An analysis of the energy life-cycle for production of biomass using the oil-rich microalgae Nannochloropsis sp. was performed, which included both raceway ponds, tubular and flat-plate photobioreactors for algal cultivation. The net energy ratio (NER) for each process was calculated. The results showed that the use of horizontal tubular photobioreactors (PBRs) is not economically feasible ([NER]<1) and that the estimated NERs for flat-plate PBRs and raceway ponds is >1. The NER for ponds and flat-plate PBRs could be raised to significantly higher values if the lipid content of the biomass were increased to 60% dw/cwd. Although neither system is currently competitive with petroleum, the threshold oil cost at which this would occur was also estimated.

Ciliary membrane fragment fusion to planar lipid bilayers resulted in the insertion of four ion channel types. cAMP-activated, cation-selective channels could be detected only in the absence of Ca2+ and had a conductance of 23 pS. They exhibited an apparent dissociation constant (Kd) for the cyclic nucleotide of approximately 30 microM and an estimated permeability ratio (PNa/PK) of 2.4. The cAMP cation-selective channel coinserted with a K(+)-selective channel refractory to cAMP, Ca2+, and D-myo-inositol 1,4,5-trisphosphate. This K+ channel was voltage independent and exhibited open-conductance substates of 60 and 112 pS. cAMP was also found to modulate a novel K+ channel with a Kd = 140 microM. It displayed three nearly equally spaced open substates with conductances of 34, 80, and 130 pS. In the absence and in the presence of cAMP the probability of occurrence of the open substates was binomially distributed. A fourth channel type was a Ca(2+)-activated K+ channel with a conductance of 240 pS. It was blocked by charybdotoxin at nanomolar concentrations (Kd = 3 nM). These results add support to the idea that, besides cAMP-activated cation-selective channels, vertebrate chemosensory olfactory membranes possess an arrangement of ion channels.

15Ethylic transesterification process for biodiesel production without any 16 chemical or biochemical catalysts at different subcritical thermodynamic con-17 ditions was performed using wet animal fat, soybean and palm oils as feed-18 stock. The results indicate that 2h of reaction at 240 o C with pressures vary-19ing from 20 to 45 bar was sufficient to transform almost all lipid fraction of 20 the samples to biodiesel, depending on the reactor dead volume and propor-21 tions between reactants. Conversions of 100%, 84% and 98.5% were obtained 22 for animal fat, soybean oil and palm oil, respectively, in the presence of wa-23 ter, with a net energy ration values of 2.6, 2.1 and 2.5 respectively. These 24 results indicate that the process is energetically favorable, and thus repre-25 sents a cleaner technology with environmental advantages when compared to 26 traditional esterification or transesterification processes. 27 2 28 Nomenclature. 29 AF: animal fat; FFA: free fatty acids; FAEEs: fatty acid ethyl esters; 30FAMEs: fatty acid methyl esters; GC: gas chromatography; IS: internal 31 standard; NER: Net Energy Ratio; TG: triglycerides; TGpcar: TG peak 32 corrected after reaction; TGpar: TG peak area after reaction; TGpbr: TG 33 peak area before reaction; ISpbr: IS peak area before reaction; ISpar: IS 34 peak area after reaction; TGtc: TG total conversion; TGpcar: TG peak 35 corrected area after reaction; FAEEsmax: Maximum possible formation of 36 FAEEs peak area; FFApbr: FFA peak area before reaction; E FAEEs : Energy 37 obtained from FAEEs; E cpm : Energy consumption from the power meter; 38 E rfr : Energy requirements for the reaction. 39 1. Introduction 40 The transesterification reaction of vegetable oils to produce fatty acid 41 methyl or ethyl esters (FAMEs or FAEEs) can be catalyzed by acids, bases 42 or enzymes, among other processes [1]. The predominant FAMEs employed 43 in the biodiesel industry in the world are derived from soybean, rapeseed, 44 and palm oils [2]. Currently, most commercial processes employ methanol 45 to perform the transesterification of triglycerides, catalyzed by a strong base 46 (KOH) in a homogeneous process to produce FAMEs. This is due to the 47 fast transesterification reaction in the presence of alcohol soluble bases and 48 to the low cost of alkaline material, but this process involves many treat-49 ment steps previous to and post-reaction, with generation of large amounts 50 of effluents and waste. Besides, the use of a soluble base as a catalyst is 51 not suitable for processing low quality raw materials, such as animal fat and 52 palm oil that usually contain traces of water and high amounts of free fatty 53 acids which readily react via the saponification reaction, generating soaps 54 and hindering the separation of the products, consumes the catalyst and re-55 duces its efficiency[3]. Likozar and Levec [4] performed a very detailed kinetic 56 study of the transesterification reaction of various vegetable oils, using vari-57 ous alcohols, via homogeneous catalysis with K...

In this study a critical analysis of input parameters on a model to describe the broth temperature in flat plate photobioreactors throughout the day is carried out in order to assess the effect of these parameters on the model. Using the design of experiment approach, variation of selected parameters was introduced and the influence of each parameter on the broth temperature was evaluated by a parametric sensitivity analysis. The results show that the major influence on the broth temperature is that from the reactor wall and the shading factor, both related to the direct and reflected solar irradiation. Other parameter which play an important role on the temperature is the distance between plates. This study provides information to improve the design and establish the most appropriate operating conditions for the cultivation of microalgae in outdoor systems.

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