Comparative LCA studies of simulated HMF biorefineries from maize and miscanthus as an example of first- and second-generation biomass as a tool for process development

5-Hydroxymethylfurfural (HMF) is a versatile platform chemical for a fossil free, bio-based chemical industry. HMF can be produced by using fructose as a feedstock. Using edible, first-generation biomass to produce chemicals has been questioned in terms of potential competition with food supply. Second-generation biomass like miscanthus could be an alternative. However, there is a lack of information if second-generation lignocellulosic biomass is a more sustainable feedstock to produce HMF. Therefore, a life cycle assessment was performed in this study to determine the environmental impacts of HMF production from miscanthus and to compare it with HMF from high-fructose corn syrup (HFCS). HFCS from either Hungary or Baden-Württemberg (Germany) was considered. Compared to the HFCS biorefineries the miscanthus concept is producing less emissions in all impact categories studied, except land occupation. Overall, the production and usage of second-generation biomass could be especially beneficial in areas where the use of N fertilizers is restricted. Besides, conclusions for the further development of the on-farm biorefinery concept were elaborated. For this purpose, process simulations from a previous study were used. Results of the previous study in terms of TEA and the current LCA study in terms of environmental sustainability indicate that the lignin depolymerization unit in the miscanthus biorefinery has to be improved. The scenario without lignin depolymerization performs better in all impact categories. The authors recommend to not further convert the lignin to products like phenol and other aromatic compounds. The results of the contribution analyses show that the major impact in the HMF production is caused by the auxiliary materials in the separation units and the required heat. Further technical development should focus on efficient heat as well as solvent use and solvent recovery. At this point further optimizations will lead to reduced emissions and costs at the same time.     

Integrating Separation and Conversion—Conversion of Biorefinery Process Streams to Biobased Chemicals and Fuels

The concept of the integrated biorefinery is critical to developing a robust biorefining industry in the USA. Within this model, the biorefinery will produce fuel as a high-volume output addressing domestic energy needs and biobased chemical products (high-value organics) as an output providing necessary economic support for fuel production. This paper will overview recent developments within two aspects of the integrated biorefinery—the fractionation of biomass into individual process streams and the subsequent conversion of lignin into chemical products. Solvent-based separation of switchgrass, poplar, and mixed feedstocks is being developed as a biorefinery “front end” and will be described as a function of fractionation conditions. Control over the properties and structure of the individual biomass components (carbohydrates and lignin) can be observed by adjusting the fractionation process. Subsequent conversion of the lignin isolated from this fractionation leads to low molecular weight aromatics from selective chemical oxidation. Together, processes such as these provide examples of foundational technology that will contribute to a robust domestic biorefining industry.     

An Olive Tree Pruning Biorefinery for Co-Producing High Value-Added Bioproducts and Biofuels: Economic and Energy Efficiency Analysis

This work presents a conceptual design of an integrated biorefinery using olive tree pruning as feedstock. The biorefinery combines a state-of-the-art thermochemical technology for producing high value-added antioxidants with an energy self-sufficient biochemical platform for lignocellulosic ethanol production. These plants are integrated by exchanging energy and feedstock. The process and design parameters employed in the plant designs are based on the authors’ own lab and pilot-scale data. The paper discusses the economic dilemma of using this feedstock for producing high value-added products in small amounts versus producing large amounts of low-profit biofuels. The feasibility of this production strategy at medium scale is demonstrated via a techno-economic analysis based on total production cost for each co-product. Each plant is energy integrated, and the energy performance of the bioethanol plant is assessed by calculating the end-use-energy ratio. Both analyses are parameterized with respect to plant capacity (100–1500 t dry weight (dw)/day) and raw material price (20–100 €/ton dry weight).     

Plant biotechnology for lignocellulosic biofuel production

Lignocelluloses from plant cell walls are attractive resources for sustainable biofuel production. However, conversion of lignocellulose to biofuel is more expensive than other current technologies, due to the costs of chemical pretreatment and enzyme hydrolysis for cell wall deconstruction. Recalcitrance of cell walls to deconstruction has been reduced in many plant species by modifying plant cell walls through biotechnology. These results have been achieved by reducing lignin content and altering its composition and structure. Reduction of recalcitrance has also been achieved by manipulating hemicellulose biosynthesis and by overexpression of bacterial enzymes in plants to disrupt linkages in the lignin–carbohydrate complexes. These modified plants often have improved saccharification yield and higher ethanol production. Cell wall‐degrading (CWD) enzymes from bacteria and fungi have been expressed at high levels in plants to increase the efficiency of saccharification compared with exogenous addition of cellulolytic enzymes. In planta expression of heat‐stable CWD enzymes from bacterial thermophiles has made autohydrolysis possible. Transgenic plants can be engineered to reduce recalcitrance without any yield penalty, indicating that successful cell wall modification can be achieved without impacting cell wall integrity or plant development. A more complete understanding of cell wall formation and structure should greatly improve lignocellulosic feedstocks and reduce the cost of biofuel production.     

Microalgal Biorefineries for Bioenergy Production: Can We Move from Concept to Industrial Reality?

Biorefineries are commercial facilities that transform raw materials into commodities of considerable interest to the world bioeconomy. In addition, biorefineries have the potential to achieve favorable environmental characteristics, such as minimal greenhouse gas (GHG) emissions and a lower water footprint, compared to homologous fossil fuels. However, for this concept to become efficient and viable, the use of potentially abundant and specific renewable biological feedstocks should be considered, such as microalgae biomass and other generated products. However, there is an emerging need to consolidate industrial plants that are not only affected by market fluctuations but also aim to transform biological materials into industrially usable products. Thus, for a microalgae biorefinery to compete with the resilient oil refineries in the future, process integration in the supply chain is a promising engineering approach, associating all the components from the cultivation to obtain multiple products that are economically and environmentally sustainable. Therefore, the objective of this review is to compile issues related to microalgal biorefineries applied to bioenergy and biofuel production.     

Catalytic processes towards the production of biofuels in a palm oil and oil palm biomass-based biorefinery

In Malaysia, there has been interest in the utilization of palm oil and oil palm biomass for the production of environmental friendly biofuels. A biorefinery based on palm oil and oil palm biomass for the production of biofuels has been proposed. The catalytic technology plays major role in the different processing stages in a biorefinery for the production of liquid as well as gaseous biofuels. There are number of challenges to find suitable catalytic technology to be used in a typical biorefinery. These challenges include (1) economic barriers, (2) catalysts that facilitate highly selective conversion of substrate to desired products and (3) the issues related to design, operation and control of catalytic reactor. Therefore, the catalytic technology is one of the critical factors that control the successful operation of biorefinery. There are number of catalytic processes in a biorefinery which convert the renewable feedstocks into the desired biofuels. These include biodiesel production from palm oil, catalytic cracking of palm oil for the production of biofuels, the production of hydrogen as well as syngas from biomass gasification, Fischer-Tropsch synthesis (FTS) for the conversion of syngas into liquid fuels and upgrading of liquid/gas fuels obtained from liquefaction/pyrolysis of biomass. The selection of catalysts for these processes is essential in determining the product distribution (olefins, paraffins and oxygenated products). The integration of catalytic technology with compatible separation processes is a key challenge for biorefinery operation from the economic point of view. This paper focuses on different types of catalysts and their role in the catalytic processes for the production of biofuels in a typical palm oil and oil palm biomass-based biorefinery.     

Comprehensive Compositional Analysis of Plant Cell Walls (Lignocellulosic biomass) Part I: Lignin

The need for renewable, carbon neutral, and sustainable raw materials for industry and society has become one of the most pressing issues for the 21st century. This has rekindled interest in the use of plant products as industrial raw materials for the production of liquid fuels for transportation¹ and other products such as biocomposite materials⁷. Plant biomass remains one of the greatest untapped reserves on the planet⁴. It is mostly comprised of cell walls that are composed of energy rich polymers including cellulose, various hemicelluloses (matrix polysaccharides, and the polyphenol lignin⁶ and thus sometimes termed lignocellulosics. However, plant cell walls have evolved to be recalcitrant to degradation as walls provide tensile strength to cells and the entire plants, ward off pathogens, and allow water to be transported throughout the plant; in the case of trees up to more the 100 m above ground level. Due to the various functions of walls, there is an immense structural diversity within the walls of different plant species and cell types within a single plant⁴. Hence, depending of what crop species, crop variety, or plant tissue is used for a biorefinery, the processing steps for depolymerization by chemical/enzymatic processes and subsequent fermentation of the various sugars to liquid biofuels need to be adjusted and optimized. This fact underpins the need for a thorough characterization of plant biomass feedstocks. Here we describe a comprehensive analytical methodology that enables the determination of the composition of lignocellulosics and is amenable to a medium to high-throughput analysis. In this first part we focus on the analysis of the polyphenol lignin (Figure 1). The method starts of with preparing destarched cell wall material. The resulting lignocellulosics are then split up to determine its lignin content by acetylbromide solubilization³, and its lignin composition in terms of its syringyl, guaiacyl- and p-hydroxyphenyl units⁵. The protocol for analyzing the carbohydrates in lignocellulosic biomass including cellulose content and matrix polysaccharide composition is discussed in Part II².     

草酸青霉的植物多糖降解酶基因表达调控的研究进展

植物生物质是地球上最丰富的可再生资源,对其生物炼制可生产高附加值的生物基产品。生物炼制需要使用植物多糖降解酶(plant-polysaccharide-degrading enzymes,PPDEs),如纤维素酶、木聚糖酶和生淀粉酶。丝状真菌草酸青霉(Penicillium oxalicum)能分泌完整的具有高活力的植物多糖降解酶,但其产量低限制了大规模生产及应用。草酸青霉中植物多糖降解酶的生物合成受到多种调控因子包括转录因子的严格调控。本文主要介绍在以植物生物质甘蔗渣和木薯生淀粉为原料的生物炼制中,涉及的一些关键微生物方面的问题,如从高产植物多糖降解酶的真菌菌株的筛选、育种,到草酸青霉植物多糖降解酶合成及其基因表达的调控基因的鉴定,以及酶产量提高的工程菌株的构建等,为丝状真菌资源的开发与利用提供理论指导。     

Financial Risk Assessment and Optimal Planning of Biofuels Supply Chains under Uncertainty

Biofuels provide an attractive alternative for satisfying energy demands in a more sustainable way than fossil fuels. To establish a biorefinery, an optimal plan must be implemented for the entire associated supply chain, covering such aspects as selection of feedstocks, location, and capacity of biorefineries, selection of processing technologies, production amounts and transportation flows. In this context, there are several parameters, including the availability of biomass, product demand, and product prices, which are difficult to predict because they might change drastically over the different seasons of the year as well as across years. To address this challenge, this work presents a mathematical programming model for the optimal planning of a distributed system of biorefineries that considers explicitly the uncertainty associated with the supply chain operation as well as the associated risk. The potential of the proposed approach is demonstrated through its application to the production of biofuels in Mexico, considering multiple raw materials and products.     

Comprehensive Compositional Analysis of Plant Cell Walls (Lignocellulosic biomass) Part II: Carbohydrates

The need for renewable, carbon neutral, and sustainable raw materials for industry and society has become one of the most pressing issues for the 21st century. This has rekindled interest in the use of plant products as industrial raw materials for the production of liquid fuels for transportation² and other products such as biocomposite materials⁶. Plant biomass remains one of the greatest untapped reserves on the planet⁴. It is mostly comprised of cell walls that are composed of energy rich polymers including cellulose, various hemicelluloses, and the polyphenol lignin⁵ and thus sometimes termed lignocellulosics. However, plant cell walls have evolved to be recalcitrant to degradation as walls contribute extensively to the strength and structural integrity of the entire plant. Despite its necessary rigidity, the cell wall is a highly dynamic entity that is metabolically active and plays crucial roles in numerous cell activities such as plant growth and differentiation⁵. Due to the various functions of walls, there is an immense structural diversity within the walls of different plant species and cell types within a single plant⁴. Hence, depending of what crop species, crop variety, or plant tissue is used for a biorefinery, the processing steps for depolymerisation by chemical/enzymatic processes and subsequent fermentation of the various sugars to liquid biofuels need to be adjusted and optimized. This fact underpins the need for a thorough characterization of plant biomass feedstocks. Here we describe a comprehensive analytical methodology that enables the determination of the composition of lignocellulosics and is amenable to a medium to high-throughput analysis (Figure 1). The method starts of with preparing destarched cell wall material. The resulting lignocellulosics are then split up to determine its monosaccharide composition of the hemicelluloses and other matrix polysaccharides1, and its content of crystalline cellulose⁷. The protocol for analyzing the lignin components in lignocellulosic biomass is discussed in Part I³.     

C_4 Plants as Biofuel Feedstocks: Optimising Biomass Production and Feedstock Quality from a Lignocellulosic Perspective

The main feedstocks for bioethanol are sugarcane (Saccharum officinarum) and maize (Zea mays),both of which are C4 grasses,highly efficient at converting solar energy into chemical energy,and both are food crops.As the systems for lignocellulosic bioethanol production become more efficient and cost effective,plant biomass from any source may be used as a feedstock for bioethanol production.Thus,a move away from using food plants to make fuel is possible,and sources of biomass such as wood from forestry and ...     

蓝细菌光驱固碳合成蔗糖技术的发展与展望

生物炼制技术体系是缓解能源和环境危机,推动社会可持续发展的重要选择,而充足的糖原料供应是生物炼制的基础。蓝细菌光驱固碳合成蔗糖是一种潜力巨大的新型糖原料供应路线。基于高效的蓝细菌光驱固碳细胞工厂,可以在单平台上以太阳能为驱动将二氧化碳和水直接转化为蔗糖,过程简单、产品明确、易于提取,而且可以同时达到固碳减排和供应糖原料的效果,具有重要的研究和应用价值。本文回顾了蓝细菌光驱固碳合成蔗糖技术的发展现状,从合成机制、代谢工程策略、技术延伸应用等层面对其最新进展和所遇到的问题进行了总结介绍,并对该技术未来发展方向进行了展望。     

Biorefinery Developments for Advanced Biofuels from a Sustainable Array of Biomass Feedstocks: Survey of Recent Biomass Conversion Research from Agricultural Research Service

When the USA passed the Renewable Fuel Standards (RFS) of 2007 into law, it mandated that, by the year 2022, 36 billion gallons of biofuels be produced annually in the USA to displace petroleum. This targeted quota, which required that at least half of domestic transportation fuel be “advanced biofuels” either produced from lignocellulosic feedstocks or be a sustainable liquid fuel other than corn ethanol or biodiesel from vegetable oils, will not likely be met due to the difficulty in commercializing alternative biofuels. The number one cost to a biorefinery is the biomass feedstock cost. Thus, it is important that research into biorefinery strategies be closely coupled to advances in crop science that account for crop yield and crop quality. To reach the RFS targets, stepwise progress in biorefinery technology is needed, as the industry moves from corn ethanol toward utilizing a wider array of lignocellulose-based biomass feedstocks. In 2010, the US Department of Agriculture created five Regional Biomass Research Centers to optimize production, collection, and conversion of crops to bioenergy, thus building a network that fosters collaboration among researchers to improve the biorefinery industry. An important component of the five Regional Biomass Research Centers is the four USDA Agricultural Research Service (ARS) regional utilization laboratories located across the country. These USDA ARS labs were originally set up by their commodities, whereby, in broad terms, the Northern Lab, now NCAUR, focused on corn and soy; the Eastern Lab on oils, leather, dairy, and meats; the Southern Lab on cotton, sugars, and fibers; and the Western Lab on other grains, including wheat and specialty crops. Each lab’s traditional expertise in these respective core commodity crops has been maintained as biofuel research came to the fore, but with the addition of new crops and biotechnological expertise, these labs often collaborate with each other, as will be revealed below. This review outlines some of the recent advances from the ARS labs in developing new bioprocessing strategies required to develop bioenergy from new crop sources.     

Terpenoid biomaterials

Terpenoids (isoprenoids) encompass more than 40 000 structures and form the largest class of all known plant metabolites. Some terpenoids have well-characterized physiological functions that are common to most plant species. In addition, many of the structurally diverse plant terpenoids may function in taxonomically more discrete, specialized interactions with other organisms. Historically, specialized terpenoids, together with alkaloids and many of the phenolics, have been referred to as secondary metabolites. More recently, these compounds have become widely recognized, conceptually and/or empirically, for their essential ecological functions in plant biology. Owing to their diverse biological activities and their diverse physical and chemical properties, terpenoid plant chemicals have been exploited by humans as traditional biomaterials in the form of complex mixtures or in the form of more or less pure compounds since ancient times. Plant terpenoids are widely used as industrially relevant chemicals, including many pharmaceuticals, flavours, fragrances, pesticides and disinfectants, and as large-volume feedstocks for chemical industries. Recently, there has been a renaissance of awareness of plant terpenoids as a valuable biological resource for societies that will have to become less reliant on petrochemicals. Harnessing the powers of plant and microbial systems for production of economically valuable plant terpenoids requires interdisciplinary and often expensive research into their chemistry, biosynthesis and genomics, as well as metabolic and biochemical engineering. This paper provides an overview of the formation of hemi-, mono-, sesqui- and diterpenoids in plants, and highlights some well-established examples for these classes of terpenoids in the context of biomaterials and biofuels.     

Bacterial acetone and butanol production by industrial fermentation in the Soviet Union: use of hydrolyzed agricultural waste for biorefinery

Clostridial acetone–butanol fermentation from renewable carbohydrates used to be the largest biotechnological process second only to yeast ethanol fermentation and the largest process ever run under sterile conditions. With the rising prices for mineral oil, it has now the economical and technological potential to replace petrochemistry for the production of fuels from renewable resources. Various methods for using non-food biomass such as cellulose and hemicellulose in agricultural products and wastes have been developed at laboratory scale. To our knowledge, the AB plants in Russia were the only full-scale industrial plants which used hydrolyzates of lignocellosic waste for butanol fermentation. These plants were further developed into the 1980s, and the process was finally run in a continual mode different from plants in Western countries. A biorefinery concept for the use of all by-products has been elaborated and was partially put into practice. The experience gained in the Soviet Union forms a promising basis for the development of modern large-scale processes to replace a considerable fraction of the current chemical production of fuel for our future needs on a sustainable basis.     

C4 plants as biofuel feedstocks: optimising biomass production and feedstock quality from a lignocellulosic perspective

The main feedstocks for bioethanol are sugarcane (Saccharum officinarum) and maize (Zea mays), both of which are C(4) grasses, highly efficient at converting solar energy into chemical energy, and both are food crops. As the systems for lignocellulosic bioethanol production become more efficient and cost effective, plant biomass from any source may be used as a feedstock for bioethanol production. Thus, a move away from using food plants to make fuel is possible, and sources of biomass such as wood from forestry and plant waste from cropping may be used. However, the bioethanol industry will need a continuous and reliable supply of biomass that can be produced at a low cost and with minimal use of water, fertilizer and arable land. As many C(4) plants have high light, water and nitrogen use efficiency, as compared with C(3) species, they are ideal as feedstock crops. We consider the productivity and resource use of a number of candidate plant species, and discuss biomass 'quality', that is, the composition of the plant cell wall.     

A sustainable woody biomass biorefinery

Woody biomass is renewable only if sustainable production is imposed. An optimum and sustainable biomass stand production rate is found to be one with the incremental growth rate at harvest equal to the average overall growth rate. Utilization of woody biomass leads to a sustainable economy. Woody biomass is comprised of at least four components: extractives, hemicellulose, lignin and cellulose. While extractives and hemicellulose are least resistant to chemical and thermal degradation, cellulose is most resistant to chemical, thermal, and biological attack. The difference or heterogeneity in reactivity leads to the recalcitrance of woody biomass at conversion. A selection of processes is presented together as a biorefinery based on incremental sequential deconstruction, fractionation/conversion of woody biomass to achieve efficient separation of major components. A preference is given to a biorefinery absent of pretreatment and detoxification process that produce waste byproducts. While numerous biorefinery approaches are known, a focused review on the integrated studies of water-based biorefinery processes is presented. Hot-water extraction is the first process step to extract value from woody biomass while improving the quality of the remaining solid material. This first step removes extractives and hemicellulose fractions from woody biomass. While extractives and hemicellulose are largely removed in the extraction liquor, cellulose and lignin largely remain in the residual woody structure. Xylo-oligomers, aromatics and acetic acid in the hardwood extract are the major components having the greatest potential value for development. Higher temperature and longer residence time lead to higher mass removal. While high temperature (>200°C) can lead to nearly total dissolution, the amount of sugars present in the extraction liquor decreases rapidly with temperature. Dilute acid hydrolysis of concentrated wood extracts renders the wood extract with monomeric sugars. At higher acid concentration and higher temperature the hydrolysis produced more xylose monomers in a comparatively shorter period of reaction time. Xylose is the most abundant monomeric sugar in the hydrolysate. The other comparatively small amounts of monomeric sugars include arabinose, glucose, rhamnose, mannose and galactose. Acetic acid, formic acid, furfural, HMF and other byproducts are inevitably generated during the acid hydrolysis process. Short reaction time is preferred for the hydrolysis of hot-water wood extracts. Acid hydrolysis presents a perfect opportunity for the removal or separation of aromatic materials from the wood extract/hydrolysate. The hot-water wood extract hydrolysate, after solid-removal, can be purified by Nano-membrane filtration to yield a fermentable sugar stream. Fermentation products such as ethanol can be produced from the sugar stream without a detoxification step.     

Optimizing Biomass Feedstock Blends with Respect to Cost,Supply, and Quality for Catalyzed and Uncatalyzed Fast Pyrolysis Applications

Biomass cost, supply, and quality are critical parameters to consider when choosing feedstocks and locations for biorefineries. Biomass cost is dependent upon feedstock type, location, quantities available, logistics costs, and the quality specifications required by the biorefinery. Biomass quality depends upon feedstock type, growth conditions, weather, harvesting methods, storage conditions, and any preprocessing methods used to improve quality. Biomass quantity depends on location as well as growth conditions, weather, harvesting methods, and storage conditions. This study examines the interdependencies of these parameters and how they affect the biomass blends required by biomass depots and/or biorefineries to achieve the lowest cost feedstock with sufficient quality at the quantities needed for biorefinery operation. Four biomass depots were proposed in South Carolina to each produce 200,000 t of feedstock per year. These depots supply a centrally located 800,000 t biorefinery that converts the feedstocks to bio-oil using either catalyzed or uncatalyzed fast pyrolysis. The four depots utilize biomass based upon availability, but the feedstock or feedstock blend still met the minimum quality requirements for the biorefinery. Costs were minimized by using waste biomass resources such as construction and demolition waste, logging residues, and forest residuals. As necessary, preprocessing methods such as air classification and acid leaching were used to upgrade biomass quality. For both uncatalyzed and catalyzed fast pyrolysis, all four depots could produce biomass blends that met quality and quantity specifications at a cost lower than using a single feedstock.     

Critical applications of Mucor circinelloides within a biorefinery context

The establishment of an efficient and feasible biorefinery model depends on, among other factors, particularly the selection of the most appropriate microorganism. Mucor circinelloides is a dimorphic fungus species able to produce a wide variety of hydrolytic enzymes, lipids prone to biodiesel production, carotenoids, ethanol, and biomass with significant nutritional value. M. circinelloides also has been selected as a model species for genetic modification by being the first filamentous oleaginous species to have its genome fully characterized, as well as being a species characterized as a potential bioremediation agent. Considering the potential of replacing several nonrenewable feedstocks is widely dependent on fossil fuels, the exploitation of microbial processes and products is a desirable solution for promoting a green and sustainable future. Here, we introduce and thoroughly describe the recent and critical applications of this remarkable fungus within the context of developing a fungal-based biorefinery.     

Sustainable production of eicosapentaenoic acid-rich oil from microalgae: Towards an algal biorefinery

Utilization of sustainable natural resources such as microalgae has been considered for the production of biofuels, aquaculture feed, high-value bioactives such as omega-3 fatty acids, carotenoids, etc. Eicosapentaenoic acid (EPA) is an omega-3 fatty acid present in fish oil, which is of physiological importance to both humans and fish. Marine microalgae are sustainable sources of lipid rich in EPA, and different species have been explored for the production of EPA as a single product. There has been a rising interest in the concept of a multi-product biorefinery, focusing on the maximum valorization of the algal biomass. Targeting one or more value-added compounds in a biorefinery scenario can improve the commercial viability of low-value products such as triglycerides for biofuel. This approach has been viewed by technologists and experts as a sustainable and economically feasible possibility for the large-scale production of microalgae for its potential applications in biodiesel and jet fuel production, nutraceuticals, animal and aquaculture feeds, etc. In this review paper, we describe the recent developments in the production of high-value EPA-rich oil from microalgae, emphasizing the upstream and downstream bioprocess techniques, and the advantages of considering an EPA-rich oil-based biorefinery.