984 research outputs found
Méthodologie d'éconconception pour un procédé innovant: la bioélétrosynthÚse des déchets organiques
International audienceBulk chemicals and liquid fuels are currently produced almost exclusively from petrochemical feedstock. In the light of emission reduction targets and the dependence on non renewable resources, the production of the same or functionally equivalent chemicals from renewable resources may play an important role [1, 2]. The project BIORARE (Bioelectrosynthesis for the refinery of residual waste) was set up to contribute to this objective. Its purpose is to use microbial electrosynthesis for the direct production of fuels and chemicals from organic waste and CO2 (see figure 1). Ecoconception is used to help to make choices. This is this work which is study.In a first step, we had to determine which parameters of the Bioelectrosynthesis (BES) could be the most impacting ones to define the priorities to be considered to minimize the potential impacts of the entire process. Some flows could be sensitive: the nature and the quantity of outputs, the nature and the quantity of materials, and the amount of energy used. The inventory of these flows had to be the first step. Thanks to databases and literature four have been identified as sensitive: electrodes, membrane, energy and chemicals produced.After determining this, we have to design the model for coupling anaerobic digestion to the BES. This was realized using Life Cycle Assessment approach. The goal of this assessment is to determine the relative influence of various target parameters on the impacts of the process. For example, results will allow assessing if the choice of a material for the electrode could have a significant influence on total impacts. Our methodology illustrates to what extend Life Cycle Assessment could help for the conception of a process, through the evaluation of the contribution of various parameters to the impacts. After, it is possible to integrate them into a model to determine what impacts they could have on the whole production chemicals or fuels from organic waste system.ACV de production de bioéthanol par bioélectrosynthÚse de déchets organiques
Analyse du cycle de vie d'un systÚme bioélectrochimique en tant que plate-forme technologique innovante pour la production d'acide succinique à partir de déchets
International audienceWaste management is a key environmental and socio-economic issue. Environmental concerns are encouraging the use of alternative resources and lower emissions to air, water and soil. Innovative technologies to deal with waste recovery that produce marketable bioproducts are emerging. Bioelectrochemical synthesis systems (BESs) are based on the primary principle of transforming organic waste into added-value products using microorganisms to catalyse chemical reactions. This technology is at the core of a research project called BIORARE (BIoelectrosynthesis for ORganic wAste bioREfinery), an interdisciplinary project that aims to use anaerobic digestion as a supply chain to feed a BES and produce target biomolecules. This technology needs to be driven by environmental strategies. Life Cycle Assessment (LCA) was used to evaluate the BIORARE concept based on expert opinion and prior experiments for the production of biosuccinic acid and waste management. A multidisciplinary approach based on biochemistry and process engineering expertise was used to collect the inventory data. The BES design and the two-step anaerobic digestion process have many potential impacts on air pollution or ecotoxicity-related categories. The comparison of the BIORARE concept with conventional fermentation processes and a water-fed BES technology demonstrated the environmental benefit resulting from the use of both the BES technology and a waste-based substrate as input thus supporting the BIORARE concept. Some trade-offs among the impact categories were identified but led to options to improve the concept. BES design and synergy management may improve the environmental performance of the BIORARE concep
A Broadband Study of Galactic Dust Emission
We have combined infrared data with HI, H2 and HII surveys in order to
spatially decompose the observed dust emission into components associated with
different phases of the gas. An inversion technique is applied. For the
decomposition, we use the IRAS 60 and 100 micron bands, the DIRBE 140 and 240
micron bands, as well as Archeops 850 and 2096 micron wavelengths. In addition,
we apply the decomposition to all five WMAP bands. We obtain longitude and
latitude profiles for each wavelength and for each gas component in carefully
selected Galactic radius bins.We also derive emissivity coefficients for dust
in atomic, molecular and ionized gas in each of the bins.The HI emissivity
appears to decrease with increasing Galactic radius indicating that dust
associated with atomic gas is heated by the ambient interstellar radiation
field (ISRF). By contrast, we find evidence that dust mixed with molecular
clouds is significantly heated by O/B stars still embedded in their progenitor
clouds. By assuming a modified black-body with emissivity law lambda^(-1.5), we
also derive the radial distribution of temperature for each phase of the gas.
All of the WMAP bands except W appear to be dominated by emission from
something other than normal dust, most likely a mixture of thermal
bremstrahlung from diffuse ionized gas, synchrotron emission and spinning dust.
Furthermore, we find indications of an emissivity excess at long wavelengths
(lambda > 850 micron) in the outer Galaxy (R > 8.9 kpc). This suggests either
the existence of a very cold dust component in the outer Galaxy or a
temperature dependence of the spectral emissivity index. Finally, it is shown
that ~ 80% of the total FIR luminosity is produced by dust associated with
atomic hydrogen, in agreement with earlier findings by Sodroski et al. (1997).Comment: accepted for publication by A&
Submillimeter mapping and analysis of cold dust condensations in the Orion M42 star forming complex
We present here the continuum submillimeter maps of the molecular cloud
around the M42 Nebula in the Orion region. These have been obtained in four
wavelength bands (200, 260, 360 and 580 microns) with the ProNaOS two meter
balloon-borne telescope. The area covered is 7 parsecs wide (50 arcmin at a
distance of 470 pc) with a spatial resolution of about 0.4 parsec. Thanks to
the high sensitivity to faint surface brightness gradients, we have found
several cold condensations with temperatures ranging from 12 to 17 K, within 3
parsecs of the dense ridge. The statistical analysis of the temperature and
spectral index spatial distribution shows an evidence of an inverse correlation
between these two parameters. Being invisible in the IRAS 100 micron survey,
some cold clouds are likely to be the seeds for future star formation activity
going on in the complex. We estimate their masses and we show that two of them
have masses higher than their Jeans masses, and may be gravitationally
unstable.Comment: 4 figures, The Astrophysical Journal, Main Journal, in pres
The Anatomy of Star Formation in NGC 300
The Spitzer Space Telescope was used to study the mid-infrared to
far-infrared properties of NGC 300, and to compare dust emission to Halpha to
elucidate the heating of the ISM and the star formation cycle at scales < 100
pc. The new data allow us to discern clear differences in the spatial
distribution of 8 micron dust emission with respect to 24 micron dust and to
HII regions traced by the Halpha light. The 8 micron emission highlights the
rims of HII regions, and the 24 micron emission is more strongly peaked in star
forming regions than at 8 microns. We confirm the existence and approximate
amplitude of interstellar dust emission at 4.5 microns, detected statistically
in Infrared Space Observatory (ISO) data, and conclude it arises in star
forming regions. When averaging over regions larger than ~ 1 kpc, the ratio of
Halpha to Aromatic Feature emission in NGC 300 is consistent with the values
observed in disks of spiral galaxies. The mid-to-far-infrared spectral energy
distribution of dust emission is generally consistent with pre-Spitzer models.Comment: to appear in the ApJS Spitzer special issue (September 2004
Planck's Dusty GEMS: Gravitationally lensed high-redshift galaxies discovered with the Planck survey
We present an analysis of 11 bright far-IR/submm sources discovered through a
combination of the Planck survey and follow-up Herschel-SPIRE imaging. Each
source has a redshift z=2.2-3.6 obtained through a blind redshift search with
EMIR at the IRAM 30-m telescope. Interferometry obtained at IRAM and the SMA,
and optical/near-infrared imaging obtained at the CFHT and the VLT reveal
morphologies consistent with strongly gravitationally lensed sources.
Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 um
and 2 mm, respectively. All objects are bright, isolated point sources in the
18 arcsec beam of SPIRE at 250 um, with spectral energy distributions peaking
either near the 350 um or the 500 um bands of SPIRE, and with apparent
far-infrared luminosities of up to 3x10^14 L_sun. Their morphologies and sizes,
CO line widths and luminosities, dust temperatures, and far-infrared
luminosities provide additional empirical evidence that these are strongly
gravitationally lensed high-redshift galaxies. We discuss their dust masses and
temperatures, and use additional WISE 22-um photometry and template fitting to
rule out a significant contribution of AGN heating to the total infrared
luminosity. Six sources are detected in FIRST at 1.4 GHz. Four have flux
densities brighter than expected from the local far-infrared-radio correlation,
but in the range previously found for high-z submm galaxies, one has a deficit
of FIR emission, and 6 are consistent with the local correlation. The global
dust-to-gas ratios and star-formation efficiencies of our sources are
predominantly in the range expected from massive, metal-rich, intense,
high-redshift starbursts. An extensive multi-wavelength follow-up programme is
being carried out to further characterize these sources and the intense
star-formation within them.Comment: A&A accepte
A multiwavelength study of Galactic HII region Sh2-294
We present the observational results of Galactic HII region S294, using
optical photometry, narrow-band imaging and radio continuum mapping at 1280
MHz, together with archival data from 2MASS, MSX and IRAS surveys. The stellar
surface density profile indicates that the radius of the cluster associated
with the S294 region is ~ 2.3 arcmin. We found an anomalous reddening law for
the dust inside the cluster region and the ratio of total-to-selective
extinction is found to be 3.8+-0.1. We estimate the minimum reddening E (B-V) =
1.35 mag and distance of 4.8+-0.2 kpc to the region from optical CC and CM
diagrams. We identified the ionizing source of the HII region, and spectral
type estimates are consistent with a star of spectral type ~ B0 V. The 2MASS
JHKs images reveal a partially embedded cluster associated with the ionizing
source along with a small cluster towards the eastern border of S294. The
ionization front seen along the direction of small cluster in radio continuum
and Halpha images, might be due to the interaction of ionizing sources with the
nearby molecular cloud. We found an arc shaped diffuse molecular hydrogen
emission at 2.12 micron and a half ring of MSX dust emission which surrounds
the ionized gas in the direction of the ionization front. Self consistent
radiative transfer model of mid- to far-infrared continuum emission detected
near small cluster is in good agreement with the observed spectral energy
distribution of a B1.5 ZAMS star. The morphological correlation between the
ionised and molecular gas, along with probable time scale involved between the
ionising star, evolution of HII region and small cluster, indicates that the
star-formation activity observed at the border is probably triggered by the
expansion of HII region.Comment: 50 pages, 21 figures: Accepted by The Astrophysical Journal; Also
available at http://www.tifr.res.in/~ojha/S294.pd
Warm molecular hydrogen in the Spitzer SINGS galaxy sample
(simplified) Results on the properties of warm H2 in 57 normal galaxies are
derived from H2 rotational transitions, obtained as part of SINGS. This study
extends previous extragalactic surveys of H2, the most abundant constituent of
the molecular ISM, to more common systems (L_FIR = e7 to 6e10 L_sun) of all
morphological and nuclear types. The S(1) transition is securely detected in
the nuclear regions of 86% of SINGS galaxies with stellar masses above 10^9.5
M_sun. The derived column densities of warm H2 (T > ~100 K), even though
averaged over kiloparsec-scale areas, are commensurate with those of resolved
PDRs; the median of the sample is 3e20 cm-2. They amount to between 1% and >30%
of the total H2. The power emitted in the sum of the S(0) to S(2) transitions
is on average 30% of the [SiII] line power, and ~4e-4 of the total infrared
power (TIR) within the same area for star-forming galaxies, which is consistent
with excitation in PDRs. The fact that H2 emission scales tightly with PAH
emission, even though the average radiation field intensity varies by a factor
ten, can also be understood if both tracers originate predominantly in PDRs,
either dense or diffuse. A large fraction of the 25 LINER/Sy targets, however,
strongly depart from the rest of the sample, in having warmer H2 in the excited
states, and an excess of H2 emission with respect to PAHs, TIR and [SiII]. We
propose a threshold in H2 to PAH power ratios, allowing the identification of
low-luminosity AGNs by an excess H2 excitation. A dominant contribution from
shock heating is favored in these objects. Finally, we detect, in nearly half
the star-forming targets, non-equilibrium ortho to para ratios, consistent with
FUV pumping combined with incomplete ortho-para thermalization by collisions,
or possibly non-equilibrium PDR fronts advancing into cold gas.Comment: ApJS, in pres
The HII Region KR 140: Spontaneous Formation of a High Mass Star
We have used a multiwavelength data set from the Canadian Galactic Plane
Survey (CGPS) to study the Galactic HII region KR 140, both on the scale of the
nebula itself and in the context of the star forming activity in the nearby
W3/W4/W5 complex of molecular clouds and HII regions. From both radio and
infrared data we have found a covering factor of about 0.5 for KR 140 and we
interpret the nebula as a bowl-shaped region viewed close to face on.
Extinction measurements place the region on the near side of its parent
molecular cloud. The nebula is kept ionized by one O8.5 V(e) star, VES 735,
which is less than a few million years old. CO data show that VES 735 has
disrupted much of the original molecular cloud for which the estimated mass and
density are about 5000 and 100 cm, respectively. KR 140 is
isolated from the nearest star forming activity, in W3. Our data suggest that
KR 140 is an example of spontaneous (i.e., non-triggered) formation of,
unusually, a high mass star.Comment: 46 pages; includes 15 figures; accepted by the Ap
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