Cultivation of four microalgae species in the effluent of anaerobic digester for biodiesel production.

This study investigated if an effluent from anaerobic digestion (AD) system can be used as a nutrients source for the microalgae cultivation, and in so doing, if the effluent can be properly treated. Nitrogen and phosphorus in the AD effluent well supported microalgal growth, and their removal efficiency reached >97.9% and 99.2%, respectively. Among four different algal species tested, Micractinium inermum particularly stood out, showing the highest biomass and FAME productivity: 0.16gL-1d-1 with 3.23gL-1 of dry cell weight, and 0.04gL-1d-1 with 27.54% (w/w) of FAME contents, respectively. As the concentrations of the nutrients decreased over time, the FAME contents were increased and its quality as well, satisfying several biodiesel quality standards. This study supports that the AD effluent can indeed serve as a cheap and nutrient-rich medium for microalgae cultivation, and equally importantly, microalgae can be a workable treatment option for it.

Application of Fe(NO3)3-based as nitrogen source and coagulant for cultivation and harvesting of Chlorella sorokiniana.

In this study, Chlorella sorokiniana was successfully cultivated in the recycled medium whose nitrogen was supplied directly from the coagulant, Fe(NO3)3. With a dosage of 0.80g/L, harvesting efficiency of 95% could be achieved. What is more, this amount of nitrate in the coagulant was enough to fully support the growth of C. sorokiniana during the 8day cultivation period, almost as much as the initial nitrogen content in the BG11 culture medium. Other nutrients had to be supplemented, however, with at least 50% amount as in the BG11 recipe. C. sorokiniana culture grown in recycled medium replenished with 50% of nutrients showed much higher Fatty acid methyl esters (FAME) productivity than the control, with 88.3mg/L/day. The recycle of the medium is certainly a way of reducing the water footprint for the purpose of microalgae-derived biodiesel production; better still, it may serve to lower the nutrient footprint.

Scenedesmus-based treatment of nitrogen and phosphorus from effluent of anaerobic digester and bio-oil production.

In this study, a microalgae-based technology was employed to treat wastewater and produce biodiesel at the same time. A local isolate Scenedesmus sp. was found to be a well suited species, particularly for an effluent from anaerobic digester (AD) containing low carbon but high nutrients (NH3-N=273mgL(-1), total P=58.75mgL(-1)). This algae-based treatment was quite effective: nutrient removal efficiencies were over 99.19% for nitrogen and 98.01% for phosphorus. Regarding the biodiesel production, FAME contents of Scenedesmus sp. were found to be relatively low (8.74% (w/w)), but overall FAME productivity was comparatively high (0.03gL(-1)d(-1)) due to its high biomass productivity (0.37gL(-1)d(-1)). FAMEs were satisfactory to the several standards for the biodiesel quality. The Scenedesmus-based technology may serve as a promising option for the treatment of nutrient-rich wastewater and especially so for the AD effluent.

Ethanol production from oil palm trunks treated with aqueous ammonia and cellulase.

Oil palm trunks are a possible lignocellulosic source for ethanol production. Low enzymatic digestibility of this type of material (11.9% of the theoretical glucose yield) makes pretreatment necessary. An enzymatic digestibility of 95.4% with insoluble solids recovery of 49.8% was achieved after soaking shredded oil palm trunks in ammonia under optimum conditions (80°C, 1:12 solid-to-liquid ratio, 8h and 7% (w/w) ammonia solution). Treatment with 60 FPU of commercial cellulase (Accellerase 1000) per gram of glucan and fermentation with Saccharomyces cerevisiae D(5)A resulted in an ethanol concentration of 13.3g/L and an ethanol yield of 78.3% (based on the theoretical maximum) after 96 h. These results indicate that oil palm trunks are a biomass feedstock that can be used for bioethanol production.