Patrick Biller

Potential yields and properties of oil from the hydrothermal liquefaction of microalgae with different biochemical content

A range of model biochemical components, microalgae and cyanobacteria with different biochemical contents have been liquefied under hydrothermal conditions at 350 °C, ∼200 bar in water, 1M Na(2)CO(3) and 1M formic acid. The model compounds include albumin and a soya protein, starch and glucose, the triglyceride from sunflower oil and two amino acids. Microalgae include Chlorella vulgaris,Nannochloropsis occulata and Porphyridium cruentum and the cyanobacteria Spirulina. The yields and product distribution obtained for each model compound have been used to predict the behaviour of microalgae with different biochemical composition and have been validated using microalgae and cyanobacteria. Broad agreement is reached between predictive yields and actual yields for the microalgae based on their biochemical composition. The yields of bio-crude are 5-25 wt.% higher than the lipid content of the algae depending upon biochemical composition. The yields of bio-crude follow the trend lipids>proteins>carbohydrates.

Hydrothermal liquefaction of biomass: Developments from batch to continuous process

This review describes the recent results in hydrothermal liquefaction (HTL) of biomass in continuous-flow processing systems. Although much has been published about batch reactor tests of biomass HTL, there is only limited information yet available on continuous-flow tests, which can provide a more reasonable basis for process design and scale-up for commercialization. High-moisture biomass feedstocks are the most likely to be used in HTL. These materials are described and results of their processing are discussed. Engineered systems for HTL are described; however, they are of limited size and do not yet approach a demonstration scale of operation. With the results available, process models have been developed, and mass and energy balances determined. From these models, process costs have been calculated and provide some optimism as to the commercial likelihood of the technology.

Catalytic hydrothermal processing of microalgae: decomposition and upgrading of lipids.

Hydrothermal processing of high lipid feedstock such as microalgae is an alternative method of oil extraction which has obvious benefits for high moisture containing biomass. A range of microalgae and lipids extracted from terrestrial oil seed have been processed at 350 °C, at pressures of 150-200 bar in water. Hydrothermal liquefaction is shown to convert the triglycerides to fatty acids and alkanes in the presence of certain heterogeneous catalysts. This investigation has compared the composition of lipids and free fatty acids from solvent extraction to those from hydrothermal processing. The initial decomposition products include free fatty acids and glycerol, and the potential for de-oxygenation using heterogeneous catalysts has been investigated. The results indicate that the bio-crude yields from the liquefaction of microalgae were increased slightly with the use of heterogeneous catalysts but the higher heating value (HHV) and the level of de-oxygenation increased, by up to 10%.

Hydrothermal processing of algal biomass for the production of biofuels and chemicals

The area of processing algal biomass under hydrothermal conditions has received increasing interest over the last decade. The process has been identified to be especially suited for high moisture aquatic biomass such as microalgae and macroalgae, as the biomass is processed wet as a slurry in hot-compressed water. At lower temperatures, hydrothermal processing leads to carbonization reactions of the biomass and the primary product is a biochar – so-called hydrothermal carbonization. At intermediate temperatures, below the critical point of water, the process is referred to as hydrothermal liquefaction and the primary product is a biocrude. Above the critical point, gasification reactions predominate and the primary product is a syngas. Microalgae are regarded as a promising source of third-generation biofuels due to their high lipid content, fast growth rates and the absence of competition for food production. Macroalgae have high carbohydrate content and represent a largely untapped source of biomass for bioenergy and chemicals. The scope of this review is to summarize the current state of research on the hydrothermal carbonization, liquefaction and gasification of algal biomass. The effect of heterogeneous and homogeneous catalysis, operating conditions, energy balances and nutrient recycling are discussed.

Hydrothermal microwave processing of microalgae as a pre-treatment and extraction technique for bio-fuels and bio-products

Microalgae are regarded as a promising source of lipids for bio-diesel production and bio-products. The current paper investigates the processing of microalgal slurries under controlled microwave irradiation. Microwave power was applied to reach temperatures of 80, 100, 120 and 140 °C at a constant residence time of 12 min. Microwave irradiation led to disruption of the algal cell walls which facilitated lipid extraction. The influence of inorganic material on microwave heating was assessed for three strains including, Nannochloropsis occulata, Chlorogloeopsis fritschii and Pseudochoricystis ellipsoidea. Mass balances were calculated and showed that the amount of carbon, nitrogen and total mass recovered in the residue was highly dependent on process conditions and algae strain. Hydrothermal microwave processing (HMP) was found to be an effective pre-treatment for hydrothermal liquefaction and extraction of lipids and phytochemicals.

Effect of hydrothermal liquefaction aqueous phase recycling on bio-crude yields and composition.

Hydrothermal liquefaction (HTL) is a promising thermo-chemical processing technology for the production of biofuels but produces large amounts of process water. Therefore recirculation of process water from HTL of dried distillers grains with solubles (DDGS) is investigated. Two sets of recirculation on a continuous reactor system using K2CO3 as catalyst were carried out. Following this, the process water was recirculated in batch experiments for a total of 10 rounds. To assess the effect of alkali catalyst, non-catalytic HTL process water recycling was performed with 9 recycle rounds. Both sets of experiments showed a large increase in bio-crude yields from approximately 35 to 55wt%. The water phase and bio-crude samples from all experiments were analysed via quantitative gas chromatography-mass spectrometry (GC-MS) to investigate their composition and build-up of organic compounds. Overall the results show an increase in HTL conversion efficiency and a lower volume, more concentrated aqueous by-product following recycling.

Effect of Multifunctional Fuel Additive Package on Fuel Injector Deposit, Combustion and Emissions using Pure Rape Seed Oil for a DI Diesel

This work investigates the effect of a multifunctional diesel fuel additive package used with RapeSeed Oil (RSO) as a fuel in a DI heavy duty diesel engine. The effects on fuel injectors’ cleanliness were assessed. The aim was to maintain combustion performance and preventing the deterioration of exhaust emissions associated with injector deposit build up. Two scenarios were investigated: the effect of deposit clean-up by a high dose of the additive package; and the effect of deposit prevention using a moderate dose of the additive package. Engine combustion performance and emissions were compared for each case against use of RSO without any additive. The engine used was a 6 cylinder, turbocharged, intercooled Perkins Phaser Engine, fitted with an oxidation catalyst and meeting the Euro II emissions limits. The tests were conducted under steady state conditions of 23kW and 47kW power output at an engine speed of 1500 rpm. The in-cylinder pressure, gaseous and particulate exhaust emissions were measured. The injectors were inspected using SEM (Scanning Electronic Microscopy). The results show that the use of the multifunctional fuel additive package reduces the ignition delay (ID), increases the premixed combustion duration (PCD) and improves the combustion stability. The multifunctional fuel additive package also reduced the deposit build up on the fuel injectors and prevented the deterioration of engine-out particulate, CO and hydrocarbon emissions

Primary sewage sludge filtration using biomass filter aids and subsequent hydrothermal co-liquefaction

Hydrothermal liquefaction (HTL) is a promising technology for biofuel production and treatment of wastewater sludge. The current study investigates a novel utilization of biomass-assisted filtration of primary sludge to obtain high dry matter (DM) content sludge. Drastic improvements in filtration speed are achieved using different types of lignocellulosic biomass filter aids prepared via mechanical pre-treatment. The combined sludge-biomass filter cake is subsequently used as a feedstock for HTL and shows superior bio-crude yields and properties compared to their individual counterparts. The chemical energy recovery to bio-crude is increased to 75% compared to 46% for biomass and 67% for sludge on its own. The increased DM content of filter cakes (∼25%) compared to primary sludge (5%) increases the energy efficiency of HTL of primary sludge by a factor of 4.5. Introducing a biomass filteraid-HTL combination to a wastewater treatment plant would reduce the organic carbon load to treat by 62%. By combining sludge with lignocellulosic biomass the use of alkali catalyst can be avoided entirely which represents a major cost factor in HTL of lignocellulosics.

Hydrothermal co-liquefaction of biomasses – quantitative analysis of bio-crude and aqueous phase composition

Hydrothermal liquefaction (HTL) is a promising technology for conversion of wet biomasses to liquid fuels, but considerable amounts of oxygen and nitrogen remain in the bio-crude, while large amounts of water-soluble organics are displaced to the aqueous phase (AqP). In this study the bio-crude and AqP from HTL of 11 different feedstocks of lignocellulosics, residues, macroalgae, microalgae, and their mixtures were analyzed for elemental composition, total acid number, total organic carbon (TOC), total nitrogen, and pH. Quantitative analysis of major compound classes present in both bio-crudes and AqPs was achieved using gas chromatography coupled to mass spectrometry employing prior derivatization of authentic standards. A wide range of biochemical content was obtained through mixing of biomasses and quantitative analysis showed particular interaction between carbohydrates and proteins with extended effect on lipids. The ability of ammonia and amines to form Schiff bases was the key factor affecting elemental distribution and the direction of reaction pathways involved in the formation of cyclic oxygenates, hydroxypyridines, oxygenated aromatics, diols, and fatty acids in bio-crudes. Similarly, Schiff base formation accounts for increased formation of nitrogen-containing compounds in the AqP, leading to a decrease in TOC and total nitrogen in products from HTL of mixed biomasses. This work highlights the quantitative differences in bio-crude and AqP composition from HTL of varying biomasses and provides new knowledge of the effect of mixing biomasses on elemental distribution and composition of product fractions. The results provide valuable information for optimizing the feedstocks used for HTL based on biochemical composition.

Catalytic hydrotreatment of bio-crude produced from the hydrothermal liquefaction of aspen wood: a catalyst screening and parameter optimization study

Lignocellulosic plant matter, as a second generation biomass, has potential as a feedstock for the production of liquid bio-fuels providing an alternative to fossil fuels. Herein, we report detailed catalyst screening and parameter optimization for catalytic hydrotreatment of bio-crude produced from the continuous hydrothermal liquefaction (HTL) of aspen wood. Three different commercial metal oxide catalysts, NiW/Al2O3 and NiMo/Al2O3 with a high and low NiMo loading, were examined. Elemental analysis showed significant oxygen expulsion from 10.7 wt% in the bio-crude down to a minimum of 0.7 wt% in the hydrotreated bio-oil. Considering the degrees of hydrodeoxygenation (HDO) along with yields, NiMo/Al2O3 with a high NiMo loading showed the best performance with a yield of 71.9 wt% and an oxygen content of 2.4 wt% for the final bio-oil, followed by low loaded NiMo/Al2O3 (yield 67.4 wt%, oxygen content 3.8 wt%) and NiW/Al2O3 (yield 58.7 wt%, oxygen content 6.9 wt%) under relatively mild conditions. Characterization by gas chromatography coupled with mass spectrometry pointed towards possible conversion pathways of the main bio-crude components during hydrotreatment. These included the conversion of substituted cyclopentenones to cycloalkanes, and oxygen-containing substituted polycyclic aromatic hydrocarbons (PAHs) to polycyclic aromatic hydrocarbons (e.g. anthracene, phenanthrene and naphthalene) and cracking of fatty acids to aliphatic hydrocarbons. The effects of initial hydrogen pressure and reaction time were investigated. The results demonstrate the potential of upgrading the bio-crude produced from the HTL of aspen wood to a hydrocarbon product with properties similar to petroleum derived transportation fuels.