•Algae biomass is a feasible feedstock for biofuels and bioproducts synthesis.•Algae biorefinery can optimise resources, maximize profits and minimize wastes.•Process development on algae-based ...biofuels and bioproducts were evaluated.•LCA is crucial in developing algae biorefinery.•Tailored design algae-based-biorefinery requires more intensive research.
Algae biomass comprises variety of biochemicals components such as carbohydrates, lipids and protein, which make them a feasible feedstock for biofuel production. However, high production cost mainly due to algae cultivation remains the main challenge in commercializing algae biofuels. Hence, extraction of other high value-added bioproducts from algae biomass is necessary to enhance the economic feasibility of algae biofuel production. This paper is aims to deliberate the recent developments of conventional technologies for algae biofuels production, such as biochemical and chemical conversion pathways, and extraction of a variety of bioproducts from algae biomass for various potential applications. Besides, life cycle evaluation studies on microalgae biorefinery are presented, focusing on case studies for various cultivation techniques, culture medium, harvesting, and dewatering techniques along with biofuel and bioenergy production pathways. Overall, the algae biorefinery provides new opportunities for valorisation of algae biomass for multiple products synthesis.
Culturing of microalgae as an alternative feedstock for biofuel production has received a lot of attention in recent years due to their fast growth rate and ability to accumulate high quantity of ...lipid and carbohydrate inside their cells for biodiesel and bioethanol production, respectively. In addition, this superior feedstock offers several environmental benefits, such as effective land utilization, CO2 sequestration, self-purification if coupled with wastewater treatment and does not trigger food versus fuel feud. Despite having all these ‘theoretical’ advantages, review on problems and issues related to energy balance in microalgae biofuel are not clearly addressed until now. Base on the maturity of current technology, the true potential of microalgae biofuel towards energy security and its feasibility for commercialization are still questionable. Thus, this review is aimed to depict the practical problems that are facing the microalgae biofuel industry, covering upstream to downstream activities by accessing the latest research reports and critical data analysis. Apart from that, several interlink solutions to the problems will be suggested with the purpose to bring current microalgae biofuel research into a new dimension and consequently, to revolutionize the entire microalgae biofuel industry towards long-term sustainability.
Derivation of biofuel from microalgae biomass has been widely researched in the past few decades. Microalgae is capable of producing 58,700 litres oil per hectare that can generate 121,104 litres ...biodiesel per hectare, which seemingly a promising transition over conventional fossil fuels. Nevertheless, economic sustainability of commercial scale production of microalgae biomass is still in shadows of doubt, especially the cultivation and harvesting process. Apparently, the microalgae cultivation system has evolved from traditional open pond to various modern photobioreactor (PBR) designs. However, with regards to tubular and flat panel PBRs as the most ubiquitous systems for biofuel production at commercial level, extensive discussion on reactor configurations and design betterment was presented in this review, along with precise technical comparison on cost and energy requirements for the cultivation systems. This review intended to serve as guideline for long term adoption of these well-established cultivation technologies in biofuel plants given the numerous economic benefits. Besides that, in attempt to lower the harvesting cost, potential use of various waste biomass as bioflocculants to recover microalgae biomass was introduced in this review. This article also deliberates direction on potential policy interventions to produce microalgae biofuel in a more sustainable and cost-effective manners in near future.
•Microalgae-derived biofuel is the potential substitute over fossil fuel.•Cultivation and harvesting steps are the bottlenecks to produce microalgae biofuel.•Wise selection of cultivation technology ensures sustainable biofuel production.•Bioflocculants from waste biomass are cheap, non-toxic, easily extracted.•Suitable policy framework ensures successful microalgae biofuel commercialization.
The third generation biofuels derived from oleaginous microorganisms have gained traction recently as the potential feedstock in generating fuel for energy production, reducing the direct dependence ...on fossil fuels. However, commercialization of microbial technology for biofuel production remains intricate and questionable due to many factors concerning the life cycle assessment and techno-economic feasibility of microorganisms-based biofuels. This review initially focuses on the nutritional aspects in enhancing the biomass and lipid yields from various microorganism feedstock, serving as impetuses for the production of third generation biofuels. Nutrient optimizations in terms of nutrient starvation, supplementation and balancing technique are discussed in relation to their respective effects on the microbial biomass and lipid productions. More importantly, the economic perspectives of oleaginous microorganism cultivations are also reviewed and strategized using alternative and non-conventional nutrient sources for possible technology scale-ups and commercialization.
In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel which can be ...easily produced through transesterification reaction. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, typically waste cooking oil can be a better alternative; however, the high free fatty acids (FFA) content in waste cooking oil has become the main drawback for this potential feedstock. Therefore, this review paper is aimed to give an overview on the current status of biodiesel production and the potential of waste cooking oil as an alternative feedstock. Advantages and limitations of using homogeneous, heterogeneous and enzymatic transesterification on oil with high FFA (mostly waste cooking oil) are discussed in detail. It was found that using heterogeneous acid catalyst and enzyme are the best option to produce biodiesel from oil with high FFA as compared to the current commercial homogeneous base-catalyzed process. However, these heterogeneous acid and enzyme catalyze system still suffers from serious mass transfer limitation problems and therefore are not favorable for industrial application. Nevertheless, towards the end of this review paper, a few latest technological developments that have the potential to overcome the mass transfer limitation problem such as oscillatory flow reactor (OFR), ultrasonication, microwave reactor and co-solvent are reviewed. With proper research focus and development, waste cooking oil can indeed become the next ideal feedstock for biodiesel.
•Microalgae biodiesel has high potential to replace fossil diesel.•Wastewater could serve as alternative nutrients source to cultivate microalgae.•Harvesting of microalgae is one of the obstacles to ...produce microalgae biodiesel.•Pre-treatment is required to enhance lipid extraction efficiency from microalgae.•Ozone bubble is a new method to harvest and pre-treat microalgae simultaneously.
Cultivation of microalgae using wastewater has received considerable attention around the globe as a platform to remove inorganic nutrients from the wastewater and producing microalgae biomass for biodiesel production. This can be done by converting freely available nutrients from the wastewater (particularly nitrogen, N and phosphorus, P) into microalgae biomass with concomitant carbon dioxide (CO2) sequestration via photosynthesis process. In fact, microalgae biodiesel could help to reduce greenhouse gas (GHG) emissions to the atmosphere through the replacement of fossil diesel as it is made from renewable resources. Despite the various benefits to produce microalgae biodiesel, a number of technical hurdles such as complex processes, requirement of high energy input during cultivation and dewatering (harvesting steps) need to be addressed for commercialization purpose. Besides, additional pre-treatment step is necessary to disrupt the microalgae cell wall to enhance lipid extraction efficiency. Hence, this paper is aims to reveal in-depth analysis and discussions on the process of microalgae-based wastewater treatment as well as microalgae cells disruption technology for lipid extraction. The paper also includes several new directions for technological improvements to improve commercialization potential of microalgae biodiesel.
Biofuels productions from microalgae received wide attention recently and have high potential to replace fossil fuels. This paper served as a platform to critically review current production ...technologies of microalgae, ranging from cultivation, harvesting, extraction and several biofuels conversion processes. In addition, due to the high photosynthetic efficiency of microalgae, mass cultivation of microalgae is believed to be able to efficiently reduce the carbon dioxide emission to atmosphere and thus, reducing the impact of global warming. This is because microalgae have high growth rate and is able to develop maximum of 70% of lipid content within their cells depending on species. Apart from that, microalgae have the ability to survive under harsh condition and occupied smaller cultivation land area than other land crops. The harvested microalgae biomass can be used for electrical generation, while its crude lipid can be used as transportation fuel as it has 80% average energy content of petroleum. In the present paper, a detailed discussion to produce biodiesel, fuel gas, bio-oil, methane, hydrogen and alcohol from microalgae biomass are also included. Besides, updated research, challenges and the way forward of microalgae biofuels are also presented. In future, biofuels production from microalgae can be economical viable at some scale, which is then profitable in terms of economics and also environment.
•Polyhydroxyalkanoates are biopolymers found in microalgae cell.•Novel technologies with additives improve the biopolymer mechanical properties.•Life cycle of biological composting have greenhouse ...gases credits.•Carbon sequestration of 1 kg algae biomass assimilates 1.83 kg atmospheric CO2.•Algae cultivation in photobioreactor does not require arable land.
The accumulation of conventional petroleum-based polymers has increased exponentially over the years. Therefore, algae-based biopolymer has gained interest among researchers as one of the alternative approaches in achieving a sustainable circular economy around the world. The benefits of microalgae biopolymer over other feedstock is its autotrophic complex to reduce the greenhouse gases emission, rapid growing ability with flexibility in diverse environments and its ability to compost that gives greenhouse gas credits. In contrast, this review provides a comprehensive understanding of algae-based biopolymer in the evaluation of microalgae strains, bioplastic characterization and bioplastic blending technologies. The future prospects and challenges on the algae circular bioeconomy which includes the challenges faced in circular economy, issues regard to the scale-up and operating cost of microalgae cultivation and the life cycle assessment on algal-based biopolymer were highlighted. The aim of this review is to provide insights of algae-based biopolymer towards a sustainable circular bioeconomy.
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•A novel bifunctional heterogenous SiC-NaOH/GO catalyst was successfully developed.•96% of yield of transesterification and 92% of yield of esterification were obtained in 6 min ...reaction time.•A high FAME conversion of 81% was obtained using SiC-NaOH/GO catalyst.
A novel heterogeneous bi-functional catalyst namely silicon carbide/sodium hydroxide-graphene oxide (SiC/NaOH-GO) was successfully developed and characterized using fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), scanning electron microscope (SEM), energy disperse X-ray analysis (EDX), Brunauer–Emmett–Teller analysis (BET), X-ray diffraction (XRD), carbon dioxide temperature programmed-desorption of carbon dioxide (CO2-TPD) and ammonia temperature programmed-desorption (NH3-TPD). The catalyst was applied in microwave-assisted transesterification and esterification of binary model feedstock (rapeseed oil and oleic acid) containing 20% free fatty acid (FFA) and optimized using respond surface methodology (RSM) based on centre composite design. The study revealed that the optimum reaction conditions were 13:1 wt ratio of SiC/NaOH to GO, 5 wt% of catalyst loading, reaction temperature of 65 °C and 6 min reaction time to attain 96% of yield of transesterification and 92% of yield of esterification. Then, the optimized catalyst (13:1 wt ratio of SiC/NaOH) was applied in Chlorella vulgaris lipid with high free fatty acid content (26%) to further confirmed the ability of converting triglycerides and free fatty acid (FFA) to biodiesel simultaneously. The study revealed that 92% of FFA of microalgae lipid was converted and 81% of fatty acid methyl ester content (FAME) was attained under the optimum conditions of methanol to lipid molar ratio of 48, 5 min reaction time, 4 wt% catalyst and reaction temperature of 85 °C.
Palm oil industry is one of the leading agricultural industries in Malaysia with average crude palm oil production of more than 13
million tonne per year. However, production of such huge amount of ...crude palm oil has consequently resulted to even larger amount of palm oil mill effluent (POME). POME is a highly polluting wastewater with high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in which can caused severe pollution to the environment, typically pollution to water resources. On the other hand, POME was identified as a potential source to generate renewable bioenergies such as biomethane and biohydrogen through anaerobic digestion. In other words, a combination of wastewater treatment and renewable bioenergies production would be an added advantage to the palm oil industry. In line with the world's focus on sustainability concept, such strategy should be implemented immediately to ensure palm oil is produced in an environmental friendly and sustainable manner. This review aims to discuss various technologies to convert POME to biomethane and biohydrogen in a commercial scale. Furthermore, discussion on using POME to culture microalgae for biodiesel and bioethanol production was included in the present paper as a new remedy to utilize POME with a greater beneficial return.
