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Charcoal is a coconut derivative product produced from burning coconut shells. In this study, coconut shell charcoal was obtained from the by-product of copra processing. The processing of coconut shell charcoal produces emissions that pollute the environment, which are greenhouse gas (GHG) emissions equivalent to CO2-eq. Life cycle assessment (LCA) is a method that can assess the environmental impact of a product throughout its life cycle. Net energy calculation was carried out to determine the energy efficiency of charcoal production in the form of net energy value (NEV) and net energy ratio (NER). The LCA studied was gate-to-gate, namely from coconut shell transportation to processing into charcoal with emission function units per 1 kg of coconut shell charcoal product. The study was conducted at CV X, located in Sukabumi, West Java, Indonesia. The calculation results show that the raw material transportation stage produced 0.0626 kg CO2-eq/kg charcoal, while the pyrolysis stage produced 0.212 kg CO2-eq/kg charcoal. Energy efficiency analysis showed NEV 9,398.66 MJ and NER 1.09. Recommendations for improvement that can be given are to produce charcoal in one place with a copra factory and produce liquid smoke from the combustion of charcoal. Charcoal production in one factory with a copra factory could reduce the GHG impact by 48%, increase NEV to 12,823.19 MJ, and increase NER to 1.13. Utilization of smoke into liquid smoke increased NEV and NEV to 107,715.75 MJ and 2.03. Combining the two scenarios increased NEV and NER to 211,856.62 MJ and 2.10.

The conversion of biomass to bioenergy is one of the approaches to creating a sustainable society. In this study, the life cycle assessment and the net energy analysis of converting mixed sewage sludge and beverage waste into bioenergy via a combined hydrothermal liquefaction-anaerobic digestion (HTL-AD) system was carried out. Primary sludge (PS), winery rose lees (RL), brewery Trub (BT), the mixture of brewery trub and primary sludge (BTPS) and the mixture of winery rose lees and primary sludge (RLPS) were the feedstocks considered. Efficient energy utilization [in form of net energy ratio (NER)], and environmental emissions were evaluated. The NER of BT (2.07) and RL (1.76) increased when mixed with PS (3.18) to produce BTPS (3.20) and RLPS (2.85). Also, the HTL phase of the combined HTL-AD system produced a greater NER than the AD phase in BT, BTPS, and PS and vice-versa in RL and RLPS. Six environmental impact categories were studied namely global warming, terrestrial acidification, ionizing radiation, terrestrial ecotoxicity, human carcinogenic toxicity, and human non-carcinogenic toxicity. RL produced the greatest environmental impact while BTPS produced the least impact, thus indicating the advantage of feedstock combination. This study shows that the combination of feedstocks for bioenergy production in an HTL-AD system does not only increase the quality and quantity of products but also increases the overall NER as well as reducting the environmental impacts. The study also proved that an integrated HTL-AD system is an energy efficient system with greater resource utilization and less environmental footprint than the constituent systems. [Display omitted] • Mixed winery rose lees/brewery trub and sewage sludge generates bioproducts of higher net energy ratio. • Combined hydrothermal liquefaction and anaerobic digestion (HTL-AD) is an energy efficient and environmentally sustainable system. • In the integrated HTL-AD system, the HTL phase produced a higher net energy ratio than the AD phase. • BT (2.16) + PS (NER 3.53) = BTPS (3.35) and RL (1.38) + PS (3.53) = RLPS (2.09). • Global warming > human non-carcinogenic > terrestrial ecotoxicity > ionizing radiation > human carcinogenic > Terrestrial acidification. [ABSTRACT FROM AUTHOR]

This work implements a multi-objective scoring methodology based on fuzzy set theory to evaluate and compare the sustainability metrics of microalgal biorefining concepts. Fuzzy membership functions are developed for three key metrics: minimum fuel selling price, global warming potential, and net energy ratio. Membership functions yield satisfaction scores (λ) between 0 and 1 for each objective; achieving λ=1 indicates a sustainability metric has fully met its target, while λ=0 is unacceptable for the standards of that metric. The individual λ are combined into an overall satisfaction score, λo, also ranging from 0 to 1, which is used here to simplify the comparison of sustainability metrics. In addition to baseline biorefining conditions, uncertainties across the algal biofuel production system are assessed through a Monte Carlo analysis of λo. A case study is developed to compare Combined Algal Processing (a biochemical conversion pathway) against hydrothermal liquefaction (a thermochemical conversion pathway). Baseline results show that lipids are always heavily favored for fuel production, but no practical cultivation operations would be able to achieve such lipid-heavy biomass. The Monte Carlo analysis reveals that current algal fuel conversion technologies cannot simultaneously satisfy all key sustainability objectives. If biomass productivity is doubled and the feedstock is high in lipids, hydrothermal liquefaction can achieve a mean λo=0.53±0.12, still well below a desirable λo of 1. Combined Algal Processing struggles to achieve high satisfaction scores even in optimistic scenarios and requires a high-lipid feedstock to achieve a mean λo=0.10±0.03. Hydrothermal liquefaction can be integrated downstream of Combined Algal Processing to increase fuel yield and optimistically can achieve a mean λo=0.48±0.07. A combination of system improvements, including biomass productivity, feed composition, fuel yield, and implementation of co-product pathways must work together to satisfy all the relevant sustainability metrics for algal biofuels. The scoring methodology developed here can be readily applied to other microalgal biorefinery concepts and, more broadly, to sustainable fuel development and production.

Attached microalgal growth of Chlorella vulgaris on palm decanter cake (PDC) under irradiation with various visible monochromatic and polychromatic spectra to produce biodiesel was studied in this work. The results demonstrated that the white spectrum cultivation exhibited the highest microalgal density of 1.13 g/g along with 1.213 g/L day of microalgal productivity. Correspondingly, the biodiesel obtained was comprised mainly of C16 and C18 fatty acids, possessing a high cetane number and oxidation stability from the high saturated fatty acid content (70.38%), which was appealing in terms of most biodiesel production requirements. Nevertheless, the highest lipid content (14.341%) and lipid productivity (93.428 mg/L per day) were discovered with green spectrum cultivation. Blue and white spectra led to similar protein contents (34%) as well as carbohydrate contents (61%), corroborating PDC as a feasible carbon and nutrient source for growing microalgae. Lastly, the energy feasibilities of growing the attached microalgae under visible spectra were investigated, with the highest net energy ratio (NER) of 0.302 found for the yellow spectrum. This value outweighed that in many other works which have used suspended growth systems to produce microalgal fuel feedstock. The microalgal growth attached to PDC is deemed to be a suitable alternative cultivation mode for producing sustainable microalgal feedstock for the biofuel industry. [ABSTRACT FROM AUTHOR]

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This study presents a comparison in terms of both environmental effect/energy efficiency of different designs of the process for sugarcane/sugar beet molasses-based bioethanol. In the present work, two scenarios were designed/compared, including the production of sugarcane-based (Scenario 1) and sugar beet molasses bioethanol (Scenario 2) in Khuzestan Province as an agricultural hub of Iran. Furthermore, an improved process, including a biogas production line from the residual vinasse from the distillation of molasses for bioethanol obtaining is presented, both from sugarcane (scenario 3) and sugar beet (scenario 4), and life cycle assessment (LCA) method was employed for determination of environmental impacts. The results, in terms of net energy value (NEV), i.e. the difference between the energy content of ethanol and the energy used in its production and distribution, were very similar as 11.03 MJ and 11.15 MJ, respectively. Nevertheless, the results of the environmental impact analysis indicated that bioethanol production from sugarcane molasses had a higher impact compared to the sugar beet in terms of global warming potential, fossil, and metal depletion, particulate matter formation, human toxicity, and climate change ecosystems. Furthermore, the addition of the biogas production plant from the residual vinasse (scenarios 3 and 4) resulted in a considerable reduction of all studied environmental impacts (i.e., climate change, human toxicity, ozone depletion, photochemical oxidant formation, terrestrial acidification, freshwater ecotoxicity, marine ecotoxicity, ionizing radiation, fossil depletion, and global warming). As an example, by applying scenarios 3 and 4, the global warming potential for sugarcane and sugar beet was reduced by 61.2% and 83%, and the climate change decreased by 61% and 81% for bioethanol production from sugarcane and sugar beet, respectively. [ABSTRACT FROM AUTHOR]

Flywheel energy storage systems are feasible for short-duration applications, which are crucial for the reliability of an electrical grid with large renewable energy penetration. Flywheel energy storage system use is increasing, which has encouraged research in design improvement, performance optimization, and cost analysis. However, the system's environmental impacts for utility applications have not been widely studied. Evaluating the life cycle environmental performance of a flywheel energy storage system helps to identify the hotspots to make informed decisions in improving its sustainability; to make reasonable comparisons with other energy storage technologies, such as pumped hydro, compressed air, electro-chemical batteries, and thermal; and to formulate environmental policy in the energy sector. In this study, an engineering principles-based model was developed to size the components and to determine the net energy ratio and life cycle greenhouse gas emissions of two configurations of flywheel energy storage: steel rotor flywheel and composite rotor flywheel. The net energy ratio is a ratio of total energy output to the total non-renewable energy input over the life cycle of a system. Steel rotor and composite rotor flywheel energy storage systems were assessed for a capacity of 20 MW for short-duration utility applications. A consistent system boundary was considered for both systems with the life cycle stages of material production, operation, transportation, and end-of-life. Electricity from solar and wind was considered separately in the operation phase. The net energy ratios of the steel rotor and composite rotor flywheel energy storage systems are 2.5–3.5 and 2.7–3.8, respectively. The corresponding life cycle greenhouse gas emissions are 75.2–121.4 kg-CO2eq/MWh and 48.9–95.0 kg-CO2eq/MWh, depending on the electricity source. The net energy ratio and greenhouse gas emissions are highly influenced by the operation phase, which includes charging and standby modes. Uncertainty analysis shows that the life cycle greenhouse gas emissions are most sensitive to the solar, wind, and grid electricity mix emission factors. The results of this study will help to understand the carbon footprints of the various utility-scale energy storage systems.

Over the past years, there were dramatic improvements in identifying and assessing various feedstocks for the production of biodiesel fuels. To promote a particular feedstock as a renewable source of energy, it is important to analyze their energy, economic, and engine performance characteristics. The current work attempts to evaluate the net energy and economic indices for both fossil diesel and coconut-blended diesel (B20) considering the diesel consumption by the Indian railways. Further, we present the experimental results of a multi-cylinder diesel engine operated with neat coconut biodiesel (B100) and fossil diesel at various load and speed conditions. The engine experiments reveal that the coconut biodiesel exhibits leaner combustion and shorter ignition delay than fossil diesel. Lower amount of carbon monoxide, hydrocarbon, and smoke emission is observed in the case of coconut biodiesel, with higher levels of nitric oxide (14%) and fuel consumption than diesel. The coefficient of variation in indicated mean effective pressure is within the range of better driveability zone for both the fuels at all test conditions. Overall the engine performance, emission and combustion results with neat coconut biodiesel are favorable with a penalty in NO emission at high load conditions. The techno-economical study highlights higher production cost per liter of B20 than the cost of fossil diesel. However, the net energy ratio (NER) for B20 is 1.021, favoring higher output than diesel and thus lowers the dependency on crude oil. [ABSTRACT FROM AUTHOR]

Abstract Microalgae is an alternative feedstock for biofuel production and has been considered to be a potential biotechnology. However, the systems for industrial biofuel production from microalgae are still costly and unsuitable. In addition, the complex and changeable processes contained in different bioenergy conversion systems make it difficult to reasonably compare these systems. This study aim to obtain an optimal microalgae-based industrial system using life-cycle assessment, and to unify the uncertainties caused by the discrepancies of each process. Two types of bioenergy conversion systems were modelled and compared: (1) transesterification, hydrothermal liquefaction, and pyrolysis for renewable diesel production and (2) anaerobic digestion without/with hydrothermal pretreatment for biogas production. The life-cycle impacts of these systems were quantified in terms of net energy ratios (NERs) and greenhouse gas (GHG) emissions. The results show that anaerobic digestion system with hydrothermal pretreatment is more industrially feasible and eco-friendly at the industrial scale due to its low NER (0.71) and GHG emissions [−60.84 g CO 2−eq (MJ biogas)−1]. Graphical abstract Image 1 Highlights • A life-cycle assessment of biofuel production from microalgae was performed. • Five different bioenergy conversion systems were compared in terms of NER and GWP. • The AD system with pretreatment achieved the optimal overall net energy income. • Sensitivity analysis of processes in the conversion systems were conducted. [ABSTRACT FROM AUTHOR]

Abstract With their fast growth rate and ability to accumulate a high percentage of their weight as lipid and carbohydrate, microalgae potentially represent an ideal feedstock for the production of biodiesel and bioethanol. In addition, microalgae offer several environmental benefits, and do not compete with food production for land, fresh water, and nutrients. Therefore, the main goal of this work is to provide a quantitative, systematic and harmonized assessment of current bio-energy potential. The analysis is conducted by considering all the main steps in detail, from cultivation to biodiesel production, and by deriving an overall estimation of energy consumption for biodiesel production. Energy consumption uncertainty is also quantified and discussed. A systematic review of all the main technologies available for all the main processing steps towards the production of biodiesel from microalgae is presented, focusing on the derivation of the Net Energy Ratio (NER) of each combination of technologies, complemented by an uncertainty analysis of the data used and those obtained in the present work. A wide scatter in the data available in the literature has been identified, highlighting the need for an uncertainty analysis. If the average overall energy consumption per unit of biodiesel mass is considered, all the routes adopting a raceway pond have a lower energy consumption, but if the uncertainty on the overall energy consumption is also considered, the minimum value of the range of NER values for some of the routes adopting a photobioreactor is comparable to the NER value obtainable by using raceway ponds. Thus, the present framework proposes a harmonized and comprehensive methodology to compare and contrast technologies for the production of biodiesel from microalgae, and is applied in this paper to identify, with an appreciation of the uncertainty, the most promising combinations of technologies. Highlights • Quantitative, systematic and harmonized assessment of microalgae energy potential. • A step-by-step analysis and overall estimation of energy consumption is given. • A substantial uncertainty on the data in literature has been identified. • The energy consumption uncertainty is quantified and critically discussed. • Derivation of the Net Energy Ratio (NER) for each combination of technologies. [ABSTRACT FROM AUTHOR]

Abstract In this study, a process model was developed to determine the net energy ratios and life cycle greenhouse gas emissions of three energy storage systems: adiabatic and conventional compressed air energy storage and pumped hydroelectric energy storage, with estimated capacities of 118, 81, and 60 MW, respectively. The net energy ratios were calculated as ratios of net energy outputs to the total net energy inputs. The greenhouse gas emissions associated with construction, operation, decommissioning life cycle stages of the energy storage systems were evaluated. The net energy ratios for the adiabatic and conventional compressed air energy storage and pumped hydroelectric energy storage are 0.702, 0.542, and 0.778, respectively. The respective life cycle greenhouse gas emissions in g CO 2 eq./kWh are 231.2, 368.2, and 211.1. The emissions are highly dominated by the operational stage in all the energy storage systems. It was also observed that energy consumption in the form of electricity is the key driver, while the contributions due to the use of material are minimal. Sensitivity and uncertainty analysis was also performed. The results help in understanding the comparative net energy ratios and emission footprints of various energy storage systems in order to make an informed decision. Highlights • The study focuses on a life cycle assessment of energy storage systems. • Net energy ratios (NERs) for pumped storage systems (PHS) and compressed air energy storage systems (CAES) are developed. • The conventional CAES has a lower NER than the adiabatic CAES. • PHS has a higher NER than CAES. • Life cycle GHG emissions for conventional CAES are higher than for PHS. [ABSTRACT FROM AUTHOR]

Highlights • CO 2 bio-sequestration from LPG-burner exhaust-gas streams using an untapped microalga Coelastrella sp. FI69 were studied. • Acclimatization of microalgal cultures in 10% CO 2 by a conventional scale up procedure aided growth in exhaust-gas streams. • Energy potential of biomass was examined through calorific value, lipid potential and biochemical methane yield potential. • A methodology to achieve a higher net energy ratio for the cultivation were figured out. Abstract This present study evaluated the potential of an untapped thermo-tolerant microalga, Coelastrella sp. FI69 as a promising candidate for scalability, CO 2 bio-sequestration and biomass production. The microalga is preliminarily cultivated in elevated CO 2 and finite NO 3 − growth habitat at outdoor field, and developed from lower to higher volume culture. The scaled up culture is eventually used as seed (in two different initial inoculum density, 0.01 and 0.1 g L−1 DW 1 1 Dry weight), in 200 L open rectangular pond (ORP 2 2 Open rectangular pond) reactor aerated with LPG combusted exhaust-gas streams (10 vol. % of CO 2 , 150 ppm of nitrogenous gases at atmospheric pressure and 30–40 °C) for 8–10 days for biomass production. The biomass production rate (BPR 3 3 Biomass production rate), maximum specific growth rate (μ max 4 4 Maximum specific growth rate), CO 2 bio-fixation rate (CBFR 5 5 CO 2 bio-fixation rate) and maximum biomass density (D B-max 6 6 Maximum biomass density) of the microalga culture achieved in the exhaust-gas aeration at 0.01 and 0.1 g L-1 are found as 0.065 ± 0.005 and 0.116 ± 0.011 g DW L-1, 0.467 ± 0.014 and 0.426 ± 0.007 day-1, 0.112 ± 0.008 and 0.202 ± 0.002 g CO 2 L-1 day-1, and 0.529 ± 0.037 and 1.047 ± 0.022 g DW L-1, respectively. The harvested biomass had heating values of 20.2–21.7 MJ kg-1, contained 16–20% of lipids, and a theoretical methane potential of 586.2 mL CH 4 gVS-1. From the biomass energy potential analysis, the microalga cultivation system, which designed to utilize the combustion-gases for biomass production, could reach a promising higher net energy ratio. This study mostly highlights the significance of using the strain for utilization of CO 2 -rich gas streams. [ABSTRACT FROM AUTHOR]

Geothermal source is a clean technology that is able to use the ground as a thermal sink or heat source. It is one of the energy resources in Iran that can be used with long-term investment. This study provided a new idea for using this energy in heating and cooling of buildings. Two wells were used for heating and cooling with constant temperature of the water in depth of 12 m underground (this temperature is approximately equal to the annual temperature of environment during the year). Water flowed in six speeds: 10, 11.5, 13, 16, 29 and 34 lit min-1 using a hydraulic pump from first well, and after passing through radiator, discharged to other well. The outdoor temperature was 9°C, 40°C and 15.5°C -16°C for heating, cooling and well water, respectively. An axial fan was used to passing the air in six speeds: 0.5, 1.1, 2.2, 3.3, 4.4 and 7.4 m s-1 through the radiator. The results showed that the use of water from this well could reduce the required power about 25% for heating and could increase the air temperature from 9°C to 25°C. Also, this system could reduce the required power from 38% to 60% for cooling and could decrease the air temperature from 40°C to 25°C. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Optimal algae to cellulose ratios were 35%:65% and 20%:80% (volatile solids based). • Synergy resulted in enhancing the ten days cumulative methane yield up to 100%. • Co-digestion reduced time-lag by 50% and increased methane production rate by 35%. • Modified Gompertz kinetic model offered superior methane production description. • Co-digestion boosted the Energy Output and NER by 30–45% depending on the HRT. Abstract This study investigated enhancing methane production from algal-bacteria biomass by adjusting the C/N ratio through co-digestion with a nitrogen-poor co-substrate – cellulose. A biomethane potential test was used to determine cumulative biogas and methane production for pure and co-digested substrates. Four kinetic models were evaluated for their accuracy describing experimental data. These models were used to estimate the total energy output and net energy ratio (NER) for a scaled AD system. Increasing the algal C/N ratio from 5.7 to 20–30 (optimal algae:cellulose feedstock ratios of 35%:65% and 20%:80%) improved the ultimate methane yield by >10% and the first ten days production by >100%. The modified Gompertz kinetic model demonstrated highest accuracy, predicting that co-digestion improved methane production by reducing the time-lag by ∼50% and increasing rate by ∼35%. The synergistic effects increase the AD system energy efficiency and NER by 30–45%, suggesting potential for substantial enhancements from co-digestion at scale. [ABSTRACT FROM AUTHOR]

Life cycle assessments of microalgal cultivation systems are often conducted to evaluate the sustainability and feasibility factors of the entire production chain. Unlike widely reported conventional microalgal cultivation systems, the present work adopted a microalgal-bacterial cultivation approach which was upscaled into a pilot-scale continuous photobioreactor for microalgal biomass production into biodiesel from wastewater resources. A multiple cradle-to-cradle system ranging from microalgal biomass-to-lipid-to-biodiesel was evaluated to provide insights into the energy demand of each processes making up the microalgae-to-biodiesel value chain system. Energy feasibility studies revealed positive NER values (4.95–8.38) for producing microalgal biomass but deficit values for microalgal-to-biodiesel (0.14–0.23), stemming from the high energy input requirements in the downstream processes for converting biomass into lipid and biodiesel accounting to 88–90% of the cumulative energy demand. Although the energy balance for microalgae-to-biodiesel is in the deficits, it is comparable with other reported biodiesel production case studies (0.12–0.40). Nevertheless, the approach to using microalgal-bacterial cultivation system has improved the overall energy efficiency especially in the upstream processes compared to conventional microalgal cultivation systems. Energy life cycle assessments with other microalgal based biofuel systems also proposed effective measures in increasing the energy feasibility either by utilizing the residual biomass and less energy demanding downstream extraction processes from microalgal biomass. The microalgal-bacterial cultivation system is anticipated to offer both environmental and economic prospects for upscaling by effectively exploiting the low-cost nutrients from wastewaters via bioconversion into valuable microalgal biomass and biodiesel. [Display omitted] • Algal-to-biodiesel system from new photobioreactor assessed for energy feasibility. • Positive NER values (4.95–8.38) for biomass production at base and best scenarios. • High energy demand from downstream processes lowered overall NER (0.14–0.23). • Lipid extraction solvent process demanded the highest energy requirement at 88–90%. • Residual biomass utilization and pretreatment process reduce overall energy demand. [ABSTRACT FROM AUTHOR]

The depletion of fossil fuel sources and increase in energy demands have increased the need for a sustainable alternative energy source. The ability to produce hydrogen from microalgae is generating a lot of attention in both academia and industry. Due to complex production procedures, the commercial production of microalgal biohydrogen is not yet practical. Developing the most optimum microalgal hydrogen production process is also very laborious and expensive as proven from the experimental measurement. Therefore, this research project intended to analyse the random time series dataset collected during microalgal hydrogen productions while using various low thermally pre-treated palm kernel expeller (PKE) waste via machine learning (ML) approach. The analysis of collected dataset allowed the derivation of an enhanced kinetic model based on the Gompertz model amidst the dark fermentative hydrogen production that integrated thermal pre-treatment duration as a function within the model. The optimum microalgal hydrogen production attained with the enhanced kinetic model was 387.1 mL/g microalgae after 6 days with 1 h thermally pre-treated PKE waste at 90 °C. The enhanced model also had better accuracy (R 2 = 0.9556) and net energy ratio (NER) value (0.71) than previous studies. Finally, the NER could be further improved to 0.91 when the microalgal culture was reused, heralding the potential application of ML in optimizing the microalgal hydrogen production process. [Display omitted] • Thermal pre-treated palm kernel expeller as a substrate for dark fermentation. • Machine learning-based kinetic model in predicting microalgal hydrogen production. • Integrated Gompertz model with thermal pre-treated function for optimization study. • Energy feasibility to produce green hydrogen from thermal pre-treated substrate. [ABSTRACT FROM AUTHOR]

Excessive use of N fertilizer in intensive agriculture can increase crop yield and at the same time cause high carbon (C) emissions. This study was conducted to determine optimized N fertilizer application for high grain yield and lower C emissions in summer corn (Zea mays L.). A field experiment, including 0 (N0), 75 (N75), 150 (N150), 225 (N225), and 300 (N300) kg N ha−1 treatments, was carried out during 2010–2012 in the North China Plain (NCP). The results showed that grain yield, input energy, greenhouse gas (GHG) emissions, and carbon footprint (CF) were all increased with the increase of N rate, except net energy yield (NEY). The treatment of N225 had the highest grain yield (10 364.7 kg ha−1) and NEY (6.8%), but the CF (0.25) was lower than that of N300, which indicates that a rate of 225 kg N ha−1 can be optimal for summer corn in NCP. Comparing GHG emision compontents, N fertilizer (0–51.1%) was the highest and followed by electricity for irrigation (19.73–49.35%). We conclude that optimazing N fertilizer application rate and reducing electricity for irrigation are the two key measures to increase crop yield, improve energy efficiency and decrease GHG emissions in corn production.

Camelina sativa is a cool-season oil seed crop that has been proven to produce various biofuels. The present study investigated the technical possibilities of using whole camelina biomass as a model feedstock in a biorefinery. This investigation examined the possibilities of using camelina seeds as a source of oil for biodiesel, sugars for ethanol, and meal for oneportfolio products. The camelina harvest residues (straw) can serve as the main source for green sugars. This study found that the energy input for the whole biorefinery process was 25.1 MJ/L ethanol, while the energy output was 54.3 MJ/L ethanol. The net energy ratio of 2.16 MJ/L ethanol was found to be competitive with other energy crops. The process was environmentally friendly, and it reduced greenhouse gas emissions by 40% if the produced biodiesel replaced petroleum diesel. The seed meals and glycerin were found to be a good source of revenue as high valueadded products and can provide an additional revenue of $1/kg of produced oil. [ABSTRACT FROM AUTHOR]

Electricity supply in India is from a centralized grid. Many parts of the country experience grid interruptions. Life cycle energy and environmental analysis has been done for a 27 kWp photovoltaic system which acts as grid backup for 3 h outage in an Indian urban residential scenario. This paper discusses energy requirements and carbon emission for a PV storage system for five different battery technologies in Indian context. This can be used as a metric for comparative analysis for new batteries, with an undeveloped market. The energy requirements for the components are quantified and are compared in terms of energy payback time (EPBT) and Net Energy Ratio (NER). All the calculations are done for Indian context. EPBT is found to be in the range of 2-4.5 years for all the systems, while NER is in the range of 6.6-2.52. NaS has the highest emission factor of 0.67 kgCO/kWh and the least for NiCd (0.091 kgCO/kWh). These factors can be used to select a PV battery option and to target selection of materials and systems based on the reported values. [ABSTRACT FROM AUTHOR]

The agroforestry system that integrate non-food, perennial trees bearing oilseeds (TBO) with agricultural crops on low quality land, has potential to sustainably produce biofuels with considerable GHG savings and has livelihood benefits for the farmers. We evaluated many TBOs with a life cycle assessment methodology. We quantified Net Energy Balance (NEB), Net Energy Ratio (NER) and greenhouse gas (GHG) emissions saving potential in comparison to fossil fuels. The study focused on agroforestry-based biofuel production from seven tree species i.e. Pongamia pinnata, Madhuca indica, Azadirachta indica, Simarouba glauca, Amoora rohituka, Calophyllum inophyllum and Jatropha curcas . In a comparative assessment with first generation biofuels from corn and soybean, agroforestry based biofuels had NER values from 1.42 to 2.03 while soybean and corn had NER values of 0.43 and 0.54, respectively, when only biofuel energy was considered. When co-products energy was also considered, the NER values of agroforestry based biofuels increased manifold and ranged between 4.2 and 6.44, while for soybean and corn it was 1.35 and 0.88 respectively. The GHG emissions saving of agroforestry based biofuels ranged from 24.3 CO 2 -Eq/MJ to 41.7 CO 2 -Eq/MJ, while soybean and corn had negative GHG emissions saving of −137 CO 2 -Eq/MJ and −99 CO 2 -Eq/MJ respectively. [ABSTRACT FROM AUTHOR]

The net energy ratios (NERs) and greenhouse gas (GHG) emissions of a Photosynthetic Cyanobacterial Biorefinery (PSBR) were evaluated using a Life Cycle Assessment (LCA) approach. This study assessed engineered cyanobacterium cultures in which biosynthetic biofuels are directly secreted. Biofuels researched in this study include bisabolane, a biosynthetic substitute for D2 diesel; heptadecane, a substitute for diesel; and ethanol, a substitute for gasoline. Results demonstrate that cyanobacteria-based ethanol has higher yields, lower NER, and lower GHG emissions than bisabolane and heptadecane products in Synechocystis sp. PCC6803. By performing a sensitivity analyses of the life cycle NER and GHG emissions responses of the system, we derived the improvements in system biology, metabolic engineering, and process engineering that would be required to minimize the environmental impacts at an industrial scale. The NER and GHG emissions of the biofuel products were found to be the most sensitive to organism-level biofuel productivities, the energy consumption of vapor compression and distillation, and the energy consumption of culture mixing. This LCA will serve as a baseline for stakeholders; including policy makers, cyanobacterial refineries, and researchers, to establish the goals to engineer cyanobacteria and sustainable bioprocesses. [ABSTRACT FROM AUTHOR]

Ethylic transesterification process for biodiesel production without any chemical or biochemical catalysts at different subcritical thermodynamic conditions was performed using wet animal fat, soybean and palm oils as feedstock. The results indicate that 2 h of reaction at 240 °C with pressures varying from 20 to 45 bar was sufficient to transform almost all lipid fraction of the samples to biodiesel, depending on the reactor dead volume and proportions between reactants. Conversions of 100%, 84% and 98.5% were obtained for animal fat, soybean oil and palm oil, respectively, in the presence of water, with a net energy ration values of 2.6, 2.1 and 2.5 respectively. These results indicate that the process is energetically favorable, and thus represents a cleaner technology with environmental advantages when compared to traditional esterification or transesterification processes. [ABSTRACT FROM AUTHOR]

The feasibility of attached culture Chlorella vulgaris in a porous substratum biofilm reactor (PSBR) for simultaneous wastewater treatment and biofuel production was investigated. The characteristics, including algal biofilm growth, lipid yield, nutrient removal, and energy efficiency of the outdoor cultures, were investigated under the influence of both inoculum densities and the percent submerged area. A maximum biofilm productivity of 57.87 g m d with 81.9 % adhesion was achieved under optimal conditions (inoculum density of 18 g m and the percent submerged area of 5.7 %). The lipid content and lipid yield were 38.56 % and 27.25 g m d, respectively. Meanwhile, the algae removed 99.95 % ammonia, 96.05 % total nitrogen (TN), and 99.83 % total phosphorus (TP). Further, the energy life cycle for the PSBR was analyzed. The biomass productivity per unit irradiance was up to 4.6 g MJ (photosynthetic efficiency of 10.65 %). The PSBR was considered to be economically feasible due to the net energy ratio of 1.3 (>1). [ABSTRACT FROM AUTHOR]

Microalgae-based biorefineries for the production of renewable biofuels like biodiesel, upgraded bio-oil, biochar, biogas and other high-value chemicals have received great attention in recent decades as potential major sources of energy for the future. Microalgae are a suitable species to produce biodiesel and other high energy density by-products; however, it is questionable whether a net energy gain can be realized or not considering the whole processing chain. In the present study, the energy balances of different algae-based biofuel and bioenergy production technologies are investigated in detail and compared to each other corresponding to a cradle-to-grave overall energetic analysis. The study includes cultivation, harvesting, cell pretreatments (cell disruption, drying, grinding), lipid extraction, transesterification, gasification and hydrothermal liquefaction with bio-oil stabilization and hydroprocessing. The energy consumption and energy gain are estimated for each operational step to determine the net energy ratio (NER, energy output over energy input) for the overall technologies studied. Our detailed investigation enables to detect the most energy consuming unit operation, that is, the bottleneck point(s) of the microalgae-based technologies which should be still improved in the future for the sake of more efficient algae-based biorefineries. The investigation makes also possible to evaluate and compare the different large scale alternatives for biomass transformation. Positive energy balances with a NER value of 1.109 and 1.137 are found in two already existing processes: open raceway ponds and closed photobioreactors, respectively. Our work gives also a detailed algorithm that can be followed at the evaluation of other microalgae-based biorefineries. [ABSTRACT FROM AUTHOR]

This paper evaluates the life cycle impact (LCI) of a 1.5 kW solar photovoltaic (PV) system. The LCI is examined in terms of the life cycle emission rate (LCER), global warming potential (GWP), cumulative energy demand (CED), energy payback time (EPT) and net energy ratio (NER), using six different locations - one from each of Nigeria's six geo-political zones as case studies. With a performance ratio of 80%, lifetime of 20–30 years, module efficiency of 15.4%, solar irradiation of 1493–2223 kWh/m 2 /yr, LCER of 37.3–72.2 g CO 2 /kWh and CED of 3800–8700 MJ eq., the GWP, EPT and NER values of 1907–5819 kg CO 2 -eq., 0.83–2.3 years and 7.08–36.17, respectively, are obtained. The significance of these results is that the lowest GWP and EPT, i.e. 1907 kg CO 2 -eq. and 0.83 years, are obtained for the location with the highest solar irradiation, while the highest values, i.e. 5819 kg CO 2 -eq. and 2.3 years, are obtained for the location with the lowest irradiation. Furthermore, the highest NER is obtained for the location with the highest irradiation while the lowest value has been obtained for the location having the lowest irradiation. The study provides an insight into the significance and impact of a location's solar energy potential on the environmental performance of a PV system, which can be useful for energy analysis, planning and decision-making purposes. [ABSTRACT FROM AUTHOR]

The Brazilian sugarcane mills already provide significant amounts of renewable products (ethanol and bioelectricity) through self-sufficient bagasse cogeneration. Gaseous outputs of the sector can provide streams rich in biogenic carbon dioxide (CO 2), suitable for the autotrophic cultivation of microalgae and aim, hereinafter, their conversion into biodiesel. This work modeled the integration of an ethanol plant with a cogeneration system, covering the enzymatic hydrolysis of bagasse and the production of microalgae biodiesel. A standard ethanol plant yielding 96 L ethanol/t cane may produce an additional 7.5–30 L microalgae biodiesel/t cane but at the expense of its energy self-sufficiency; the biorefinery must recur to fossil resources unless other biomass (besides bagasse) and coproducts by the plant's neighborhood can be exploited. The process simulation is conducted in nine cases derived from a central composite design with two factors – the fraction of bagasse destined for the hydrolysis system (x 1) and the fraction of ethanol sent to produce anhydrous ethanol (x 2) – and three levels for each factor (0, 50, 100%). Energy ratios between representative outputs and inputs – Net energy ratio (NER) and Fossil energy ratio (FER) –, direct CO 2 emission, and exergy efficiencies were calculated as representative responses to evaluate the plant's technical and environmental efficiencies. Statistical tools (t-Student test, ANOVA, and R2) showed that the constructed models were robust and that the responses varied significantly with x 1 , while x 2 produced mild or negligible effects. The highest achievable NER and FER were 0.83 and 2.09, respectively. The whole system resulted in a FER equal to 1 when bagasse usage is split in half between the hydrolysis and cogeneration systems. This result guarantees that the energy related to the useful products is higher than the requirements of fossil energy inputs, within an acceptable range. The optimum CO 2 emission and exergy efficiency were found when 6–8% of the bagasse is hydrolyzed, which is also a range covering attractive energy ratios. The proposed integration benefits the sector, but resorting to renewable sources to supply energy deficits, developing the technological exploitation over wasted coproducts, and studying heat and mass integration of processes are highly recommended to enhance the global-system performance. [Display omitted] • The highest Fossil Energy Ratio of the biorefinery reached a value of 2.1. • Bagasse usage is the most significant factor in the Central Composite Design. • Exergy efficiency doubled to 60% with the inclusion of more marketable coproducts. • The partial bagasse hydrolysis (6–8% of the total) produced the lowest emissions. • The oil extraction is the crucial step (high energy demand and exergy loss). [ABSTRACT FROM AUTHOR]

This study examined the sustainability of generating renewable diesel via hydrothermal liquefaction (HTL) of biomass from a rotating algal biofilm reactor. Pilot-scale growth studies and laboratory-scale HTL experiments were used to validate an engineering system model. The engineering system model served as the foundation to evaluate the economic feasibility and environmental impact of the system at full scale. Techno-economic results indicate that biomass feedstock costs dominated the minimum fuel selling price (MFSP), with a base case of $104.31 per gallon. Life-cycle assessment results show a base-case global warming potential (GWP) of 80 g CO 2 -e MJ −1 and net energy ratio (NER) of 1.65 based on a well-to-product system boundary. Optimization of the system reduces MFSP, GWP and NER to $11.90 Gal −1 , −44 g CO 2 -e MJ −1 , and 0.33, respectively. The systems-level impacts of integrating algae cultivation with wastewater treatment were found to significantly reduce environmental impact. Sensitivity analysis showed that algal productivity most significantly affected fuel selling price, emphasizing the importance of optimizing biomass productivity. [ABSTRACT FROM AUTHOR]

Agricultural residues (wheat/barley/oat straw) can be used to produce charcoal, which can then be either landfilled off-site or spread on the agricultural field as a means for sequestering carbon. One centralized and five portable charcoal production technologies were explored in this paper. The centralized system produced 747.95 kg-CO 2 eq/tonne-straw and sequestered 0.204 t-C/t-straw. The portable systems sequestered carbon at 0.141–0.217 t-C/t-straw. The net energy ratio (NER) of the portable systems was higher than the centralized one at 10.29–16.26 compared to 6.04. For the centralized system, the carbon sequestration and the cumulative energy demand were most sensitive to the charcoal yield. Converting straw residues into charcoal can reduce GHG emissions by 80% after approximately 8.5 years relative to the baseline of in-field decomposition, showing these systems are effective carbon sequestration methods. [ABSTRACT FROM AUTHOR]

In this work, Chlorella pyrenoidosa was converted into bio-oil via solvolysis liquefaction in sub/supercritical ethanol–water system. The influence of reaction temperature (220–300 °C), retention time (0–120 min), solid/liquid ratio (6.3/75–50.0/75 g/mL) and ethanol content (0–100%) on bio-oil yield and property was investigated. The increase of reaction temperature and retention time both improved the bio-oil yield. The bio-oil yield increased firstly and then decreased when the solid/liquid ratio and ethanol content exceeded 18.8/75 g/mL and 80%, respectively. As the reaction temperature <260 °C and retention time <30 min, a soft and unsticky product was insoluble in dichloromethane (DCM) during the extraction process. The chemical composition of the DCM-insoluble product was analyzed by FTIR (Fourier Transform Infrared Spectrometry). The change tendency of O/C and H/C atomic ratio of bio-oil indicated that the addition of ethanol contributed to deoxygenation and hydrogen-donating for bio-oil, due to the dehydration and decarboxylation reaction. 1 H NMR (hydrogen-1 nuclear magnetic resonance) analysis indicated that the main chemical compositions of bio-oil were aliphatic functional groups and heteroatomic functionalities (80.00–83.58%). The addition of ethanol enhanced the transesterification to form more ester. The NER (net energy ratio, the ratio of energy output to energy consumption) of solvolysis liquefaction in ethanol–water system (NER < 1) was less than that of hydrothermal liquefaction in sole water system (NER = 1.29), but the NERs of 20% and 40% ethanol content (NER = 0.91, 0.70 for 20% and 40% ethanol content) were larger than pyrolysis technology (NER = 0.66). The high bio-oil yield, better bio-oil property and high NER were achieved at reaction temperature of 300 °C, with retention time of 60 min, solid/liquid ratio of 18.8/75 g/mL and ethanol content of 40% (bio-oil yield = 39.75%, HHV (higher heating value) = 39.31 MJ/kg and NER = 0.70). [ABSTRACT FROM AUTHOR]

Life cycle assessment has been widely accepted as an effective tool to assess the environmental impacts of various biofuels in comparison with conventional fuels to quantify the potential benefits in both energy and environmental aspects. This work focused on life cycle assessment of the production of diesel via pyrolysis using two potential feedstocks in Thailand: crude palm oil (CPO) and waste cooking oil (WCO). The system boundary consists of the cultivation, harvesting, transportation, pyrolysis, distillation, blending, and vehicle testing (combustion). Inventory data were collected at the pilot plant of the Center for Fuels and Energy from Biomass of Chulalongkorn University located in Saraburi province. All collected data were input into SimaPro program to evaluate the relevant environmental impacts such as global warming potential, acidification, and ozone depletion based on a functional unit of 1 MJ of diesel. For the fuel production, the resulting diesel was blended with conventional diesel at 2, 5, and 20 wt% to obtain blended diesel fuels (B2, B5, and B20), respectively. The energy and potential environmental impacts of the diesel fuels produced from two different feedstocks, CPO and WCO, were compared based on cradle-to-grave. The results showed that net energy ratio with its co-products of WCO-based diesel (3.12) was higher than that of CPO-based diesel (2.12). Because of the large amount of energy use for diesel production in pyrolysis and distillation processes, global warming potential was the main environmental impact. From scenarios, it can be concluded that recycling methane from exhaust gas and replacing liquefied petroleum gas by natural gas lead to reduce energy input of 2% and global warming potential impact over 10%. Pyrolysis oil is possible to improve over time on account of the increase of waste palm oil and development of new technologies. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Many LCA based viability studies have already been done for the production of green diesel from microalgae, still a comprehensive LCA, has not yet been undertaken. Current study aims to find out if the Net Energy Balance(NEB) can further be increased by using a combination of many available agronomical practices & the techniques of production of green diesel from microalgae. The results show that neither open raceway pond nor Photobioreactor routes (Wet and dry routes) yield positive energy balance. The production of green diesel via open raceway pond, both in dry as well as wet route, have less negative NEB and comparatively higher NER than the photobioreactors. Comparison says that open raceway pond dry route has slightly higher value for NER than the wet route. Even with the best possible route (open raceway pond dry route), the total energy use is almost 5 times more than the energy produced, with a negative NEB of 4.07 MJ & very low NER value of 0.20. Study concludes that R & D in the area of green diesel production from microalgae has yet to go a long way & has a huge scope to further lower its input energy demand for biofuel production. [ABSTRACT FROM AUTHOR]

Of the potential sources of renewables, the most promising one is microalgae, which are viewed as a biofuel feedstock and technological solution for CO2sequestration. Among microalgae-derived biofuels, biodiesel is one of the best application choices since microalgae have substantial amounts of oils. Nonetheless, microalgal biodiesel production is still in its infancy, since there is no commercial production on a large scale. The economic data and evaluation related to microalgal biodiesel production are incomplete and out of date, although lots of technological research has been carried out. This article demonstrates the pilot scale cultivation of microalgae in photobioreactors and evaluates the economics of producing oil from microalgae, including net energy ratio and cost-effectiveness evaluation. The contribution of this article lies in the presentation of an updated analysis of economic conditions for pilot scale microalgal oil production, which can provide the direction for future development of this important biofuel process. [ABSTRACT FROM PUBLISHER]

Current microalgae biofuel production pathways are still far from being energetically self-sufficient. Simulations scenarios (1 t · y−1 of biomass) under a purely energetic perspective, have revealed some bottlenecks mainly in the cultivation and metabolite recovery processes. Technologies such as intensified photobioreactors such as AlgoFilm©, infrared light filtering units, photovoltaic panels, solvent-free metabolite recovery processes, and high biomass concentration treatments at ⩾ 145 kg · m−3 are suggested and discussed to also have a major contribution on the net energy ratio of the process. An energy-driven biorefinery approach has been proposed to increase the energy output by obtaining bioethanol and biodiesel liquid fuels, but also photovoltaic energy during the same production process. The latter may also compensate for the large amounts of energy consumed in typical operations of the wet-pathway processes like harvesting-concentration, cell disruption, or solvent recycling processes. This perspective increased the final volume of liquid biofuels up to 57%. It was found a maximum net energy ratio of 1.9 for a double biofuel process, and 8.5 if photovoltaic energy is also considered. [ABSTRACT FROM AUTHOR]

The economic feasibility and environmental impact is investigated for the conversion of agricultural waste, delactosed whey permeate, through yeast fermentation to a renewable diesel via hydrothermal liquefaction. Process feasibility was demonstrated at laboratory-scale with data leveraged to validate systems models used to perform industrial-scale economic and environmental impact analyses. Results show a minimum fuel selling price of $4.78 per gallon of renewable diesel, a net energy ratio of 0.81, and greenhouse gas emissions of 30.0 g-CO 2 -eq MJ −1 . High production costs and greenhouse gas emissions can be attributed to operational temperatures and durations of both fermentation and hydrothermal liquefaction. However, high lipid yields of the yeast counter these operational demands, resulting in a favorable net energy ratio. Results are presented on the optimization of the process based on economy of scale and a sensitivity analysis highlights improvements in conversion efficiency, yeast biomass productivity and hydrotreating efficiency can dramatically improve commercial feasibility. [ABSTRACT FROM AUTHOR]

Spatial variability in yields and greenhouse gas emissions from soils has been identified as a key source of variability in life cycle assessments (LCAs) of agricultural products such as cellulosic ethanol. This study aims to conduct an LCA of cellulosic ethanol production from switchgrass in a way that captures this spatial variability and tests results for sensitivity to using spatially averaged results. The Environment Policy Integrated Climate (EPIC) model was used to calculate switchgrass yields, greenhouse gas (GHG) emissions, and nitrogen and phosphorus emissions from crop production in southern Wisconsin and Michigan at the watershed scale. These data were combined with cellulosic ethanol production data via ammonia fiber expansion and dilute acid pretreatment methods and region-specific electricity production data into an LCA model of eight ethanol production scenarios. Standard deviations from the spatial mean yields and soil emissions were used to test the sensitivity of net energy ratio, global warming potential intensity, and eutrophication and acidification potential metrics to spatial variability. Substantial variation in the eutrophication potential was also observed when nitrogen and phosphorus emissions from soils were varied. This work illustrates the need for spatially explicit agricultural production data in the LCA of biofuels and other agricultural products. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the full-chain carbon cycle of oil palm to determine the CE (carbon equivalences), starting from plantation until production of end-user products including RBD (refined, bleached, and deodorized) Palm Olein as a cooking oil and PME (palm methyl ester) as biodiesel fuel. Based on the carbon categorization, the equivalent carbon emissions from RBD Palm Olein and PME productions were found to be 159 and 153 kg CE/ton product, respectively. The major emissions in the RBD Palm Olein production chain are attributed to the use of natural gas for energy spent in the industrial process and Poly Ethylene Terephthalate for product containers; whereas, those in the PME production are from methanol used in the transesterification. After identification of the carbon pathway, RBD Palm Olein exhibited a net emission of 116 kg CE/ha-y, but PME shows a net reduction of 2328 kg CE/ha-y. From energy balances and economic performances, PME is found to have higher net energy ratio, with 40% lower production cost per kg CE, than does RBD Palm Olein. Therefore, increasing the use of palm oil for biodiesel production rather than as use for cooking oil is justified as a useful tool for climate change mitigation. [ABSTRACT FROM AUTHOR]

EU targets require nearly zero energy buildings (NZEB) by 2020. However few monitored examples exist of how NZEB has been achieved in practise in individual residential buildings. This paper provides an example of how a low-energy building (built in 2006), has achieved nearly zero energy heating through the addition of a solar domestic hot water and space heating system (“combi system”) with a Seasonal Thermal Energy Store (STES). The paper also presents a cumulative life cycle energy and cumulative life cycle carbon analysis for the installation based on the recorded DHW and space heating demand in addition to energy payback periods and net energy ratios. In addition, the carbon and energy analysis is carried out for four other heating system scenarios including hybrid solar thermal/PV systems in order to obtain the optimal system from a carbon efficiency perspective. [ABSTRACT FROM AUTHOR]

Bioenergy sources are promising alternatives for sustainable energy production. Nevertheless, significant research and detailed analysis are necessary to identify the circumstances under which such energy sources can contribute to sustainability. This paper reviews the literature of Life Cycle Assessment (LCA) of microalgae-to-energy technologies and focuses in two categories, Greenhouse Gas (GHG) emissions and Net Energy Ratios (NER). The analysis is illustrated with a case study of microalgae biomass combustion to produce heat and compares the influence of different electricity sources with respect to GHG emissions and NER along the supply chain. Selected fossil energy sources were used as reference conditions. The methodology was LCA based on ISO 14044 standard, and most of the data used were extracted from a review of relevant scientific publications. Heat production from microalgae showed higher GHG emissions than those from fossil fuels with United States' electricity grid, but lower than those with the Brazilian one. The NER of heat from microalgae combustion life cycle is still disadvantageous compared to most of fossil options. However, the observation that fossil fuel options performed slightly better than microalgae combustion, in the two categories analyzed, must be understood in the context of a mature fossil energy technology chain. The fossil technology has less potential for improvements, while microalgae technology is beginning and has significant potential for additional innovations. [ABSTRACT FROM AUTHOR]

India's biofuel programme relies on the ethanol from molasses for blending into gasoline. Therefore, quantification of GHG (green house gas) emissions and the energy consumed during the process of ethanol production is desirable to help policy makers to take meaningful decisions. In order to establish the environmental impact of the biofuels, LCA (life cycle assessment) is conducted for 1 ton of fuel grade ethanol in the NR (northern region) and WR (western region) of India. Four different allocation approaches, WA (without any allocation), MA (mass allocation), EA (energy allocation) and MPA (market price allocation) are used to distribute emissions and energy consumption between the product and the co-products. Total GHG emissions are from 543.3 (−75.9%) to 8219.8 kg CO 2 -eq. (262.7%) in NR and 552.0 (−75.8%) to 7382.4 kg CO 2 -eq. (225.6%) with respect to gasoline. Similarly, the NER (net energy ratio) also varies with different allocation approaches and ranged from 0.38 to 3.39 in the NR and 0.48 to 4.23 in WR. Using MA approach, maximum GHG emissions reduction are, −75.9 and −75.8% and NER, 3.39 and 4.23 in NR and WR respectively indicates the environment and net energy benefits of fuel ethanol. It is observed that MA and EA approaches give more acceptable and real life results. [ABSTRACT FROM AUTHOR]

Energy usage and CO2emission between traditional electrodialysis reversal (EDR) and innovative EDR desalinations were compared. The difference between traditional and innovative EDR desalination depended on which concentrate treatment was employed. Traditional EDR desalination consists of electrodialysis as concentrate treatment, while innovative EDR desalination consists ofDunaliella salinaproduction as concentrate treatment. Microalgae speciesD. salinaandArthrospira (Spirulina) platensiswere cultured in used bottles (3.7 L) as reactors and using desalination concentrate and supernatant from anaerobic digested sludge (SADS) as growth medium and nutrients.D. salinawas grown in reactorsD1,D2,D3, andD4.Spirulina platensiswas inS1,S2,S3, andS4. SADS was supplied to reactorsD1,D2,S1, andS2as nutrient. Bold’s Basal Medium was supplied to reactorsD3andD4while F2 was supplied to reactorsS3andS4as nutrient. Conductivity of desalination concentrates used in reactorsD1andD3was 31.8 and inD2andD425.4 mS/cm, respectively. Conductivity of concentrate in reactorsS1andS3was 35.9 and inS2andS421.5 mS/cm, respectively. Dry weight concentrations ofD. salinagrown in reactorsD1andD2with SADS (1.36–1.49 g/L) were achieved which were more than that with Bold’s Basal Medium (0.84–1.04 g/L) in reactorsD3andD4. Dry weight concentrations ofS. platensiswith SADS (1.41–1.98 g/L) in reactorsS1andS2were achieved which were more than that supplied with F2 (0.68–1.20 g/L) in reactorsS3andS4. In those cases where SADS was the nutrient, low conductivity mediums provided the higher microalgae dry weight concentrations. Dry weights of both species achieved by reusing concentrate and SADS in our studies were 1.49 g/L (D. Salina) and 1.98 g/L (S. platensis) that are comparable to that of literature data where sea water and pretreated sea water were used. Both species gain a negative net energy ratio. Energy content of 3.02–4.24 kJ/L is required for a positive net energy ratio in microalgae growth culture. Conductivities of growth mediums from all reactors in whichD. salinawere grown are less than the conductivity of drinking water quality required for sheep. Net energy ratio ofD. salinais less than that ofS. platensis. For conservative and reusable drinking water for sheep,D. salinawas used as microalgae to treat concentrate in our analyses. Energy usage and CO2emission saved from innovative integrated desalination were 4–14%. [ABSTRACT FROM PUBLISHER]

The conversion of biomass to four different outputs via gasification is a renewable technology that could reduce the use of fossil fuels and greenhouse gas (GHG) emissions. This study investigates the energy aspects for a new concept of biomass based quad-generation plant producing power, heat, methanol and methane. Circulating fluidized bed gasifier and the gas technology institute (GTI) gasifier technologies are used for this quad-generation process. Two different biomass feedstocks are considered in this study. The net energy ratio for six different pathways having the range of between 1.3 and 7.2. The lowest limit corresponds to the wood chips-based power, heat, methanol and methane production pathway using GTI technology. Since more efficient alternatives exist for the generation of heat and electricity from biomass, it is argued that syngas is best used for methanol production. The aim of this study was to evaluate the energy performance, reduce GHG and acid rain precursor emission, and use of biomass for different outputs based on demand. Finally, a sensitivity analysis and a comparative study ar conducted for expected technological improvements and factors that could increase the energy performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wintering cultivation of algae in artificial wastewater was investigated. [•] pH regulation could improve the nutrient removal and biomass productivity. [•] High lipid content and productivity were obtained by regulating pH. [•] Biodiesel yield in the pH-regulated group was 19.44% of dry weight. [•] It is efficient to grow C. zofingiensis in winter by pH regulation using acetic acid. [ABSTRACT FROM AUTHOR]

Microalgae have potential to yield various bioenergy products, including algal biodiesel. For algal energy production, the process energy input must be substantially lower than the product energy. Airlift photobioreactors provide controlled environments with good mixing and mass transfer; however, previous work reports a net energy ratio (NER; energy produced divided by energy consumed) less than 1. Here, the energy consumption in these reactors was improved by combined optimisation of superficial gas velocity and its CO 2 concentration. Increasing CO 2 concentration resulted in increased tolerance to lower superficial gas velocities, down to a critical minimum value. A 75% reduction in aeration power input was obtained by reducing superficial gas velocity from 0.0210 to 0.0052 m s − 1 at 5 400 ppm CO 2 , without substantial reduction in biomass concentration (2.27 to 1.93 g L − 1 , respectively) or productivity (0.189 to 0.173 g L − 1 d − 1 , respectively). The NER under these conditions was 5.47 for biomass plus lipid and 1.01 for lipid only. The CO 2 supply rate, product of superficial gas velocity and CO 2 concentration, correlated with the CO 2 transfer rate which influenced algal productivity. The range of NERs measured across the superficial gas velocities studied indicates the ability to optimise algal cultivation in photobioreactors for the improved feasibility of algal bioenergy. [ABSTRACT FROM AUTHOR]

Highlights: [•] 0.25gL−1 urea is the optima for biomass accumulation in D. abundans. [•] NaCl was outstanding of different salts (NaCl, NaHCO3, NaAc and NaS2O3) on lipid induction. [•] Higher lipid productivity was obtained during the optimized cultivation process. [•] 1.79gL−1 of biomass concentration was the time point for NaCl addition. [•] Strategy of NaCl addition for cultivating D. abundans was cost-efficient and net energy-positive. [Copyright &y& Elsevier]