Understanding lignin’s fast pyrolysis through examination of the thermolysis mechanisms of model oligomers

The lignocellulosic biorefinery is a visionary concept that endeavors to provide an alternative to fossil-based refineries by producing biobased fungible fuels and specialty chemicals almost exclusively derived currently from petroleum refineries. This vision of the lignocellulosic biorefinery can only be realized if all fractions of lignocellulosic biomass are efficiently deconstructed and valorized to generate a diverse portfolio of products to sustain it against market vicissitudes. Of the three main structural constituents of lignocellulosic biomass (i.e., cellulose, hemicellulose, and lignin), lignin is underutilized despite being the most abundant renewable source of aromatic platform chemicals, representing a growing 250 billion dollar market. One pathway for lignin valorization includes its efficient fractionation followed by controlled deconstruction. Through the thermochemical deconstruction route, the focus of this dissertation project, greater understanding of the thermal deconstruction or depolymerization reactions and their associated kinetics is necessary to control competing reaction pathways to improve selectivity toward desirable products and increase yields. In this project, we seek to deepen our mechanistic understanding of the prevalent reaction pathways during the thermal deconstruction of lignin by computationally and experimentally investigating model lignin oligomers with important linkages found in lignin. Insight of the thermal deconstruction pathways of oligomeric lignin fragments with diverse linkages is a key missing piece of the puzzle required to develop fuller and generalizable lignin thermal deconstruction mechanisms. We will employ density functional theory (DFT), a computational quantum chemistry investigative tool, to assess the reactivity of a combination of important lignin linkages in the model oligomers. We will then experimentally pyrolyze commercially available model compounds with closely related to the model compounds used in the DFT investigation using a pulse heated pyrolysis reactor (PHPR) system developed for this project. The PHPR system overcomes transport limitations found in commercial pyroprobe systems used in milligram-scale biomass pyrolysis studies. We will use this system to identify major products and intermediates and validate the results obtained from the computational calculations. The computational and experimental findings will be used to identifying general reactivity trends between the major interunit linkages of lignin and propose and validate reaction mechanisms and kinetics for each model oligomer

Computational Fluid Dynamic Modeling of Catalytic Hydrous Pyrolysis of Biomass to Produce Refinery-Ready Bio-Crude Oil

The growing world population continually increases the demand for energy. Currently, the main source of energy production is fossil fuels, which are harmful to the environment and are finite. An exploration of renewable energy to supplement or replace fossil fuels is of great importance. Modern techniques for producing renewable bio-oil consist of converting biomass into bio-oil through pyrolysis, but unfortunately, pyrolysis oil has quality issues (e.g., high oxygen content, viscosity, chemical instability). Therefore, upgrading is necessary to improve quality. Hydropyrolysis is a state of the art technique to deoxygenate bio-oil during pyrolysis to produce petroleum quality bio-oil. A major issue with hydropyrolysis is the expensive cost of hydrogen.This project aimed to computationally model the hydrous pyrolysis of biomass coupled with an in-situ hydrogen generation process. The kinetics of the water-gas shift (WGS) were determined experimentally and modeled using an ordinary differential equation subroutine coupled with a nonlinear regression. A computational fluid dynamic (CFD) model of biomass fast pyrolysis was developed to simulate conventional fast pyrolysis. The final part of this project adapted the CFD model to simulate hydrous pyrolysis and incorporate the determined WGS kinetics. The bio-oil was deoxygenated via a global lumped hydrodeoxygenation (HDO) kinetic scheme.This WGS was determined to have an agreement with both an empirical power law and a Langmuir-Hinselwood mechanism at conditions similar to that of pyrolysis. The CO conversion reached a maximum value of 94% at higher temps and larger amounts of catalyst. The CFD model of fast pyrolysis predicted a maximum bio-oil yield of 47%, but significantly under-predicted the amount of water present in the oil. The hydrous pyrolysis simulations have not yet reached steady-state and the HDO reactions are just beginning to take place. Further work is needed to explore more detailed kinetic schemes for the secondary pyrolysis reactions as well as the hydrodeoxygenation kinetics

Widespread adoption of genetic technologies is a key to sustainable expansion of global aquaculture

Aquaculture production comprises a diverse range of species, geographies, and farming systems. The application of genetics and breeding technologies towards improved production is highly variable, ranging from the use of wild-sourced seed through to advanced family breeding programmes augmented by genomic techniques. This technical variation exists across some of the most highly produced species globally, with several of the top ten global species by volume generally lacking well-managed breeding programmes. Given the well-documented incremental and cumulative benefits of genetic improvement on production, this is a major missed opportunity. This short review focusses on (i) the status of application of selective breeding in the world’s most produced aquaculture species, (ii) the range of genetic technologies available and the opportunities they present, and (iii) a future outlook towards realising the potential contribution of genetic technologies to aquaculture sustainability and global food security

Future directions in breeding for disease resistance in aquaculture species

ABSTRACT Infectious disease is a major constraint for all species produced via aquaculture. The majority of farmed fish and shellfish production is based on stocks with limited or no selective breeding. Since disease resistance is almost universally heritable, there is huge potential to select for improved resistance to key diseases. This short review discusses the current methods of breeding more resistant aquaculture stocks, with success stories and current bottlenecks highlighted. The current implementation of genomic selection in breeding for disease resistance and routes to wider-scale implementation and improvement in aquaculture are discussed. Future directions are highlighted, including the potential of genome editing tools for mapping causative variation underlying disease resistance traits and for breeding aquaculture animals with enhanced resistance to disease

Zombie Apocalypse: Engaging Students In Environmental Health And Increasing Scientific Literacy Through The Use Of Cultural Hooks And Authentic Challenge Based Learning Strategies

Environmental Health (EH) is an essential profession for protecting human health and yet as a discipline it is under-recognised, overlooked and misunderstood. Too few students undertake EH studies, culminating in a dearth of qualified Environmental Health Officers (EHOs) in Australia. A major deterrent to students enrolling in EH courses is a lack of appreciation of the relevance to their own lives. This is symptomatic of a wider problem of scientific literacy: the relevance gap and how to bridge it. Employing a cultural hook offers a means to connect students to science and the fundamental elements of EH. Zombies feature prominently in the contemporary cultural landscape – movies, TV, gaming, music, cosplay, ‘Zombie Marches’. A Zombie Apocalypse provides an engaging platform to convey key EH concepts such as microbes and toxins, whilst improving the scientific literacy skills of both science and non-science students. Engaging students through this cultural hook bridged the relevance gap, connected students to science, and inspired an increased interest in EH

Genome-Wide Association and Genomic Selection for Resistance to Amoebic Gill Disease in Atlantic Salmon

Abstract Amoebic gill disease (AGD) is one of the largest threats to salmon aquaculture, causing serious economic and animal welfare burden. Treatments can be expensive and environmentally damaging, hence the need for alternative strategies. Breeding for disease resistance can contribute to prevention and control of AGD, providing long-term cumulative benefits in selected stocks. The use of genomic selection can expedite selection for disease resistance due to improved accuracy compared to pedigree-based approaches. The aim of this work was to quantify and characterize genetic variation in AGD resistance in salmon, the genetic architecture of the trait, and the potential of genomic selection to contribute to disease control. An AGD challenge was performed in ∼1,500 Atlantic salmon, using gill damage and amoebic load as indicator traits for host resistance. Both traits are heritable (h2 ∼0.25-0.30) and show high positive correlation, indicating they may be good measurements of host resistance to AGD. While the genetic architecture of resistance appeared to be largely polygenic in nature, two regions on chromosome 18 showed suggestive association with both AGD resistance traits. Using a cross-validation approach, genomic prediction accuracy was up to 18% higher than that obtained using pedigree, and a reduction in marker density to ∼2,000 SNPs was sufficient to obtain accuracies similar to those obtained using the whole dataset. This study indicates that resistance to AGD is a suitable trait for genomic selection, and the addition of this trait to Atlantic salmon breeding programs can lead to more resistant stocks.</jats:p