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Biogas Beats Bioethanol by Dr. Wolfgang Bauer

Molecular Marvel - A Novel Catalyst greases the wheels of Biofuel production by Ms Gabrielle Bauer.

To develop biofuel production from waste lignocellulosic biomass materials the rice straw was selected one of renewable material and the degradation condition about pretreatment and enzymatic hydrolysis to obtain effectively fermentable sugars was investigated. Rice straw was pretreated by five kinds of methods and then the components ratio of rice straw was examined. First, the steam explosion was selected based on the degradability and the requirement energy. In addition, the best suitable combination of two cellulases to effective and economical hydrolyze was determined from the degradability of these pretreated rice straws. In the simultaneous saccharification and fermentation of the steam explosion rice straw by combining cellulase cocktail and a novel fermenting fungus, 13.2 g/L ethanol was able to product for 96 h.

Waste Shiitake (Lentinula edodes) mushroom medium, a lignocellulosic aglicultural residue, was evaluated as a fermentable substrate. 87% of the fermentable sugars remained in the waste mushroom medium. The sugar yield of the waste mushroom medium (46.3%) was higher than that of raw mushroom medium (20.3%) after 48 h of enzymatic saccharification by Meicelase because L. edodes changed wood structure. These results indicated that the waste mushroom medium is a suitable substrate for fermentation. Next, the efficient ethanol production using steam explosion pretreatment was studied. After 30 h of simultaneous saccharification and fermentation (SSF) using Meicelase and Saccharomyces cerevisiae AM12, 20.0 g/L ethanol was produced from 100 g/L water-insoluble residue of the waste mushroom medium treated at a steam pressure of 20 atm and a steaming time of 5 min. This corresponded to an ethanol yield of 77.0% of the theoretical, i.e. 14.7 g of ethanol obtained from 100 g of waste mushroom medium.

We performed a cost-benefit analysis for bioethanol production using biomass of Ulva rigida, a marine macroalga (seaweed), co-cultured with fish in an intensive offshore aquaculture unit. This is the first report for such analysis that takes into consideration offshore seaweed cultivation and uses a recently developed, novel and simplified ethanol production technology that is devoid of costly pre-treatments imposed to the seaweed biomass. By simultaneously producing ethanol with valuable Dried Distillers Grains with Solubles (DDGS) by-products such as animal feed, the economic viability of this system is plausible over a production range of 77–240 dry tons of seaweed per day. As such, applying the model to suggested future scenarios for the Israeli Mediterranean shorelines, which limits aquaculture to ca. 600 ha, results in unprofitability. Further, sensitivity analyses place profitability as mainly dependent on DDGS prices and on the daily growth rate (biomass yield) of the macroalga. These two are key factors to achieve profitability at the 600-ha scenario.

The sun is the only source of renewable energy available to us, if geothermal energy is not taken into account. In the form of radiation (UV light, visible light, infrared light, Section 1.1) it sends us annually 178,000 terawatts (1 TW = 10¹² W; unit of power 1 W = 1 J s^–1 = 859.85 calories per hour), that is to say 15,000 times the energy consumed annually by humanity. Only 0.1% of the solar energy received by planet Earth is converted into plant biomass, i.e. 100 × 10⁹ tons per year which corresponds to ca. 180 × 10⁹ tons per year of CO₂ captured from the atmosphere. This CO₂ returns to the biosphere after the death of the plants. Consumption of fossil carbon emits ca. 35 × 10⁹ tons of CO₂ yearly. Biomass is the material produced by all living organisms (plants, animals, microorganisms, fungi)…

Extracts from auto- and acid-hydrolysis of Eucalyptus globulus wood chips were used as fermentation media to produce ethanol by the yeast Pichia stipitis. pH adjustment with Ca(OH)₂ led to higher yeast activity than with NaOH, probably due to a detoxification effect. Furfural, in the range 0.1 to 0.8 g L^-1, did not act as an inhibitor of yeast growth. Substrate inhibition did not occur as well for xylose concentration as high as 60 g L^-1. Autohydrolysis extracts were submitted to a secondary hydrolysis. The use of different contents of auto- and acid-hydrolysis extracts as natural media, with the yeast previously adapted, showed that 75% (v/v) of acid-hydrolysis extract neutralized with Ca(OH)₂, led to 10 g L^-1 ethanol concentration and a yield of 0.36 g_bioethanolg_sugars^-1, under micro-aerobic conditions, at 30 °C and pH 6.0. Although the maximum ethanol concentration reached was still very low, these results compare well to those obtained when using a synthetic medium with an equivalent concentration of xylose.

Reduction of greenhouse gas emissions (GHG) in the automobile sector is one of the main reasons supporting bioethanol production. Bioethanol obtained from biomass fermentation is dilute and unsuitable for use as an automobile fuel. For recovery (pre-concentration) and dehydration (purification) of bioethanol from the fermentation broth, distillation is widely used although ethanol and water separation by distillation is complex due to the presence of a minimum-boiling azeotrope. Membrane separation is increasingly promising for use in bioethanol production. Hence, this chapter presents development of a hybrid process of distillation followed by vapor permeation (DVP) to produce fuel-grade (99.8 wt.%) ethanol. Process optimization with one objective can reduce energy consumption. For deeper insights and meaningful conclusions, this study investigates multi-objective optimization of DVP process for bioethanol recovery and dehydration, using multi-objective differential evolution. Pareto-optimal solutions for minimizing GHG and cost of manufacture are presented and discussed. DVP process at 134 kPa has a lower cost of manufacture of $0.1829/kg of bioethanol with 99.8% recovery of bioethanol from the fermentation broth.