Mark M. Wright

Continuous production of sugars from pyrolysis of acid-infused lignocellulosic biomass

Although pyrolysis of carbohydrate-rich biomass should theoretically yield large amounts of sugar, the presence of alkali and alkaline earth metals (AAEMs) in most biomass prevents this from happening. Even in small amounts, AAEM strongly catalyzes the fragmentation of holocellulose to light oxygenates compared to the thermally-induced breaking of glycosidic bonds that yield anhydrosugars. The concept of AAEM passivation, by which the catalytic activity of AAEMs can be suppressed to enhance thermal depolymerization of lignocellulose to sugars, has been previously established at the microgram scale using batch reactors. The feasibility of increasing sugar yield via AAEM passivation has not been previously demonstrated at the kilogram scale in a continuous flow reactor. The goal of this research is to demonstrate the enhanced production of sugars from AAEM passivated feedstocks in a continuous auger pyrolyzer at the kilogram scale. Alkali and alkaline earth metal passivation prior to pyrolysis increased total sugars from red oak by 105% compared to conventional pyrolysis, increasing from 7.8 wt% to 15.9 wt% of feedstock. Light oxygenates and non-condensable gases (NCGs) simultaneously decreased 45%, from 27.1 wt% to 14.7 wt% of feedstock as a result of AAEM passivation. Similarly, AAEM passivation of switchgrass increased total sugars by 259%, from 4.5 wt% to 16.2 wt% of feedstock, while the light oxygenates and NCGs decreased by 48%, from 20.0 wt% to 10.5 wt% of feedstock. An undesirable outcome of AAEM passivation was an increase in char production, increasing by 65% and 30% for pyrolysis of red oak and switchgrass, respectively. Loss of lignin-derived phenolic compounds from the bio-oil can explain 67% and 38% of the increase in char for red oak and switchgrass, respectively. The remaining 33% char increase for red oak (3.1 wt% char) and 62% char increase for switchgrass (4.0 wt% char) appear to be from carbonization of sugars released during pyrolysis of acid-infused biomass.

Techno-economic and uncertainty analysis of in situ and ex situ fast pyrolysis for biofuel production

This study evaluates the techno-economic uncertainty in cost estimates for two emerging technologies for biofuel production: in situ and ex situ catalytic pyrolysis. The probability distributions for the minimum fuel-selling price (MFSP) indicate that in situ catalytic pyrolysis has an expected MFSP of

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

1.11 per liter with a standard deviation of 0.29, while the ex situ catalytic pyrolysis has a similar MFSP with a smaller deviation (

The impacts of biomass properties on pyrolysis yields, economic and environmental performance of the pyrolysis-bioenergy-biochar platform to carbon negative energy

1.13 per liter and 0.21 respectively). These results suggest that a biorefinery based on ex situ catalytic pyrolysis could have a lower techno-economic uncertainty than in situ pyrolysis compensating for a slightly higher MFSP cost estimate. Analysis of how each parameter affects the NPV indicates that internal rate of return, feedstock price, total project investment, electricity price, biochar yield and bio-oil yield are parameters which have substantial impact on the MFSP for both in situ and ex situ catalytic pyrolysis.

Natural Gas and Cellulosic Biomass: A Clean Fuel Combination? Determining the Natural Gas Blending Wall in Biofuel Production

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 Plans 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

A Framework for Defining the Economic Feasibility of Cellulosic Biofuel Pathways

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.

Commentary on ‘Current economic obstacles to biochar use in agriculture and climate change mitigation’ regarding uncertainty, context-specificity and alternative value sources

This study evaluated the impact of biomass properties on the pyrolysis product yields, economic and environmental performance for the pyrolysis-biochar-bioenergy platform. We developed and applied a fast pyrolysis, feedstock-sensitive, regression-based chemical process model to 346 different feedstocks, which were grouped into five types: woody, stalk/cob/ear, grass/plant, organic residue/product and husk/shell/pit. The results show that biomass ash content of 0.3-7.7wt% increases biochar yield from 0.13 to 0.16kg/kg of biomass, and decreases biofuel yields from 87.3 to 40.7 gallons per tonne. Higher O/C ratio (0.88-1.12) in biomass decreases biochar yield and increases biofuel yields within the same ash content level. Higher ash content of biomass increases minimum fuel selling price (MFSP), while higher O/C ratio of biomass decreases MFSP within the same ash content level. The impact of ash and O/C ratio of biomass on GHG emissions are not consistent for all feedstocks.

Techno-economic analysis of biomass fast pyrolysis to transportation fuels

Natural gas has the potential to increase the biofuel production output by combining gas- and biomass-to-liquids (GBTL) processes followed by naphtha and diesel fuel synthesis via Fischer-Tropsch (FT). This study reflects on the use of commercial-ready configurations of GBTL technologies and the environmental impact of enhancing biofuels with natural gas. The autothermal and steam-methane reforming processes for natural gas conversion and the gasification of biomass for FT fuel synthesis are modeled to estimate system well-to-wheel emissions and compare them to limits established by U.S. renewable fuel mandates. We show that natural gas can enhance FT biofuel production by reducing the need for water-gas shift (WGS) of biomass-derived syngas to achieve appropriate H2/CO ratios. Specifically, fuel yields are increased from less than 60 gallons per ton to over 100 gallons per ton with increasing natural gas input. However, GBTL facilities would need to limit natural gas use to less than 19.1% on a LHV energy basis (7.83 wt %) to avoid exceeding the emissions limits established by the Renewable Fuels Standard (RFS2) for clean, advanced biofuels. This effectively constitutes a blending limit that constrains the use of natural gas for enhancing the biomass-to-liquids (BTL) process.

Techno-economic comparison of biomass-to-transportation fuels via pyrolysis, gasification, and biochemical pathways

This paper incorporates pathway-specific financial assumptions into techno-economic analyses of cellulosic biofuel pathways under price uncertainty. Five cellulosic biofuel pathway scenarios are developed in a discounted cash flow rate of return spreadsheet to determine pathway-specific costs of debt. The cost of equity for the scenarios is calculated based on the financial characteristics of the US biorenewable industrial sector. A 20-year net present value (NPV) and probability of default for each scenario are stochastically calculated. Mean NPVs vary from a low of –

Establishing the optimal sizes of different kinds of biorefineries.

774 million to a high of –