Green-filamentous macroalgae Chaetomorpha cf. gracilis from Cuban wetlands as a feedstock to produce alternative fuel: A physicochemical characterization

The excessive blooming of green filamentous macroalgae is a global problem due to their unwanted presence in freshwater, lakes, nursery garden and stagnant waters. An attractive solution is to use macroalgae as a biofuel feedstock. In this work, the macroalgae studied was the Chaetomorpha cf. gracilis. The macroalgae oil extraction was accomplished using Soxhlet method obtaining a yield of 1.85%. The gas chromatography analysis showed higher unsaturated fatty acids (56.14%) compared to saturated fatty acids (35.18%), highlighting the content of oleic acid, 27.89%. The kinematic viscosity and density were 0.826 mm²/s and 699.6 kg/m³, respectively. The heating value, crystallization temperature and elemental composition showed higher values than other algae oils. Nevertheless, the nitrogen content was similar to L.digitata macroalgae. The analysis conducted on the net energy ratio for the oil extraction process showed that the Chaetomorpha macroalgae oil might represent an attractive alternative for liquid biofuel production.     

Resource demand implications for US algae biofuels production scale-up

Photosynthetic microalgae with the potential for high biomass and oil productivities have long been viewed as a promising class of feedstock for biofuels to displace petroleum-based transportation fuels. Algae offer the additional benefits of potentially being produced without using high-value arable land and fresh water, thereby reducing the competition for those resources between expanding biofuels production and conventional agriculture. Algae growth can also be enhanced by the use of supplemental CO₂ that could be supplied by redirecting concentrated CO₂ emissions from stationary industrial sources such as fossil-fired power plants, cement plants, fermentation industries, and others. In this way, algae may offer an effective means to capture carbon emissions for reuse in renewable fuels and co-products, while at the same time displacing fossil carbon fuels to help bring about a net reduction in overall carbon emissions. Significant displacement of petroleum fuels will require that algae feedstock production reach large volumes that will put demands on key resources. This scenario-based analysis provides a high-level assessment of land, water, CO₂ and nutrient (nitrogen, phosphorus) demands resulting from algae biofuel feedstock production reaching target levels of 10 billion gallons per year (BGY), 20 BGY, 50 BGY, and 100 BGY for four different geographical regions of the United States. Different algae productivities are assumed for each scenario region, where relative productivities are nominally based on annual average solar insolation. The projected resource demands are compared with data that provide an indication of the resource level potentially available in each of the scenario regions. The results suggest that significant resource supply challenges can be expected to emerge as regional algae biofuel production capacity approaches levels of about 10 BGY. The details depend on the geographic region, the target feedstock production volume, and the level of algae productivity that can be achieved. The implications are that the supply of CO₂, nutrients, and water, in particular, can be expected to severely limit the extent to which US production of algae biofuel can be sustainably expanded unless approaches are developed to mitigate these resource constraints in parallel to emergence of a viable algae technology. Land requirements appear to be the least restrictive, particularly in the Western half of the country where larger quantities of potentially suitable classes of land exist. Within the limited scope and assumptions of this analysis, sustainable photosynthetic microalgae biofuel feedstock production in the US in excess of about 10 BGY will likely be a challenge due to other water, CO₂ and nutrient resource limitations. Developing algae production approaches that can effectively use non-fresh water resources and minimize both water and nutrient requirements will help reduce resource constraints. Providing adequate CO₂ resources for enhanced algae production appears the biggest challenge, and could emerge as a constraint at oil production levels below 10 BGY.     

Palm-based biofuel refinery (PBR) to substitute petroleum refinery: An energy and emergy assessment

As the most active palm industry cluster in the world, Malaysia produces enormous amount of biomass from the industry. This work studies the possibility of creating a renewable and sustainable source of energy by fully utilizing an area of land to provide liquid biofuel for the country. Palm-based biofuel refinery (PBR) proposed in this study has the ultimate goal to displace petroleum fuels and fulfill domestic energy demand. It fully utilizes indigenous palm biomass to fulfill 35.5% of energy demand in the country by using land area of only 8% of current palm cultivation. The operation concept of PBR is similar to petroleum refinery in which a single source feedstock (crude petroleum) can be processed to multiple products. In PBR, products from an oil palm plantation will be converted to various biofuel end products. Renewable biofuel such as biodiesel and bioethanol can be produced from crude palm oil and lignocellulosic residues. Energy and emergy assessment were made in this work to evaluate the sustainability and efficiency of PBR. Biofuel produced from PBR has a high energy equivalent of 31.56 MJ/kg as 1 ha of land can produce 182,142 MJ annually. Although there are still obstacles to be overcome, it is important for Malaysia to develop its own energy supply from indigenous resources as an initiative not only for security but also lower carbon emission.     

Net energy balance of small-scale on-farm biodiesel production from canola and soybean

One necessary criterion for a biofuel to be a sustainable alternative to the petroleum fuels it displaces is a positive net energy balance. This study estimated the net energy ratio (NER), net energy balance (NEB), and net energy yield (NEY) of small-scale on-farm production of canola [Brassica napus (L.)] and soybean [Glycine max (L.)] biodiesel in the upper Midwest. Direct and embodied energy inputs based on well-defined system boundaries and contemporary data were used to estimate the energy requirement of crop production, oil extraction, and biofuel processing. The NER of canola biodiesel was 1.78 compared with 2.05 for soybean biodiesel. Canola biodiesel had a NEB of 0.66 MJ MJ⁻¹ of biofuel compared with 0.81 MJ MJ⁻¹ for soybean biodiesel. The NEY of soybean biodiesel was 10,951 MJ ha⁻¹, less than canola biodiesel which had a NEY of 11,353 MJ ha⁻¹. Use of soybean as a biodiesel feedstock was more energetically efficient than canola primarily due to reduced nitrogen fertilizer requirement. In terms of energetic productivity, canola was a more productive biodiesel feedstock than soybean due to its higher oil content. A best-case scenario based on optimal feedstock yields, reduced fertilizer input, and advanced biofuel processing equipment suggested that potential gains in energetic efficiency was greater for canola than soybean. According to our results, small-scale on-farm biodiesel production using canola and soybean can be an energetically efficient way to produce energy for on-farm use.     

Cob biomass supply for combined heat and power and biofuel in the north central USA

Corn (Zea mays L.) cobs are being evaluated as a potential bioenergy feedstock for combined heat and power generation (CHP) and conversion into a biofuel. The objective of this study was to determine corn cob availability in north central United States (Minnesota, North Dakota, and South Dakota) using existing corn grain ethanol plants as a proxy for possible future co-located cellulosic ethanol plants. Cob production estimates averaged 6.04 Tg and 8.87 Tg using a 40 km radius area and 80 km radius area, respectively, from existing corn grain ethanol plants. The use of CHP from cobs reduces overall GHG emissions by 60%–65% from existing dry mill ethanol plants. An integrated biorefinery further reduces corn grain ethanol GHG emissions with estimated ranges from 13.9 g CO₂ equiv MJ⁻¹ to 17.4 g CO₂ equiv MJ⁻¹. Significant radius area overlap (53% overlap for 40 km radius and 86% overlap for 80 km radius) exists for cob availability between current corn grain ethanol plants in this region suggesting possible cob supply constraints for a mature biofuel industry. A multi-feedstock approach will likely be required to meet multiple end user renewable energy requirements for the north central United States. Economic and feedstock logistics models need to account for possible supply constraints under a mature biofuel industry.     

Effect of cosolvent and addition of catalyst (HZSM‐5) on hydrothermal liquefaction of macroalgae

The present study aimed to evaluate the effect of the direct liquefaction of macroalgae in an autoclave reactor (50 mL) possessing water and ethanol as cosolvent. The reaction conditions such as duration, temperature, algae/solvent ratio, the composition of cosolvent (ethanol‐water) on product distribution, and bio‐oil characterization were studied. The optimum conditions such as 300°C of temperature, 45 minutes of reaction time, 75% of ethanol, and algae to solvent ratio of 4/40 g/mL supported the bio‐oil yield of 46.75% with a conversion rate of 95.5%. The composition and concentration of the compounds in the bio‐oil produced under various doses of catalyst were described using GC‐MS. The bio‐oil characterization showed that the esters were most predominant in hydrothermal liquefaction with a catalyst (HZSM‐5) compared with hydrothermal liquefaction in the absence of the catalyst.     

Conversion of microalgae to biofuel

This paper primarily presents an overall review of the use of microalgae as a biofuel feedstock. Among the microalgae that have potential as biofuel feedstock, Chlorella, specifically, was thoroughly discussed because of its ability to adapt both to heterotrophic and phototrophic culture conditions. The lipid content and biomass productivity of microalgae can be up to 80% and 7.3 g/l/d based on the dried weight of biomass, respectively, making microalgae an ideal candidate as a biofuel feedstock. The set-up of the system and the biomass productivity of microalgae cultivated in an open pond and a photobioreactor were also compared in this work. The effect of the culture condition is discussed based on the two-stage culture period. The issues that were discussed include the light condition and the CO₂, DO and N supply. The microalgal productivities under heterotrophic and phototrophic culture conditions were also compared and highlighted in this work. The harvesting process and type of flocculants used to aid the harvesting were highlighted by considering the final yield of biomass. A new idea regarding how to harvest microalgae based on positive and negative charges was also proposed in this work. The extraction methods and solvents discussed were primarily for the conventional and newly invented techniques. Conversion processes such as transesterification and thermochemical processes were discussed, sketched in figures and summarized in tables. The cost–benefit analysis of heterotrophic culture and the cultivation system was highlighted at the end of this work. Other benefits of microalgae are also mentioned in this work to give further support for the use of microalgae as a feedstock for biofuel production.     

Valorization of hydrothermal liquefaction aqueous phase: pathways towards commercial viability

Hydrothermal liquefaction (HTL) is a thermochemical conversion technology that shows promising commercial potential for the production of biocrude oil from wet biomass. However, the inevitable production of the hydrothermal liquefaction aqueous phase (HTL-AP) acts as a double-edged sword: it is considered a waste stream that without additional treatment clouds the future scale-up prospects of HTL technology; on the other hand, it also offers potential as an untapped nutrient and energy resource that could be valorized. As more researchers turn to liquefaction as a means of producing renewable fuel, there is a growing need to better understand HTL-AP from a variety of vantage points. Specifically, the HTL-AP chemical composition, conversion pathways, energy valorization potential, and the interconnection of HTL-AP conversion with biofuel production technology are particularly worthy of investigation. This paper extensively reviews the impact of HTL conditions and the feedstock composition on the energy and elemental distribution of process outputs with specific emphasis on the HTL-AP. Moreover, this paper also compares and contrasts the current state of value-added products separation along with biological (biomass cultivation, anaerobic fermentation, and bioelectrochemical systems) and thermochemical (gasification and HTL) pathways to valorize HTL-AP. Furthermore, life cycle analysis (LCA) and techno-economic assessments (TEA) are performed to appraise the environmental sustainability and economic implications of these different valorization techniques. Finally, perspectives and challenges are presented and the integration approaches of HTL-AP valorization pathways with HTL and biorefining are explored.     

Energy and environmental sustainability assessment of a crude oil refinery by thermodynamic analysis

This study presents the assessment of energy and environmental sustainability metrics for a crude oil refinery consisting of three distillation columns. The assessments of the current operation and the retrofits for possible improvements are suggested by the thermodynamic analysis and energy analyzer. The main objective is to explore the scope of reducing the thermal energy consumption and CO₂ emissions for a more sustainable refinery operation. Thermodynamic analysis is carried out by using the thermal analysis capability of ‘column targeting tool’ to address the ‘energy intensity metrics’ and the ‘energy analyzer’ to design and improve the performance of the heat exchanger network system for process heat integration. Environmental pollution impact metrics are estimated from the ‘carbon tracking’ options with a selected CO₂ emission data source of US‐EPA‐Rule‐E9‐5711 and using crude oil as a primary fuel source for the hot utilities. The results indicate that column targeting tool, energy analyzer, and carbon tracking can estimate the energy and environmental sustainability metrics of an existing design and determine the scope of considerable improvements for reducing the costs of thermal energy required and emissions of carbon dioxide in a crude oil refinery operation. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Lifecycle assessment of the economic, environmental and energy performance of Jatropha curcas L. biodiesel in China

Due to issues relating to the sustainability of biofuel production, second generation biofuel has attracted much attention. As a promising feedstock of second generation biodiesel, Jatropha curcas L. (JCL) is being massively planted on marginal land in China, but its viability as a biofuel source has not been systematically assessed. This paper performed a lifecycle assessment of the economic, environmental and energy (3E) performance of the JCL biodiesel, assuming JCL oil is either used for direct blending with diesel or further processed into JCL methyl ester (JME). The results show that, at the current technical levels, the production of JCL biodiesel is financially infeasible, but has positive environmental and energy performance. Despite the additional cost incurred in the transesterification process, the net present value of JME is slightly higher than that of JCL oil when a part of the cost is allocated to the co-product, i.e., glycerin. As compared with that of diesel, the production and consumption of per liter JCL oil and JME can reduce 7.34 kg and 8.04 kg CO₂ equivalent, respectively. The energy balances of both JCL oil and JME are 1.57 and 1.47, respectively, in terms of the ratio of the heat value of biodiesel and that of energy input. The main factors affecting the 3E performance of JCL biodiesel are seed yield, co-product output, and farm energy input.     

Transesterification of marine macroalgae using microwave technology

Biodiesel is renewable and environmental friendly, with calori?c value equivalent to regular fossil fuel. This fuel can be produced from a variety of feedstocks, such as ?rst-generation biodiesel feedstock (corn, peanut, soybean), second generation (jatropha, animal fats, waste cooking oils, macroalgae), and third generation (microalgae). Among these feedstocks, biodiesel production from microalgae has drawn special attention for different reasons: they have high lipid content and high growth rates; they are tolerant to severe environmental conditions; they offer the possibility of sequester carbon dioxide from the ?ue gases; their harvesting and transportation are economical compared to other crops; and they have very high photosynthetic yields compared to other terrestrial plants. The advantage of using macroalgae recollected on the beaches as raw material is that allows to obtained energy from a residue.

Microwave-assisted extraction and transesteri?cation of microalgae is being researched as a solution for biodiesel production by its benefits, such as shorter reaction times and less amount of heat energy to obtain biodiesel. It is due to the fact that microwaves can easily penetrate through the cell wall structure to extract and transesterify the oils into biodiesel.

The aim of this research was to explore the possibility of carrying out the microwave-assisted transesterification of three marine macroalgae (brown and green). Different experimental runs were carried out with different process parameters such as macroalgae-to-methanol ratio, reaction time and catalyst concentrations. Based on the obtained results, the best conditions for microwave-assisted transesteri?cation reaction were macroalgae-to-methanol ratio of 1:15 (wt/vol), sodium hydroxide concentration of 2 wt% and reaction time of 3 min.     

利用微藻热化学液化制备生物油的研究进展

微藻是制备生物质液体燃料的良好材料,利用微藻热化学液化制备生物油在环保和能源供应方向都具有非常重要的意义。目前国内外研究者主要采用快速热解液化和直接液化两种热化学转化技术进行以微藻为原料制备生物油的研究。快速热解生产过程在常压下进行,工艺简单、成本低、反应迅速、燃料油收率高、装置容易大型化,是目前最具开发潜力的生物质液化技术之一。但快速热解需要对原料进行干燥和粉碎等预处理,微藻含水率极高,会消耗大量的能量,使快速热解技术在以微藻为原料制备生物油方面受到限制。直接液化技术反应温度较快速热解低,原料无需烘干和粉碎等高耗能预处理过程,且能产生更优质的生物油,将会是微藻热化学液化制备生物油发展的主流方向,极具工业化前景。国内外研究者还尝试利用超临界液化、共液化、热化学催化液化、微波裂解液化等多种新型液化工艺进行微藻热化学液化制备生物油的实验研究。今后的主要研究方向应是将热化学液化原理研究、生产工艺开发、反应器研发、反应条件优化、产品精制等有机地结合起来,进行深入研究。同时应努力节约成本、降低能耗。     

A Swedish integrated pulp and paper mill—Energy optimisation and local heat cooperation

Heat cooperation between industries and district heating companies is often economically and environmentally beneficial. In this paper, energy cooperation between an integrated Swedish pulp and paper mill and two nearby energy companies was analysed through economic optimisations. The synergies of cooperation were evaluated through optimisations with different system perspectives. Three changes of the energy system and combinations of them were analysed. The changes were process integration, extending biofuel boiler and turbine capacity and connection to a local heat market. The results show that the single most promising system change is extending biofuel and turbine capacity. Process integration within the pulp and paper mill would take place through installing evaporation units that yield less excess heat but must in this particular case be combined with extended biofuel combustion capacity in order to be beneficial. Connecting to the local heat market would be beneficial for the pulp and paper mill, while the studied energy company needs to extend its biofuel capacity in order to benefit from the local heat market. Furthermore, the potential of reducing CO₂ emissions through the energy cooperation is shown to be extensive; particularly if biofuel and turbine capacity is increased.     

Algae as a promising resource for biofuel industry: facts and challenges

Energy is the main driving force of society today that should be handled as a whole starting from production to consumption. With the rapid increase in the energy necessity, alternative methods and sources are becoming a crucial topic that should be scientifically highlighted with all their pros and cons. Especially the problems related to the fossil sources of energy triggered the search on the renewable alternatives like algae. In order to reach the desired amounts of energy with the satisfactory quality and quantity, understanding the algae as a living thing with the biological mechanism and existing production technologies are the key points to have a projection for commercialization. In this regard, technical facts and challenges on algal biofuel production should be evaluated. Keeping in mind the specifications and possible advantages related to their taxonomy, algae can serve as a promising source to reduce fossil fuel consumption. With the progress in the modern technology, reaching an effective production process will be possible, and this will help the algal biofuels to prove their maturity as a sustainable source for future. Within this context, the aim of this review is to point out the crucial technical challenges about algal fuels comprising both the macroalgae and microalgae as a reliable source of renewable energy. Copyright © 2016 John Wiley & Sons, Ltd.     

Improving inter-plant integration of syngas production technologies by the recycling of CO2 and by-product of the Fischer-Tropsch process

This paper deals with the emission reduction in synthesis-gas production by better integration and increasing the energy efficiency of a high-temperature co-electrolysis unit combined with the Fischer-Tropsch process. The investigated process utilises the by-product of Fischer-Tropsch, as an energy source and carbon dioxide as a feedstock for synthesis gas production. The proposed approach is based on adjusting process streams temperatures with the further synthesis of a new heat exchangers network and optimisation of the utility system. The potential of secondary energy resources was determined using plus/minus principles and simulation of a high-temperature co-electrolysis unit. The proposed technique maximises the economic and environmental benefits of inter-unit integration. Two scenarios were considered for sharing the high-temperature co-electrolysis and the Fischer-Tropsch process. In the first scenario, by-products from the Fischer-Tropsch process were used as fuel for a high-temperature co-electrolysis. Optimisation of secondary energy sources and the synthesis of a new heat exchanger network reduce fuel consumption by 47% and electricity by 11%. An additional environmental benefit is reflected in emission reduction by 25,145 tCO₂/y. The second scenario uses fossil fuel as a primary energy source. The new exchanger network for the high-temperature co-electrolysis was built for different energy sources. The use of natural gas resulted in total annual costs of the heat exchanger network to 1,388,034 USD/y, which is 1%, 14%, 116% less than for coal, fuel oil and LPG, respectively. The use of natural gas as a fuel has the lowest carbon footprint of 7288 tCO₂/y. On the other hand, coal as an energy source has commensurable economic indicators that produce 2 times more CO₂, which can be used as a feedstock for a high-temperature co-electrolysis. This work shows how in-depth preliminary analysis can optimise the use of primary and secondary energy resources during inter-plant integration.     

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.     

Potential alternatives of heat and power technology application using rice straw in Thailand

Rice straw could be used for heat and power with the current technologies available in Thailand. The cost of rice straw for power generation at 0.38–0.61 Baht/MJ_e (at rice straw price 930–1500 Baht/t) is not competitive with coal at 0.30 Baht/MJ_e but comparable with other biomass at 0.35–0.53 Baht/MJ_e. However, utilization of rice straw in industrial boilers is a more competitive and flexible option with two alternatives; (1) installing rice straw fired boilers instead of heavy oil fired or natural gas ones when selecting new boilers; and (2) fuel switching from coal to rice straw for existing boilers with cost saving of feedstock supply by 0.01 Baht/MJ_h. Based on its properties (Slagging index, R_s = 0.04; fouling index, R_f = 0.24), rice straw is not expected to have significant operating problems or different emissions compared with wheat straw and rice husk under similar operating conditions.     

Energy consumption and CO2 emissions of potato peel and sugarcane biohydrogen production pathways, applied to Portuguese road transportation

This paper analyses the energy consumption and CO₂ emissions of biological hydrogen production from sugarcane and potato peels using life cycle assessment methodology for the Portuguese scenario. Potato peels are assumed to be produced locally from Portuguese potato cultivation. Sugarcane is assumed to be imported from Brazil and fermented in Portugal. The uncertainty is quantified by a Monte Carlo approach. Biohydrogen was compared with natural gas reforming, electrolysis and other energy resources such as diesel and electricity. Between bioH₂ feedstocks, sugarcane stands out with the lowest values for energy consumption and CO₂ emissions with 0.30–0.34 MJ of consumed energy and 24–31 g of CO₂ emitted per 1 MJ of H₂ produced. However these results do not have a major contribution to the Portuguese energy independency problem. On the other hand potato peels feedstocks are more attractive, presenting values of 0.49–0.61 MJ/MJ_H2 and 60-77 gCO₂/MJ_H2. According to Portuguese production capabilities, it is estimated that biohydrogen will be able to supply 3100 vehicles of a typical Portuguese urban taxi fleet or up to 1.4 million passenger cars with a daily commuting distance of 30 km.     

Microalgal biomass production and carbon dioxide sequestration from an integrated ethanol biorefinery in Iowa: A technical appraisal and economic feasibility evaluation

Microalgae present some advantageous qualities for reducing carbon dioxide (CO₂) emissions from ethanol biorefineries. As photosynthetic organisms, microalgae utilize sunlight and CO₂ to generate biomass. By integrating large-scale microalgal cultivation with ethanol biorefineries, CO₂ sequestration can be coupled with the growth of algae, which can then be used as feedstock for biodiesel production. In this case study, a 50-mgy ethanol biorefinery in Iowa was evaluated as a candidate for this process. Theoretical projections for the amount of land needed to grow algae in raceway ponds and the oil yields of this operation were based on the amount of CO₂ from the ethanol plant. A practical algal productivity of 20 g m⁻² d⁻¹ would require over 2,000 acres of ponds for complete CO₂ abatement, but with an aggressive productivity of 40–60 g m⁻² d⁻¹, a significant portion of the CO₂ could be consumed using less than 1,000 acres. Due to the cold temperatures in Iowa, a greenhouse covering and a method to recover waste heat from the biorefinery were devised. While an algal strain, such as Chlorella vulgaris, would be able to withstand some temperature fluctuations, it was concluded that this process is limited by the amount of available heat, which could maintain only 41 acres at 73 °F. Additional heating requirements result in a cost of 10–40 USD per gallon of algal oil, which is prohibitively expensive for biodiesel production, but could be profitable with the incorporation of high-value algal coproducts.