Residual Streams Research Articles

Dewatering methanotrophic enrichments intended for single cell protein production using biomimetic aquaporin forward osmosis membranes

Microbial biomass is becoming an alternative source of protein, especially for application in animal feeds formulations. While much progress has been made in biomass cultivation, harvesting after cultivation remains a very costly part of the overall process. This study investigated low-cost forward osmosis for dewatering methanotrophic cultures using biomimetic aquaporin membranes. Brine and glycerol were used as draw solutions as they are available as inexpensive industrial byproducts. NaCl and MgCl2 were also used to better understand the behavior of brine. With NaCl and brine the highest water fluxes were obtained, but ammonium retention was low and high reverse salt fluxes were measured. With MgCl2, the highest specific water flux (Jw/Js = 7.5 ± 1.7 L g−1) and a good ammonium retention (~85%) was obtained. Thus, only brines with high content on MgCl2 should be considered for FO applications. With glycerol as draw solution, the solute back flux was the highest without affecting microbial growth or methane yields. Hence it shows potential as good draw solution, if available as residual stream. Surprisingly there was no significant difference in water fluxes at the different osmotic pressures (30 and 60 atm). Noteworthy biofouling did not affect the water fluxes, except the case when NaCl at 60 atm was used as draw solution. Overall, this study demonstrates that forward osmosis is a feasible technology for harvesting methanotrophic biomass.

On the feasibility of small communities wellhead RO treatment for nitrate removal and salinity reduction

The feasibility of wellhead water treatment in small communities for nitrate removal and salinity reduction via a flexible high recovery RO system was evaluated through analysis of treatment options, laboratory and onsite field tests. In small remote communities that rely on septic systems for residential wastewater treatment, discharge of the RO residual stream (containing nitrate) to the community septic tank is shown to be a feasible option. It is demonstrated that RO treatment with a system that employs partial concentrate recycle, integrated with a pressure intensifier, enabled the use of a relatively low-pressure feed pump while allowing high recovery operation. The approach of integrating RO treatment into existing community small water systems is demonstrated to be suitable for providing effective nitrate removal and salinity reduction over wide range of nitrate and salinity levels, while meeting community water demand and regulatory water quality requirements.

A Multifunctional Biosurfactant Extract Obtained from Corn Steep Water as Bactericide for Agrifood Industry.

The increase of crop production along with stricter requirements on food security have augmented the demand of new and eco-friendly bactericides. Most of the bactericides used at the moment consist of persistent organic substances, representing a risk for environmental and human health. For instance, agriculture bactericides used for crop protection includes copper-based, dithiocarbamate and amide bactericides, which are not biodegradable, resulting in the necessity of further research about the production of new active principles that attack microorganisms without producing any harmful effect on human health or environment. The biosurfactant extract evaluated in this work as a bactericide, is obtained from corn steep water, a residual stream of corn wet milling industry, which is fermented spontaneously by probiotic lactic acid bacteria that possess the capacity to produce biosurfactants. In previous works, it has been demonstrated that this biosurfactant extract is able to promote the growth of Lactobacillus casei in drinkable yogurts, though its antimicrobial activity against pathogenic strains has not been evaluated at the moment. The results obtained in this work have proved that this biosurfactant extract is effective as bactericide against Pseudomonas aeruginosa and Escherichia coli, at concentrations of 1 mg/mL, opening the door to its use in agrifood formulations for reducing the use of chemical pesticides and preservatives.

Innovative Production of Bioproducts From Organic Waste Through Solid-State Fermentation

Solid-state fermentation (SSF) is, by definition, a technology carried out in the absence or near absence of free water. Therefore, it allows the use of solid materials as substrates for further biotransformation. SSF has gained attention in the last years, being reported as a promising eco-technology to produce bioproducts of industrial interest using solid biomass (wastes and by-products). Main advantages over conventional submerged fermentation rely on the lower water use and energy requirements,which generates minimum residual streams. However, drawbacks often appear,related to poor homogeneity and energy and mass transfer limitations, hindering the process yield and the downstream of the produced bioproducts. Despite the difficulties, many successful processes have been reported on the production of a variety of bioproducts such as hydrolytic enzymes, mostly carbohydrases for bioethanol production, and to a lesser extent, aromas, biosurfactants, biopesticides, bioplastics, organic acids or phenolic compounds. Most of the reported research focuses on process development at a small scale; however, the main challenges to overcome in SSF are related to the upscaling and the development of consistent and continuous operation. In this work, the main advances in the production of valuable/innovative bioproducts are presented and discussed.

Fractionation of sugarcane bagasse using hydrothermal and advanced oxidative pretreatments for bioethanol and biogas production in lignocellulose biorefineries

The fractionation of sugarcane bagasse (SB) by hydrothermal pretreatment (HP, autohydrolysis) followed by alkaline extraction (AE) and advanced oxidative pretreatment (AOP) for production of second-generation ethanol and biogas was investigated. The AOP of SB was optimized using a Doehlert design, varying the applied H2O2 load, liquid-to-solid ratio (LSR), and time. The responses evaluated were yield (Y), residual cellulose (RC), delignification (DE), and enzymatic conversion (EC). The AE of SB pretreated by HP led to 61.8% DE (using 0.2 mol L−1 NaOH). This high lignin removal enabled substantial savings of H2O2 in the AOP. The optimized AOP conditions led to 78% Y, 82.2% RC, 42.7% DE, and 88.9% EC (overall glucose yield of 60.9%). Fermentation of the enzymatic hydrolysate with Saccharomyces cerevisiae yielded 190.8 Lethanol tonSB−1. Biogas production by anaerobic digestion of residual liquid streams of the pretreatment steps yielded 27.46 NLCH4 kgSB−1. An energy balance was estimated for the SB fractionation.

Production of molecular weight fractionated hemicelluloses hydrolyzates from spent coffee grounds combining hydrothermal extraction and a multistep ultrafiltration/diafiltration

Spent coffee grounds are a huge residual stream from instant coffee makers. The production of spent coffee oil and molecular weight fractionated hemicellulose hydrolysates via supercritical CO2 and a hydrothermal treatment followed by concentration, separation, and purification through cascade ultrafiltration/diafiltration (30-10-5 kDa) was studied. Hemicelluloses extraction yield reached 3.49 g/100 g of dry defatted spent coffee after 40 min at 160 °C. The ultrafiltration system allowed concentrating up to 5-fold certain groups of hemicellulose, being most of them retained in the first membrane. Hemicellulose concentration and molecular weight of the feed exerted a great influence on the mass transfer through the membrane due to the formation of aggregates. However, purification through diafiltration allowed both to decrease by-products retentions from 45.6% to 8.7%, increasing the molecular weight of each fraction. Six hemicellulose products were obtained with purities between 83.7 and 97.8 wt% and weight-average molecular weights between 1641 and 49,733 Da.

Multi-component extraction process of high added value compounds from microalgae with supercritical CO2: A technical and economic study

In this work a multicomponent extraction process of high added value compounds (principally omega-3 fatty acids and carotenoids) from a microalgal matrix (Chlorella vulgaris), using supercritical CO2, was studied. Chlorella's metabolites were analyzed singularly, not as a pseudocomponent, and their affinities to the solvent were explored. The Simplified Broken and Intact Cell model was implemented in order to represent the extraction yields and to define the best conditions in terms of operative variables, ensuring the preservation of the bioactive and thermolabile properties of the extracted metabolites. Moreover, these conditions were chosen also for keeping carotenoids’ solubility in supercritical CO2 very low, in order to separate them (residue stream) from fatty acids (extract stream) without further purification steps. All of these informations were used to implement a simulation of the process, optimizing the daily cycles and increasing the productivity. As last step, calculations of the energy and utilities’ consumption for the estimation of the Operating Expense (OPEX) and Capital Expenditure (CAPEX), as starter point for a future industrial implementation of the process, were carried out.

Strategies for Increasing the Biohydrogen Yield in Anaerobic Fermentation of Xylose

The pretreatment of lignocellulosic materials to obtain cellulose generates a residual stream with hemicellulosic composition, mainly containing xylose. This C5 fraction is not directly fermentable by microorganisms traditionally used to produce ethanol. Hence, more promising alternatives for the C5 fraction have been studied, and acidogenic fermentation proves to be an attractive option for the production of biohydrogen, due to the possibility of using hemicellulose fractions and mixed anaerobic cultures. To reduce the activity of hydrogen-consuming microorganisms when mixed cultures are employed as inoculum to produce hydrogen by anaerobic fermentation, thermal pretreatment was selected. However, such pretreatment method also affects the activity of hydrogen-producing acidogenic bacteria, and strategies should be studied to enrich the inoculum for these bacteria and to increase hydrogen yields. Thus, this study evaluated the effect of some strategies on the biohydrogen production from xylose. The strategies adopted were thermal pretreatment of the sludge, maintenance of the incubation temperature at 35 °C, adaptation of the sludge by successive contacts with the xylose solution, and increasing inoculum to substrate ratio (I/S) from 1 to 2. This approach improved hydrogen yield approximately 30 times, from 0.03 to 0.93 mmol H2/mmol xylose. However, this yield was only 56% of the theoretical value and can still be improved.

Valorisation of surplus food in the French retail sector: Environmental and economic impacts

The retail sector, generating large amounts of food waste in a limited and well-defined number of locations, represents a unique opportunity for the implementation of waste minimisation policies targeting food waste and surplus food. France has introduced policy measures forcing retailers to prioritise the redistribution of surplus food to charity (donation) and/or diversion to animal feed. To evaluate the environmental benefits from such initiatives, this study provides a bottom-up consequential life cycle assessment of surplus food management at twenty retail outlets in France. A cradle-to-grave assessment was performed, including land-use changes, and the impacts were evaluated for ten impact categories. Four scenarios were considered, using monthly data on waste flows and management. Alongside assessing the current management (i.e. redistribution and/or use of surplus food for animal feed with anaerobic digestion and incineration of residual streams), three additional scenarios were evaluated: (i) prevention (used as benchmark), (ii) anaerobic digestion and (iii) incineration. The results demonstrated that redistribution leads to substantial environmental savings when accounting for all potentially induced benefits, second only to prevention but nevertheless of similar magnitude. Neither anaerobic digestion nor incineration can compete environmentally with redistribution and use as animal feed, especially in a low-carbon energy system. A cost analysis, including tax credits implemented in the French regulation, demonstrated that retailers donating high-value products also achieved lower costs and higher environmental savings overall. The results clearly suggest that similar initiatives should be encouraged, and the study offers a consistent basis for evaluating similar initiatives also for other countries.

Preparation and Characterization of Whey Protein-Based Polymers Produced from Residual Dairy Streams.

The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source—milk proteins—was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey residual, which is a by-product in the cheese-making process. Two different sources of whey protein were tested: Whey protein isolate (WPI) containing 91% protein concentration and whey protein concentrate (WPC) containing 77% protein concentration. These were methacrylated, followed by free radical polymerization with co-polymer poly(ethylene glycol) methyl ether methacrylate (PEGMA) to obtain polymer sheets. Different protein concentrations in water (11–14 w/v%), at two protein/PEGMA mass-ratios, 20:80 and 30:70, were tested. The polymers made from WPI and WPC at a higher protein/PEGMA ratio of 30:70 had significantly better tensile strength than the one with lower protein content, by about 1–2 MPa (the best 30:70 sample exhibited 3.8 ± 0.2 MPa and the best 20:80 sample exhibited 1.9 ± 0.4 MPa). This indicates that the ratio between the hard (protein) and soft (copolymer PEGMA) domains induce significant changes to the tensile strengths of the polymer sheets. Thermally, the WPI-based polymer samples are stable up to 277.8 ± 6.2 °C and the WPC-based samples are stable up to 273.0 ± 3.4 °C.

A Feasible Application of Circular Economy: Spent Grain Energy Recovery in the Beer Industry

The generation of residual streams and wastes is a common constant in all productive processes. The brewing sector generates a large quantity of residual by-products which can be sustainably reused within the industry to contribute to cover the energy requirement of the process and at the same time to contribute to minimize the amount of waste that is sent to landfills. In this paper the feasibility and advantages of incorporating a stage for energy recovery from some of the solid wastes generated during the process as part of the circular economy approach is presented. La Cibeles, a local small size beer process is taken as a real example. In a brewing process the main wastes that are produced are: grain husks, yeast and CO2. Out of the three, the most important one is the grain husk or brewers’ spent grain that can make around 85% of the total waste of a brewery. The results presented in this study show that, by gasification of brewers’ spent grain, not only the final volume of the residue to be disposed is considerably minimised, but also it is possible to obtain a net economic saving of around 22% in the consume of fossil fuels used in the brewing process when the syngas produced is used for heat generation.

Model for practical carbonation depth prediction for high volume fly ash concrete and recycled aggregate concrete

Abstract The reuse of industrial residue streams such as fly ash (FA) or waste materials such as recycled concrete aggregate (RCA) can be beneficial both from an economic and an ecological point of view. Extensive research, investigating different properties of these concrete types, has been carried out so far. However, durability remains a key property ensuring sustainable application of these materials in the construction sector that still needs more research to be fully understood. The main objective of this study was to evaluate the application of widely used models for carbonation depth prediction—defined for ordinary Portland cement concrete with natural aggregate (NAC)—to high volume FA concrete (HVFAC) and recycled aggregate concrete (RAC). The research presented in this paper was conducted in two steps. First, an experimental programme was designed to provide better understanding of the influence of different CO2 concentrations on the carbonation process kinetics in HVFAC, RAC and NAC. This was performed using accelerated carbonation tests (CO2 concentrations of 1%, 2%, 4% and 16%) and natural carbonation tests (duration 21 and 48 months). Furthermore, a database of previously published results of HVFAC and NAC carbonation depths was made in order to analyse the application of carbonation depth prediction defined by Tuutti and given in the fib Model Code 2010. It was shown that the existing models, providing the relationship between accelerated test results and natural carbonation depth, are applicable to NAC and RAC but not to HVFAC. Modifications of the above mentioned models were proposed in order to enable a more accurate and reliable prediction of the HVFAC carbonation depth under natural exposure conditions.

Oligosaccharides fractionation cascades with 3 outlet streams

Fructooligosaccharides (FOS) were fractionated using nanofiltration cascades. Instead of creating one product and a residual stream, we report on configurations that create 3 separate product streams rich in: (1) monosaccharides (DP1), (2) DP3 and (3) DP ≥ 5. We developed a modular system allowing different operating pressures and membrane types at each stage. Two possible alternative configurations were assessed for a 3-stage cascade both experimentally and via simulation. The simulation was performed using a steady state model and was in a good agreement with the experimental data. Using the simulation model, the system was optimized towards 4 and 5 stage cascades. All designs were evaluated based on the purities and yields of 3 components of interest in the corresponding product streams. Selecting the correct set up, the cascade was able to reach maximum purity of monosaccharides to 66 wt% (from 9 wt%), DP3 to 33 wt% (from 24 wt%) and DP ≥ 5 to 54 wt% (from 34 wt%). Increasing the number of stages improved the maximum purities of the 3 fractions. However, a fifth stage did not increase the purification and the best purities were found using 4-stage rather than 5-stage cascades.

Conversion of organic resources by black soldier fly larvae: Legislation, efficiency and environmental impact

To meet the projected substantial growth in the global demand for meat, we are challenged to develop additional protein-rich feed ingredients while minimizing the use of natural resources. The larvae of the black soldier fly (BSF) have the capacity to convert low-value organic resources into a high quality protein source for pigs, chickens and fish and as such may increase both the productivity and the efficiency of the food chain. The aim of this study was to assess the environmental opportunities of BSF larvae reared on different sources using up to date literature data on the efficiency of BSF larvae in converting such resources into biomass. The current EU legislative framework was used to classify the various resources for rearing insects. Data of forty articles published until 1 September 2017 were used, reporting on in total 78 (mixtures of) resources used for growing BSF larvae. Data on the resource conversion efficiency on dry matter (DM) and N basis was presented in 11 and 5 studies, evaluating 21 and 13 resources, respectively. Resources studied included food and feed materials (A, n = 8 resources), foods not intended (anymore) for human consumption (B1, n = 4), and residual streams such as food waste (D, n = 2), and animal manure (E, n = 7). Conversion efficiency varied from 1.3 to 32.8% for DM and from 7.4 to 74.8% for N. Using life cycle assessment, our environmental results showed that resources within the legal groups (i.e. A and B1) that are, at the moment, not allowed in EU as animal feed have in general a lower impact in terms of global warming potential, energy use, and land use. On a per kg protein basis, BSF larvae reared on a resource that contains food (e.g. sorghum) and feed (e.g. dried distillers grains with solubles) products generally have higher environmental impacts than conventional feed protein sources (fishmeal and soybean meal). Using insects as feed, therefore, has potential to lower the environmental impact of food production but a careful examination of the resource is needed in terms of environmental impact, safety and economics.

An efficient privacy protection scheme for data security in video surveillance

The advancement in video surveillance has raised significant concerns about privacy protection. The existing methods focus on identifying the sensitive region and preserving the behavior of the target, however, they ignore the recoverability of private content. In this paper, we propose a novel and efficient privacy protection scheme for data security in video surveillance, which jointly addresses several key challenges, including de-identification, behavior preservation, recoverability, and compressibility in one unified system. Our method constructs a public stream and a private residual error stream by blurring the private sensitive region. With our scheme, ordinary users could recognize the behaviors in the public identity-protected video stream for surveillance purpose, while authorized users are able to access the recovered private content (e.g., for law investigations). Moreover, the compressed privacy protected region and residual error could be able to save the costs associated with transmission and storage. The extensive experiments on two standard surveillance datasets and a user study demonstrate the effectiveness of our privacy protection system.

Establishing an industrial symbiosis – key factors and time aspects in steel industry

Today production industry has increasing incentives to be resource efficient and sustainable. Many residual material streams from production processes are therefore recycled internally; however, some streams might be of better use in another industry. In this study, factors seen as encouraging and/or barriers in the work towards an industrial symbiosis with residual materials, between two or more industries, were identified. The factors were divided into five categories: physical/technical, regulatory, business, motivation and society, on three organisational levels. Based on the key factors, the time aspect for establishing an industrial symbiosis was studied and criteria that need to be met in order to carry on with a business idea for a residual material were divided into three work phases. The study shows that an industrial symbiosis based on residual materials on many levels differs from a business with main products, for example when it comes to laws and policies. With residual materials it is also extra important to have good understanding of the material properties and the customer’s material requirements. It was concluded that the establishment of industrial symbioses would be facilitated if all materials had the same conditions regardless of origin provided that the final product gets the same properties.

Assessing the technical and environmental performance of wood-based fiber laminates with lignin based phenolic resin systems

Over the past five years, the mobilization of fiber wood assortments for promoting material use, and the integration of supply and conversion chains between biorefineries and the wood panel industry have been intensively investigated. In this regard, the production of fibers and by-products from industrial wood and the substitution of phenolic resin systems with natural polymers such as lignin offer a promising alternative for increasing the bio-based content in composite materials. A direct use of the natural lignin without intermediate downstream processing could support the implementation of energy efficient and short processing routes. But it also could open new challenges such as to identify the extent to which substitution of phenolic resins are technically feasible without compromising the required mechanic performances of the obtained products. For this reason it is needed to identify the material compositions in laminate production, which exhibit good mechanic performance values and in the same time contribute to the reduction of environmental impacts. Considering these constraints in material design, practical results from material testing of different composite materials were used to conduct a comparative Life Cycle Assessment (LCA). The environmentally most preferable compositions of beech fiber laminates are identified for the selected product compositions. Furthermore a LCA scenario analysis is applied to compare the environmental preferability of the use of industrial wood assortments in fiber provisioning against the use of industrial wood residues within coupled production schemes of the wood-based bioeconomy. The results show that in nine out of eleven impact categories reduction potentials of up to 39% are achieveable and that the use of residue streams shows a rather limited benefit in realizing further reduction potentials.

Grassroots petroleum refinery configuration for heavy oil processing

This paper presents a model-based optimization approach to design a grassroots petroleum refinery for heavy oil processing including residue treating and upgrading. The focus is to determine an optimal refinery configuration to produce light products from an atmospheric residue stream. The proposed linear model can consider a large number of heavy oil processing technologies (more than 70) including multiple operating modes to arrive at a configuration that meets an objective of maximizing profit or a certain fuel type production. Computational results show trends in agreement with real-world practice for residuum refining applications, thus contributing to substantiating practicality of the approach.

Effect of Operating Conditions and Split Ratio for Lactic Acid Purification by Short Path Evaporation System

An increasing interest for discovery new environment-friendly sources of chemicals has been observed due to the current concerns related to the cost and environmental impact of fossil-based chemicals. One important technological platform is the production of bio-based chemicals by fermentation, such as lactic acid (LA). In this work, LA was produced by fermentation using sugarcane molasses without pretreatment as carbon source and Lactobacillus plantarum inoculum. Traditionally, several steps are needed after fermentation to produce the final LA product. By not using organic solvents and not produce gypsum, short path evaporation system (SPE) is an alternative separation process to purify the LA. Evaporator temperature (from 116 to 164 °C) and condenser temperature (from 13 to 22 °C) were studied aiming to determine the best operating conditions for SPE. This evaluation to obtaining maximum LA purity and recovery can be made either in the distillate or in the residue stream. In the range of study, the product obtained at the distillate stream using evaporator temperature of 141 °C and condenser temperature of 17.6 °C presented the richest lactic acid fraction (~70 wt%) with recovery of ~55 %. Using split ratio (mass of residue/ mass of distillate) of 1.5, the residue stream presented ~22 wt% of LA fraction with ~52 % of recovery. In addition, results were compared with previous works using different distillation processes. The comparison was performed based on Purification Performance Index (PPI).

Conversion from dual stream to single stream recycling results in nuanced effects on revenues and waste stream amounts and composition

Single stream recyclables collection (residents set out all recyclables in one container without sorting them further) has become the dominant means of curbside recycling in the United States. Proponents claim it motivates residents to set out more materials for recovery because it is more convenient than other collection strategies; others claim it may also lead to poorer quality materials sent to market. Here we report on a conversion on Long Island (New York) from dual stream collection (paper and container recyclables collected in separate passes) to single stream collection. No other major change was made to the waste program, unlike other documented switches from single stream to dual stream, which means changes we document appear to be due solely to the collection processes change. Waste composition studies before and after the conversion added important information. We found significant (25%) increases in set outs for recycling, but also more inclusion of non-recyclable items in the recycling bins. Residents increased their separation rates of targeted recyclable materials, but because waste composition changed from 2012 to 2014, the increased separation rates resulted in about the same amount of recyclable materials being set aside. However, we estimate that the residual waste stream contained much less recyclable material concurrent with the change to single stream recycling, primarily due to the changes to the waste stream composition and size.