Electricity production potential from biodiesel, glycerol, and MBM.

<p>Electricity production potential from biodiesel, glycerol, and MBM.</p

Potential revenue in terms of oil & gas savings used for electricity production.

<p>Potential revenue in terms of oil & gas savings used for electricity production.</p

Cumulative projection of slaughterhouse waste and UCO with their relevant GHG emissions potential.

<p>Cumulative projection of slaughterhouse waste and UCO with their relevant GHG emissions potential.</p

Detailed economic analysis of esterification implementation in Makkah city.

<p>Detailed economic analysis of esterification implementation in Makkah city.</p

Projected values of different fat related fraction in Makkah from 2014 to 2050.

<p>Projected values of different fat related fraction in Makkah from 2014 to 2050.</p

Process flow diagram for biodiesel production from fat/oil fraction of MSW in Makkah city.

<p>Process flow diagram for biodiesel production from fat/oil fraction of MSW in Makkah city.</p

Distribution of food waste fractions in Makkah city [14].

<p>Distribution of food waste fractions in Makkah city [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0171297#pone.0171297.ref014" target="_blank">14</a>].</p

Resonant Bonding, Multiband Thermoelectric Transport, and Native Defects in n‑Type BaBiTe_3–<i>x</i>Se_<i>x</i> (<i>x</i> = 0, 0.05, and 0.1)

The unique crystal structure of BaBiTe₃ containing Te···Te resonant bonds and its narrow band gap motivated the systematic study of the thermoelectric transport properties of BaBiTe_3–<i>x</i>Se_<i>x</i> (<i>x</i> = 0, 0.05, and 0.1) presented here. This study gives insight in the chemical bonding and thermoelectric transport properties of BaBiTe₃. The study shows that the presence of Te···Te resonant bonds in BaBiTe₃ is best described as a linear combination of interdigitating (Te^1–)₂ side groups and infinite Te_n chains. Rietveld X-ray structure refinements and extrinsic defect calculations reveal that the substitution of Te by Se occurs preferentially on the Te4 and Te5 sites, which are not involved in Te···Te bonding. This work strongly suggests that both multiband effects and native defects play an important role in the transport properties of BaBiTe_3–<i>x</i>Se_<i>x</i> (<i>x</i> = 0, 0.05, and 0.1). The carrier concentration of BaBiTe₃ can be tuned via Se substitution (BaBiTe_3–<i>x</i>Se_<i>x</i> with <i>x</i> = 0, 0.05, and 0.1) to values near those needed to optimize the thermoelectric performance. The thermal conductivity of BaBiTe_3–<i>x</i>Se_<i>x</i> (<i>x</i> = 0, 0.05, and 0.1) is found to be remarkably low (ca. 0.4 Wm^–1K^–1 at 600 K), reaching values close to the glass limit of BaBiSe₃ (0.34 W m^–1 K^–1) and BaBiTe₃ (0.28 W m^–1 K^–1). Calculations of the defect formation energies in BaBiTe₃ suggest the presence of native Bi_Ba⁺¹ and Te_Bi⁺¹ antisite defects, which are low in energy and likely responsible for the native n-type conduction and the high carrier concentration (ca. 10²⁰ cm^–3) found for all samples. The analyses of the electronic structure of BaBiTe₃ and of the optical absorption spectra of BaBiTe_3–<i>x</i>Se_<i>x</i> (<i>x</i> = 0, 0.05, 0.1, and 3) strongly suggest the presence of multiple electron pockets in the conduction band (CB) in all samples. These analyses also provide a possible explanation for the two optical transitions observed for BaBiTe₃. High-temperature optical absorption measurements and thermoelectric transport analyses indicate that bands higher in the conduction band converge with the conduction band minimum (CBM) with increasing temperature and contribute to the thermoelectric transport properties of BaBiTe₃ and BaBiTe_2.95Se_0.05. This multiband contribution can account for the ∼50% higher <i>zT</i>_max of BaBiTe₃ and BaBiTe_2.95Se_0.05 (∼0.4 at 617 K) compared to BaBiTe_2.9Se_0.1 (∼0.2 at 617 K), for which no such contribution was found. The increase in the band offset between the CBM and bands higher in the conduction band with respect to the selenium content is one possible explanation for the absence of multiband effects in the thermoelectric transport properties of BaBiTe_2.9Se_0.1