Uncertainties and sustainability concepts in biofuel supply chain management: A review

Biofuel energy as an alternative and additive form of energy to fossil fuel has gained much attention in recent times. In order to sustain such a vision, a robust supply chain is of extreme importance in helping to deliver competitive biofuel to the end user markets. In this paper, firstly, an introduction of the evolution of biofuels and the general structure of the biofuel supply chain are presented. Secondly, the three types of decision making levels and uncertainties that are inherent within the biofuel supply chain are discussed. Thirdly, important methodologies for modeling uncertainties in the decision making process are provided. Fourthly, sustainability concepts and models that give perspectives to the social, economical and environmental concepts are reviewed. Finally, conclusions and future research based on incorporating uncertainties and sustainability concepts within the biofuel supply chain are drawn and suggested, respectively.     

降低小型柴油机排放的试验研究

从生物混合燃料成分、燃烧室结构和排气再循环等方面探索降低柴油机排放的方法。通过对柴油机排放性能的大量试验研究,结果表明:对于直喷式柴油机,生物混合燃料的NOx排放与柴油的排放基本相当,碳烟排放则比柴油有较大幅度的降低,而涡流室柴油机,NOx的排放量却有大幅度的降低,碳烟排放则比直喷式柴油机有更大幅度的降低,生物燃料的添加比例对NOx的排放影响不大。柴油机采用排气再循环技术后,混合燃料的碳烟排放仍比柴油少,混合燃料可以承载一定的EGR率而不增加碳烟排放。排气再循环可以大幅度地降低NOx排放且与EGR率有关,与燃料的性质关系不大。涡流室柴油机采用生物燃料和排气再循环,可以同时降低NOx和碳烟的排放,排放效果非常优良。     

A potentially implantable glucose fuel cell with Raney-platinum film electrodes for improved hydrolytic and oxidative stability

We present an improved abiotically catalyzed glucose fuel cell, intended as energy harvesting tissue implantable power supply for medical implants. The fuel cell is constructed from a Raney-platinum film cathode deposited on a silicon substrate with micro-machined feedholes for glucose permeability, arranged in front of a Raney-platinum film anode. A novelty is the application of platinum for both electrodes and the complete abdication of hydrogel binders. This overcomes the limited stability against hydrolytic and oxidative attack encountered with previous glucose fuel cells fabricated from activated carbon particles dispersed in a hydrogel matrix. During performance characterization in phosphate buffered saline under physiological concentrations of glucose and oxygen the diffusion resistance to be expected from tissue capsule formation was taken into account. Despite the resulting limited oxygen supply, the Raney-platinum fuel cells exhibit a power density of up to (4.4 ± 0.2) μW cm⁻² at 7.0% oxygen saturation. This exceeds the performance of our previous carbon-based prototypes, and can be attributed to the higher catalytic activity of platinum cathodes and in particular the increased oxygen tolerance of the Raney-platinum film anodes.     

Economics of small-scale on-farm use of canola and soybean for biodiesel and straight vegetable oil biofuels

While the cost competitiveness of vegetable oil-based biofuels (VOBB) has impeded extensive commercialization on a large-scale, the economic viability of small-scale on-farm production of VOBB is unclear. This study assessed the cost competitiveness of small-scale on-farm production of canola- [Brassica napus (L.)] and soybean-based [Glycine max (L.)] biodiesel and straight vegetable oil (SVO) biofuels in the upper Midwest at 2007 price levels. The effects of feedstock type, feedstock valuation (cost of production or market price), biofuel type, and capitalization level on the cost L⁻¹ of biofuel were examined. Valuing feedstock at the cost of production, the cost of canola-based biodiesel ranged from 0.94 to 1.13 $ L⁻¹ and SVO from 0.64 to 0.83 $ L⁻¹ depending on capitalization level. Comparatively, the cost of soybean-based biodiesel and SVO ranged from 0.40 to 0.60 $ L⁻¹ and from 0.14 to 0.33 $ L⁻¹, respectively, depending on capitalization level. Valuing feedstock at the cost of production, soybean biofuels were cost competitive whereas canola biofuels were not. Valuing feedstock at its market price, canola biofuels were more cost competitive than soybean-based biofuels, though neither were cost competitive with petroleum diesel. Feedstock type proved important in terms of the meal co-product credit, which decreased the cost of biodiesel by 1.39 $ L⁻¹ for soybean and 0.44 $ L⁻¹ for canola. SVO was less costly to produce than biodiesel due to reduced input costs. At a small scale, capital expenditures have a substantial impact on the cost of biofuel, ranging from 0.03 to 0.25 $ L⁻¹.     

Biofuel or excavation? - Life cycle assessment (LCA) of soil remediation options

The environmental consequences of soil remediation through biofuel or through dig-and-dump were compared using life cycle assessment (LCA). Willow (Salix viminalis) was actually grown in-situ on a discontinued oil depot, as a phytoremediation treatment. These data were used for the biofuel remediation, while excavation-and-refill data were estimated from experience. The biofuel remediation had great environmental advantages compared to the ex situ excavation remediation. With the ReCiPe impact assessment method, which included biodiversity, the net environmental effect was even positive, in spite of the fact that the wood harvest was not utilised for biofuel production, but left on the contaminated site. Impact from the Salix viminalis cultivation was mainly through land use for the short rotation coppice, and through journeys of control personnel. The latter may be reduced when familiarity with biofuel as a soil treatment method increases. The excavation-and-refill remediation was dominated by the landfill and the transport of contaminated soil and backfill.     

Enzymatic hydrolysis of cellulose part II: Population balance modelling of hydrolysis by exoglucanase and universal kinetic model

In this work, a concise review on enzymatic hydrolysis of cellulose by endoglucanase is presented. In addition a novel population balance based kinetic model for the action of endoglucanase has been developed. One important feature in the proposed model is a new approach to consider the evolution of cellulose chain length. In addition, a new mechanism for hydrolysis of cellulose by endoglucanase is proposed in which bond breakage is a function of position in the chain as well as the susceptibility to enzymatic attack. In the first part, the focus is on developing a mechanistic model for the action of endoglucanase and then in part II a mechanistic model for the action of exoglucanase has been developed together with a holistic model considering all the major steps involved in enzymatic hydrolysis. In the case of endoglucanase action, the model prediction is very close to the experimental results presented by Kurakake et al. [12]. Using the estimated values for the parameters (confidence interval = 98%), the evolution of size distribution for cellulose polymers during the course of hydrolysis has been presented.     

Characterisation of land types and agro-ecological conditions for production of Jatropha as a feedstock for biofuels in Zimbabwe

There is increasing interest in Zimbabwe in developing a biofuels industry based on the production of biodiesel using Jatropha as the main feedstock. This has led to the introduction of Jatropha as a commercial energy crop in the country. There are plans to grow 1220 km² of Jatropha which will supply about 365,000 t of seed. This will provide about 110 dam³ of biodiesel required to achieve a blending level of 10% with petro-diesel. The availability and suitability of land for the production of Jatropha cannot be taken for granted, particularly given the fact that the concept and practice of production of feedstocks for biofuels remain contested on the threat they pose to food security. Determining the land that is potentially available for biofuels is a non-trivial task. A multiplicity of factors needs to be considered. It is important to determine the spatial extent of areas with suitable growth conditions for Jatropha. The interaction of soil type and land use is an important interface in agriculture. Added to this is the need to balance food, fodder and fuel supply in land use planning. This paper attempts to assess the availability and suitability of various land types as well as agro-ecological conditions for the production of Jatropha in Zimbabwe.     

Flocculation of wall-deficient cells of Chlamydomonas reinhardtii mutant cw15 by calcium and methanol

Flocculation is a common and inexpensive method for harvesting algae from solution. After nitrogen starvation, it was shown that 83 ± 3% of the wall-deficient cells of the cw 15 mutant of Chlamydomonas reinhardtii flocculated from 12 mL samples within 15 min after the addition of 15 mM calcium chloride at pH 8.4. Only 24 ± 2% of the wildtype strain flocculated under these conditions, thus demonstrating how a simple mutation might facilitate process design. The data suggested that algae grown in waters with similar calcium concentrations (e.g. certain wastewaters) might be harvested through simple pH adjustment. It was also discovered that the addition of small amounts (<5% v/v) of methanol could significantly reduce the calcium needed to achieve flocculation. Within 15 min after addition of 12 mM calcium chloride and 4.6% (v/v) methanol, 83 ± 4% of cw15 cells flocculated. Methanol is fully recoverable by distillation, and its use might enable flocculation without further water salinization when media calcium concentrations fall short of 15 mM. It was further shown that substrates for and/or products of cellular growth affected flocculation adversely. Nearly 81% of cells flocculated from fresh medium compared to only 54% in spent medium.     

Dispersion and flow properties of charcoal oil slurries (ChOS) as potential renewable industrial liquid fuels

This work reports on a preliminary study aimed at developing an industrial liquid fuel derived from charcoal and vegetable oil. Its relevance relies on the high energy potential of charcoal, its renewable nature, storage and transportation capacity in liquid form, as well as on the economic and environmental advantages derived thereof. The ability of a commercially available charcoal to be dispersed in three different organic solvents was assessed through the rheological characterisation of the resulting charcoal oil slurries (ChOS). The charcoal was ground in a conventional ball mill and dispersed with the aid of three different surfactants. The effects of the most relevant factors influencing the rheological properties of the suspensions were evaluated, including: (i) the solvent producing the lowest fuel viscosity (η) at a given charcoal content; (ii) the most efficient surfactant (and its amount) minimising the fuel viscosity (η) at a given solids fraction; and (iii) the charcoal content, which should be as high as possible. High-stability ChOS containing 62 wt% solids and 0.4 wt% surfactant, and exhibiting adequate flow properties and high calorific values, were successfully obtained.     

Biofuel excision and the viability of ethanol production in the Green Triangle,Australia

The promotion and use of renewable energy sources are established priorities worldwide as a way to reduce emissions of Greenhouse Gases and promote energy security. Australia is committed to reach a target of 350 ML of biofuels per year by 2010, and incentives targeted to producers and consumers have been placed. These incentives include zero excise until 2011 for the ethanol produced in Australia and gradual increase of the taxation rates reaching the full excise of 0.125 AUD per litre by 2015. This paper analyses the viability of the second generation ethanol industry in the Green Triangle, one of the most promising Australian regions for biomass production, by comparing the energy adjusted pump prices of petrol and the produced ethanol under different taxation rates and forecasted oil prices. Major findings suggest that under the current conditions of zero fuel excise and oil prices around 80US$ per barrel ethanol production is viable using biomass with a plant gate cost of up to 74 AUD per ton. Moreover, the forecasted increase in oil prices have a higher impact on the price of petrol than the increased ethanol excise on the pump price of the biofuel. Thus, by 2016 feedstock with a plant gate cost of up to 190 AUD per ton might be used for ethanol production, representing a flow of 1.7 million tons of biomass per year potentially mitigating 1.2 million tons of CO₂ by replacing fossil fuels with ethanol.