Synergetic sustainability enhancement via current biofuel infrastructure: waste-to-energy concept for biodiesel production.

The concept of waste-to-energy (WtE) with regards to the utilization of byproducts from the bioethanol industry (e.g., distiller's dried grain with solubles: DDGS) was employed to enhance the renewability of biodiesel, which would be an initiative stage of a biorefinery due to the conjunction between bioethanol and biodiesel. For example, DDGS is a strong candidate for use as a biodiesel feedstock due to the tremendous amount that is regularly generated. On the basis of an estimation of possible lipid recovery from DDGS, ∼30% of the biodiesel feedstock demand in 2010 could be supported by the total DDGS generation in the same year. Considering the future expansion of the bioethanol industry up to 2020, the possible lipid recovery from DDGS would provide more than 6 times the biodiesel feedstock demand in 2010. In order to enhance the renewability of biodiesel, the transformation of lipid extracted from DDGS into fatty acid ethyl ester (FAEE) via a noncatalytic transesterification reaction under ambient pressure was investigated in this work. The newly introduced method reported here enables the combination of the esterification of free fatty acids (FFAs) and the transesterification of triglycerides into a single step. This was achieved in the presence of a porous material (i.e., charcoal), and the optimal conditions for transformation into biodiesel via this noncatalytic method were assessed at the fundamental level.

Thermo-chemical process with sewage sludge by using CO2.

This work proposed a novel methodology for energy recovery from sewage sludge via the thermo-chemical process. The impact of CO2 co-feed on the thermo-chemical process (pyrolysis and gasification) of sewage sludge was mainly investigated to enhance thermal efficiency and to modify the end products from the pyrolysis and gasification process. The CO2 injected into the pyrolysis and gasification process enhance the generation of CO. As compared to the thermo-chemical process in an inert atmosphere (i.e., N2), the generation of CO in the presence of CO2 was enhanced approximately 200% at the temperature regime from 600 to 900 °C. The introduction of CO2 into the pyrolysis and gasification process enabled the condensable hydrocarbons (tar) to be reduced considerably by expediting thermal cracking (i.e., approximately 30-40%); thus, exploiting CO2 as chemical feedstock and/or reaction medium for the pyrolysis and gasification process leads to higher thermal efficiency, which leads to environmental benefits. This work also showed that sewage sludge could be a very strong candidate for energy recovery and a raw material for chemical feedstock.

Utilizing carbon dioxide as a reaction medium to mitigate production of polycyclic aromatic hydrocarbons from the thermal decomposition of styrene butadiene rubber.

The CO(2) cofeed impact on the pyrolysis of styrene butadiene rubber (SBR) was investigated using thermogravimetric analysis (TGA) coupled to online gas chromatography/mass spectroscopy (GC/MS). The direct comparison of the chemical species evolved from the thermal degradation of SBR in N(2) and CO(2) led to a preliminary mechanistic understanding of the formation and relationship of light hydrocarbons (C(1-4)), aromatic derivatives, and polycyclic aromatic hydrocarbons (PAHs), clarifying the role of CO(2) in the thermal degradation of SBR. The identification and quantification of over 50 major and minor chemical species from hydrogen and benzo[ghi]perylene were carried out experimentally in the temperature regime between 300 and 500 °C in N(2) and CO(2). The significant amounts of benzene derivatives from the direct bond dissociation of the backbone of SBR, induced by thermal degradation, provided favorable conditions for PAHs by the gas-phase addition reaction at a relatively low temperature compared to that with conventional fuels such as coal and petroleum-derived fuels. However, the formation of PAHs in a CO(2) atmosphere was decreased considerably (i.e., ∼50%) by the enhanced thermal cracking behavior, and the ultimate fates of these species were determined by different pathways in CO(2) and N(2) atmospheres. Consequently, this work has provided a new approach to mitigate PAHs by utilizing CO(2) as a reaction medium in thermochemical processes.

Biodiesel production from sewage sludge: new paradigm for mining energy from municipal hazardous material.

This work demonstrates that the production of biodiesel using the lipids extracted from sewage sludge (SS) could be economically feasible because of the remarkably high yield of oil and low cost of this feedstock, as compared to conventional biodiesel feedstocks. The yield of oil from SS, 980,000 L ha(-1) year(-1), is superior to those from microalgal and soybean oils, 446 and 2200 L ha(-1) year(-1), respectively. According to the case study of South Korea, the price of the lipids extracted from SS was approximately $0.03 L(-1) (USD), which is lower than those of all current biodiesel feedstocks. This work also highlights the insight of a novel methodology for transforming lipids containing high amounts of free fatty acids (FFAs) to biodiesel using a thermochemical process under ambient pressure in a continuous flow system. This allowed the combination of esterification of FFAs and transesterification of triglycerides into a single noncatalytic process, which led to a 98.5% ± 0.5% conversion efficiency to FAME (fatty acid methyl ester) within 1 min in a temperature range of 350-500 °C. The new process for converting the lipids extracted from SS shows high potential to achieve a major breakthrough in minimizing the cost of biodiesel production owing to its simplicity and technical advantages, as well as environmental benefits.

Involvement of Shewanella oneidensis MR-1 LuxS in biofilm development and sulfur metabolism.

The role of LuxS in Shewanella oneidensis MR-1 has been examined by transcriptomic profiling, biochemical, and physiological experiments. The results indicate that a mutation in luxS alters biofilm development, not by altering quorum-sensing abilities but by disrupting the activated methyl cycle (AMC). The S. oneidensis wild type can produce a luminescence response in the AI-2 reporter strain Vibrio harveyi MM32. This luminescence response is abolished upon the deletion of luxS. The deletion of luxS also alters biofilm formations in static and flowthrough conditions. Genetic complementation restores the mutant biofilm defect, but the addition of synthetic AI-2 has no effect. These results suggest that AI-2 is not used as a quorum-sensing signal to regulate biofilm development in S. oneidensis. Growth on various sulfur sources was examined because of the involvement of LuxS in the AMC. A mutation in luxS produced a reduced ability to grow with methionine as the sole sulfur source. Methionine is a key metabolite used in the AMC to produce a methyl source in the cell and to recycle homocysteine. These data suggest that LuxS is important to metabolizing methionine and the AMC in S. oneidensis.

Investigation into role of CO2 in two-stage pyrolysis of spent coffee grounds.

As a way of improving process efficiency of pyrolysis of waste biomass, the effect of carbon dioxide (CO2) on pyrolysis of spent coffee grounds (SCGs) was examined using a two-stage pyrolysis reactor consisting of a region with increasing temperature and an isothermal region. It was experimentally validated that CO2 accelerates thermal cracking of organic compounds formed during the pyrolysis of SCGs. The expedited thermal cracking attributed to employing CO2 in pyrolysis of SCGs led to changing pyrolytic products in gas, liquid, and solid phases. The production of gaseous carbon monoxide was increased when using CO2 as the pyrolysis medium. In liquid pyrolytic products, the formation of phenolic compounds was hindered in the CO2-assited pyrolysis. Biochar morphology (solid pyrolytic product) was also changed with different pyrolysis environments. This study shows that CO2 can help improve applicability of pyrolysis of waste biomass by modifying three phase pyrolytic products in a two-stage pyrolyzer.

Catalytic pyrolysis of swine manure using CO2 and steel slag.

Pyrolysis of swine manure (SM) was conducted as a case study to establish an environmentally sound management of livestock manure. To build a more renewable pyrolysis platform for SM, this study selected carbon dioxide (CO2) as the reaction medium. In addition, CO2 was used in pyrolysis of SM to restrict the formation of toxic compounds, such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). A series of thermo-gravimetric analysis (TGA) tests was done to understand the thermolysis of SM in the CO2 environment. The TGA tests elucidated no occurrence of heterogeneous reactions between the SM sample and the CO2. Moreover, the TGA tests of SM suggested that SM contains more volatile matter (VM) than lignocellulosic biomass. Non-catalytic transesterification of SM lipids confirmed that the dried SM sample contained 8.85 ±â€¯0.05 wt% of lipids. This study also confirmed that the mechanistic role of CO2 was realized through the gas phase reactions between volatile pyrolysates evolved from the thermolysis of SM and CO2. In summary, CO2 donates O, enhancing the generation of CO through homogeneous reactions. In parallel, this study confirmed that CO2 suppress dehydrogenation. Therefore, the identified gas phase reactions between volatile pyrolysates and CO2 led to the compositional modifications in the condensable pyrolysates. However, such mechanistic features arising from CO2 only initiated at ≥520 °C. To expedite the reaction kinetics of the homogeneous reaction triggered by CO2, steel slag (SS) was used as a catalyst. Hence, the reaction kinetics associated with the mechanistic role of CO2 were substantially enhanced (up to 80%) when SS was used as a catalyst. Therefore, all experimental findings strongly suggest that CO2 can be utilized as a raw material in a thermo-chemical process. More importantly, all observations suggest that CO2 lopping can also be achieved in a thermo-chemical process. Lastly, this study shows that the high Cu content in SM was effectively immobilized through pyrolysis. Conclusively, this study experimentally proved that CO2 could be promising for restricting the formation of toxic pollutant in the thermo-chemical treatment in that CO2 offers an innovative and strategic means for controlling the ratio of C to H. Note that aromaticity and toxicity of chemical compounds are highly contingent on the ratio of C to H.

Boosting the value of biodiesel byproduct by the non-catalytic transesterification of dimethyl carbonate via a continuous flow system under ambient pressure.

Transformation of coconut oil into biodiesel by using dimethyl carbonate (DMC) via a non-catalytic transesterification reaction under ambient pressure was investigated in this study. The non-catalytic transformation to biodiesel was achieved by means of a heterogeneous reaction between liquid triglycerides and gas phase DMC. The reaction was enhanced in the presence of porous material due to its intrinsic physical properties such as tortuosity and absorption/adsorption. The numerous pores in the material served as micro reaction chambers and ensured that there was enough contact time between the liquid triglycerides and the gaseous DMC, which enabled the completion of the transesterification. The highest fatty acid methyl esters (FAMEs) yield achieved was 98±0.5% within 1-2min at a temperature of 360-450°C under ambient pressure. The fast reaction rates made it possible to convert the lipid feedstock into biodiesel via a continuous flow system without the application of increased pressure. This suggested that the commonly used supercritical conditions could be avoided, resulting in huge cost benefits for biodiesel production. In addition, the high value of the byproduct from the transesterification of the lipid feedstock with DMC suggested that the production biodiesel using this method could be more economically competitive. Finally, the basic properties of biodiesel derived from the non-catalytic conversion of rapeseed oil with DMC were summarised.

Noncatalytic transformation of the crude lipid of ChlorellaI vulgaris into fatty acid methyl ester (FAME) with charcoal via a thermo-chemical process.

The noncatalytic transformation of the crude lipid of Chlorella vulgaris (C. vulgaris) into fatty acid methyl ester (FAME) via a thermo-chemical process was mainly investigated in this work. The crude lipid of C. vulgaris was recovered by means of solvent extraction from C. vulgaris cultivated in a raceway pond. The conventional catalyzed transesterification of crude lipid of C. vulgaris is notably inhibited by the impurities contained in the crude lipid of C. vulgaris. These impurities are inevitably derived from the solvent extraction process for C. vulgaris. However, this work presents the noncatalytic transesterification of microalgal lipid into FAME, which could be an alternative option. For example, the noncatalytic transformation of microalgal lipid into FAME provides evidence that the esterification of free fatty acids (FFAs) and the transesterification of triglycerides can be combined into a single step less susceptible to the impurities and with a high conversion efficiency (∼97%).

Sequential co-production of biodiesel and bioethanol with spent coffee grounds.

The sequential co-production of bioethanol and biodiesel from spent coffee grounds was investigated. The direct conversion of bioethanol from spent coffee grounds was not found to be a desirable option because of the relatively slow enzymatic saccharification behavior in the presence of triglycerides and the free fatty acids (FFAs) found to exist in the raw materials. Similarly, the direct transformation of the spent coffee grounds into ethanol without first extracting lipids was not found to be a feasible alternative. However, the crude lipids extracted from the spent coffee grounds were themselves converted into fatty acid methyl ester (FAME) and fatty acid ethyl ester (FAEE) via the non-catalytic biodiesel transesterification reaction. The yields of bioethanol and biodiesel were 0.46 g g(-1) and 97.5±0.5%, which were calculated based on consumed sugar and lipids extracted from spent coffee grounds respectively. Thus, this study clearly validated our theory that spent coffee grounds could be a strong candidate for the production of bioethanol and biodiesel.

Non-catalytic heterogeneous biodiesel production via a continuous flow system.

This study provides a novel methodology for biodiesel (FAME) production under ambient pressure, which resolves most drawbacks of current commercialized biodiesel conversion via the transesterification reaction. This has been achieved by means of a thermo-chemical process and a true continuous flow system. This also enables combination of esterification of free fatty acids (FFAs) and transesterification of triglycerides into a single process without utilizing a catalyst, and leads to a 98-99±0.5 % conversion efficiency of FAME within 1 min in the temperature range of 350-500 °C. High FFA content in oil feedstock is not a matter of the new process, which enables the use of a broader variety of feedstocks, including all edible and inedible fats. Another feature of this novel method is that it does not produce wastewater. Thus, the new process has potential to spur a breakthrough in the lowest cost of biodiesel production. Moreover, this method also requires utilization of carbon dioxide during biodiesel production, an additional environmental benefit.

New candidate for biofuel feedstock beyond terrestrial biomass for thermo-chemical process (pyrolysis/gasification) enhanced by carbon dioxide (CO2).

The enhanced thermo-chemical process (i.e., pyrolysis/gasification) of various macroalgae using carbon dioxide (CO(2)) as a reaction medium was mainly investigated. The enhanced thermo-chemical process was achieved by expediting the thermal cracking of volatile chemical species derived from the thermal degradation of the macroalgae. This process enables the modification of the end products from the thermo-chemical process and significant reduction of the amount of condensable hydrocarbons (i.e., tar, ∼50%), thereby directly increasing the efficiency of the gasification process.

Biostimulation of PAH degradation with plants containing high concentrations of linoleic acid.

Many plant species enhance the biodegradation of polycyclic aromatic hydrocarbons (PAHs), but there is little understanding of the mechanisms by which this occurs. This research identified phytochemicals that stimulate pyrene degradation using crushed roottissues from 43 plants that were screened in soil spiked with 100 ppm pyrene. Among the plants tested, root tissues from Apium graveolens (celery), Raphanus sativus (radish), Solanum tuberosum (potato), and Daucus carota (carrot) were most effective for promoting disappearance of pyrene within 40 days. Experiments with A. graveolens showed that plant culture in soil contaminated with pyrene or benzo[a]pyrene was as effective as addition of crushed root tissues. Comparison of the chemical compositions of the effective plants suggested that linoleic acid was the major substance that stimulated PAH degradation. This hypothesis was supported in experiments examining degradation of pyrene and benzo[a]pyrene in soil amended with linoleate, whereas linolenic and palmitic acids did not stimulate degradation within a 20 day period. Antibiotic inhibitor studies implicated gram positive bacteria as a predominant group responding to linoleic acid. These findings provide insight into the mechanisms by which plants enhance degradation of PAHs, and have practical application for remediation of PAH contaminated soils.