The Impact of Biomass Availability and Processing Cost on Optimum Size and Processing Technology Selection

Biomass processing plants have a trade-off between two competing cost factors: as size increases, the economy of scale reduces per unit processing cost, while a longer biomass transportation distance increases the delivered cost of biomass. The competition between these cost factors leads to an optimum size at which the cost of energy produced from biomass is minimized. Four processing options are evaluated: power production via direct combustion and via biomass integrated gasification and combined cycle (BIGCC), ethanol production via fermentation, and syndiesel via Fischer Tropsch. The optimum size is calculated as a function of biomass gross yield (the biomass available to the processing plant from the total surrounding area) and processing cost (capital recovery and operating costs). Higher biomass gross yield and higher processing cost each lead to a higher optimum size. For most cases, a small relaxation in the objective of minimum cost, 3%, leads to a halving of plant size. Direct combustion and BIGCC each produce power, with BIGCC having a higher capital cost and conversion efficiency. When the delivered cost of biomass is high, BIGCC produces power at a lower cost than direct combustion. The crossover point at which this occurs is calculated as a function of the purchase cost of biomass and the biomass gross yield.     

The relative cost of biomass energy transport

Logistics cost, the cost of moving feedstock or products, is a key component of the overall cost of recovering energy from biomass. In this study, we calculate for small- and large-project sizes, the relative cost of transportation by truck, rail, ship, and pipeline for three biomass feedstocks, by truck and pipeline for ethanol, and by transmission line for electrical power. Distance fixed costs (loading and unloading) and distance variable costs (transport, including power losses during transmission), are calculated for each biomass type and mode of transportation. Costs are normalized to a common basis of a giga Joules of biomass. The relative cost of moving products vs feedstock is an approximate measure of the incentive for location of biomass processing at the source of biomass, rather than at the point of ultimate consumption of produced energy. In general, the cost of transporting biomass is more than the cost of transporting its energy products. The gap in cost for transporting biomass vs power is significantly higher than the incremental cost of building and operating a power plant remote from a transmission grid. The cost of power transmission and ethanol transport by pipeline is highly dependent on scale of project. Transport of ethanol by truck has a lower cost than by pipeline up to capacities of 1800 t/d. The high cost of transshipment to a ship precludes shipping from being an economical mode of transport for distances less than 800 km (woodchips) and 1500 km (baled agricultural residues).     

Laboratory cost management.

Laboratory cost management deals with the economical use of laboratory resources such as capital, equipment and manpower. Cost analysis is a tool for cost management, by means of which the laboratory manager can properly set priorities, choose appropriate test procedures, set personnel policies and make better investments of his resources. This article sets out some important aspects of cost analysis, such as the construction of cost curves, the factors that enter into cost analysis, the context in which cost analysis is used, and the limitations of this type of analysis.     

Economic evaluation of the hydrolysis of lactose using immobilized β-galactosidase

A computer program for preliminary cost estimates of free and immobilized enzyme systems has been developed. The cost for the hydrolysis of lactose by β-galactosidase fromAspergillus oryzae has been calculated for a batch tank reactor, with free (BTRF) and immobilized (BTRI) enzymes, a continuously stirred tank reactor (CSTR) and a plug-flow tubular reactor (PFTR), considering the mass transfer behavior and deactivation of the enzyme.

Enzyme immobilization is economically feasible, compared with a system with free enzymes, despite a very high cost for the enzyme attachment. At a half-life time of 80 d, the PFTR gives the lowest cost (0.48 SEK/kg lactose), but the cost for the BTRI is just slightly higher (0.66 SEK/kg lactose) and still much lower than the BTRF (2.10 SEK/kg lactose).

     

Preliminary estimate of the cost of ethanol production for ssf technology

The Solar Energy Research Institute (SERI) recently completed a detailed engineering and economic analysis of the simultaneous saccharification and fermentation (SSF) based wood-to-ethanol process. The reference-case design was based on a plant capacity of 1920 dry t/d and a wood cost of $42/dry t. For this case, the preliminary estimate of the production cost of the ethanol product is about $1.22/gal. The combined effects of optimizing SSF enzyme loading, increasing plant capacity to 10,000 dry t/d, and reducing wood cost to $34/dry t are to reduce the preliminary estimate of the production cost to about $0.95/gal. Other technological improvements may further reduce the production cost. Certain technical assumptions, inherent in the analysis, are being investigated further.

     

Development of Activity-based Cost Functions for Cellulase, Invertase, and Other Enzymes

As enzyme chemistry plays an increasingly important role in the chemical industry, cost analysis of these enzymes becomes a necessity. In this paper, we examine the aspects that affect the cost of enzymes based upon enzyme activity. The basis for this study stems from a previously developed objective function that quantifies the tradeoffs in enzyme purification via the foam fractionation process (Cherry et al., Braz J Chem Eng 17:233–238, 2000). A generalized cost function is developed from our results that could be used to aid in both industrial and lab scale chemical processing. The generalized cost function shows several nonobvious results that could lead to significant savings. Additionally, the parameters involved in the operation and scaling up of enzyme processing could be optimized to minimize costs. We show that there are typically three regimes in the enzyme cost analysis function: the low activity prelinear region, the moderate activity linear region, and high activity power-law region. The overall form of the cost analysis function appears to robustly fit the power law form.     

Potential Enzyme Cost Reduction with the Addition of Surfactant during the Hydrolysis of Pretreated Softwood

The potential economic benefits of surfactants addition on enzymatic hydrolysis of steam-exploded lodgepole pine (SELP) and ethanol-pretreated lodgepole pine (EPLP) were investigated in this study. Free cellulase readsorption on fresh substrate was used to recover and recycle cellulase enzymes during the hydrolysis of SELP and EPLP substrate. Supplementing Tween 80 during the hydrolysis could facilitate enzyme recycling for EPLP substrate. A logarithmic correlation was established between surfactant concentration and free cellulase content after lignocellulosic hydrolysis, which was used to compute enzyme cost savings over various Tween 80 concentrations. A simple economic analysis of enzyme cost savings versus the cost of surfactant was undertaken. The results indicated that the addition of Tween 80 (priced at US $0.25/kg) during the hydrolysis of the EPLP substrate could save 60% of the total enzyme cost at concentrations in the 0.025% to 0.2% range. The addition of Tween for the hydrolysis of the SELP substrate significantly reduced the material cost by 24% per 1 gal of ethanol produced, and the ethanol production cost could be reduced by 8.6% with the addition of Tween and enzymes recycle for the hydrolysis of SELP substrate. A schematic concept of recycling enzyme and surfactant was also presented with a recirculation of process streams during hydrolysis. Further analysis indicated a 66% reduction in total enzyme cost could potentially be achieved under the concept.     

Optimal current and voltage trajectories for minimum energy consumption in batch electrodialysis

Cost-effective operations of a batch electrodialyzer for removal of salt from a single salt solution are investigated. It is desired to minimize the operating cost for a particular batch. The operating cost for an electrodialysis (ED) stack is comprised of cost related to energy consumption and cost of maintenance of the ED stack. In effective operations of an ED stack, the maintenance cost is a small fraction of the total operating cost. The bulk of the operating cost is therefore proportional to total energy consumption, which is the sum of the electrical energy needed for salt removal and the energy required to pump various solutions through the ED stack. For fixed feed composition and the desired percent salt recovery, the total energy required is influenced by trajectories of current flowing through and the voltage applied across the ED stack and the operating time. In this regard, the following operations are studied: (I) constant current operation, (II) constant voltage operation, (III) constant current operation followed by constant voltage operation, (IV) constant voltage operation followed by constant current operation, and (V) operation with time-variant current and voltage. For arbitrary relations among salt concentration, current utilization, and stack resistance, optimal current and voltage trajectories that lead to minimum energy requirement are identified for each of the five operations. It is established analytically that operation V is superior to operations III and IV, which in turn are superior to operations I and II. Numerical illustrations reveal that the performance differences in these operations are enhanced as the percent salt recovery is increased.     

Polyolefin: changing supply-demand framework and new technology

Polyolefin industry is now under a remarkable change of international supply-demand framework and its market is splitting into commodity and high performance products. It is getting more important for a material being harmless and comfortable, while the “life cycle cost”, which includes the cost during use and the recycle cost after use, is regarded as more important to evaluate a material. Those changes are accelerating the inter-material penetration. Several examples of the material design and production technologies, which responded to the changing market needs and developed new applications of polyolefin, are discussed.     

Exergoeconomic analysis of a thermochemical copper–chlorine cycle for hydrogen production using specific exergy cost (SPECO) method

The manner is investigated in which exergy-related parameters can be used to minimize the cost of a copper–chlorine (Cu–Cl) thermochemical cycle for hydrogen production. The iterative optimization technique presented requires a minimum of available data and provides effective assistance in optimizing thermal systems, particularly in dealing with complex systems and/or cases where conventional optimization techniques cannot be applied. The principles of thermoeconomics, as embodied in the specific exergy cost (SPECO) method, are used here to determine changes in the design parameters of the cycle that improve the cost effectiveness of the overall system. The methodology provides a reasonable approach for improving the cost effectiveness of the Cu–Cl cycle, despite the fact that it is still in development. It is found that the cost rate of exergy destruction varies between $1 and $15 per kilogram of hydrogen and the exergoeconomic factor between 0.5 and 0.02 as the cost of hydrogen rises from $20 to $140 per GJ of hydrogen energy. The hydrogen cost is inversely related to the exergoeconomic factor, plant capacity and exergy efficiency. The results are expected to assist ongoing efforts to increase the economic viability and to reduce product costs of potential commercial versions of this process. The impact of the results are anticipated to be significant since thermochemical water splitting with a copper–chlorine cycle is a promising process that could be linked with nuclear reactors to produce hydrogen with no greenhouse gases emissions, and thereby help mitigate numerous energy and environment concerns.     

Changes in motion vs. bonding in positively vs. negatively cooperative interactions

From a consideration of the interactions between non-covalent bonds, it is concluded that positively cooperative binding will occur with a benefit in enthalpy and a cost in entropy, and that negatively cooperative binding will occur with a cost in enthalpy and a benefit in entropy; experimental data support these conclusions.     

A comparative study of global hexavalent chromium removal by chemical and electrochemical processes

Direct electroreduction of Cr(VI) to Cr(III) has been widely proposed as an alternative for the treatment of effluents polluted with hexavalent chromium, however, no analysis is available on the cost of a global process, that considers both, the energy required to carry out the reduction reaction, and that associated with the operation of the process, to remove Cr(VI) via precipitation of Cr(OH)₃. This paper presents a study of the operation cost, considering raw material and electric power required by the electrochemical process, to remove Cr(VI) from real samples. A comparison between chemical reduction is presented, where both processes are followed by a step of alkaline chemical precipitation. The differences in pH required for each step are determinant in the overall cost of the process. Operating under optimal conditions the cost is almost 7 times higher for direct electroreduction process compared with the chemical method, and power consumption being secondary. The ratio decreases to 1.3 times when the electrochemical method is carried out at pH 2, but operating time is increased threefold, thereby increasing the cost of pumping the solution to be treated.     

Optimization of module configuration in membrane gas separation

Mathematical models have been developed to optimize three configurations for membrane gas separation modules. The three systems include the single stage, the two stage, and the continuous membrane column (CMC). Analysis of the three systems is carried out for the case of enriching a binary mixture of methane and carbon dioxide, where the reject stream is the desired product. The cost optimization function includes the capital cost for compressors and membranes as well as the energy operating cost. The cost function is solved subject to a set of equality and inequality constraints. The equality constraints include the module balance equations and the permeation fluxes across the membrane. The inequality equations include constraints on mole fractions in permeate and reject streams, operating pressure, membrane area, and the amount of methane recovered in reject stream. Model equations for the three systems are solved using GINO, a program for nonlinear optimization. A quasi-Newton search method is selected and found quite efficient for solution of the equations. Over the range of parameters considered in the analysis, results show that the two stage configuration has a lower production cost than the other two systems. In addition, the operating cost for the CMC and the single stage systems are found to be comparable. Irrespective of this, the optimum amount of methane recovered is the highest for the CMC system. Although the optimum operating costs for the CMC and the single stage systems are higher than the two stage system, comparison should consider other factors including higher methane recoveries generated by the CMC system and the simplicity of design and operation for the single stage system.     

A Low‐Cost Neutral Zinc–Iron Flow Battery with High Energy Density for Stationary Energy Storage

Flow batteries (FBs) are one of the most promising stationary energy‐storage devices for storing renewable energy. However, commercial progress of FBs is limited by their high cost and low energy density. A neutral zinc–iron FB with very low cost and high energy density is presented. By using highly soluble FeCl₂/ZnBr₂ species, a charge energy density of 56.30 Wh L⁻¹ can be achieved. DFT calculations demonstrated that glycine can combine with iron to suppress hydrolysis and crossover of Fe³⁺/Fe²⁺. The results indicated that an energy efficiency of 86.66 % can be obtained at 40 mA cm⁻² and the battery can run stably for more than 100 cycles. Furthermore, a low‐cost porous membrane was employed to lower the capital cost to less than $ 50 per kWh, which was the lowest value that has ever been reported. Combining the features of low cost, high energy density and high energy efficiency, the neutral zinc–iron FB is a promising candidate for stationary energy‐storage applications.     

A partial-propensity formulation of the stochastic simulation algorithm for chemical reaction networks with delays

Several real-world systems, such as gene expression networks in biological cells, contain coupled chemical reactions with a time delay between reaction initiation and completion. The non-Markovian kinetics of such reaction networks can be exactly simulated using the delay stochastic simulation algorithm (dSSA). The computational cost of dSSA scales with the total number of reactions in the network. We reduce this cost to scale at most with the smaller number of species by using the concept of partial reaction propensities. The resulting delay partial-propensity direct method (dPDM) is an exact dSSA formulation for well-stirred systems of coupled chemical reactions with delays. We detail dPDM and present a theoretical analysis of its computational cost. Furthermore, we demonstrate the implications of the theoretical cost analysis in two prototypical benchmark applications. The dPDM formulation is shown to be particularly efficient for strongly coupled reaction networks, where the number of reactions is much larger than the number of species.     

Sustainable Electrical Energy Storage through the Ferrocene/Ferrocenium Redox Reaction in Aprotic Electrolyte

The large‐scale, cost‐effective storage of electrical energy obtained from the growing deployment of wind and solar power is critically needed for the integration into the grid of these renewable energy sources. Rechargeable batteries having a redox‐flow cathode represent a viable solution for either a Li‐ion or a Na‐ion battery provided a suitable low‐cost redox molecule soluble in an aprotic electrolyte can be identified that is stable for repeated cycling and does not cross the separator membrane to the anode. Here we demonstrate an environmentally friendly, low‐cost ferrocene/ferrocenium molecular redox couple that shows about 95 % energy efficiency and about 90 % capacity retention after 250 full charge/discharge cycles.     

Effect of reduction in yeast and enzyme concentrations in a simultaneous-saccharification-and-fermentation-based bioethanol process

The ethanol production cost in a simultaneous saccharification and fermentation-based bioethanol process is influenced by the requirements for yeast production and for enzymes. The main objective of this study was to evaluate—technically and economically—the influence of these two factors on the production cost. A base case with 5 g/L of baker’s yeast and an initial concentration of water-insoluble solids of 5% resulted in an experimental yield of 85%. When these data were implemented in Aspen Plus, yeast was assumed to be produced from sugars in the hydrolysate, reducing the overall ethanol yield to 69%. The ethanol production cost was 4.80 SEK/L (2.34 US$/gal). When adapted yeast was used at 2 g/L, an experimental yield of 74% was achieved and the estimated ethanol production cost was the same as in the base case. A 50% reduction in enzyme addition resulted in an increased production cost, to 5.06 SEK/L (2.47 US$/gal) owing to reduced ethanol yield.     

Scale-up of Thermally Dried Kefir Production as Starter Culture for Hard-Type Cheese Making: An Economic Evaluation

This paper concerns the effect of thermal-drying methodology on the investment cost for dried kefir cells production in order to be used as starter culture in cheese manufacturing. Kefir cells were produced at pilot plant scale using a 250-L bioreactor and whey as the main substrate. Kefir cells were subsequently dried in a thermal dryer at 38?°C and used as a starter culture in industrial-scale production of hard-type cheeses. The use of thermally dried kefir as starter culture accelerated ripening of cheeses by increasing both lipolysis and fermentation rate as indicated by the ethanol, lactic acid, and glycerol formation. Additionally, it reduced coliforms and enterobacteria as ripening proceeded. This constituted the basis of developing an economic study in which industrial-scale production of thermally dried kefir starter culture is discussed. The industrial design involved a three-step process using three bioreactors of 100, 3,000, and 30,000 L for a plant capacity of 300 kg of thermally dried kefir culture per day. The cost of investment was estimated at 238,000 €, which is the 46% of the corresponding cost using freeze-drying methodology. Production cost was estimated at 4.9 €/kg of kefir biomass for a 300-kg/day plant capacity, which is the same as with the corresponding cost of freeze-dried cells. However, the estimated added value is up to 10.8?×?10⁹ € within the European Union.     

Existing biorefinery operations that benefit from fractal-based process intensification

Ion exchange, adsorption, and chromatography are examples of separation processes frequently used in today's biorefineries. The particular tasks for which these technologies can be successfully applied are highly influenced by capital cost and efficiency. There exists a potential for significantly increasing the efficiency of these processes whereas simultaneously decreasing their size and capital cost. This potential for process intensification can be realized with the use of engineered fractal equipment. The cost savings potential and the possibilities for broadening the use of fractal-based separation technologies in future biorefinery concepts is illustrated by examples of full-scale implementation in the sugar and sweetener industries.