Solid state fermentation and composting as alternatives to treat hair waste : a LCA comparative approach

One of the wastes associated with leather production in tannery industries is the hair residue generated during the dehairing process. Hair wastes are mainly dumped or managed through composting but recent studies propose the treatment of hair wastes through solid-state fermentation (SSF) to obtain proteases and compost. These enzymes are suitable for its use in an enzymatic dehairing process, as an alternative to the current chemical dehairing process. In the present work, two different scenarios for the valorization of the hair waste are proposed and assessed by means of life-cycle assessment: composting and SSF for protease production. Detailed data on hair waste composting and on SSF protease production are gathered from previous studies performed by our research group and from a literature survey. Background inventory data are mainly based on Ecoinvent version 3 from software SimaPro® 8. The main aim of this study was to identify which process results in the highest environmental impact. The SSF process was found to have lower environmental impacts than composting, due to the fact that the enzyme use in the dehairing process prevents the use of chemicals traditionally used in the dehairing process. This permits to reformulate an industrial process from the classical approach of waste management to a novel alternative based on circular economy

Performance, yield and characteristics of bioflocculants (UPMBF13) produced by Bacillus subtilis UPMB13 during submerged and solid-state fermentation

This study compares the distinctive performance, yield and characteristics of bioflocculants (UPMBF13) derived from submerged (SmF) and solid-state fermentation (SSF) of Bacillus subtilis UPMB13. The bioflocculants were subjected to morphological characterization, functional groups determination, molecular weight measurement, protein content quantification and specific compound identification. The SmF and the SSF strategies yielded an average of 2.70 g l-1 and 1.25 g kg-1 of UPMBF13, respectively. The submerged UPMBF13 resulted in a clear suspension with visible flocs formation, while flocs from the SSF treatment were less apparent. Higher total proteinaceous contents of UPMBF13 from the SSF led to the inferiority in flocculating performances. The produced UPMBF13 consisted of hydroxyl, carboxyl, methoxyl and carbonyl functional groups which contributed to their flocculating abilities. The molecular weights of UPMBF13 were around 10-50 kDa, characterizing them into low-molecular weight bioflocculants. The submerged UPMBF13 were more fibrous in nature than the SSF, giving the submerged UPMBF13 the upper hand in flocculation. SmF was the best fermentation method yielding high performing bioflocculants at a faster rate by the utilization of non-elaborative techniques. SSF, on the other hand, was proven feasible but further improvements are needed

Relationships among Physicochemical, Microbiological, and Parasitological Parameters, Ecotoxicity, and Biochemical Methane Potential of Pig Slurry

Background: Pig slurry can negatively impact on the environmental, animal, and human health. Knowing the relationship between the organic and inorganic loads, pathogens, and toxicity allows identifying the main parameters to be removed or treated before final disposal. The aim of this study was to evaluate the relationships between the physicochemical properties, microbiological, and parasitological content, ecotoxicological effects, and biochemical methane potential (BMP) of pig slurries. Methods: Ten pig slurry samples at two production stages were characterized and a BMP test at two substrate/inoculum (S/I) ratios was conducted to compare the methane yields. Results: We found high content of Cu, Zn, quaternary ammonium, pathogenic microorganisms (E. coli and Salmonella), and parasites (Trichuris and Trichostrongylus). Toxicity on lettuce, radish, and Daphnia was observed with a slurry concentration greater than 1.35%. Positive correlations were found between toxicity on Daphnia and chemical oxygen demand (COD), sulfate, Zn, and Cu, as well as between phytotoxicity and COD, NH4, Na, K, and conductivity. The lowest S/I ratio showed 13% more methane yield. It was associated with high removals of COD and volatile fatty acids. Conclusions: We recommend using a low S/I ratio to treat pig slurry as it improves the efficiency of the anaerobic process.Instituto de Microbiología y Zoología Agrícola (IMYZA)Fil: Beily, María Eugenia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Young, Brian Jonathan. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Bres, Patricia Alina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Riera, Nicolas Iván. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Wang, Wenguo. Biogas Institute of Ministry of Agriculture and Rural Affairs. Key Laboratory of Development and Application of Rural Renewable Energy; ChinaFil: Crespo, Diana Elvira. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Komilis, Dimitrios. Democritus University of Thrace. Department of Environmental Engineering; Greci

Effect of Poultry Manure-Derived Compost on the Growth of eucalypts spp. Hybrid Clones

Interspecific hybrids of E. grandis × E. camaldulensis were generated to widen the plantation area. The aim of this study was to assess root capability and development for six different clones of eucalyptus grown in substrates made with three different composts derived from poultry manure. A factorial design was used to assess the effect of different composts on six growth variables. The analysis detected a greater effect from the genotype than the substrate. E. grandis × E. camaldulensis hybrid vegetative propagation was successful in alternative substrates formulated from composted poultry manure. GC8 was the genotype that showed the greatest differences for four the different variables among the substrates, being both the most sensitive and the one with the highest values for all parameters measured. The hybrids' vegetative propagation was determined in alternative substrates formulated from poultry manure compost. The physicochemical characteristics of substrates composed of pine bark and sawdust provided adequate conditions for the growth of eucalyptus. GC8 was the genotype most sensitive to the use of different substrates, showing significant differences in the ratio of roots/callus, radicular dry weight, and cutting dry weight. These clones might be a good option for evaluating compost-based substrates for forestry applications

Relationships among Physicochemical, Microbiological, and Parasitological Parameters, Ecotoxicity, and Biochemical Methane Potential of Pig Slurry

Background: Pig slurry can negatively impact on the environmental, animal, and human health. Knowing the relationship between the organic and inorganic loads, pathogens, and toxicity allows identifying the main parameters to be removed or treated before final disposal. The aim of this study was to evaluate the relationships between the physicochemical properties, microbiological, and parasitological content, ecotoxicological effects, and biochemical methane potential (BMP) of pig slurries. Methods: Ten pig slurry samples at two production stages were characterized and a BMP test at two substrate/inoculum (S/I) ratios was conducted to compare the methane yields. Results: We found high content of Cu, Zn, quaternary ammonium, pathogenic microorganisms (E. coli and Salmonella), and parasites (Trichuris and Trichostrongylus). Toxicity on lettuce, radish, and Daphnia was observed with a slurry concentration greater than 1.35%. Positive correlations were found between toxicity on Daphnia and chemical oxygen demand (COD), sulfate, Zn, and Cu, as well as between phytotoxicity and COD, NH4, Na, K, and conductivity. The lowest S/I ratio showed 13% more methane yield. It was associated with high removals of COD and volatile fatty acids. Conclusions: We recommend using a low S/I ratio to treat pig slurry as it improves the efficiency of the anaerobic process.Instituto de Microbiología y Zoología Agrícola (IMYZA)Fil: Beily, María Eugenia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Young, Brian Jonathan. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Bres, Patricia Alina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Riera, Nicolas Iván. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Wang, Wenguo. Biogas Institute of Ministry of Agriculture and Rural Affairs. Key Laboratory of Development and Application of Rural Renewable Energy; ChinaFil: Crespo, Diana Elvira. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola; ArgentinaFil: Komilis, Dimitrios. Democritus University of Thrace. Department of Environmental Engineering; Greci

Biodegradation activity of eight organic substrates : a correlation study of different test methods

The biological activity of eight organic substrates was assessed using different techniques under aerobic and anaerobic environments at different scales. The used substrates included simulated fresh to actual stabilized composts. Experiments included dynamic respiration (with 30 and 5.5 L reactors), static respiration (with 1 L reactors) and biochemical methane potential (BMP) tests (with 1.1 L flasks). The indices evaluated were: the 24-h dynamic respiration index (DRI₂₄) and the cumulative dynamic respiration indices at 4 and 7 days (DCRI₄ and DCRI₇, respectively) measured with two different methods, the maximum dynamic CO₂ generation rate (D-CO₂_24) at 24 h and a dynamic cumulative CO₂ generation after 7 days (D-CO₂_7), the maximum static O₂ consumption rate in 12 and 24 h (SRI₁₂ and SRI₂₄), the static cumulative O₂ consumptions after 4 and 7 days (SCRI₄ and SCRI7) and the static CO₂ generation after 7 days (S-CO₂) and the BMP after 30 days. The DRI₂₄ ranged from 25 to 3000 mg O2 kg−1 VS h−1 in one lab and from 150 to 3500 mg O₂ kg−1 VS h−1 in the other. A positive statistically significant correlation was achieved between the two types of dynamic indices. In addition, the CH4 production after 30 days showed a strong positive correlation with both DRI₂₄ indices and DCRI₄ and DCRI₇, as measured in both labs. The static respiration indices did not correlate well with the dynamic respiration ones. The practical implications of the use of the biodegradation activity indices were also analysed and discussed

The importance of aeration mode and flowrate in the determination of the biological activity and stability of organic wastes by respiration indices

The aim of this study was to assess the effect of different air flowrates and different aeration modes on the respiration activity of three organic substrates of different stability degree: (i) a constant flowrate and (ii) a continuously adjusted air flowrate that optimized the oxygen uptake rate (OUR). Above 20 L air kg⁻¹ DM h⁻¹, at the constant flow regime, the resulting dynamic respiration index at 24 h (DRI₂₄) and the cumulative respiration at four days (AT₄) were statistically similar. At the OUR based aeration regime, the DRI₂₄ and AT₄ were statistically similar at all initial flowrates tested. Above a minimum threshold, cumulative air flow of around 3000 L air kg⁻¹ DM during a 5 day period, the respiration activity was similar, particularly for the two less active substrates. This study highlights the importance of selecting the aeration to obtain reliable measures of biological activity and stability in organic wastes

The effect of a short term aerobic pretreatment step on the anaerobic co-digestion of the organic fraction of municipal solid wastes : liquid extract addition versus solid phase addition

Dimitrios Komilis thanks TECNIOspring programme for the 2014-2016 incoming fellowship in UAB (no. TECSPR13-1-0006). Raquel Barrena thanks TECNIOspring programme for the outgoing + return fellowship (no. TECSPR15-1-0051).Goal of the work was to study the effect of mixing aerobically pretreated organic municipal solid wastes (OFMSW) with raw OFMSW in an anaerobic digestion process. The optimum time of aerobic pretreatment was found to be five days, as this was indicated via biological activity measurements (oxygen uptake rate, enzymatic activities, temperature). The aerobically pretreated wastes or a liquid extract from those pretreated wastes were, each separately, mixed with simulated OFMSW in various experiments. The mixtures were anaerobically digested for 28 days and five different treatments were performed including the blanks. The methane generation results were fitted to a typical anaerobic model to calculate theoretical maximum methane potential, maximum methane generation rate and theoretical lag time. Results indicated that the addition of 5-day aerobically pretreated OFMSW in solid form to raw OFMSW resulted in a 18 % net increase of the methane production. The Rmax was also increased by 39 % while no significant differences in the lag time of the methanogenic phase were observed. The addition of the liquid extract that was obtained from the 5-day pretreated OFMSW did not result in a statistically significant increase of the net methane production of the raw OFMSW

A state of the art literature review on anaerobic digestion of food waste : influential operating parameters on methane yield

Dimitrios Komilis and Raquel Barrena are grateful to the TECNIOspring fellowship programme (TECSPR13-1-0006 and TECSPR15-1-0051, respectively) co-financed by the European Union through the Marie Curie Actions and ACCIÓ (Generalitat de Catalunya).A thorough literature review was conducted to investigate the behaviour of food waste in anaerobic digestion experiments. The main goal of this literature review was to study the effect of several operating parameters on methane yields and to develop a simplified regression equation to predict methane generation. Using a data prospection methodology, all the papers published within 2013-2015 that contained selected keywords were included in this study (a total of 613 papers). After screening, 167 papers were finally retrieved using the search engines and our methodology. From these papers, data from 231 experiments were recorded and evaluated. The parameters recorded in each paper were: operation mode (batch or continuous), temperature (mesophilic or thermophilic), moisture content (wet or dry), presence or absence of pretreatment, reactor scale (laboratory, bench, pilot, demonstration/full scale), presence or absence of co-substrates (co- or mono-digestion), organic loading rate, hydraulic retention time (HRT) and methane yield. The novelty of the work is that it employed various statistical tools to examine the effect of the above-mentioned factors on food waste methane generation. Most of the experiments were performed at mesophilic temperatures, at a wet system without substrate pretreatment. An equal number of papers described mono-digestion and co-digestion studies, and an equal number of papers described batch and continuous reactor experiments. The mean HRT for the continuous processes was 36.7 days. Statistical analysis indicated that the parameters that significantly affected methane yields were the "operation mode" and "pretreatment". A best reduced regression model was fitted to the methane yield data to describe the above effects. As a general conclusion, with this methodology, that involved the analysis of a large number of studies (with different conditions and set-ups, heterogeneous waste, etc.), correlations between some typical operating parameters of anaerobic digestion and methane yields were not obvious

Glutamic acid independent production of bioflocculants by bacillus subtilis UPMB13

Bacillus subtilis UPMB13 was found to be an L-glutamic acid independent producer of extracellular polymeric substances (EPS) with bioflocculation properties. Optimum production of the bioflocculant was found to be at the early stage of cell propagation of 24-72 h of fermentation. At a limited nutrient input of 100 mL tryptic soy broth, the flocculating activities were found to be negatively correlated (p < 0.01) with growth as it continued to decline after 72 h, while cell growth proliferated further. Ample nutrient supply may prolong bioflocculant production with flocculating activities of 90 % and higher, while excess oxygen supply may promote rapid growth that can lead to poor flocculation due to the re-use of the bioflocculant as a substitute for food during starvation. Bioflocculant production occurred at best at 25-30 °C incubation temperature and at the initial pH medium of 7 to 8. The bioflocculant was proven to be extracellularly produced as the broth and the supernatant possessed the ability to flocculate the suspended kaolin particles. Bioflocculant productions by UPMB13 were hereditarily stable among succeeding progenies, hence, proving genetic competency. About 0.90 g of purified bioflocculant were collected from 1 L culture broth of UPMB13 under the optimized fermentation conditions