and the net removal of GHGs from the atmosphere by the end of the 21st century [1]. To address the need to remove GHG from the atmosphere, we are investigating the integrated Pyrolysis-Bioenergy-Biochar Platform (PBBP) for the production of carbon-negative energy (Figure 1). Bio-oil and non-condensable gases produced by fast pyrolysis of biomass are potential sources of liquid transportation fuels, heat, power, bio-asphalt, and other products that can offset fossil fuels [2]. Biochar, the condensed aromatic carbon-rich solid co- product of biomass pyrolysis, is a soil amendment that is effective for sequestering carbon while improving soil quality and reducing leaching of nutrients [3, 4]. The PBBP is potentially carbon negative because the half-life of biochar C in soils is hundreds to thousands of years, depending on the biochar quality. Furthermore, biochar has the potential to increase agricultural productivity, which would have cascading effects, such as decreasing the need for fertilizer and reducing the amount of crop land needed to produce food, which further reduce anthropogenic greenhouse gas emissions. This project was designed to address several of the key challenges limiting industrial scale deployment of the PBBP. One of those challenges is the lack of an ability to predict crop yield response to biochar applications at local, regional, and global scales. Crop yield responses to biochar applications depend on complex interactions among biochar type, soil type, crop genetics, crop management and weather. An ability to predict crop yield responses to biochar applications is necessary for determining the local and regional markets for the biochar co- product of PBBP plants, and hence technoeconomic assessments of the viability of PBBP plants. Furthermore, crop yield responses have feedback effects on regional and global grain markets and land use decisions, which influence GHG emissions. Another key challenge is the lack of an ability to predict direct environmental impacts of soil biochar applications, specifically