Biofuel production: Prospects,challenges and feedstock in Australia

The growing demands for energy coupled with ever increasing environmental concerns have allowed the global production of biofuels to rise significantly in recent years. Many countries across the world have begun utilising biofuels on a national scale, while many more are in the process of planning and implementing similar steps. While Australia has an abundance of fossil fuels in the form of coal, natural gas, and oil, and currently employs a variety of alternative energy sources, the technology to produce and implement biofuels in Australia is in its embryonic stage. Today, Australia is using first generation feedstock as the main source for the production of biofuel, but is progressively broadening into second-generation biofuel production technology. Australia has an enormous amount of biomass available in the form of agricultural and forestry residues, bagasse and feedstock currently unused for the production of biofuels. The technology for the conversion of lignocellulosic biomass into biofuels warrants further research to maximise yield to the point of industrial feasibility. This review discusses the current state of ethanol production in Australia, the key technological challenges involved in the production of second-generation biofuel and the availability of various kinds of lignocellulosic biomass for biofuel production.     

Pretreatment of lignocellulosic biomass for enhanced biogas production

Lignocellulosic biomass is an abundant organic material that can be used for sustainable production of bioenergy and biofuels such as biogas (about 50–75% CH₄ and 25–50% CO₂). Out of all bioconversion technologies for biofuel and bioenergy production, anaerobic digestion (AD) is a most cost-effective bioconversion technology that has been implemented worldwide for commercial production of electricity, heat, and compressed natural gas (CNG) from organic materials. However, the utilization of lignocellulosic biomass for biogas production via anaerobic digestion has not been widely adopted because the complicated structure of the plant cell wall makes it resistant to microbial attack. Pretreatment of recalcitrant lignocellulosic biomass is essential to achieve high biogas yield in the AD process. A number of different pretreatment techniques involving physical, chemical, and biological approaches have been investigated over the past few decades, but there is no report that systematically compares the performance of these pretreatment methods for application on lignocellulosic biomass for biogas production. This paper reviews the methods that have been studied for pretreatment of lignocellulosic biomass for conversion to biogas. It describes the AD process, structural and compositional properties of lignocellulosic biomass, and various pretreatment techniques, including the pretreatment process, parameters, performance, and advantages vs. drawbacks. This paper concludes with the current status and future research perspectives of pretreatment.     

State of the art of biofuels from pure plant oil

The pollution caused by fuel combustion either for mechanical or electrical energy generation purposes is nowadays one of the most important environmental issues. It has been proven that combustion emissions, particularly those from cars and trucks, are linked with severe damages to the environment and human health. Along with the environmental problems, is necessary to consider that fossil resources are declining and their exploitation is getting more and more expensive. Bioenergy represent a sustainable solution for energy generation. Bioenergy is renewable energy made from plant-derived organic matter, collectively termed “biomass”. Biomass-based energy sources are potentially carbon dioxide neutral and recycle the same carbon atoms. Life cycle assessments are reported to evaluate the net environmental impacts of biofuels. The term biofuel refers to liquid or gaseous fuels for the internal combustion engines that are predominantly produced from biomass. Biofuel policy might capitalize on the production of biofuels supporting rural economic development and sustainable agriculture. Amongst biofuels pure plant oil (PPO) has been investigated. This paper sets out to review the state of the art for PPO use as fuel in diesel engines, based on a wide literature review.     

Trends and sustainability criteria of the production and use of liquid biofuels

Environmental impacts associated with the use of fossil fuels, rising prices, potential limitations in supply and concerns about regional and national security are driving the development and use of biomass for bioenergy, biofuels and bioproducts. However, the use of biomass does not automatically imply that its production, conversion and use are sustainable. Conflicts between various ecosystem services (economic production of food, fodder and fuels, biodiversity, social and cultural values, etc.) that are provided by fertile land are increasing as well. Hence, a developed thinking on how to balance between these services is desirable.There is a significant amount of information available on biofuels and their sustainability. In this paper, different initiatives and sustainability criteria for biofuels are presented and assessed.35 criteria were found in emerging sustainability assessment frameworks. The majority of 12 criteria were focused on environmental issues, 4 were social and only 1 was economic. Energy balance and greenhouse gas balance were perceived as especially critical, social criteria ranked generally low. Although being perceived as important, food security ranked very low.     

Towards sewage sludge based biofuels via thermochemical conversion – A review

Wastewater treatment leads to an increase in sewage sludge production. Sewage sludge consists, in general, of non-toxic organic matter and therefore can be utilized as a biomass resource for energy production. Energy recovery from sewage sludge via thermochemical valorization processes seems of great potential. Processes’ products can be used as bio-fuels, while minimization of the environmental impacts can be also achieved. In particular, wet sewage sludge pyrolysis-partial gasification at high temperatures and especially gasification give a new perspective for hydrogen-rich fuel gas production. Co-processing of sewage sludge with biomass improves the fuel's characteristics and enhances the processes efficiency. In addition, blends of sewage sludge with biomass contribute in diluting the inorganic and toxic compounds. Towards that direction, algae production using wastewater resources and then to be used for biofuels production seems a sustainable solution that is the reason why exploitation of such a material through thermochemical processes is under intensive discussion.     

An overview of algae bioethanol production

Because of rapid growth in population and industrialization, worldwide ethanol demand is increasing continuously. The first‐generation and second‐generation biofuels are unable to meet the global demand of bioethanol production because of their primary value of food and feed. Therefore, algae are among the most potentially significant sources of sustainable biofuels in the future of renewable energy because of the accumulating high starch/cellulose and because they are widely distributed in nature. The focus of this paper is to review the production and recent advances in research and development in the algae bioethanol, including pretreatment, hydrolysis, and fermentation of algae biomass. Despite the many developments made in the recent years, commercialization of algal bioethanol remains challenging chiefly because of the techno‐economic constraints. Technological breakthroughs in all major aspects must be overcome before it can be a successfully large‐scale and commercialized product. Copyright © 2014 John Wiley & Sons, Ltd.     

Fermentative hydrogen production - An alternative clean energy source

Hydrogen generation from wastewater is one of the promising approaches through biological route. So, exploitation of wastewater as substrate for hydrogen production with concurrent wastewater treatment is an attractive and effective way of tapping clean energy from renewable resources in a sustainable approach. In this direction, considerable interest is observed on various biological routes of hydrogen production using bio-photolysis, photo fermentation and heterotrophic dark fermentation process or by a combination of these processes. Therefore, in this communication, utilizing industrial wastewater as primary substrate for dark fermentation process is reviewed and different parametric aspects associated with this sustainable approach for better energy production is discussed. The industrial wastewaters that could be the source for bio hydrogen generation, such as rice slurry wastewater, food and domestic wastewaters, citric acid wastewater and paper mill wastewater, are also discussed in this article.     

Biofuels from microalgae—A review of technologies for production,processing, and extractions of biofuels and co-products

Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO₂, N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products.This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.     

Biofuel production: Challenges and opportunities

It is increasing clear that biofuels can be a viable source of renewable energy in contrast to the finite nature, geopolitical instability, and deleterious global effects of fossil fuel energy. Collectively, biofuels include any energy-enriched chemicals generated directly through the biological processes or derived from the chemical conversion from biomass of prior living organisms. Predominantly, biofuels are produced from photosynthetic organisms such as photosynthetic bacteria, micro- and macro-algae and vascular land plants. The primary products of biofuel may be in a gas, liquid, or solid form. These products can be further converted by biochemical, physical, and thermochemical methods. Biofuels can be classified into two categories: primary and secondary biofuels. The primary biofuels are directly produced from burning woody or cellulosic plant material and dry animal waste. The secondary biofuels can be classified into three generations that are each indirectly generated from plant and animal material. The first generation of biofuels is ethanol derived from food crops rich in starch or biodiesel taken from waste animal fats such as cooking grease. The second generation is bioethanol derived from non-food cellulosic biomass and biodiesel taken from oil-rich plant seed such as soybean or jatropha. The third generation is the biofuels generated from cyanobacterial, microalgae and other microbes, which is the most promising approach to meet the global energy demands. In this review, we present the recent progresses including challenges and opportunities in microbial biofuels production as well as the potential applications of microalgae as a platform of biomass production. Future research endeavors in biofuel production should be placed on the search of novel biofuel production species, optimization and improvement of culture conditions, genetic engineering of biofuel-producing species, complete understanding of the biofuel production mechanisms, and effective techniques for mass cultivation of microorganisms.     

A comprehensive review on lignocellulosic biomass biorefinery for sustainable biofuel production

The increasingly severe environmental pollution and energy shortage issues have demanded the production of renewable and sustainable biofuels to replace conventional fossil fuels. Lignocellulosic (LC) biomass as an abundant feedstock for second-generation biofuel production can help overcome the shortcomings of first-generation biofuels related to the “food versus fuel” debate and feedstock availability. Embracing the “circular bioeconomy” concept, an integrated biorefinery platform of LC biomass can be performed by employing different conversion technologies to obtain multiple valuable products. This review provides an overview of the principles and applications of thermochemical processes (pyrolysis, torrefaction, hydrothermal liquefaction, and gasification) and biochemical processes (pretreatment technologies, enzyme hydrolysis, biochemical conversion processes) involved in LC biomass biorefinery for potential biofuel applications. The engineering perspective of LC biofuel production on separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP) were also discussed.     

A critical review of biochemical conversion,sustainability and life cycle assessment of algal biofuels

The increasing global demand of biofuels for energy security and reduction in climate change effects generate the opportunity to explore new biomass sources. Algae is a very promising source of biomass in this context as it sequester a significant quantity of carbon from atmosphere and industrial gases and is also very efficient in utilizing the nutrients from industrial effluents and municipal wastewater. Therefore cultivation of algal biomass provide dual benefit, it provides biomass for the production of biofuels and also save our environment from air and water pollution. The life cycle assessment (LCA) of algal biofuels suggests them to be environmentally better than the fossil fuels but economically it is not yet so attractive.     

Are plants the new oil? Responsible innovation,biorefining and multipurpose agriculture

Bioenergy is seen as one of the options for industrialised countries to wean themselves off fossil fuels. However bioenergy, transport biofuels in particular, has faced considerable environmental and social controversies. Biorefining has been proposed in the UK and Denmark to address these concerns by using biomass efficiently for multiple purposes (food, feed, fuel, chemicals). Drawing from frameworks on responsible innovation, this paper opens up the implicit assumptions within the biorefinery concept about how biomass should be produced.Stakeholder interviews show that the biorefinery concept is framed within an industrial agricultural paradigm that aims to overcome controversies through large-scale production stimulated by biotechnology innovation. By contrast, an “alternative agriculture” paradigm envisions sustainable multipurpose biomass production in terms of on-farm nutrient and energy cycling and local, smaller scale production. However, there is a potential overlap through the concept of quality industrial biomass production. These three visions provide different perspectives on the bioeconomy in terms of the differences between biomass and fossil fuels; and where biomass should come from. Policy development for bioenergy must reckon with these different visions in innovation pathways for multipurpose biomass.     

Microalgae for biodiesel production and other applications: A review

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO₂, wastewater treatment, in human health, as food additive, and for aquaculture.     

Co-culture for lipid production: Advances and challenges

The exploration of microbial communities to efficiently produce biofuels has become a critical approach among biochemical processes. Co-cultures have been intensively studied to address the limitations in substrate utilization by individual strains for the production of other bioproducts. Accordingly, many concerns have arisen about the effects of this strategy on lipid productivity. Despite the extensive research on lipid production by oleaginous microorganisms, co-culture strategy has been only well-reviewed in algal species and most of the original research has been concentrated on the different nutritional growth modes (e.g. heterotrophic and mixotrophic). Moreover, current literature indicates scarce information on strategies for the improvement of lipid production with other species rather than microalgae. From a systematic perspective, this review will highlight co-culture systems existing for the improved biomass and lipid productivity, among other species. The review first discloses the current state of microalgal assemblies and their strategies for lipid production. Subsequently, it summarizes other assemblies aimed at lipid production. Finally, it discusses the relative advantages and disadvantages and the possibilities to overcome inherent challenges.     

Methane production from lignocellulosic agricultural crop wastes: A review in context to second generation of biofuel production

The aim of this paper is to present a comprehensive review on renewable methane fuel production through the biological route of biomethanation process from major lignocellulosic agricultural crop waste biomass (maize, wheat, rice and sugarcane). Global annual approximate production of major agriculture based lignocellulosic biomass has been explored. Fundamental requirements of biomethanation process have been discussed in details for optimum production of methane. The essential properties of biomass (proximate, ultimate and compositional) conscientious for quality of derived fuel have also been presented along with the pretreatment requirements for lignocellulosic biomass. Methane generation potential of the major lignocellulosic agricultural crop biomass has been explored and presented. Furthermore, the methane production potential and its energetic analysis have also been compared with the bio-ethanol productions. The overall parametric analysis involved in anaerobic digestion and alcoholic fermentation explore that methane generation from lignocellulosic agricultural crop waste biomass is more economical and environmentally beneficial way of biomass utilization in a sustainable way of energy production.     

Improvement potential for net energy balance of biodiesel derived from palm oil: A case study from Indonesian practice

Biodiesel derived from palm oil has been recognized as a high-productivity oil crop among the first generation of biofuels. This study evaluated and discussed the net energy balance for biodiesel in Indonesia by calculating the net energy ratio (NER) and net energy production (NEP) form the total energy input and output. The results of the calculation of energy input for the default scenario demonstrated that the primary energy inputs in the biodiesel production lifecycle were the methanol feedstock, energy input during the biodiesel production process, and urea production. These three items amounted to 85% of the total energy input. Next, we considered and evaluated ways to potentially improve the energy balance by utilizing by-products and biogas from wastewater treatment in the palm oil mill. This result emphasized the importance of utilizing the biomass residue and by-products. Finally, we discussed the need to be aware of energy balance issues between countries when biofuels are transported internationally.     

Value analysis for commercialization of fermentative hydrogen production from biomass

In addition to producing hydrogen gas, biohydrogen production is also used to process wastewater. Therefore, this study specifically conducted value analyses of two different scenarios of fermentative hydrogen production from a biomass system: to increase the value of a wastewater treatment system and to specifically carry out hydrogen production. The analytical results showed that fermentative hydrogen production from a biomass system would increase the value of a wastewater treatment system and make its commercialization more feasible. In contrast, fermentative hydrogen production from a biomass system designed specifically for producing hydrogen gas would have a lower system value, which indicated that it is not yet ready for commercialization. The main obstacle to be overcome in promoting biohydrogen production technology and system application is the lack of sales channels for the system's products such as hydrogen gas and electricity. Thus, in order to realize its commercialization, this paper suggests that governments provide investment subsidies for the use of biohydrogen production technology and establish a buy-back tariff system for fuel cells.     

Sustainable ethanol production from lignocellulosic biomass - Application of exergy analysis

The sustainability of the second-generation biofuels requests to confirm that the energy produced from lignocellulosic biomass is significantly greater than the energy consumed in the process. As lignocellulosic biomass does not affect the food supply, sugarcane bagasse was analyzed as a raw material for second-generation biofuels production. Exergy analysis serves as a unified and effective tool to evaluate the global process efficiency. Exergy analysis evaluates the performance of sugarcane bagasse and its sustainability in the bioethanol production process. In this work, four ethanol production topologies using the typical daily amount of residual biomass produced by the sugar industry were compared. The exergy analysis concept is effective in screening design alternatives with the lowest environmental impact for second-generation bioethanol fuel production from renewable resources. This study was executed by the use of the Aspen Plus^® program and other software developed by the authors.     

Land use competition for production of food and liquid biofuels: An analysis of the arguments in the current debate

This article analyses the current state of the debate over competition for land use, by means of an index of the main arguments in favor and against the production of liquid biofuels and the impacts on food production. Based on this index, an analytic framework is constructed to establish the causal relations indicated by the existing studies on this competition. We find that the emergence of agro-energy has altered the land use dynamic, albeit not yet significantly, with a shift of areas traditionally used to grow foods over to crops to produce biofuels. This has been contributing to raise food prices in the short run. However, it is probable that this is not the only factor determining this trend, nor will it last over the long run. The challenge is to conciliate the production of biofuels with the production of foods in sustainable form.     

Scenarios for biofuel demands,biomass production and land use – The case of Denmark

The land potential for producing biomass for bioenergy purposes has been highly debated in recent years. The present paper analyses the possibilities and consequences for land use and agricultural production of biofuel production in Denmark based on domestic wheat and rape under specific scenario conditions for the period 2010–2030. The potential is assessed for a situation where policy targets for renewable energy carriers in the transport sector is reached using biofuels, and where second generation ethanol increasingly substitutes first generation ethanol.Three scenarios are developed and evaluated: a baseline, an alternative scenario allowing continuous growth in the now dominant livestock branch and a biofuel scenario assuming that efforts to achieve self-sufficiency in biofuel displaces part of the domestic production of fodder.Results show that the biofuel demand could be met in 2020; but only if current rape oil production is used to satisfy local bio-diesel demand. It would also imply that the Danish bio-diesel export currently supplying a minor part of the German fuel market would seize. In 2030, however, only about 60 percent of the biofuel demand would be covered by self-sufficiency. If biofuels were to displace animal production to make up for this, a reduction of the pig production between 10 and 20 percent would result. Efficiency increases across production branches would allow the animal production to continue un-affected if about half of the rape oil produced for other purposes is utilized.