Biofuels: Environmental Consequences and Interactions with Changing Land Use: Chapter 3

The International SCOPE Biofuels Project gratefully acknowledges support from the United Nations Foundation, Deutsche Forschungsgemeinschaft, the David & Lucile Packard Foundation, UNEP, the Cornell Center for a Sustainable Future, the Biogeochemistry & Biocomplexity Initiative at Cornell University, an endowment provided to Cornell University by David R. Atkinson, and the Wuppertal Institute for Climate, Environment, and Energy

Investigating the Impacts of Feedstock Variability on a Carbon-Negative Autothermal Pyrolysis System Using Machine Learning

Feedstock properties impact the economic feasibility and sustainability of biorefinery systems. Scientists have developed pyrolysis kinetics, process, and assessment models that estimate the costs and greenhouse gas (GHG) emissions of various biorefineries. Previous studies demonstrate that feedstock properties have a significant influence on product costs and lifecycle emissions. However, feedstock variability remains a challenge due to a large number of possible feedstock property combinations and limited public availability of feedstock composition data. Here, we demonstrate the use of machine learning (ML) models to generate large feedstock sample data from a smaller sample set for sustainability assessment of biorefinery systems. This study predicts the impact of feedstock properties on the profitability and sustainability of a lignocellulosic biomass autothermal pyrolysis (ATP) biorefinery producing sugar, phenolic oil, and biochar. Generative Adversarial Networks and Kernel Density Estimation machine learning models are used to generate 3,000 feedstock samples of diverse biochemical compositions. Techno-economic and lifecycle assessments estimated that the ATP minimum sugar selling price (MSSP) ranges between $66/metric ton (MT) and$280/MT, and the greenhouse gas (GHG) range from a net negative GHG emission(s) of −0.56 to −0.74 kg CO2e/kg lignocellulosic biomass processed. These results show the potential of ML to enhance sustainability analyses by replacing Monte Carlo-type approaches to generate large feedstock composition datasets that are representative of empirical data.This article is published as Ganguly A, Brown RC and Wright MM (2022) Investigating the Impacts of Feedstock Variability on a Carbon-Negative Autothermal Pyrolysis System Using Machine Learning. Front. Clim. 4:842650. DOI: 10.3389/fclim.2022.842650. Copyright 2022 Ganguly, Brown, and Wright. Attribution 4.0 International (CC BY 4.0). Posted with permission

Techno-economic and greenhouse gas emission assessment of carbon negative pyrolysis technology

Carbon-negative energy removes carbon dioxide from the atmosphere while providing energy to society. The pyrolysis-biochar platform achieves carbon-negative energy by producing bio-oil as an energy product and biochar as a carbon sequestration agent. This study evaluates the economic and environmental performance of conventional fast pyrolysis (FP) and autothermal pyrolysis (ATP) systems with and without pretreatment of three kinds of biomass to produce sugars, phenolic oil, and biochar as valuable products while achieving carbon negative emissions. Techno-economic (TEA) and life cycle analysis (LCA) results show minimum sugar selling prices (MSSP) as low as zero while achieving significant carbon dioxide removal from the atmosphere. Comparison of these systems to direct air capture (DAC) shows that the pyrolytic systems are competitive both in terms of net carbon dioxide (CO2) removal per unit of energy consumption and cost of removing CO2 which ranges between $30 to −$139 per ton CO2 removed.This article is published as Ganguly, Arna, Robert C. Brown, and Mark Mba Wright. "Techno-economic and greenhouse gas emission assessment of carbon negative pyrolysis technology." Green Chemistry 24, no. 23 (2022): 9290-9302. DOI: 10.1039/D2GC03172H. Copyright 2022 The Royal Society of Chemistry. Attribution-NonCommercial 3.0 Unported (CC BY-NC 3.0). Posted with permission

Technoeconomic analysis of photoelectrochemical hydrogen production from desalination waste brine using concentrated solar flux

Co-generation of hydrogen with value-added by-products is a promising route for affordable low-carbon hydrogen. This work presents a system for and a technoeconomic analysis of hydrogen with the co-generation of chlorine and sodium hydroxide from waste brine. The system uses a conceptual triple-junction gallium arsenide (3-J GaAs)-based photoelectrochemical (PEC) reactor at high solar concentrations (50–500x). The base case of 200x solar concentration results in a solar-to-chemical (SCE) efficiency of 15% and a levelized cost of hydrogen (LCOH) production of $15.76/kgH2. Revenue from by-products ($45.36/kgH2) is critical for offsetting the operating costs, with sodium hydroxide constituting 64% of total by-product revenue. The sensitivity analysis showed that under favorable combinations of the key variables (sodium hydroxide price, waste brine pretreatment price, and PEC replacement lifetime) PEC hydrogen generation from waste brine would be viable and have prices reaching $0.78/kgH2

Ultra-Low Carbon Emissions from Coal-Fired Power Plants through Bio-Oil Co-Firing and Biochar Sequestration

This study investigates a novel strategy of reducing carbon emissions from coal-fired power plants through co-firing bio-oil and sequestering biochar in agricultural lands. The heavy end fraction of bio-oil recovered from corn stover fast pyrolysis is blended and co-fired with bituminous coal to form a bio-oil co-firing fuel (BCF). Life-cycle greenhouse gas (GHG) emissions per kWh electricity produced vary from 1.02 to 0.26 kg CO₂-eq among different cases, with BCF heavy end fractions ranging from 10% to 60%, which corresponds to a GHG emissions reduction of 2.9% to 74.9% compared with that from traditional bituminous coal power plants. We found a heavy end fraction between 34.8% and 37.3% is required to meet the Clean Power Plan’s emission regulation for new coal-fired power plants. The minimum electricity selling prices are predicted to increase from 8.8 to 14.9 cents/kWh, with heavy end fractions ranging from 30% to 60%. A minimum carbon price of $67.4 ± 13 per metric ton of CO₂-eq was estimated to make BCF power commercially viable for the base case. These results suggest that BCF co-firing is an attractive pathway for clean power generation in existing power plants with a potential for significant reductions in carbon emissions

Comparative Techno-economic Analysis and Life Cycle Assessment of Producing High-Value Chemicals and Fuels from Waste Plastic via Conventional Pyrolysis and

The rapid rise in global plastic production in recent decades has resulted in the massive generation of plastic waste. Over 75% of the plastic waste generated in the United States was sent to landfills, with a meager 8.7% recycled. Plastics are valuable feedstocks for platform chemicals and fuels. Chemical upcycling of waste high-density polyethylene (HDPE) is gaining more attention as a potentially feasible and environmentally friendly plastic waste management technology. Conventional pyrolysis (CPY) and thermal oxo-degradation (TOD) are two chemical upcycling technologies actively researched for decomposing waste HDPE into valuable chemicals and fuels. However, there are few studies on the techno-economic analysis (TEA) and life cycle assessment (LCA) of these technologies for converting waste HDPE to valuable products. This study conducts a comparative TEA and LCA study of the thermochemical decomposition of waste HDPE to produce gaseous (ethylene and propylene) and liquid (naphtha, diesel, and wax) products by CPY and TOD. The study elucidates and compares the impact of hydrocracking longer chain hydrocarbons to produce more valuable products on the TEA and LCA. The TEA showed that the fixed capital investment could range from $32.5 million for TOD without hydrocracking to$244 million for CPY with hydrocracking scenarios. Annual revenues range from $28.1 million to$71.5 million in favor of scenarios with hydrocracking. However, the net present value ranges from $1.4 million to$265.8 million in favor of scenarios without hydrocracking. Sensitivity analysis showed that fixed capital cost, facility capacity, and product prices have the biggest impact on the process economics of the facilities, while utilities and waste transportation to refineries have the biggest impact on environmental impacts. The LCA showed that primary products from scenarios without hydrocracking can be more environmentally friendly than virgin products from petroleum processes. However, TOD and CPY with hydrocracking primary products have more emissions than those of virgin products.This is a manuscript of an article published as Olafasakin, Olumide, Jiaze Ma, Victor Zavala, Robert C. Brown, George W. Huber, and Mark Mba-Wright. "Comparative Techno-economic Analysis and Life Cycle Assessment of Producing High-Value Chemicals and Fuels from Waste Plastic via Conventional Pyrolysis and Thermal Oxo-degradation." Energy & Fuels (2023). doi:https://doi.org/10.1021/acs.energyfuels.3c02321. Posted with Permission.Copyright © 2023 American Chemical Society

Techno‐economic and life cycle analysis of renewable natural gas derived from anaerobic digestion of grassy biomass: A US Corn Belt watershed case study

Abstract Restoring native grassland vegetation can substantially improve ecosystem service outcomes from agricultural watersheds, but profitable pathways are needed to incentivize conversion from conventional crops. Given growing demand for renewable energy, using grassy biomass to produce biofuels provides a potential solution. We assessed the techno‐economic feasibility and life cycle outcomes of a “grass‐to‐gas” pathway that includes harvesting grassy (lignocellulosic) biomass for renewable natural gas (RNG) production through anaerobic digestion (AD), expanding on previous research that quantified ecosystem service and landowner financial outcomes of simulated grassland restoration in the Grand River Basin of Iowa and Missouri, United States. We found that the amount of RNG produced through AD of grassy biomass ranged 0.12–45.04 million gigajoules (GJ), and the net present value (NPV) of the RNG ranged −$97 to$422 million, depending on the combination of land use, productivity, and environmental credit scenarios. Positive NPVs are achieved with environmental credits for replacement of synthetic agricultural inputs with digestate and clean fuel production (e.g., USEPA D3 Renewable Identification Number, California Low Carbon Fuel Standard). Producing RNG from grassy biomass emits 15.1 g CO2‐eq/MJ, which compares favorably to the fossil natural gas value of 61.1 g CO2‐eq/MJ and exceeds the US Environmental Protection Agency's requirement for cellulosic biofuel. Overall, this study demonstrates opportunities and limitations to using grassy biomass from restored grasslands for sustainable RNG production

A lignin-first strategy to recover hydroxycinnamic acids and improve cellulosic ethanol production from corn stover

The goal of this research is to develop a partial delignification process for corn stover that simultaneously improves accessibility of enzymes to cellulose and recovers hydroxycinnamic acids (HCA) as a value-added product from the lignin. We recover HCAs from corn stover with a mild base extraction employing sodium hydroxide, ethanol, and water. The total HCA yield was 33.5 wt% on a lignin basis and approximately 6 wt% on a corn stover basis. This partial delignification pretreatment allowed 85 wt% of total available glucose to be recovered by enzymatic hydrolysis using an enzyme loading that is only 10% of the level recommended for recovering sugars from lignocellulosic biomass. Technoeconomic analysis indicates that recovery of HCAs could reduce the selling price of ethanol by $0.26 L-1. That part of the lignin not removed as HCA becomes a co-product of enzymatic hydrolysis suitable for thermochemical processing into additional biofuels and/or chemicals.This is a manuscript of an article published as Johnston, Patrick A., Haoqin Zhou, Alvina Aui, Mark Mba Wright, Zhiyou Wen, and Robert C. Brown. "A lignin-first strategy to recover hydroxycinnamic acids and improve cellulosic ethanol production from corn stover." Biomass and Bioenergy 138 (2020): 105579. DOI: 10.1016/j.biombioe.2020.105579. Posted with permission.</p

Economic Evaluation of Infrastructures for Thermochemical Upcycling of Post-Consumer Plastic Waste

Thermochemical technologies, such as pyrolysis, offer a potentially scalable pathway for upcycling diverse types of plastic waste (PW) into value-added chemicals. However, deploying these technologies in waste management infrastructures is not straightforward because such systems involve a wide range of interdependent stakeholders, processing facilities, and products. In this work, we present a holistic optimization framework that integrates value-chain analysis, techno-economic analysis, and life-cycle analysis for investigating the economic viability and environmental benefits of upcycling infrastructures that collect, sort, clean, and process post-consumer PW for producing virgin polymer resins. The framework is applied to a case study in the upper Midwest region of the US. Our analysis reveals that the infrastructures are economically viable and could activate a regional circular economy that generates over 1 billion USD in annual profit. Moreover, our analysis reveals that this economy can reduce the carbon footprint of PW incineration by half. Our framework also determines the inherent values of post-consumer PW and of derived products such as plastic bales and pyrolysis oil; we find that, in these infrastructures, PW becomes a highly valuable feedstock with a market value of 500 USD/tonne. We discuss how this market value can generate incentives that foster more effective waste pre-sorting practices by consumers that can help bypass material recycling facilities and increase total system profit

Biofuels: Environmental Consequences and Interactions with Changing Land Use: Chapter 17

The International SCOPE Biofuels Project gratefully acknowledges support from the United Nations Foundation, Deutsche Forschungsgemeinschaft, the David & Lucile Packard Foundation, UNEP, the Cornell Center for a Sustainable Future, the Biogeochemistry & Biocomplexity Initiative at Cornell University, an endowment provided to Cornell University by David R. Atkinson, and the Wuppertal Institute for Climate, Environment, and Energy