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PubMed2002

Chapter two: methodologies for characterisation of combustion sources and for quantification of their emissions.

Emissions from the combustion of biomass and fossil fuels result in generation of a large number of particle and gaseous products in outdoor and/or indoor air, which create health and environmental risks. Of particular importance are the very small particles that are emitted in large quantities from all the combustion sources, and that could be potentially more significant in terms of their impact on health and the environment than larger particles. It is important to quantify particle emissions from combustion sources for regulatory and control purposes in relation to air quality. This paper is a review of particle characteristics that are used as source signatures, their general advantages and limitations, as well as a review of source signatures of the most common combustion pollution sources including road transport, industrial facilities, small household combustion devices, environmental tobacco smoke, and vegetation burning. The current methods for measuring particle physical characteristics (mass and number concentrations) and principles of methodologies for measuring emission factors are discussed in the paper as well. Finally, the paper presents the recommendations for the future techniques for measurements of combustion products.

Air Movements↗
PubMed2005

Increase in tropospheric nitrogen dioxide over China observed from space.

Emissions from fossil fuel combustion and biomass burning reduce local air quality and affect global tropospheric chemistry. Nitrogen oxides are emitted by all combustion processes and play a key part in the photochemically induced catalytic production of ozone, which results in summer smog and has increased levels of tropospheric ozone globally. Release of nitrogen oxide also results in nitric acid deposition, and--at least locally--increases radiative forcing effects due to the absorption of downward propagating visible light. Nitrogen oxide concentrations in many industrialized countries are expected to decrease, but rapid economic development has the potential to increase significantly the emissions of nitrogen oxides in parts of Asia. Here we present the tropospheric column amounts of nitrogen dioxide retrieved from two satellite instruments GOME and SCIAMACHY over the years 1996-2004. We find substantial reductions in nitrogen dioxide concentrations over some areas of Europe and the USA, but a highly significant increase of about 50 per cent-with an accelerating trend in annual growth rate-over the industrial areas of China, more than recent bottom-up inventories suggest.

Air Pollutants↗
PubMed2004

Fine environmental particulate engenders alterations in human lung epithelial A549 cells.

Particulate matter (PM), a component of urban air pollution that derives primarily from the combustion of fossil fuels, is responsible for a number of health effects in humans. Recent studies have demonstrated that the fine particles (PM(2.5)) present in high numbers in PM samples can be more harmful than larger particles, since they are more efficiently retained in the peripheral lung. In the present study, we have investigated the biological effects of PM(2.5) on human lung epithelial cell line A549. Morphological analysis performed by immunofluorescence and electron microscopy showed that fine particles interact with the cell surface, where they induce evident alterations and, subsequently, are internalized in the cytoplasm. Cytoskeletal components, in particular microfilaments and microtubules, cause modifications upon challenge with PM(2.5). Of interest, an early cell response to the fine particulate is an increase of reactive oxygen species content, which can account for the observed cytoskeletal changes and the production of proinflammatory cytokines in A549 cells. In particular, exposure to PM(2.5) promoted a dose- and time-dependent release of TNF-alpha and IL-6 in the cell medium.

Air Pollutants↗
PubMed2002

Development and characterization of an annular denuder methodology for the measurement of divalent inorganic reactive gaseous mercury in ambient air.

Atmospheric mercury is predominantly present in the gaseous elemental form (Hg0). However, anthropogenic emissions (e.g., incineration, fossil fuel combustion) emit and natural processes create particulate-phase mercury(Hg(p)) and divalent reactive gas-phase mercury (RGM). RGM species (e.g., HgCl2, HgBr2) are water-soluble and have much shorter residence times in the atmosphere than Hg0 due to their higher removal rates through wet and dry deposition mechanisms. Manual and automated annular denuder methodologies, to provide high-resolution (1-2 h) ambient RGM measurements, were developed and evaluated. Following collection of RGM onto KCl-coated quartz annular denuders, RGM was thermally decomposed and quantified as Hg0. Laboratory and field evaluations of the denuders found the RGM collection efficiency to be >94% and mean collocated precision to be <15%. Method detection limits for sampling durations ranging from 1 to 12 h were 6.2-0.5 pg m(-3), respectively. As part of this research, the authors observed that methods to measure Hg(p) had a significant positive artifact when RGM coexists with Hg(p). This artifact was eliminated if a KCl-coated annular denuder preceded the filter. This new atmospheric mercury speciation methodology has dramatically enhanced our ability to investigate the mechanisms of transformation and deposition of mercury in the atmosphere.

Air Pollutants↗
PubMed2002

National policies for biosphere greenhouse gas management: issues and opportunities.

Biosphere greenhouse gas (GHG) management consists of preserving and enhancing terrestrial carbon pools and producing biomass as a fossil fuel substitute. The discussion of this topic has focused primarily on carbon-accounting and project-level issues, particularly relating to carbon sequestration as a source of emissions credits under the Kyoto Protocol. While international consensus on these matters is needed, this paper argues that an important domestic policy agenda also deserves attention. National policies for biosphere GHG management are necessary to bring about large-scale changes in land-use, forestry, and agricultural practices and can address some of the technical and policy issues that have proven to be particularly problematic from carbon-accounting and project-level perspectives. These policies should minimize land-use and resource-management conflicts, account for collateral benefits, and ensure institutional compatibility with existing resource-management regimes. Issues relating to project permanence, leakage, and transaction costs should also be addressed. A range of policy instruments should be used and biosphere GHG management should be one component of an integrated approach to environmental and resource management. Countries promoting biosphere GHG management as an important element of their climate change strategies should be developing these domestic policies to complement international negotiations and to demonstrate that carbon sequestration and biomass production can make an effective contribution to the stabilization of atmospheric GHG concentrations.

Air Pollution↗
PubMed2002

A technical, economic, and environmental assessment of amine-based CO2 capture technology for power plant greenhouse gas control.

Capture and sequestration of CO2 from fossil fuel power plants is gaining widespread interest as a potential method of controlling greenhouse gas emissions. Performance and cost models of an amine (MEA)-based CO2 absorption system for postcombustion flue gas applications have been developed and integrated with an existing power plant modeling framework that includes multipollutant control technologies for other regulated emissions. The integrated model has been applied to study the feasibility and cost of carbon capture and sequestration at both new and existing coal-burning power plants. The cost of carbon avoidance was shown to depend strongly on assumptions about the reference plant design, details of the CO2 capture system design, interactions with other pollution control systems, and method of CO2 storage. The CO2 avoidance cost for retrofit systems was found to be generally higher than for new plants, mainly because of the higher energy penalty resulting from less efficient heat integration as well as site-specific difficulties typically encountered in retrofit applications. For all cases, a small reduction in CO2 capture cost was afforded by the SO2 emission trading credits generated by amine-based capture systems. Efforts are underway to model a broader suite of carbon capture and sequestration technologies for more comprehensive assessments in the context of multipollutant environmental management.

Absorption↗
PubMed2002

Transcription factor activation following exposure of an intact lung preparation to metallic particulate matter.

Metallic constituents contained in ambient particulate matter have been associated with adverse effects in a number of epidemiologic, in vitro, and in vivo studies. Residual oil fly ash (ROFA) is a metallic by-product of the combustion of fossil fuel oil, which has been shown to induce a variety of proinflammatory responses in lung cells. We have examined signaling pathways activated in response to ROFA exposure and recently reported that ROFA treatment activates multiple mitogen-activated protein (MAP) kinases in the rat lung. In the present study we extended our investigations on the mechanism of toxicity of ROFA to include transcription factors whose activities are regulated by MAP kinases as well as possible effectors of transcriptional changes that mediate the effects of ROFA. We applied immunohistochemical methods to detect ROFA-induced activation of nuclear factor-kappa B (NF kappa B), activating transcription factor-2 (ATF-2), c-Jun, and cAMP response element binding protein (CREB) in intact lung tissue and confirmed and characterized their functional activation using DNA binding assays. We performed these studies using a perfused rabbit lung model that is devoid of blood elements in order to distinguish between intrinsic lung cell effects and effects that are secondary to inflammatory cell influx. We report here that exposure to ROFA results in a rapid activation of all of the transcription factors studied by exerting direct effects on lung cells. These findings validate the use of immunohistochemistry to detect transcription factor activation in vivo and demonstrate the utility of studying signaling changes in response to environmental exposures.

Activating Transcription Factor 2↗
PubMed2002

Impacts of urban greenspace on offsetting carbon emissions for middle Korea.

Carbon dioxide is an important greenhouse gas and a major agent of climate change. This study quantified carbon (C) emissions from energy consumption and C storage and uptake by greenspace for three cities in middle Korea: Chuncheon, Kangleung, and Seoul. Carbon emissions were estimated using C emission coefficients for fossil fuels consumed. Carbon storage and uptake by woody plants were computed applying biomass equations and radial growth rates. The soils in Chuncheon were cored to analyze organic C storage. Annual C emissions were 37.0 t/ha/yr in Kangleung, 47.2 t/ha/yr in Chuncheon, and 264.9 t/ha/yr in Seoul. Mean C storage by woody plants ranged from 26.0 to 60.1 t/ha for natural lands within the study cities, and from 4.7 to 7.2 t/ha for urban lands (all land use types except natural and agricultural lands). Mean annual C uptake by woody plants ranged from 1.60 to 3.91 t/ha/yr for natural lands within the cities, and from 0.53 to 0.80 t/ha/yr for urban lands. There were no significant differences (95% confidence level) between the cities in C storage and uptake per ha for urban lands. Organic C storage in Chuncheon soils (to a depth of 60 cm) averaged 31.6 t/ha for natural lands and 24.8 t/ha for urban lands. Woody plants stored an amount of C equivalent to 6.0-59.1% of total C emissions within the cities, and annually offset total C emissions by 0.5-2.2%. Carbon storage in soils was 1.2 times greater than that by woody plants in Chuncheon. The C reduction benefits of woody plants were greater in Chuncheon and Kangleung, where areal distribution of natural lands was larger and the population density lower than in Seoul. Strategies to increase C storage and uptake by urban greenspace were explored.

Carbon↗
PubMed2005

The avoidable health effects of air pollution in three Latin American cities: Santiago, São Paulo, and Mexico City.

Urban centers in Latin American often face high levels of air pollution as a result of economic and industrial growth. Decisions with regard to industry, transportation, and development will affect air pollution and health both in the short term and in the far future through climate change. We investigated the pollution health consequences of modest changes in fossil fuel use for three case study cities in Latin American: Mexico City, Mexico; Santiago, Chile; and São Paulo, Brazil. Annual levels of ozone and particulate matter were estimated from 2000 to 2020 for two emissions scenarios: (1) business-as-usual based on current emissions patterns and regulatory trends and (2) a control policy aimed at lowering air pollution emissions. The resulting air pollution levels were linked to health endpoints through concentration-response functions derived from epidemiological studies, using local studies where available. Results indicate that the air pollution control policy would have vast health benefits for each of the three cities, averting numerous adverse health outcomes including over 156,000 deaths, 4 million asthma attacks, 300,000 children's medical visits, and almost 48,000 cases of chronic bronchitis in the three cities over the 20-year period. The economic value of the avoided health impacts is roughly 21 to 165 billion Dollars (US). Sensitivity analysis shows that the control policy yields significant health and economic benefits even with relaxed assumptions with regard to population growth, pollutant concentrations for the control policy, concentration-response functions, and economic value of health outcomes. This research demonstrates the health and economic burden from air pollution in Latin American urban centers and the magnitude of health benefits from control policies.

Adolescent↗
PubMed2005

Source apportionment of organic pollutants of a highway-traffic-influenced urban area in Bayreuth (Germany) using biomarker and stable carbon isotope signatures.

Traffic- and urban-influenced areas are prone to enhanced pollution with products of incomplete combustion of fossil fuels and biomass such as black carbon or polycyclic aromatic hydrocarbons (PAHs). Black carbon is composed of aromatic and graphitic structures and may act as a carrier for pollutants such as PAHs and heavy metals. However, little is known about possible contributions of traffic-derived black carbon to the black carbon inventory in soils. Similar uncertainties exist regarding the contribution of different pollutant sources to total PAH and black carbon contents. Therefore, the objective of this study was to quantify the importance of traffic pollution to black carbon and PAH inventories in soils. PAH contamination of soils adjacent to a major German highway in the urban area of Bayreuth with about 50,000 vehicles per day was in the same order of magnitude compared to highway-close soils reported in other studies. Using molecular (black carbon and PAHs) and compound-specific stable carbon isotope evidence (PAHs) it was demonstrated that this contamination originated not only from automobile exhausts, here primarily diesel, but also from tire abrasion and tailpipe soot which significantly contributed to the traffic-caused black carbon and PAH contamination. Low molecular weight PAHs were more widely transported than their heavy molecular counterparts (local distillation), whereas highway-traffic-caused black carbon contamination was distributed to at least 30 m from the highway. On the other hand, urban fire exhausts were distributed more homogeneously among the urban area.

Air Pollutants↗
PubMed2002

Nitric oxide reduction in coal combustion: role of char surface complexes in heterogeneous reactions.

Nitrogen oxides are one of the major environmental problems arising from fossil fuel combustion. Coal char is relatively rich in nitrogen, and so this is an important source of nitrogen oxides during coal combustion. However, due to its carbonaceous nature, char can also reduce NO through heterogeneous reduction. The objectives of this work were on one hand to compare NO emissions from coal combustion in two different types of equipment and on the other hand to study the influence of char surface chemistry on NO reduction. A series of combustion tests were carried out in two different scale devices: a thermogravimetric analyzer coupled to a mass spectrometer and an FTIR (TG-MS-FTIR) and a fluidized bed reactor with an on line battery of analyzers. The TG-MS-FTIR system was also used to perform a specific study on NO heterogeneous reduction reactions using chars with different surface chemistry. According to the results obtained, it can be said that the TG-MS-FTIR system provides valuable information about NO heterogeneous reduction and it can give good trends of the behavior in other combustion equipments (i.e., fluidized bed combustors). It has been also pointed out that NO-char interaction depends to a large extent on temperature. In the low-temperature range (<800 degrees C), NO heterogeneous reduction seems to be controlled by the evolution of surface complexes. In the high-temperature range (>800 degrees C), a different mechanism is involved in NO heterogeneous reduction, the nature of the carbon matrix being a key factor.

Carbon Dioxide↗
PubMed1998

Induction of apoptosis by particulate matter: role of TNF-alpha and MAPK.

Particulate matter (PM) is a major by-product from the combustion of fossil fuels. The biological target of inhaled PM is the pulmonary epithelium and resident macrophages. In this study, we demonstrate that cultured macrophages (RAW 264.7 cells) exposed continously to a well-defined model of PM [benzo[a]pyrene adsorbed on carbon black (CB+BaP)] exhibit a time-dependent expression and release of the cytokine tumor necrosis factor-alpha (TNF-alpha). CB+BaP also evoked programmed cell death or apoptosis in cultured macrophages as assessed by genomic DNA-laddering assays. The CB+BaP-induced apoptosis was inhibited when macrophages were treated with CB+BaP in the presence of a neutralizing antibody to TNF-alpha, suggesting that TNF-alpha plays an important role in mediating CB+BaP-induced apoptosis in macrophages. Interestingly, neither untreated carbon black nor benzo[a]pyrene alone induced apoptosis or caused the release of TNF-alpha in RAW 264.7 cells. Moreover, we observed that TNF-alpha activates mitogen-activated protein kinase (MAPK) activity, the extracellular signal-regulated kinases p42/p44, in a time-dependent manner. RAW 264.7 cells treated with PD-098059, a selective inhibitor of MAPK kinase activity, did not exhibit CB+BaP-induced apoptosis and TNF-alpha secretion. Furthermore, cells treated with the MAPK kinase inhibitor did not undergo TNF-alpha-induced apoptosis. Taken together, our data suggest that TNF-alpha mediates PM-induced apoptosis and that the MAPK pathway may play an important role in regulating this pathway.

Adsorption↗
PubMed2005

Prenatal ambient air exposure to polycyclic aromatic hydrocarbons and the occurrence of respiratory symptoms over the first year of life.

The purpose of the study was to test the hypothesis that infants with higher levels of prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) from fossil fuel combustion may be at greater risk of developing respiratory symptoms. The study was carried out in a cohort of 333 newborns in Krakow, Poland, followed over the first year of life, for whom data from prenatal personal air monitoring of mothers in the second trimester of pregnancy were available. The relative risks of respiratory symptoms due to prenatal PAHs exposure were adjusted for potential confounders (gender of child, birth weight, maternal atopy, maternal education as a proxy for the socio-economic status, exposure to postnatal environmental tobacco smoke, and moulds in households) in the Poisson regression models. Increased risk related to prenatal PAH exposure was observed for various respiratory symptoms such as barking cough (RR = 4.80; 95% CI: 2.73-8.44), wheezing without cold (RR = 3.83; 95% CI: 1.18-12.43), sore throat (RR = 1.96; 95% CI: 1.38-2.78), ear infection (RR = 1.82; 95% CI: 1.03-3.23), cough irrespective of respiratory infections (RR=1.27; 95% CI: 1.07-1.52), and cough without cold (RR = 1.72; 95% CI: 1.02-2.92). The exposure to PAHs also had impact on the duration of respiratory symptoms. The effect of PAHs exposure on the occurrence of such symptoms as runny nose or cough was partly modified by the simultaneous exposure to postnatal passive smoking. The analysis performed for the duration of respiratory symptoms confirmed significant interaction between PAHs exposure and postnatal ETS for runny or stuffy nose (RR = 1.82; 95% CI: 1.57-2.10), cough (RR = 1.18; 95% CI: 0.99-1.40), difficulty in breathing (RR = 1.39; 95% CI: 1.01-1.92) and sore throat (RR = 1.74; 1.26-2.39). Obtained results support the hypothesis that prenatal exposure to immunotoxic PAHs may impair the immune function of the fetus and subsequently may be responsible for an increased susceptibility of newborns and young infants to respiratory infections.

Adolescent↗
PubMed1984

The induction of sister chromatid exchanges by environmental pollutants: relationship of SCE to other measures of genetic damage.

Sister chromatid exchanges (SCEs), induced by environmental pollutants from fossil fuel use, were measured in 2 cell systems, Chinese hamster ovary (CHO) cells and Chinese hamster primary lung cell cultures. The frequency of SCEs induced in these cell systems was related to other measures of genetic damage, namely mutations in CHO cells at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) gene locus and in bacteria (Salmonella mutagenicity test TA-98), produced by the same pollutants. The pollutants were divided into 2 classes: those produced in oxidizing combustion environments--extracts of particles from light-duty diesel cars, spark-ignition cars, and an automotive tunnel; and those produced in reducing environments--extracts from coke oven mains and condensates from a low BTU coal gasifier obtained either before or after cleanup of the process stream. Sister chromatid exchanges were induced by all pollutants without the addition of a rat liver microsomal fraction (S-9 mix), whereas S-9 mix was required to induce a positive response in the CHO/HGPRT assay for all pollutants. The pollutants produced in a reducing environment required metabolic activation by S-9 mix to be mutagenic in the Salmonella mutation assay. The addition of S-9 mix to pollutants produced in an oxidizing environment reduced the response in the Salmonella test. The relative genotoxic potency for each pollutant was determined for all 3 endpoints. The slopes of dose-response curves for each pollutant were plotted for each assay to compare relative potency. When the bacterial mutagenicity test was compared to either mammalian cell assay, SCE or CHO/HGPRT, there was little correlation between relative potencies. However, the data indicated that the responses in the 2 mammalian cell assays, SCE and CHO/HGPRT, showed similar relative responses to the pollutants. Differences in the requirement for S-9 mix seem to be related to both the chemical nature of the mixture and the endpoint measured. Differences in responses are related not only to cell type but also to chemical composition of the complex pollutants.

Air Pollutants↗
PubMed2003

A three-stage system to remove mercury and dioxins in flue gases.

Mercury (Hg) from combustion of fossil fuels and waste is the dominant source of anthropogenic Hg emissions, globally amounting to more than 1500 t Hgyear(-1). These emissions must decrease substantially in order to counteract increasing environmental levels of Hg and reduce future toxic effects. Uppsala Energi AB, nowadays (May, 2002) Vattenfall Värme Uppsala AB, an energy company in Uppsala, Sweden, has invested in equipments for air and water pollution control of their three waste fired steam boilers. The flue gases are cleaned in three stages in series to meet the strict Swedish regulation. Electrostatic precipitators remove most dust in the first stage, wet scrubbers remove most water-soluble gases, and in the last stage a Filsorption unit removes most remaining impurities in particulate as well as gaseous form. The Filsorption process includes additives injection, sorption, and chemical reaction in a reactor and filtration with a fabric filter. The aim with this article is to evaluate the efficiency of the system to recover Hg in flue gases from boilers in routine operation. Flue gases, ashes, and water were sampled yearly for 21 years and analysed for Hg, dioxin, and other potential contaminants received at waste incineration. The results clearly demonstrate the decreasing use of Hg in society the last two decades as influenced by governmental policy regarding Hg. The results also indicate that the equipment efficiently removed Hg and dioxins from the flue gases to a final concentration of approximately 3.5 microg Hgm(-3) n and 0.01 ng dioxinsm(-3) n, corresponding to more than 97 and 99.9% reduction of Hg and dioxins, respectively, by cleaning in three stages. The electrostatic precipitators and Filsorption stages alone, with the scrubber in bypass, removed 90% of Hg in flue gases. Using the scrubber is motivated to remove acid components and additional Hg, but call for water separated after the condensers to be neutralised and cleaned, so that less than 5 microg l(-1) Hg and 0.02 ngl(-1) dioxins remained, before the water was discharged to a recipient. In conclusion, cleaning flue gases in two or three stages reduced Hg emissions well below Swedish regulations. The strict measures to prevent pollution from waste incineration and simultaneously make use of the energy produced are a good example of a local solution for a global problem.

Adsorption↗
PubMed1996

Coal tar, pine tar and sulfonated shale oil preparations: comparative activity, efficacy and safety.

BACKGROUND: Tar and sulfonated shale oil preparations are used in the treatment of a variety of inflammatory skin diseases, including psoriasis vulgaris; due to the high polycyclic aromatic hydrocarbon (PAH) content of tars, a possible relationship with cancer in humans has been postulated. On the other hand, the purity of sulfonated shale oils concerning PAHs guarantees a good tolerability during dermatologic therapy. AIM: In this review, it is attempted to compare activity, efficacy and safety of coal tar, pine tar and sulfonated shale oil preparations which currently play a role in dermatologic treatment. RESULTS AND CONCLUSIONS: Primary sources of PAHs in the normal human environment are forest fires, cigarette smoke and combustion of fossil fuels for heating and energy. Thermal processing of fossil substances is also required for the production of tars and sulfonated shale oils. Due to individual manufacturing techniques, tars and sulfonated shale oils differ completely in their chemical composition. Still, sulfonated shale oils are often falsely grouped as tars because of their related origin and similar dermatologic indications. There is at least limited evidence of the activity and efficacy of various tars as well as sulfonated shale oil preparations in different frequent inflammatory skin diseases. This includes psoriasis vulgaris and atopic eczema of glabrous as well as hairy skin. There is still some concern about the long-term tolerability of tar preparations at least in some contexts. This, however, does not apply to sulfonated shale oil preparations. Consequently, at least their use should still be considered a rational drug treatment in dermatology.

Animals↗
PubMed1990

[Current status of air pollution in Sao Paulo, Brazil: effects and problems associated with the introduction of ethanol-fueled motor vehicles].

Recently suggestions have been advanced that alternative fuels including ethanol, methanol or methane instead of so called "fossil fuels" may help improve the current conditions of air pollution. According to results of general survey in Sao Paulo, since their introduction in 1978, ethanol-fueled cars have increased their share to almost 50% of all light vehicles in 1983. The current status of air pollution in Sao Paulo metropolitan area (SPMA) is described in relation to the use of such alternative fuel. The average concentrations in air of SO2 and lead have been decreasing drastically during the period of 1982-88, whereas non-methane hydrocarbon, NO2 and O3 levels have been increasing to attain the worst levels in the world as indicated in Fig. 2. The use of ethanol-fuel, which contains less sulphate and lead, is thought to have contributed more or less to the above reductions of SO2 and lead in the air. However, the pollutants that have increased may derive mainly from diesel and gasoline exhausts of heavy vehicles. The general state of air pollutions appears not to have been improved, suggesting the difficulty in resolving air pollution issues. On the other hand, a current problem specific to ethanol-fuel is the aldehydes or other carcinogenic components in exhaust. Peak formaldehyde concentration, for example, have been reported to have reached 159 ppb in SPMA, which may be one of the highest levels shown in ambient air.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollution↗
PubMed2004

High yield bio-oil production from fast pyrolysis by metabolic controlling of Chlorella protothecoides.

The use of renewable energy sources is becoming increasingly necessary to mitigate global warming. Recently much research has been focused on identifying suitable biomass species, which can provide high-energy outputs, to replace conventional fossil fuels. This paper reports an approach for increasing the yield of bio-oil production from fast pyrolysis after manipulating the metabolic pathway in microalgae through heterotrophic growth. The yield of bio-oil (57.9%) produced from heterotrophic Chlorella protothecoides cells was 3.4 times higher than from autotrophic cells by fast pyrolysis. The bio-oil was characterized by a much lower oxygen content, with a higher heating value (41 MJ kg(-1)), a lower density (0.92 kg l(-1)), and lower viscosity (0.02 Pas) compared to those of bio-oil from autotrophic cells and wood. These properties are comparable to fossil oil. The research could contribute to the creation of a system to produce energy from microalgae, and also could have great commercial potential for liquid fuel production.

Chlorella↗