Recycling of food waste as nutrients in Chlorella vulgaris cultivation

Towards a circular economy - Repurposing side streams from the potato processing industry by Chlorella vulgaris

Common wastewater treatment strategies in the food industry do not include efficient remediation strategies for nitrogen, phosphorous and organic carbon. Incorporating microalgae in water treatment plants is rising in popularity because of their high nutrient and trace element uptake driven by light. In this study, four different side streams from an Austrian potato processing company have been screened for their applicability of microalgal cultivation. The side streams were assessed for Chlorella vulgaris growth and their requirement of any additional pretreatment or media supplementation. One side stream specifically, called blanching water II, a stream generated by boiling the potatoes for ease of peeling, turned out very useful to cultivate Chlorella vulgaris and concomitantly remedy the wastewater. Compared to a state-of-the-art cultivation in BG11, cultivating Chlorella vulgaris in blanching water II led to a 45 % increase in specific growth rate of 1.29 day-1 and a 48% increase in biomass productivity to 294.6 mg/L/day, while all nitrogen and phosphate present in the side stream were metabolized. Overall, the results demonstrate that the water remediation process for blanching water II shows vast potential in regard to water purification and waste to value approaches.

Sustainable media feedstocks for cellular agriculture

The global food system is shifting towards cellular agriculture, a second domestication marked by cultivating microorganisms and tissues for sustainable food production. This involves tissue engineering, precision fermentation, and microbial biomass fermentation to establish food value chains independent of traditional agriculture. However, these techniques rely on growth media sourced from agricultural, chemical (fossil fuels), and mining supply chains, raising concerns about land use competition, emissions, and resource depletion. Fermentable sugars, nitrogen, and phosphates are key ingredients derived from starch crops, energy-intensive fossil fuel based processes, and finite phosphorus resources, respectively. This review explores sustainable alternatives to reduce land use and emissions associated with cellular agriculture media ingredients. Sustainable alternatives to first generation sugars (lignocellulosic substrates, sidestreams, and gaseous feedstocks), sustainable nitrogen sources (sidestreams, green ammonia, biological nitrogen fixation), and efficient use of phosphates are reviewed. Especially cellulosic sugars, gaseous chemoautotrophic feedstocks, green ammonia, and phosphate recycling are the most promising technologies but economic constraints hinder large-scale adoption, necessitating more efficient processes and cost reduction. Collaborative efforts are vital for a biotechnological future grounded in sustainable feedstocks, mitigating competition with agricultural land and emissions.

Fermentative Biohydrogen and Biomethane Production from High-Strength Industrial Food Waste Hydrolysate Using Suspended Cell Techniques

The food waste was very difficult to treat in a proper way since its high-organic matter. The novel biohythane (H2 + CH4) production from high-strength industry food waste hydrolysate in two steps anaerobic well mixed batch bioreactor was carried out in this study using cultivated microflora. The temperature was controlled at 37 °C and initial substrate concentration of industrial food waste hydrolysate varied from 60, 80, 100, and 120 g COD/L, respectively. The pH, TS, VS, and SCOD were analyzed from the influent and effluent samples. These analytical parameters showed the correlations between the biogas production rates and yields in the batch fermentation system. This study was the first time to use the industry food waste hydrolysate which was collected from the subcritical water hydrolysis process. In this study, the optimal biohydrogen and biomethane yield production by using suspended cells were 0.65 mL H2/g COD and 203.72 mL CH4/g COD where the initial substrate concentrations of total COD and SCOD were 60 g/L and 39.80 g/L, respectively. The optimal of the biohydrogen and biomethane yields production by using suspended cells were 0.65 mL H2/g COD and 203.72 mL CH4/g COD where the initial substrate concentrations of total COD and SCOD were 60 g/L and 39.80 g/L, respectively. The results of this study supported that the cultivation of inoculum in a suspended cell type can have a higher tolerance for the biohydrogen and biomethane production in a high-strength initial substrate concentration of 60 g COD/L.

Oscillatoria sancta Cultivation Using Fruit and Vegetable Waste Formulated Media and Its Potential as a Functional Food: Assessment of Cultivation Optimization

The most cost-effective technique to cultivate microalgae is with low-cost resources, like fruit and vegetable peels. This study examined the viability of culturing microalgae (Oscillatoria sancta PCC 7515) isolated from a waterlogged region of Punjab, India, in a low-cost medium (fruit and vegetable waste peels) for pharmaceutical use. 16S rRNA sequencing discovered O. sancta PCC 7515. Fruit and vegetable peels were mineralized and chemically analyzed. At a 5% Bacillus flexus concentration, fruit and vegetable peels were liquefied at room temperature for 24 h. Response Surface Methodology (RSM) was used to assess and improve important cultural variables. The RSM predicted the best results at 10 pH, 30 days of incubation, 5% inoculum concentration, and 5% fruit and vegetable waste liquid leachate. The optimum conditions yielded more biomass than the basal conditions (0.8001 g/L). O. sancta PCC 7515 produced more lipids, proteins, Chl a, and Chl b in a formulated alternate medium than standard media. This study shows that O. sancta PCC 7515 may thrive on fruit and vegetable peel media. Fruit and vegetable waste (FVW) media assure low-cost microalgae-based functional foods.

Valorization of environmental-burden waste towards microalgal metabolites production

The present study develops a novel concept of using waste media as an algal nutrient resource compared to the usual growth media with the aid of growth kinetics study and metabolite production abilities. Food- and agri-compost wastes are compact structures with elemental compounds for microbial media. As a part of the study, environ-burden wastes (3:1) as a food source for photosynthetic algae as a substitute for the costly nutrient media were proposed. The environment-burden waste was also envisaged for macromolecule production, i.e., 99200 μg/ml lipid, 112.5 μg/ml protein, and 8.75 μg/ml carbohydrate with different dilutions of agri-waste, bold basal media (BBM), and Food waste, respectively. The fabricated growth kinetics and dynamics showcased the unstructured models of different photosynthetic algal growth phases and the depiction of productivity and kinetic parameters. The theoretical maximum biomass concentration (Xp) was found to be more (0.871) with diluted agricompost media than the usual BBM (0.697). The X_Lim values were found to be 0.362, 0.323 and 0.209 for BBM, diluted agri-compost media and diluted food waste media, respectively. Overall, the study proposes a cleaner approach of utilizing the wastes as growth media through a circular economy approach which eventually reduces the growth media cost with integrated macromolecule production capabilities.

Cultivation of microalgae on food waste: Recent advances and way forward

Microalgae are photosynthetic microbes that can synthesize compounds of therapeutic potential with wide applications in the food, bioprocessing and pharmaceutical sector. Recent research advances have therefore, focused on finding suitable economic substrates for the sustainable cultivation of microalgae. Among such substrates, food derived waste specifically from the starch, meat, dairy, brewery, oil and fruit and vegetable processing industries has gained popularity but poses numerous challenges. Pretreatment, dilution of waste water supernatants, mixing of different food waste streams, utilizing two-stage cultivation and other biorefinery approaches have been intensively explored for multifold improvement in microalgal biomass recovery from food waste. This review discusses the advances and challenges associated with cultivation of microalgae on food waste. The review suggests that there is a need to standardize different waste substrates in terms of general composition, genetically engineered microalgal strains, tackling process scalability issues, controlling wastewater toxicity and establishing a waste transportation chain.

Microalgae/cyanobacteria: the potential green future of vitamin B12 production

This review summarizes the available information about potential sources of vitamin B12, especially for people who follow a vegan or vegetarian diet and inhabitants of poor countries in the developing world. Cyanobacteria and microalgae approved for food purposes can play a critical role as promising and innovative sources of this vitamin. This work involves a discussion of whether the form of vitamin B12 extracted from microalgae/cyanobacteria is biologically available to humans, specifically focusing on the genera Arthrospira and Chlorella. It describes analyses of their biomass composition, cultivation requirements, and genetic properties in B12 production. Furthermore, this review discusses the function of cobalamin in microalgae and cyanobacteria themselves and the possibility of modification and cocultivation to increase the content of B12 in their biomass.

Synergetic biofuel production from co-pyrolysis of food and plastic waste: reaction kinetics and product behavior

This study aimed to develop a process for producing bio-oil, char, and value-added chemicals from food waste and plastic waste blend using co-pyrolysis under controlled conditions. The food waste (rice, vegetables, and fish) was blended in definite ratios (70:30, 60:40, and 50:50 w/w) with polyethylene terephthalate (PET). Experiments were conducted at various temperatures (250, 300, and 350 °C) and reaction times (30, 60, 90, and 120 min). A kinetic analysis was performed to fit experimental data, and reaction kinetics were observed to follow Arrhenius behavior. Maximum yields of bio-oil and bio-char, 66 and 40 wt% respectively, were attained at 350 °C, with yields being strongly influenced by variations in temperature and weakly affected by variations in reaction time. Co-pyrolysis promoted the formation of carboxylic acid, hydrocarbons, and furan derivatives. Formation of carboxylic acid could be increased by increasing the ratio of plastic waste. A maximum carboxylic acid content of 42.01% was achieved at 50% of plastic waste. Meanwhile, a maximum aliphatic hydrocarbon content of 44.6% was obtained with a ratio of 70:30 of food waste to plastic waste at 350 °C. Overall, pyrolysis of food and plastic waste produced value-added compounds that can be used as biofuels and for a variety of other applications.

Metabolic and Proteomic Analysis of Chlorella sorokiniana, Chloroidium saccharofilum, and Chlorella vulgaris Cells Cultured in Autotrophic, Photoheterotrophic, and Mixotrophic Cultivation Modes

Chlorella is one of the most well-known microalgal genera, currently comprising approximately a hundred species of single-celled green algae according to the AlgaeBase. Strains of the genus Chlorella have the ability to metabolize both inorganic and organic carbon sources in various trophic modes and synthesize valuable metabolites that are widely used in many industries. The aim of this work was to investigate the impact of three trophic modes on the growth parameters, productivities of individual cell components, and biochemical composition of Chlorella sorokiniana, Chloroidium saccharofilum, and Chlorella vulgaris cells with special consideration of protein profiles detected by SDS-PAGE gel electrophoresis and two-dimensional gel electrophoresis with MALDI-TOF/TOF MS. Mixotrophic conditions with the use of an agro-industrial by-product stimulated the growth of all Chlorella species, which was confirmed by the highest specific growth rates and the shortest biomass doubling times. The mixotrophic cultivation of all Chlorella species yielded a high amount of protein-rich biomass with reduced contents of chlorophyll a, chlorophyll b, carotenoids, and carbohydrates. Additionally, this work provides the first information about the proteome of Chloroidium saccharofilum, Chlorella sorokiniana, and Chlorella vulgaris cells cultured in molasses supplementation conditions. The proteomic analysis of the three Chlorella species growing photoheterotrophically and mixotrophically showed increased accumulation of proteins involved in the cell energy metabolism and carbon uptake, photosynthesis process, and protein synthesis, as well as proteins involved in intracellular movements and chaperone proteins.

Microalgal transformation of food processing byproducts into functional food ingredients

Large amounts of food processing byproducts (FPBs) are generated from food manufacturing industries, the second-largest portion of food waste generation. FPBs may require additional cost for post-treatment otherwise cause environmental contamination. Valorization of FPBs into food ingredients by microalgae cultivation can save a high cost for organic carbon sources and nutrients from medium cost. This study reviews FPBs generation categorized by industry and traditional disposal. In contrast with the low-value production, FPBs utilization as the nutrient-abundant medium for microalgae can lead to high-value production. Due to the complex composition in FPBs, various pretreatment methods have been applied to extract the desired compounds and medium preparation. Using the FPB-based medium resulted in cost reduction and a productivity enhancement in previous literature. Although there are still challenges to overcome to achieve economic viability and environmental sustainability, the microalgal transformation of FPBs is attractive for functional food ingredients production.

Advances in production of bioplastics by microalgae using food waste hydrolysate and wastewater: A review

Microalgae have emerged as an effective dual strategy for bio-valorisation of food processing wastewater and food waste hydrolysate which favours microalgae cultivation into producing value-added by products mainly lipids, carbohydrates, and proteins to the advantages of bioplastic production. Moreover, various microalgae have successfully removed high amount of organic pollutants from food processing wastewater prior discharging into the environment. Innovation of microalgae cultivating in food processing wastewater greatly reduced the cost of wastewater treatment compared to conventional approach in terms of lower carbon emissions, energy consumption, and chemical usage while producing microalgae biomass which can benefit low-cost fertilizer and bioplastic applications. The study on several microalgae species has all successfully grown on food waste hydrolysates showing high exponential growth rate and biomass production rich in proteins, lipids, carbohydrates, and fatty acids. Multiple techniques have been implemented for the extraction of food wastes to be incorporate into the bioplastic production.

Cultivation of the heterotrophic microalga Galdieria sulphuraria on food waste: A Life Cycle Assessment

The aim of this study was to perform a Life Cycle Assessment of a production process of 1 kg dry algal biomass powder (Galdieria sulphuraria) with 27 % (w/w) protein content for human consumption for optimizing the production regarding global warming potential and resource efficiency in combination with food waste utilization. It was investigated, underpinned by a comparison of the use of conventional glucose, whether and to what extent the environmental impact/global warming potential can be reduced by changing to food waste hydrolysate and how this can lead to a more sustainable use of resources and a sustainable development. Overall, the results showed that hydrolysis, along with freeze-drying, caused most of the overall impact. The carbon footprint associated with the use of hydrolyzed food waste was 11% higher than using conventional glucose and supplementary nutrients mainly driven by the high demand of energy for hydrolysis.

Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

Third-generation biofuels that are derived from microalgal biomass have gained momentum as a way forward in the sustainable production of biodiesel. Such efforts are propelled by the intention to reduce our dependence on fossil fuels as the primary source of energy. Accordingly, growing microalgal biomass in the form of suspended cultivation has been a conventional technique for the past few decades. To overcome the inevitable harvesting shortcomings arising from the excessive energy and time needed to separate the planktonic microalgal cells from water medium, researchers have started to explore attached microalgal cultivation systems. This cultivation mode permits the ease of harvesting mature microalgal biomass, circumventing the need to employ complex harvesting techniques to single out the cells, and is economically attractive. However, the main bottleneck associated with attached microalgal growth is low biomass production due to the difficulties the microalgal cells have in forming attachment and populating thereafter. In this regard, the current review encompasses the novel techniques adopted to promote attached microalgal growth. The physicochemical effects such as the pH of the culture medium, hydrophobicity, as well as the substratum surface properties and abiotic factors that can determine the fate of exponential growth of attached microalgal cells, are critically reviewed. This review aims to unveil the benefits of an attached microalgal cultivation system as a promising harvesting technique to produce sustainable biodiesel for lasting applications.

Heterotrophic cultivation of Galdieria sulphuraria under non-sterile conditions in digestate and hydrolyzed straw

Non-sterile heterotrophic cultivation of Galdieria sulphuraria in presence of digestate as well as straw after hydrolysis was investigated. G. sulphuraria can be grown in pure digestate at rates of 0.9 day^-1 with glucose. However, a proteolytic treatment of digestate resulted in increased growth rates (1.2 day^-1) and doubled cell concentrations. Furthermore, G. sulphuraria can utilize glucose obtained after straw hydrolysis. Biomass yields in glucose limited cultures were around 0.9 g per g glucose, while only 0.2 g biomass was formed per g glucose in glucose sufficient cultures. Biomass composition (w/w) of G. sulphuraria grown in digestate supplemented with straw hydrolysate consisted of 20% carbohydrates, 37% proteins and 3% lipids. This study revealed the potential to utilize agricultural waste streams to form algal biomass rich in proteins and may pave the way to novel utilization strategies to be implemented in rural areas.

Insights into the physiology of Chlorella vulgaris cultivated in sweet sorghum bagasse hydrolysate for sustainable algal biomass and lipid production

Supplementing cultivation media with exogenous carbon sources enhances biomass and lipid production in microalgae. Utilization of renewable organic carbon from agricultural residues can potentially reduce the cost of algae cultivation, while enhancing sustainability. In the present investigation a medium was developed from sweet sorghum bagasse for cultivation of Chlorella under mixotrophic conditions. Using response surface methodology, the optimal values of critical process parameters were determined, namely inoculum cell density (O.D.₇₅₀) of 0.786, SSB hydrolysate content of the medium 25% v/v, and zero medium salinity, to achieve maximum lipid productivity of 120 mg/L/d. Enhanced biomass (3.44 g/L) and lipid content (40% of dry cell weight) were observed when the alga was cultivated in SSB hydrolysate under mixotrophic conditions compared to heterotrophic and photoautotrophic conditions. A time course investigation revealed distinct physiological responses in terms of cellular growth and biochemical composition of C. vulgaris cultivated in the various trophic modes. The determined carbohydrate and lipid profiles indicate that sugar addition to the cultivation medium boosts neutral lipid synthesis compared to structural lipids, suggesting that carbon flux is channeled towards triacylglycerol synthesis in the cells. Furthermore, the fatty acid profile of lipids extracted from mixotrophically grown cultures contained more saturated and monosaturated fatty acids, which are suitable for biofuel manufacturing. Scale-up studies in a photobioreactor using SSB hydrolysate achieved a biomass concentration of 2.83 g/L consisting of 34% lipids and 26% carbohydrates. These results confirmed that SSB hydrolysate is a promising feedstock for mixotrophic cultivation of Chlorella and synthesis of algal bioproducts and biofuels.

Sustainable lipid and lutein production from Chlorella mixotrophic fermentation by food waste hydrolysate

Bioconversion of food waste into value-added products is a promising way to tackle the global food waste management problem. In this study, a novel valorisation strategy for bioenergy and lutein production via microalgal fermentation was investigated. Significant amount of glucose was recovered from enzymatic hydrolysis of food waste. The resultant hydrolysate was then utilised as culture medium in mixotrophic cultivation of Chlorella sp. to obtain high levels of lipid and lutein, whose accumulation patterns were consistent with molecular analyses. The resultant algal lipid derived from microalgal biomass using food hydrolysate was at high quality in terms of biodiesel properties. Further, in semi-continuous fermentation, the average algal biomass was 6.1 g L^-1 with 2.5 g L^-1 lipid and 38.5 mg L^-1 lutein using hydrolysate with an initial glucose concentration of 10 g L^-1. Meanwhile, the resultant algal biomass was 6.9 g L^-1 with 1.8 g L^-1 lipid and 63.0 mg L^-1 lutein using hydrolysate with an initial glucose concentration of 20 g L^-1, which suggests food waste hydrolysate could trigger algal products preferences. The experimental results of this study suggested the potential of microalgae as a platform for bioconversion of food waste into high-value products, especially sustainable bioenergy.

Mining of squalene as a value-added byproduct from DHA producing marine thraustochytrid cultivated on food waste hydrolysate

The commercial production of docosahexaenoic acid (DHA) from oleaginous microorganisms is getting more attention due to several advantages over fish oils. The processing cost became a major bottleneck for commercialization of DHA from microorganisms. The most of cost shares in the feedstock to cultivate the microorganisms and downstream processing. The cost of feedstock can be compensated with the utilization of substrate from waste stream whereas production of value-added chemicals boosts the economic viability of nutraceutical production. In the present study, the docosahexaenoic acid (DHA)-producing marine protist Aurantiochytrium sp. T66 was cultivated on post-consumption food waste hydrolysate for the mining of squalene. After 120 h of cultivation, cell dry weight was 14.7 g/L, of which 6.34 g/L (43.13%; w/w) were lipids. DHA accounted for 2.15 g/L (34.05%) of total extracted lipids or 0.15 g/g_CDW. Maximum squalene concentration and yield were 1.05 g/L and 69.31 mg/g_CDW, respectively. Hence, utilization of food waste represents an excellent low-cost strategy for cultivating marine oleaginous thraustochytrids and produce squalene as a byproduct of DHA.

Estimation of the economy of heterotrophic microalgae- and insect-based food waste utilization processes

An estimation of the economy of Hermetia illucens and Chlorella pyrenoidosa cultivations as food waste treatment with benefits was carried out. For both organisms, a process scale was assumed to treat 56.3 t of wet food waste per day, which is equivalent to the amount of food waste appearing in a catchment area of 141,000 inhabitants. Using hypothetical insect and heterotrophic microalgae cultivation processes, a daily production of 3.64 t and 7.14 t dried biomass, respectively, can be achieved. For the cultivation of H. illucens, equipment and daily operational costs were estimated at 79,358.15 € and 5,281.56 €, respectively. Equipment and operational costs for the C. pyrenoidosa cultivation was 50 and 6 times higher, respectively. The higher costs reflect the more complex and advanced process compared to H. illucens cultivation. The internal return rate for a plant lifetime of 20 times revealed an economic benefit when C. pyrenoidosa biomass is produced. Nevertheless, both processes were found economically feasible when dried biomass is directly commercialized as food without any further downstream processing. However, extraction and purification of special chemicals, such as unsaturated fatty acids and pigments, can significantly increase the revenue.

Sustainable biorefinery concept for biofuel production through holistic volarization of food waste

The aim of this study was to utilize the whole food waste in two stages. In the first stage, the carbohydrate and protein fractions of food waste recovered after enzymatic hydrolysis was used to cultivate heterotrophic microalgae, resulting in biomass yield of 0.346 ± 0.09 g/g_sugars and lipid yield of 0.216 ± 0.06 g/g_sugars. In the second stage, oil (14.15% w/w) was extracted from food waste after hydrolysis and converted to biodiesel by a two-step transesterification reaction that generated 135.8 g/kg_{food waste} of fatty acid methyl esters and 13.8 g/kg_{food waste} of crude glycerol. Finally, crude glycerol obtained from both processes was used at 20 g/L to cultivate heterotrophic microalgae, resulting in a cell dry weight and total lipid concentration of 6.23 g/L and 2.91 g/L, respectively. A total 248.21 g of fatty acid methyl esters were obtained from the 1 kg of food waste through this integrated process.

A study on catalytic co-pyrolysis of kitchen waste with tire waste over ZSM-5 using TG-FTIR and Py-GC/MS

Co-pyrolysis characteristics of kitchen waste (KW) with tire waste (TW) were studied by TGA-FTIR and Py-GC/MS. The kinetic parameters were calculated by Ozawa-Flynn-Wall (OFW) and the Kissinger-Akahira-Sunose (KAS) methods. TGA-FTIR results indicated that CO₂, CO, NO, NH₃, SO₂, CH and CC groups were the main gases released from the pyrolysis process, finding that a certain coupling synergistic interaction occurred between KW and TW. Co-pyrolysis of KW and TW displayed positive synergy in pyrolysis kinetics, especially at the ratio of 5:5 whose apparent activation energy declined 16.78% (by FWO) and 17.54% (by KAS). The Py-GC/MS results found that co-pyrolysis could increase the total peak area of volatile matters (10.92-15.34%). Moreover, co-pyrolysis could increase hydrocarbons (especially for olefins (13.25-37.42%)) and inhibit non-hydrocarbon compounds (about 63%) of volatile products. In brief, co-pyrolysis of KW and TW could be a potential way for improving quality of pyrolysis oil.

Bioconversion of kitchen wastes into bioflocculant and its pilot-scale application in treating iron mineral processing wastewater

In this study, the feasibility of converting kitchen waste into bioflocculant using Bacillus agaradhaerens C9 was analyzed. The result showed that strain C9 could secrete various degrading enzymes, including amylase, protease, lipase, cellulase, xylanase and pectinase, promoting the hydrolysis of kitchen waste. Strong alkaline fermentation condition was able to induce the bioflocculant production, and inhibit the growth of contaminated bacteria, which avoids the sterilization process of kitchen waste. The optimum fermentation condition for enzymatic hydrolysis and bioflocculant production was 40 g/L kitchen waste, 37 °C, pH 9.5, and the highest bioflocculant yield of 6.92 g/L was achieved. Furthermore, bioflocculant was applied to treat pilot-scale (30 L) of mineral processing wastewater for the first time, and the removal rate of 92.35% was observed when 9 mg/L bioflocculant was added into wastewater. Therefore, this study could promote the resource utilization of kitchen waste and recycling of mineral processing wastewater.

Food waste compost as an organic nutrient source for the cultivation of Chlorella vulgaris

The present study investigates the prospective of substituting inorganic medium with organic food waste compost medium as a nutrient supplement for the cultivation of Chlorella vulgaris FSP-E. Various percentages of compost mixtures were replaced in the inorganic medium to compare the algal growth and biochemical composition. The use of 25% compost mixture combination was found to yield higher biomass concentration (11.1%) and better lipid (10.1%) and protein (2.0%) content compared with microalgae cultivation in fully inorganic medium. These results exhibited the potential of combining the inorganic medium with organic food waste compost medium as an effective way to reduce the cultivation cost of microalgae and to increase the biochemical content in the cultivated microalgae.

Co-pyrolysis characteristics and kinetic analysis of organic food waste and plastic

In this work, typical organic food waste (soybean protein (SP)) and typical chlorine enriched plastic waste (polyvinyl chloride (PVC)) were chosen as principal MSW components and their interaction during co-pyrolysis was investigated. Results indicate that the interaction accelerated the reaction during co-pyrolysis. The activation energies needed were 2-13% lower for the decomposition of mixture compared with linear calculation while the maximum reaction rates were 12-16% higher than calculation. In the fixed-bed experiments, interaction was observed to reduce the yield of tar by 2-69% and promote the yield of char by 13-39% compared with linear calculation. In addition, 2-6 times more heavy components and 61-93% less nitrogen-containing components were formed for tar derived from mixtures.

Utilization of organic residues using heterotrophic microalgae and insects

Various organic residues occur globally in the form of straw, wood, green biomass, food waste, feces, manure etc. Other utilization strategies apart from anaerobic digestion, composting and incineration are needed to make use of the whole potential of organic residues as sources of various value added compounds. This review compares the cultivation of heterotrophic microalgae and insects using organic residues as nutrient sources and illuminates their potential with regard to biomass production, productivity and yield, and utilization strategies of produced biomasses. Furthermore, cultivation processes as well as advantages and disadvantages of utilization processes are identified and discussed. It was shown that both heterotrophic algae and insects are able to reduce a sufficient amount of organic residues by converting it into biomass. The biomass composition of both organisms is similar which allows similar utilization strategies in food and feed, chemicals and materials productions. Even though insect is the more complex organism, biomass production can be carried out using simple equipment without sterilization and hydrolysis of organic residues. Contrarily, heterotrophic microalgae require a pretreatment of organic residues in form of sterilization and in most cases hydrolysis. Interestingly, the volumetric productivity of insect biomass exceeds the productivity of algal biomass. Despite legal restrictions, it is expected that microalgae and insects will find application as alternative food and feed sources in the future.

Effect of lipid-free microalgal biomass and waste glycerol on growth and lipid production of Scenedesmus obliquus: Innovative waste recycling for extraordinary lipid production

In the present work, a novel approach of using growth medium with different substitutions of lipid-free algal hydrolysate (LFAH, 0, 5, 10 and 15%) and/or waste glycerol (WG, 0, 5, 10 and 20 g L^-1) for enhanced biodiesel production from Scenedesmus obliquus was studied. Combination of different concentrations of WG with 15% LFAH showed the maximum significant biomass productivity, which represented 27.4, 30.5 and 28.9% over the control at combined 5, 10 and 20 g L^-1 WG, respectively. The combinations of different LFAH with 20 g L^-1 WG showed the maximum significant lipid accumulation, where lipid productivity showed its maximum significant value of 59.66 mg L^-1 d^-1 using LFAH15-WG10. In addition, LFAH15-WG10 significantly enhanced total FAMEs yield by 21.2% over the control. Moreover, it reduced polyunsaturated fatty acids (PUFAs) ratio from 52.1% to 47.8% of total FAMEs, and increased monounsaturated fatty acids (MUFAs) ratio from 26.6% to 31.3% of total FAMEs.

Use of food waste, fish waste and food processing waste for China's aquaculture industry: Needs and challenge

China's aquaculture industry is growing dramatically in recent years and now accounts for 60.5% of global aquaculture production. Fish protein is expected to play an important role in China's food security. Formulated feed has become the main diet of farmed fish. The species farmed have been diversified, and a large amount of 'trash fish' is directly used as feed or is processed into fishmeal for fish feed. The use of locally available food waste as an alternative protein source for producing fish feed has been suggested as a means of tackling the problem of sourcing safe and sustainable feed. This paper reviews the feasibility of using locally available waste materials, including fish waste, okara and food waste. Although the fishmeal derived from fish waste, okara or food waste is less nutritious than fishmeal from whole fish or soybean meal, most fish species farmed in China, such as tilapia and various Chinese carp, grow well on diets with minimal amounts of fishmeal and 40% digestible carbohydrate. It can be concluded that food waste is suitable as a component of the diet of farmed fish. However, it will be necessary to revise regulations on feed and feed ingredients to facilitate the use of food waste in the manufacture of fish feed.

Environmental building policy by the use of microalgae and decreasing of risks for Canadian oil sand sector development

Environmental building recommendations aimed towards new environmental policies and management-changing decisions which as example demonstrated in consideration of the problems of Canadian oil sands operators. For the implementation of the circular economic strategy, we use an in-depth analysis of reported environmental after-consequence on all stages of the production process. The study addressed the promotion of innovative solutions for greenhouse gas emission, waste mitigation, and risk of falling in oil prices for operators of oil sands with creating market opportunities. They include the addition of microalgae biomass in tailings ponds for improvement of the microbial balance for the water speedily cleaning, recycling, and reusing with mitigation of GHG emissions. The use of food scraps for the nutrition of microalgae will reduce greenhouse gas emission minimally, on 0.33 MtCO₂eq for Alberta and 2.63 MtCO₂eq/year for Canada. Microalgae-derived biofuel can reduce this emission for Alberta on 11.9-17.9 MtCO₂eq and for Canada on 71-106 MtCO₂eq/year, and the manufacturing of other products will adsorb up to 135.6 MtCO₂ and produce 99.2 MtO₂. The development of the Live Conserve Industry and principal step from non-efficient protection of the environment to its cultivation in a large scale with mitigation of GHG emission and waste as well as generating of O₂ and value-added products by the use of microalgae opens an important shift towards a new design and building of a biological system.

Growth and phycocyanin synthesis in the heterotrophic microalga Galdieria sulphuraria on substrates made of food waste from restaurants and bakeries

Galdieria sulphuraria 074G (Rhodophyta) was grown heterotrophically in defined medium and on amylolytic and proteolytic hydrolysed food waste from restaurants and bakeries. Substrate uptake, growth, and phycocyanin content were quantified in the cultures. The alga utilised carbohydrates and amino acids from the waste but ammonium and other inorganic nutrients were needed to stimulate phycocyanin synthesis. Highest specific phycocyanin contents (20-22mgg^-1) were observed in cells grown at 25°C or 34°C on the food wastes. Growth inhibition was observed when the hydrolysates were used in quantities resulting in glucose concentrations of 10 and 50gL^-1 for bakery and restaurant waste, respectively. Still, G. sulphuraria 074G grew and produced phycocyanin efficiently on food waste under adequate conditions and may potentially be utilised for synthesise of high-valuable products from food waste.

Hydrolysate of lipid extracted microalgal biomass residue: An algal growth promoter and enhancer

The present study demonstrates the utilization of the algal hydrolysate (AH) prepared from lipid extracted residual harmful bloom-forming cyanobacteria Lyngbya majuscula biomass, as a growth supplement for the cultivation of green microalgae Chlorella vulgaris. BG-11 replacements with AH in different proportions significantly affects the cell count, dry cell weight (DCW), biomass productivity (BP) and pigments concentration. Among all, 25% AH substitution in BG11 media was found to be optimum which enhanced DCW, BP and pigments content by 39.13%, 40.81% and 129.47%, respectively, compared to control. The lipid content (31.95%) was also significantly higher in the 25% AH replacement. The volumetric productivity of neutral lipids (ideal for biodiesel) and total protein content of the cells significantly increased in all AH substitutions. Thus, lipid extracted microalgal biomass residue (LMBR) hydrolysate can be a potential growth stimulating supplement for oleaginous microalgae C. vulgaris.

Utilization of protein-rich residues in biotechnological processes

A drawback of biotechnological processes, where microorganisms convert biomass constituents, such as starch, cellulose, hemicelluloses, lipids, and proteins, into wanted products, is the economic feasibility. Particularly the cost of nitrogen sources in biotechnological processes can make up a large fraction of total process expenses. To further develop the bioeconomy, it is of considerable interest to substitute cost-intensive by inexpensive nitrogen sources. The aim of this mini-review was to provide a comprehensive insight of utilization methods of protein-rich residues, such as fish waste, green biomass, hairs, and food waste. The methods described include (i) production of enzymes, (ii) recovery of bioactive compounds, and/or (iii) usage as nitrogen source for microorganisms in biotechnological processes. In this aspect, the utilization of protein-rich residues, which are conventionally considered as waste, allows the development of value-adding processes for the production of bioactive compounds, biomolecules, chemicals, and materials.

Enhancing the hydrolysis and methane production potential of mixed food waste by an effective enzymatic pretreatment

In this study, a fungal mash rich in hydrolytic enzymes was produced by solid state fermentation (SSF) of waste cake in a simple and efficient manner and was further applied for high-efficiency hydrolysis of mixed food wastes (FW). The enzymatic pretreatment of FW with this fungal mash resulted in 89.1 g/L glucose, 2.4 g/L free amino nitrogen, 165 g/L soluble chemical oxygen demand (SCOD) and 64% reduction in volatile solids within 24h. The biomethane yield and production rate from FW pretreated with the fungal mash were found to be respectively about 2.3 and 3.5-times higher than without pretreatment. After anaerobic digestion of pretreated FW, a volatile solids removal of 80.4±3.5% was achieved. The pretreatment of mixed FW with the fungal mash produced in this study is a promising option for enhancing anaerobic digestion of FW in terms of energy recovery and volume reduction.

Biohydrogen production from food waste hydrolysate using continuous mixed immobilized sludge reactors

A continuous mixed immobilized sludge reactor (CMISR) using activated carbon as support carrier for dark fermentative hydrogen production from enzymatic hydrolyzed food waste was developed. The effects of immobilized sludge packing ratio (10-20%, v/v) and substrate loading rate (OLR) (8-40kg/m(3)/d) on biohydrogen production were examined, respectively. The hydrogen production rates (HPRs) with packing ratio of 15% were significantly higher than the results obtained from packing ratio of 10% and 20%. The best HPR of 353.9ml/h/L was obtained at the condition of packing ratio=15% and OLR=40kg/m(3)/d. The Minitab was used to elicit the effects of OLR and packing ratio on HPR (Y) which could be expressed as Y=5.31 OLR+296 packing ratio+40.3 (p=0.003). However, the highest hydrogen yield (85.6ml/g food waste) was happened at OLR of 16kg/m(3)/d because of H2 partial pressure and oxidization/reduction of NADH.