• Energy Research

Biofuels from lignocellulosic biomass converted via thermochemical technologies can be renewable and sustainable, which makes them promising as alternatives to conventional fossil fuels. Prior to building industrial-scale thermochemical conversion plants, computational models are used to simulate process flows and conditions, conduct feasibility studies, and analyse process and business risk. This paper aims to provide an overview of the current state of the art in modelling thermochemical conversion of lignocellulosic biomass. Emphasis is given to the recent advances in artificial intelligence (AI)-based modelling that plays an increasingly important role in enhancing the performance of the models. This review shows that AI-based models offer prominent accuracy compared to thermodynamic equilibrium modelling implemented in some models. It is also evident that gasification and pyrolysis models are more matured than thermal liquefaction for lignocelluloses. Additionally, the knowledge gained and future directions in the applications of simulation and AI in process modelling are explored.

Various biocrudes were characterised by their distillation curves using simulated distillation. Biocrude and petroleum crude blends were generated and analysed to assess their compatibility for processing in conventional petroleum refineries. Distillation curves of biocrudes varied widely but were comparable to petroleum crude oil in shape and distillation range. Blending biocrude with petroleum crudes in the laboratory presented some challenges in miscibility; however, blending at higher than ambient temperatures, which more closely represents industrial practice, improved miscibility as shown in the FTIR spectra of blends, and close matching of the warmer blends to models. The distillation curve of the biocrude-petroleum crude blends followed the modelled blends in ASPEN Plus. Petroleum analysis and modelling methods were also demonstrated as reliable tools to analyse biocrudes and their blends with petroleum crude. The study verifies ASPEN’s utility in modelling biocrude distillation for processing in refinery distillation columns either as a blend or separately.

Abstract Generating green-based liquid fuels using hydrothermal liquefaction is a promising method for fossil fuel replacement. This study investigates the impact of recycling the aqueous phase in hydrothermal liquefaction processing on fuel yield, quality and energy efficiency using algae as the feedstock. Recycling the aqueous phase in algal hydrothermal liquefaction increased biocrude production yield by 18.9% at 350 °C, although a 12.2% increase in the biocrude nitrogen content was observed. In the second recycling, the nitrogen content increased to 17.6%, which is not environmentally favourable for direct usage in diesel engines due to the possible increase in Nitrogen Oxides (NOx) emissions. Recycling the aqueous phase in Spirulina Platensis feedstock liquefaction led to a 19–30% increase in yields for different recycling numbers, which was influenced by increasing the temperature and by applying catalysts. The heterogeneous catalyst showed a considerable increase (17.8%) in yield, a decrease (9.5%) in nitrogen content, and an improved energy consumption recovery by 30.8% after single recycling. However, a slight increase (2.7%) in nitrogen content was observed after recycling twice. It is vital to reduce the amount of energy used in the hydrothermal liquefaction process to be comparable with conventional fuels. Recycling the aqueous phase reduced the energy usage considerably. Applying the homogeneous catalyst and recycling the aqueous phase twice had the highest energy efficiency (36.8%) and production yield (51.4%) for the hydrothermal liquefaction process. The generated aqueous phase in single and double recycling experiments had up to 77% and 166% more phosphate, which may be of interest for agricultural applications.

Abstract Hydrothermal liquefaction (HTL) biocrude is a promising source of energy with potential for co-processing with conventional fuels or as a drop-in fuel. However, it needs upgrading to reduce heteroatoms (e.g., N, S, O), improve physical properties, stability, and miscibility with hydrocarbons. Distillation is a conventional physical upgrading method that has not been studied extensively for biocrude using an industry-accepted procedure on a large scale. In this study, an algae-based biocrude was distilled into four fractions using ASTM D2892 standard method: Fraction 1 (

Hydrothermal liquefaction (HTL) presents a viable route for converting a vast range of materials into liquid fuel, without the need for pre-drying. Currently, HTL studies produce bio-crude with properties that fall short of diesel or biodiesel standards. Upgrading bio-crude improves the physical and chemical properties to produce a fuel corresponding to diesel or biodiesel. Properties such as viscosity, density, heating value, oxygen, nitrogen and sulphur content, and chemical composition can be modified towards meeting fuel standards using strategies such as solvent extraction, distillation, hydrodeoxygenation and catalytic cracking. This article presents a review of the upgrading technologies available, and how they might be used to make HTL bio-crude into a transportation fuel that meets current fuel property standards.

This study presents an overview of the context and global impacts of recent International Maritime Organization (IMO) regulations on the marine fuel oil refining industry, future marine fuel mix and ship emissions. IMO limited marine fuel sulphur content in both Sulphur Emission Control Areas (SECAs) and Nitrogen Oxide Emission Control Areas (NECAs) to 0.1% (wt. %) by 2015, and to 0.5% globally by 2020. It is anticipated that the newly implemented IMO regulations will help to mitigate negative impact of ship emissions on public health and environment. IMO regulations require significant changes to refineries to increase the production of low sulphur fuels through a shift to distillates, use of novel deep desulphurization techniques, or fuel blending. Changes to the refinery processes can bring forth increases in greenhouse gas emissions and high capital investments. Alternative fuels will need to meet the required reduction of air pollutants and greenhouse gas emissions in coastal areas. Alternative marine fuels consisting of liquefied nature gas (LNG) and biofuel may be suitable fuels to meet both targets. These two fuels are predicted to account for 50% of shipping energy demand by 2050, while the remainder will still be supplied by conventional heavy fuel oil (HFO)/marine gas oil (MGO). Switching to low sulphur fuels as a results of the new IMO regulations has led to measureable reductions in ship emissions generally. This fuel switching also resulted in changes in engine emission characteristics, especially on particulate matter chemical composition.

Thermal liquefaction of five potential feedstocks namely, banana bunch stems (BBS), pineapple tops (PT), Forage sorghum (FS), bagasse (Ba) and Arundo donax (AD) were examined from an energy perspective at a large laboratory scale.

For a cleaner and healthier planet, industries must decarbonize and move away from ‘take-make-waste’ linear economies to circular economies, in ways that maximize value and minimize negative environmental impact. Anaerobic digestion (AD) is a well-known technology used to process domestic and industrial wastes to produce biogas (mainly CH4) but with large volumes of high moisture content digestate as by-product The digestate is both difficult and expensive to manage, often requiring more than half the operating cost of treatment plants. Hydrothermal gasification (HTG) can convert the recalcitrant digestate into renewable gases including CH4. So, for high carbon conversion a hybrid AD and HTG technology is an attractive solution. In the hybrid process, AD can be used to treat the wet biomass (an existing practice), and the liquid AD digestate can then be processed by HTG to optimize CH4 yield. This paper reviews the pros and cons of the AD and HTG processes, examines the valorization of co-products, and assesses the potential of the hybrid process with additional information from other AD-thermochemical process hybrids that have widely reported economic feasibilities.