Search Results (13)

Egypt’s municipal solid waste (MSW) sector faces persistent challenges due to increasing generation rates, limited recovery, and a high organic fraction, motivating the selection of appropriate biological treatment options within Mechanical–Biological Treatment (MBT) systems. This study compares composting-based MBT and biodrying-based MBT for a case application in Alexandria, Egypt, using an integrated techno-economic and greenhouse gas (GHG) assessment. Discounted cash-flow modelling was applied using defined CAPEX and OPEX, along with revenue from recovered products. GHG accounting used documented emission factors and activity data against an unmanaged landfill baseline representative of current disposal practices. The system boundary covers waste reception and mechanical processing, biological treatment, process energy use, and residual disposal. Results show that composting achieves higher financial performance (NPV USD 2.55 million) than biodrying (NPV USD 0.99 million), while delivering a 48.5% reduction in net system GHG emissions relative to the baseline. Sensitivity analysis indicates that the comparative ranking is primarily driven by electricity prices, revenue assumptions, CAPEX, and baseline-related emissions parameters. Under the defined assumptions, composting is the preferred MBT biological pathway for the analyzed case, and interpretations are limited to the evaluated boundaries. Full article

A major factor in worldwide ecological harm is the large quantity of municipal solid waste generated because of rapid industrialization and population growth. Nowadays, there are numerous mechanical, biological, and thermal waste treatment processes that can reduce the amount of landfilled waste. A variety of analytical tests are conducted to evaluate the potential risks that landfills pose to human health and the environment. Among these, laboratory leaching tests are commonly employed to assess the release of specific waste constituents that may become hazardous to the environment. Municipal solid waste (MSW) management poses significant environmental risks due to leachate contamination in bioreactor landfills, where acidic conditions (pH ≈ 5) can mobilize heavy metals. This study evaluates the reliability of leaching tests for biodried reject MSW from CWMC Marišćina, Croatia, by comparing standard EN 12457-1 and EN 12457-2 methods (L/S = 2 and 10 L/kg) with simulations of aerobic degradation using acetic acid (10 g/L) to maintain pH = 5 over 9 days. Waste composition analysis revealed plastics (35%), paper/cardboard (25%), metals (15%), and glass (10%) as dominant fractions. Although the majority of parameters determined through standard leaching tests remain below the maximum permissible limits for non-hazardous waste, simulations under acidic conditions demonstrated substantial increases in eluate concentrations between days 6 and 9: Hg (+1500%), As (+1322%), Pb (+1330%), Ni (+786%), and Cd (+267%), with TDS rising 33%. These results highlight the underestimation of risks by conventional tests, emphasizing the need for pH-dependent methods to predict in situ leachate behavior in MBO-treated waste and support improved EU landfill regulations for enhanced environmental protection. Full article

Biodrying and composting are aerobic processes to treat and stabilize organic solid waste, but biodrying involves a shorter process time and does not require the addition of water. The resulting biodried material (BM) is mainly used as an energy source in cement production or in municipal solid waste incineration with energy recovery, but when obtained from agricultural or agroindustrial organic waste, it could also be used as a soil amendment, such as compost (CO). In this study, the phytotoxicity of BM compared to CO, both made from organic wastes (orange peel, mulch and grass), was evaluated on seed germination and growth (for 90 days) of lettuce (Lactuca sativa L.) seedlings on treatments prepared from mixtures of BM and soil, soil (100%) and a mixture of CO and soil. The germination index (GI%) was higher for BM extracts (200 g/L) than for CO extracts (68% vs. 53%, respectively). According to their dry weight, lettuce grew more on the CO mixture (16.5 g) than on the BM (5.4–7.4 g), but both materials far exceeded the soil values (0.15 g). The absence of phytotoxicity suggests that BM acts as a soil amendment, improving soil structure and providing nutrients to the soil. Therefore, biodrying is a quick and low-cost bioprocess to obtain a soil improver. Full article

Waste-to-energy technology has proven effective in reducing the mass and volume of waste, thereby minimizing contamination sources and residual fractions. However, high moisture content in waste significantly reduces the efficiency of energy recovery. Biodrying has shown great potential for moisture reduction through microbial activity, enhancing the efficiency of waste-to-energy processes. While the lack of proper real-time monitoring methods hinders the optimization of the biodrying processes. This study proposes an efficient method for monitoring the biodrying of municipal solid waste based on real-time electrical resistivity monitoring. During biodrying, resistivity was measured alongside key parameters like temperature, weight, gas emissions from the biodrying process, relative air humidity, moisture, and waste density. The results indicate a good correlation between bulk electrical resistivity (441–614 Ω·m) and temperature increases above ambient within the first 36 h (r² = 0.97–0.99). Statistical analyses also revealed the correlations of electrical resistivity with waste density (negative correlation, r² = 0.68–0.97) and gas emissions (moderate to strong, r² = 0.45–0.72) during different biodrying phases. These findings demonstrate the relationship between electrical resistivity and key biodrying parameters, which can be used for the development of biodrying and to enhance process control efficiency, thus enhancing sustainable waste management efficiency. Full article

The biodrying process is a well-established method in solid waste management for reducing the moisture content of municipal solid waste (MSW), facilitating its mechanical treatment, enhancing energy recovery efficiency, and simplifying disposal. However, challenges such as variability in drying efficiency, seasonal fluctuations, and operational inconsistencies limit its optimization and broader applicability. This study undertakes a detailed evaluation of biodrying operations using Statistical Process Control (SPC) techniques to improve process stability and identify key factors influencing efficiency. Data collected over a one-year period from a waste management facility employing Herhoff Rotteboxes^® reveal an average drying efficiency of 28%, with notable seasonal trends showing reduced efficiency during summer and fall. A regression model analyzing waste load, operational parameters, and seasonal effects accounted for 25% of the variability in drying efficiency, suggesting additional factors like waste composition and microbial activity significantly impact the process. This study highlights the value of SPC tools in monitoring process stability and demonstrates how targeted optimization strategies—such as seasonal adjustments and refined loading practices—can enhance biodrying outcomes. By addressing gaps in current practices, these findings contribute to the advancement of waste management technologies and support the development of more efficient and sustainable systems for handling municipal solid waste. Full article

The correct management of high-moisture organic waste (HMOW) is crucial to minimize its environmental impact and take advantage of its potential as a valuable resource, thus linking it to the circular economy, sustainable production and recycling. Processes such as anaerobic digestion, composting and, more recently, biodrying have been applied to support the sustainable management of HMOW. However, the latter has not yet been well characterized, so this study focuses on elucidating the behavior of microbial populations and their relationship with physical and chemical conditions during biodrying. In a greenhouse, a semi-static pile with an initial water content of 88%, composed of orange peel waste (80%), sugarcane bagasse (16.5%) and mulch (3.5%) was biodried for 50 days. Biodrying went through three stages: (1) the mesophilic stage, when different microbial populations decompose some organic matter, causing a temperature increase from 25 to 40 °C; (2) the thermophilic stage, in which the highest microbial counts were found, most of which corresponded to the highest temperatures reached and maintained between 40 and 62 °C, and, consequently, to the greatest decrease in water content (from 78 to 41%); and (3) the cooling phase, when the temperature dropped to 23–25 °C. The aeration and mainly the microbial activity were responsible for most of the water evaporation. Microbial activity in biodrying of HMOW ended on day 32, when the humidity was lower than 30% and the water activity (aw) was below 0.8. After that, moisture loss was carried out only by convection and radiation. Obtained biodried organic waste (10% water-content) could be used as an alternative fuel in many industries. Full article

The installation of food waste disposers has been prohibited in South Korea, due to conflicts with governmental policies that are focused on resource recovery from food waste and concerns about potential damage to the city’s sewer system. However, there is a growing demand for such systems in the country. This study proposes a system for the collective recovery of solid resources from food waste tailored for apartment complexes in South Korea, using an innovative solid–liquid separation technology. In the pilot experiment, 49.60% of the solids fed into the system were recovered as solid matter, confirming its practical applicability. Ultimately, a solid resource collective recovery system suitable for the high-rise apartment residence style of South Korea was developed and applied to an actual apartment complex. The final-stage solids were discharged from the system and processed through bio-drying, subsequently exhibiting a combustible material content of 67.06%, higher heating value (HHV) of 4843 kcal/kg, and lower heating value (LHV) of 3759 kcal/kg; moreover, they have the potential to be repurposed as biomass–solid refuse fuel (bio-SFR), compost, feed, and substrate for biogas production. The proposed food waste disposal system not only aligns with governmental policies, but also facilitates the recovery of high-quality resources from food waste, while providing a sustainable waste management solution. Full article

Biodrying is an essential part of the mechanical–biological treatment process that minimizes moisture content and simultaneously maximizes heating value for refuse-derived fuel (RDF) production. Although the mechanical separation process operates effectively in Thailand’s RDF production, high organic content levels and their degradation cause moisture contamination in RDF, producing wet RDF. Aeration is essential for an effective biodrying process, and can reduce RDF’s moisture content as well as increase its heating value. To maximize the biodrying effect, aeration should be optimized based on the waste conditions. This study proposes a modified aeration-supplied configuration for wet RDF biodrying. The aeration rate was modified based on the period within the biodrying operation; the first period is from the beginning until day 2.5, and the second period is from day 2.5 to day 5. The optimal aeration supply configuration was 0.5 m³/kg/day in the first period and then 0.3 m³/kg/day until the end of the process; this configuration yielded the greatest moisture content decrease of 35% and increased the low heating value of the biodried product by 11%. The final moisture content and low heating value were 24.07% and 4787 kcal/kg, respectively. Therefore, this optimal aeration-supplied configuration could be applied to meet the moisture content and low heating value requirements of the RDF production standard for Thailand’s local cement industry. Full article

Biodrying is a complex process that is very useful in the treatment of solid waste, where variables, such as temperature, thermal conductivity and the moisture content of organic matter, oxygen concentration in the pore space of the waste mass, microbial heat generation, microbial biomass, among others, are involved. Given this complexity, the development of mathematical models that help us to understand this bioprocess is fundamental. In the present work, a mathematical model, based on the finite difference method, was developed to predict the temperature profile at nine recording points, in an organic solid waste pile, during the biodrying process. The bioprocess was carried out under natural convection and solar radiation conditions, inside a greenhouse-type structure. A network of 5³ nodes, distributed in the x, y and z directions, on a rectangular prism, was developed. From this network, 27 base nodes were taken and the energy balance was developed for each node, and with this, the equation was obtained, in explicit form, to calculate the temperature. In these base equations, the microbial heat generation was considered, at between 2 and 140 W/m³; the convective coefficient was between 1 and 5 W/m² °C; and the daily records were taken inside the greenhouse for the solar radiation (0 to 450 W/m²), temperature (15 to 50 °C) and RH% (70 to 30). The modeled temperature profiles of the center (C) and the midpoints of the pile were, on average, 91% close to the experimental values, during the period from 0 to 20 days of biodrying; 70% close, during the period from day 21 to 35, the period when the modeled values were lower, due to the turning of the pile; and 94% close to the experimental values from day 36 to 50, when the modeled values were higher, also due to turning. The modeled temperature profiles of the left, right, upper and lower surfaces were, on average 92% close to the experimental profiles over the 0–35 day period, and the modeled and experimental values were practically identical from day 36 to 50 of the biodrying process. Full article

One of the methods of municipal solid waste (MSW) treatment is biodrying. The literature describes mainly the results obtained in a laboratory- and a pilot-scale reactor. The manuscript presents the results of MSW treatment in a full-scale bio-drying reactor (150 m³). The reactor is operated in one of the Polish installations specializing in mechanical-biological treatment (MBT). During the 14 day period of biodrying in the reactor, the parameters of MSW such as the moisture, temperature, loss on ignition (LOI), and net heating value (NHV) were examined. The temperature of the air in the reactor was also examined. The research also included changes in the above-mentioned parameters of MSW located in three parts of the reactor: the front, middle, and back. The test results showed that the moisture content of the waste decreased from the initial level of 55% to the level of 30%. This was accompanied by an increase in the NHV from 6.3 MJ kg⁻¹ to 9.6 MJ kg⁻¹. At the same time, the LOI decreased from 68% d.m. to 45% d.m. The LOI decrease is not favorable from the point of view of using MSW as refuse-derived fuel (RDF), as was expected in the final usage stage. The results have application value as the plant operator, having at their disposal the controlling of the reactor’s ventilation and the temperature inside the reactor, should select the speed of the moisture removal from MSW at such a level as to minimize the LOI decrease. Full article

Two pilot-scale tests were carried out to assess if biodrying could be an effective process for the treatment of light fraction produced by an hydromechanical pre-treatment in an anaerobic digestion plant. The trials were performed using two pilot-scale stainless steel cylindrical reactors of 750 L capacity. Two tests were performed: in Test 1, only the light fraction was used; in Test 2, the light fraction was mixed with a bulking agent composed of garden and pruning waste. In Test 2, the highest temperature (71 °C) in a short time (8 days) was reached. An average water content reduction of 78% in Test 1 and 61% in Test 2 was measured, leading to similar reductions of weight (47–48%) and volume (27–29%). A high biological stability was measured on the final light fraction samples collected from both the tests. Furthermore, the lower heating value obtained after the biodrying treatment complies with the quality specification of the European standard on refuse-derived fuels. Full article

This experimental research aimed to examine potential production and utilization of RDF derived from mixed municipal solid waste using bio-drying technology to be used as a substitute fuel for the traditional fuel currently used in cement plants in Jordan. The characteristics of RDF produced were identified and compared with limits and criteria set by some European countries. An economic model for RDF utilization in cement industry was created. The model proposes six different options resulting from adding RDF as a substitute fuel for the petcoke fuel currently used. A cost analysis for each option proposed was performed to estimate the economic and environmental savings of RDF utilization in cement industry. At the end of the bio-drying process, the mass of dried waste directed to the landfill was reduced by about 35%. In the case of the recovery of RDF materials from dried waste, the mass of waste to be landfilled was reduced by 69%. The bio-drying process allowed an increase in the heating value of waste (LHV) by 58% to reach 15.58 MJ/kg, as a result of the reduction of waste moisture. RDF produced had high calorific value, low water content, and satisfactory chlorine content. With regard to the concentration of the heavy metals, all of the RDF samples tested had lower concentrations than those values set by some European countries. The findings showed that adding 15% RDF as a substitute fuel, equaling 4.92 tons/h, to the fuel used in cement kilns will save 486 USD/h in petcoke costs, with 2.27 tons/h of CO₂ being emitted into the atmosphere at a net saving of 389 USD/h. Full article

Alternative fuels (refuse-derived fuels—RDF) have been a substitute for fossil fuels in cement production for many years. RDF are produced from various materials characterized by high calorific value. Due to the possibility of self-ignition in the pile of stored alternative fuel, treatments are carried out to help protect entrepreneurs against material losses and employees against loss of health or life. The objective of the research was to assess the impact of alternative fuel biodrying on the ability to self-heat this material. Three variants of materials (alternative fuel produced on the basis of mixed municipal solid waste (MSW) and on the basis of bulky waste (mainly varnished wood and textiles) and residues from selective collection waste (mainly plastics and tires) were adopted for the analysis. The novelty of the proposed solution consists in processing the analyzed materials inside the innovative ecological waste apparatus bioreactor (EWA), which results in increased process efficiency and shortening its duration. The passive thermography technique was used to assess the impact of alternative fuel biodrying on the decrease in the self-heating ability of RDF. As a result of the conducted analyses, it was clear that the biodrying process inhibited the self-heating of alternative fuel. The temperature of the stored fuel reached over 60 °C before the biodrying process. However, after the biodrying process, the maximum temperatures in each of the variants were about 30 °C, which indicates a decrease in the activity of microorganisms and the lack of self-ignition risk. The maximum temperatures obtained (>71 °C), the time to reach them (≈4 h), and the duration of the thermophilic phase (≈65 h) are much shorter than in the studies of other authors, where the duration of the thermophilic phase was over 80 h. Full article