Hydrocarbon bio-jet fuel from bioconversion of poplar biomass: life cycle assessment

Multi-criteria decision analysis for the evaluation and screening of sustainable aviation fuel production pathways

The aviation sector, a significant greenhouse gas emitter, must lower its emissions to alleviate the climate change impact. Decarbonization can be achieved by converting low-carbon feedstock to sustainable aviation fuel (SAF). This study reviews SAF production pathways like hydroprocessed esters and fatty acids (HEFA), gasification and Fischer-Tropsch Process (GFT), Alcohol to Jet (ATJ), direct sugar to hydrocarbon (DSHC), and fast pyrolysis (FP). Each pathway's advantages, limitations, cost-effectiveness, and environmental impact are detailed, with reaction pathways, feedstock, and catalyst requirements. A multi-criteria decision framework (MCDS) was used to rank the most promising SAF production pathways. The results show the performance ranking order as HEFA > DSHC > FP > ATJ > GFT, assuming equal weight for all criteria.

Carbon credit reduction: A techno-economic analysis of "drop-in" fuel production

The current study elucidates the fundamentals of technical, financial, and environmental viability of the processes used for sustainable "drop-in" fuel generation. At present, the price of producing "drop-in" fuels is around two times as costly (5-6 USD/gallon) as the cost of fossil fuels (3 USD/gallon), especially when using second-generation feedstocks. Hence, this necessitates a comprehensive techno-economic understanding of the current technologies with respect to "drop-in"-fuel. This entitles technical-economic viability, and environmental sustainability to make the processes involved commercially viable. In this context, the present review addresses unique contrasts among the various processes involved in "drop-in" fuel production. Furthermore, principles and process flow of techno-economic analysis as well as environmental implications in terms of reduced carbon footprint and carbon credit are elucidated to discuss fundamentals of techno-economic analysis in terms of capital and operational expenditure, revenue, simulation, cash flow analysis, mass and energy balances with respect to evidence-based practices. Case specific techno-economic studies with current developments in this field of research with emphasis on software tools viz., Aspen Plus, Aspen HYSIS, Aspen Plus Economic Analyser (APEC) Aspen Icarus Process Evaluator (AIPE) are also highlighted. The study also emphasis on the carbon foot print of biofuels and its carbon credits (Carbon Offset Credits (COCs) and Carbon Reduction Credits (CRCs)) by leveraging a deep technical and robust business-oriented insights about the techno-economic analysis (TEA) exclusively for the biofuel production.

Advances and opportunities in integrating economic and environmental performance of renewable products

There is a growing global need to transition from a fossil-based to a bio-based economy to produce fuels, chemicals, food, and materials. In the specific context of industrial biotechnology, a successful transition toward a sustainable development requires not only steering investment toward a bioeconomy, but also responsibly introducing bio-based products with lower footprints and competitive market prices. A comprehensive sustainability assessment framework applied along various research stages to guide bio-based product development is urgently needed but currently missing. To support holistic approaches to strengthen the global bioeconomy, the present study discusses methodologies and provides perspectives on the successful integration of economic and environmental performance aspects to guide product innovation in biotechnology. Efforts on quantifying the economic and environmental performance of bio-based products are analyzed to highlight recent trends, challenges, and opportunities. We critically analyze methods to integrate Techno-Economic Assessment (TEA) and Life Cycle Assessment (LCA) as example tools that can be used to broaden the scope of assessing biotechnology systems performance. We highlight the lack of social assessment aspects in existing frameworks. Data need for jointly applying TEA and LCA of succinic acid as example commodity chemical are assessed at various Technology readiness levels (TRLs) to illustrate the relevance of the level of integration and show the benefits of the use of combined assessments. The analysis confirms that the implementation of integrated TEA and LCA at lower TRLs will provide more freedom to improve bio-based product's sustainability performance. Consequently, optimizing the system across TRLs will guide sustainability-driven innovation in new biotechnologies transforming renewable feedstock into valuable bio-based products.

Hydrocarbon Bio-Jet Fuel from Bioconversion of Poplar Biomass: Life Cycle Assessment of Site-Specific Impacts

Hydrocarbon drop-in bio-jet fuels could help to reduce greenhouse gas emissions within the aviation sector. Large tracts of land will be required to grow biomass feedstock for this biofuel, and changes to the management of these lands could have substantial environmental impacts. This research uses spatial analysis and life cycle assessment methodologies to investigate potential environmental impacts associated with converting land to grow poplar trees for conversion to bio-jet fuel from different regions within the western United States. Results vary by region and are dependent on land availability, type of land converted, prior land management practices, and poplar growth yields. The conversion of intensively managed cropland to poplar production results in a decrease in fertilizer and a lower annual global warming potential (GWP) (Clarksburg CA region). Bringing unmanaged rangeland into production results in increases in fertilizers, chemical inputs, fuel use, and GWP (Jefferson OR region). Where poplar yields are predicted to be lower, more land is converted to growing poplar to meet feedstock demands (Hayden ID). An increased use of land leads to greater fuel use and GWP. Changes to land use and management practices will drive changes at the local level that need to be understood before developing a drop-in biofuels industry.

Next generation applications of lignin derived commodity products, their life cycle, techno-economics and societal analysis

The pulp and biorefining industries produce their waste as lignin, which is one of the most abundant renewable resources. So far, lignin has been remained severely underutilized and generally burnt in a boiler as a low-value fuel. To demonstrate lignin's potential as a value-added product, we will review market opportunities for lignin related applications by utilizing the thermo-chemical/biological depolymerization strategies (with or without catalysts) and their comparative evaluation. The application of lignin and its derived aromatics in various sectors such as cement industry, bitumen modifier, energy materials, agriculture, nanocomposite, biomedical, H2 source, biosensor and bioimaging have been summarized. This comprehensive review article also highlights the technical, economic, environmental, and socio-economic variable that affect the market value of lignin-derived by-products. The review shows the importance of lignin, and its derived products are a platform for future bioeconomy and sustainability.

Well-to-wake analysis of switchgrass to jet fuel via a novel co-fermentation of sugars and CO2

Lignocellulosic biomass such as switchgrass can be converted to n-butanol using fermentation, which can be further processed into jet fuel. Traditional acetone-butanol-ethanol (ABE) fermentation only converts sugars derived from switchgrass to ABE. Novel co-fermentation processes convert sugars and gas (CO₂/H₂) produced during fermentation into butanol, thus increasing ABE yields by 15.5% compared to traditional ABE fermentation. Herein, the environmental impact of a Switchgrass to Jet Fuel (STJ) pathway was assessed using life cycle assessment (LCA) from well-to-wake. LCAs were performed for greenhouse gas (GHG) emissions from jet fuel production via co-fermentation of sugars and gas for ideal and practical cases of ABE fermentation and seven other jet fuel pathways. The ideal case assumes 100% sugar recovery and 95% ABE yield. The practical case assumes 90% sugar recovery and an 80% ABE yield. Results are presented based on 100-year global warming potential (GWP) per MJ of jet fuel. Co-products were allocated using various methods. The increase in butanol yield via the co-fermentation technology reduced GWP-100 for the STJ pathway by 6.5% compared to traditional ABE fermentation. Similarly, the STJ pathway for the practical case with co-fermentation had 14.2%, 47.5%, 73.8%, and 44.4% less GWP-100 compared to HRJ, Fischer-Tropsch jet fuel from switchgrass, Fischer-Tropsch jet fuel from coal, and conventional petroleum jet fuel. The results demonstrate that the STJ pathway via co-fermentation has the potential to increase product yield while reducing GHG emissions compared to other jet fuel production pathways.

Review of life cycle assessments of lignin and derived products: Lessons learned

In the last decade, the use of lignin as a bio-based alternative for fossil-based products has attracted significant attention, and the first LCAs of lignin and derived products have been conducted. Assessing side-stream products like lignin and potential benefits compared to their fossil counterparts presents complex methodological issues. This article provides a critical review of forty-two peer-reviewed LCAs regarding lignin and derived products. Methodological issues and their influence on the LCA results include the choice of the modeling approach and system boundaries, functional unit definition, impact categories considered, type of data used, handling multifunctionality and biogenic carbon modeling. The review focused on climate change impacts, as this is also the main impact category considered in most studies. Other impact categories in the comparison between lignin-based products and counterparts were also discussed with examples from the studies. Based on ten lessons learned, recommendations were provided for LCA practitioners to increase future consistency of environmental claims made about lignin and lignin-based products. The finding suggest that the environmental performance of lignin-based products is significantly affected by both 1) LCA methodological problems such as allocation practices and biogenic carbon modeling and 2) technical aspects such as the percentage of lignin in the composition of products and the selection of the fuel to replace lignin in internal energy uses. Beyond this, the reviewed LCAs showed that often lignin-based products offer better environmental performances than fossil-based products, especially for climate change.

Production routes to bio-acetic acid: life cycle assessment

BACKGROUND

Similar to biofuels, numerous chemicals produced from petroleum resources can also be made from biomass. In this research we investigate cradle to biorefinery exit gate life cycle impacts of producing acetic acid from poplar biomass using a bioconversion process. A key step in developing acetic acid for commercial markets is producing a product with 99.8% purity. This process has been shown to be potentially energy intensive and in this work two distillation and liquid-liquid extraction methods are evaluated to produce glacial bio-acetic acid. Method one uses ethyl acetate for extraction. Method two uses alamine and diisobutyl ketone. Additionally two different options for meeting energy demands at the biorefinery are modeled. Option one involves burning lignin and natural gas onsite to meet heat/steam and electricity demands. Option two uses only natural gas onsite to meet heat/steam demands, purchases electricity from the grid to meet biorefinery needs, and sells lignin from the poplar biomass as a co-product to a coal burning power plant to be co-fired with coal. System expansion is used to account for by-products and co-products for the main life cycle assessment. Allocation assessments are also performed to compare the life cycle tradeoffs of using system expansion, mass allocation, or economic allocation for bio-acetic acid production. Finally, a sensitivity analysis is conducted to determine potential effects of a decrease in the fermentation of glucose to acetic acid.

RESULTS

Global warming potential (GWP) and fossil fuel use (FFU) for ethyl acetate extraction range from 1000-2500 kg CO₂ eq. and 32-56 GJ per tonne of acetic acid, respectively. Alamine and diisobutyl ketone extraction method GWP and FFU ranges from -370-180 kg CO₂ eq. and 15-25 GJ per tonne of acetic acid, respectively.

CONCLUSIONS

Overall the alamine/diisobutyl ketone extraction method results in lower GWP and FFU values compared to the ethyl acetate extraction method. Only the alamine/diisobutyl extraction method finds GWP and FFU values lower than those of petroleum based acetic acid. For both extraction methods, exporting lignin as a co-product produced larger GWPs and FFU values compared to burning the lignin at the biorefinery.

Integration of wastewater treatment into process design of lignocellulosic biorefineries for improved economic viability

BACKGROUND

Production and use of bio-based products offer advantages over conventional petrochemicals, yet the relatively high cost of production has restricted their mainstream adoption. Optimization of wastewater treatment processes could reduce capital expenditures, lowering the barrier to market entry for lignocellulosic biorefineries. This paper characterizes wastewater associated with lignocellulosic ethanol production and evaluates potential wastewater treatment operations.

RESULTS

It is found that organic material is intrinsic to bioconversion wastewater, representing up to 260 kg of biological oxygen demand per tonne of feedstock processed. Inorganics in the wastewater largely originate from additions during pretreatment and pH adjustments, which increase the inorganic loading by 44 kg per tonne of feedstock processed. Adjusting the ethanol production process to decrease addition of inorganic material could reduce the demands and therefore cost of waste treatment. Various waste treatment technologies-including those that take advantage of ecosystem services provided by feedstock production-were compared in terms of capital and operating costs, as well as technical feasibility.

CONCLUSIONS

It is concluded that wastewater treatment technologies should be better integrated with conversion process design and feedstock production. Efforts to recycle resources throughout the biofuel supply chain through application of ecosystem services provided by adjacent feedstock plantations and recovery of resources from the waste stream to reduce overall capital and operating costs of bioconversion facilities.

Breeding progress and preparedness for mass-scale deployment of perennial lignocellulosic biomass crops switchgrass, miscanthus, willow and poplar

Genetic improvement through breeding is one of the key approaches to increasing biomass supply. This paper documents the breeding progress to date for four perennial biomass crops (PBCs) that have high output-input energy ratios: namely Panicum virgatum (switchgrass), species of the genera Miscanthus (miscanthus), Salix (willow) and Populus (poplar). For each crop, we report on the size of germplasm collections, the efforts to date to phenotype and genotype, the diversity available for breeding and on the scale of breeding work as indicated by number of attempted crosses. We also report on the development of faster and more precise breeding using molecular breeding techniques. Poplar is the model tree for genetic studies and is furthest ahead in terms of biological knowledge and genetic resources. Linkage maps, transgenesis and genome editing methods are now being used in commercially focused poplar breeding. These are in development in switchgrass, miscanthus and willow generating large genetic and phenotypic data sets requiring concomitant efforts in informatics to create summaries that can be accessed and used by practical breeders. Cultivars of switchgrass and miscanthus can be seed-based synthetic populations, semihybrids or clones. Willow and poplar cultivars are commercially deployed as clones. At local and regional level, the most advanced cultivars in each crop are at technology readiness levels which could be scaled to planting rates of thousands of hectares per year in about 5 years with existing commercial developers. Investment in further development of better cultivars is subject to current market failure and the long breeding cycles. We conclude that sustained public investment in breeding plays a key role in delivering future mass-scale deployment of PBCs.

Life cycle assessment of residual lignocellulosic biomass-based jet fuel with activated carbon and lignosulfonate as co-products

BACKGROUND

Bio-jet fuels are emerging as a valuable alternative to petroleum-based fuels for their potential for reducing greenhouse gas emissions and fossil fuel dependence. In this study, residual woody biomass from slash piles in the U.S. Pacific Northwest is used as a feedstock to produce iso-paraffinic kerosene, through the production of sugar and subsequent patented proprietary fermentation and upgrading. To enhance the economic viability and reduce the environmental impacts of iso-paraffinic kerosene, two co-products, activated carbon and lignosulfonate, are simultaneously produced within the same bio-refinery. A cradle-to-grave life cycle assessment (LCA) is performed for the residual woody biomass-based bio-jet fuel and compared against the cradle-to-grave LCA of petroleum-based jet fuel. This paper also discusses the differences in the environmental impacts of the residual biomass-based bio-jet fuel using two different approaches, mass allocation and system expansion, to partition the impacts between the bio-fuel and the co-products, which are produced in the bio-refinery.

RESULTS

The environmental assessment of biomass-based bio-jet fuel reveals an improvement along most critical environmental criteria, as compared to its petroleum-based counterpart. However, the results present significant differences in the environmental impact of biomass-based bio-jet fuel, based on the partitioning method adopted. The mass allocation approach shows a greater improvement along most of the environmental criteria, as compared to the system expansion approach. However, independent of the partitioning approach, the results of this study reveal that more than the EISA mandated 60% reduction in the global warming potential could be achieved by substituting petroleum-based jet fuel with residual woody biomass-based jet fuel. Converting residual woody biomass from slash piles into bio-jet fuel presents the additional benefit of avoiding the impacts of slash pile burning in the forest, which results in a net negative impact on 'Carcinogenics' and 'Respiratory effects', and substantial reduction in the 'Smog' and 'Ecotoxicity' impacts. The production of woody biomass-based bio-jet fuel, however, did not show any significant improvement in the 'Acidification' and 'Eutrophication' impact categories.

CONCLUSIONS

The study reveals that residual woody biomass recovered from slash piles represents a more sustainable alternative to petroleum for the production of jet fuel with a lower impact on global warming and local pollution. Future research should focus on the optimization of chemical processes of the bio-refinery to reduce the impacts on the 'Acidification' and 'Eutrophication' impact categories.

Well-to-wake analysis of ethanol-to-jet and sugar-to-jet pathways

BACKGROUND

To reduce the environmental impacts of the aviation sector as air traffic grows steadily, the aviation industry has paid increasing attention to bio-based alternative jet fuels (AJFs), which may provide lower life-cycle petroleum consumption and greenhouse gas (GHG) emissions than petroleum jet fuel. This study presents well-to-wake (WTWa) results for four emerging AJFs: ethanol-to-jet (ETJ) from corn and corn stover, and sugar-to-jet (STJ) from corn stover via both biological and catalytic conversion. For the ETJ pathways, two plant designs were examined: integrated (processing corn or corn stover as feedstock) and distributed (processing ethanol as feedstock). Also, three H₂ options for STJ via catalytic conversion are investigated: external H₂ from natural gas (NG) steam methane reforming (SMR), in situ H₂, and H₂ from biomass gasification.

RESULTS

Results demonstrate that the feedstock is a key factor in the WTWa GHG emissions of ETJ: corn- and corn stover-based ETJ are estimated to produce WTWa GHG emissions that are 16 and 73%, respectively, less than those of petroleum jet. As for the STJ pathways, this study shows that STJ via biological conversion could generate WTWa GHG emissions 59% below those of petroleum jet. STJ via catalytic conversion could reduce the WTWa GHG emissions by 28% with H₂ from NG SMR or 71% with H₂ from biomass gasification than those of petroleum jet. This study also examines the impacts of co-product handling methods, and shows that the WTWa GHG emissions of corn stover-based ETJ, when estimated with a displacement method, are lower by 11 g CO₂e/MJ than those estimated with an energy allocation method.

CONCLUSION

Corn- and corn stover-based ETJ as well as corn stover-based STJ show potentials to reduce WTWa GHG emissions compared to petroleum jet. Particularly, WTWa GHG emissions of STJ via catalytic conversion depend highly on the hydrogen source. On the other hand, ETJ offers unique opportunities to exploit extensive existing corn ethanol plants and infrastructure, and to provide a boost to staggering ethanol demand, which is largely being used as gasoline blendstock.

Hydrocarbon bio-jet fuel from bioconversion of poplar biomass: techno-economic assessment

BACKGROUND

Infrastructure compatible hydrocarbon biofuel proposed to qualify as renewable transportation fuel under the U.S. Energy Independence and Security Act of 2007 and Renewable Fuel Standard (RFS2) is evaluated. The process uses a hybrid poplar feedstock, which undergoes dilute acid pretreatment and enzymatic hydrolysis. Sugars are fermented to acetic acid, which undergoes conversion to ethyl acetate, ethanol, ethylene, and finally a saturated hydrocarbon end product. An unfermentable lignin stream may be burned for steam and electricity production, or gasified to produce hydrogen. During biofuel production, hydrogen gas is required and may be obtained by various methods including lignin gasification.

RESULTS

Both technical and economic aspects of the biorefinery are analyzed, with different hydrogen sources considered including steam reforming of natural gas and gasification of lignin. Cash operating costs for jet fuel production are estimated to range from 0.67 to 0.86 USD L^-1 depending on facility capacity. Minimum fuel selling prices with a 15 % discount rate are estimated to range from 1.14 to 1.79 USD L^-1. Capacities of 76, 190, and 380 million liters of jet fuel per year are investigated. Capital investments range from 356 to 1026 million USD.

CONCLUSIONS

A unique biorefinery is explored to produce a hydrocarbon biofuel with a high yield from bone dry wood of 330 L t^-1. This yield is achieved chiefly due to the use of acetogenic bacteria that do not produce carbon dioxide as a co-product during fermentation. Capital investment is significant in the biorefinery in part because hydrogen is required to produce a fully de-oxygenated fuel. Minimum selling price to achieve reasonable returns on investment is sensitive to capital financing options because of high capital costs. Various strategies, such as producing alternative, intermediate products, are investigated with the intent to reduce risk in building the proposed facility. It appears that producing and selling these intermediates may be more profitable than converting all the biomass into aviation fuel. With variability in historical petroleum prices and environmental subsidies, a high internal rate of return would be required to attract investors.