Analyzing alternative bio-waste feedstocks for potential biodiesel production using time domain (TD)-NMR

Valorization of fat balls and primary scum from wastewater treatment: a promising renewable lipid feedstock for biodiesel production

We investigated the potential of waste materials from wastewater treatment plants (WWTPs) to serve as an alternative lipid feedstock for biodiesel production. The average lipid recoveries from fat balls (46.4%) and primary scum (49.5-54.5%) were higher than the lipid recovery of primary sludge (15.8-16.4%). The yield of biodiesel produced from the extracted lipids ranged from 5.7 to 20.1%. There were considerable site- and season-dependent variations in the characteristics of the lipid waste materials. Radiocarbon analysis indicated the presence of fossil-derived carbon (26.0-42.0%) in the biodiesel obtained from wastewater lipids. Finally, we estimated the potential for biodiesel production from WWTP-derived lipids; about 333.0 metric tons of biodiesel per year could be produced from fat balls and primary scum in Japan. The results indicate that lipid-rich materials from WWTPs represent a valuable alternative feedstock for biodiesel production.

Lipid extraction in the primary sludge generated from urban wastewater treatment: characteristics and seasonal composition analysis

A seasonal study of the lipid composition of a primary sludge (dry and dewatered base) obtained from an urban wastewater treatment plant located in Aguascalientes (Mexico) is reported. This study assessed the variability in sludge composition to establish its potential as a raw material for biodiesel production. Lipid recovery was achieved by extraction using two solvents. Hexane was employed for lipid extraction from dry sludge, whereas hexane and ethyl butyrate were used for comparison with dewatered sludge. The formation (%) of fatty acid methyl esters (biodiesel) was determined using extracted lipids. The extraction results from the dry sludge showed 14 and 6% of recovered lipids and their conversion to biodiesel, respectively. For the dewatered sludge, the lipid recovery and biodiesel formation were 17.4 and 60% using hexane, and 23 and 77% for ethyl butyrate, respectively, on a dry basis. Statistical data indicated that lipid recovery depended on the physicochemical characteristics of sewage sludge, which were related to seasonal changes, population activities, and changes in plant configuration, among other factors. These variables must be considered in the design of large-scale extraction equipment for the application and commercial exploitation of biomass waste in biofuel production.

Determination of the lipid content of organic waste using time-domain nuclear magnetic resonance

Time-Domain Nuclear Magnetic Resonance (TD-NMR) was used to quantify the lipid contents of 48 different organic waste substrates. Results obtained from TD-NMR were compared to those from Soxhlet extraction, currently the prevalent method for organic waste characterization, especially in the field of anaerobic digestion. Two calibration methods were tested. The first was a self-calibration process using pure oils (NMR1) which showed good repeatability compared to Soxhlet extraction with a better coefficient of variation (5%). Analyses of volatile fatty acids (VFA) and long-chain fatty acids (LCFA) by chromatography were carried out to understand why the NMR1 method produced underestimations for some samples. Statistical analysis showed that the presence of saturated fatty acids had a significant effect on differences between the Soxhlet and NMR1 methods. The second calibration method applied chemometrics to TD-NMR raw data (NMR2), taking Soxhlet extraction values as references. It provided a good prediction of lipid content and avoided the lengthy calibration procedure usually required for this type of study. Last, the NMR2 method was shown to be highly suited to the quantification of lipids in organic waste, demonstrating better repeatability than the classic Soxhlet method.

Energetic Valorisation of Olive Biomass: Olive-Tree Pruning, Olive Stones and Pomaces

Olive oil industry is one of the most important industries in the world. Currently, the land devoted to olive-tree cultivation around the world is ca. 11 × 106 ha, which produces more than 20 × 106 t olives per year. Most of these olives are destined to the production of olive oils. The main by-products of the olive oil industry are olive-pruning debris, olive stones and different pomaces. In cultures with traditional and intensive typologies, one single ha of olive grove annually generates more than 5 t of these by-products. The disposal of these by-products in the field can led to environmental problems. Notwithstanding, these by-products (biomasses) have a huge potential as source of energy. The objective of this paper is to comprehensively review the latest advances focused on energy production from olive-pruning debris, olive stones and pomaces, including processes such as combustion, gasification and pyrolysis, and the production of biofuels such as bioethanol and biodiesel. Future research efforts required for biofuel production are also discussed. The future of the olive oil industry must move towards a greater interrelation between olive oil production, conservation of the environment and energy generation.

Characterization and Recovery of In Situ Transesterifiable Lipids (TLs) as Potential Biofuel Feedstock from Sewage Sludge Obtained from Various Sewage Treatment Plants (STPs)

This study purposed to characterize the sewage sludge from various sewage treatment plants (STPs) as a biodiesel feedstock. Crude biodiesel was produced from each dried primary sludge (PS) and waste activated sludge (WAS) via in situ transesterification process. The average yield of transesterifiable lipid (TL) was 77.8% and 60.4% of the total lipid content from PS and WAS, respectively. The TL yield had a greater margin among WAS than PS samples due to differences in the biological processes adopted in each treatment plant. The TL recovered from PS and WAS contained 54.2% and 40.1% fatty acid methyl esters (FAMEs), respectively, which were mostly made up of palmitic acid (C16:0) and stearic acid (C18:0). The FAME composition of the biodiesel in the WAS sample was highly associated with a microbial community that grows otherwise, depending on the purpose of the biological treatment process. In particular, the increase in the proportion of nitrifying bacteria that grow predominantly under a relatively longer solid retention time (SRT) contributed significantly to the improvement in FAME content.

Replacement of Soybean Meal With Soybean Cake Reduces Methane Emissions in Dairy Cows and an Assessment of a Face-Mask Technique for Methane Measurement

The objective of this study was to (a) evaluate the effect of replacing soybean meal (SBM) with soybean cake (SBC) on feeding behavior, rumen fermentation, milk production, nutrient digestibility and CH₄ emissions and (b) investigate whether a face-mask technique could be used to predict daily methane (CH₄) emissions in dairy cattle. The experiment was conducted as a completely randomized design, with 32 crossbred Holstein × Gyr cows (days in milk (DIM): 112 ± 25.1) randomly assigned to the following treatments (n = 8/group) for 75 days: (1) 0% SBC, (2) 6% SBC, (3) 14% SBC, and (4) 23% SBC, in place of SBM on a dry matter (DM) basis. Across the final 4 weeks of the study, CH₄ production was estimated using the proposed face-mask technique subsequent to a respiration chamber measurement for an evaluation of treatment efficacy and face-mask accuracy. There was no effect of SBM replacement by SBC on intake, feeding or drinking behavior (P > 0.21). Total VFA concentration, the individual proportions of VFA and blood metabolites were not altered (P > 0.17) by SBC, however there was a tendency for decreased (P = 0.08) lactate and plasma urea nitrogen (P = 0.07) concentration associated with SBC addition. Fat-corrected milk yield (FCM_4%) and composition was not affected (P > 0.27) by SBC; however, there was a tendency for decreased total milk solids (P = 0.07) and milk fat (P = 0.08) associated with 23% SBC treatment. There was no treatment × technique interaction (P > 0.05) effect on gas measurements. A maximum reduction (P = 0.01) in CH₄ yield (g/kg DM) and intensity (g/kg milk) of 11 and 20%, respectively, was observed for the 14% SBC inclusion. Compared to the week of mask measurements, chambers decreased (P = 0.01) intake (kg/d, %BW) and increased (P = 0.05) FCM_4%. The face-mask method over estimated O₂ consumption by 5%. The face-mask method accurately predicted daily CH₄ emissions when compared to the chamber at the same time-point. However, there was a linear bias of CH₄ outputs so further evaluation of the calculation of total CH₄ from a spot measurement is required.

Recent development on sustainable biodiesel production using sewage sludge

Biodiesel as a renewable energy is an important alternative to biofuels in current scenario to explore green energy sources. It is well known that the major cost involved in biodiesel production technology is dependent upon the used feedstock. This review presents an overview of biodiesel production using municipal sewage sludge as a cost-effective substrate. Municipal sewage sludge which possesses high lipid content with zero cost availability can meet the characteristics of a potential feedstock to produce biodiesel. Different types of substrates based processes to produce biodiesel have been also explored in brief. In addition, limitations of the existing process technology for biodiesel production with sustainable solutions have been also discussed.

Economic assessment of biodiesel production from wastewater sludge

Currently, there are mainly two pathways of the biodiesel production from wastewater sludge including 1) directly extracting the lipid in sludge and then converting the lipid to biodiesel through trans-esterification, and 2) employing sludge as medium to cultivate oleaginous microorganism to accumulate lipid and then transferring the lipid to biodiesel. So far, the study was still in research stage and its cost feasibility was not yet investigated. In this study, biodiesel production from wastewater sludge was designed and the cost was estimated with SuperPro Designer. With consideration of converting the lipid in raw sludge to biodiesel, the unit production cost was 0.67 US $/kg biodiesel (0.59 US $/L biodiesel). When the sludge was used as medium to grow oleaginous microorganism to accumulate lipid for producing biodiesel, the unit production cost was 1.08 US $/kg biodiesel (0.94 US $/L biodiesel). The study showed that sludge has great potential in biodiesel production.

Effect of sludge features and extraction-esterification technology on the synthesis of biodiesel from secondary wastewater treatment sludges

Secondary sludge from municipal wastewater treatment plant is proposed as a promising alternative lipid feedstock for biodiesel production. A deep study combining different type of raw materials (sludge coming from the oxic, anoxic and anaerobic steps of the biological treatment) with different technologies (liquid-liquid and solid-liquid extractions followed by acid catalysed transesterification and in situ extraction-transesterification procedure) allows a complete comparison of available technologies. Different parameters - contact time, catalyst concentration, pretreatments - were considered, obtaining more than 17% FAMEs yield after 50min of sonication with the in situ procedure and 5% of H₂SO₄. This result corresponds to an increment of more than 65% respect to the best results reported at typical conditions. Experimental data were used to propose a mathematical model for this process, demonstrating that the mass transfer of lipids from the sludge to the liquid is the limiting step.

Thermo-chemo-sonic pre-digestion of waste activated sludge for yeast cultivation to extract lipids for biodiesel production

The low cost biosynthesis of microbial lipids are an efficient feedstock to replace plant based oil for biodiesel production. The present study objective is to explore the effect of thermo-chemo-sonic pre-digestion of municipal Waste Activated Sludge (WAS) to cultivate oleaginous L. starkeyi MTCC-1400 as a model organism to produce high yield biomass and lipid. Higher Suspended Solids (SS) reduction (20 and 15.71%) and Chemical Oxygen Demand (COD) solubilization (27.6 and 22.3%) were achieved at a Specific Energy (SE) input of 5569 kJ/kg for WAS digested with NaOH and KOH, respectively. The maximum biomass of 17.52 g L^-1 and lipid 64.3% dwt were attained in NaOH pre-digested sample. The analyzed lipid profile exhibited high content of palmitic acid (45.6%) and oleic acid (38.7%) which are more suitable for biofuel production. Thus, these results strongly motivate the use of pre-digested WAS as an efficient and economical substrate for biodiesel production.

Scale-up and economic analysis of biodiesel production from municipal primary sewage sludge

Municipal wastewater sludge is a promising lipid feedstock for biodiesel production, but the need to eliminate the high water content before lipid extraction is the main limitation for scaling up. This study evaluates the economic feasibility of biodiesel production directly from liquid primary sludge based on experimental data at laboratory scale. Computational tools were used for the modelling of the process scale-up and the different configurations of lipid extraction to optimise this step, as it is the most expensive. The operational variables with a major influence in the cost were the extraction time and the amount of solvent. The optimised extraction process had a break-even price of biodiesel of 1232 $/t, being economically competitive with the current cost of fossil diesel. The proposed biodiesel production process from waste sludge eliminates the expensive step of sludge drying, lowering the biodiesel price.

Comparison of biodiesel production from sewage sludge obtained from the A²/O and MBR processes by in situ transesterification

The potential of two types of sludge obtained from the anaerobic-anoxic-oxic (A(2)/O) and membrane bioreactor (MBR) processes as lipid feedstock for biodiesel production via in situ transesterification was investigated. Experiments were conducted to determine the optimum conditions for biodiesel yield using three-factor and four-level orthogonal and single-factor tests. Several factors, namely, methanol-to-sludge mass ratio, acid concentration, and temperature, were examined. The optimum yield of biodiesel (16.6% with a fatty acid methyl ester purity of 96.7%) from A(2)/O sludge was obtained at a methanol-to-sludge mass ratio of 10:1, a temperature of 60°C, and a H2SO4 concentration of 5% (v/v). Meanwhile, the optimum yield of biodiesel (4.2% with a fatty acid methyl ester purity of 92.7%) from MBR sludge was obtained at a methanol-to-sludge mass ratio of 8:1, a temperature of 50°C, and a H2SO4 concentration of 5% (v/v). In this research, A(2)/O technology with a primary sedimentation tank is more favorable for obtaining energy from wastewater than MBR technology.

Screening transesterifiable lipid accumulating bacteria from sewage sludge for biodiesel production

Sewage sludge was evaluated as high available and low cost microbial oils feedstock for biodiesel production. Samples from four different wastewater treatment plants from La Araucanía Region in Southern Chile presented total lipids content ranging between 7.7 and 12.6%, being Vilcún sewage sludge that with the highest transesterifiable lipids content of about 50% of the total extracted lipids. The most relevant identified bacteria present in sludge samples were Acinetobacter, Pseudomonas and Bacillus, being Bacillus sp. V10 the strain with the highest transesterfiable lipids content of 7.4%. Bacillus sp. V10 was cultured using urban wastewater supplemented with glucose to achieve nitrogen depleted medium and using milk processing wastewater as a low-cost carbon source. Bacillus sp. V10 lipid profile indicates that low degree unsaturated long chain fatty acids such as C18:1 may account for approximately 50% of the lipids content, indicating its suitability to be used as raw material for biodiesel production.

In situ biodiesel production from greasy sewage sludge using acid and enzymatic catalysts

This study proposes to select the most appropriate sewage sludge (greasy, primary and secondary) for in situ transesterification and to compare the technical, economic and energetic performance of an enzymatic catalyst (Novozym®435) with sulfuric acid. Greasy sludge was selected as feedstock for biodiesel production due to its high lipid content (44.4%) and low unsaponifiable matter. Maximum methyl esters yield (61%) was reached when processing the wet sludge using sulfuric acid as catalyst and n-hexane, followed by dried-greasy sludge catalyzed by Novozym®435 (57% methyl esters). Considering the economic point of view, the process using acid catalyst was more favorable compared to Novozym®435 catalyst due to the high cost of lipase. In general, greasy sludge (wet or dried) showed high potential to produce biodiesel. However, further technical adjustments are needed to make biodiesel production by in situ transesterification using acid and enzymatic catalyst feasible.

Study of liquid-phase molecular packing interactions and morphology of fatty acid methyl esters (biodiesel)

BACKGROUND

(1)H low field nuclear magnetic resonance (LF-NMR) relaxometry has been suggested as a tool to distinguish between different molecular ensembles in complex systems with differential segmental or whole molecular motion and/or different morphologies. In biodiesel applications the molecular structure versus liquid-phase packing morphologies of fatty acid methyl esters (FAMEs) influences physico-chemical characteristics of the fuel, including flow properties, operability during cold weather, blending, and more. Still, their liquid morphological structures have scarcely been studied. It was therefore the objective of this work to explore the potential of this technology for characterizing the molecular organization of FAMEs in the liquid phase. This was accomplished by using a combination of supporting advanced technologies.

RESULTS

We show that pure oleic acid (OA) and methyl oleate (MO) standards exhibited both similarities and differences in the (1)H LF-NMR relaxation times (T2s) and peak areas, for a range of temperatures. Based on X-ray measurements, both molecules were found to possess a liquid crystal-like order, although a larger fluidity was found for MO, because as the temperature is increased, MO molecules separate both longitudinally and transversely from one another. In addition, both molecules exhibited a preferred direction of diffusion based on the apparent hydrodynamic radius. The close molecular packing arrangement and interactions were found to affect the translational and segmental motions of the molecules, as a result of dimerization of the head group in OA as opposed to weaker polar interactions in MO.

CONCLUSIONS

A comprehensive model for the liquid crystal-like arrangement of FAMEs in the liquid phase is suggested. The differences in translational and segmental motions of the molecules were rationalized by the differences in the (1)H LF-NMR T2 distributions of OA and MO, which was further supported by (13)C high field (HF)-NMR spectra and (1)H HF-NMR relaxation. The proposed assignment allows for material characterization based on parameters that contribute to properties in applications such as biodiesel fuels.

Novel 1H low field nuclear magnetic resonance applications for the field of biodiesel

BACKGROUND

Biodiesel production has increased dramatically over the last decade, raising the need for new rapid and non-destructive analytical tools and technologies. 1H Low Field Nuclear Magnetic Resonance (LF-NMR) applications, which offer great potential to the field of biodiesel, have been developed by the Phyto Lipid Biotechnology Lab research team in the last few years.

RESULTS

Supervised and un-supervised chemometric tools are suggested for screening new alternative biodiesel feedstocks according to oil content and viscosity. The tools allowed assignment into viscosity groups of biodiesel-petrodiesel samples whose viscosity is unknown, and uncovered biodiesel samples that have residues of unreacted acylglycerol and/or methanol, and poorly separated and cleaned glycerol and water. In the case of composite materials, relaxation time distribution, and cross-correlation methods were successfully applied to differentiate components. Continuous distributed methods were also applied to calculate the yield of the transesterification reaction, and thus monitor the progress of the common and in-situ transesterification reactions, offering a tool for optimization of reaction parameters.

CONCLUSIONS

Comprehensive applied tools are detailed for the characterization of new alternative biodiesel resources in their whole conformation, monitoring of the biodiesel transesterification reaction, and quality evaluation of the final product, using a non-invasive and non-destructive technology that is new to the biodiesel research area. A new integrated computational-experimental approach for analysis of 1H LF-NMR relaxometry data is also presented, suggesting improved solution stability and peak resolution.