Showing papers in "Biomass & Bioenergy in 2013"
TL;DR: In this paper, the authors examined three aspects of micro-algae production that will ultimately determine the future economic viability and environmental sustainability: the energy and carbon balance, environmental impacts and production cost.
Abstract: Micro-algae have received considerable interest as a potential feedstock for producing sustainable transport fuels (biofuels). The perceived benefits provide the underpinning rationale for much of the public support directed towards micro-algae research. Here we examine three aspects of micro-algae production that will ultimately determine the future economic viability and environmental sustainability: the energy and carbon balance , environmental impacts and production cost . This analysis combines systematic review and meta-analysis with insights gained from expert workshops. We find that achieving a positive energy balance will require technological advances and highly optimised production systems. Aspects that will need to be addressed in a viable commercial system include: energy required for pumping, the embodied energy required for construction, the embodied energy in fertilizer, and the energy required for drying and de-watering. The conceptual and often incomplete nature of algae production systems investigated within the existing literature, together with limited sources of primary data for process and scale-up assumptions, highlights future uncertainties around micro-algae biofuel production. Environmental impacts from water management, carbon dioxide handling, and nutrient supply could constrain system design and implementation options. Cost estimates need to be improved and this will require empirical data on the performance of systems designed specifically to produce biofuels. Significant (>50%) cost reductions may be achieved if CO 2 , nutrients and water can be obtained at low cost. This is a very demanding requirement, however, and it could dramatically restrict the number of production locations available.
708 citations
TL;DR: In this article, a review of the available literature is presented, analyzing the influence of parameters such as temperature, holding time and catalyst dosage on the yield and properties of the different product fractions.
Abstract: Among the various types of biomass, microalgae have the potential of becoming a significant energy source for biofuel production in the coming years. Currently, research is mainly focusing on optimization of the cultivation methods and the conversion of just a single microalgae fraction (lipids for biodiesel production). Hydrothermal liquefaction is a method for thermochemical conversion of wet microalgae, producing a liquid energy carrier called ‘bio-oil’ or ‘biocrude’, next to gaseous, aqueous and solid by-products. A review of the available literature is presented here, analyzing the influence of parameters such as temperature, holding time and catalyst dosage on the yield and properties of the different product fractions. Also, the strain selection and the status of the technology for hydrothermal processes are analyzed. Finally, based on the findings obtained from the literature review, directions for future research are suggested.
608 citations
TL;DR: In this article, a review of the technologies for removing contaminants from raw syngas is presented, which are classified according to the gas temperature exiting the cleanup device: hot, cold, and warm.
Abstract: Syngas from gasification of carbonaceous feedstocks is used for power production and synthesis of fuels and commodity chemicals. Impurities in gasification feedstocks, especially sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temperature exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the technical difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine.
480 citations
TL;DR: In this article, a pretreatment process for making a homogenized, carbon rich, and energy-dense solid fuel, called biochar, from lignocellulosic biomass is described.
Abstract: Hydrothermal carbonization (HTC) is a pretreatment process for making a homogenized, carbon rich, and energy-dense solid fuel, called biochar, from lignocellulosic biomass. Corn stover, miscanthus, switch grass, and rice hulls were treated with hot compressed water at 200, 230, and 260 °C for 5 min. Mass yield is as low as 41% of the raw biomass, and decreases with increasing HTC temperature. Higher heating values (HHV) increase up to 55% with HTC pretreatment temperature. Up to 90% of calcium, magnesium, sulfur, phosphorus, and potassium were removed with HTC treatment possibly due to hemicellulose removal. At a HTC temperature of 260 °C, some structural Si was removed. All heavy metals were reduced by HTC treatment. The slagging and fouling indices are reduced with HTC treatment relative to that of untreated biomass. Chlorine content, a concern only for raw and HTC 200 switch grass, was reduced to a low slagging range at 230 °C, and 260 °C. Alkali index was medium for raw biomass but decreased by HTC.
376 citations
TL;DR: In this article, the authors provide a consolidated source of information on studies using high-solids loadings in enzymatic hydrolysis, including a brief discussion of the limitations, such as a lack of available water, difficulty with mixing and handling, insufficient mass and heat transfer, and increased concentration of inhibitors, associated with the use of high solids.
Abstract: Enzymatic hydrolysis is the unit operation in the lignocellulose conversion process that utilizes enzymes to depolymerize lignocellulosic biomass. The saccharide components released are the feedstock for fermentation. When performed at high-solids loadings (≥15% solids, w/w), enzymatic hydrolysis potentially offers many advantages over conversions performed at low- or moderate-solids loadings, including increased sugar and ethanol concentrations and decreased capital and operating costs. The goal of this review is to provide a consolidated source of information on studies using high-solids loadings in enzymatic hydrolysis. Included in this review is a brief discussion of the limitations, such as a lack of available water, difficulty with mixing and handling, insufficient mass and heat transfer, and increased concentration of inhibitors, associated with the use of high solids, as well as descriptions and findings of studies that performed enzymatic hydrolysis at high-solids loadings. Reactors designed and/or equipped for improved handling of high-solids slurries are also discussed. Lastly, this review includes a brief discussion of some of the operations that have successfully scaled-up and implemented high-solids enzymatic hydrolysis at pilot- and demonstration-scale facilities.
376 citations
TL;DR: In this article, the use of biochar to improve soil fertility and reduce metal concentrations in shoots was investigated in the presence of heavy metals in a corn field, and the results showed that the harvested biomass could be used as feedstock for pyrolysis to produce bioenergy and new biochar, which could contribute further to the reduction of CO 2 emission.
Abstract: Phytoremediation of soils contaminated by heavy metals was tested by liming (CaCO 3 ) or adding biochar (1%, 5% and 10%, mass fraction) and by growing rapeseed (Brassica napus L.), a common bioenergy crop. Bioavailable metal concentrations (0.01molL -1 CaCl 2 extraction) decreased with increasing concentrations of biochar amendment. The reduction reached 71%, 87% and 92% for Cd, Zn and Pb respectively in the presence of 10% biochar. Twelve weeks after sowing, all plants cultivated on the untreated soil and on the soil amended by biochar at 1% had died, while the plants grew normally on the soil that had the other treatments. Compared to liming, treatment with 10% biochar proved equally efficient in reducing metal concentrations in shoots but the biomass production tripled as a result of the soil fertility improvement. Thus, in addition to C sequestration, the incorporation of biochar into metal-contaminated soils could make it possible to cultivate bioenergy crops without encroaching on agricultural lands. Although additional investigations are needed, we suggest that the harvested biomass might in turn be used as feedstock for pyrolysis to produce both bioenergy and new biochar, which could contribute further to the reduction of CO 2 emission. © 2013 Elsevier Ltd.
341 citations
TL;DR: In this paper, the authors shed some light into this subject to help the understanding of the importance of the various impacts of the straw blanket on the ground, the availability and quality of straw, the economics of straw recovery and use and the main criteria for determining the amount of straw that can be recovered for bioenergy or biofuels production.
Abstract: Sugarcane straw represents, under Brazilian conditions, approximately one third of the total primary energy of sugarcane in the field. Today, its use for energy is incipient and it is mostly wasted by either burning in the pre-harvest or left on the ground to decay. Besides its potential use as feedstock for energy production, there are several possible agronomic benefits of the straw blanket left on the ground such as soil protection against erosion, increase of soil organic carbon content, inhibition of weed growth, nutrient recycling and reduction of soil water losses, to name a few. The balance of the impacts and the economic and energetic value of the straw indicate that the amount of the straw left on the ground that could be considered optimal is dependent on the local conditions, agricultural practices, characteristics of the straw and intended final use. This work is meant to shed some light into this subject to help the understanding of the importance of the various impacts of the straw blanket on the ground, the availability and quality of the straw, the economics of straw recovery and use and the main criteria for determining the amount of straw that can be recovered for bioenergy or biofuels production.
259 citations
TL;DR: In this article, the authors studied the thermo-chemical conversion of green microalgae Chlamydomonas reinhardtii (CCAP 11/32C), its cell wall deficient mutant Chlorella vulgaris and their proteins and lipids under conditions of intermediate pyrolysis.
Abstract: The thermo-chemical conversion of green microalgae Chlamydomonas reinhardtii wild type (CCAP 11/32C), its cell wall deficient mutant C. reinhardtii CW15 (CCAP 11/32CW15) and Chlorella vulgaris (CCAP 211/11B) as well as their proteins and lipids was studied under conditions of intermediate pyrolysis. The microalgae were characterised for ultimate and gross chemical composition, lipid composition and extracted products were analysed by Thermogravimetric analysis (TG/DTG) and Pyrolysis-gaschromatography/mass-spectrometry (Py-GC/MS). Proteins accounted for almost 50% and lipids 16-22 % of dry weight of cells with little difference in the lipid compositions between the C. reinhardtii wild type and the cell wall mutant. During TGA analysis, each biomass exhibited three stages of decomposition, namely dehydration, devolatilization and decomposition of carbonaceous solids. Py-GC/MS analysis revealed significant protein derived compounds from all algae including toluene, phenol, 4-methylphenol, 1H-indole, 1H-indole-3methyl. Lipid pyrolysis products derived from C. reinhardtii wild type and C. reinhardtii CW15 were almost identical and reflected the close similarity of the fatty acid profiles of both strains. Major products identified were phytol and phytol derivatives formed from the terpenoid chain of chlorophyll, benzoic acid alkyl ester derivative, benzenedicarboxylic acid alkyl ester derivative and squalene. In addition, octadecanoic acid octyl ester, hexadecanoic acid methyl ester and hydrocarbons including heptadecane, 1-nonadecene and heneicosane were detected from C. vulgaris pyrolysed lipids. These results contrast sharply with the types of pyrolytic products obtained from terrestrial lignocellulosic feedstocks and reveal that intermediate pyrolysis of algal biomass generates a range of useful products with wide ranging applications including bio fuels.
243 citations
TL;DR: In this paper, the structural analysis of lignin is divided into qualitative and quantitative analyses, and different analytical methods could provide significantly different results that are even sometimes not directly comparable, and the magnetic resonance techniques have proved to be efficient analytical tools for the structural elucidation of these complex biopolymers.
Abstract: Agricultural by-products are the most promising feedstock for the generation of renewable, carbon neutral substitutes for synthetic materials (e.g. biofuel, building materials). The demand for efficient utilisation of lignin biomass has induced detailed analyses of its fundamental chemical structures and development of analysing technologies. This paper reviews the structural analysis techniques for straw lignin together with the morphology of the lignin biomass and the study of the form and structure of organisms and their specific structural features. The review showed that the studies on lignin could be divided into the qualitative and quantitative analyses; different analytical methods could provide significantly different results that are even sometimes not directly comparable. Among many techniques reviewed, the magnetic resonance techniques have proved to be efficient analytical tools for the structural elucidation of these complex biopolymers. Quantitative and qualitative structural analysis of lignin indicated a great potential for industrial crops optimisation due to in-depth microstructure interpretation, and detailed and accurate chemical composition although the composition and structure of straw lignin have been discovered highly complex and varied considerably within and among plants. The structure of lignin has remained one of the most difficult biopolymers to characterise, however recent advances in analytical chemistry and spectroscopy have dramatically improved the understanding of this natural resource, and further value added utilisations are being expected for the lignin and its related biomass.
233 citations
TL;DR: In this article, the authors reviewed advances on causes and consequences of global climate change and its impact on nature and society and highlighted the different management and research strategies in forestry, agriculture, agroforestry and grasslands to mitigate the global warming.
Abstract: Rising level of atmospheric CO2 and consequent global warming is evident. Global surface temperature have already increased by 0.8 °C over the 20th century and is projected to increase by 1.4–5.8 °C during the twenty-first century. The global warming will continue till atmospheric concentrations of the major greenhouse gases are stabilized. Among them, CO2 is mainly responsible and is expected to account for about 60% of the warming over the next century. This study reviews advances on causes and consequences of global climate change and its impact on nature and society. Renewable biomass has tremendous potential to mitigate the global warming. Renewable biomass is expected to play a multifunctional role including food production, source of energy and fodder, biodiversity conservation, yield of goods and services to the society as well as mitigation of the impact of climate change. The review highlights the different management and research strategies in forestry, agriculture, agroforestry and grasslands to mitigate the global warming.
219 citations
TL;DR: The main purpose of all pretreatment methods is to modify the biosludge characteristics in such a way to boost settling of cells and solid particles of sludge, and to ease the release of water molecules from extracellular polymeric substances and cells and to facilitate flow of water through forming filter cake as mentioned in this paper.
Abstract: Difficulties in dewatering of biosludge result in economical and environmental issues for wastewater treatment plants. Various attempts have been made to overcome this problem by achieving some pretreatment on biosludge. The main purpose of all pretreatment methods is to modify the biosludge characteristics in such a way to boost settling of cells and solid particles of sludge, and to ease the release of water molecules from extracellular polymeric substances and cells and to facilitate flow of water through forming filter cake. The present work presents an overview of different properties of sludge and their measurement, the main reasons of sludge dewatering difficulty, the fundamentals of sludge dewatering and various proposed methods for sludge pretreatment. The advantages and drawbacks of different methods are described and the dominance of one over the others is discussed mostly with respect to energy requirement and environmental impacts. Some recommendations have been made for optimal application of each method.
TL;DR: In this article, the authors examined bio-oil and bio-char fuel produced from Spirulina Sp. by slow pyrolysis and found that the suitable temperature to obtain biochar and biooil were at approximately 500 and 550°C respectively.
Abstract: This study examined bio-oil and bio-char fuel produced from Spirulina Sp. by slow pyrolysis. A thermogravimetric analyser (TGA) was used to investigate the pyrolytic characteristics and essential components of algae. It was found that the temperature for the maximum degradation, 322 °C, is lower than that of other biomass. With our fixed-bed reactor, 125 g of dried Spirulina Sp. algae was fed under a nitrogen atmosphere until the temperature reached a set temperature between 450 and 600 °C. It was found that the suitable temperature to obtain bio-char and bio-oil were at approximately 500 and 550 °C respectively. The bio-oil components were identified by a gas chromatography/mass spectrometry (GC–MS). The saturated functional carbon of the bio-oil was in a range of heavy naphtha, kerosene and diesel oil. The energy consumption ratio (ECR) of bio-oil and bio-char was calculated, and the net energy output was positive. The ECR had an average value of 0.49.
TL;DR: In this paper, the 13 C NMR spectroscopy, scanning electron microscopy and energy-dispersive X-ray Spectroscopy and black carbon results confirmed these observations showing that hydrochars have lower proportions of aromatic compounds than biochars (less stable) but are rich in functional groups (higher cation exchange capacity) than biocharars.
Abstract: Technologies for agro-industrial feedstock utilization such as pyrolysis, gasification and hydrothermal carbonization at industrial scale develop rapidly. The thermochemically converted biomasses of these production technologies have fundamentally different properties controlled by the production technology. This is reflected by general properties such as pH or elemental composition. The 13 C NMR spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy and black carbon results confirmed these observations showing that hydrochars have lower proportions of aromatic compounds than biochars (less stable) but are rich in functional groups (higher cation exchange capacity) than biochars. Analyses of pollutants indicate that polycyclic aromatic hydrocarbons as well as dioxin contents of most samples were under the threshold values recommended by International Biochar Initiative and European Biochar Certificate. In conclusion, biochars and hydrochars are entirely different from each other and these materials will probably have a complementary reaction in a soil environment.
TL;DR: In this article, a review of relevant scientific research concerning the conversion of crude glycerol discharged after bio-diesel (fatty acid methyl/ethyl esters) manufacturing process into value-added products through biological methods with Yarrowia lipolytica yeast is presented.
Abstract: Unconventional and nonpathogenic Yarrowia lipolytica yeast has been addressed in various studies conducted in many research centers, and in recent years has been perceived as an especially attractive host for many applications of glycerol. In its initial paragraphs, this review article provides a short characteristics of Y. lipolytica ; followed by biodiesel production and brief characteristics of crude glycerol. Further on, this review summarizes relevant scientific research concerning the conversion of crude glycerol discharged after bio-diesel (fatty acid methyl/ethyl esters) manufacturing process into value-added products through biological methods with Y. lipolytica yeast. The feasibility of using Y. lipolytica biomass, rich in proteins and oils, as food and feed additives is described as well. Subsequently, different strategies employed to produce and improve yield and productivity of organic acids (citric, pyruvic and α-ketoglutaric acid) are presented. And, finally, the biosynthesis of new products, such as erythritol, mannitol and invertase, whose synthesis from glycerol by Y. lipolytica would be advantageous when compared with their production from common sugars, is evaluated. In conclusion, an actual wide range of compounds that can be produced from glycerol by Y. lipolytica are shown to be a valuable contribution to the development of the biodiesel industry as well as a cost-effective fermentation based on renewable resources.
TL;DR: In this article, the authors describe the trend of utilizing oil palm residue, i.e. the empty fruit bunches (EFB) left after extraction of the palm oil, using a case study of Malaysia, which is one of the world's major palm oil producers, and discusses the environmental performance of recycling technologies being developed in Malaysia for fuel, fiber, and fertilizer.
Abstract: This paper describes the trend of utilizing oil palm residue, i.e. the empty fruit bunches (EFB) left after extraction of the palm oil, using a case study of Malaysia, which is one of the world's major palm oil producers, and discusses the environmental performance of recycling technologies being developed in Malaysia for fuel, fiber, and fertilizer. Seven technologies are analyzed: ethanol production, methane recovery, briquette production, biofuel for combined heat and power (CHP) plants, composting, medium density fiberboard (MDF) production, and pulp and paper production. The life cycle assessment (LCA) method is used to discuss the environmental impacts of these technologies for adding value to this biomass. Sensitivity analyses are conducted to determine the land use effects for the various technologies utilizing EFB and to estimate the energy generation potential of raw EFB in CHP plants and methane production. Among the technologies for energy production, CHP plants have the best performance if the electricity generated is connected to the national grid, with superior benefits in the majority of impact categories compared to briquette, methane, and ethanol production. Overall, we find that methane recovery and composting are more environmentally friendly than other technologies, as measured by reduction of greenhouse gas emissions. Pulp and paper, and MDF production are favorable technologies for land use impacts; however, they have intense primary energy requirements, chemical use in the processes, and emissions from their waste treatment systems. Our results provide information for decision makers when planning for sustainable use of oil palm biomass.
TL;DR: This work demonstrates an ecological approach to overcome the current limitations of cultivation strategies and manipulates a basic environmental parameter, salinity, to promote algal growth and limit invading organisms.
Abstract: Mass production of microalgae is currently limited by existing cultivation strategies, which rely heavily on open cultivation systems. Increasing lipid production in these systems while minimizing the invasion of non-target algae (competitors) and grazers (predators) will improve the economic viability of algal biofuel. In this study, we manipulate a basic environmental parameter, salinity, to promote algal growth and limit invading organisms. We monitor the growth of marine microalga Nannochloropsis salina and invasion of algal competitors and predators in open cultures grown at different salinities ranging from brackish to hypersaline. Algal growth and biomass was greatest at salinities of 22 and 34 PSU, whereas the density of invading organisms was lowest at 22 PSU. To determine if lipid accumulation could be maximized by salinity stress, we grew N. salina at 22 PSU until the populations were at stationary phase and then increased salinity to 34, 46, and 58 PSU. Gravimetrically determined lipid content increased significantly at these higher salinities, and was highest at 34 PSU (36% dry tissue mass). Analysis of Folch extracts by FT-ICR mass spectrometry showed a monotonic increase in triglyceride content and decreased membrane lipid content with increased salinity. Together, this work demonstrates an ecological approach to overcome the current limitations of cultivation strategies.
TL;DR: In this paper, the authors report on the preparation of biomass-based activated carbons by the steam physical activation and KOH chemical activation methods and investigate their adsorption performance.
Abstract: We report on the preparation of biomass-based activated carbons by the steam physical activation and KOH chemical activation methods. In addition, we also investigate their adsorption performance. By adjusting the reaction parameters, different carbon materials are prepared from corn residues and characterized using instrumental analyses such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Brunauer–Emmett–Teller (BET). It is found that the synthesized activated carbons exhibit high surface area (1600 m 2 g −1 ) and large pore volume (2.01 cm 3 g −1 ). Furthermore, the high methylene blue and iodine adsorption value and a considerable CO 2 uptake (exceeding 1.5 mmol g −1 ) are attained with the activated carbons, showing their potential usage for the CO 2 adsorbent.
TL;DR: In order to enhance the production of BC, the residues were supplemented with nitrogen (N) and phosphate sources to overcome possible nutritional limitations and it was verified an increase on the BC production between 21.5% and 43.2% when compared with no supplementation.
Abstract: Bacterial Cellulose (BC), produced by many bacteria specially those belonging to the Gluconacetobacter genus, is a very peculiar cellulose form that bears unique mechanical and structural properties that can be exploited in numerous applications. However, the production costs of BC are very high because of the use of quite expensive culture media. In this sense, the purpose of this work was to evaluate the possibility of use residues from the olive oil production industry as nutrient and carbon source for the production of BC by Gluconacetobacter sacchari . The dry olive mill residue (DOR) was submitted to water extraction at 40 and 100 °C (DOR40 and DOR100) and to hydrolysis with H 2 SO 4 1M (DOR100H) in order to obtain sugar rich aqueous extracts to be used for BC production. The BC production obtained without addiction of any type of nutrients was 0.81 g L −1 for DOR40 and 0.85 g L −1 for DOR100 after 96 h incubation, which corresponded respectively to 32 and 34% of the production achieved with conventional HS culture medium (around 2.5 g L −1 ). In order to enhance the production of BC, the residues were supplemented with nitrogen (N) and phosphate (P) sources to overcome possible nutritional limitations. It was verified an increase on the BC production between 21.5% (N8 P4,5) and 43.2% (N1 P8) when compared with no supplementation. These are promising results to overcome high BC production costs.
TL;DR: In this paper, the effects of water depth, liquid velocity and the presence, or absence, of sump baffles to improve the CO2 supply transfer were considered in relation to on the power consumption, residence time and mixing in the reactor.
Abstract: The fluid dynamic characterization of a 100 m length × 1 m wide channel raceway photobioreactor was carried out. The effects of water depth, liquid velocity and the presence, or absence, of sump baffles to improve the CO2 supply transfer were considered in relation to on the power consumption, residence time and mixing in the reactor was studied. When operated at a depth of 20 cm, the power consumption was between 1.5 and 8.4 W m?3 depending on the forward velocity, with higher values occurring when the baffle was in place. Residence times and the degree of mixing at each section of the raceway (paddlewheel, bends, channels and sump) were measured experimentally. Mixing occurred mainly in the sump, paddlewheel and bends, with a maximum dispersion coefficient of 0.07 m2 s?1. These sections, however, only contributed a small fraction to the total volume of the raceway. Bodenstein numbers from 200 to 540 for the channel sections indicated plug-flow characteristics. Mixing times ranged from 1.4 to 6 h, with the presence of the baffle greatly increasing these times despite higher specific power consumption. A total of 15–20 circuits of the raceway were needed to achieve complete mixing without the baffle, compared to 30–40 cycles with the baffle. Vertical mixing was very poor whereas axial mixing was similar to that achieved in closed photobioreactors. The methodologies applied were shown to be useful in determining the fluid dynamics of a raceway photobioreactor. Equations useful in simulating the power consumption as a function of the design and operation parameters have been validated.
TL;DR: This article seeks to provide a bridge between energy modelling and spatial planning while integrating research and techniques in energy modelling with Geographic Information Science, which encompasses GIS, remote sensing, spatial disaggregation techniques and geovisualization.
Abstract: Renewable energy will play a crucial role in the future society of the 21st century. The various renewable energy sources need to be balanced and their use carefully planned since they are characterized by high temporal and spatial variability that will pose challenges to maintaining a well balanced supply and to the stability of the grid. This article examines the ways that future ‘energy landscapes’ can be modelled in time and space. Biomass needs a great deal of space per unit of energy produced but it is an energy carrier that may be strategically useful in circumstances where other renewable energy carriers are likely to deliver less. A critical question considered in this article is whether a massive expansion in the use of biomass will allow us to construct future scenarios while repositioning the ‘energy landscape’ as an object of study. A second important issue is the utilization of heat from biomass energy plants. Biomass energy also has a larger spatial footprint than other carriers such as, for example, solar energy. This article seeks to provide a bridge between energy modelling and spatial planning while integrating research and techniques in energy modelling with Geographic Information Science. This encompasses GIS, remote sensing, spatial disaggregation techniques and geovisualization. Several case studies in Austria and Germany demonstrate a top-down methodology and some results while stepwise calculating potentials from theoretical to technically feasible potentials and setting the scene for the definition of economic potentials based on scenarios and assumptions.
TL;DR: In this paper, the compatibility of the EU 2020 targets for renewable energy with conservation of biodiversity is discussed based on literature and six country studies (Belgium, Denmark, Finland, Netherlands, Sweden, Slovakia).
Abstract: Based on literature and six country studies (Belgium, Denmark, Finland, Netherlands, Sweden, Slovakia) this paper discusses the compatibility of the EU 2020 targets for renewable energy with conservation of biodiversity.
We conclude that increased demand for biomass for bioenergy purposes may lead to a continued conversion of valuable habitats into productive lands and to intensification, which both have negative effects on biodiversity. On the other hand, increased demand for biomass also provides opportunities for biodiversity, both within existing productive lands and in abandoned or degraded lands. Perennial crops may lead to increased diversity in crop patterns, lower input uses, and higher landscape structural diversity which may all have positive effects on biodiversity.
In production forest opportunities exist to harvest primary wood residues. Removal of these forest residues under strict sustainability conditions may become economically attractive with increased biomass demand.
An additional biomass potential is represented by recreation areas, road-side verges, semi-natural and natural areas and lands which have no other use because they have been abandoned, polluted or degraded.
Whether effects of cropping of biomass and/or removal of biomass has positive or negative impact on biodiversity depends strongly on specific regional circumstances, the type of land and land use shifts involved and the associated management practices in general. However, it is clear that in the six countries studied certain types of biomass crops are likely to be more sustainable than others.
TL;DR: Modifying genes and proteins involved in cellulose synthesis resulted in an unusual secondary cell wall deposition and composition and a lower crystallinity index, thus making lignocellulosic ethanol production economically viable.
Abstract: Plant biomass, or lignocellulosic biomass, is evaluated worldwide as a potential feedstock for the sustainable production of bioenergy in the near future due to its abundance, availability and renewability. Promising sources of plant biomass include agricultural residues and energy crops; however, the natural recalcitrance of this material is a major bottleneck for lignocellulose-derived ethanol production. The current process requires pre-treatment with severe conditions to disrupt the plant cell wall structures and remove hemicellulose and lignin components so that cellulose is more accessible to cellulases. However, the generation of enzyme inhibitors/deactivators and toxic substances during pre-treatment may subsequently affect enzymatic saccharification and fermentation processing. The pre-treatment and saccharification processability can be simplified if the plant biomass resistance to biochemical or enzymatic treatment is reduced. While there are many developed pre-treatment technologies and formulated enzyme cocktails that match pre-treated substrates, there has been attempt to design ideal energy crops via plant genetic manipulation. Cellulose engineering is aimed at reducing the crystallinity of cellulose structures. Expression of cellulose-disrupting proteins, including carbohydrate-binding modules, expansins, and swollenins, produces irregular forms of cellulose fibrils, which change from tightly packed fibrils to splayed ribbons with a high sugar release after enzymatic treatment. In addition, modifying genes and proteins involved in cellulose synthesis resulted in an unusual secondary cell wall deposition and composition and a lower crystallinity index. Reducing lignin content though engineering lignin biosynthesis pathways improves the saccharification process; however, abnormal growth and plant fitness remain problematic when improper genes are selected for manipulation. Lignin composition can be modified by introducing phenolic derivatives or peptide cross-links upon lignification, and these approaches might minimise the interference with plant growth and development. Hemicellulose biosynthesis is a complicated process. Currently, the reduction of hemicellulose content relies mostly on enzymes involved in xyloglucan/glucoarabinoxylan synthesis and the arrangements of those polymers in developing wood. Additionally, several glycosyltransferase and glycoside hydrolases are believed to be involved in hemicellulose modification in relation to loosened cell walls. Importantly, the expression of foreign glycoside hydrolases in plants may facilitate the reduction of enzyme loadings, thus making lignocellulosic ethanol production economically viable.
TL;DR: In this article, the authors present different combinations of scenarios for global feedstock supply for the production of bioenergy under specified social and environmental safeguard provisions, and the aggregate results, achieved through the application of an integrated global modeling cluster, indicate that under a high global demand for bioenergy by mid-century, biomass will to a large extent be sourced from the conversion of unmanaged forest into managed forest, from new fast growing short-rotation plantations, intensification, and optimization of land use.
Abstract: Preservation of biodiversity and reduction of deforestation are considered as key elements when addressing an increased use of bioenergy in the future. This paper presents different combinations of scenarios for global feedstock supply for the production of bioenergy under specified social and environmental safeguard provisions. The objectives of this study were threefold: a) to present a global perspective using an integrated modeling approach; b) to frame the boundaries for lower scale assessments; and c) to identify potential trade-offs to be considered in future research. The aggregate results, achieved through the application of an integrated global modeling cluster, indicate that under a high global demand for bioenergy by mid-century, biomass will to a large extent be sourced from the conversion of unmanaged forest into managed forest, from new fast-growing short-rotation plantations, intensification, and optimization of land use. Depending on the underlying scenario, zero net deforestation by 2020 could be reached and maintained with only a minor conversion of managed forests into other land cover types. Results further indicate that with rising populations and projected consumption levels, there will not be enough land to simultaneously conserve natural areas completely, halt forest loss, and switch to 100% renewable energy. Especially in the tropical regions of the southern hemisphere, it will be important to achieve a controlled conversion from unmanaged to sustainably managed forest as well as increased protection of areas for ecosystems services such as biodiversity. The study concludes with the recommendation to focus on targeted regional policy design and its implementation based on integrated global assessment modeling.
TL;DR: In this paper, the authors discuss the consequences of discontinuities in policy support using a case study approach and show that large, unexpected changes in policies increase uncertainty and may have a negative impact on investments.
Abstract: The renewable energy sector (RES) often receives financial, institutional or educational support from the government. A significant challenge for the actors in the RES field is policy consistency. When investments are carried out, a prognosis for future policies must be made. If the future is uncertain, larger risk margins should be included in the investment appraisals. Sudden, unexpected policy changes are one type of uncertainty that makes it more difficult to attract capital. In this article, we discuss the consequences of discontinuities in policy support using a case study approach. In Ontario, feed-in tariffs were introduced in 2009 and resulted in a large uptake in the programme. In 2010, the subsidies were drastically cut, resulting in the RES community losing confidence that the government would offer consistent support to the sector. In Norway, a large new biodiesel plant was opened by the Minister of the Environment only a few weeks before the government announced a major change in the bioenergy policy. As a result, the new plant was closed and restructured, and the investors lost nearly all of their investments. The government lost political credibility, making it difficult to raise private capital for new investments in this sector in Norway. We do not argue that policies should not be changed, but the manner in which policies are changed plays an important role. Our study shows that large, unexpected changes in policies increase uncertainty and may have a negative impact on investments. This topic should be further researched.
TL;DR: In this paper, the effects of torrefaction on the physiochemical properties of empty fruit bunches (EFB), palm mesocarp fiber (PMF), and palm kernel shell (PKS) are investigated.
Abstract: In this work, the effects of torrefaction on the physiochemical properties of empty fruit bunches (EFB), palm mesocarp fiber (PMF) and palm kernel shell (PKS) are investigated. The change of properties of these biomass residues such as CHNS mass fraction, gross calorific value (GCV), mass and energy yields and surface structure when subjected to torrefaction process are studied. In this work, these materials with particle size in the range of 355–500 μm are torrefied under light torrefaction conditions (200, 220 and 240 °C) and severe torrefaction conditions (260, 280 and 300 °C). TGA is used to monitor the mass loss during torrefaction while tube furnace is used to produce significant amount of products for chemical analyses. In general, the study reveals torrefaction process of palm oil biomass can be divided into two main stages through the observation on the mass loss distribution. The first stage is the dehydration process at the temperature below than 105 °C where the mass loss is in the range of 3–5%. In the second stage, the decomposition reaction takes place at temperature of 200–300 °C. Furthermore, the study reveals that carbon mass fraction and gross calorific value (GCV) increase with the increase of torrefaction temperature but the O/C ratio, hydrogen and oxygen mass fractions decrease for all biomass. Among the biomass, torrefied PKS has the highest carbon mass fraction of 55.6% when torrefied at 300 °C while PMF has the highest GCV of 23.73 MJ kg−1 when torrefied at the same temperature. Both EFB and PMF produce lower mass fraction than PKS when subjected to same torrefaction temperature. In terms of energy yield, PKS produces 86–92% yield when torrefied at light to severe torrefaction conditions, until 280 °C. However, both EFB and PMF only produce 70–78% yield at light torrefaction conditions, until 240 °C. Overall, the mass loss of 45–55% of these biomasses is observed when subjected to torrefaction process. Moreover, SEM images reveal that torrefaction has more severe impact on surface structure of EFB and PMF than that of PKS especially under severe torrefaction conditions. The study concludes that the torrefaction process of these biomass has to be optimized based on the type of the biomass in order to offset the mass loss of these materials through the process and increase the energy value of the solid product.
TL;DR: In this paper, the authors investigated the short run and long run causality analysis between biomass energy consumption and economic growth in selected 10 developing and emerging countries by using the Autoregressive Distributed Lag bounds testing (ARDL) approach of cointegration and error correction models.
Abstract: This paper investigates the short-run and long-run causality analysis between biomass energy consumption and economic growth in the selected 10 developing and emerging countries by using the Autoregressive Distributed Lag bounds testing (ARDL) approach of cointegration and error correction models. It covers annual data from 1980 to 2009. The cointegration test results show that there is cointegration between the biomass energy consumption and the economic growth in nine of the ten countries (Argentina, Bolivia, Cuba, Costa Rica, El Salvador, Jamaica, Nicaragua, Panama, Paraguay, Peru). The cointegration test results show that there is no cointegration between the biomass energy consumption and the economic growth in one of the ten countries (Paraguay).
TL;DR: In this article, the authors analyse the environmental performance of different biogas to electricity scenarios and identify two criticalities: the choice of feedstock and the operational practice concerning the digestate.
Abstract: Biogas production and use are generally regarded as a sustainable practice that can guarantee high greenhouse gas (GHG) savings. However, the actual carbon footprint of biogas is strongly influenced by several factors. The aim of this study is to analyse the environmental performance of different biogas to electricity scenarios. Two criticalities are identified as important: the choice of feedstock and the operational practice concerning the digestate. Maize, manure and co-digestion of them are the different feedstocks chosen. Maize has higher yields, but its cultivation has to be accounted for, which consists of 28–42% of the GHG emissions of the whole process of producing electricity. Manure is considered a residue and as a result benefits from no production stage, but also from avoided emissions from the normal agricultural practice of storing it in the farm and spreading it as fertiliser, but has lower methane yields. Co-digestion combines the benefits and disadvantages of the two different feedstocks. Digestate storage in open or closed tanks and further use as fertiliser is analysed. The environmental impact analysis shows that a substantial reduction of GHG emissions can be achieved with closed digestate storage. The GHG emissions savings vary from about 3% in the maize pathways with open storage up to 330% in the manure pathway with closed storage. The biogas pathways, though, have worse environmental performances in all other environmental impacts considered but ozone depletion potential when compared to the European electricity average mix.
TL;DR: In this article, the effect of co-gasification studies of coal and biomass and the effects of biomass and coal contents in the fuel blends is discussed. But, the authors focus mainly on co-gathering studies of different kinds of coal, biomass, and coal and their blends.
Abstract: This review deals mainly with co-gasification studies of different kinds of coal and biomass and the effect of biomass and coal contents in the fuel blends The percentage of biomass or coal in co-gasification is one of the most important parameters that affect the gasification process In this paper, the effect of gasifying various kinds of biomass, coal and their blends on the production of H 2 , CO 2 , CO, CH 4 and other hydrocarbons is reviewed In addition, other characteristics of the co-gasification process such as carbon conversion, gas yield, calorific value, cold gas efficiency, tar, H 2 S and NH 3 contents, which are influenced by changing the kinds and percentages of fuel in the mixture of coal and biomass is elaborated upon
TL;DR: In this article, Artificial Neural Networks (ANNs) have been applied for modeling biomass gasification process in fluidized bed reactors, and two architectures of ANNs models are presented; one for circulating fluidised bed gasifiers (CFB) and the other for bubbling fluidized-bed gasifier (BFB) for determining the producer gas composition (CO, CO2, H2, CH4) and gas yield.
Abstract: Artificial neural networks (ANNs) have been applied for modeling biomass gasification process in fluidized bed reactors. Two architectures of ANNs models are presented; one for circulating fluidized bed gasifiers (CFB) and the other for bubbling fluidized bed gasifiers (BFB). Both models determine the producer gas composition (CO, CO2, H2, CH4) and gas yield. Published experimental data from other authors has been used to train the ANNs. The obtained results show that the percentage composition of the main four gas species in producer gas (CO, CO2, H2, CH4) and producer gas yield for a biomass fluidized bed gasifier can be successfully predicted by applying neural networks. ANNs models use in the input layer the biomass composition and few operating parameters, two neurons in the hidden layer and the backpropagation algorithm. The results obtained by these ANNs show high agreement with published experimental data used R2 > 0.98. Furthermore a sensitivity analysis has been applied in each ANN model showing that all studied input variables are important.
TL;DR: In this paper, the physicochemical properties of digestates and derivatives are characterized in order to identify the fertilizer value and potential bottlenecks for agricultural re-use of these products, in line with European legislative constraints.
Abstract: In the transition from a fossil to a bio-based economy, it has become an important challenge to maximally recuperate valuable nutrients coming from waste streams. Nutrient resources are rapidly depleting, significant amounts of fossil energy are used for the production of chemical fertilizers, whereas costs for energy and fertilizers are increasing. In the meantime, biogas production through anaerobic digestion produces nutrient-rich digestates. In high-nutrient regions, these products cannot or only sparingly be returned to agricultural land in its crude unprocessed form. The consequent processing of this digestate requires a variety of technologies producing lots of different derivatives, which could potentially be re-used as green fertilizers in agriculture. As such, a sustainable alternative for fossil-based mineral fertilizers could be provided. This study aims to characterize the physico-chemical properties of digestates and derivatives, in order to identify the fertilizer value and potential bottlenecks for agricultural re-use of these products, in line with European legislative constraints. In addition, the economic and ecological benefits of substituting conventional fertilizers by bio-based alternatives are quantified and evaluated. Waste water from acidic air scrubbers for ammonia removal shows potential for application as N-S fertilizer. Analogously, concentrates resulting from membrane filtrated liquid fraction of digestate show promise as N-K fertilizer. Substituting conventional fertilizers by digestate derivatives in different cultivation scenarios can result in significant economic and ecological benefits for the agriculturist. Starting from theoretical scenarios outlined in the current study, field test validation will be required to confirm the potential substitution of fossil-based mineral fertilizers by bio-based alternatives.