Biomass ash reutilisation as an additive in the composting process of organic fraction of municipal solid waste

Dynamics of co-composting of pineapple harvest and processing residues with poultry litter and compost quality

The production of pineapple generates significant quantities of harvest and processing residues, which are very little used. This study evaluates compost quality using pineapple residues and poultry litter. Five composting treatments were tested, varying following proportions of crown, pineapple processing wastes (PPW), pineapple harvest residue (PHR), and poultry litter (PL). Various parameters were analyzed, including pH, electrical conductivity, CO2 evolution rate, water content, organic carbon, nitrogen compounds, phosphorus, potassium, calcium, magnesium, copper, and zinc. Additionally, the perceptions of producers and processors regarding compost quality were gathered. Results indicated that microbial decomposition increased temperature, pH, CO2 release, and nitrogen content while reducing electrical conductivity and organic carbon. Composts demonstrated favorable characteristics for crop fertilization, with C4 (75% PHR + 25% PL) compost showing the best chemical properties. Producers and processors preferred the color, odor, and structure of C4 (75% PHR + 25% PL) and C5 (56.25% crown + 18.75% PPW + 25% PL) composts. Overall, composting pineapple residues with poultry litter yields composts suitable for plant fertilization, particularly C4 and C5 formulations, offering potential for sustainable waste valorization in agriculture.

A comparative study on compost preparation using lab prepared eco-enzyme and its effect on growth of plant species Phaseolus vulgaris

The augmented rise in population in the last few decades has resulted in gigantic increase in the solid waste production in India and around the globe. The conventional composting methods are slow and sluggish process that has resulted in the advancement techniques for the emergence in new rapid composting processes. Use of eco-enzyme is such a rapid technique that helps to degrade the solid waste in a very accelerative manner. The present study has been carried out by preparing eco-enzyme using the kitchen waste and with the objective to utilize it for degradation of agricultural wastes and preparing compost for its utilization for different plant species as soil conditioner and fertilizer. The prepared eco-enzyme was added during the composting process in each batch with concentration variations of 10%, 15%, and 20% (V/V) once every week. The pH value of the final prepared compost was found to be within the neutral range of 6.51 ± 0.03-7.88 ± 0.50 in all the samples. Overall compost prepared using 10% eco-enzyme has the highest growth promoting effects for Phaseolus vulgaris. The present study will be having twofold advantage as the environment will get rid of such wastes as the same can be utilized as resource and it will also be helpful for the farmers from economical point of view.

Ashes from challenging fuels in the circular economy

In line with the objectives of the circular economy, the conversion of waste streams to useful and valuable side streams is a central goal. Ash represents one of the main industrial side-products, and using ashes in other than the present landfilling applications is, therefore, a high priority. This paper reviews the properties and utilization of ashes of different biomass power plants and waste incinerations, with a focus on the past decade. Possibilities for ash utilization are of uttermost importance in terms of circular economy and disposal of landfills. However, considering its applicability, ash originating from the heat treatment of chemically complex fuels, such as biomass and waste poses several challenges such as high heavy metal content and the presence of toxic and/or corrosive species. Furthermore, the physical properties of the ash might limit its usability. Nevertheless, numerous studies addressing the utilization possibilities of challenging ash in various applications have been carried out over the past decade. This review, with over 300 references, surveys the field of research, focusing on the utilization of biomass and municipal solid waste (MSW) ashes. Also, metal and phosphorus recovery from different ashes is addressed. It can be concluded that the key beneficial properties of the ash types addressed in this review are based on their i) alkaline nature suitable for neutralization reactions, ii) high adsorption capabilities to be used in CO2 capture and waste treatment, and iii) large surface area and appropriate chemical composition for the catalyst industry. Especially, ashes rich in Al2O3 and SiO2 have proven to be promising alternative catalysts in various industrial processes and as precursors for synthetic zeolites.

Effect of forest-based biochar on maturity indices and bio-availability of heavy metals during the composting process of organic fraction of municipal solid waste (OFMSW)

The main objective of this study was to investigate the effect of biochar on the composting process of the organic fraction of municipal solid waste (OFMSW) under real conditions. Different doses of biochar (1%, 3%, and 5%) were mixed with compost piles to evaluate the variation of temperature, moisture content (MC), organic matter (OM), carbon (C), nitrogen (N), C/N ratio, and heavy metal (HM) contents in comparison with the control treatment (with 0% biochar addition). The results of this study showed that the compost piles combined with different doses of biochar had higher MC. The use of biochar as an additive, even at low doses (1%), was able to increase the compost quality through the reduction of N losses during the composting process. The highest reduction of OM during the composting process was observed in the control pile (without biochar addition) by 48.06%, whereas biochar affected the biodegradability of OM and prevented the reduction of nutrients during the composting process under real conditions. The contents of HMs (Pb, Zn, Ni, Cd, and Cu) showed a significant reduction in all of the compost piles combined with biochar in comparison with the control treatment. Considering that in terms of all compost quality indicators, the piles combined with biochar can regarded as high standard product, the composts obtained from combining the OFMSW with different biochar doses have desirable features to be used as an amendment agent to improve agricultural soil quality.

Comparison of the basic processes of aerobic, anaerobic, and aerobic-anaerobic coupling composting of Chinese medicinal herbal residues

Chinese medicinal herbal residues (CMHRs) are waste generated after extracting Chinese medicinal materials, and they can be used as a renewable bioresource. This study aimed to evaluate the potential of aerobic composting (AC), anaerobic digestion (AD), and aerobic-anaerobic coupling composting (AACC) for the treatment of CMHRs. CMHRs were mixed with sheep manure and biochar, and composted separately under AC, AD, and AACC conditions for 42 days. Physicochemical indices, enzyme activities, and bacterial communities were monitored during composting. Results showed that AACC- and AC-treated CMHRs were well-rotted, with the latter exhibiting the lowest C/N ratio and maximal germination index (GI) values. Higher phosphatase and peroxidase activities were detected during the AACC and AC treatments. Better humification was observed under AACC based on the higher catalase activities and lower E4/E6. AC treatment was effective in reducing compost toxicity. This study provides new insights into biomass resource utilisation.

An assessment of the impact of structure and type of microplastics on ultrafiltration technology for microplastic remediation

Microplastic, which is of size less than 5 mm, is gaining a lot of attention as it has become a new arising contaminant because of its ecophysiology impact on the aquatic environment. These microplastics are found in freshwater or drinking water and are the major carriers of pollutants. Removal of this microplastic can be done through the primary treatment process, secondary treatment process, and tertiary treatment process. One approach for microplastic remediation is ultrafiltration technology, which involves passing water through a membrane with small pores to filter out the microplastics. However, the efficiency of this technology can be affected by the structure and type of microplastics present in the water. New strategies can be created to improve the technology and increase its efficacy in removing microplastics from water by knowing how various types and shapes of microplastics react during ultrafiltration. The filter-based technique, that is, ultrafiltration has achieved the best performance for the removal of microplastic. But with the ultrafiltration, too some microplastic that are of sizes less than of ultrafiltration membrane passes through the filter and enters the food chain. Accumulation of this microplastic on the membrane also leads to membrane fouling. Through this review article, we have assessed the impact of the structure, size, and type of MPs on ultrafiltration technology for microplastic remediation, with that how these factors affect the efficiency of the filtration process and challenges occur during filtration.

The Effect of Ash Admixture on Compost Quality and Availability of Nutrients

The effect of graded doses of ash from biomass wood chips and straw admixture combustion on compost properties was investigated through a set of large-scale experiments. In a compost plant, matured organic composts were prepared from raw organic mixtures based on biodegradable waste, separated digestate, straw, and biomass ash admixture of 0, 3, 6, and 9 wt. %. Final composts, as well as individual components, were analyzed for basic physical and chemical properties, total and available nutrients, and potentially hazardous elements. Biomass ash addition increased the total nutrient content (P, K, Mg, Ca, and S) in the studied composts. The highest ash addition (9 wt. %) increased the nutrient content as follows: Ca (2.6×), Mg (1.6×), K (1.5×), P (1.2×), S (1.3×). However, the availability of some nutrients (especially P, K, and Mg) for plant nutrition was reduced by the increasing amount of ash admixture. Even at the highest dosage of biomass ash addition, desirable chemical (nutrient content) and physical properties of composts (especially dry bulk density) were both obtained. The content of hazardous elements was below the legal limit values in all studied composts.

Processes and prospects on valorizing solid waste for the production of valuable products employing bio-routes: A systematic review

Humanity is struggling against a major problem for a proper management of generated municipal solid waste. The collected waste causes natural issues like uncontrollable emission of greenhouse gases and others. Even though, escalation of waste results in minimizing the areas accessible for disposing the waste. Creating awareness in the society to use organic products like biofuels, biofertilizers and biogas is a need of an hour. Biochemical processes such as composting, vermicomposting, anaerobic digestion, and landfilling play important role in valorizing biomass and solid waste for production of biofuels, biosurfactants and biopolymer. This paper covers the details of biomass and solid waste characteristics and its composition. It is also focused to provide updated information about reutilization of biomass for value creation. Technologies and products obtained through bio-routes are discussed in current review paper together with the integrated system of solid waste management. It also covers challenges, innovations and perspectives in this field.

Effect of additives on properties and microstructure of lightweight aggregates produced from MSWI bottom ash sludge

In order to solve problems of land occupation and environment damage resulted from massive municipal solid waste incineration bottom ash sludge (MSWI-BAS), sintered lightweight aggregates (LWA) were prepared from MSWI-BAS. Additives are of great significance for the preparation of high-performance LWA and the utilization of MSWI-BAS resources, so their effect on properties of LWA was investigated. The results showed that when the content of water glass was 20%, compressive strength of LWA reached a maximum of 8.4 MPa, and 1-hr water absorption reached a minimum of 5%. The reason was that the addition of water glass brought a lot of Na⁺ and Si(OH)₄, and the internal crystals of water glass were converted into rod-shaped zeolite crystals, thereby forming a high-density structure. The addition of coal powder led to the formation of gas in LWA, thus reducing the density of LWA. At the same time, it was also conducive to earlier generation of liquid phase in LWA, making its internal structure dense. When the content of coal powder was 5%, 15%, and 20%, the modification effect was better, and compressive strength of LWA was larger, about 4 MPa. Additives are of great significance for the preparation of high-performance LWA and the utilization of MSWI-BAS resources.Implications: In this study, we have prepared LWA with MSWI-BAS. At the same time of X-ray diffractometer (XRD) and FT-IR analysis of raw materials, we also investigated effect of water glass and coal powder on characteristics (particle density, 1-hr water absorption, and compressive strength) of lightweight aggregates, and good results were obtained. For explanations, several characterizations were carried out, such as XRD and SEM. The sludge disposal problem is reduced. It opens up a new way for the utilization of solid waste resources. In addition, it meets with the concept of green development of building materials and makes the production of LWA have a broader development prospect.

A Sustainable Solution to Obtain P-K-Mn Glass Fertilizers from Cheap and Readily Available Wastes

The sustainable economy framework imposes the adoption of new ways for waste reuse and recycling. In this context, this paper proposes a new alternative to obtain glass fertilizers (agriglasses) by reusing two cheap and easily available wastes, wood ash and manganese rich sludge resulting from drinking water treatment processes for groundwater sources. Glasses were obtained using different amounts of wastes together with (NH₄)₂HPO₄ and K₂CO₃ as raw materials. The P-K-Mn nutrient solubilization from the obtained glasses was investigated using a citric acid solution. The kinetics of the leaching process was studied after 1, 7, 14, 21 and 28 days, respectively. The intraparticle diffusion model was used to interpret kinetic data. Two distinct stages of the ion leaching process were recorded for all of the studied compositions: first through intraparticle diffusion (the rate-controlling stage) and second through diffusion through the particle–medium interface. The fertilization effect of the obtained agriglasses was studied on a barley crop. The specific plant growth parameters of germination percentage, average plant height, biomass and relative growth rate were determinate. The positive impact of the agriglasses upon the plants biomass and relative growth rate was highlighted. The effects of agriglasses can be tuned through glass compositions that affect the solubility of the nutrients.

Fluorinated silica-modified anti-oil-fouling omniphobic F-SiO2@PES robust membrane for multiple foulants feed in membrane distillation

Direct-contact membrane distillation (DCMD) can be eminent solution for oily wastewater treatment if the membrane provided is slippery and tolerant to low surface tension complex solutions. This study describes preparation of an anti-oil-fouling omniphobic polyethersulfone membrane using fluorinated silica nanoparticles (F-SiO₂@PES) combined with perfluorodecyl triethoxysilane and polydimethylsiloxane for application against oil-In-water (o/w) emulsions. Feed solutions consist of different concentrations of oil (hexadecane), different charge surfactants (anionic sodium dodecyl benzenesulfonate, non-ionic Tween 20, and cationic hexadecyltrimethylammonium bromide, and salt (NaCl). The hierarchical re-entrant micro structured surface of the omniphobic F-SiO₂@PES membrane and functional groups are confirmed by atomic force microscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The anti-oil-fouling and anti-wetting performance of omniphobic F-SiO₂@PES membranes are investigated using contact-angle, sliding angles, DCMD tests with multiple foulants of surfactants. Omniphobic F-SiO₂@PES membrane exhibited effective anti-oil-fouling and anti-wetting performance against emulsions as no severe fouling and a conductivity rises were evident regardless of surfactant charge and the concentration of components. Flux reduction and rejection rates for the omniphobic F-SiO₂@PES membranes are in a range of 5-15% (only) and >99%, respectively, for various combinations of feed solution components.

Factors affecting gaseous emissions, maturity, and energy efficiency in composting of livestock manure digestate

This study investigated the interplay effects of key operational factors on maturity, gaseous emissions, and energy efficiency during composting of livestock manure digestate. Orthogonal experiments were conducted with three factors: digestion duration (15, 30, 45 days), corn stalk addition (15%, 25%, 35%, wet weight based), and aeration rate (0.12, 0.24, 0.48 L kg^-1 dry matter (DM) min^-1). Results showed that digestion duration was the main factor influencing the compost germination index (GI), greenhouse gases (GHGs) emission, and net energy. Digestion duration of 30 days was favored for compost GI and GHG reduction, while digestion duration of 45 days exhibited 18% higher daily net energy. Increasing corn stalk addition and aeration rates improved compost GI, but increased energy consumption. Corn stalk addition of 25% and aeration rate of 0.24 L kg^-1 DM min^-1 could ensure desirable compost maturity and save energy consumption. Thus, digestion for 30 days, 25% corn stalk addition, and aeration rates of 0.24 L kg^-1 DM min^-1 can be potentially implemented in industry for environmental and cost efficient composting of digestate.

Lightweight aggregate obtained from municipal solid waste incineration bottom ash sludge (MSWI-BAS) and its characteristics affected by single factor of sintering mechanism

To solve the disposal problem of municipal solid waste incineration bottom ash sludge (MSWI-BAS), using it as the main raw material to prepare lightweight aggregates (LWA) for resource utilization. Sintering is an important process to achieve the desired microstructure and material properties. This paper investigates the characteristics of LWA affected by single factor of sintering mechanism (sintering temperature, heating rate and soaking time). Results show that sintering temperature increased from 1130°C to 1160°C caused high-density microstructure materials gradually formed in LWA, leading to particle strength increased from 0.1 MPa to 3.64 MPa, particle density showed an overall upward trend, reaching a maximum of 916 Kg/m³ at 1160°C, and 1 h water absorption reduced from 68% to 25%. The heating rate of 15 K/min was beneficial to the formation of dense phase structure which could increase the particle strength, and the water absorption rate reached the lowest at this time, while the particle density was less affected by heating rate. When soaking time extended from 5 min to 20 min, particle strength and compressive density were gradually increased, and 1 h water absorption showed an overall downward trend, indicating that a longer soaking time was not conducive to the retention of pores. This study demonstrates that the utilization of MSWI-BAS to make high-performance LWA is feasible, along with the preferable environmental and economic benefits.Implications: MSWI-BAS were selected to produce lightweight aggregate (LWA), so that the sludge disposal problem is reduced. The effects of sintering temperature, heating rate and soaking time on the characteristics of LWA were investigated. Compact glass structures are formed at 1150°C and 1160°C which greatly improve the strength. The heating rate has little influence on the physical properties of LWA products. The particle density of LWA increases after the sintering soaking time reaches 15 minutes.

Semi-quantitative determination of ash element content for freeze-dried, defatted, sulfated and pyrolysed biomass of Scenedesmus sp

BACKGROUND

Energy demand by mankind has become one of the most important aspects of our society. A promising technology that seeks to provide part of the energy demand and to obtain high-value products is the thermochemical conversion of microalgae biomass. Inorganic species presented in microalgae biomass may act as catalysts for thermochemical reactions and are responsible for notorious ash-related issues during thermochemical decomposition.

RESULTS

In this study, the freeze-dried biomass of Scenedesmus sp. was used to evaluate the lipid extraction methodology regarding a sonication bath as pretreatment technique for cell disruption followed by vortex mixing and n-hexane as solvent. It is also presented the lipid and amino acid profiles for Scenedesmus sp. The freeze-dried biomass was pyrolysed through a TGA (thermogravimetric analysis), with heating rates of 20 °C/min, from 100 to 650 °C. The ash and sulfated ash contents were accurately determined by combustion of biomass in a muffle furnace. The element component of ashes of the freeze-dried, defatted, pyrolysed and sulfated biomasses was determined by means of scanning electron microscope (SEM) fitted with energy dispersive spectroscopy (EDS). The lipid content obtained for Scenedesmus sp. dry biomass was 16.72% (± 0.03). The content of the sulfated ash obtained was 17.81 ± 0.15%. The SEM-EDS technique identified different mineral compounds in ashes, allowing to quantify Mg, P, S, K, Ca, Fe, Co and Br, as well as oxides.

CONCLUSION

The results suggest a possible strategy to evaluate in a semi-quantitative manner the ash composition of freeze-dryed, defatted, sulfated and pyrolysed biomass of Scenedesmus sp. and its feasibility in using Scenedesmus sp. biomass in different thermochemical conversion strategies to achieve processes with positive energy ratio, representing potential use both environmental and energetically.

A new molecular weight (MW) descriptor of dissolved organic matter to represent the MW-dependent distribution of aromatic condensation: Insights from biodegradation and pyrene binding experiments

In this study, we utilized a size exclusion chromatography (SEC) system that was equipped with a fluorescence emission scanning mode to explore the heterogeneous distribution of the humification index (HIX) values within bulk dissolved organic matter (DOM). The HIX-based SEC chromatograms showed that the molecular weight (MW)-dependent distribution of aromatic condensation was heavily affected by the DOM sources and the progress of biodegradation. The HIX heterogeneity across different MW was more pronounced for terrestrial versus aquatic DOM sources. Microbial incubation of leaf litter DOM led to the initial enhancement of the HIX at a relatively low MW, followed by a gradual increase at larger MW values. The dynamic changes of the HIX can be attributed to (1) the preferential removal of non-aromatic or less-aromatic molecules by microorganisms, (2) the production of microbial metabolites, (3) microbial humification, and (4) self-assemblage of humic-like molecules. From the SEC chromatograms, the HIX-based average molecular weight (or MW_HIX) was proposed as a unifying surrogate to represent an MW that was highly associated with aromatic condensation. The MW_HIX discriminated four different DOM sources and described well the biodegradation-induced changes. The MW_HIX also presented a good positive correlation with pyrene organic carbon-normalized binding coefficients (K_oc). The prediction capability of the MW_HIX for pyrene K_oc was higher than those based on the single descriptors of bulk DOM, such as HIX and MW, which revealed its superior linkage with the DOM reactivity related to both MW and HIX.

Effects of ambient temperature and aeration frequency on emissions of ammonia and greenhouse gases from a sewage sludge aerobic composting plant

This study analyzed emissions characteristics of NH₃ and greenhouse gases (i.e. N₂O, CH₄, and CO₂) from a municipal sewage sludge aerobic composting plant. Samples were collected during different seasons in which ambient temperatures and aeration frequencies varied. Results revealed (1) the maximum gas emissions occurred during the mesophilic phase for N₂O (22%-56%) and CH₄ (65%-95%), and in the thermophilic phase for NH₃ (84%-86%) and CO₂ (65%-74%); (2) raising ambient temperatures promoted emissions of NH₃ and greenhouse gases, while improved aeration frequency increased NH₃ but decreased greenhouse gas emissions; (3) CO₂ and N₂O were found to be the key greenhouse gases emitted during aerobic composting according to assessment of the CO₂ equivalent. The results obtained from this study suggest that adjusting ambient temperature to -3 to 5 °C and aeration frequency in composting workshops can be useful approaches for the reduction of NH₃ and greenhouse gas emissions from municipal sewage sludge composting plants.

Effects of waste lime and Chinese medicinal herbal residue amendments on physical, chemical, and microbial properties during green waste composting

Traditional composting is time-consuming and often results in a low-quality product. The objective of this study was to determine the effects of waste lime (WL; at 0, 2.5, and 3.5%) and/or Chinese medicinal herbal residues (CMHRs; at 0, 10, and 20%) as amendments on the two-stage composting of green waste (GW). The combination of WL and CMHRs improved compost particle-size distribution and pH, decreased nitrogen loss, and increased cation exchange capacity (CEC), nutrient content, and microbial numbers. The combination of WL and CMHRs also accelerated organic matter humification and lignocellulose degradation and therefore increased the germination index of the final compost. Relative to the non-amended compost, the optimal amendment (2.5% WL and 20% CMHRs) increased the percentage of particles of ideal size from 23.8 to 66.9%, the pH from 6.69 to 7.17, the CEC from 52 to 169 cmol/kg, the humic acid to fulvic acid ratio from 1.32 to 2.49, the hemicellulose degradation rate from 42 to 87%, and the cellulose degradation rate from 20 to 61%. The treatment with addition of 2.5% WL and 20% CMHRs to GW required only 21 days to generate the highest quality compost product.