Concrete production and municipal solid waste management contribute up to 13% of global CO2 emissions. Here, we describe Hydrothermal Oxidation and Mineralization (HTOM) as a new process for production of alternative construction material (ACM) with a compressive strength (9.23 +/- 0.98 MPa) more than double what is required for non-loadbearing concrete (4.14 MPa) while storing CO2. HTOM consists of two oxidative reactions: (1) supercritical water oxidation (SCWO) converts the organic fraction of food waste to a high-pressure CO2 stream while producing thermal bioenergy that can be recovered using a turbine, then (2) the high-pressure CO2 stream is used for rapid mineralization of soluble calcium to calcium carbonate, reaching 100% conversion within 20 minutes. ASPEN/HYSYS simulations and a GREET lifecycle analysis demonstrate that HTOM has the potential to offset 0.1 kg of CO2 per kg of ACM produced by simultaneously diverting fugitive landfill emissions, capturing waste energy, and offsetting traditionally CO2-intensive concrete mortar production.

Hydrothermal liquefaction (HTL) is a waste agnostic process that leverages near-critical water to break down macromolecules, forming an energy-dense biocrude. Some carbon contained in the waste feed is lost in the aqueous phase, where its high organic content and unusual speciation are burdensome for municipal wastewater resource recovery facilities (WRRF). Treating the aqueous phase adds undesirable cost to the HTL process, reducing its attractiveness. Here, we report aqueous phase supercritical upgrading (AP-SCU) as a new catalytic aqueous phase upgrading technology that reduces the organic content of the aqueous phase with co-production of supplemental biocrude. The supercritical phase provides sufficient catalyst activity for organic conversion, reduces energy inefficiency by eliminating the need for evaporation, and extends the catalyst lifetime relative to the liquid state. AP-SCU was evaluated at 380–440°C at 24 MPa for a representative HTL aqueous phase produced from the treatment of food waste. Using a ZSM-5 catalyst bound with silica sol, the aqueous carbon content was reduced by 64%–73% with a corresponding production of aromatic hydrocarbons including phenol and 2-pentanone. The total nitrogen was reduced by approximately 10%. Additionally, the ZSM-5 facilitated reduction and denitrogenation reactions of aqueous phase compounds to produce aromatic and pyridine compounds which more closely resemble HTL biocrude. After 3 h on stream, the catalyst experienced coke formation, and surface degradation which led to a reduction in acid sites and surface area. The carbon balance for the system was closed through the analysis of the aqueous, solid, and gas phases to estimate that biocrude yield varies from 43%–57% on a carbon basis. An energy balance for HTL process with integrated AP-SCU system showed that operating the AP-SCU unit at 380°C yielded the minimum energy demand for carbon removal at 63 MJ/kg-TOC. This value is greater than the energy demand for conventional WRRFs (37.9 MJ/kg-TOC) but is more than 10-times less than emerging technologies which are designed to handle complex feeds. AP-SCU has potential as an energy efficient and effective new technology for reducing the TOC of the aqueous phase with simultaneous production of supplemental biocrude to offset energy demand.

Current solutions to global challenges place tension between global benefits and local impacts. The result is increasing opposition to implementation of beneficial climate policies. Prioritizing investment in projects with tangible local benefits that also contribute to global climate change can resolve this tension and make local communities’ partners instead of antagonists to change; the approach advocated is a new take on “thinking globally, acting locally”. This approach is a departure from the usual strategy of focusing resources on solutions perceived to have the largest potential global impact, without regards to local concerns. Reclamation of polluted mine sites by using fast growing bamboo to remove heavy metals provides a case study to show what is possible. Effective implementation of thinking globally while acting locally will require increased coordination between different types of researchers, new educational models, and greater stakeholder participation in problem identification and solution development.

Less than 5% of polystyrene is recycled, motivating a search for energy efficient and economical methods for polystyrene recycling that can be deployed at scale. One option is chemical recycling, consisting of thermal depolymerization and purification to produce monomer-grade styrene (>99%) and other co-products. Thermal depolymerization and distillation are readily scalable, well-established technologies; however, to be considered practical, they must be thermodynamically efficient, economically feasible, and environmentally responsible. Accordingly, mass and energy balances of a pyrolysis reactor for thermal depolymerization and two distillation columns to separate styrene from alpha-methyl styrene, styrene dimer, toluene, and ethyl benzene co-products, were simulated using ASPEN to evaluate thermodynamic and economic feasibility. These simulations indicate that monomer-grade styrene can be recovered with energy inputs <10MJ/kg, comparable to the energy content of pyrolysis co-products. Thermodynamic sensitivity analysis indicates the scope to reduce these values and enhance the robustness of the predictions. A probabilistic economic analysis of multiple scenarios combined with detailed sensitivity analysis indicates that the cost for recycled styrene is approximately twice the historical market value of fossil-derived styrene when styrene costs are fixed at 15% of the total product cost or less than the historical value when feedstock costs are assumed to be zero. A Monte Carlo and Net Present Value-based economic performance analysis indicates that chemical recycling is economically viable for scenarios assuming realistic feedstock costs. Furthermore, the CO2 abatement cost is roughly $1.5 per ton of averted CO2, relative to a pyrolysis process system to produce fuels. As much as 60% of all polystyrene used today could be replaced by chemically recycled styrene, thus quantifying the potential benefits of this readily scalable approach.

This study advances the fundamental understanding of the correlation between lignin structure and reactivity during hydrothermal liquefaction (HTL). Five different lignin varieties were obtained using the cosolvent enhanced lignin fraction (CELF) pretreatment; lignin sources were selected to represent a range of lignin types including softwood (pine), hardwood (poplar and maple), and agricultural (bagasse and corn stover) feeds and analyzed using conventional methods and new developed advanced solid-state 13C NMR (ssNMR) approaches. Molecular weight, relative quantities of syringol (S), guaiacol (G), and p-hydroxyphenyl monomers, as well as degree of condensation (DC) were measured for the lignin samples, providing a quantitative basis for structure-reactivity relationships. These lignin samples then underwent HTL at 300 degrees C for 1 h, and the resulting biocrude, water soluble, char, and gas products were quantified. Lignin properties were correlated to HTL yields and biocrude composition, which found feedstock S/G ratio as the strongest predictor of biocrude and char yields, followed closely by DC. Ultrahigh resolution mass spectrometry analysis of the biocrude was used to gain mechanistic insights into lignin reactivity during HTL, finding that biocrude consists of oligomers of lignin subunits composed of 2-5 monomers. The biocrude obtained from high S content lignin is enriched in dimers and trimers, explaining the high biocrude yields obtained from these feeds compared with low S content lignin. These insights significantly advance current understanding of lignin reactivity under hydrothermal conditions.

Modeling complex chemical reactions is a long-standing challenge in chemical reaction engineering. Group type analysis is commonly used for reducing the complexity of the reaction model while retaining sufficient chemical information for a particular application. This study evaluates a data-driven approach based on mathematical similarity as a new tool for identification of groups for use in group type reaction models. Data for dodecane cracking in the supercritical state over Zeolite Socony Mobil-5 (ZSM-5) was used as a test system. Mathematical similarity analysis of the raw data differentiated as many as five different groups. Adding synthetic data did not affect the groups identified by similarity analysis, indicating that the separation was not limited by the number of data points. Scaling or normalizing the data improved the separation of the similarity analysis. To test the data-identified groups, different types of reaction models were generated systematically, kinetic parameters regressed, and the resulting predictions compared with experimental data. The resulting reaction models consisted either of parallel or sequential reactions. As a general statement, the reaction models consisting of parallel reactions were more accurate than those consisting of sequential reactions. Additional tests showed that user defined groups could be added to those identified mathematically to improve the accuracy of predictions for target species without sacrificing overall accuracy. The similarity approach was applied to a data set consisting of catalytic dodecane cracking in the presence of water added to the reaction mixture (50 wt %). The proposed similarity analysis identified different groups in the presence and absence of water, indicating that the data-driven approach can be used to identify qualitative differences in the reaction pathways. It is therefore demonstrated that data-driven identification of group types represents a useful new tool for development of group type models.

Hydrothermal liquefaction (HTL) has remarkable potential for efficient conversion of abundant, decentralized organic wastes into renewable fuels. Because waste is a highly distributed resource with context-dependent economic viability, selection of optimal deployment sites is slowed by the need to develop detailed technoeconomic analyses (TEA) for the thousands of potential deployment locations, each with their own unique combinates of scale, proximity to infrastructure/markets, and feedstock properties. An economic modeling framework that requires only easily obtainable inputs for assessing economic performance would therefore allow multiplexed analysis of many thousands of cases, whereas traditional TEA would not be possible for more than a handful of cases. Within such a context, the present study uses machine learning to guide development of a TEA and modeling framework which provides accurate cost predictions using three key inputs - feedstock cost, biocrude yield, and process scale - to estimate the minimum fuel selling price (MFSP) that an HTL process can achieve. The structure of the proposed framework is informed and based on empirical observations of cost projections made by a detailed TEA over a wide range of feedstock costs, biocrude yields, and process scales. A machine learning guided process was used to identify, train, and test a series of models using auto-generated data for training and independently reported data for testing. The most accurate model consists of three terms and requires 6 adjustable parameters to predict independently published values of MFSP (N N = 28) to within an average value of +/- 20.4%. It is demonstrated that the reduced-order model's predictions fall within 40% of the corresponding published values 95% of the time, and in the worst case, the associated discrepancy is 45.9%, suggesting that the accuracy of the machine learned model is indeed comparable to the TEAs that were used to build it. Moreover, the terms in the model are physically interpretable, conferring greater reliability to the use of its predictions. The model can be used to predict the dependence of MSFP on biocrude yield, scale, and feedstock cost; interestingly, MFSP is insensitive to biocrude yield and/or scale under many situations of interest and identifying the critical value for a given application is crucial to optimizing economic performance. The proposed model can be also extended to evaluate economic performance of newly developed HTL-based processes, including catalytic HTL, and the methodological framework used in this study is deemed appropriate for the development of machine learned TEA models in cases of other similar waste-to-energy technologies.

We have investigated ozone treatment of as-made LTA zeolites under mild temperature conditions (175 degrees C) using experiments and periodic DFT as a method of energy savings and engineering defects such as silanol nests in comparison with conventional calcination at 550 degrees C. We have studied ozone treatment on LTA samples synthesized with 1,2-dimethyl-3-(4-methylbenzyl) imidazolium (denoted as "BULKY") as the primary organic structure-directing agent (OSDA) and with various amounts of tetramethylammonium (TMA) as a secondary OSDA. Ozone treatment of LTA-BULKY at 175 degrees C was found to give defect-free, pristine LTA materials as determined by Si-29 NMR, C-13 NMR, Raman spectra, and DFT to assign the spectra. This represents a significant and unexpected finding: that fluoride ions can be completely removed from double four-membered rings (D4Rs) under such mild conditions. Ozone treatment of LTA-BULKY-TMA samples removed BULKY but left behind TMA/F, giving a new and more diverse structural landscape of Si environments in LTA. Ab initio MetaDynamics calculations provide pathways with relatively low barriers, explaining how fluoride ions can be removed from D4Rs, leaving behind defect-free LTA materials under mild conditions.

The molecular structure of hydrochars produced from 13C-enriched glucose under various conditions has been elucidated based on advanced one- and two-dimensional (2D) 1H-13C and 13C-13C solid-state nuclear magnetic resonance (NMR) with spectral editing. Regardless of synthesis conditions, hydrochars consist mostly of oxygensubstituted arene rings (including diphenols) and furans connected by alkyl linkers rich in ketones. Cross-linking nonprotonated and methyne (C-H) alkyl carbons have been identified through spectrally edited 2D NMR. Alkenes and 'quaternary' C-O are observed only at low synthesis temperature, while some clusters of fused arene rings are generated at high temperature. Hydrochar composition is nearly independent of reaction time in the range from 1 to 5 h. Equilibration of 13C magnetization within 1 s shows that the materials are homogeneous on the 5-nm scale, refuting core-shell models of hydrochar microspheres. While furan C-O carbons bonded to alkyl groups or ketones show distinctive cross peaks in 2D NMR, phenolic C-OH is observed unambiguously by hydroxyl-proton selection. While methylene-linked furan rings are fairly common, the signal previously assigned to furan C alpha-C alpha linkages is shown to arise from abundant, stable catecholic ortho-diphenols, whose HO-C=C-OH structure is proved by 2D13C-13C NMR after hydroxyl-proton selection. Quantitative 13C NMR spectra of low- and hightemperature hydrochars have been matched by chemical-shift simulations for representative structural models. Mixed phenol and furan rings connected by ketones and alkyl linkers provide good fits of the experimental spectra, while literature models dominated by large clusters of fused rings and with few phenols or alkyllinked ketones do not.

During the process of subcritical water hydrolysis of lignocellulosic compounds, such as brewers' spent grains, some toxic compounds can be formed due to the breakdown of the cellulose structure. These compounds are known as furanic aldehydes, and they are inhibitors of microorganisms that are used in different processes, such as fermentation and anaerobic digestion, among others. The detoxification and conditioning of these hydrolysates are required before their use in other processes that require low concentrations of toxins. One of the mechanisms that can be used to diminish those compounds is the adsorption process. For this reason, this study evaluated at-line and in-line purification strategies using different adsorbents in fixed-bed columns to remove furanic aldehydes from a model feed simulating hydrolysate from subcritical water hydrolysis. The model feed consisted of simple sugars and furanic aldehydes at appropriate concentrations. The selected adsorbents were silica-C18, hydrocarbons, and activated carbon. The results indicate that, among the adsorbents that were studied, activated carbon was the most efficient for the removal of both 5-hydroxymethylfurfural and furfural. The activated carbon removed >99% of furanic aldehydes in the experiments conducted in the at-line system. Sequential subcritical water hydrolysis followed by either at-line or in-line purification is promising for integrated inexpensive and efficient hydrolysate purification.

Abstract MF-LOGP, a new method for determining a single component octanol–water partition coefficients ( $$LogP$$ LogP ) is presented which uses molecular formula as the only input. Octanol–water partition coefficients are useful in many applications, ranging from environmental fate and drug delivery. Currently, partition coefficients are either experimentally measured or predicted as a function of structural fragments, topological descriptors, or thermodynamic properties known or calculated from precise molecular structures. The MF-LOGP method presented here differs from classical methods as it does not require any structural information and uses molecular formula as the sole model input. MF-LOGP is therefore useful for situations in which the structure is unknown or where the use of a low dimensional, easily automatable, and computationally inexpensive calculations is required. MF-LOGP is a random forest algorithm that is trained and tested on 15,377 data points, using 10 features derived from the molecular formula to make $$LogP$$ LogP predictions. Using an independent validation set of 2713 data points, MF-LOGP was found to have an average $$RMSE$$ RMSE = 0.77 ± 0.007, $$MAE$$ MAE = 0.52 ± 0.003, and $${R}^{2}$$ R 2 = 0.83 ± 0.003. This performance fell within the spectrum of performances reported in the published literature for conventional higher dimensional models ( $$RMSE$$ RMSE = 0.42–1.54, $$MAE$$ MAE = 0.09–1.07, and $${R}^{2}$$ R 2 = 0.32–0.95). Compared with existing models, MF-LOGP requires a maximum of ten features and no structural information, thereby providing a practical and yet predictive tool. The development of MF-LOGP provides the groundwork for development of more physical prediction models leveraging big data analytical methods or complex multicomponent mixtures. Graphical Abstract

The development of novel and sustainable bioprocesses for the valorization of agri-food by-products is required for the food industry to transition to a circular economy. The objective of this study to evaluate a sequential process consisting of fed-batch pretreatment followed by semi-continuous anaerobic digestion of brewer's spent grains for the production of biomethane and bioenergy. Anaerobic digestion was conducted under mesophilic and methanogenic conditions, and the digestate and corresponding biogas were characterized to determine the process efficiency. Experimental results indicate that the fed-batch pretreatment improves the biogas production obtained from the semi-continuous process. The methane yield during the fed-batch pretreatment was 11.89 L CH4/kg TVSadded, while in the semi-continuous process, the yield was 30.61 L CH4/kg TVSadded. The biogas produced in the semi-continuous process could generate electricity (66.9 kWh/t) and heat (316.75 MJ/t), avoiding greenhouse gas emissions (20.81 kg CO2eq/t). Implementing the novel anaerobic digestion system could be a promising approach for the valorization of brewery by-products, producing renewable energy from biomass.

β-glucan is the major component of the extracellular matrix (ECM) of many fungi, including wood degrading fungi. Many of these species also secrete oxalate into the ECM. Our research demonstrates that β-glucan forms a novel, previously unreported, hydrogel at room temperature with oxalate. Oxalate was found to alter the rheometric properties of the β-glucan hydrogels, and modeling showed that β-glucan hydrogen bonds with oxalate in a non-covalent matrix. Change of oxalate concentration also impacted the diffusion of a high-molecular-weight protein through the gels. This finding has relevance to the diffusion of extracellular enzymes into substrates and helps to explain why some types of wood-decay fungi rely on non-enzymatic degradation schemes for carbon cycling. Further, this research has potential impact on the diffusion of metabolites in association with pathogenic/biomedical fungi.

Low- and middle-income countries have tremendous potential for renewable energy production, including production of renewable carbon from locally prolific crops. In this work, bamboo endemic to West Africa (Bambusa vulgaris) was studied as a feedstock for the production of renewable sugars as the gateway to the local production of biofuels and bio-based chemical products. The effectiveness of delignification and amorphization pretreatments was evaluated, with the observation that quantitative (97 ± 4%) sugar yields could be obtained with a rapid initial hydrolysis rate (82 ± 4 mg g−1 h−1) but only when amorphization was performed following delignification. Experimental measurements and further characterization using 13C solid state nuclear magnetic resonance (NMR) helped establish the importance of amorphization and delignification and explained why the order of these treatments determined their effectiveness. The economics of the bamboo-based process were compared with those projected for corn stover, selected as a well-studied benchmark crop. Because of the higher bamboo growth rate compared with corn stover and the effectiveness of the pretreatment, the projected net present value (NPV) of the bamboo biorefinery was positive ($190 MM, U.S.), whereas the corn biorefinery projected to negative NPV (−$430 MM, U.S.). A socially sustainable framework for deployment of a bamboo biorefinery in a low- or middle-income economy was then proposed, guided by the principle of local ownership and stakeholder buy-in. The findings presented here motivate further investment in development of bamboo cultivation and conversion to sugars as a rapid route to decarbonization of low- and middle-income economies.

In this study, four geopolymer sorbents GP0, GP10, GP30 and GP50 were synthesized using volcanic ash (VA) and metakaolin (MK) blends as precursors with 0, 10, 30 and 50% MK content by mass, respectively. The materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analyses, revealing successful geopolymerization of the precursors and increasing surface area with increasing MK content. The sorption performance of the VA, MK and VA-MK geopolymers was then evaluated for the removal of cationic methylene blue (MB) dye from aqueous media. Sorption capacity was independent of composition, providing flexibility in sorbent synthesis. Sorption rate, on the other hand, was 3–8 times greater for the VA-MK geopolymers than the precursor materials. The equilibrium adsorption data were suitably explained by the Freundlich model, denoting multilayer adsorption onto a heterogeneous adsorption surface with higher Freundlich affinity constant (K F ) for geopolymers than VA. The adsorption kinetics obeyed the pseudo-second-order (PSO) kinetic law with an average of 98% removal efficiency in 30 min. MB uptake was pH-dependent and driven by electrostatic chemisorption interactions. These results motivate further studies on the use of locally sourced geopolymers for water purification applications.

Hydrothermal liquefaction (HTL) is a promising strategy for conversion of energy-dense waste streams to fuels. Mixed-feed HTL aggregates multiple feed streams to achieve greater scales that capitalize on local resources, hence lowering costs. The potential for new pathways and products upon feedstock blending becomes a compounding level of complexity when unlocking emergent chemistries. Food and green waste streams were evaluated under HTL conditions (300 °C, 1 hr) to understand the effect of feed molecular composition on product distributions and mechanisms. Thousands of emergent chemical compounds were detected via FT-ICR MS, ultimately leading to the emergence of two dominant outcomes. First, the presence of small amounts of food waste into green waste results in substantial decarboxylation and subsequent polymerization to biocrude then chars. Second, in the other limit, small amounts of green waste promote capping of oxygenates into the biodiesel range, such as with the emergence of fatty acid methyl esters.

ZSM-5 was evaluated for chemical production in a reaction mixture consisting of palmitic acid and water at conditions near the critical point of water (400 degrees C, 23 +/- 2 MPa). Two types of ZSM-5, a microscale variety with particle diameters determined by scanning electron microscopy in the range from 1.66 to 2.56 mu m (micro-ZSM-5) and a nanoscale variety with 350-730 nm diameters (nano-ZSM-5), and three water loadings (0, 15, and 65 wt %) were evaluated for their effects on conversion and product selectivity. Palmitic acid conversion and yields of one-ring aromatics, including toluene and xylenes, were greatest for the combination of nano-ZSM-5 and 15 wt % water loadings, showing that reducing particle size and optimizing water content help achieve desired reaction outcomes. Subsequently, the use of nano-ZSM-5 combined with 15 wt % water loading was studied in greater detail, finding that the catalyst could be reused up to four times at these conditions without reduction of aromatic yields and while retaining a fraction of the original acid sites. Time-resolved studies and molecular-level analysis using two-dimensional gas chromatography and isotopic resolution mass spectrometry provided information on the reaction pathway, which consists of a combination of homogeneous and heterogeneous steps. The results of this study motivate future work on water-promoted catalytic cracking of oils to produce valuable chemicals.

Reducing chain ends in various hydrolyzed cellulose samples were quantitatively analyzed by solid-state 13C NMR. Cellulose di- and tetramers served as model systems to demonstrate that distinct signals at 97 ppm and 92.7 ppm can be detected quantitatively and assigned unambiguously to reducing chain ends in β and α anomers, respectively. In standard Avicel microcrystalline cellulose, the same signals were detected at the expected low intensity; their strength increased significantly upon further hydrolysis. The assignment of the 97 and 92.7 ppm signals to reducing chain ends was confirmed by their absence after ethanolysis, which instead produced an α-ethyl-ether end group signal at 99 ppm. Due to moderate-amplitude chain-end mobility, chain-end signals were relatively enhanced in direct-polarization 13C NMR with heteronuclear Overhauser enhancement. In 13C-enriched hydrolyzed cellulose, the assignment of the C–OH chain-end signals was further corroborated by hydroxyl-proton selection and two-dimensional 13C-13C NMR. From the fractional chain-end signal intensity, the number-average degree of polymerization (DPn) was determined. For Avicel, this yielded DPn = 43 (+ 50, -6), consistent with gel-permeation chromatography but significantly lower than deduced from a more indirect optical method likely hampered by limited chain-end accessibility. After 60 min of hydrolysis of ball-milled Avicel or cellulose from maize, highly reliable values of DPn = 18 ± 3 and 15 ± 3, respectively, were obtained. Solid-state NMR completely avoids the potential loss of low-molar-mass chains in solution-based approaches. The accurate, solvent-free solid-state NMR method introduced here can serve as a primary standard to calibrate other methods for molar-mass determination in hydrolyzed cellulose.

This study assessed the subcritical water hydrolysis (SWH) of poultry feathers to recover amino acids. Experiments were conducted in a semi-continuous flow-through subcritical reactor (110 mL), which was operated over a range of temperatures (210-250 degrees C) and water flow rates (5-15 mL min-1), combined through a 22 central composite design, at constant feed (10 g) and pressure (15 oa). The results demonstrated that non-essential and essential amino acids were obtained from SWH of poultry feathers. The highest hydrolysis temperature resulted in the highest concentrations of valine, methionine, tryptophan, phenylalanine, isoleucine, leucine, and lysine. Otherwise, threonine, histidine, and arginine were obtained more effectively at lower temperatures. The response surface methodology was adopted to identify the best conditions for amino acid production, and it was possible to identify the ranges of temperatures and water flow rates to be used to recover specific amino acids. This study allowed concluding that SWH is a promising eco-friendly technology to recover amino acids from protein-rich wastes.