Biomass to levulinic acid: A techno-economic analysis and sustainability of biorefinery processes in Southeast Asia.

Aligned with Singapore's commitment to sustainable development and investment in renewable resources, cleaner energy and technology (Sustainable Singapore Blueprint), we report a techno-economic analysis of the biorefinery process in Southeast Asia. The considerations in this study provide an overview of the current and future challenges in the biomass-to-chemical processes with life-cycle thinking, linking the land used for agriculture and biomass to the levulinic acid production. 7-8 kg of lignocellulosic feedstock (glucan content 30-35 wt%) from agriculture residues empty fruit bunches (EFB) or rice straw (RS) can be processed to yield 1 kg of levulinic acid. Comparisons of both traditional and "green" alternative solvents and separation techniques for the chemical process were modelled and their relative energy profiles evaluated. Using 2-methyltetrahydrofuran (2-MeTHF) as the process solvent showed to approx. 20 fold less energy demand compared to methyl isobutyl ketone (MIBK) or approx. 180 fold less energy demand compared to direct distillation from aqueous stream. Greenhouse gases emissions of the major operations throughout the supply chain (energy and solvent use, transport, field emissions) were estimated and compared against the impact of deforestation to make space for agriculture purposes. A biorefinery process for the production of 20 ktonne/year of levulinic acid from two different types of lignocellulosic feedstock was hypothesized for different scenarios. In one scenario the chemical plant producing levulinic acid was located in Singapore whereas in other scenarios, its location was placed in a neighboring country, closer to the biomass source. Results from this study show the importance of feedstock choices, as well as the associated plant locations, in the quest for sustainability objectives.

Bioenergy co-products derived from microalgae biomass via thermochemical conversion--life cycle energy balances and CO2 emissions.

An investigation of the potential to efficiently convert lipid-depleted residual microalgae biomass using thermochemical (gasification at 850 °C, pyrolysis at 550 °C, and torrefaction at 300 °C) processes to produce bioenergy derivatives was made. Energy indicators are established to account for the amount of energy inputs that have to be supplied to the system in order to gain 1 MJ of bio-energy output. The paper seeks to address the difference between net energy input-output balances based on a life cycle approach, from "cradle-to-bioenergy co-products", vs. thermochemical processes alone. The experimental results showed the lowest results of Net Energy Balances (NEB) to be 0.57 MJ/MJ bio-oil via pyrolysis, and highest, 6.48 MJ/MJ for gas derived via torrefaction. With the complete life cycle process chain factored in, the energy balances of NEBLCA increased to 1.67 MJ/MJ (bio-oil) and 7.01 MJ/MJ (gas). Energy efficiencies and the life cycle CO2 emissions were also calculated.

Life cycle energy and CO2 analysis of microalgae-to-biodiesel: preliminary results and comparisons.

Despite claims that microalgal biofuels are environmentally friendlier alternatives to conventional fuels, debate surrounding its ecological benefits or drawbacks still exists. LCA is used to analyze various biofuel production technologies from 'cradle to gate'. Energy and CO(2) balances are carried out for a hypothetical integrated PBR-raceway microalgae-to-biodiesel production in Singapore. Based on a functional unit of 1 MJ biofuel, the total energy demands are 4.44 MJ with 13% from biomass production, 85% from lipid extraction, and 2% from biodiesel production. Sensitivity analysis was carried out for adjustments in energy requirements, percentage lipid contents, and lower/higher heating product value. An 'Optimistic Case' was projected with estimates of: 45% lipid content; reduced energy needs for lipid extraction (1.3 MJ per MJ biodiesel); and heating value of biodiesel (42 MJ/kg). The life cycle energy requirements dropped significantly by about 60%. The results are compared with other published case studies from other countries.

Influence of initial dissolved oxygen concentration on Fenton's reagent degradation.

The effect of initial dissolved oxygen concentration (IDOC) on Fenton's reagent degradation of a dyestuff, Reactive Black 5 was explored in this study. The study was designed, conducted and analysed based on Central Composite Rotatable Design using a 3-1 lab-scale reactor. The participation of O2 in the process was experimentally observed and appears to be affected by the dosage of the reagents used in the study. The IDOC was found to have a significant influence on the process. Reducing the IDOC from 7.5 mg l(-1) to 2.5 mg l(-1) increased the removal of TOC by an average of about 10%. Reduction of IDOC from 10 mg l(-1) to 0 mg l(-1) enhanced the TOC removal by about 30%. The negative influence of IDOC is likely to be caused by the competition between the O2 and the reagents for the organoradicals. A model describing the relationship between initial TOC removal, reagent dosage and IDOC has also been developed.

Fenton oxidation of Reactive Black 5: effect of mixing intensity and reagent addition strategy.

This study investigates the effect of mixing intensity and reagents addition strategy on Fenton's reagent degrading a common reactive diazo type dyestuff, Reactive Black 5. Within the experimental conditions used in the study, the effect of mixing intensity on TOC removal was observed to be both significant and complex. Using factorial analysis, it was found that if the reagents are added near to each other, higher mixing intensity will enhance the effectiveness of the degradation process. However, a very, high mixing level may cause reduction in performance. It was also observed that the mixing intensity effect interacts with Fe2+ or/and H2O2 dosage. The benefit of increasing mixing intensity appears to be higher for lower reagents dosage. The effect of reagents addition strategy was found to be inter-dependent with mixing intensity level. It was also deduced that proper chemical addition strategy could be used to reduce the mixing intensity requirement of the process.

Characterization of effects of selected organic substances on decomposition of hydrogen peroxide during Fenton reaction.

This study aims to investigate the effects of selected organic substances on the degradation of hydrogen peroxide during the Fenton reaction. Since the presence of organic substances can strongly affect the mechanism of the Fenton reaction, the information on effects of organic substances on the reaction would be a vital guide to the success of its application to the destruction of organics in wastewater. Several organic compounds having different structures were selected as model pollutants: 4-chlorophenol, 1,4-dioxane, chloroform, a dye (reactive black-5), and EDTA. Oxidation of 4-chlorophenol and reactive black-5 resulted in enormously fast degradation of hydrogen peroxide, while others such as 1,4-dioxane and chloroform showed much slower degradation. These experimental data were compared to simulation results from a computational model based on a simple *OH-driven oxidation model. Modelling results for chloroform and 1,4-dioxane were in relatively good agreement with the experimental data, while those for 4-chlorophenol and reactive black-5 were very different from the experimental data. The results for EDTA showed a different trend to those for other compounds. From these results, classification of organic substances into several sub-groups was tried.