• Energy Research

During recent years, a renovated interest in the pre-treatment of biomass through torrefaction has led to several proposals on industrial-scale application of the technology. Torrefaction holds promising characteristics for obtaining a high-energy yield biomass for further processing, including densified biofuels such as pellets and briquettes, at low overall costs, low energy input, and high capacity and availability for the near future, having the capability of displacing coal in power facilities. Despite many efforts in developing the technology at an industrial scale, very few manufacturers and companies are offering torrefied machinery and lignocellulosic torrefied biomass. Furthermore, information about the actual profitability of the business, sensitivity, and costs of torrefied biomass are very scarce and are limited to very focused studies in some areas of the production, but not in the overall supply chain, and manufacturing processes. This study aimed to develop and validate a technical and economic model for the production of lignocellulosic torrefied biomass for its utilization in the solid biofuels industry, with a focus on production and delivered costs for U.S. potential manufacturers. This model also includes analysis of important variables affecting production, such as biomass delivered costs, capital expenditure (CAPEX), and technology availability. Results indicate that the production of torrefied lignocellulosic biomass can be profitable for U.S. manufacturers, subject to a high sensitivity on biomass cost, CAPEX, and technology affordability for large-scale production. Other sensitive facts include carbon credits scenarios, which may influence profitability based on analyses of net present value and internal rate of return for the manufacturing facility.

Abstract The technical and financial performance of high yield Eucalyptus biomass in a co-current dilute acid pretreatment followed by enzymatic hydrolysis process was simulated using WinGEMS ® and Excel ® . Average ethanol yield per dry Mg of Eucalyptus biomass was approximately 347.6 L of ethanol (with average carbohydrate content in the biomass around 66.1%) at a cost of $0.49 L −1 of ethanol, cash cost of ∼ $0.46 L −1 and CAPEX of $1.03 L −1 of ethanol. The main cost drivers are: biomass, enzyme, tax, fuel (gasoline), depreciation and labor. Profitability of the process is very sensitive to biomass cost, carbohydrate content (%) in biomass and enzyme cost. Biomass delivered cost was simulated and financially evaluated in Part I; here in Part II the conversion of this raw material into cellulosic ethanol using the dilute acid process is evaluated.

Abstract Manufacturing and trade of wood pellets in the United States (US) has seen an exponential growth in the last few years, triggered by its potential utilization in applications typically dominated by fossil fuels, such as heat, power, and combined cycle generation. This combination holds the promise of delivering a high density, high heat value fuel, making it a better substitute for coal and other fossil fuels. This combined process exists only at pilot-plant levels. Scale-up of the technology and feasibility of such projects remain largely unexplored. This research developed a techno-economic model for the production of torrefied wood pellets, considering critical production parameters, and evaluating sensitivity to changes in CAPEX (Capital Expenditure), biomass delivered costs, labor, and energy consumption of a facility, evaluated through a case-study. Results indicated that biomass delivered costs and depreciation are the most significant factors influencing production with CAPEX being the most sensitive variable due to high investments in torrefaction reactors. The selection of different torrefaction technologies, and adequate binders, may represent a major improvement in the feasibility of a project by reducing capital costs drastically. Back-calculated price for torrefied wood pellets is $261/metric ton (100,000 metric tons/year facility), and delivered price may reach $282/metric ton, a similar cost compared to regular pellets. Preliminary analysis of carbon credits as additional income may considerably increase the likeability of the business, and further enhance profitability.

The ability of microemulsions to overcome the complex capillary structure of wood is revealed in relation to its composition and formulation. The oil phase (limonene in this study) of O/W microemulsions is found to be critical for effective flooding. The type of amphiphile molecule used, including sodium lignosulfonate and alkyl polyglucosides as well as reference sodium dodecylsulfate and silicone-based surfactants, together with the viscosity of the resulting microemulsions were the main factors determining the dynamics and extent of fluid penetration. The associated observations were ascribed to the balance of the affinities of the surfactants for the substrate and its conductive elements. Owing to the inherent morphological and chemical features, large differences were observed as far as impregnation susceptibility of different wood types is concerned. By using appropriate surfactant mixtures it was possible for the microemulsions to penetrate the most recalcitrant woody biomass studied, with efficiencies up to 83% higher than that of water, at atmospheric pressure and room temperature. Application of microemulsions is a new alternative for green and efficient pre-treatment of woody biomass in biorefineries, to deliver (bio)chemical functions to the constrained spaces of the cell wall and to increase its accessibility.

This study aimed to assess the energy performance of three different charcoal production systems: “encosta” kiln, “rectangular” kiln, and “fornalha” kiln. Data collection involved measuring carbonization product yields and essential process variables, enabling determination of material and energy flows, and evaluation of two main energy indicators: the EROI and the energy balance. The study found that all evaluated systems had a negative energy balance, indicating inefficiency. The encosta kiln system displayed the best energy performance with the highest EROI (0.90 ± 0.45) and the greatest energy intensity (264.50 MJ t−1 ± 132.25), despite having faced technological, operational, and mechanization limitations that explained its limited use on a global scale. Research that evaluates the sustainable production of charcoal has grown in recent years, however, and it is necessary to invest in studies that evaluate the existing energy flow. Thus, the energy performance indicators presented in this study offer valuable insights for decision-making in charcoal production, potentially maximizing efficiency of the systems. Optimizing carbonization system energy performance can be achieved by implementing operational parameters focused on reducing avoidable energy losses, such as improving thermal insulation and introducing systems for heat recovery or combustion gas utilization.

AbstractThe growing interest in bamboo fibers for pulp, paper, and board production in the USA necessitates a comprehensive financial viability assessment. This study conducts a detailed technoeconomic analysis (TEA) of bamboo fiber production, primarily for the consumer hygiene tissue market although it is also applicable to other industrial uses. The economic viability of two pulping methods – alkaline peroxide mechanical pulping (APMP) and ammonium bisulfite chemical pulping (ABS) – was explored within three different pulp mill settings to supply pulp to two nonintegrated tissue and towel mills in South Carolina, USA. The target was to produce wet lap bamboo bleached pulp at 50% consistency and 70% ISO brightness. Despite higher initial capital invesment and operating costs, ABS achieved a lower minimum required selling price – USD 544 to 686 per bone dry metric ton (BDt = 1000 BDkg) – in comparison with USD 766 to 899 BDt−1 for APMP. This price advantage is partly due to an additional revenue stream (lignosulfonate byproduct), which not only boosts revenue but also circumvents the need for expensive chemical recovery systems. When compared with traditional kraft pulping, both methods require significantly lower capital investments, with minimum required selling prices (estimated to achieve 16% IRR) below current market rates for extensively used bleached kraft pulps in the USA tissue industry. The economic benefits derive from several factors: the low cost of bamboo as raw material, reduced capital needs for new pulping technologies, lower transportation costs from the pulp mill to tissue and towel manufacturing facilities, and the high market price of bleached kraft pulp.

The use of biomass as a source of bioenergy has intensified in recent years and has gained strength in replacing fossil fuels and their derivatives. Jatropha curcas L. oil is currently used as a raw material for the production of biodiesel through the physical extraction of the fruit, generating a large amount of waste. The heterogeneity characteristics of these materials impose the need for thermal pre-treatments for their recovery, such as torrefaction. Thus, this study aimed to investigate the biomass of Jatropha curcas as affected by water availability and its response to the torrefaction process. This research analyzed the biomass physical, chemical, and energy characteristics. TGA/DTG evaluated the thermo-degradation profile, and infrared spectroscopy (FTIR) determined the aromatic chemical structure. The fresh biomass of epicarp and cake presented different behaviors regarding water availability conditions, as variations in lignin contents from 29% to 2.7% and 30.9%–5.7%, respectively, and extractive range from 45.3% to 19.8% and 44.6%–21.6%, respectively. Torrefaction contributed to the increase in physical-chemical characteristics such as lignin and fixed carbon levels, from 29% to 82.4% and 19.8%–52.7%, respectively, and net calorific value of biomass, valuing them for energy use, as well as to decrease in the content of volatile materials from 80.7% to 71.8%. Using renewable biomass of Jatropha curcas cake and epicarp for energy purposes contributes to the reduction of environmental impacts by reducing the disposal of these residues in the environment, providing a sustainable and more efficient destination.

Abstract Eucalyptus plantations in the Southern United States offer a viable feedstock for renewable bioenergy. Delivered cost of eucalypt biomass to a bioenergy facility was simulated in order to understand how key variables affect biomass delivered cost. Three production rates (16.8, 22.4 and 28.0 Mg ha −1 y −1 , dry weight basis) in two investment scenarios were compared in terms of financial analysis, to evaluate the effect of productivity and land investment on the financial indicators of the project. Delivered cost of biomass was simulated to range from $55.1 to $66.1 per delivered Mg (with freight distance of 48.3 km from plantation to biorefinery) depending on site productivity (without considering land investment) at 6% IRR. When land investment was included in the analysis, delivered biomass cost increased to range from $65.0 to $79.4 per delivered Mg depending on site productivity at 6% IRR. Conversion into cellulosic ethanol might be promising with biomass delivered cost lower than $66 Mg −1 . These delivered costs and investment analysis show that Eucalyptus plantations are a potential biomass source for bioenergy production for Southern U.S.

AbstractBamboo, recognized for its rapid growth, high yield, and fiber performance is prominent in the fiber‐based bioproduct industry. However, the absence of US industrial bamboo plantations for fiber production necessitates reliance on imports or locally manufactured products using imported bamboo fibers, predominantly from China. This study evaluates the economic viability of cultivating bamboo in the Southern US for fiber production, with a case study on hygiene tissue products. The supply‐chain analysis was assessed to calculate bamboo chips' minimum selling price (MSP) at the farm gate for an 8% internal rate of return (IRR). The MSP, influenced primarily by land rental costs, ranges from USD 48 to 55 per bone‐dry metric ton (BDt). Despite an initial establishment cost of ~USD 2 000 ha−1 and profitability by year 5, bamboo is a viable, long‐term fiber alternative. Successful bamboo cultivation in the US could lead to a more sustainable implementation of alternative non‐wood fibers for hygiene tissue applications.