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Showing papers in "Biomass & Bioenergy in 2006"


Journal ArticleDOI
TL;DR: In this paper, the asymptotic modulus of wheat straw, barley straw, corn stover, switchgrass, and switchgrass were determined at different compressive forces, particle sizes and moisture contents.
Abstract: Mechanical properties of wheat straw, barley straw, corn stover and switchgrass were determined at different compressive forces, particle sizes and moisture contents. Ground biomass samples were compressed with five levels of compressive forces (1000, 2000, 3000, 4000 and 4400 N) and three levels of particle sizes (3.2, 1.6 and 0.8 mm) at two levels of moisture contents (12% and 15% (wet basis)) to establish compression and relaxation data. Compressed sample dimensions and mass were measured to calculate pellet density. Corn stover produced the highest pellet density at low pressure during compression. Compressive force, particle size and moisture content significantly affected the pellet density of barley straw, corn stover and switchgrass. However, different particle sizes of wheat straw did not produce any significant difference on pellet density. The relaxation data were analyzed to determine the asymptotic modulus of biomass pellets. Barley straw had the highest asymptotic modulus among all biomass indicating that pellets made from barley straw were more rigid than those of other pellets. Asymptotic modulus increased linearly with an increase in compressive pressure. A simple linear model was developed to relate asymptotic modulus and maximum compressive pressure.

673 citations


Journal ArticleDOI
TL;DR: In this article, the influence of chemical fuel properties on biomass combustion plants as well as possibilities and recommendations for controlling them are discussed and discussed in detail in terms of potential and possible solutions.
Abstract: The chemical composition of solid biofuels (as defined in [Directive 2000/76/EC of the European Parliament and of the Council on the Incineration of Waste. In: European Commission, editor. Official Journal of the European Communities, vol. L 332; 2000. p. 91–111] and [CEN/TC 335—WG2 N94. Final draft. European Committee for standardization, editor. Solid biofuels—fuel specifications and classes. Brussels, Belgium; 2003.] has manifold effects on their thermal utilisation. C, H and O are the main components of solid biofuels and are of special relevance for the gross calorific value, H in addition also for the net calorific value. The fuel N content is responsible for NOx formation. NOx emissions belong to the main environmental impact factors of solid biofuel combustion. Cl and S are responsible for deposit formation and corrosion and are therefore relevant for a high plant availability. Furthermore, Cl causes HCl as well as PCDD/F and S SOx emissions and both elements are involved in the formation of aerosols (submicron particle emissions). The ash content influences the choice of the appropriate combustion technology and influences deposit formation, fly ash emissions and the logistics concerning ash storage and ash utilisation/disposal. Major ash forming elements (Al, Ca, Fe, K, Mg, Na, P, Si, Ti) are of relevance for the ash melting behaviour, deposit formation and corrosion. In addition, volatile elements such as Na and K are main constituents of aerosols. Volatile minor elements (As, Cd, Hg, Pb, Zn) play a major role in gaseous and especially aerosol emissions as well as in deposit formation, corrosion and ash utilisation/disposal. Either partly or non-volatile minor elements (Ba, Co, Cr, Cu, Mo, Mn, V) are of special relevance for ash utilisation. The present paper discusses the influence of chemical fuel properties on biomass combustion plants as well as possibilities and recommendations for controlling them.

654 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyzed the energy consumption of biogas systems based on 8 different raw materials and found that the most energy-demanding process is the operation of the plant, corresponding to 40% to 80% of the energy input into the systems.
Abstract: Energy balances are analysed from a life-cycle perspective for biogas systems based on 8 different raw materials. The analysis is based on published data and relates to Swedish conditions. The results show that the energy input into biogas systems (i.e. large-scale biogas plants) overall corresponds to 20–40% (on average approximately 30%) of the energy content in the biogas produced. The net energy output turns negative when transport distances exceed approximately 200 km (manure), or up to 700 km (slaughterhouse waste). Large variations exist in energy efficiency among the biogas systems studied. These variations depend both on the properties of the raw materials studied and on the system design and allocation methods chosen. The net energy output from biogas systems based on raw materials that have high water content and low biogas yield (e.g. manure) is relatively low. When energy-demanding handling of the raw materials is required, the energy input increases significantly. For instance, in a ley crop-based biogas system, the ley cropping alone corresponds to approximately 40% of the energy input. Overall, operation of the biogas plant is the most energy-demanding process, corresponding to 40–80% of the energy input into the systems. Thus, the results are substantially affected by the assumptions made about the allocation of a plant's entire energy demand among raw materials, e.g. regarding biogas yield or need of additional water for dilution.

557 citations


Journal ArticleDOI
TL;DR: Alfalfa stems, reed canarygrass, and switchgrass; perennial herbaceous species that have potential as biomass energy crops in temperate regions; were evaluated for their bioconversion potential as energy crops.
Abstract: Alfalfa stems, reed canarygrass, and switchgrass; perennial herbaceous species that have potential as biomass energy crops in temperate regions; were evaluated for their bioconversion potential as energy crops. Each forage species was harvested at two or three maturity stages and analyzed for carbohydrates, lignin, protein, lipid, organic acids, and mineral composition. The biomass samples were also evaluated for sugar yields following pretreatment with dilute sulfuric followed by enzymatic saccharification using a commercial cellulase preparation. Total carbohydrate content of the plants varied from 518 to 655 g kg � 1 dry matter (DM) and cellulose concentration from 209 to 322 g kg � 1 DM. Carbohydrate and lignin contents were lower for samples from early maturity samples compared to samples from late maturity harvests. Several important trends were observed in regards to the efficiency of sugar recovery following treatments with dilute acid and cellulase. First, a significant amount of the available carbohydrates were in the form of soluble sugars and storage carbohydrates (4.3–16.3% wt/wt). Recovery of soluble sugars following dilute acid pretreatment was problematic, especially that of fructose. Fructose was found to be extremely labile to the dilute acid pretreatments. Second, the efficiency at which available glucose was recovered was inversely correlated to maturity and lignin content. However, total glucose yields were higher for the later maturities because of higher cellulose contents compared to the earlier maturity samples. Finally, cell wall polysaccharides, as determined by the widely applied detergent fiber system were found to be inaccurate. The detergent fiber method consistently overestimated cellulose and hemicellulose and underestimated lignin by substantial amounts. Published by Elsevier Ltd.

499 citations


Journal ArticleDOI
TL;DR: The reaction kinetics of acid-catalyzed transesterification of waste frying oil in excess methanol to form fatty acid methyl esters (FAME), for possible use as biodiesel, was studied in this paper.
Abstract: The reaction kinetics of acid-catalyzed transesterification of waste frying oil in excess methanol to form fatty acid methyl esters (FAME), for possible use as biodiesel, was studied. Rate of mixing, feed composition (molar ratio oil:methanol:acid) and temperature were independent variables. There was no significant difference in the yield of FAME when the rate of mixing was in the turbulent range 100 to 600 rpm. The oil:methanol:acid molar ratios and the temperature were the most significant factors affecting the yield of FAME. At 70 °C with oil:methanol:acid molar ratios of 1:245:3.8, and at 80 °C with oil:methanol:acid molar ratios in the range 1:74:1.9–1:245:3.8, the transesterification was essentially a pseudo-first-order reaction as a result of the large excess of methanol which drove the reaction to completion (99±1% at 4 h). In the presence of the large excess of methanol, free fatty acids present in the waste oil were very rapidly converted to methyl esters in the first few minutes under the above conditions. Little or no monoglycerides were detected during the course of the reaction, and diglycerides present in the initial waste oil were rapidly converted to FAME.

431 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe the framework development of a dynamic integrated biomass supply analysis and logistics model (IBSAL) to simulate the collection, storage, and transport operations for supplying agricultural biomass to a biorefinery.
Abstract: This paper describes the framework development of a dynamic integrated biomass supply analysis and logistics model (IBSAL) to simulate the collection, storage, and transport operations for supplying agricultural biomass to a biorefinery. The model consists of time dependent events representing the working rate of equipment and queues representing the capacity of storage structures. The discrete event and queues are inter-connected to represent the entire network of material flow from field to a biorefinery. Weather conditions including rain and snow influence the moisture content and the dry matter loss of biomass through the supply chain and are included in the model. The model is developed using an object oriented high level simulation language EXTEND™. A case of corn stover collection and transport scenario using baling system is described.

382 citations


Journal ArticleDOI
TL;DR: In this article, the potential biomass supply in the 15 EU countries (EU15), 8 new member states and 2 candidate countries (ACC10), plus Belarus and the Ukraine, was analyzed.
Abstract: This paper analyses the potential biomass Supply in the 15 EU countries (EU15), 8 new member states and 2 candidate countries (ACC10), plus Belarus and the Ukraine. The objective of this study is to make a more detailed assessment of the potential in Europe than previously undertaken. For this purpose five scenarios were designed to describe the short-, medium- and long-term potential of biomass for energy. The scenarios are based on assumptions regarding residue harvests, energy-crop yields and Surplus agricultural land. Energy-crop yields are correlated with the national wheat yields, a methodology we have not seen used in biomass assessments before. Our assessments show that under certain restrictions on land availability, the potential supply of biomass energy amounts to up to 11.7 EJy(-1) in the EU15 and 5.5 EJy(-1) in the ACC10. For comparison, the overall energy supply in the EU15 totalled 62.6 EJy(-1) in 2001. Consequently, there are no important resource limitations in meeting the biomass target, 5.6E Jy(-1) in the EU15 by 2010, which was set by the European Commission in the 1997 White paper on renewable energy sources (RES). However, given the slow implementation of the RES policy it is very unlikely that the biomass targets will be met. (C) 2005 Elsevier Ltd. All rights reserved.

356 citations


Journal ArticleDOI
TL;DR: In this article, dilute sulfuric acid was used to depolymerize xylan to xylose with a maximum yield of 80.8% at hydrolysis pressure of 15 bar, 10 min retention time and 0.5% acid concentration.
Abstract: Hydrolysis of rice straw by dilute sulfuric acid at high temperature and pressure was investigated in one and two stages. The hydrolyses were carried out in a 10-l reactor, where the hydrolysis retention time (3–10 min), pressure (10–35 bar) and acid concentration (0–1%) were examined. Optimization of first stage hydrolysis is desirable to achieve the highest yield of the sugars from hemicellulose and also as a pretreatment for enzymatic hydrolysis. The results show the ability of first stage hydrolysis to depolymerize xylan to xylose with a maximum yield of 80.8% at hydrolysis pressure of 15 bar, 10 min retention time and 0.5% acid concentration. However, the yield of glucose from glucan was relatively low in first stage hydrolysis at a maximum of 25.8%. The solid residuals were subjected to further dilute-acid hydrolysis in this study. This second-stage hydrolysis without addition of the acid could not increase the yield of glucose from glucan beyond 26.6%. On the other hand, the best results of the hydrolysis were achieved, when 0.5% sulfuric acid was added prior to each stage in two-stage hydrolysis. The best results of the second stage of the hydrolysis were achieved at the hydrolysis pressure and the retention time of 30 bar and 3 min in the second stage hydrolysis, where a total of 78.9% of xylan and 46.6% of glucan were converted to xylose and glucose, respectively in the two stages. Formation of furfural and HMF were functions of the hydrolysis pressure, acid concentration, and retention time, whereas the concentration of acetic acid was almost constant at pressure of higher than 10 bar and a total retention time of 10 min.

352 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyse fuel-cycle emissions from a life-cycle perspective for different biogas systems based on six different raw materials, including carbon dioxide (CO2), carbon oxide (CO), nitrogen oxides (NOx), sulphur dioxide (SO2), hydrocarbons (HC), methane (CH4), and particles.
Abstract: Fuel-cycle emissions of carbon dioxide (CO2) carbon oxide (CO), nitrogen oxides (NOx), sulphur dioxide (SO2), hydrocarbons (HC), methane (CH4), and particles are analysed from a life-cycle perspective for different biogas systems based oil six different raw materials. The gas is produced in large- or farm-scale biogas plants, and is used in boilers for heat production, in turbines for co-generation of heat and electricity, or as a transportation fuel in light- and heavy-duty vehicles. The analyses refer mainly to Swedish conditions. The levels of fuel-cycle emissions vary greatly among the biogas systems studied, and are significantly affected by the properties of the raw material digested, the energy efficiency of the biogas production, and the status of the end-use technology. For example, fuel-cycle emission may vary by a factor of 3-4, and for certain gases by up to a factor of 11, between two biogas systems that provide an equivalent energy service. Extensive handling of raw materials, e.g. ley cropping or collection of waste-products such as municipal organic waste, is often a significant source of emissions. Emission from the production phase of the biogas exceeds the end-use emissions for several biogas systems and for specific emissions. Uncontrolled losses of methane, e.g. leakages from stored digestates or from biogas upgrading, increase the fuel-cycle emissions of methane considerably. Thus, it is necessary to clearly specify the biogas production system and enduse technology being studied in order to be able to produce reliable and accurate data oil fuel-cycle emission. (c) 2005 Elsevier Ltd. All rights reserved. (Less)

319 citations


Journal ArticleDOI
TL;DR: Research on willow (Salix spp.) as a locally produced, renewable feedstock for bioenergy and bioproducts began in New York in the mid-1980s in response to growing concerns about environmental impacts associated with fossil fuels and declining rural economies as discussed by the authors.
Abstract: Research on willow (Salix spp.) as a locally produced, renewable feedstock for bioenergy and bioproducts began in New York in the mid-1980s in response to growing concerns about environmental impacts associated with fossil fuels and declining rural economies. Simultaneous and integrated activities—including research, large-scale demonstrations, outreach and education, and market development—were initiated in the mid-1990s to facilitate the commercialization of willow biomass crops. Despite technological viability and associated environmental and local economic benefits, the high price of willow biomass relative to coal has been a barrier to wide-scale deployment of this system. The cost of willow biomass is currently $ 3.00 GJ - 1 ( $ 57.30 odt - 1 ) compared to $ 1.40 – 1.90 GJ - 1 for coal. Yield improvements from traditional breeding efforts and increases in harvesting efficiency that are currently being realized promise to reduce the price differential. Recent policy changes at the federal level, including the provision to harvest bioenergy crops from Conservation Reserve Program (CRP) land and a closed-loop biomass tax credit, and state-level initiatives such as Renewable Portfolio Standards (RPS) will help to further reduce the difference and foster markets for willow biomass. Years of work on willow biomass crop research and demonstration projects have increased our understanding of the biology, ecophysiology and management of willow biomass crops. Using an adaptive management model, this information has led to the deployment of willow for other applications such as phytoremediation, living snowfences, and riparian buffers across the northeastern US.

275 citations


Journal ArticleDOI
TL;DR: In this paper, the potential distribution of 26 bioenergy crops in the UK was predicted based on the simple model described by Tuck et al. The model has been applied at a 5 km resolution using the UKCIP02 model for scenarios at Low, Medium-Low, Medium High and High emissions.
Abstract: We have predicted the potential distribution of 26 bioenergy crops in the UK, based on the simple model described by Tuck et al. [1]. The model has been applied at a 5 km resolution using the UKCIP02 model for scenarios at Low, Medium-Low, Medium-High and High emissions. In the analysis of the results the limitations for crop growth are assigned to elevation, temperature, high and low rainfall. Most of the crops currently grown are predicted to remain prevalent in the UK. A number of crops are suitable for introduction to the UK under a changing climate, whereas others retreat to northern parts of the UK. The greatest changes are expected in England. The simplicity of the model means that it has a relatively high uncertainty, with minor modifications to the model leading to quite different results. Nevertheless, it is well suited for identifying areas and crops that are most likely to be affected by the greatest changes. It has been noted that Miscanthus and Short Rotation Coppice (SRC) willow and poplar, which are currently regarded as highly suitable for UK conditions, may be less suited to southern areas in the future, where, for example, kenaf could have a greater potential. Further investigations are required to reduce uncertainty associated with the projections based on this simple model and to make conclusions more firmly.

Journal ArticleDOI
TL;DR: In this article, the development of surface morphology of physically and chemically activated carbons observed via scanning electron microscopy showed that physical activation produced activated carbon with a nodular and pitted surface morphology whereas activated carbon produced through chemical activation had a smooth surface morphology.
Abstract: Biomass waste in the form of biomass flax fibre, produced as a by-product of the textile industry was processed via both physical and chemical activation to produce activated carbons. The surface area of the physically activated carbons were up to 840 m 2 g −1 and the carbons were of mesoporous structure. Chemical activation using zinc chloride produced high surface area activated carbons up to 2400 m 2 g −1 and the pore size distribution was mainly microporous. However, the process conditions of temperature and zinc chloride concentration could be used to manipulate the surface area and porosity of the carbons to produce microporous, mesoporous and mixed microporous/mesoporous activated carbons. The physically activated carbons were found to be a mixture of Type I and Type IV carbons and the chemically activated carbons were found to be mainly Type I carbons. The development of surface morphology of physically and chemically activated carbons observed via scanning electron microscopy showed that physical activation produced activated carbons with a nodular and pitted surface morphology whereas activated carbons produced through chemical activation had a smooth surface morphology. Transmission electron microscopy analysis could identify mesopore structures in the physically activated carbon and microporous structures in the chemically activated carbons.

Journal ArticleDOI
TL;DR: In this paper, simultaneous saccharification and fermentation (SSF) at high dry matter content was applied to corn stover, which resulted in a high ethanol concentration in the fermented slurry, thereby decreasing the energy demand in the subsequent distillation step.
Abstract: Replacing fossil fuels by bio-fuels has many advantages, such as the reduction of CO2-emission to the atmosphere, the possibility for non-oil-producing countries to be self-sufficient in fuel, and increased local job opportunities. Bio-ethanol is such a promising renewable fuel. However, today it is produced from sugar or starch-raw materials that are relatively expensive. To lower the production cost of bio-ethanol the cost of the raw material must be reduced and the production process made more efficient. The production of bio-ethanol from corn stover using simultaneous saccharification and fermentation (SSF) at high dry matter content addresses both issues. Corn stover is an agricultural by-product and thus has a low economic value. SSF at high dry matter content results in a high ethanol concentration in the fermented slurry, thereby decreasing the energy demand in the subsequent distillation step. In this study, SSF was performed on steam-pretreated corn stover at 5, 7.5 and 10% water-insoluble solids (WIS) with 2g/L hexosefermenting Saccharomyces cerevisiae (ordinary compressed baker's yeast). SSF at 10% WIS resulted in an ethanol yield of 74% based on the glucose content in the raw material and an ethanol concentration of 25 g/L. Neither higher yeast concentration (5 g/L) nor yeast cultivated on the liquid after the pretreatment resulted, under these conditions, in a higher overall ethanol yield. (c) 2006 Elsevier Ltd. All rights reserved. (Less)

Journal ArticleDOI
TL;DR: In this paper, an inventory of existing certification systems for sustainable biomass trade was made; second, their structures were analyzed; and third and fourth steps different approaches to formulate standards were described and a list of more than 100 social, economic, ecological, and general criteria was extracted from the reviewed systems.
Abstract: It is expected that international biomass trade will significantly increase in the coming years because of the possibly lower costs of imported biomass, the better supply security through diversification and the support by energy and climate policies of various countries. Concerns about potential negative effects of large-scale biomass production and export, like deforestation or the competition between food and biomass production, have led to the demand for sustainability criteria and certification systems that can control biomass trade. Because neither such criteria and indicator sets nor certification systems for sustainable biomass trade are yet available, the objective of this study is to generate information that can help to develop them. For these purposes, existing certification systems, sets of sustainability criteria or guidelines on environmental or social sound management of resources are analyzed with the purpose to learn about the requirements, contents and organizational set ups of a certification system for sustainable biomass trade. First, an inventory of existing systems was made; second, their structures were analyzed. Key finding from the analysis of internationally applied certification systems was that they are generally led by an international panel that represents all countries and stakeholders involved in the biomass production and trade activities. In third and fourth steps different approaches to formulate standards were described and a list of more than 100 social, economic, ecological and general criteria for sustainable biomass trade was extracted from the reviewed systems. Fifth, methods to formulate indicators, that make sustainability criteria measurable, and verifiers that are used to control the performance of indicators are described. It is recommended to further develop the criteria and indicator (C&I) sets for sustainable biomass trade by involvement of the relevant stakeholders (e.g. biomass producer and consumer) and the analysis of local conditions (e.g. local production potentials and limits, and preferences of local people).

Journal ArticleDOI
TL;DR: In this paper, the authors studied biomass production of two upland and two lowland cultivars under two different managements at eight sites in the upper southeastern USA during 1999-2001 (Sites had been planted in 1992 and continuously managed for biomass production).
Abstract: Limited information is available regarding biomass production potential of long-term (>5- yr-old) switchgrass (Panicum virgatum L) stands Variables of interest in biomass production systems include cultivar selection, site/environment effects, and the impacts of fertility and harvest management on productivity and stand life We studied biomass production of two upland and two lowland cultivars under two different managements at eight sites in the upper southeastern USA during 1999–2001 (Sites had been planted in 1992 and continuously managed for biomass production) Switchgrass plots under lower-input management received 50 kg N ha−1 yr−1 and were harvested once, at the end of the season Plots under higher-input management received 100 kg N ha−1 (in two applications) and were harvested twice, in midsummer and at the end of the season Management effects on yield, N removal, and stand density were evaluated Annual biomass production across years, sites, cultivars, and managements averaged 142 Mg ha−1 Across years and sites, a large (28%) yield response to increased inputs was observed for upland cultivars; but the potential value of higher-input management for lowland cultivars was masked overall by large site×management interactions Nitrogen removal was greater under the higher-input system largely due to greater N concentrations in the midsummer harvests Management recommendations (cultivar, fertilization, and harvest frequency), ideally, should be site and cultivar dependent, given the variable responses reported here

Journal ArticleDOI
TL;DR: The few current commercial applications of SRWC rest on a substantial base of silvicultural and biological knowledge, including clones of Populus and Salix, which became the dominant plantation material because of their inherently rapid growth and ease of propagation by hardwood cuttings.
Abstract: Although its roots are in antiquity, the current concept of short-rotation woody crops (SRWC) for fiber and energy evolved scientifically from pioneering tree breeding work begun in the early 20th century. A natural outgrowth of this work was the culture of fast-growing trees on rotations of 1–15 years. Close-spaced tree culture received further impetus with the introduction of the “silage sycamore” concept in the southeastern US in the mid-1960s and the OPEC oil embargo in 1973, leading to statistically designed trials at numerous locations in North America, Europe, and Scandanavia. Early silvicultural research focused on spacing and species trials, propagation methods, site preparation, weed management, nutrition, growth, and yield. Because these trials were based on small plots, and the importance of pest depredations or site variation were not fully recognized, early biomass yield predictions tended to be overly optimistic. Soon physiologists and ecologists began to unravel the biological characteristics of SRWC plantations and their responses to environment. Knowledge of the influence and diversity of pests—insects, diseases, and animals—provided a necessary reality check. Many hardwood tree species and a few conifers have been evaluated over the years for SRWC in temperate regions of the world. Clones of Populus and Salix, however, became the dominant plantation material because of their inherently rapid growth and ease of propagation by hardwood cuttings. Among conifers, loblolly pine (Pinus taeda) also shows promise. Because genetic variation is readily exploitable in the dominant SRWC taxa, strongly focused breeding programs began to provide highly productive genotypes and seed sources in the last decades of the 20th century. A new plateau, with significant practical potential, was reached in the late 20th century when biotechnological methods were applied to tree taxa. Recently, the DNA in the Populus genome was sequenced. Thus, the few current commercial applications of SRWC rest on a substantial base of silvicultural and biological knowledge.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a modular and transportable bio-oil plant that can convert raw biomass into a low-viscosity liquid that, depending on the moisture content of the feedstock, increases the energy density of biomass by a factor of 6 to 7 times over green wood chips.
Abstract: ROI BioOil plants can be made modular and transportable, allowing them to be located close to the source of biomass and the subsequent transportation of high energy density BioOil to a central plant. Conversely, one central BioOil plant could supply several energy users in distributed locations, or several plants could supply numerous end-users, just as in the petroleum industry. Renewable Oil International® LLC (ROI) is one of several developers of fast pyrolysis technology. The production of BioOil can convert raw biomass into a low-viscosity liquid that, depending on the moisture content of the feedstock, increases the energy density of biomass by a factor of 6 to 7 times over green wood chips. The increase in energy density increases the amount of energy that can be hauled by standard tanker trucks versus a chip trailer van by a factor of two. Capital costs, exclusive of land costs, are comparable for a 50 MWe biomass handling system at the power plant. Land area requirements for fuel storage and handling are reduced roughly half for BioOil systems versus solid fuel handling systems. No analysis was made of operating and maintenance costs.

Journal ArticleDOI
TL;DR: Amorphous zirconia catalysts, titanium-, aluminum-, and potassium-doped Zirconias, were used in the transesterification of soybean oil with methanol at 250°C, and the esterification of n-octanoic acid with methenol at 175-200°C.
Abstract: Amorphous zirconia catalysts, titanium-, aluminum-, and potassium-doped zirconias, were prepared and evaluated in the transesterification of soybean oil with methanol at 250 °C, and the esterification of n-octanoic acid with methanol at 175–200 °C. Titanium- and aluminum-doped zirconias are promising solid catalysts for the production of biodiesel fuels from soybean oil because of their high performance, with over 95% conversion in both of the esterifications.

Journal ArticleDOI
TL;DR: In this paper, a strategy for avoiding propionic acid accumulation in the anaerobic process for bio-hydrogen generation is also introduced and the experimental results indicate that changing pH and oxidation reduction potential (ORP) can result in the variation of fermentation type, and maintaining lower ORP and avoiding pH of 5.5 will reduce the accumulation of propionic acids.
Abstract: The accumulation of propionic acid in the anaerobic process will result in low efficiency of the methanogenic phase due to the low acetogenic rate of propionic acid, and hence low wastewater treatment efficiency. The reasons for propionic acid accumulation in the acidogenic phase and the relationship between the accumulation and biohydrogen generation were studied and a strategy for avoiding propionic acid accumulation in the anaerobic process for biohydrogen generation is also introduced. The experimental results indicate that changing pH and oxidation–reduction potential (ORP) can result in the variation of fermentation type, and maintaining lower ORP and avoiding pH of 5.5 will reduce the accumulation of propionic acid in the anaerobic process. Higher biohydrogen generation rate is not always accompanied with the accumulation of propionic acid. In the acidogenic reactor of two-phase separated anaerobic process, ethanol type fermentation, in which pH at 4.5 below, can produce much more biohydrogen but without accumulation of propionic acid. Thus, ethanol-type fermentation is a better selection when using an acidogenic reactor of a two-phase separated anaerobic process to efficiently produce biohydrogen with simultaneous organic wastewater pre-treatment.

Journal ArticleDOI
TL;DR: In this paper, the authors used the CO2 evolution test to study the biodegradability of biodiesel and its mixtures with fossil diesel fuel and gasoline, showing that the synergic effect was positive in all the cases.
Abstract: Biodiesel is a clean renewable fuel with many environmental advantages. One of the most important is its good biodegradability and ability to dissolve crude oil and its derivatives. In this paper, we used the CO2 evolution test to study the biodegradability of biodiesel and its mixtures with fossil diesel fuel and gasoline. The biodegradability of biodiesel was higher than 98% after 28 days, while for diesel fuel and gasoline it was 50% and 56%, respectively. In all the cases, biodegradability increased with the addition of biodiesel. To evaluate the synergic effect, the experimental results for the mixtures were compared with a linear combination of the biodegradability values for the pure compounds. The synergic effect was positive in all the cases, demonstrating that biodiesel enhances the biodegradability of both diesel fuel and gasoline by means of cometabolism. The density and viscosity of the mixtures were also evaluated to determine the possibility of collecting them from an affected area. Although both properties increased with the addition of biodiesel, in all the cases the density was lower than that of water and the viscosity was low enough to allow pumpability.

Journal ArticleDOI
TL;DR: In this article, a process to convert Jojoba oil-wax to biodiesel by transesterification with methanol, catalysed with sodium methoxide (1.5% of the oil), was described.
Abstract: The Jojoba oil-wax is extracted from the seeds of the Jojoba ( Simmondsia chinensis Link Schneider), a perennial shrub that grows in semi desert areas in some parts of the world. The main uses of Jojoba oil-wax are in the cosmetics and pharmaceutical industry, but new uses could arise related to the search of new energetic crops. This paper summarizes a process to convert the Jojoba oil-wax to biodiesel by transesterification with methanol, catalysed with sodium methoxide (1 wt% of the oil). The transesterification reaction has been carried out in an autoclave at 60 °C, with a molar ratio methanol/oil 7.5:1, and vigorous stirring (600 rpm), reaching a quantitative conversion of the oil after 4 h. The separation of the fatty acid methyl esters (the fraction rich in FAME, 79% FAME mixture; 21% fatty alcohols; 51% of methyl cis -11-eicosenoate) from the fatty alcohols rich fraction (72% fatty alcohols; 28% FAME mixture; 26% of cis -11-eicosen-1-ol, 36% of cis -13-docosen-1-ol) has been accomplished in a single crystallization step at low temperature (−18 °C) from low boiling point petroleum ether. The fraction rich in FAME has a density (at 15 °C), a kinematic viscosity (at 40 °C), a cold filter plugging point and a high calorific value in the range of the European standard for biodiesel (EN 14214).

Journal ArticleDOI
TL;DR: Lowland switchgrass cultivars appear better suited to biomass production in the upper southeastern USA, due to their greater productivity, and two vs. one cutting per year may be of less advantage for biomass yield with lowland cultivars in this region.
Abstract: Switchgrass ( Panicum virgatum L.) is considered a good biofuels feedstock candidate. However, limited information is available on its productivity and harvest management in the upper southeastern USA. Our objective was to examine production potential of upland and lowland switchgrass cultivars in response to one- or two-cut management across the region. Upland (‘Cave-in-Rock’ and ‘Shelter’) and lowland (‘Alamo’ and ‘Kanlow’) cultivars were harvested for 3 yr under one- or two-cut management at eight sites in five states (North Carolina, Kentucky, Tennessee, Virginia, and West Virginia). Across all sites, years, and cutting managements, upland cultivars yielded 12.6 vs. 15.8 Mg ha −1 for lowland cultivars. Both cultivars yielded more on average with two harvests rather than one, but the effect was greater for upland cultivars (36% more biomass), while lowland cultivars yielded only 8% more biomass with two harvests. Tiller densities were higher for Alamo (lowland) than for Cave-in-Rock (upland) and higher with two-cut than with one-cut management. Early season production of Alamo (a cultivar of southern origin) appeared sensitive to low temperatures. Weak linear responses to precipitation were observed for first-cut biomass, but none was observed for summer precipitation. Lowland switchgrass cultivars appear better suited to biomass production in the upper southeastern USA, due to their greater productivity. Two vs. one cutting per year may be of less advantage for biomass yield with lowland cultivars in this region. However, if upland cultivars are used, two harvests may be of benefit dependent upon production costs and feedstock quality.

Journal ArticleDOI
TL;DR: In this paper, the performance and emissions of a single-cylinder engine running on simulated bio-gas and commercial seed oil was examined. But the results showed that specific fuel consumption was about the same and specific NOx emissions were lower with bio-fuel than results from the spark-ignition engine tests running on biogas.
Abstract: An experimental programme examining performance and emissions from spark- and compression-ignition engines, running on a variety of bio-fuels, including simulated bio-gas and commercial seed oil is presented. Both engines were single-cylinder laboratory-type engines of comparable power output having variable speed and load capability, the spark-ignition engine additionally having variable compression ratio. For bio-gas, containing carbon dioxide, emissions of oxides of nitrogen were reduced relative to natural gas, while unburnt hydrocarbons were increased. Brake power and specific fuel consumption changed little and carbon monoxide was predominantly affected by air:fuel ratio. Equivalent effects were demonstrated with nitrogen replacing carbon dioxide in the simulated bio-gas and similar trends were evident as compression ratio was increased. Seed-oil bio-fuel gave similar performance to diesel fuel without major disadvantages, other than an increased specific fuel consumption. Tests with cetane and rape-seed methyl ester bio-diesel are also presented for comparison. Specific fuel consumption was about the same and specific NOx emissions were lower with bio-fuel than results from the spark-ignition engine tests running on biogas.

Journal ArticleDOI
TL;DR: In this paper, different methods for the determination of the mechanical durability (DU) of pellets and briquettes were compared by international round robin tests including different laboratories, and the results showed that the measured DU values and their variability are influenced by the applied method.
Abstract: Different methods for the determination of the mechanical durability (DU) of pellets and briquettes were compared by international round robin tests including different laboratories. The DUs of five briquette and 26 pellet types were determined. For briquettes, different rotation numbers of a prototype tumbler and a calculated DU index are compared. For pellets testing, the study compares two standard methods, a tumbling device according to ASAE S 269.4, the Lignotester according to ONORM M 7135 and a second tumbling method with a prototype tumbler. For the tested methods, the repeatability, the reproducibility and the required minimum number of replications to achieve given accuracy levels were calculated. Additionally, this study evaluates the relation between DU and particle density. The results show for both pellets and briquettes, that the measured DU values and their variability are influenced by the applied method. Moreover, the variability of the results depend on the biofuel itself. For briquettes of DU above 90%, five replications lead to an accuracy of 2%, while 39 replications are needed to achieve an accuracy of 10%, when briquettes of DU below 90% are tested. For pellets, the tumbling device described by the ASAE standard allows to reach acceptable accuracy levels (1%) with a limited number of replications. Finally, for the tested pellets and briquettes no relation between DU and particle density was found. r 2006 Elsevier Ltd. All rights reserved.

Journal ArticleDOI
TL;DR: For example, Short-rotation woody crops (SRWC) have been established for purposes other than as dedicated bioenergy feedstocks, however, portions of the crops are (or are planned to be) used for bioenergy production as discussed by the authors.
Abstract: Bioenergy consumption is greatest in countries with heavy subsidies or tax incentives, such as China, Brazil, and Sweden. Conversion of forest residues and agricultural residues to charcoal, district heat and home heating are the most common forms of bioenergy. Biomass electric generation feedstocks are predominantly forest residues (including black liquor), bagasse, and other agricultural residues. Biofuel feedstocks include sugar from sugarcane (in Brazil), starch from maize grain (in the US), and oil seeds (soy or rapeseed) for biodiesel (in the US, EU, and Brazil). Of the six large land areas of the world reviewed (China, EU, US, Brazil, Canada, Australia), total biomass energy consumptions amounts to 17.1 EJ. Short-rotation woody crops (SRWC) established in Brazil, New Zealand, and Australia over the past 25 years equal about 50,000 km2. SRWC plantings in China may be in the range of 70,000–100,000 km2. SRWC and other energy crops established in the US and EU amount to less than 1000 km2. With some exceptions (most notably in Sweden and Brazil), the SRWC have been established for purposes other than as dedicated bioenergy feedstocks, however, portions of the crops are (or are planned to be) used for bioenergy production. New renewable energy incentives, greenhouse gas emission targets, synergism with industrial waste management projects, and oil prices exceeding 60 $ Bbl−1 (in 2005) are major drivers for SRWC or energy crop based bioenergy projects.

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the prospects of a more widespread utilisation of willow plantations for wastewater treatment in Sweden, including existing incentives and barriers, based on current knowledge and experience.
Abstract: The concept of willow vegetation filters for the treatment of nutrient-rich wastewater has the potential to address two of our most serious environmental problems today -water pollution and climate change- in a cost-efficient way. Despite several benefits, including high treatment efficiency, increased biomass yields, improved energy and resource efficiency, and cost savings, willow vegetation filters have so far only been implemented to a limited degree in Sweden. This is due to various kinds of barriers, which may be the result of current institutional, structural and technical/geographical conditions. This paper discusses the prospects of a more widespread utilisation of willow plantations for wastewater treatment in Sweden, including existing incentives and barriers, based on current knowledge and experience. © 2005 Elsevier Ltd. All rights reserved.

Journal ArticleDOI
TL;DR: In this paper, a microbial catalyst Clostridium carboxidivorans P7T was used to convert biomass-generated producer gas to ethanol and acetic acid.
Abstract: In our previous work, we demonstrated that biomass-generated producer gas can be converted to ethanol and acetic acid using a microbial catalyst Clostridium carboxidivorans P7T. Results showed that the producer gas (1) induced cell dormancy, (2) inhibited H2 consumption, and (3) affected the acetic acid/ethanol product distribution. Results of this work showed that tars were the likely cause of cell dormancy and product redistribution and that the addition of a 0.025 μm filter in the gas cleanup negated the effects of tars. C. carboxidivorans P7T can adapt to the tars (i.e. grow) only after prolonged exposure. Nitric oxide, present in the producer gas at 150 ppm, is an inhibitor of the hydrogenase enzyme involved in H2 consumption. We conclude that significant conditioning of the producer gas will be required for the successful coupling of biomass-generated producer gas with fermentation to produce ethanol and acetic acid.

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TL;DR: The use of forest fuels has more than doubled in Sweden over the last 25-30 years as discussed by the authors and almost a fifth of the utilized energy is now based on forest biomass, while real prices of bioenergy have decreased to less than a third of what they were 25 years ago.
Abstract: The use of forest fuels has more than doubled in Sweden over the last 25–30 years. Almost a fifth of the utilized energy is now based on forest biomass. Concurrently, real prices of bioenergy have decreased to less than a third of what they were 25 years ago. Some principal driving forces behind this development are identified and discussed in this paper. The origin of this development was equally the result of a foreseen shortage of fibre and a reaction to this vulnerable position, made obvious through the ‘oil crises’. Although Sweden has a long tradition of large-scale use of forest energy, 35 years ago she was almost totally dependent on imported oil. Forest mechanisation provided rational solutions to handling small diameter wood and stumps in conventional industrial processes, but also enabled the economical use of such wood for energy. During 3 decades of development, drivers and obstacles have shifted. What started to reduce dependence on fossil fuels was later driven by increased general environmental awareness. An emerging ‘green’ lobby blocked the development of nuclear power and expanded harnessing of hydropower which were alternative means of self-sufficiency. In the last 10–15 years, focus has changed again. Global concern for climatic change due to emissions of greenhouse gases is a powerful driver, endorsing increased use of CO 2 -neutral energy sources. Sustainability, resource cycling and the welfare of future generations are seen as goals for continued development. Ideals and policies do not, however, automatically induce change in regular operations. A set of drivers is identified, that has played the decisive role in practice. These include the direct technical–operational drivers, as well as indirect drivers through market development, taxation and other legislation.

Journal ArticleDOI
Bernd Linke1
TL;DR: Anaerobic treatment of solid wastes from potato processing was studied in completely stirred tank reactors (CSTR) at 55 °C with special attention paid to the effect of increased organic loading rate (OLR) on the biogas yield in long-term experiments.
Abstract: Anaerobic treatment of solid wastes from potato processing was studied in completely stirred tank reactors (CSTR) at 55 °C. Special attention was paid to the effect of increased organic loading rate (OLR) on the biogas yield in long-term experiments. Both biogas yield and CH 4 in the biogas decreased with the increase in OLR. For OLR in the range of 0.8 gl −1 d −1 –3.4 gl −1 d −1 , biogas yield and CH 4 obtained were 0.85 l g −1 –0.65 l g −1 and 58%–50%, respectively. Biogas yield y as a function of maximum biogas yield y m , reaction rate constant k and HRT are described on the basis of a mass balance in a CSTR and a first order kinetic. The value of y m can be obtained from curve fitting or a simple batch test and k results from plotting y /( y m − y ) against 1/OLR from long-term experiments. In the present study values for y m and k were obtained as 0.88 l g −1 and 0.089 d −1 , respectively. The simple model equations can apply for dimensioning completely stirred tank reactors (CSTR) digesting organic wastes from food processing industries, animal waste slurries or biogas crops.

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TL;DR: In this paper, micro-level data from wood energy producers in Hedmark County were gathered and analyzed to find how much greenhouse gas (GHG) emissions various kinds of wood energy cause (not only CO2, but also CH4 and N2O), which energy they substitute, their potential to reduce GHG emissions, and the major sources of uncertainty.
Abstract: In this study, micro-level data from wood energy producers in Hedmark County were gathered and analysed. The aim was to find how much greenhouse gas (GHG) emissions various kinds of wood energy cause (not only CO2, but also CH4 and N2O), which energy they substitute, their potential to reduce GHG emissions, and the major sources of uncertainty. The method was life cycle assessment. Six types of wood energy were studied: fuel wood, sawdust, pellets, briquettes, demolition wood, and bark. GHG emissions over the life cycle of the wood energy types in this study are 2–19% of the emissions from a comparable source of energy. The lowest figure is for demolition wood substituting oil in large combustion facilities, the highest for fuel wood used in dwellings to substitute electricity produced by coal-based power plants. Avoided GHG emissions per m3 wood used for energy were from 0.210 to 0.640 tonne CO2-equivalents. Related to GWh energy produced, avoided GHG emissions were from 250 to 360 tonne CO2-equivalents. Avoided GHG emissions per tonne CO2 in the wood are 0.28–0.70 tonne CO2-equivalents. The most important factors were technology used for combustion, which energy that is substituted, densities, and heating values. Inputs concerning harvest, transport, and production of the wood energy are not important. Overall, taking the uncertainties into account there is not much difference in avoided GHG emissions for the different kinds of wood energy.