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Effects of temperature treatment on corn cob composting and reducing of composting time: A comparative study
Abstract and Figures
This study focuses on the effect of temperature on the compost quality and the processing time. Two temperature, namely 46°C (high temperature) and 30°C (low temperature) were considered for the composting trials. A mixture of 60% ground corn cob, 30% dried sports grass and 10% bio-activator was used as composting material. The composting process lasted for 120 days. The maturity indices at the end of composting indicate that, for the high-temperature treatment, the compost show an improved quality as compared to the low-temperature treatment. The maturity indices, namely carbon to nitrogen ratio, water extractable organic carbon, ratio of cation exchange capacity to total organic carbon and germination index, determined for the high temperature treatment are: 13.9, 1.48 mg mL⁻¹, 2.21, and 86%, respectively. On the basis of the compost characteristics, the processing time for the high- and low-temperature treatments was 75 days and 105 days, respectively. It can be concluded that treatment at the high-temperature level considered in this study presents a more suitable option for improvement of composting.
... The temperature was recorded daily throughout the entire composting experiment (13 weeks), and Figure 2 illustrates the temperature variation curve over time. The temperature curve exhibits an initial temperature of 52 • C. Subsequently, the composting process transitioned directly into a thermophilic phase, characterized by a sustained temperature of greater than 50 • C. The temperatures recorded were similar to the ones observed by Itävaara et al. (1997) [60], who also reported temperatures exceeding 50 • C and rising as high as 80 • C. Another study by Kianirad et al. (2009) [61] also noted that higher temperatures, typically exceeding 55 • C, are favorable for the efficient biodegradation of PBAT, and even longer aromatic oligomers can degrade during composting at such elevated temperatures [62]. Secondly, the compost maintained a pH between 6 and 7, and an increased pH of 8.16 was observed by the end of the study. ...
... The temperature was recorded daily throughout the entire composting experiment (13 weeks), and Figure 2 illustrates the temperature variation curve over time. The temperature curve exhibits an initial temperature of 52 • C. Subsequently, the composting process transitioned directly into a thermophilic phase, characterized by a sustained temperature of greater than 50 • C. The temperatures recorded were similar to the ones observed by Itävaara et al. (1997) [60], who also reported temperatures exceeding 50 • C and rising as high as 80 • C. Another study by Kianirad et al. (2009) [61] also noted that higher temperatures, typically exceeding 55 • C, are favorable for the efficient biodegradation of PBAT, and even longer aromatic oligomers can degrade during composting at such elevated temperatures [62]. Secondly, the compost maintained a pH between 6 and 7, and an increased pH of 8.16 was observed by the end of the study. ...
... The temperatures recorded were similar to the ones observed by Itävaara et al. (1997) [60], who also reported temperatures exceeding 50 °C and rising as high as 80 °C. Another study by Kianirad et al. (2009) [61] also noted that higher temperatures, typically exceeding 55 °C, are favorable for the efficient biodegradation of PBAT, and even longer aromatic oligomers can degrade during composting at such elevated temperatures [62]. Secondly, the compost maintained a pH between 6 and 7, and an increased pH of 8.16 was observed by the end of the study. ...
In recent years, the environmental impacts of plastic production and consumption have become increasingly significant, particularly due to their petroleum-based origins and the substantial waste management challenges they pose. Currently, global plastic waste production has reached 413.8 million metric tons across 192 countries, contributing notably to greenhouse gas emissions. Bioplastics have emerged as eco-friendly alternatives, with bioplastic carrier bags composed of 20% starch, 10% additives, and 70% polybutylene adipate terephthalate (PBAT) being the focus of this research. This study aimed to evaluate the biodegradation of these bioplastic bags under industrial composting conditions, addressing the gap in the existing literature that often lacks real-world applicability. A large-scale composting experiment was conducted using 37.5 tons of manure/wood and 50 tons of biopolymer bags over 12 weeks. Results showed that compost temperatures peaked at 70 °C and remained above 50 °C, pH levels stabilized at 8.16, and electrical conductivity was recorded at 1251 μs cm−1. Significant changes were observed in key metrics, such as the carbon-to-nitrogen ratio and organic matter content. Disintegration tests revealed that 95% of the bags disintegrated by the 12th week, though ecotoxicity tests indicated varying germination inhibition rates. Advanced analytical methods (Fourier transform infrared spectroscopy, gas chromatography coupled with mass spectrometry) highlighted morphological and chemical transformations in the bags. This research enhances understanding of bioplastic degradation in real-world composting environments and suggests potential improvements to existing standards, promoting sustainable waste management solutions.
... The main factors controlling composting are: operating parameters (moisture content and aeration), pH, and temperature are not industrially altered, and nature of substrate (C/N ratio and particle size). Among them, temperature is a key factor to judge the process efficiency in composting (Ekinci et al. 2004;Lei and Vandergheynst 2000;Kianirad et al. 2009). Moreover, in accordance with Wang and Ai (2016) and Ponsá et al. (2009), a balance among moisture content, diffusion transport, and oxygen supply is necessary to obtain a suitable composting process; hence, an adequate size, as physical pretreatment, is necessary in these residues. ...
... The samples were analysed for: pH (1:5 w/v) using a pH electrode, total organic matter (OM) by loss on ignition (550 °C for 5 h) (Klute et al., 1986), and carbon was estimated as OM/1.8 (Haug 1993). Carbon was also expressed on ashfree basis, total P (HCl acid digest) using the ascorbic acid method (Jones 2001). Total K, Ca, Mg, Fe, Cu, Mn, and Zn are determined by total digestion of the compost in strong acid (concentrated HCl), with subsequent analysis by atomic absorption spectrometry (Variant SpectrA 220FS, Jones 2001) and the total Kjeldahl-N was determined by Kjeldahl digestion (Faithfull 2002). ...
Purpose
Stevia rebaudiana residues composting is studied and optimized using a central composite experimental design
Methods
The influence of controllable composting variables [moisture (40–70%), aeration (0.05–0.30 Lair min⁻¹ kg⁻¹), and time (0–50 days)] on the temperature history and the properties of the compost (pH, organic matter) produced to determine suitable composting conditions. Mass balance and emitted gases of all the composting reactors have been done.
Results
Compost with high degradation entails operating at 50 days of composting under high moisture content (70%) and aeration level with values close to 0.05 Lair min⁻¹ kg⁻¹. Moreover, the composting process kinetic for Stevia rebaudiana residues has been studied. The magnitude of the kinetic parameters on the studied conditions varies among 1/42 and 1/46 for 1/K1 and 0.15 and 1.6 for K2. Where 1/K1 is a value that measures the affinity between microorganisms and substrate and K2 depends on the composting variable optimization.
Conclusions
Both moisture and aeration affects positively and negatively the composting process. Moreover, low effect of aeration has been found. The values of 1/K1 and K2 obtained showed higher values (higher degradation kinetic) under 55% moisture content and 0.30 Lair min⁻¹ kg⁻¹.
... Composting is a common treatment for biodegradable waste which could be an important technology in developing countries where waste materials usually have a high content of wet organic materials (Boldrin et al., 2009). Composting is the biological decomposition and stabilization of organic substrates, under conditions that allow the development of thermophilic temperatures as a result of biologically produced heat, to produce a final product that is stable, free from pathogens and can be useful, when applied to the land (Haug, 1993; Kianirad et al., 2010). Composting is also a possible alternative for treating solid organic wastes and the end products could be reutilized for land application (Wong et al., 2001). ...
... d products which acted as slowrelease fertilizers for agricultural purposes (Hao et al., 2004). A decrease of C/N ratio in the compost in comparison with the initial organic substrate may be due to a relative increase in the nitrogen content on loss of dry matter as carbon dioxide is emitted and water is lost by evaporation during min- eralization. Kianirad et al. (2010) further confirmed that the C/N ratio decrease during composting is sometimes used to indicate compost stability, which agreed with the findings of the present study. The C/N ratio changes during the composting process are shown inFigure 3. Boldrin et al. (2009) also remarked that the danger inherent in the C and N decomposition is that ...
Solid waste comprised of a grass clippings mixture was decomposed using a locally-made compost bin in Pulau Pinang, Malaysia, to eliminate challenges associated with improper waste disposal. Bulk density, pH, moisture content, nutrients content, nitrogen (N), phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu) and carbon/nitrogen (C/N) ratio were determined over 77 days. A 34% reduction in compost bin volume was observed and bulk density and pH were also reduced from 732 to 482 kg m(-3) and 7.82 to 8.41, respectively, indicating fairly good performance. The final moisture content and C/N ratio were 44.06% and 14 : 1, respectively, and the results also showed that the presence of nutrients and heavy metals in the final compost were within acceptable limits for use as a soil conditioner. Final concentrations of N, P and K were 347 mg kg(-1), 510 mg kg(-1) and 14.8 g kg(-1) and for heavy metals, Fe, Zn and Cu were 5308, 300 and 20 mg kg(-1), respectively, which considerably assisted in the decomposition process. Processed waste materials from the bin were shown to be excellent organic fertilizers with over 75% germination index for seeds grown into bean sprouts in 72 h. An improved bin design to eliminate greenhouse gas emission into the environment is suggested.
... Comparing the time required to finish the composting process, the quality of end-product obtained (based on extent of degradation of waste, final C/N ratio and texture and structure of the final compost) coriander compost with feathers was found to be the best supplement for composting of such highly keratinoluytic waste. Similar investigations were also conducted by Kianirad et al. (2010) and Lalremruati and Devi (2021). ...
There is a growing need for economical and environmentally responsible ways to valorizing poultry feather waste, and keratinolytic bacteria show significant promise. A single strain of Bacillus pumilus NM03, which was isolated from living poultry and has been shown to have substantial keratinolytic characteristics, degrades feathers. In this work, the effects of temperature on the quality of compost prepared with wheat and coriander straw were assessed both alone and in combination with thermophilic microbial inoculation. Temperature @ 37°C + inoculum significantly reduced total nitrogen loss (56.20 and 69.80%) and total organic carbon degradation (47.06 and 62.41%) in coriander and wheat straw composting, respectively, when compared to temperature @37°C. For different regression models, the higher and lower R2 values were estimated for the linear-linear and log logistic models for coriander with feather composting, and the linear-linear and linear models for wheat with feather composting, respectively. The principal component loading matrix obtained from correlation matrix reveals that the first three components whose eigen values are greater than 1, together account for about 91.70% and 87.69 % of the total explained variance in coriander and wheat with feather composting, respectively. Furthermore, our results showed that temperature @ 37°C + inoculum were most suited for feather composting with wheat and coriander straw for total organic carbon and total nitrogen breakdown was expedited for increased bacterial richness and diversity, as well as Bacillus pumilus overrepresentation. The quality of end-product obtained based on final C: N ratio coriander compost with feathers was found to be the best supplement for composting of such highly keratinoluytic waste.
... Thus, controlling NH 3 emissions during composting is crucial for reducing environmental risks and improving compost quality. NH 3 emissions during composting are mainly influenced by factors such as temperature (Kianirad et al. 2010), pH , moisture content (Ding et al. 2019), aeration rate (Zhang et al. 2013), and C/N ratio (Jiang et al. 2011). Adjusting composting materials, environmental conditions, and process parameters can be costly and challenging. ...
The significant volatilization of NH 3 during aerobic composting causes nitrogen (N) losses and environmental risks. Both iron (Fe) and biochar (BC) can influence the N conversion process in composting. Fe application can delay the maturation of materials, while biochar can enhance the quality of organic fertilizer. The combination of these two conditioners may help decrease NH 3 emissions and improve organic fertilizer quality. Therefore, this study investigates the effects of different doses of FeCl 3 and BC on NH 3 emissions and organic fertilizer quality during composting. The results demonstrated that Fe/BC co-conditioners reduced the accumulation of NH 3 emissions during composting by 11.1–48.2%, increased the total nutrient content by 0.6–15.3%, and enhanced economic and environmental benefits by 0.1–23.6 $ t ⁻¹ . At the high-temperature stage of composting, Fe/BC co-conditioners decreased the pH by 0.3–1.2, but there was no significant difference compared to the control at the end of composting, and they did not affect compost maturation. The structural equation model analysis suggested that the reduction in NH 3 emissions was related to ammonia-oxidizing bacteria (AOB), NH 4 ⁺ –N, and total nitrogen (TN). As a result, the Fe/BC co-conditioners reduced NH 3 emissions by lowering the pH at the beginning of composting and increasing the content of NH 4 ⁺ –N. This study concludes that Fe/BC co-conditioners could complement each other to significantly reduce NH 3 emissions and improve the quality of organic fertilizers.
Graphical Abstract
... Temperature directly impacts the microorganisms in the pile and microbial community structure, and it further affects the decomposition and decay process of organic matter [22]. The composting process must reach a relatively high temperature and last for a certain duration to ensure that pathogenic bacteria are destroyed. ...
Large amounts of NH3 and H2S are emitted during sewage sludge composting, resulting in odor pollution. This composting experiment was carried out using sewage sludge mixed with sawdust, and different amounts of zero-valent iron (ZVI) were added to investigate the effect on volatile gases, such as NH3 and H2S, and to analyze the effect on the available sulfur, total sulfur, moisture content, and germination index of the compost. The results showed that the addition of ZVI during the composting process had noticeable effects on the emission of NH3 and H2S. ZVI could also increase the heating rate and peak temperature of the pile, reduce the available sulfur loss, and promote the dewatering and decomposition of the compost pile. The addition of 3% ZVI had the best effect on NH3 emissions; it reduced the peak concentration of NH3 release during composting by 21.0% compared to the blank group. However, the addition of 2% ZVI was the most effective for H2S emissions; it reduced the peak release concentration of H2S by 20.0%. A higher addition of ZVI was more effective in reducing the moisture content and increasing the germination index of the compost.
... Temperature directly affects the activity and microbial community structure in the pile, which, in turn, affects the decomposition rate and the decay process of organic matter [27]. The composting process must reach a specific temperature and last for a certain amount of time to kill pathogenic bacteria. ...
Odor released from the sewage sludge composting process often has a negative impact on the sewage sludge treatment facility and becomes a hindrance to promoting compost technology. This study investigated the effect of adding KNO3 on the emissions of volatile sulfur compounds, such as hydrogen sulfide (H2S), dimethyl sulfide (DMS), and carbon disulfide (CS2), during sewage sludge composting and on the physicochemical properties of compost products, such as arylsulfatase activity, available sulfur, total sulfur, moisture content, and germination index. The results showed that the addition of KNO3 could inhibit the emissions of volatile sulfur compounds during composting. KNO3 can also increase the heating rate and peak temperature of the compost pile and reduce the available sulfur loss. The addition of 4% and 8% KNO3 had the best effect on H2S emissions, and it reduced the emissions of H2S during composting by 19.5% and 20.0%, respectively. The addition of 4% KNO3 had the best effect on DMS and CS2 emissions, and it reduced the emissions of DMS and CS2 by 75.8% and 63.0%, respectively. Furthermore, adding 4% KNO3 had the best effect from the perspective of improving the germination index of the compost.
... Another finding by Wan et al. [15] revealed that the addition of a microbial cocktail inoculum consisting of Bacillus licheniformis, Bacillus amyloliquefaciens, Bacillus megaterium, Bacillus pumilus, Geobacillus pallidus, Ureibacillus thermosphaericus and Paracoccus denitrificans which were isolated and cultivated from chicken manure and maize straw compost itself enhanced the thermophilic phase of composting process with maximum temperature reaching 68 • C as compared to the control treatment with only 60.8 • C as the maximum temperature. Due to this, the germination index increases as high temperature reduced the phytotoxicity effect and thus contributed to the better maturity level of the compost [89]. Previously, Zhang et al. [80] reported the inoculation of enriched ammonia-oxidizing bacteria successfully reduced ammonia emission by 53% of total ammonia than uninoculated compost by promoting ammonia transformation into nitrate. ...
Composting is an important technology used to treat and convert organic waste into value-added products. Recently, several studies have been done to investigate the effects of microbial supplementation on the composting of agro-industrial waste. According to these studies, microbial inoculation is considered to be one of the suitable methods for enhancing the biotransformation of organic materials during the composting process. This review provides up-to-date research findings on microbial inoculation strategies and their role and functions in enhancing the composting process and the improvement of compost quality. Based on this review, the addition of microorganisms could enhance the composting process such as accelerating the organic matter degradation, mineralization and microbial enzymes activities, and the quality of the end-products such as high germination index. It is important to notice in this strategy that sludge’s microbial consortium is feasible to enhance the composting process in pilot-scale and industrial-scale productions. Besides, it also reduces the cost of compost production. The findings of this review show the various positive impact of microbial inoculation on agro-industrial waste composting which in turn might be useful as a reference for selecting a suitable inoculum based on the type of waste materials.
... In cold regions, the composting period and composting quality are essential factors that affect the economic benefits of the composting process (Kianirad et al. 2009). The maturity of compost can be defined as the degree of completion of the composting process, which can be quantified by the degree of formation of humus in the final compost product (Onwosi et al. 2017). ...
This review investigates the significant challenges of the process of livestock manure composting in cold regions and assesses the critical features related to the quality of the final compost product. Recently, the composting process has grasped more attention because of environmental pollution concerns and seeks for environmentally-sound approaches for managing livestock manure. Despite recent progress in crucial areas like the microbiology of compost, further improvement is needed in composting process monitoring. Therefore, specific obstacles related to livestock manure composting in cold regions, such as the generation and preservation of temperature, and the solution of obstacles such as inoculation of coldadapted microorganisms, and the role of biochar in prolonging the thermophilic stage of composting were reviewed. Also, the challenges were adequately addressed, and promising strategies to improve composting of livestock manure under harsh conditions were proposed. Still, there is a need for more investigation to get a better understanding of the role of microbial inoculants and biochar amendment regarding the start-up of the composting process in cold regions.
... A relação C/N do início do processo foi de 18,3/1, valor este semelhante ao encontrado por Yang et al. (2008) com valores iniciais de 19,8/1. Por outro lado, Kianirad et al. (2010) observaram, trabalhando com compostagem de resíduos de Tabela 1. Temperatura média da leira e pH das amostras de cada coleta de resíduo em processo de compostagem espigas de milho, que a relação C/N variou de 38 no estágio inicial, a 13,9 ao final do processo. Kurola et al. (2011) obtiveram valores acima de 25/1 em um experimento de compostagem com a adição de cinzas de madeira. ...
The composting technique is a promising alternative for the treatment of solid organic residues, along with the sludge produced in sewage treatment plants. The final compost might show fertilizer properties, which can be used to recover poor soils. The high temperatures that the composting process can achieve are responsible for the reduction of the pathogenic microbial population, helminth eggs and virus present in the beginning of the process. This behavior assures the microbial quality of the compost according to the 375/2006 Resolution of the CONAMA. The aim of this study was to evaluate the influence of temperature on Escherichia coli, Salmonella sp., helminth egg and enteric virus presence in the final product from a composting process. For this matter colimetric assays were performed together with the seedling of the samples in different culture media, the assay for helminth eggs visualization under the microscope and the identification of enteric virus. The results showed an oscillation on E. coli and heterotrophic bacteria counts, even after the thermophilic phase. On the other hand, Salmonella sp., helminth eggs and enteric virus were not found in the final compost.
... A wide range of organic waste can be composted for use as growing media: municipal solid waste, sewage sludge, poultry litter, chicken manure and other animal excreta, poppy straw, cotton gin trash, and waste from the food and processing industry. The latter includes apple pomace (Chong, 1992), corn cobs (Kianirad et al., 2009), cotton gin waste (Krewer et al., 2002), grape marc (Reis et al., 2003), grape stalks (Tattini et al., 1992), olive marc (Pages et al., 1985), olive-mill waste (Papafotiou et al., 2004 and 2005), sugarcane fibre or bagasse (Cintra et al., 2004) and vegetable residues (Vallini et al., 1992). Prasad and Maher (2001) recommend using composted materials such as green waste and biowaste as a component of a growing medium (up to 50 percent) but not on their own. ...
This chapter examines growing media used in soilless culture; they represent
one of the main solutions for soil problems, have positive effects on the
environment and improve fertilizer and water-use efficiency. This is especially
the case in Mediterranean countries where shortage of good quality water is a
major constraint in protected cultivation. At present, a relatively small proportion
(approximately 10%) of growing media – which are very important for a good start
to plant cultivation – can be used for the production of seedlings and transplants.
... In fact, the soil CEC usually displays values parallel to those of soil C (Skyers et al., 1970;Rashidi & Seilsepour, 2008). Although mainly used for the assessment of composts quality (Hachicha et al., 2009;Kianirad et al., 2009) a high CEC:C ratio could be considered a good indicator of well-humified SOM, as opposed to the less evolved types of humus, where the contribution to the CEC by C unit is much less (Garcı´a-Go´mez et al., 2005;Melo et al., 2007). This index should be especially useful for cultivated soils, where the classical C:N ratio usually used to estimate humus quality is not biased by fertilization. ...
Quantitative changes in soil organic matter (SOM) from undisturbed Mediterranean forests and neighbouring deforested sites were assessed by analysing soil lipids and humic acids (HAs), in total studying 80 variables. Changes in the composition of free lipids reflected vegetation types, whereas HAs analysed by visible and 13C NMR spectroscopy, sodium perborate degradation and Curie-point pyrolysis indicated the extent of structural alteration of lignin in soil. The molecular fractions released by degradation techniques applied to HAs showed that demethoxylation and oxidation were associated with the removal of forest vegetation, and the aromatic compounds consisted mainly of methoxyphenols and benzenecarboxylic acids. Decreased concentration of alkanes and increased amounts of alcohols were observed after removal of forests. The chain lengths of alkyl compounds also tended to decrease. In forest soil, there was a series of diterpene resin acids, whereas in pasture soil steroids from animal origin and a root-derived triterpenoids with friedelan structure were found. In relation to the total quantity and quality of soil C, the overall chemical descriptors indicated that clearing and cultivation (semiarid cereal fields) lead to intense mineralization of SOM (mainly particulate, free organic matter) but the residual humic substances have enhanced maturity in terms of structural condensation and potential resilience. Conversely, the cleared forest soil under pasture had a comparatively higher potential for C sequestration, but the HA characteristics suggested selective preservation of plant biomacromolecules directly incorporated as underground biomass.
Humic substances (HS) are important product during composting, which play a key role in the maturity of compost, and its electron transfer characteristics have significant applications in the reduction of pollutants. We focus on the structure and composition characteristics and formation mechanism of HS during the composting. The effects of composting raw materials, additives, microorganisms and oxygen supply conditions on the formation of HS were reviewed. The electron transfer mechanism of compost HS was summarized as well as the structural and environmental factors affect the electron transfer of HS. The applications of HS in soil pollution control and water treatment are introduced. The research directions of HS formation mechanism, electron transfer mechanism and its application are also prospected.
As a prerequisite additive, bulking agent played an essential role on organic wastes biodrying by affecting the organics degradation and microbial consortia. In this study, a series of experiments were conducted to explore the relationships among the type of bulking agents, organics degradation and microbial community evolution. In line with the excellent physiochemical properties, corncob was found to be more desirable for biodrying with more water removal (62.13% vs. 53.70% for sawdust and 51.72% for straw)and higher energy efficiency. Furthermore, different bulking agents showed different biodegradability and affected co-existed organics degradation. In detail, corncob upgraded the amylase and lipase activities, thus promoting the degradation of readily degradable carbohydrates and lipids in feedstocks, which accounted for >60% of the bio-heat sources for water evaporation. In addition, pyrosequencing analysis revealed that Bacillus (>50%)and Ochrobactrum (>40%)were the dominant genera in thermophilic and cooling phases, with degradation capacities of readily degradable substrate and lignocellulose, respectively. And the pathogens, e.g., E. coli and K. pneumonia, were seriously inhibited by high matrix temperatures in corncob trial. These results not only suggested the corncob was a promising bulking agent, but the potential microbial mechanisms for organics degradation were also revealed.
The decomposition of green waste and brown waste in relative proportions of 1:1, 2:1 and 3:1 was studied in three successive experiments conducted at Desasiswa Bakti Permai, Universiti Sains Malaysia, Penang. The research involved the determination of the quality of compost produced from the different mixture ratio of green waste and brown waste. Three different 200L capacity reactor that made of 4mm thick poly vinyl chloride (PVC) was used as a Semi Passive Aerated Reactor. Temperature and pH were controlled over 89 days (three months) of composting process. Moisture Content, Calorific Value, C:N ratio and Germination Index of the compost product were analyzed. The final moisture content were 23%, 32% and 54% while the final C:N ratio were 23,21 and 14 respectively. The recommended mixture ratio for composting are in relative proportions 3:1 with final C/N ratio of 14 with Moisture content of 52% and 75% germinated seeds.
One of the main analytical variable to indicate the evolution and the phases of the composting process is temperature, whose constant monitoring is fundamental for decision making. However, studies usually perform collection of temperature data with a daily frequency due to the operational difficulty in obtaining this information from manually collected samples. Thus, the objective of this work was to determine the ideal frequency of temperature data collection in composting layers. Eight composting layers containing tree prunings + domestic organic residues were installed and four temperature sensors were installed in each layer. The temperature data were collected and recorded from minute to minute by means of a datalogger developed with an Arduino board during 70 days of composting. Thus, the collected temperatures were used as a pilot sample, and therefore the ideal temperature collection rate was estimated for different estimation error limits. No significant difference was found between the different collection times according to the Kruskal-Wallis test at a significance level of 5%. Therefore, the ideal collection frequency can be determined from the error limit of temperature estimation that is acceptable to the researcher.
The aim of this work was to investigate the sintering characteristics and mineral transformation behaviors of three corn cob ashes using a combination of inductively coupled plasma–atomic emission spectroscopy (ICP–AES), ash fusion analysis, X-ray diffraction (XRD), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX). The sintering degrees of the corn cob ashes at elevated temperatures were graded by performing laboratory-scale sintering tests. The WCob ash has a significantly low melting temperature of 834 °C and showed severe sintering behaviors during testing. The SEM–EDX and XRD analyses revealed that the fused WCob ash consisted of a mixture of potassium-rich silicate–phosphate melts. The WCob is dominated by potassium, silicon, and phosphorus, along with small amounts of alkali earth metals. Therefore, the formation and melting of potassium-rich silicates and phosphates are favored, causing severe sintering of the WCob ash at elevated temperatures. In contrast, a relatively higher melting temperature of 998 °C and a moderate sintering degree were observed from the PCob ash. High contents of chlorine, calcium, and magnesium in the PCob may promote potassium release from ash residues, instead of being incorporated into the silicate and phosphate structures. This process could inhibit the formation of low-temperature-melting silicates and phosphates and reduce ash sintering consequently. The abundance of calcium and magnesium in the PCob also led to the formation of high-temperature-melting silicates and phosphates, restraining ash melt formation and the extent of ash sintering. Results from the experimental work and analyses indicate that the combustion of corn cob may be challenging because of ash sintering. The transformation and melting behaviors of corn cob ashes are highly dependent upon the fuel compositions.
Electron transfer capacity (ETC) of dissolved organic matter (DOM) is proposed as the maturity index to predict the composting status, based on the fact that the compositions of DOM strongly associate with the degree of decomposition. ETC, including electron accept capacity (EAC) and electron recycle rate (ERR), increases as the composting goes on, showing a close correlationship with the germination index (GI). The correlation coefficient between EAC and GI is 0.9273, and that between ERR and GI is 0.9501. The measurements of these ETC parameters require no chemical reagent preparations before analyses and can be obtained very rapidly. The results of this study indicate that these simply and rapidly obtainable ETC parameters can be potential alternatives to evaluate the composting process.
Potato starch foam trays based on blends of poly(vinyl alcohol) and corn fibers (CFs), co-product of the corn-wheat wet-milling process, are prepared by baking the blended mixtures in a preheated mold. Materials are evaluated for processing parameters, foam strength, flexibility, and water resistance as a function of fibers content. Addition of CF in formulations improved not only moisture resistance of foam, but has a potential to lower the overall cost of the foamed materials substantially. Interestingly, addition of up to 45% fiber in formulations was possible without compromising the foaming process. Degradability is evaluated both in compost than simulating a disposal in the environment (soil burying and soil surface). Trays are biodegraded within 30—60 days in compost and soil. Particularly, trays containing starch and fiber degraded at much faster rates than trays prepared using starch without natural fillers.
We studied a compost made of poultry manure, olive mill wastes and mineral-rich wastewater, as an alternative fertiliser. The composts were of high quality, characterized by high levels of nutrients, a relatively low C/N ratio of 15–17 and a fertilizing value similar to that of conventional cattle manure, however without phytotoxicity. Field experiments showed an increase in potato production of 31.5–35.5 t/ha, compared to 30.5 t/ha using cattle manure. The use of olive mill wastewater did not have any negative impact on soil pH, electrical conductivity and phenols. The compost made of poultry manure and olive mill by products appears therefore as a promising ecological alternative to classical fertilizers.
Compost product safety and quality assurance are required to meet the needs of the horticultural, agricultural, and silvicultural user markets. At present, there exist no industry-wide sampling and testing protocols for compost products, thus limiting the production sector. The objective of this research was to test three methods for determining compost maturity. The study followed the composting process of a locally successful commercial composting operation that had been producing lime-stabilized biosolids compost in the Washington, DC metro region for 12 yr. Change over time in the dependent variables--Dewar flask self-heating capacity, oxygen uptake rate, and cation exchange capacity (CEC)-during a 57-d composting of lime-stabilized biosolids was studied. Because cold storage at 4 degrees C is recommended when compost samples cannot be tested for maturity immediately, cold storage of up to 11 wk was included as a variable. Mathematical models were developed that predict change in the Dewar flask self-heating capacity, oxygen uptake rate, and CEC with composting time and storage at 4 degrees C. The Dewar flask self-heating test was the most useful indicator of compost maturity. This test showed change throughout the 57-d biosolids composting period while oxygen respirometry did not change after 29 d. The CEC was found to increase with age and storage. Storage effects varied for the different tests. Except for Days 1 and 57, composts continued to stabilize during storage. Testing stored composts may produce erroneous results that suggest the compost is mature.
Characterization of soil-applied organic material is necessary in order to clarify the nature of the organic matterand nutrients in it. In this study, the organic matter and nutrient contents of the spent pig litter (a mixture of partially decomposed pig manure and sawdust) was characterized before and after windrow composting to: (1) determine their changes during composting, and (2) assess the suitability of the composted spent litter as a soil amendment. Results demonstrated that the time required to reach maturity, and the composition of composted spent litter, depended on the chemical properties of the initial compost feedstock as well as the compost strategies used during composting. Total N, P, and K concentrations of the composted litter depended on chemical properties of the initial material. On the other hand, C:N ratio, humic and fulvic acid and cation-exchange capacity were influenced by differences in composition of the initial spent litter and composting strategy. If moisture content was maintained weekly at 60% with a four-day turning frequency, the litter reached maturity in 56 days. Maturation of spent litter was accompanied by a decline in total C, water-extractable metals, NH(4)(+)-N, increase in ash, (NO(3)(-)+NO(2)(-)-N, humic acid, humic acid:fulvic acid ratio, and cation exchange capacity, and elimination of phytotoxicity. The stability of nutrient and organic matter, acceptable pH and electrical conductivity values, and low levels of undesirable components such as heavy metals and phytotoxic compounds of the spent litter provided substantial evidence that agronomically suitable compost can be obtained after composting in windrows.
Accumulation of dairy manure compost has created a need to identify alternative uses for this plant nutrient source. This field study determined compost effects on corn (Zea mays L.) silage production, nutritive value, and soil characteristics for three growing seasons following incorporation of dairy manure compost at 0, 35, 70, and 105 Mg dry matter (DM) ha(-1). Yields from subplots receiving annual split applications of supplemental inorganic N at 224 or 336 kg ha(-1) yr(-1) were not different. Compost at 35 Mg ha(-1) with supplemental inorganic N fertilizer produced equivalent amounts of DM to that of conventional inorganic fertilizer (IF: 336-49-93 kg ha(-1), N-P-K) for the first 2 yr. By the third year, the IF treatment produced 17% more DM than the 105 Mg compost treatment (pooled across N rates). Corn silage nutritive values generally did not differ among compost and IF treatments. By the third year, compost applications >35 Mg ha(-1) raised soil pH 2.3 units and increased electrical conductivity (EC) 50% compared to IF. Three years after compost application, soil P and K concentrations were still greater in plots receiving 70 and 105 Mg compost ha(-1) compared to both the check and IF plots. Soil organic matter (OM) increased with compost rates over 35 Mg ha(-1) the first season after application, but did not differ after the second season compared to IF. Compared to IF, dairy manure compost can improve soil nutrients for 3 yr; however, it can also increase soil EC and pH, which may be beneficial or detrimental.
Food industry will have to focus on waste avoidance as well as utilisation of process waste. Application of clean technologies greatly enhances the safety and quality of the product as well as reducing the energy requirements and environmental impact of the food industry. The main environmental impacts of the food sector are aquatic, atmospheric and solid waste emissions. Nowadays, the main treatment method of solid wastes is composting, while recovery and reuse of by-products and wastes as raw materials stand for another effective option (http://www.oulu.fi/resopt/wasmin/pap.pdf). Composted olive oil waste can find applications (1) as amendment in agriculture because of its high nitrogen and phosphorus content, (2) as a biofertiliser, with a mixture of compost with Sphagnum peat or commercial substrate finding use for ornamental plants growth and (3) as a biofilter for toxic metal removal. However, there are a number of disadvantages as well, such as large decline of soil germination capability, necrosis of the leaves and slow emission of secondary stems, and enhanced phytotoxicity, because of pH neutralisation technique, which should be seriously taken into account prior to opting for composting as a promising waste treatment alternative.
Although corn and rice waste can be hardly classified among the most hazardous waste, their treatment is very important in view of the great volume of waste materials involved. In this review article, an update is provided for most of the waste treatment techniques (composting, pyrolysis, gasification, combustion) used to alter the physical, chemical or biological character of the waste, to reduce its volume and/or toxicity and to make the waste safer for disposal. Furthermore, all current and potential uses of treated corn and rice waste such as fertilisers, biomass and biogas/biofuel are summarised. Four comprehensive tables and six figures provide a thorough presentation of both waste treatment methods (characteristics, advantages and disadvantages) and uses of treated corn and rice waste.
A method for determining the cation-exchange capacity (CEC) of organic matter was developed by modifying the BaCl2 triethanolamine, pH 8.1, method used in calcareous soils. Problems arising from the presence of sulphates and losses of water
soluble organic matter were solved. The proposed method for organic matter is comparable to that of soil in terms of sensitivity,
reproducibility and in the time necessary for each analysis. In the second part of the work the CEC's of diverse organic samples
were determined and found to be reproducible with an average coefficient of variation of 3.56%.
Despite numerous investigations of the maturation process of composts, a simple and straightforward parameter which can predict plant response upon compost application has yet to be defined. In light of results accumulated over a decade, we examined simple, chemical parameters of three composts from three types of source materials (municipal solid waste (MSW), separated cow manure (CSM), biosolids (BS)). These materials were composted using different procedures and facilities. The chemical parameters were correlated to the growth response of cucumbers or ryegrass sown in potting media amended with the composts sampled at different stages of the process. The dissolved organic carbon (DOC) concentration of all composts decreased rapidly within the first month, then, towards the end of the process, stabilized at concentration below 4 g kg−1. DOC correlated highly and significantly to the absorbance at 465 nm in all composts, and also to the C/N ratio. Nitrate evolution was similar in all composts, but the final concentrations differed among them. Plant biomass increased with composting time. For CSM and BS compost maximum biomass was reached when the DOC reached levels below 4 g kg−1. DOC concentration is suggested for use as a simple method of determining maturity, with 4 g kg−1 recommended as a threshold level indicating maturity. Absorbance at 465 nm can be used instead of DOC concentration after appropriate calibration.
Seven different composts were prepared in a pilot plant by the Rutgers static-pile system using a wide range of wastes: sewage sludge, poultry manure, pig slurry, olivemill wastewater, city refuse and the lignocellulosic wastes cotton waste, maize straw and sweet sorghum bagasse. Their chemical and biological properties were studied at four stages of the composting process: in the initial mixture, at the thermophilic phase, at the end of the active phase and after two months of maturation. The following maturity indices were established: C/N < 12, Cw < 1.7%, Cw/Norg < 0.55. NH4/NO3 < 0.16, and NH4-N < 0.04%, with a germination index greater than 50%. In addition, some carbon mineralization parameters could also be used as maturity indices: mineralized-C in 70 days (Cm) < 30%, rapidly mineralizable-C (CR) < 7.2% and a slow mineralization rate (CS × KS) < 0.35% day−1. Maturation indices based on humification of the organic matter and the cation exchange capacity of different composts could not be found, since the values for mature compost depended on the wastes from which the composts were made.
A composting experiment was carried out to study which are the best parameters to use as indicators of the degree of compost maturity, and to determine ‘humification’ indices for practical use.The following parameters were selected: cation exchange capacity (CEC), carbon/organic nitrogen ratio in water extract (), ratio in solid phase (), total organic carbon (Ct), oxidizable carbon (Co), alkaline-extractable carbon (Cex), humic and fulvic-like carbon (Cha, Cfa) humification ratio (), humification index (), percent humic acid () and ratio.The regression analysis shows that the carbon (total and oxidizable), and ratio are correlated with a level of significance higher than 99.5%. From the integration of the deduced values, applying the obtained equations sequentially, the optimal values of these parameters to assure an acceptable degree of maturity of the compost are: mEq per 100 g (on an ash-free basis), and Pha > 62%.
Bulking agents and bedding materials used on farms for composting manures affect the time required for composts to mature. The effects of these materials on guidelines for the use of composted manures in potting mixes are not fully known. Several chemical and biological compost characteristics were mentioned and a cucumber plant growth greenhouse bioassay was performed on samples removed from windrows during composting of: (i) dairy manure amended with wheat straw; (ii) dairy manure amended with sawdust (mostly Quercus spp.); and (iii) pig manure amended with sawdust and shredded wood (mostly Quercus spp.). Dry weights of cucumber seedlings grown in fertilized and unfertilized potting mixes amended with composts (30%, v/v) having stability values of <1 mg CO2–C g–1 dw d−1, did not differ significantly from those in a control peat mix. Only the most mature dairy manure-wheat straw compost samples consistently established sufficient N concentrations in cucumber shoots in unfertilized treatments. For the dairy manure-wheat straw compost, all possible subset regression analyses of compost characteristics versus cucumber plant dry weight revealed that any of several compost characteristics (electrical conductivity-EC, compost age, total N, organic C, C-to-N ratio, ash content, CO2 respirometry, Solvita CO2 index and the Solvita® Compost Maturity Index) predicted growth of cucumber in the unfertilized treatments, and thus maturity. In contrast, at least two characteristics of the dairy manure-sawdust compost were required to predict growth of cucumber in the unfertilized treatments. Effective combinations were EC with compost age and the Solvita® maturity index with total N. Even five compost characteristics did not satisfactorily predict growth of cucumber in the non-fertilized pig manure-wood compost. Nutrient analysis of cucumber shoots indicated N availability was the principal factor limiting growth in potting mixes amended with the dairy manure-sawdust compost, and even more so in the pig manure-wood compost even though the compost had been stabilized to a high degree (<1 mg CO2–C g−1 dw d−1). Maturity of the composted manures, which implies a positive initial plant growth response of plants grown without fertilization, could not be predicted by compost characteristics alone unless the bulking agent or bedding type used for the production of the composts was also considered.
We examined the possibility of cultivating Agaricus bisporus (Ab) on various grains and agricultural by-products, with the objective of improving yield capacity of substrate pre-colonized by Scytalidium thermophilum (St). Radial growth rate (RGR) of St at 45 degrees C ranged from no growth on sterile wheat grain to 14.9 mm/d on whole oats. The linear extension rate (LER) of Ab, grown on St-colonized substrate (4 days at 45 degrees C), ranged from a low of 2.7 mm/d on 100% corncobs to 4.7 mm/d on a 50/50 mixture of ground corncobs/millet grain. Several other substrates containing wheat straw+ground corncobs+boiled millet and pre-colonized by St (4 days at 42+/-3 degrees C), were evaluated for production of Ab. The biological efficiency (BE) of production increased linearly with the addition of millet to the formula. However, substrates with millet levels 84% often were contaminated before mushroom harvest. Maximum BE (99%) and yield (21.6 kg/m(2)) were obtained on St-colonized wheat straw+2% hydrated lime supplemented with 9% commercial supplement added both at spawning and at casing.
The composting of olive press cake (OPC) repeatedly mixed either with olive mill wastewater (OPC+OMW) or with tap water (OPC+W) was studied using the thermogradient respirometer, an apparatus that determines the respiration rates from a substrate over a wide range of different temperatures (respiratory profile). The composting processes took place over a period of five months during which nine moistenings of the OPC were performed with the respective liquids. The composting resulted in detoxification of the materials used in both treatments, as indicated by seed germination tests. However, the repeated applications of OMW resulted in recurring thermophilic phases (following each application) and in greater pH and conductivity increases in the final product, as compared to water applications. Respiration measurements performed at 35 degrees C were good indicators of the mean metabolic potential in the compost piles (the mean respiration derived from the whole respiration profile over a wide range of environmental temperatures). However, respiration measurements at higher temperatures (48.5 degrees C) were better indicators of the respiration activity occurring in situ. Following the initial thermophilic phase, the respiration potential of the composts at high temperatures (42-63 degrees C) increased drastically compared to their respiration potential at lower temperatures (17-42 degrees C) indicating the establishment of a thermophilic microflora. Subsequently, only the periodic new substrate-C applications in the form of OMW resulted in increased ratios of low temperature-to-high temperature respiration potential. These ratios decreased again following the respective thermophilic phase that each new OMW application had induced.
Composting organic matter is an interesting way to valorize waste. Compost is a product obtained after a humification process. The humification of organic matter during composting was studied by the quantification and monitoring of the evolution of humic substances. The final objective was to be able to evaluate the state of humification based on a spectrum of total humic substances using the method of UV spectral deconvolution. This study presented a new index obtained by UV spectroscopy using the deconvolution of an unknown spectrum of compost with 3 reference spectra. This index was compared to the maturity indices usually used, such as total extraction of humic substances (rate of extraction), IP (index of polymerization) or the humic acid to fulvic acid ratio. This new parameter, which was easy and quick to determine, gave precise information about the quality of the compost. It made it possible to disregard the values of aberrant concentrations caused by the classical protocol of extraction. Compared to the humic acid to fulvic acid ratio, the new index obtained by UV spectral deconvolution showed more representative results: the humic acid to fulvic acid ratio for an apparently non-mature compost was abnormally high, suggesting that the compost was mature, whereas the UV index proposed showed that the compost was really young and not yet humified.
In this study changes in the properties of natural organic matter (NOM) were studied during composting of sewage sludge in a laboratory experiment using the pile method. Typical physicochemical parameters were measured during 53 days of composting including humic fractions. The effects of humification on the molecular properties of humic acids (HA) were investigated by 13C CP/MAS NMR spectroscopy. On the basis of chemical analyses, 53 days of composting sewage sludge with structural material can be divided into three phases: (i) domination of rapid decomposition of non-humic, easily biodegradable organic matter (two to three weeks), (ii) domination of organic matter humification and formation of polycondensed, humic-like substances (the next two weeks), (iii) stabilization of transformed organic material and weak microbial activity. Spectroscopic characterization (13C NMR) of compost humic acids reveals changes in their structures during maturation. The changes are highly correlated with the processes taking place in bulk compost.