Search

Editorial

Bio-oil and pyrolysis gas (py-gas) are two pyrolysis products available for potential energy recovery. Crude bio-oil, however, is typically corrosive and unstable, requiring special combustion equipment or catalytic upgrading to produce drop-in-grade fuel. In contrast, py-gas is readily useable in standard equipment for energy recovery. Previous research revealed that Ca-impregnated biochar catalyst improved bio-oil to py-gas conversion. Biochar produced from paper mill sludge (p-sludge) has very high Ca content. In this study, the catalytic ability of p-sludge biochar was systematically evaluated for the first time in pyrolysis. P-sludge biochar resulted in higher py-gas yield (40 wt% of total pyrolysis products) and py-gas energy (8400 kJ of py-gas per biosolids pyrolyzed) than other biochar catalysts (e.g. wood and corn stover biochars) and mineral catalysts (e.g. calcined dolomite). Under some conditions (e.g. high temperature and catalyst loading), catalysis completely eliminated the nonaqueous phase condensate. A lower catalyst-to-feedstock ratio was required using p-sludge biochar compared to other biochars for similar performance. P-sludge biochar also had a longer catalyst lifetime based on the effectiveness over five reuse cycles. Bio-oil catalyzed by p-sludge biochar contained fewer organic constituents based on GC-MS and GC-FID analyses (e.g. toluene, ethylbenzene, styrene, phenol, cresol, and indole were not identified after catalysis).

The present study investigates the effect on methane production from waste paper when co-digested with macroalgal biomass. Both feedstocks were previously mechanically pretreated to reduce their particle size. The study was planned according two factors: the feedstock to inoculum (F/I) ratio and the waste paper to macroalgae (WP/MA) ratio. The F/I ratios checked were 0.2, 0.3 and 0.4 and the WP/MA ratios were 0:100, 25:75, 50:50, 75:25 and 100:0. The highest methane yield (386 L kg−1 VSadded) was achieved at an F/I ratio of 0.2 and a WP/MA ratio of 50:50. A biodegradability index of 0.87 obtained in this study indicates complete conversion of feedstock at an optimum C/N ratio of 26. Synergistic effect was found for WP/MA 25:75, 50:50 and 75:25 mixing ratios compared with the substrates mono-digestion.

Increasing levels of variable renewable energy require additional flexible resources in the global energy system. In countries with energy-intensive industries, flexibility may be increased through industrial demand side management (IDSM). In most studies, the potential of IDSM is estimated from a technical or theoretical viewpoint. However, IDSM capacity is only utilized if the industry finds it profitable, and thus the economic potential should also be assessed. The focus of this paper is on the intra-day IDSM potential of a paper mill site that is active in the Nordic power market. An optimization model is built to estimate the costs that occur when the paper mill executes regulating power bids, if the original production schedule has been optimized against a spot price forecast. The costs are estimated for different sizes of bids and a marginal cost curve is provided for pricing them. Using this marginal cost curve, the market potential of the case mill site is assessed. It is found that this potential is greatly influenced by the costs of executing regulating power bids. The results indicate that transmission system operators and policy makers should account for economic factors when assessing the potential of market based IDSM.

This paper evaluates system aspects of biorefineries based on biomass gasification integrated with pulp and paper production. As a case the Billerud Karlsborg mill is used. Two biomass gasification concepts are considered: BIGDME (biomass integrated gasification dimethyl ether production) and BIGCC (biomass integrated gasification combined cycle). The systems analysis is made with respect to economic performance, global CO2 emissions and primary energy use. As reference cases. BIGDME and BIGCC integrated with district heating are considered. Biomass gasification is shown to be potentially profitable for the mill. The results are highly dependent on assumed energy market parameters, particularly policy support. With strong policies promoting biofuels or renewable electricity, the calculated opportunity to invest in a gasification-based biorefinery exceeds investment cost estimates from the literature. When integrated with district heating the BIGDME case performs better than the BIGCC case, which shows high sensitivity to heat price and annual operating time. The BIGCC cases show potential to contribute to decreased global CO2 emissions and energy use, which the BIGDME cases do not, mainly due to high biomass demand. As biomass is a limited resource, increased biomass use due to investments in gasification plants will lead to increased use of fossil fuels elsewhere in the system. Original Publication:Elisabeth Wetterlund, Karin Pettersson and Simon Harvey, Systems analysis of integrating biomass gasification with pulp and paper production - Effects on economic performance, CO2 emissions and energy use, 2011, ENERGY, (36), 2, 932-941.http://dx.doi.org/10.1016/j.energy.2010.12.017Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com/

The integration of different conversion technologies can strongly contribute to the biomass potential exploitation. To this aim, the use of intermediate pyrolysis biochar is analyzed in this paper as an alternative co-substrate in anaerobic digestion. The specie Ampelodesmos mauritanicus has been specifically chosen in this case for its capacity to tolerate, accumulate and, in some cases, degrade organic and inorganic pollutants. The biochar, produced under intermediate pyrolysis conditions at 450 °C, 500 °C and 550 °C, has been here considered for a biomethane potential assessment. The intermediate pyrolysis process improves the herbaceous bioavailability and promotes the microbial activity by reducing the digestion lag phase. Three reactors, namely B450, B500 and B550, have been considered in this study. Acclimatized cow manure from food wastes digestion has been used as inoculum with 5 g of biochar. The reactors have been continuously monitored for 15 days keeping the temperature fixed at 37 °C. Excluding the inoculum contribution, an accumulated methane production of 465–540.4 ml CH4/g-VS has been measured with an LHV evaluated in the range 25.8–26.9 MJ/kg. The modified Gompertz equation has been then used to describe the influence of biochar production temperature on methane conversion. A lag phase of 1.8, 2.2 and 3.8 days respectively for B450, B500 and B550, has been estimated showing an inverse proportionality to the biochar production temperature. The biomass to biogas energy conversion analysis reveals a reduction in the efficiency with the biochar production temperature increase. This fact is attributed to the steep reduction in volatile solids occurring by increasing the pyrolysis process severity. As a whole, the paper present a novel approach to possibly combine phytoremediation and production of renewable energy by using Ampelodesmos mauritanicus.

This study explored the optimization of pretreatment of pineapple peel for biogas generation. Pretreatments were carried out sulfuric acid and alkaline hydrogen peroxide prior to anaerobic digestion while the response surface methodology (RSM) was used for optimization of the pretreatment procedures. The physical, chemical, proximate and structural compositions of the peels were determined prior to and at the end of the pretreatment procedures. The dynamics of microorganisms in the reactors were also evaluated by rapid molecular methods while the Fourier Transform Infra-red (FTIR) spectroscopy was employed in the identification of the chemical changes as a result of pretreatments. The use of H2O2 pretreatment caused enormous lignin solubilization in the pineapple peel. In comparison, biogas production was 67% more in the alkaline pretreated pineapple peel than the biomass treated with acid and also 51% over the untreated samples. The total biogas volume produced from the acidic pretreated, alkaline pretreated, not sifted untreated and sifted untreated samples are 194.2 ± 3.0, 587.5 ± 5.2, 287.8 ± 2.1 and 245.4 ± 3.1 respectively. Thus, the alkaline pretreated experiment used lower retention time to achieve maximum gas production in this study. The use of alkaline H2O2 on lignocelluloses has remained unpopular prior to this study. However, its usage in this study yielded better result than all the conventional treatments in terms of lignin solubilization and improvement in methane yield. Economically, the use of H2O2 for pretreatment is adjudged feasible because the 1504 kWh t−1 TS thermal energy gain obtained from the biogas produced by the alkaline treated peel exceeded the 921 kWh t−1 TS used in the pretreatment. This gives a net thermal energy of 583 kWh t−1 TS. Whereas, the investment into acidic pretreatment of pineapple peel may not be economically justified because the total thermal energy gain of −200 kWh t−1 TS was far lower than the 1236 kWh t−1 TS thermal energy that was consumed during the pretreatment giving a net thermal energy of −1436 kWh t−1 TS. Therefore, the use of mild alkaline pretreatment is advocated in biogas generation from pineapple peel and also for biofertilizer production mostly in localities of mass production.

This research presents the results of statistical significance tests for evaluating the main effect of water-diesel emulsion usage (containing 2%, 5%, 8% and 10% by vol.) and engine load on the engine performance and emission parameters. To exclude inevitable random errors of measurements, the mean values of measured data were compared using Duncan's multiple range tests (MRT). The decrease in heating value and increase in fuel density and viscosity were observed with increasing water content. Although the fuel pour point decreased with water presence, but it didn't depend to water percentage. The combustion of emulsions significantly decreased the engine power and torque at 1% probability level (P

The interest in water-diesel emulsion fuel (EM) is increased recently because of the significant reduction in emissions from diesel exhaust, especially NOx and PM. In this study, a diesel engine configured for experimental investigations was fueled by ultra-low sulfur diesel (ULSD) and a diesel-water emulsion (EM). Both fuels’ combustion characteristics were studied at a speed of 1500 rpm and using a load of 2.5 and 5 bars and variable injection timings. Regular and irregular pollutants were studied at the same conditions as well as at variable engine loads and speeds to better understanding for their formation conditions. As for the first time (in the case of an engine running with a water-diesel emulsion) irregular pollutants for EM emulsion were measured. The measured results indicated that the use of water-diesel emulsion reduced the heat released in the combustion chamber, which causes an increase in the brake specific fuel consumption and ignition delay. For the tested loads, the diffusion combustion duration for EM was decreased when the injection timing was retarded while the opposite was occurred for premixed combustion duration. The regulated NOx and Smoke Number were reduced when EM was used compared to ULSD while CO and HC levels were increased at low engine’s speed and loads. Besides, these concentrations are depending on injection timing (they were higher at restarted timing). The unregulated emissions measured (Formaldehyde, Acetaldehyde, Methane, Acetylene, Ethylene, and propylene, Ammonia, and Acetone) were increased with using EM, especially at no and low loads, indicating the high impact of the combustion chamber temperature on these pollutants formation.

The stable H2 production is the important link in the anaerobic biohythane fermentation. In order to address the key parameters for the stable H2 production in the recirculated temperature-phased anaerobic digestion (R-TPAD) system, a critical strategy was proposed to adjust the recirculation ratio (R). The adjusting strategy was examined on a lab-scale R-TPAD system. The R-TPAD system was started up and operated with R = 1. Another system without recirculation (R = 0) was also operated as the control system. By narrowing the probable range from 0

A heat exchanger and vegetable oil bubbling system was designed and tested for biomass-generated syngas cooling and cleaning. The fully enclosed heat exchanger contained water at 15 °C, with syngas having to travel 35 m3/s. Using canola oil, the bubbler was tested at 70 and 100 mm oil depths and 5 and 10 mm syngas bubble sizes to determine the effect of tar removal. The results showed that tar removal efficiency was significantly affected by oil depth and bubble size; however, the interaction between bubble size and oil depth was not significant. About 60% of tars was removed by the heat exchanger alone and 96% of the remaining tars was removed by the oil bubbler when used in series with the heat exchanger. Overall, tar reduction efficiency of 98.5% was achieved with the heat exchanger plus oil bubbler having oil depth of 100 mm and syngas bubble size of 5 mm. Heat exchanger removed most of the tars by cooling the syngas below its dew point but syngas tars with low dew point was absorbed in the oil bubbler.

It is important to evaluate the utilization pathways of biomasses as there are different multiple choices for various types of biomasses. A method using the functional exergy efficiency as a unified protocol is proposed to evaluate the effectiveness of energy utilization in three utilization pathways of biomasses: pyrolysis, oxygen gasification and anaerobic digestion. The results show that straws are more suitable than manures used in the pyrolysis process. Functional exergy efficiencies of the oxygen gasification process of six biomasses are all higher than those of the pyrolysis process. The functional exergy efficiencies of the manures have increased, becoming close to those of straws. For the anaerobic digestion process, the functional exergy efficiencies of straws are generally lower than that of manures. Manures with low lignin content (chicken manure in this study) are more suitable as the feedstock of anaerobic digestion process. The functional exergy efficiencies of anaerobic digestion are lower than those of the pyrolysis and gasification processes while the temperature exceeds 850 °C.

In this study, the utilization of textile fibres as energy feedstock in the form of biochar was investigated depending on the fibre type. The biochars were produced from waste natural and synthetic fibres and its blends. For this purpose, different types of textile fibres (cotton, viscose, polyester, acrylic) and their blends (cotton/polyester, acrylic/wool, acrylic/polyester, acrylic/viscose) were torrefied at temperatures between 300 and 400 degrees C. The effects of torrefaction temperature and fibre type on biochar yield and biochar properties (fuel properties, morphological and structural properties and combustion characteristics) were investigated. The results showed that the temperature had a significant effect on biochar yield whereas the fibre type was the only significant factor on energy densification ratio and biochar properties. The torrefaction of tested fibres and blends resulted in an energy-intensive solid fuel, having a negligible amount of ash and sulphur. Although torrefied acrylic based textile fibres had similar H/C and O/C ratios to bituminous coal, it was concluded that high nitrogen contents will limit their usage as fuel. Overally, this study showed that torrefaction of cotton and cotton/polyester textile wastes is a promising process for the production of a solid fuel, which can be used as a substitute fuel in coal/waste co-firing systems. (C) 2018 Elsevier Ltd. All rights reserved.

By determining the methane production, volatile fatty acids (VFA) and ammonia nitrogen content of deer manure anaerobic fermentation system we explored the effects of adding biogas slurry on biogas production for the anaerobic fermentation of deer manure. The initial mushroom slag amount that was added was 35 g, total solid content was 6%, and temperature was 35 °C. One set of experiments was not added to the biogas slurry during the experiment, and for the other three groups, the amounts of biogas slurry that were originally added to the fermentation mixture were 10%, 30% and 50%. The results showed that the addition of biogas slurry during the fermentation of raw materials improved biogas total production and CH4 total production and also produced CH4 in advance. The total amounts of biogas and CH4 produced were the largest when the amount of biogas slurry added to the fermented mixture was 30%. Upon increasing the amount of biogas slurry, the trend of the VFA content in the fermented material first increased, then decreased and finally increased again. The content of VFA was the smallest when 30% biogas slurry was added to the fermented mixture because this was the most favorable condition for CH4 production.

In this research a hybrid thermochemical and biochemical approach is proposed to produce biocarbon, biomethane and biofertilizer from corn residue using the concept of resource recovery from biowaste. In this approach, corn residue is first pretreated in hydrothermal carbonization process to produce solid biocarbon. Hydrothermal process water, a co-product of hydrothermal carbonization process underwent fast anaerobic digestion to produce biomethane and biofertilizer. Effects of operating conditions (process temperature and residence time) on both biocarbon and hydrothermal process water contents were studied. Four selected hydrothermal temperatures of 200 °C, 220 °C, 240 °C and 260 °C and their three corresponding residence times of 10 min, 20 min and 30 min were considered. Among these 12 hydrothermal processes, 240 °C for 30 min process produced hybrid bioenergy of 14.26 MJkg−1 of raw corn residue with an overall energy yield of 78.65%. Biocarbon produced at 240 °C for 30 min and 260 °C for 10–30 min were comparable to pulverized coal used in power plants, which contained high heating values of 23.01 MJkg−1 to 24.70 MJkg−1. All anaerobic digestion digestate are nutrient enriched and useable as liquid fertilizer.

In this study, valorisation of high acid value waste cooking oil into biodiesel has been investigated. Non-catalytic transesterification using supercritical methanol has been used for biodiesel production. Four controllable independent process variables have been considered for analysis including methanol to oil (M:O) molar ratio, temperature, pressure and time. Uncommon effects of process variables on the reaction responses, e.g. biodiesel and glycerol yields, have been observed and extensively discussed. Response surface methodology (RSM) via Central Composite Design (CCD) has been used to analyse the effect of the process variables and their interactions on the reaction responses. A quadratic model for each response has been developed representing the interrelationships between process variables and responses. Analysis of Variance (ANOVA) has been used to verify the significance effect of each process variable and their interactions on reaction responses. Optimal reaction conditions have been predicted using RSM for 98% and 2.05% of biodiesel and glycerol yields, respectively at 25:1 M:O molar ratio, 265oC temperature, 110 bar pressure and 20 minutes reaction time. The predicted optimal conditions have been validated experimentally resulting in 98.82% biodiesel yield, representing 0.83% relative error. The quality of the produced biodiesel showed excellent agreement with the European biodiesel standard (EN14214).

The environmental load of continuous bioenergy production from palm oil (Elaeis guineensis) included with a proposed 10 ha of microalgae production system were assessed to be implemented in Indonesia. Material and energy balances, greenhouse gas (GHG) emission, nutrient requirement and also water scarcity during bioenergy production cycle were evaluated. The integrated system was developed for 60 tons h−1 of fresh fruit bunch (FFB) processing capacity of a conventional mill. Aggregate of energy-profit ratio from the proposed system was 5.20, which indicates a positive balance. The total water footprint for each palm oil and microalgae cultivation was 3.18 and 2.85 m3 kg−1 of biodiesel production, respectively. Microalgae mix-culture has the potential to treat organic compounds from palm oil mill effluent (POME) and combined with flue gases from biomass and biogas power plant as the alternative nutrient sources contributed to net-reduction of GHG emission for 158.8 tons ha−1 of microalgae culture, annually. The integrated system produced 26,471 tons of biodiesel that included 223 tons from microalgae and contribute to 39.90% of total GHG emission reduction from diesel fuel substitute. Additional co-product of 520.33 tons year−1 of animal feed from defatted biomass also possible to be produced and have potential for environmental benefits.

Reserves of fossil fuel are being depleted, and its use to generate energy also affects the environment. Sustainable and clean energy sources, therefore, need to be produced to meet the demands. In this research, combined blended fuels were produced from cottonseed and palm oil methyl esters with petroleum diesel fuel. To achieve the benefits of palm oil biodiesel (high calorific value) and cottonseed oil biodiesel (low kinematic viscosity and acid value), the combined biodiesel blend (C05P15, C10P10, and C15P05) has been tested to assess their effect on engine performance, emissions, and tribological properties. The physicochemical properties of all fuels were measured following ASTM D6751 standard. A single-cylinder, 4-stroke, and the natural aspiration diesel engine were used for engine testing. The experimental results showed that all combined blended fuels have low brake thermal efficiency and emitted fewer hydrocarbons, carbon monoxide, and smoke opacity apart from nitrogen oxides compared with petroleum diesel fuel. Based on results, the combined blended fuel can be used as a substitute fuel in diesel engines without any engine modifications.

Herein, we report on a combined process that incorporates hydrothermal liquefaction (HTL) and supercritical water gasification (SCWG) to improve energy recovered from algal biomass. Eight algal biomasses, including four microalgae and four macroalgae with a large difference in biochemical compositions, were screened for this dual process. The algal biomass feedstocks significantly affected the carbon and energy distribution in the product fractions (crude bio-oil, solid, gas, and water-soluble products). 62.50–71.34% energy of microalgae and 6.03–41.06% energy of macroalgae could be recovered as crude bio-oil. 11.86–21.55% carbon of the microalgae and 8.01–15.82% carbon of the macroalgae was distributed in the HTL process water in form of water soluble products after the HTL process. 14.3–33.7% energy of microalgae and 30.18–36.34% energy of macroalgae was retained in the HTL process water. SCWG could convert the organics in the HTL process water into fuel gases consisting mainly of H2 and CH4. 54–91% carbon of the HTL process water was transformed into the fuel gases, which correspond 5.53–18.30% energy of the algal biomass. Thus, this work shows that the integration of HTL and SCWG could improve energy recovery from algal biomass relative to the HTL process alone.

The economic feasibility of a facility producing jet fuel range cycloalkanes, hydrogen and biochar via microwave-assisted catalytic pyrolysis integrated with mild hydrogenation was evaluated by modeling a 1000 metric dry tonne feedstock/day using ASPEN PLUS®. The effects of hydrogenation solvent, heat integration, and coproducing H2 or syngas were investigated in different analysis scenarios. The results indicated that the production of jet fuel could reach 47882.74 Gallon/day, with 9.58 Metric tonne/day biochar and 28200 kg/day H2 as coproducts. The lowest minimum selling price of 3.78 $/Gallon was obtained when using n-hexane as the hydrogenation solvent and coproducing H2 with heat integration. The sale of H2 offset the high production cost, resulting in a significant decrease in the minimum selling price. Sensitivity analysis indicated that the production process was greatly sensitive to total capital investment, internal rate of return, market prices of feedstock and H2.

An alternative to the sugar/starch-based crops bioethanol is lignocellulosic biomass, but its utilization to biofuels is still not economically viable. In this context, an increasing interest has arising on the search for specific energy crops that do not require arable lands and are not water intensive, such as Jerusalem artichoke (JA). So, this work consisted on the cultivation of JA on those agricultural conditions and its further evaluation as a sustainable feedstock towards bioethanol. Two strategies of producing bioethanol were evaluated pointing out for the consolidated bioprocessing with the Zygosaccharomyces bailii Talf1 yeast as the best approach for further scale-up, based on energy data analysis and ethanol productivity. Different industrial scenarios were outlined and compared for overall CO2eq emissions and energy consumption per liter of ethanol (LEtOH), using adequate criteria on a cradle-to-gate approach. With no land-use change, no biogenic and no co-products credits, the comparison of the overall energy consumption and CO2eq emissions (100% process) from JA ethanol (9 MJ/LEtOH; 679 g CO2/LEtOH) with sugarcane/sugar beet ethanol (42/29 MJ/LEtOH; 731/735 g CO2/LEtOH) and with gasoline refinery (15 MJ/LEtOH eq; 1154 g CO2/LEtOH eq), highlights the JA as an alternative feedstock to be a focus of ethanol research for gasoline blends.

The pyrolysis of food waste has a double environmental advantage as it contributes to the management and treatment of waste and allows the production of renewable fuels. Spent coffee and tea grounds, were characterized by thermogravimetry to determine their composition and evaluating the pyrolysis kinetics of each lignocellulosic pseudocomponent and pyrolyzed in a fixed bed reactor. Tea grounds had about twice the cellulose and higher pyrolysis activation energy than the coffee grounds sample. At 673 K the pyrolysis of the coffee grounds led to a 42% bio-oil yield while the tea grounds produced only 18% of liquid product, which is compatible with its higher cellulose content and the higher activation energy for pyrolysis. The alkaline carbonates used as pyrolysis catalysts led to an increase in the production of a gaseous product, bio-gas, with a reduction in the production of bio-oil but accompanied by a significant increase in the volatile fraction of the produced bio-oils. Pyrolysis data shows that both coffee and tea residues can be used as raw materials to produce pyrolysis bio-oil and that low-value materials such as alkaline carbonates can be used as pyrolysis catalysts improving the characteristics of bio-oils produced such as acidity and volatility.

Microbial fuel cell (MFC) technology allows renewable energy production from the decomposition of organic matter present in wastewater. This technology, however, poses challenges that hinder scaling up of its usage in practical implementation. Also, resource recovery from the available waste sources is attracting attention due to the immense amount of valuable nutrients present in the wastewater. Herein, the present study focuses on investigating high-performance anodes, that is, using a stainless-steel brush (SSB) and carbon brush (CB) to accommodate the MFC in terms of energy production, leading to transformation into a microbial nutrient recovery system (MNRS) for nutrients’ recovery from wastewater. The present novel SSB anode system generated a stable voltage of ∼0.4V and a maximum power density of ∼400 mW/m2 whereas CB anode system produced the voltage and maximum power density of ∼0.5 V and ∼800 mW/m2, respectively. Besides, using the MNRS process, recovery of nutrients in terms of PO43− (80–83.4% for CB-MNRS and 60–69.5% for SSB-MNRS when using feed PO43− concentration of 10–20 ppm) and NH4+ (63–80.64% for the CB-MNRS and 52–70% for the SSB-MNRS when using feed NH4+ with a concentration of 10–20 ppm) was achieved.

Current studies have employed various chemicals for disintegrating and hydrolyzing microbial cells in waste activated sludge (WAS). However, a comprehensive process assessment over the whole anaerobic digestion process has seldom been proposed. Besides, the characterization of microbial community responses to these chemicals is not well understood. In this study, the effects of five typical chemicals: solubilizer (β-cyclodextrin, CD), alkaline (NaOH), peroxide (peracetic-acid, PA), biological (rhamnolipid, RL) and chemical (sodium dodecylsulphate, SDS) surfactants on WAS digestion were examined. Higher efficiencies of WAS solubilization, hydrolysis and acidification were achieved by CD treatment, followed by RL and SDS. Methanogenesis was also strongly chemicals-dependent. Shifts in microbial community structure were observed in all chemical-pretreated WAS. The community in RL, CD and PA was dominated by microorganisms that anaerobically hydrolyze organics to acids, while that in NaOH and SDS was mainly associated to biogas production. This study proved that the overall performance of WAS digestion was substantially depended on the initial chemical pretreatments, which in turn influenced and was related to the microbial community structures. Although the economic advantage might not be clear yet, the findings obtained in this work may provide a scientific basis for the potential implementation of chemicals for WAS treatment.

The integration of anaerobic digestion and thermal gasification can ensure a high biomass utilization, as the unconverted biomass from digesters can be converted by thermal gasification. When integrating steam electrolysis or co-electrolysis, all the CO and CO2 in the biogas and gasification gas can be upgraded to synthetic natural gas (SNG), achieving a very high bio-SNG yield per biomass input. In this paper, a highly integrated system combining anaerobic digestion, thermal gasification, and pressurized solid oxide cells for bio-SNG production from manure is presented and analyzed by thermodynamic modeling. The system is compared to a similar system without anaerobic digestion. The analysis finds that the energy yield of bio-SNG can reach 138% in relation to the manure input (LHV-dry), while the yield drops to 107% without anaerobic digestion. The total energy efficiency from manure and electricity to bio-SNG can reach 79% with anaerobic digestion and 64% without it. By combining thermal gasification and anaerobic digestion, it is thereby almost possible to reach the same efficiency as a thermal gasification system operating on wood (up to 84%).

H2 production from biogas (60%CH4 + 40%CO2) by sorption enhanced steam reforming (SESR) was thermodynamically and experimentally studied in a fluidized bed reactor. Biogas is an interesting renewable biomass resource for hydrogen production due to its sustainable nature. SESR combines the catalytic reforming reaction of biogas with simultaneous CO2 removal in a single step. A Pd/Ni–Co hydrotalcite-like material (HT) was used as catalyst and dolomite as CO2 sorbent. The effects of temperature (550–800 °C), steam/CH4 molar ratio (2–6) and gas hourly space velocity (GHSV) (492–3937 mL CH4 gcat−1 h−1) on the process performance were evaluated. CO2 in biogas was effectively removed by the sorbent from the gas phase at 550–700 °C, without influencing the reforming process. H2 yield increased with temperature from 550 to 650 °C, but H2 concentration decreased at temperatures higher than 600 °C, requiring a tradeoff between both parameters to select an optimum operating temperature. H2 purity of 98.4 vol% was obtained at 550–600 °C and H2 yield of 92.7% was reached at 650 °C. Higher steam/CH4 ratios enhance the process, whereas higher space velocities decrease H2 yield. Results demonstrate that high-purity high-yield biohydrogen can be produced by the SESR of a renewable biomass resource as biogas., The authors thank Franefoss Miljøkalk A/S (Norway) for supplying Arctic dolomite. This work was carried out with financial support from the Spanish MICINN (Project ENE2017-83530-R) and from the Gobierno del Principado de Asturias (PCTI, Ref. IDI/2018/000115), both co-financed by the European Regional Development Fund (ERDF). M.V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish Government, co-financed by the European Social Fund (ESF).

Efficient conversion of all components in lignocellulosic biomass is essential to realizing economic feasibility of biorefineries. However, lignin cannot be fermented using biochemical routes. Furthermore, high lignin and high ash residues from simultaneous saccharification and fermentation (SSF) is difficult to thermochemically process due to feed line plugging and bed agglomeration. In this study a corn stover SSF digester residue was thermally pretreated at 300 °C for 22.5 min and gasified in a fluidized bed gasifier to study the effect of thermal pretreatment on its processing behavior. Untreated, pelletized SSF residue was gasified at the same conditions to establish the baseline processing behavior. Results indicate the thermal pretreatment process removes a substantial portion of the polar and non-polar extractives, with a resultant increase in the concentration of lignin, cellulose, and ash. Feed line plugging was not observed, although bed agglomeration occurred at similar rates for both feedstocks, suggesting that overall ash content is the most important factor affecting bed agglomeration. Benzene, phenol, and polyaromatic hydrocarbons in the tar were present at higher concentrations in the treated material, with higher tar loading in the product gas. Total product gas generation is lower for the treated material, although overall gas composition does not change.

The European Commission opened a discussion about limiting first generation food based biofuels in favour of advanced biofuels. The main reason was to limit the uncertainty in estimates of indirect land use change emissions (ILUC) of food based biofuels. Brown seaweeds represent a valuable solution. The lack of lignin makes them suitable for degradation processes such as anaerobic digestion (AD). The main output of AD is biogas which can be upgraded to biomethane and used as a transport fuel. The most common Irish brown seaweeds namely Laminaria sp. and Ascophyllum nodosum were subject to AD. The effects of beating pretreatment time (5–10–15 min) and changes in the seaweeds volatile solids (VS) concentration (1–2.5–4%) on methane production were investigated through a response surface methodology (RSM). Laminaria sp. showed the highest methane yield of 240 ml CH 4 g −1 VS when the pretreatment time was set at 15 min and at VS concentration of 2.5%. In the case of Ascophyllum nodosum , the best yield of 169 mL CH 4 g −1 VS was found at the longest pretreatment time tested and at the minimum concentration of VS. The RSM analysis revealed that the VS concentration had the strongest impact on the methane yield.

The major concern of recycling anaerobic digestion (AD) effluent in the digester centers on accumulation of total ammonia nitrogen (TAN) and salinity, both of which can potentially inhibit methane production. In the current study, 30%, 50%, and 80% of separated-liquid AD effluent, were recycled in a series of batch AD experiments. The inhibitions to specific methane potential (SMP) caused by TAN and salinity were evaluated. Recycling up to 80% of un-treated effluent resulted in the best SMP averaging 0.265 ± 0.005 m 3 [CH 4 ] Kg −1 [volatile solids], which averaged 10% more compared to recycling 80% treated effluent and 5% more compared to no recycling (the control). After acclimation, up to 6.39 g N L −1 increase in TAN resulted in SMP averaging 0.112 ± 0.002 m 3 [CH 4 ] Kg −1 [volatile solids] and up to 12 parts per thousand increase in salinity resulted in SMP averaging 0.163 ± 0.005 m 3 [CH 4 ] Kg −1 [volatile solids]. A mass balance for a hypothetical 5000 cows dairy farm showed effluent recycle of up to 66% for maintaining 8% solids in anaerobic digester. Moreover, in the proposed system, the effluent going off-farm was on w/w basis 64% less water, 66% less solids, and 52% less nitrogen compared to the effluent produced with no recycle facility.

The kinetics of the acidogenic phase during anaerobic digestion of sugarcane vinasse in differential reactors containing immobilized cells was investigated. The maximum substrate conversion rate (r max ), substrate saturation constant (K s ) and constant of inhibition by excess substrate (K is ) were determined using vinasse with and without pH adjustment. Simulation and scaling-up of a thermophilic-hydrogen production system were performed. The r max values obtained at different pH were similar and near 0.9 mg-Total carbohydrates g-VS −1 h −1 . The K s obtained from the system without pH adjustment was 10,762.3 mg-Total carbohydrates L −1 (i.e., 2.5 times higher than the system with pH adjustment). No inhibition by excess substrate was achieved in the system without pH adjustment, indicating that sugarcane vinasse can be used to produce hydrogen without input costs. The simulation revealed that hydrogen production is a sensitive process that requires careful balancing of various operational parameters. The payback for the investment in system implementation is 4.4 years.

The exergetic performance of beer produced by the conventional malting and brewing process is compared with that of beer produced using an enzyme-assisted process. The aim is to estimate if the use of an exogenous enzyme formulation reduces the environmental impact of the overall brewing process. The exergy efficiency of malting was 77%. The main exergy losses stem from the use of natural gas for kilning and from starch loss during germination. The exergy efficiency of the enzyme production process ranges between 20% and 42% depending on if the by-product was considered useful. The main exergy loss was due to high power requirement for fermentation. The total exergy input in the enzyme production process was 30 times the standard chemical exergy of the enzyme, which makes it exergetically expensive. Nevertheless, the total exergy input for the production of 100 kg beer was larger for the conventional process (441 MJ) than for the enzyme-assisted process (354 MJ). Moreover, beer produced using enzymes reduced the use of water, raw materials and natural gas by 7%, 14% and 78% respectively. Consequently, the exergy loss in the enzyme production process is compensated by the prevention of exergy loss in the total beer brewing process.

Used creosote-treated wood ties were thermally treated between 250 and 350 °C to recover preservative and upgrade the wood to provide an improved quality biomass for thermochemical processes. With thermal treatments ranging from 250 to 300 °C, the amounts of creosote, mostly consisting of polycyclic aromatic hydrocarbons (PAHs), recovered were from 47 to 79% of total creosote present in the used ties. Thermal treatment at 350 °C recovered 97% of total PAH compounds. Larger amounts of PAHs with higher molecular weights (HMWs) and lower vapor pressures (LVP) were recovered at elevated temperatures. Temperature above 300 °C decomposed the wood matrix, with a mass loss ranging between 50 and 63 wt% and produced large amounts of light organics, anhydrosugars, and phenolic compounds that would contaminate the recovered creosote. Our study concluded that thermal treatment ranging between 275 and 300 °C would be preferred to recover preservative for recycling and improve the wood quality, i.e., high carbon content and caloric value, and low hazardous pollutants (creosote residues) for thermochemical processes such as pyrolysis or gasification. These findings suggest that the proposed approach could be a commercially viable and environmentally beneficial alternative to landfill for used railroad ties.

Byproducts from a photocatalytic pretreated model lignin chemical, sodium LS (lignosulfonate), was used to produce electricity in SCMFCs (single chamber microbial fuel cells). Pretreating LS was performed using TiO 2 -UV photocatalysis. Optimization and modeling of the photocatalytic degradation process was performed using the Box-Behnken design method to achieve a maximum BOD 5 to COD ratio. LC-MS (Liquid chromatography–mass spectrometry) analysis was conducted to identify compounds produced from the photocatalysis of LS. The biofilm microbial diversity and performance of SCMFCs fed PrLS (pretreated LS) was compared to SCMFCs fed glucose at the same COD loadings and operating conditions. The PrLS fed SCMFCs, operated at 37 ± 1 °C, generated maximum current and power densities of 6556 ± 360 mA m −3 and 1881 ± 103 mW m −3 , respectively. The corresponding maximum current and power densities normalized to the cathode area were 868 ± 48 mA m −2 and 248 ± 14 mW m −2 , respectively. The SCMFCs removed 77.6 ± 2.3% of the COD of the PrLS and achieved a coulombic efficiency of 17.7 ± 1.2%. This study demonstrated the effectiveness of photocatalysis coupled with a bioelectrochemical system in treating lignin compounds and simultaneously generate electricity.

This study focuses on the production and characterisation of fast pyrolysis bio-oil from hardwood (Populus) and softwood (Spruce) using a bench-scale pyrolysis reactor at two different temperatures. In this study, a mixed solvent extraction method with different polarities was developed to extract different components of bio-crude oil into three fractions. The obtained fractions were characterized by using gas chromatography and mass spectrometry (GC-MS). The effect of temperature on the production of bio-oil and on the chemical distribution in bio-oil was examined. The maximum bio-oil yield (71.20%) was obtained at 873 K for bio-oil produced from softwood (Spruce). In contrast, at a temperature of 773 K, the bio-oil yields were 62.50% and 65.40% for bio-oil obtained from hardwood (Populus) and softwood (Spruce) respectively. More phenolic compounds were extracted at a temperature of 773 K for bio-oil derived from softwood (Spruce) whereas the bio-oil obtained from hardwood (Populus) produced mostly furans, acids and sugar compounds at this temperature. For both types of bio-oil, a wide variety of chemical groups were identified at a temperature of 873 K in comparison to 773 K.

The recycling of low-cost resources from waste biomass is a promising strategy towards circular bioeconomy. Food waste is an ideal candidate to produce cost-effective glucose. However several problems such as insolubility of macromolecular substances hindered the valorization of food waste. To recover reducing sugar efficiently, a two-stage enzymatic hydrolysis platform was developed, where the alpha-amylase was used at the first stage and glucoamylase followed. Results showed that the enzymatic hydrolysis was more efficient in comparison with acidic and alkali hydrolysis. The optimum pH and dosage for alpha-amylase and glucoamylase were determined to be 5.5 and 150 U/g total solid (TS), and 4.0 and 150 U/g-TS, respectively. The hybrid hydrolysis was more effective in catalyzing starch, obtaining the highest reducing sugar concentration of 204.2 g/L. Analysis of the physicochemical structures indicated that the solid particles could be broken thoroughly by the two enzymes, resulting in sharp decrease of the particle size and viscosity compared with the control. The mass balance and economic assessment verified the feasibility and profitability of the two stage enzymatic hydrolysis. The features of the two-stage platform widened the door to the further production of value-added biochemicals using the sugars recovered from food wastes.

This study aims to assess the torrefaction of biomass as alternative renewable energy fuel to coal during co-firing. It was evaluated that torrefaction improves biomass grindability to such an extent that it can be used in coal mills with coal in co-firing without capital intensive modification. Torrefaction of beech wood was performed on a batch scale reactor at three different temperatures (200, 250 and 300 °C) with 30 min of residence time. The chemical structural changes in torrefied biomass were investigated with binding energies and FTIR (Fourier transform infrared) analysis. Monocombustion and co-combustion tests were performed to examine the combustion behaviour regarding flue gas emissions (CO, NOx and SO2) at 0.5, 1.5 and 2.5 m distance from the burner opening along with fly ash analysis. The FTIR and binding energies showed that lignin hardly affected during light torrefaction while hemicellulosic material was significantly depleted. The Hardgrove grindability index (HGI) was calculated with three methods (DIN51742, IFK and ISO). The medium temperature torrefied biomass (MTTB) yields HGI value in the range of 32–37 that was comparable with HGI of El Cerrejon coal (36–41). A slight change in temperature enabled the torrefied beech wood to be co-milled with coal without capital intensive modification and improved grindability. Comparing the combustion behaviour of single fuels, low temperature torrefied biomass (LTTB) produces less amount of NOx (426 mg/m3), CO (0.002 mg/m3) and SO2 (2 mg/m3) as compared MTTB and raw beech wood. In the case of co-combustion, it was found that blending of coal with raw biomass does not show a stable behaviour. However, premixing of 50% of coal with 50% of torrefied biomasses (MTTB and LTTB) gives most stable behaviour and reduces NOx almost 30% and SOx up to almost 50% compared to coal. The fly ash contents analysis proved that K2O contents much decreased during co-firing of coal and torrefied fuels that could cause ash related issues during combustion of raw biomass.

Pretreating biomass prior to pyrolysis was investigated. Three undesirable catalysts naturally present in biomass were identified: inorganics, acids, and water. A pretreatment sequence incorporating acid leaching and torrefaction was developed to reduce/remove these catalysts. Acid leaching targeted reducing the biomass's inorganic content. The acidic liquor produced during torrefaction was rich in acetic and formic acid; this solution was recycled as the acid leaching reagent. The optimal leaching conditions were at 30 °C with 1% acetic acid for 4 h, which decreased the inorganic content from 0.41 wt% to 0.16 wt% for leached biomass. Torrefaction targeted reducing the biomass's moisture and acetyl content and was optimal at 270 °C for 20 min. Bio-oil from pyrolysis of demineralisation and torrefied biomass was depleted in organic acids, pyrolytic lignin, and water but was rich in levoglucosan and aromatics. Decreasing the biomass's acetyl and inorganic content reduced organic acid formation. The water content in the bio-oil was lower because less water entered the system, and water plays an auto-catalytic role during pyrolysis, promoting the production of pyrolytic water. The high levoglucosan yield confirmed that secondary reactions were limited to a much higher degree when both pretreatments were implemented compared to demineralisation or torrefaction alone.

In this work, a cooperative algal-bacterial system that efficiently upgrade biogas, simultaneously reduce the biogas slurry nutrient, and exhibits high biomass productivity, was developed. The method about removing H2S and CO2 from biogas by three microalgal strains (Chlorella vulgaris, Scenedesmus obliquus, and Neochloris oleoabundans) mixed with activated sludge using biogas slurry as nutrient medium. A CO2 concentration of 45% (v/v) was considered optimum to support CO2 and H2S removals of 74.11%–80.57% and 99.04%–99.42%, respectively. At the CO2 concentration of 45%–55%, the mixed culture containing S. obliquus and C. vulgaris efficiently removed COD (chemical oxygen demand) and TP (total phosphorus), respectively. The mixed culture containing S. obliquus demonstrated high N removal efficiency at CO2 concentration of 45%. Biomass productivity increased at increasing CO2 concentration in a certain range, with a maximum of 0.177 g L−1 d−1 at CO2 concentration of 45% (v/v) for the mixed culture containing S. obliquus, whereas the C, N, and P biomass contents remained constant at 46.73%–52.31%, 7.59%–9.08%, and 0.91%–1.08%, respectively. This study showed the potential of the combination of alga and bacteria to serve as a treatment for nutrient removal and biogas upgrading in algal-bacterial processes.

Torrefaction is a thermal pretreatment leading to the improvement of most of the fuel properties of biomass, namely energy density, HHV (higher heating value), grindability and hydrophobicity. The aim of this study is to identify the most feasible temperature to carry out torrefaction of Eucalyptus globulus and nitens , based on chemical evidences associated to the release of volatiles during thermal treatment of biomass. With that end: (i) Devolatilization kinetics, (ii) Effects of temperature and residence time and (iii) volatiles composition during torrefaction of both wood and bark were analyzed. In all cases DTG (derivative thermogravimetric curves) exhibited the typical shape of lignocellulosic materials, with three decomposition phases and two reaction zones. Values of activation energies for hemicellulose decomposition, were in agreement with those reported in the literature (121–170 kJ/mol). Carboxylic acids, water and phenolic compounds showed two peaks, which were associated to torrefaction (below 310 °C) and pyrolysis (310–410 °C) respectively. The most feasible temperatures for torrefaction were estimated as a function of these peaks, and it ranged between 295 °C and 310 °C for all samples. Main volatile species at the torrefaction peaks were distributed as Water > Acetic Acid > CO 2 > Others, while Levoglucosan formation was marginal, due to the catalytic effect of inorganics.

International audience; The behavior of biomass in torrefaction is determined by that of its macromolecular components, as well as by the biomass type. However, up to now, commercial compounds were typically used for modelling biomass torrefaction. This work proposes to assess the behavior of cellulose, hemicelluloses and lignin in torrefaction through extracted fractions directly isolated from woody and agricultural biomasses (ash-wood, beech, miscanthus, pine and wheat straw) thanks to an optimized extraction procedure. The solid kinetics of these extracted fractions were analyzed through thermogravimetric analysis (TGA) in chemical regime conditions (200–300 °C at 3 °C·min−1 followed by 30 min at 300 °C). These experiments highlighted the influence of the biomass type and the sugar composition in the degradation of the polysaccharide fractions in torrefaction, particularly for hemicelluloses. Furthermore, the degree of preservation of the native structure of the macromolecular components, when extracting them from biomass, seems also having an impact their behavior, especially for cellulose. The comparison of the torrefaction solid kinetic profiles of these extracted fractions, dependent on the biomass type, to that of commercial compounds from previous studies suggest that these extracted fractions would be more suitable for biomass torrefaction modelling.

This article analyzes the potential for electric power generation and cost from commonly disposed Empty Fruit Bunches (EFB) from palm oil mills. To identify the best options, 40 plant configurations and two turbine configurations were simulated: Backpressure Turbine (BPT), Condensing-Extraction Turbine (CET); four types of EFB pretreatment: EFB Crude; EFB W/M; EFB D/M; EFB P; and five gas temperatures generated in the boiler (320 psig/320 °C; 320 psig/400 °C; 400 psig/450 °C; 600 psig/450 °C; 900 psig/500 °C). Results showed that configurations with the CET and steam at high pressure (>400 psig) with EFB type D/M produced the most energy. Generation with raw and pelletized EFB generated low amounts of energy due to vaporization heat requirements and energy consumption by peripheral equipment, especially with the BPT. CET configurations had the lowest levelized cost of energy (LCOE) at 390 COP/kWh, which is close to the average energy price around Colombian palm mills. Initial cost estimates showed that CET with high pressure steam at weighted energy price >230 COP/kWh are currently profitable (NPV > 0). Commercialization of energy obtained from low pressure steam is only calculated to be profitable when the price of electricity is > 320 COP/kWh.

The phase-out of fossil fuels in the heavy transportation sector will require energy-dense biofuels like methanol, and will likely require that a wide range of biomasses are utilized. In this framework, gasification of straw and subsequent upgrading to methanol represents a potentially advantageous conversion route. In this study, the established low-temperature circulating fluid bed (LTCFB) gasifier is coupled to a partial oxidation (POX) and char bed reactor, which enables a relatively robust and effective conversion of tars - making the product gas suitable for methanol synthesis. Five scenarios producing methanol via traditional air-separation units and electrolysis were thermodynamically modeled and analyzed in Aspen Plus. The analysis showed state-of-the-art biomass-to-methanol energy efficiencies up to 54–56% and overall carbon conversions above 57%. A parametric analysis on the POX temperature revealed the potential to increase efficiency and the carbon conversion up to 58% and 68%, respectively. The proposed systems outperform alternative systems framed on straw gasification, and exceed in terms of efficiency and overall carbon conversion other solutions based on wood-gasification.

© 2019 This study conducted a life cycle assessment of palm oil mill effluent (POME) based energy generation using the CML 2001 method and Gabi 8 software, focusing on two POME treatment technologies: the covered lagoon bio-digester (CLB) and the continuous stirred tank reactor (CSTR). The analysis determined the respective environmental impacts of the technologies, both of which are currently in use in Malaysia. The global warming potential (GWP) and acidification potential (AP) for CSTR were −4.48 kg CO2 eq/kWh and −2.21 kg SO2 eq/kWh respectively, while for CLB the values were −4.09 kg CO2 eq/kWh and −0.15 kg SO2 eq/kWh. Both technologies produced a negative result, which equates to a net environmental benefit. However, both systems had a negative impact in terms of eutrophication potential (EP). The CSTR nevertheless achieved a better EP result of 0.048 kg PO43− eq/kWh than the CLB with 0.054 kg PO43− eq/kWh. A sensitivity analysis was carried out in order to find a way to overcome the impacts of EP. The findings provide useful data to guide decision-makers in the sustainable management of POME, in Malaysia and globally where similar technologies are in use.

Direct fermentation of cellulosic biomass to bioethanol has been very promising and hence attracted attention in recent years. In this study, bioethanol production from apple pomace hydrolysate (agro-industrial waste product) was investigated by coculturing Trichoderma harzianum , Aspergillus sojae and Saccharomyces cerevisiae using statistical approaches. Screening and optimization experiments were conducted in order to determine the significant factors and their optimum levels for maximum bioethanol production. Inoculation rates, aeration and agitation speed were considered as factor variables and bioethanol production as response variable. Highest bioethanol (EtOH) concentration and ethanol yield on total reducing sugar content (Y P/S ) were 8.748 g/L and 0.945 g/g, respectively. Optimum conditions were 6% (w/v) inoculation rates of T.harzianum and A.sojae , and 4% (v/v) inoculation rate of S.cerevisiae with vented aeration method and agitation speed of 200 rpm. To best of our knowledge to date, no reports are available in literature regarding the coculturing of T.harzianum , A.sojae and S.cerevisiae for bioethanol production. Therefore, this study will serve as a base line of initial studies in this field. The method can create a renewable alternative feedstock for fossil fuel production and suggest a feasible solution to multiple environmental problems simultaneously creating a sink for waste utilization.

Bio-oils produced from fast pyrolysis of renewable energy feedstocks are chemically complex organic liquids that contain over 200 different organic compounds. Many of these compounds are oxygenates which result in 40–45% oxygen content in the bio-oils. Due to this high oxygen content bio-oils have numerous negative properties that include low heating value, high acidity, high water content and variable viscosity. It is universally agreed that for production of a viable fuel pyrolysis bio-oils must be upgraded. Esterification is a viable means to produce a boiler fuel but maximum heating energies remain rather low and amount of alcohol usually added is uneconomic. In this study we tested oxidative pretreatment prior to esterification as a means to both increase heating energy and decrease the amount of alcohol required. The most effective oxidative pretreatment was with application of a combined ozone/H2O2 treatment. The esterification of the ozone/H2O2 pretreated product produced a boiler fuel with improved yield and better physical/chemical properties compared to direct esterification of bio-oil. As compared to the product from direct esterification of bio-oil the esterified ozone/H2O2 pretreated bio-oil provided a 23% increased boiler fuel yield of 48 wt%; higher heating value was 5.7% higher at 35.3 MJ/kg.

Cell walls and lignin component disruption treatments are needed to enhance the hydrolytic phase and the overall biodegradability of lignocellulosics during an anaerobic digestion process. Given their abundant availability in nature, low impact on food market prices and low lignin content, aquatic plants result in being particularly suitable for biofuel conversion. A preliminary study on the effects of a Hollander beater mechanical pretreatment has been conducted in batch mode focusing on biogas yields from five different species of Irish seaweeds in co-digestion with sludge. A second experiment on Laminaria Digitata species has been carried out using a ResponseSurface Methodology (RSM) with treatment times (0-10min), mesophilic range of temperatures (35-39°C) and sludge amounts (100-300ml). Results from biogas yields of treated macroalgae have been found to be up to 20% higher when compared to untreated ones. A mathematical model of the biogas volume behaviour has been developed and the ideal conditions identified. © 2013 Elsevier Ltd.

In April 2004, the California Attorney General's (AG) office issued a white paper that provided a “law enforcement perspective of the California energy crisis.” To complete this special issue's coverage, I summarize three aspects of that paper: notably, the deficiencies in market oversight and enforcement that left the deregulated market prone to potential abuse, the principal modus operandi that some market agents used to exploit those deficiencies without fear of retribution, and the AG's “recommendations for improving enforcement and protecting consumers in deregulated energy markets.”

A preliminary assessment of castor plant adaptability at Northern Portugal was performed, together with the evaluation of the extracted raw oil, without any refinement, for biodiesel production. Castor was seeded, plants grew and seeds were manually harvested after 2 years. Mechanical and chemical oil extraction procedures were evaluated. Biodiesel was produced by homogenous alkaline transesterification and experimental planning was conducted to evaluate the influence of temperature and reaction time in product yield and quality; 20 experiments were performed. A 54.1% (w/w) oil yield was obtained by Soxhlet extraction with methanol after grinding the seeds. Product yield ranged from 43.3 to 74.1% (w/w), biodiesel quality varied and the conditions that lead to the best product were established. Results indicate that, to achieve higher product yields and quality using raw oil, longer reaction times are required compared to what is generally reported for refined oil. Statistically significant predictive models were obtained to estimate product yield and quality as function of the studied reaction variables. The best temperature and reaction time to produce biodiesel from raw castor oil were 65 °C and 8 h, where models predict a product yield of 73.62% (w/w) and a purity of 83.41% (w/w).

In this study, a new thermochemical route to produce lignocellulosic ethanol based on DME (dimethyl ether) hydrocarbonylation is proposed and economically assessed. The process is designed and evaluated using current kinetic laboratory data for hydrocarbonylation reactions. Only available technologies or those expected to be available in the short term are considered for the process design, which involves biomass pretreatment and gasification (indirect circulating fluidized bed), gas clean-up and conditioning, methanol synthesis, DME production by methanol dehydration and DME hydrocarbonylation. The process is designed to be both energy self-sufficient and electrical energy neutral. For a plant size of 2140 dry tonnes/day of wood chip (500 MWHHV) the minimum selling price of ethanol (for a 10% rate of return and a biomass price of 66 $/dry tonne) ranges from 0.555 to 0.592 USD2010/L of automotive grade ethanol with fixed capital costs between 333 and 352 M USD2010. Energy efficiency of biomass to ethanol ranges from 44.35 to 45.53% (high heating value basis). These results compare favorably with the “state of the art” production of ethanol via biochemical pathway from lignocellulosic biomass, revealing that the DME hydrocarbonylation route is a promising one that could be cost-competitive in the near future.

This study utilized microwave irradiation to induce torrefaction (mild pyrolysis) of rice husk and sugarcane residues by varying different parameters, including microwave power level, processing time, water content, and particle size of biomass. Proper microwave power levels are suggested to be set between 250 and 300 W for the torrefaction of these two agricultural residues. With proper processing time, the caloric value can increase 26% for rice husk and 57% for sugarcane residue. Compared to dry rice husk, both maximum reaction temperature and mass reduction ratio increased with higher water content (not over 10%). Moreover, the particle size of biomass needs not to be very small. The mass reduction ratios were 65 wt.%, 69 wt.%, and 72 wt.%, when the sizes were 50/100 mesh, 100/200 mesh, and >200 mesh, respectively. Microwave-induced torrefaction reduces more oxygen/carbon ratio of biomass in comparison with traditional torrefaction. Microwave-induced torrefaction is considered as an efficient and promising technology with great potential.