Anthony K Lau

Associate Professor

Relevant Degree Programs


Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Nov 2019)
Logistics of wood chips supply and performance analysis of an industrial updraft gasifier (2020)

In the published literature, there is a lack of detailed data relevant to full-scale gasification plants that operate on variable quality of biomass feedstock, especially those originating from urban sources. The objectives of this study are to characterize the spatial and temporal variations in the physical properties of waste wood supplied to the UBC industrial gasification system; and to conduct an analysis of variations in fuel properties vs. gasifier performance in terms of system reliability, steam production, syngas quality, tar formation, and gasification efficiencfy. The measured values of fuel properties were in compliance with the fuel specifications. Large variation in steam production during the earlier years of operation was attributed partly to the variations in feedstock moisture content and particle size. Subsequent data collection and analysis revealed that fuel moisture content affects the production of steam the most. Fuel moisture content (mc), gasifier bed temperature, and fuel feeding rate were identified to be the key factors that affect syngas quality, tar formation, and gasifier efficiency. Multi-variable regression models were developed to quantify these relationships. Despite a wide variation of the data collected from the industrial gasifier, our results are in line with the trends reported in the literature based on lab-scale and pilot-scale studies. Research findings indicated that even for a commercial updraft gasifier, syngas quality and steam production would be enhanced if the fuel moisture content could be maintained around 20% (wb). With air as the gasifying agent, when fuel moisture content decreased to 20%, the carbon monoxide (CO) concentration (~30%) and calorific value (>4 MJ/m³) would be higher, whereas tar concentration (
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Development of a quantitative risk analysis approach to evaluate the economic performance of an industrial-scale biorefinery (2018)

The overall objective of this dissertation was to evaluate the economic performance of a commercial-scale biorefinery given the volatility in the market price of the final product and the variability in the biomass delivered cost. To this end, a risk analysis methodology comprised of five steps was developed: 1) construct the supply area geographical data base, 2) perform Monte Carlo simulation via the Integrated Biomass Supply Analysis and Logistics Multi-Crop model (IBSAL-MC) to produce the biomass delivered cost distribution, 3) conduct economic analysis by combining the biomass delivered cost distribution with the product market price to generate a ROI (return on investment) heat map, 4) repeat Steps 1 to 3 for an alternative scenario and 5) compare heat maps from different scenarios to quantify the effectiveness and incentive available for achieving an alternative scenario.The proposed methodology was applied to a cellulosic sugar plant under construction in Southwestern Ontario, Canada. Three biorefinery scenarios were considered including small-scale (175 dry tonnes (dt)/day), medium-scale (520 dt/day) and large-scale (860 dt/day). Results showed that the magnitude of the required logistical resources and their associated upfront and administrative costs hindered the biorefinery’s economic performance as its scale increased. The risk analysis approach was then applied to the small-scale scenario. Potential economic incentives for participating biomass producers were quantified as the participation rate increased from 20% to 30%, 40% and 50. While increasing farm participation rate was economically beneficial to the biorefinery, there were more economic benefits if the sugar market price was in a favourable range. When a farmers’ co-operative was introduced to the supply system, if the biorefinery could secure a long-term consumer of the produced sugar in the price range of $425-575/tonne, the farmers’ co-operative and other investors of the biomass project were both more likely to achieve an acceptable annual ROI that exceeds 10%.

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Physical and thermal characterization of ground wood chip and ground wood pellet particles (2017)

The goal of the present study is to characterize the ground chip and ground pellet particles with respect to their size, shape, density, flow properties, drying and pyrolysis mass loss. Commercial wood pellets and pulp-quality wood chips are used in this study. These commercial samples are ground in the laboratory using a range of grinder screen sizes. The grinder power input is measured. The ground particles are examined for their size and shape. The ground particles are thermally treated in a micro TGA equipment and in a lab-scale thin-layer drying/pyrolysis equipment. The grinding results show that grinding a whole pellet to the desirable particle sizes for pyrolysis (~1 mm) takes around 1/7 of energy required to grind a whole wood chip to the same mean particle size. Pellet particles are denser, more spherical and shorter than the needle-shape chip particles. The spheroid shape of ground pellet particles lowers the compressibility of bulk, lowers the cohesion among the particles and facilitates their flowability. Higher density and random fiber orientation of the pellet particles prolong the duration of their drying significantly compared to the drying time of thin and long wood chip particles. Further moisture diffusion modeling shows that the moisture diffusion rate inside the pellet particles is half of those inside the chip particles. Although chip and pellet particles show the same level of shrinkage in size of a single particle due to drying, ground pellet particles exhibit a larger reduction in their bed porosity than the bed porosity measured for ground chip particles. Both chip and pellet particles reach their fiber saturation point at a moisture content of around 0.50 (dry basis). The pyrolysis kinetic parameters are determined experimentally and a two-zone kinetic mechanism is modeled and validated using the experimental thin-layer pyrolysis data.

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Anaerobic fermentation for biological hydrogen production in a sequencing batch reactor (2013)

Biological hydrogen production via anaerobic fermentation of organic waste can be potentially a greener and sustainable technology. Thus far, most research has been conducted using continuous stirred tank reactors (CSTR). Anaerobic sequencing batch reactors (ASBR) have advantages over CSTR, but there are disadvantages in terms of their operation. The overall goal of the thesis research is to enhance hydrogen production by optimizing the operational conditions in an ASBR using agri-food wastewater as substrate. An ASBR with 6-L working volume was inoculated with sewage sludge from the anaerobic zone of a sewage treatment facility and was not pretreated to select the hydrogen-producing bacteria. Hydrogen productivity was estimated by hydrogen content (%), hydrogen production rate (HPR) and hydrogen yield as the performance indicators in response to changes in pH, hydraulic retention time (HRT), organic loading rate (OLR), and cyclic duration (CD) as the key operational parameters. Using dairy wastewater as substrate, the suppression of methanogenesis was feasible without pretreatment of inoculum under the conditions of higher OLR and shorter HRT, which favoured hydrogen production. With carbohydrate-rich synthetic wastewater as substrate, the combination of relatively low pH 4.5 and HRT 30 hr was found to be the optimal condition for hydrogen production. For higher hydrogen production, ethanol-to-acetic acid ratio of 1.25 and food-to-microorganism ratio of 0.84 were revealed as threshold values. Higher hydrogen productivity at longer CD was not necessarily accompanied with higher microbial growth that occurred at shorter CD. Subsequently, real sugar refinery wastewater was used in the tests for biohydrogen production. Based on statistical analysis and curve fitting by the modified Gompertz model of the data as well as microbial identification, the operational setting of (pH 5.5, HRT 10 hr, OLR 15 kg/m³.d) was concluded to be optimal with the performance indicators of (71.8±10.5% H₂, HPR 2.11±0.31 L H₂/L reactor.d and yield 0.95±0.13 mol H₂/mol sucrose). Taxonomic analysis confirmed the presence of dominant hydrogen-producing bacteria among the diverse microbial genera, and in particular, the Clostridia spp. without the pretreatment of inocula. Further studies with the optimization of operational conditions would contribute towards making the best possible decision for ASBR.

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Moisture sorption and gas emissions during the storage of high moisture woody biomass (2013)

Moisture sorption and gas emissions are major processes associated with biomass storage. Depending on the storage conditions, these processes alter the structure and composition of biomass. The objectives of this research are (1) to develop moisture relations for woody biomass exposed to drying and wetting environments; (2) to quantify gas emissions from biomass stored under aerobic and anaerobic conditions; and (3) to develop dry matter loss equations for the stored biomass. Moisture adsorption and desorption (drying) experiments were carried out on Aspen branches in a controlled temperature and humidity chamber. Frequent wetting-drying cycles were simulated by spraying water on the biomass. A lump model for simulating moisture adsorption-desorption was developed and calibrated with experimental results. The model was applied to the Aspen bales stored for one year in the field under natural conditions. The predicted moisture contents using the lump moisture transfer model were found to be in reasonably good agreement with the moisture contents measured in the stored bales. In another set of experiments, gas emissions from stored Western Red Cedar (WRC) and Douglas fir (DF) were analyzed. The emissions of CO₂, CO, H₂ and CH₄, and the depletion of O₂ were measured. The highest total CO₂ emissions from WRC stored in the non-aerobic and aerobic reactors were 2.8 g/kg DM and 6.6 g/kg DM, respectively. Higher gas emissions were measured from stored DF materials than from WRC. Common volatile organic compounds (VOCs) measured using GC-MS were methanol, aldehydes, terpene, acid, acetone, hexane, ketone, benzene, ethers and esters from WRC and DF. The total VOC concentrations were found to have a positive correlation with temperature. The results of microbial analysis were compatible with gas emission results. Positive correlations between percent dry matter losses and gas emissions were found for both aerobic and non-aerobic storage conditions. The summation of gas emissions from aerobic reactors is greater than accumulated gas emissions from non-aerobic reactors over the same storage period. It was found that DF is more readily degradable than WRC. Greens (leaves and twigs) degrade faster than wood chips.

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Preventive control of ammonia and odor emissions during the active phase of poultry manure composting (2009)

Traditional measures used in the composting industry for ammonia and odor emissions control are those involving collection and treatment such as thermal oxidation, adsorption, wet scrubbing and biofiltration. However, these methods do not address the source of the odor generation problem. The primary objective of this thesis research was to develop preventive means to minimize ammonia and odor emissions, and maximize nitrogen conservation to increase the agronomic value of compost. Laboratory-scale experiments were performed to examine the effectiveness of various technologies to minimize these emissions during the active phase of composting. These techniques included precipitating ammonium into struvite in composting matrix before it release to outside environment; the use of chemical and biological additives in the form of yeast, zeolite and alum; and the manipulation of key operational parameters during the composting process. The fact that struvite crystals were formed in manure composting media, as verified by both XRD and SEM-EDS analyses, represents novel findings from this study. This technique was able to reduce ammonia emission by 40-84%, while nitrogen content in the finished compost was increased by 37-105%. The application of yeast and zeolite with dosages of 5-10% enhanced the thermal performance of composting and the degree of degradation, and ammonia emission was reduced by up to 50%. Alum was found to be the most effective additive for both ammonia and odor emission control; ammonia emission decreased by 45-90% depending on the dosage, and odor emission assessed via an dynamic dilution olfactometer was reduced by 44% with dosages above 2.5%. This study reaffirmed that aeration is the most influential factor to odor emission. An optimal airflow rate for odor control would be 0.6 L/ dry matter with an intermittent aeration system. Quantitative relationships between odor emission and key operational parameters were determined, which would enable “best management practices” to be devised and implemented for composting.An empirical odor predictive model was developed to provide a simple and direct means for simulation of composting odor emissions. The effects of operating conditions were incorporated into the model with multiplicative algorithm and linearization approximation approach. The model was validated with experimental observations.

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Master's Student Supervision (2010 - 2018)
Calorific value of wood pellets (2015)

The export of wood pellets from Canada to Europe has been increasing steadily in recent years (roughly 1.8 million ton in 2013). Due to distances involved, wood pellets remain in transit and storage for months before their final consumption. The net calorific value determines the price of wood pellets purchased in Europe. There have been concerns about the changes of net calorific values over time. In this study, the effects of storage time, storage configuration, storage temperature, and wood pellet quality on the net calorific value of wood pellets for a period of 6 months were investigated. Storage configurations were “open” or “closed” and storage temperatures were 25°C, 35°C and 45°C. Two types of wood pellets used: white (10% bark) and mixed (40% bark). The results in the “closed” storage scenario indicated that storage time had a positive effect on the net calorific value, where the net calorific value increased by 1 to 2% over the storage period. In the open storage scenario, the moisture content had the most significant impact on the net calorific value. A multivariable linear regression and analysis of variance performed verified the graphical results. It was postulated that the higher energy potential compounds – low molecular weight aldehyde and ketone or off-gasses such as carbon monoxide, methane and hydrogen – produced during pellet storage, caused the increase in net calorific values.

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Logistics modeling of biomass supply chain in Ontario (2015)

The overall goal of this research is to investigate the logistics of agricultural biomass in Ontario, Canada using the Integrated Biomass Supply Analysis and Logistics Model (IBSAL). The applicability of IBSAL is demonstrated through simulating three case studies. Case A is for the supply of corn stover to Ontario Power Generation (OPG) in Lambton. Case B concerns the supply of baled switchgrass from three farms to a greenhouse operation. Case C is for the supply of straw or switchgrass bales from 5 growing regions to Mushroom Producers Coop Inc. (MPCI).For Case A, five scenarios of delivering corn stover to the OPG power plant in Lambton Ontario are investigated: (1) base scenario, (2) central storage scenario, (3) direct scenario, (4) barge scenario, (5) railroad scenario. The net amount of annual biomass demand at the power plant is estimated to be 124,264 dry metric ton (Mg). For scenarios 1 to 5 the amount of biomass required to be harvested is respectively 160123, 155730, 151141,172480, and 170686 Mg per year. Also the total cost estimated to be respectively $37/Mg, $49/Mg, $33/Mg, $94/Mg, and $81/Mg.For Case B, the annual heating demand of a greenhouse located on southwestern Ontario near Lake Huron is calculated as 20,730 GJ/year. Roughly 2,200 Mg of switchgrass is required. Cost, energy consumption and carbon emission associated with the supply chain are $66/Mg, 151.3 MJ/Mg and 10.4 kg CO₂/Mg, respectively. The dry matter loss is calculated to be 805 Mg.For Case C, the following scenarios are modeled: (1) Base case scenario, (2) Straw location scenario, (3) Straw field to MPCI, (4) Switchgrass location scenario. Delivery costs of the first scenario vary in the range of $50-69/Mg. In the second scenario, the total average costs were $74/Mg, $68/Mg, and $70/Mg for the storage on gravel, storage on gravel with pad and protected under shed. Scenario 3 showed how sorted and unsorted bales affect the cost. The forth scenario the average total costs were reported to be $106.7/Mg, $91.4/Mg, and $90.8/Mg respectively for storage on the gravel pad on the gravel pad and protected under shed.

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Durability of Wood Pellets (2011)

No abstract available.

Development of an analytical tool for anaerobic digestion of organic wastes (2010)

Anaerobic digesters decompose organic matter biologically in the absence of oxygen. In some cases, in addition to waste management, the purpose of anaerobic digestion (AD) is to produce methane, which can be used for energy. In the Fraser Valley region, potentially 30 MW of energy can be generated through AD with the additional benefits of reduced odour, green house gas (GHG) emissions and soil and water contamination, which is produced currently from artificial fertilizers.The main goal of this research project is to develop an anaerobic digestion calculator that would assist farm and herd owners in the Lower Fraser Valley in making decisions on choosing suitable anaerobic digestion technologies for their own farms. The calculator is developed from Excel spreadsheets and graphical user interfaces (GUIs). These user interfaces take inputs, send the inputs to the corresponding spreadsheet cells, and block invalid inputs from causing calculation error. The new calculator uses the Lawrence and McCarty kinetic model to calculate substrate consumed during AD. This calculator takes hydraulic retention time (HRT) and feed, via animal counts, single-defined flow or mixing several waste sources, as inputs. From these inputs and default kinetic parameters, which can be modified, reactor size, biogas production rate, effluent characteristics, capital cost and revenue of the AD plant are calculated and summarized for users. Users can select one of the three possible digester configurations: completely-mixed, plug-flow and mixed plug-flow and heat and electricity co-generation or biogas upgrading. Currently the calculator is valid for simulating AD in the mesophilic temperature range only. Further modifications are needed to include other kinetic models, input more feed types and simulate thermophilic AD.

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