This article is an up-to-date review of the literature available on the subject of liquid biofuels. In search of a suitable fuel alternative to fast depleting fossil fuel and oil reserves and in ...serious consideration of the environmental issues associated with the extensive use of fuels based on petrochemicals, research work is in progress worldwide. Researchers have been re-directing their interests in biomass based fuels, which currently seem to be the only logical alternative for sustainable development in the context of economical and environmental considerations. Renewable bioresources are available globally in the form of residual agricultural biomass and wastes, which can be transformed into liquid biofuels. However, the process of conversion, or chemical transformation, could be very expensive and not worth-while to use for an economical large-scale commercial supply of biofuels. Hence, there is still need for much research to be done for an effective, economical and efficient conversion process. Therefore, this article is written as a broad overview of the subject, and includes information based on the research conducted globally by scientists according to their local socio-cultural and economic situations.
This study evaluated the effectiveness of technology-push and market-pull policies in encouraging the production and use of biofuels in 15 countries including major biofuels producers. Biofuels ...production and consumption data for the 12-year period of 2006-2017 showed that in most of the surveyed countries, biofuels policies played an important role in developing and growing regional and national biofuels markets. Blending mandates continue to be the main market-pull policy used to create and expand biofuels markets. Countries with a mixture of market-pull and technology-push policy instruments have been most successful at increasing biofuels production and use and also developing and deploying less mature advanced biofuels. Most policies have primarily promoted the production and use of biofuels for road transport with key long-distance transport sectors (aviation and shipping) drawing less policy attention despite being significant fuel consumers and carbon emitters. While many older policies were originally developed to promote energy security, more recent policies, such as low carbon fuel standard, have reduction in the carbon intensity of transportation fuels as a primary goal. While policies have been essential in promoting the on-going growth of biofuels, they have not been sufficient to drive the level of development needed to decarbonize the transport sector.
•Biofuels policies have played an important role in developing biofuel markets.•Combinations of demand-pull and technology-push policies has been most successful.•Policies have primarily promoted the production and use of road transport biofuels.•Biofuel blending mandates are the primary biofuels policies use by most countries.•There is a shift from blending mandates to carbon-intensity type biofuel policies.
► Thermophiles are potential candidates for efficient lignocellulose conversion. ► The limitations of existing lignocellulose conversion processes are discussed. ► Importance of thermostable enzymes ...to overcome limitations are discussed. ► Influence of high temperatures on lignocellulose conversion processes are discussed.
Second-generation feedstock, especially nonfood lignocellulosic biomass is a potential source for biofuel production. Cost-intensive physical, chemical, biological pretreatment operations and slow enzymatic hydrolysis make the overall process of lignocellulosic conversion into biofuels less economical than available fossil fuels. Lignocellulose conversions carried out at ⩽50°C have several limitations. Therefore, this review focuses on the importance of thermophilic bacteria and thermostable enzymes to overcome the limitations of existing lignocellulosic biomass conversion processes. The influence of high temperatures on various existing lignocellulose conversion processes and those that are under development, including separate hydrolysis and fermentation, simultaneous saccharification and fermentation, and extremophilic consolidated bioprocess are also discussed.
•This paper examines the economic and cost advantages of microalgae in greater depth.•This paper shows how policy is crucial to the biofuels industry's growth in a region.•The suggestions focus on ...protecting the supply and positive externalities of biofuels.
There is currently no sustainable reliance on liquid fossil fuels worldwide, which ensures that future fiscal, environmental and social stability requires alternative renewable sources of liquid fuel. In order to satisfy the worldwide demand for liquid fuel, microalgae production is needed on a commodity scale; however, there are significant challenges in ensuring that production is economical and durable. This paper aims to examine microalgae' economic and cost advantages in greater depth and evaluate how vital biofuel policy support is for microalgae. A systematic analysis outlined the obstacles facing traditional biofuels to achieve these targets and proposed microalgae biofuels' economic opportunities. Provided that the policy was a primary determinant of the biofuel industry's development, these economic studies' findings were then included in the debate on existing policy support for biofuels and biofuels' potential microalgae play an essential role in the policy background.
•Few pretreatment methods have been applied to microalgae, most of them in BMP tests.•Pretreatment were evaluated by biomass solubilization and methane yield increase.•Results are species-specific, ...but effects on cell structure are not well understood.•Research at pilot-scale is needed to evaluate the scalability of the technology.
Microalgae have been intensively studied as a source of biomass for replacing conventional fossil fuels in the last decade. The optimization of biomass production, harvesting and downstream processing is necessary for enabling its full-scale application. Regarding biofuels, biogas production is limited by the characteristics of microalgae, in particular the complex cell wall structure of most algae species. Therefore, pretreatment methods have been investigated for microalgae cell wall disruption and biomass solubilization before undergoing anaerobic digestion. This paper summarises the state of the art of different pretreatment techniques used for improving microalgae anaerobic biodegradability. Pretreatments were divided into 4 categories: (i) thermal; (ii) mechanical; (iii) chemical and (iv) biological methods. According to experimental results, all of them are effective at increasing biomass solubilization and methane yield, pretreatment effect being species dependent. Pilot-scale research is still missing and would help evaluating the feasibility of full-scale implementation.
Algal biofuels: Challenges and opportunities Leite, Gustavo B.; Abdelaziz, Ahmed E.M.; Hallenbeck, Patrick C.
Bioresource technology,
10/2013, Volume:
145
Journal Article, Conference Proceeding
Peer reviewed
Open access
► Algae are promising for biofuels production. ► Higher productivity and lipid content than plants. ► Open ponds are better than PBRs for biofuels. ► Technical hurdles include harvesting and oil ...extraction.
Biodiesel production using microalgae is attractive in a number of respects. Here a number of pros and cons to using microalgae for biofuels production are reviewed. Algal cultivation can be carried out using non-arable land and non-potable water with simple nutrient supply. In addition, algal biomass productivities are much higher than those of vascular plants and the extractable content of lipids that can be usefully converted to biodiesel, triacylglycerols (TAGs) can be much higher than that of the oil seeds now used for first generation biodiesel. On the other hand, practical, cost-effective production of biofuels from microalgae requires that a number of obstacles be overcome. These include the development of low-cost, effective growth systems, efficient and energy saving harvesting techniques, and methods for oil extraction and conversion that are environmentally benign and cost-effective. Promising recent advances in these areas are highlighted.
The shift from straw incorporation to biofuel production entails emissions from production, changes in soil organic carbon (SOC) and through the provision of (co‐)products and entailed displacement ...effects. This paper analyses changes in greenhouse gas (GHG) emissions arising from the shift from straw incorporation to biomethane and bioethanol production. The biomethane concept comprises comminution, anaerobic digestion and amine washing. It additionally provides an organic fertilizer. Bioethanol production comprises energetic use of lignin, steam explosion, enzymatic hydrolysis and co‐fermentation. Additionally, feed is provided. A detailed consequential GHG balance with in‐depth focus on the time dependency of emissions is conducted: (a) the change in the atmospheric load of emissions arising from the change in the temporal occurrence of emissions comparing two steady states (before the shift and once a new steady state has established); and (b) the annual change in overall emissions over time starting from the shift are assessed. The shift from straw incorporation to biomethane production results in net changes in GHG emissions of (a) −979 (−436 to −1,654) and (b) −955 (−220 to −1,623) kg CO2‐eq. per tdry matter straw converted to biomethane (minimum and maximum). The shift to bioethanol production results in net changes of (a) −409 (−107 to −610) and (b) −361 (57 to −603) kg CO2‐eq. per tdry matter straw converted to bioethanol. If the atmospheric load of emissions arising from different timing of emissions is neglected in case (a), the change in GHG emissions differs by up to 54%. Case (b) reveals carbon payback times of 0 (0–49) and 19 (1–100) years in case of biomethane and bioethanol production, respectively. These results demonstrate that the detailed inclusion of temporal aspects into GHG balances is required to get a comprehensive understanding of changes in GHG emissions induced by the introduction of advanced biofuels from agricultural residues.
The article evaluates changes in greenhouse gas (GHG) emissions arising from a shift from straw incorporation into agricultural soil to advanced biofuel production. The focus of the evaluation is set on the change in the temporal occurrence of emissions. The study shows that the provision of organic material can contribute to soil organic carbon formation and thereby increase net reductions in GHG emissions.
Industrial and municipal wastewaters are potential resources for production of microalgae biofuels. Dalton – the Carpet Capital of the World generates 100–115
million
L of wastewater
d
−1. A study ...was conducted using a wastewater containing 85–90% carpet industry effluents with 10–15% municipal sewage, to evaluate the feasibility of algal biomass and biodiesel production. Native algal strains were isolated from carpet wastewater. Preliminary growth studies indicated both fresh water and marine algae showed good growth in wastewaters. A consortium of 15 native algal isolates showed >96% nutrient removal in treated wastewater. Biomass production potential and lipid content of this consortium cultivated in treated wastewater were ∼9.2–17.8
tons
ha
−1
year
−1 and 6.82%, respectively. About 63.9% of algal oil obtained from the consortium could be converted into biodiesel. However further studies on anaerobic digestion and thermochemical liquefaction are required to make this consortium approach economically viable for producing algae biofuels.
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