Sustainable organic waste valorisation: A zero-waste approach.

The annual increase in global organic waste generation emphasises the need to develop a sustainable management platform to address environmental concerns. This study aims to explore sustainable treatments for the conversion of organic waste into energy in pursuit of zero-waste. The organic waste generated from the animal feed industry (referred to as WF) was used for the model compound in this study. 8.5 wt% of lipids were extracted from the WF, which contained unidentified impurities. Acid-catalysed transesterification yielded less than 80 wt% biodiesel might be due to the reversible reaction. In contrast, non-catalytic transesterification resulted in a significantly higher biodiesel yield (95.6 wt%), suggesting that this method was more effective at converting impure lipids into biodiesel compared to acid-catalysed transesterification. These results indicate the potential advantages of the non-catalytic approach, particularly when dealing with impure lipid sources. To minimise the generation of waste in the process, the WF residue produced after lipid extraction was converted into combustible gas (syngas) through pyrolysis. CO2 was used as a reactive medium in pyrolysis. In one-stage pyrolysis, the gas yield under CO2 was comparable to that under N2, indicating that CO2 did not react effectively with the volatiles derived from the WF residue. Enhanced CO2 reactivity was achieved via catalytic pyrolysis using a nickel-impregnated catalyst. Consequently, the combustible gas yield under CO2 was much higher than that under N2. This approach might contribute to maximising the efficiency of converting organic waste into renewable energy while simultaneously consuming CO2 during pyrolysis, thereby enhancing the sustainability of this approach.

Metabolic engineering of Caldicellulosiruptor bescii for hydrogen production.

Hydrogen is an alternative fuel for transportation vehicles because it is clean, sustainable, and highly flammable. However, the production of hydrogen from lignocellulosic biomass by microorganisms presents challenges. This microbial process involves multiple complex steps, including thermal, chemical, and mechanical treatment of biomass to remove hemicellulose and lignin, as well as enzymatic hydrolysis to solubilize the plant cell walls. These steps not only incur costs but also result in the production of toxic hydrolysates, which inhibit microbial growth. A hyper-thermophilic bacterium of Caldicellulosiruptor bescii can produce hydrogen by decomposing and fermenting plant biomass without the need for conventional pretreatment. It is considered as a consolidated bioprocessing (CBP) microorganism. This review summarizes the basic scientific knowledge and hydrogen-producing capacity of C. bescii. Its genetic system and metabolic engineering strategies to improve hydrogen production are also discussed. KEY POINTS: • Hydrogen is an alternative and eco-friendly fuel. • Caldicellulosiruptor bescii produces hydrogen with a high yield in nature. • Metabolic engineering can make C. bescii to improve hydrogen production.

Potential application of urease and nitrification inhibitors to mitigate emissions from the livestock sector: a review.

Human activities have caused an increase in greenhouse gas emissions, resulting in climate change that affects many factors of human life including its effect on water and food quality in certain areas with implications for human health. CH4 and N2O are known as potent non-CO2 GHGs. The livestock industry contributes to direct emissions of CH4 (38.24%) and N2O (6.70%) through enteric fermentation and manure treatment, as well as indirect N2O emissions via NH3 volatilization. NH3 is also a secondary precursor of particulate matter. Several approaches have been proposed to address this issue, including dietary management, manure treatment, and the possibility of inhibitor usage. Inhibitors, including urease and nitrification inhibitors, are widely used in agricultural fields. The use of urease and nitrification inhibitors is known to be effective in reducing nitrogen loss from agricultural soil in the form of NH3 and N2O and can further reduce CH4 as a side effect. However, the effectiveness of inhibitors in livestock manure systems has not yet been explored. This review discusses the potential of inhibitor usage, specifically of N-(n-butyl) thiophosphoric triamide, dicyandiamide, and 3,4-dimethylpyrazole phosphate, to reduce emissions from livestock manure. This review focuses on the application of inhibitors to manure, as well as the association of these inhibitors with health, toxicity, and economic benefits.

Behavioral changes of sows with changes in flattening rate.

In this study, considering the difficulties for all farms to convert farm styles to animal welfare-based housing, an experiment was performed to observe the changes in the behavior and welfare of sows when the slat floor was changed to a collective breeding ground. Twenty-eight sows used in this study were between the second and fifth parities to minimize the influence of parity. Using a flats floor cover, the flattening rates were treated as 0%, 20%, 30%, 40%, and 50%. Data collection was the behavior of sows visually observed using a camera (e.g., standing, lying, fighting and excessive biting behaviors, and abnormal behaviors) and the animal welfare level measured through field visits. Lying behavior was found to be higher (p < 0.01) as the flattening rate increased, and sows lying on the slatted cover also increased as the flattening rate increased (p < 0.01). Fighting behavior wasincreased when the flattening rate was increased to 20%, and chewing behavior was increased (p < 0.05) as the flattening rate increased. The animal welfare level of sows, 'good feeding', it was found that all treatment groups for body condition score and water were good at 100 (p < 0.05). 'Good housing' was the maximum value (100) in each treatment group. As the percentage of floor increased, the minimum good housing was increased from 78 in 0% flattening rate to 96 in 50% flattening rate. The maximum (100) 'good health' was achieved in the 0% and 20% flattening rates, and it was 98, 98, and 99 in the 30%, 50%, and 40% flattening rate, respectively. 'Appropriate behavior' score was significantly lower than that of other paremeters, but when the flattening ratio was 0% and 20%, the maximum and minimum values were 10. At 40% and 50%, the maximum values were 39 and 49, respectively, and the minimum values were analyzed as 19 for both 40% and 50%. These results will be used as basic data about sow welfare for farmers to successfully transition to group housing and flat floors.

Evaluation of pilot-scale in-vessel composting for Hanwoo manure management.

The study investigated the effect of in-vessel composting process on Hanwoo manure in two different South Korea regions (Pyeongchang and Goechang) with sawdust using vertical cylindrical in-vessel bioreactor for 42days. The stability and quality of Hanwoo manure in both regions were improved and confirmed through the positive changes in physico-chemical and phytotoxic properties using different commercial seed crops. The pH and electrical conductivity (EC, ds/m) of composted manure in both regions were slightly increased. At the same time, carbon:nitrogen (C:N) ratio and ammonium nitrogen:nitrate nitrogen (NH4+-N:NO3--N) ratio decreased to 13.4-16.1 and 0.36-0.37, respectively. The germination index (GI, %) index was recorded in the range of 67.6-120.9%, which was greater than 50%, indicating phytotoxin-free compost. Although, composted manure values in Goechang region were better in significant parameters, overall results confirmed that the composting process could lead to complete maturation of the composted product in both regions.

Evaluation of integrated ammonia recovery technology and nutrient status with an in-vessel composting process for swine manure.

The study investigated the effect of different initial moisture (IM) content (55, 60, 65, and 70%) of composting mixtures (swine manure and sawdust) for the production of nutrient rich manure, and the recovery of ammonia through a condensation process using a vertical cylindrical in-vessel composter for 56days. The composting resulted in a significant reduction in C:N ratio and electrical conductivity (EC), with a slight increase in pH in all products. The NH3 were emitted notably, and at the same time the NO3--N concentration gradually increased with the reduction of NH4+-N in the composting mixtures. The overall results confirmed, the 65% IM showed the maximum nutritional yield, maturity and non-phytotoxic effects (Lycopersicon esculentum L.), with the results of ideal compost product in the following order of IM: 65%>60%>70%>55%. Finally, the recovered condensed ammonia contained considerable ammonium nitrogen concentrations and could be used as fertilizer.

Nutrient status and phytotoxicity analysis of goat manure discharged from farms in South Korea.

The present study evaluated the phytotoxicity effect of goat manure (GM) collected from six different regions in South Korea, namely, Chupungnyeong (T1), Hoengseong (T2), Goesan (T3), Sancheong (T4), Jangsu (T5) and Namwon (T6). Phytotoxicity was assessed by means of the analysis of germination index (GI), relative seed germination (RSG), relative root elongation (RRE) and vigor index (VI) using five commercial crop varieties, namely, sesame (Sesamum indicum L.), chrysanthemum (Chrysanthemum indicum L.), carrot (Daucus carota), radish (Raphanus sativus) and cabbage (Brassica rapa). Physico-chemical parameter values were recorded at appreciable levels in all GM extracts. The effect of seedling growth was significantly different (p ≤ .05) due to the variability of nutrient content and phytotoxic effect of the extracts on the different crop seeds. Of the extracts, Goesan (T3) and Sancheong (T4) recorded the best results in the range of GI (%) (54.1-128.8) and VI (930.7-1044) and GI (%) (70.1-167.3) and VI (609.2-3034), respectively, and also showed no inhibitory effect in any of the crop seeds. Overall results also revealed that radish crops showed excellent and non-phytotoxic results in all manure extracts compared to the other crops.

Comparison of biomass production and total lipid content of freshwater green microalgae cultivated under various culture conditions.

The growth and total lipid content of four green microalgae (Chlorella sp., Chlorella vulgaris CCAP211/11B, Botryococcus braunii FC124 and Scenedesmus obliquus R8) were investigated under different culture conditions. Among the various carbon sources tested, glucose produced the largest biomass or microalgae grown heterotrophically. It was found that 1% (w/v) glucose was actively utilized by Chlorella sp., C. vulgaris CCAP211/11B and B. braunii FC124, whereas S. obliquus R8 preferred 2% (w/v) glucose. No significant difference in biomass production was noted between heterotrophic and mixotrophic (heterotrophic with light illumination/exposure) growth conditions, however, less production was observed for autotrophic cultivation. Total lipid content in cells increased by approximately two-fold under mixotrophic cultivation with respect to heterotrophic and autotrophic cultivation. In addition, light intensity had an impact on microalgal growth and total lipid content. The highest total lipid content was observed at 100 µmol m(-2)s(-1) for Chlorella sp. (22.5%) and S. obliquus R8 (23.7%) and 80 µmol m(-2)s(-1) for C. vulgaris CCAP211/11B (20.1%) and B. braunii FC124 (34.9%).

A new genotype of Miscanthus sacchariflorus Geodae-Uksae 1, identified by growth characteristics and a specific SCAR marker.

Miscanthus is referred to as an ideal lignocellulosic bioenergy crop, which can be used to generate heat, power, and fuel, as well as to reduce carbon dioxide emissions. The new Miscanthus sacchariflorus genotype named Geodae-Uksae 1 was recently collected from damp land in southern Korea. This study investigated the growth characteristics of Miscanthus genotypes, and developed a specific, sensitive, and reproducible sequence characterized amplified region (SCAR) marker to distinguish new M. sacchariflorus genotype Geodae-Uksae 1 from other native Miscanthus species in Korea. Growth characteristics such as stem length, stem diameter, and dry weight of Geodae-Uksae 1 were greater than those of normal M. sacchariflorus. The genotypes within Geodae-Uksae 1 were had the highest genetic similarity. A putative 1,800-bp polymorphic sequence specific to Geodae-Uksae 1 was identified with the random amplified polymorphic DNA (RAPD) N8018 primer. The sequence-characterized amplified region (SCAR) primers Geodae 1-F and Geodae 1-R were designed based on the unique RAPD amplicon. The SCAR primers produced a specific 1,799-bp amplicon in authentic Geodae-Uksae 1, whereas no amplification was observed in other Miscanthus species. The SCAR marker could contribute to identify Geodae-Uksae 1 among native Miscanthus species. The new Miscanthus genotype Geodae-Uksae 1 has great potential as an alternative lignocellulosic biomass feedstock for bioenergy productions.

Development of SCAR marker for simultaneous identification of Miscanthus sacchariflorus, M. sinensis and M. x giganteus.

The sequence-characterized amplified region (SCAR) marker for simultaneous identification of Miscanthus sacchariflorus, Miscanthus sinensis, and Miscanthus x giganteus was developed. In this study, it was attempted for the first time to develop the SCAR marker for detecting the molecular phenotypes among Miscanthus species. Randomly amplified polymorphic DNA technique was applied for this study and one fragment which is unique to M. sacchariflorus was identified and then sequenced. Based on the specific fragment, one SCAR primer pair designated as MS62-5F and MS62-5R was designed to amplify an approximately 1,000 bp DNA fragment within the sequenced region. Diagnostic PCR was performed using the primer pair. Using this SCAR marker, approximately 1,000 bp and 1,200 bp DNA fragments were obtained in M. sacchariflorus and M. sinensis, respectively. Moreover, M. x giganteus was obtained both bands at the same time. The result showed that this SCAR marker can clearly distinguish the M. sacchariflorus, M. sinensis, and M. x giganteus, respectively.

Dechlorination with sodium thiosulfate affects the toxicity of wastewater contaminated with copper, cadmium, nickel, or zinc.

Sodium thiosulfate is recommended by U.S. Environmental Protection Agency for dechlorination of the effluent samples containing residual chlorines before the toxicity testing. For samples contaminated with residual chlorine and metals, e.g., Cd(II), Cu(II) and Ni(II); however, metal toxicity as measured with Daphnia magna was reduced even at approximately half the recommended amount of sodium thiosulfate. Formation of metal-thiosulfate complexes that are less bioavailable may explain the apparent reduction of metal toxicity. In contrast, for samples spiked with Zn(II), dechlorination with sodium thiosulfate increased toxicity. The use of sodium thiosulfate for dechlorination should be cautioned when the sample under the bioassay is potentially contaminated with metals.

Volumetric scale-up of a three stage fermentation system for food waste treatment.

In this study, a volumetric scale-up of this system was designed and built on a field pilot-scale (total digester volume 10 m(3)), with the results from the field pilot-scale experiments compared with those from the bench-scale (total digester volume 0.4 m(3)) process prior to scale-up. The reduction rate of total chemical oxygen demand (tCOD) and the maximum methane content produced in the biogas from the bench-scale system were 90.6% and 72%; whereas those from the field pilot-scale system were 90.1% and 68%, respectively. The estimated methane yields were 282 and 254 l CH(4)/kg tCOD(degraded) in bench and field pilot-scale fermentation systems, respectively. These results indicate that the three stage fermentation system developed in this study can be applied as a commercial process for the disposal of food waste in view of process stability.

Application of a microbial toxicity assay for monitoring treatment effectiveness of pentachlorophenol in water using UV photolysis and TiO2 photocatalysis.

Conventional approaches for monitoring the effectiveness of wastewater treatment processes include evaluating the degradation of the target compound and/or generation of its nontoxic byproducts. These approaches are, however, limited because routine chemical analyses alone are neither able to fully address potential hazard to biological receptors nor characterize potential synergistic interactions. This study was carried out to investigate the degradation effectiveness of pentachlorophenol (PCP) by treatment with UV-A, UV-B photolysis, sunlight, TiO(2) photocatalysis, and/or their combinations. Chemical analyses of the parent compound and its selected byproducts, as well as acute toxicity assessment using the luminescent bacteria Vibrio fischeri (Microtox), were conducted during and after the various photolytic and photocatalytic treatments. In general, the toxicity reduction pattern observed after treatment corresponded well with the chemical degradation data. However, it should be noted that there were occasions that acute microbial toxicity was observed even from the treated water samples, some of which showed complete removal of the parent compound. This post-treatment toxicity might be due to toxic PCP byproducts, which may include polychlorinated dibenzodioxins/furans, tetrachloro-p-benzoquinone, and other intermediates. The TiO(2) photocatalysis with UV-B photolysis was the most effective method to remove both PCP and its toxic derivatives in the water. The Microtox assay is an easy to use and promising approach for evaluating the effectiveness of wastewater treatment processes.

Effects of temperature and hydraulic retention time on anaerobic digestion of food waste.

A modified three-stage methane fermentation system was developed to digest food waste efficiently. This system consisted of three stages: semianaerobic hydrolysis, anaerobic acidogenesis and strictly anaerobic methanogenesis. In this study, we examined the effects of temperature and hydraulic retention time (HRT) on the methanogenesis. Operation temperature was adjusted from 30 degrees C to 55 degrees C, and the HRTs ranged from 8 to 12 d. The rate of soluble chemical oxygen demand (sCOD) removal correlated with digestion time according to the first-order kinetic model developed by Grau et al. [Water Res., 9, 637-642 (1975)]. With liquor food waste, thermophilic digesters showed a higher rate of sCOD removal than mesophilic digesters. The rates of biogas and methane production by thermophilic digesters were higher than those by mesophilic digesters regardless of HRT. Although maximum biogas production occurred when an HRT of 10 d was used, the methane yield was the highest in the reactor when an HRT of 12 d was used (223 l CH4/kg sCODdegraded). However, digestion stability decreased when an HRT of 8 d was used. The concentration of NH3-N generated in this experiment did not inhibit anaerobic digestion.

Degradation mechanism and the toxicity assessment in TiO2 photocatalysis and photolysis of parathion.

The photocatalytic degradation of methyl parathion was carried out using a circulating TiO2/UV reactor. The experimental results showed that parathion was more effectively degraded in the photocatalytic condition than the photolysis and TiO2-only condition. With photocatalysis, 10mg/l parathion was completely degraded within 60 min with a TOC decrease exceeding 90% after 150 min. The main ionic byproducts during photocatalysis were measured. The nitrogen from parathion was recovered mainly as NO3-, NO2- and NH4+, 80% of the sulfur as SO4(2-), and less than 5% of the phosphorus as PO4(3-). The organic intermediates 4-nitrophenol and paraoxon were also identified, and these were further degraded. Two different bioassays (Vibrio fischeri and Daphnia magna) were used to test the acute toxicity of solutions treated by photocatalysis and photolysis. A Microtox test using V. fischeri showed that the toxicity, expressed as the relative toxicity (%), was reduced almost completely after 90 min under photocatalysis, whereas only an 83% reduction was achieved with photolysis alone. Another toxicity test using D. magna also showed that the relative toxicity disappeared after 90 min under photocatalysis, whereas there was a 65% reduction in relative toxicity with photolysis alone. The pattern of toxicity reduction parallels the decrease in parathion and TOC concentrations.