Green Waste Compost Research Articles

A review on green waste composting, role of additives and composting methods for process acceleration.

Effective disposal of green waste has been a challenging task faced by urban bodies for a long time. Composting can be an effective method to manage green waste by recovering nutrients that can be used as organic manure. However, there are some limitations to green waste composting, such as a low degradation rate and the requirement for high manpower and space. Many researchers have studied ways to minimize the limitations of green waste composting through different approaches. These include the use of co-composting materials, inoculating agents, and process modifications such as multi-stage composting. In this review, we systematically summarized the physicochemical characteristics of green waste and green waste compost, optimum ratios of additives, and process modifications during the composting of green waste reported in various articles. This review is helpful for early-career researchers and individuals new to the field of green waste composting by providing them with key concepts and recent developments in the field. The study suggests that the sustainable selection of additives or methods for composting green waste should depend on resource availability, climatic conditions, and the characterization of the feedstock.

Characterization of organic materials in regulating soil carbon sequestration of urban greenspaces: Links to microbial necromass and community composition

Application of organic material is a win-win strategy that effectively boosts soil carbon (C) storage and promotes organic waste recycling in urban ecosystems. However, the divergent responses of C sequestration to organic materials and the underlying mechanisms remain unclear. Using molecular and litterbag methods, this study examined soil organic C (SOC) content, C sequestration efficiency of organic material (CSE-organic material), microbial necromass and community composition in urban greenspaces amended with different types of organic materials. The field experiment had seven treatments: addition of green waste (GreenWaste), green waste compost (GreenWasteCompost), biogas residue (BiogasResidue), biogas residue compost (BiogasResidueCompost), peat (PEAT), biochar (BioChar), and no organic material (Control). Organic materials after 16 months application increased SOC content by 34.1–87.0% compared with the Control and presented CSE-organic material in the order: BioChar > GreenWasteCompost > PEAT > BiogasResidueCompost > GreenWaste > BiogasResidue. Aromaticity index was positively correlated with CSE-organic material, indicating that aromatic C addition had a strong capacity to enhance C sequestration. Microbial necromass increased from 2.7 g C kg−1 in the Control to 3.9–5.0 g C kg−1 under organic materials addition. Bacterial necromass was enriched in the BiogasResidue and BiogasResidueCompost treatments, primarily because of sufficient substrate that facilitated the proliferation and activity of copiotrophic Firmicutes, whereas fungal necromass was 8.8–19.1% higher in the GreenWaste, GreenWasteCompost, and PEAT treatments than that in the BiogasResidue and BiogasResidueCompost treatments, accompanying by an increasing abundance of Ascomycota. However, the contribution of microbial necromass to the increased SOC was negatively correlated with CSE-organic material, suggesting that the input of recalcitrant C weakened the role of microbial necromass in C retention. Overall, this study reveals that the efficiency of organic materials application in promoting soil C accumulation depends largely on recalcitrant C rather than microbial necromass, which highlights the important role of organic waste acting as a C source in achieving urban sustainable development.

Short‐term effects of food waste composts on physicochemical soil quality and horticultural crop production

AbstractAimComposts made from food waste will soon become more widespread on the market thanks to the upcoming enforcement of the legal obligation to sort biowaste. Our experiment aims at improving knowledge on the short‐term effects of these composts on soils’ physicochemical properties and vegetable crops.MethodsThree composts with contrasting characteristics were tested: a 100% v/v green waste compost (C1), and two composts composed of 50% v/v food waste and 50% v/v green waste, one prepared directly on the soil (C2) and the other from a competing producer who have the French NFU 44‐051 (AFNOR NF U 44‐051, 2006) certification for an organic amendment (C3). They were applied at a rate of 100 t ha−1 (dry matter) on two cropped soils with contrasting textures. Soil‐and‐compost mixes and compost‐free soil were planted with lettuce, radish, and potato.ResultsSeventy‐four days after planting, composts improved some soil physicochemical properties. The compost‐amended soils had better saturated hydraulic conductivity (Ks, 1 10−3–2.5 10−3 cm s−1) than the compost‐free soil (0.5 10−3 cm s−1), and water‐stable aggregates were higher than the initial value in C3 soil, equal to it in C2 soil, and lower in C1 soil. pH, total nitrogen, and organic carbon increased in all compost‐amended soils. Food waste compost stimulated crop production. The yields (dry matter) of all three crops were two to three times higher in the two soils amended with food waste compost compared to unamended soil, whereas they decreased almost two times in the soil amended with green waste compost due to nitrogen immobilization. Trace metals (particularly Pb and Cd) added by the composts, although present in edible parts of the plants, did not exceed the European rules for trace metals.ConclusionThus, food waste composts have positive effects on soils and vegetable crops, and the higher their organic matter content, the higher these positive effects.

Organic Fertilization Improves Soil Multifunctionality in Sugarcane Agroecosystems

Soil multifunctionality is closely tied to soil health, yet a comprehensive understanding of this link in agricultural soils is lacking. The aim of this study was to understand how long-term fertilization practices affect the provision of multiple services by comparing the multifunctionality of soils. The three objectives were to (i) determine whether the effect of fertilization is consistent across soil types, (ii) describe the effect of the different fertilizers on soil multifunctionality, and (iii) identify soil chemical properties that can be easily used proxies of soil multifunctionality. The descriptors belong to three functioning indexes associated with nutrient availability, carbon transformation, and soil structure maintenance. This study is the first to investigate the effect of a variety of organic fertilizers on the health of three soil types by combining physical, chemical, and biological indicators in sugarcane agroecosystems. An increase in soil multifunctionality was obtained, with no effect on yield. The effect of fertilizers was consistent across soil types. Filter mud and green waste compost significantly increased the multifunctionality and functioning indexes compared to mineral fertilizer. Modifications in soil properties did not fully explain the observed variations. Our results confirm the high potential of organic fertilization to improve multifunctionality and provide ecosystem services.

Manufactured soil: A new use for bauxite residue

Bauxite processing residue produced at an Alumina refinery was used to produce manufactured soil. The residue was first acidified and then leached to remove excess salts. Green waste compost was added at rates of 5 and 10 % w/w, with or without the addition of 20 % w/w dune sand. The products were dried, crushed and sieved and the chemical, physical and microbial properties of the materials characterized. Products had an electrical conductivity and pH of 1.0–1.1 dS m−1 and 8.0–8.1 respectively in 1:5 soil:water extracts and corresponding values in saturation paste extracts were 5.4–5.7 dS m−1 and 7.4–7.5. The effective cation exchange capacity was 202–351 mmolc kg−1, exchangeable Na percentage was 41–46 %, Colwell-extractable P was 108–119 mg kg−1 and the Toxicity Characteristic Leaching Procedure showed that extractable metal concentrations were an order of magnitude below regulatory limits so the material can be considered as non-hazardous. Diethylenetriaminepentaacetic acid-extractable Cu, Zn and Mn were below reported critical levels. Addition of compost lowered concentrations of extractable Cr, As and V and drying the material further reduced extractable levels. When the material was dried it shrunk and solidified and the aggregates produced had a low macroporosity and high microporosity and water holding capacity compared with dune sand. Aggregates were very stable as measured by wet sieving. Compost addition increased organic C content, and the size (microbial biomass C) and activity (basal respiration and the activity of enzymes involved in C, N, S and P mineralization) of the soil microbial community. It was concluded that the materials produced had soil-like chemical, physical and microbial properties and could potentially be used as a soil substitute.

Effects of Compost Application of Green Waste on Soil Properties: A Meta-Analysis

Objective: With the accelerating urbanization process, the garden area is gradually expanding, and the production of green waste is also increasing. Composting green waste can not only reduce environmental pollution caused by incineration and landfill and improve the utilization efficiency of resources but also improve the soil and increase soil productivity. The study aims to investigate the comprehensive impact of green waste compost (GWC) application on soil nutrient conditions. Through comprehensive data analysis, the impact of compost application of green waste on soil properties was revealed as a reference for compost application and fertilizer reduction. Methods: Based on meta-analysis, we quantitatively investigated the response of soil properties to the application of green waste, collected published experimental data, and integrated 25 domestic and international literature to analyze the effects of different soil properties on soil nutrients. Literature was used to analyze the impact of different application rates of GWC on the physicochemical properties of soils with varying pH levels. The results were compared to control conditions with no GWC application. Results: The application of significantly improved soil quality by reducing soil bulk density and increasing the levels of soil organic matter, organic carbon, total nitrogen, available phosphorus, available potassium, and dehydrogenase activity. The increases in available potassium and soil organic carbon were consistently significant across all subgroups. However, the effects on available phosphorus and organic matter varied in significance depending on initial soil pH. Soil bulk density was influenced by the GWC content, while dehydrogenase activity showed significant effects only when initial soil pH was ≥8. Total nitrogen levels were significantly impacted by GWC application in soil with an initial pH of <8 and at GWC contents of ≥50%. Conclusion: The application of green waste compost demonstrates a positive effect on soil improvement. This study provides a comprehensive database that supports the use of GWC in enhancing soil quality and reducing the need for chemical fertilizers.

Carbon conversion and microbial driving factors in the humification of green waste composts

Carbon conversion and microbial driving factors in the humification of green waste composts

Composted biochar versus compost with biochar: effects on soil properties and plant growth

Biochar is widely recognized as an amendment that enhances soil properties and sequesters carbon, particularly in degraded soils. However, biochar applied solely to soil may also hinder plant development due to toxic by-products generated during pyrolysis or nutrient retention. To mitigate these adverse effects, it has been suggested to either mix biochar with compost or to process it by composting with fresh organic materials. To date, there is a lack of comparative studies evaluating the performance of these two approaches. In this study, three types of biochar, differing in their initial feedstocks (beech wood, hornbeam/beech/oak mixture, and digestate/cereal straw mixture), were investigated. These biochars were applied solely, mixed with green waste compost, or processed as composted biochar in two soils of different fertility (a Luvisol and a gleyic Fluvisol). A pot experiment was conducted under controlled conditions where lettuce was grown for three months. After harvesting, plant biomass, and soil microbial and physicochemical properties were measured. Composted biochar and compost additives maintained a neutral soil pH, contrary to biochar applied solely or mixed with compost. The dissolved organic carbon and total nitrogen were higher in composted biochar treatments, leading to a higher proportion of humified material with a high degree of condensed aromatic groups compared to other treatments. Microbial activities were higher in the composted biochar treatments compared to those in the compost with biochar, and more specifically in the less fertile Luvisol. Finally, composted biochar increased plant growth by almost six times compared to the control without amendments, whereas the mix of biochar and compost increased it by only three times. Solely applied biochars did not affect lettuce growth. This study demonstrates that biochar composting is more beneficial than mixing biochar with compost in terms of improving soil fertility and mitigating the negative effects associated with pure biochar application.Graphical

Impacts of Compost Amendment Type and Application Frequency on a Fire-Impacted Grassland Ecosystem

Composting organic matter can lower the global warming potential of food and agricultural waste and provide a nutrient-rich soil amendment. Compost applications generally increase net primary production (NPP) and soil water-holding capacity and may stimulate soil carbon (C) sequestration. Questions remain regarding the effects of compost nitrogen (N) concentrations and application rates on soil C and greenhouse gas dynamics. In this study, we explored the effects of compost with different initial N quality (food waste versus green waste compost) on soil greenhouse gas fluxes, aboveground biomass, and soil C and N pools in a fire-impacted annual grassland ecosystem. Composts were applied annually once, twice, or three times prior to the onset of the winter rainy season. A low-intensity fire event after the first growing season also allowed us to explore how compost-amended grasslands respond to burning events, which are expected to increase with climate change. After four growing seasons, all compost treatments significantly increased soil C pools from 9.5 ± 0.9 to 30.2 ± 0.7 Mg C ha−1 (0–40 cm) and 19.5 ± 0.9 to 40.1 ± 0.7 Mg C ha−1 (0–40 cm) relative to burned and unburned controls, respectively. Gains exceeded the compost-C applied, representing newly fixed C. The higher N food waste compost treatments yielded more cumulative soil C (5.2–10.9 Mg C ha−1) and aboveground biomass (0.19–0.66 Mg C ha−1) than the lower N green waste compost treatments, suggesting greater N inputs further increased soil stocks. The three-time green waste application increased soil C and N stocks relative to a single application of either compost. There was minimal impact on net ecosystem greenhouse gas emissions. Aboveground biomass accumulation was higher in all compost treatments relative to controls, likely due to increased water-holding capacity and N availability. Results show that higher N compost resulted in larger C gains with little offset from greenhouse gas emissions and that compost amendments may help mediate effects of low-intensity fire by increasing fertility and water-holding capacity.

Effects of woodchip biochar on temperature sensitivity of greenhouse gas emissions in amended soils within a mountain vineyard

The utilization of biochar as a soil amendment holds promise for long-term carbon sequestration due to its elevated carbon content and persistent chemical structure. This characteristic has positioned biochar as a proposed nature-based solution for climate change mitigation. Nevertheless, the impact of biochar on soil greenhouse gas (GHG) emissions remains a subject of ongoing debate. In the present investigation, we evaluated the influence of conifer wood biochar on the fluxes of three GHGs, namely carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), in a vineyard soil subjected to biochar-alone treatments (at rates of 25 and 50 t ha−1) and in combination with green waste compost (at a rate of 45 t ha−1). The experimental field was situated in northern Italy and was organized in a randomized block design. Soil GHG fluxes were monitored for two and a half years. Monthly flux measurements were conducted using a high-resolution multi-gas analyzer for 24 hours. Fluxes were, therefore, correlated with soil temperature to assess the influence of treatments on the sensitivity of GHG emissions to this pivotal environmental parameter. The findings demonstrated diminished temperature sensitivity in the initial experimental year across all GHG fluxes in soils amended with biochar and biochar-compost combination, in contrast to treatments lacking biochar (i.e., control and compost-alone treatments). Notably, the attenuation was most pronounced for N2O emissions, suggesting a potential role of biochar in mitigating the release of this gas. However, this effect did not persist in the second and third years of the experiment. Overall, biochar significantly contributed to a reduction in N2O fluxes and an increase in CO2 fluxes, but the effect was limited and temporary. Furthermore, biochar had no impact on CH4 fluxes. The discerned fluctuation in the impact of biochar over time can be attributed to the processes of biochar aging and/or the interannual variability in soil moisture.

Visible intruders: Tracing (micro-) plastic in organic fertilizers

Agricultural soils have been identified as potential reservoirs for plastic pollution, with adverse effects on soil properties. Primary sources of plastic input in agricultural landscapes are associated with the application of sewage sludge or compost. Understanding the sources and anticipated plastic content is crucial in mitigating plastic pollution in agricultural fields. This study presents one of the first investigations into the plastic content and other impurities, e.g. glass, of seven organic fertilizers (biowaste compost, digested pig slurry, sewage sludge compost, dry chicken manure, green waste compost, sewage sludge, and a mixed digestate comprising pig slurry, chicken manure, and 74 % renewable raw materials). Potentially visible foreign substances were assessed on the surface of each fertilizer pile. No impurities could be detected in digested pig slurry, chicken manure, and mixed digestate. For the remaining fertilizers, visible potential foreign substances were collected, cleaned, visually described, weighed, photographed, size measured, and chemically characterized using ATR-FTIR. The quantification revealed that plastic particles are the most abundant and are contained in all other fertilizers, in contrast to glass and metal. An increasing trend in plastic particle number per m2: green waste < biowaste < sewage sludge compost < sewage sludge, which is about 4 times greater in sewage sludge than in green waste compost, could be observed. However, sewage sludge compost has the largest plastic mass and surface area per square meter. This illustrates that sewage sludge compost application can be a significant entry pathway for visual plastics into agricultural soils.

Feasibility of composted green waste amended by vermiculite and earthworm casts as the growth media for three common ornamental plants.

This study demonstrated the effects of adding specific proportions of vermiculite (VMT: 0%, 10%, and 20%) and earthworm casts (EWCs: 0%, 10%, and 20%) on the physico-chemical properties of composted green waste (CGW), and the impacts of amended CGW as growth media on the growth of three common ornamental plants (Dahlia pinnata Cav. [dahlia], Centaurea cyanus L. [cornflower], and Consolida ajacis[L.] Schur [delphinium]). Compared with Treatment T1 (CK), the addition of 10% VMT and 20% EWCs greatly (p < 0.05) increased the total porosity, aeration porosity, water-holding porosity, total nitrogen, available phosphorus, available potassium, and organic matter of CGW by 9%, 35%, 4%, 18%, 27%, 13%, and 33%, respectively. In addition, this pattern increased (p < 0.05) the total fresh biomass, total chlorophyll content, and root length of dahlias by 9%, 19%, and 27%, respectively; those of cornflowers by 17%, 30%, and 29%, respectively (p < 0.05); and those of delphiniums by 23%, 14%, and 63%, respectively. Therefore, the amended CGW supplemented with 10% VMT and 20% EWCs was an ideal growth medium for the three plants.

Inorganic phosphorous availability and mobility in a manufactured soil

Manufactured soils, created by combining various organic and inorganic waste materials and byproducts, may be tailored to specific applications, providing an alternative to the extraction of natural soils. It is important for them to be capable of supporting plant growth without the need for significant management or fertiliser applications, the over-application of which can have adverse environmental effects.We examined the dynamics of phosphorus (P) transformations within a manufactured soil and the implications for nutrient cycling. A freshly prepared manufactured soil (32.5 % composted green waste, 32.5 % composted bark, 25 % horticultural grit, and 10 % lignite clay) was studied over one year in temperature and moisture controlled mesocosms. Leachate was collected to achieve high-resolution monitoring of leached phosphate concentrations.Initially, leached dissolved inorganic phosphorus (DIP) concentrations were low (0.02 ± 0.01 mg P L−1), before increasing by 160 μg P L−1 d−1 over the first 42 days to 5.57 ± 1.23 mg P L−1. After reaching a maximum concentration, DIP concentrations remained relatively consistent, varying by only 1.67 mg P L−1 until day 270. The increase in leached DIP was likely driven by soil organic matter mineralisation and the cleavage of carbon‑phosphorus bonds by the soil microbes to satisfy carbon demand with mineralogical influences, such as a decrease in apatite content, also contributing. Sorption and desorption from soil particles were the processes behind the P loss from the soil, which was followed by slow diffusion and eventual loss via leaching. The fertiliser application on phosphate dynamics resulted in increased DIP leaching.P concentrations observed in the manufactured soil were within the range considered sufficient to support plant growth. However, the mean leached phosphorus concentrations were higher than reported eutrophication thresholds suggesting that these soils may pose a risk to surface waters in their current form.

Biodegradable Waste Management in Georgia: Problems of the Composting System Introduction

Biodegradable waste management and, in particular, the introduction and implementation of composting systems are among the major problems for Georgia. An increase in the volume of municipal waste has been recorded in the country; therefore, the volume of generated biodegradable waste is also increasing. In accordance with the National Waste Management Strategy 2016-2030 of Georgia, the municipal waste generated in 2021 amounted to 1,104,952 tons. It is worth noting that the largest part of municipal waste is organic waste - 54.7%, while plastic waste is 13.8%, paper and cardboard - 10.6%, textiles - 4.1%, and other wastes. According to various studies, by 2030, waste generation is expected to increase from 0.6% to 1.2% annually, which should be the cause of significant challenges for national and local authorities, especially local municipalities, whose duties include municipal waste collection and transportation as well as the implementation of separate waste collection systems. Biodegradable waste management, including various composting systems, is of particular importance.The study shows that composting, as one of the best approaches for recycling biodegradable waste, is still not properly developed in Georgia. It is possible to name only a few successful experiences. Noteworthy among them is the Kutaisi Composting Center, which was established within the framework of the EU JOP “Black Sea Basin” in Kutaisi, Georgia. The Composting Center is designed for windrow composting of green waste (tree branches, leaves, grass). Its productivity is 2000 tons of compost annually. This Composting Center is one of the first in Georgia. It can bring very tangible benefits. In particular, the amount of municipal waste going to landfill sites was reduced by approximately 10%; the expenditures of the municipalities connected to the maintenance of green facilities (received compost is used) and so on have been reduced.Among the biodegradable waste composting approaches, it is recommended to use systems such as:Centralized composting,Community composting,Home (individual) composting.A centralized composting method can be used in municipalities where a large amount of biodegradable waste is generated. It is especially favorable in regions where the agricultural sector is developed and large amounts of green waste are generated. The Kutaisi Composting Center is a good example of the centralized composting system. As experience shows, such large-scale composting is particularly effective for green waste composting.It is promising for Georgia to introduce community composting approaches that offer an optimal scheme for communities to get the maximum benefits of their potential.Composting is an approach used in the field of biodegradable waste management that has the greatest potential in Georgia and can make a significant contribution to both economic development and the protection of the social and natural environment.

Effect of Coal Fly Ash and Green Waste Compost on Salt Ions Leaching in Coastal Saline Soils

Effect of Coal Fly Ash and Green Waste Compost on Salt Ions Leaching in Coastal Saline Soils

Effects of food waste and green waste composts on yield and nitrogen‐use efficiency in irrigated tomato crops

AbstractComposts are increasingly used to enhance soil health and agricultural sustainability, but their impacts on nitrogen (N) availability are unclear. In a 3‐year field experiment with subsurface drip‐irrigated tomatoes (Solanum lycopersicum), we investigated the effects of food waste and green waste co‐compost (FW) and green waste compost (GW) on yield, nitrogen‐use efficiency (NUE), nitrate leaching potential, and fertilizer N retention. Various combinations of compost rates (0, 9, or 18 t ha−1) and fertilizer N levels (0%, 70%, 85%, and 100% of the recommended rate) were examined, and 15N‐labeled fertilizer was used. In Years 2 and 3, FW and GW either maintained or increased crop yield compared to no compost when 0% or 70% N was applied; however, lower NUE was observed in the compost treatments compared to no compost when 70% or 85% N was supplied. Postharvest, FW showed greater fertilizer N retention in topsoil than GW and controls, while no difference in nitrate leaching potential was found among treatments, except for Year 2 during which FW exhibited the lowest potential. These results suggest that compost can immobilize fertilizer N, reducing its uptake by crops but enhancing soil retention, potentially acting as an N source or a primer of soil N mineralization. Future research is needed to assess compost's impact on N gaseous emissions and distinguish its dual roles as an N source and a soil N mineralization primer. This is essential for developing nutrient management guidelines to minimize N losses.

Composted Green Waste as a Peat Substitute in Growing Media for Vinca (Catharanthus roseus (L.) G. Don) and Zinnia (Zinnia elegans Jacq.)

The purpose of this work was to explore the feasibility of replacing all or part of peat with composted green waste (CGW) for vinca (Catharanthus roseus (L.) G. Don) and zinnia (Zinnia elegans Jacq.) cultivation. Seven different growing media were prepared as follows (volume/volume): T1, 100% CGW; T2, 80% CGW + 20% peat; T3, 60% CGW + 40% peat; T4, 50% CGW + 50% peat; T5, 40% CGW + 60% peat; T6, 20% CGW + 80% peat; and T7, 100% peat. In the course of the experiment, the physicochemical properties of the seven media were analyzed, and the growth of vinca and zinnia was determined. Studies showed that replacing peat completely or partially with CGW could significantly enhance the nutrient content, bulk density, water-holding capacity, total porosity, aeration porosity, water-holding porosity, organic matter, pH, and electrical conductivity of growing media. In comparison with what observed with T7 (control), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), plant height (HP), root length (RL), flower number (FN), total chlorophyll, and the content of chlorophyll a, chlorophyll b, and carotenoids in the leaves of vinca cultivated under T5 conditions increased by 36%, 34%, 84%, 27%, 34%, 25%, 157%, 62%, 60%, and 33%, respectively; SFW, SDW, RFW, RDW, HP, RL, FN, total chlorophylls, and the content of chlorophyll a, chlorophyll b, and carotenoids in the leaves of zinnia increased by 341%, 296%, 365%, 302%, 206%, 93%, 180%, 56%, 49%, 67%, 110%, respectively.

Substitution of mineral N fertilizers with organic wastes in two long‐term field experiments: Dynamics and drivers of crop yields

AbstractOrganic wastes (OW) are rich in nutrients, and their recycling into agriculture can substitute chemical fertilizers. The level of substitution (partial with mineral fertilizer or exclusive with only OW), along with the method, amount, and timing of OW application, as well as the crop type, can impact crop productivity. The temporal dynamics of crop productivity after repeated applications of OW remain uncertain. Thus, two French long‐term field experiments (QualiAgro and PROspective, started in 1998 and 2000, respectively) were used to evaluate the effect of repeated OW applications on crop yield dynamics and investigate the potential driving factors affecting crop yields. Six different OW were applied: urban sewage sludge (SLU), green waste and SLU compost (GWS), biowaste compost (BIO), municipal solid waste compost (MSW), farmyard manure (FYM), and composted FYM (FYMC). The OW were applied every 2 years in QualiAgro (~4 t C ha−1) and PROspective (~1.7 t C ha−1). QualiAgro was studied under high and low mineral N conditions, while PROspective was examined with and without mineral N fertilization. The results indicated that at the QualiAgro site, a combination of OW and high mineral N treatments resulted in higher maize and wheat yields compared to the mineral N control, while the combination of OW and low mineral N reached the same maize and wheat yield as the mineral N control after 3 and 6 applications of OW, respectively. At the PROspective site, partially substituting mineral fertilizer with OW maintained maize yields but decreased wheat yields, while full substitution led to a decrease in both maize and wheat yields compared to the mineral N control. Results from the gradient boosting model (GBM) showed that soil total N rather than mineral N input was the primary driver of the relative maize yield, while mineral N fertilizer input was more critical for wheat during the second year. We conclude that the joined use of OW and mineral fertilizers is superior to using OW or mineral fertilizer alone for maintaining high yields and soil fertility. We further suggest that OW full substitution of mineral fertilizer may need to apply OW more frequently to meet the crop demands, and/or to use OW with higher N availability like digestates.

Deodorisation of Ventilated Air from a Fat-Processing Plant Using Different Types of Biofilter Fillings and Membranes

The aim of the research is to assess changes in odour concentration in the ventilated air of a production hall, using different types of biofilter fillings and different types of membranes. Deodorisation was carried out using a mobile combined biofilter at a plant producing lard and liquid oils. Ventilated air from the hall contained organic and inorganic pollutants. Two types of fillings were used for technological tests: stumpwood chips mixed with pine bark and a mix of stumpwood chips with pine bark and green waste compost. Two types of membranes were also used, differing in thickness, permeability, and water resistance. The subjects of the research were the air supplied to the filter, lifted directly from the bed, and the air above the membranes. The deodorisation efficiency—the percentage reduction in the odour concentration value as a result of air flow through the bed and membranes—was calculated. The filtration methods used allowed the selection of the most advantageous technological variant from the point of view of deodorisation effectiveness: a mix of stumpwood chips with pine bark and the Pro Eko Tex UV membrane. It has a total odour reduction efficiency of 99.3–99.9% and has been added to full-scale implementation works.

Green Waste Compost Impacts Microbial Functions Related to Carbohydrate Use and Active Dispersal in Plant Pathogen-Infested Soil

The effects of compost on physical and chemical characteristics of soil are well-studied but impacts on soil microbiomes are poorly understood. This research tested effects of green waste compost on bacterial communities in soil infested with the plant pathogen Fusarium oxysporum. Compost was added to pathogen-infested soil and maintained in mesocosms in a greenhouse experiment and replicated growth chamber experiments. Bacteria and F. oxysporum abundance were quantified using quantitative PCR. Taxonomic and functional characteristics of bacterial communities were measured using shotgun metagenome sequencing. Compost significantly increased bacterial abundance 8 weeks after amendment in one experiment. Compost increased concentrations of chemical characteristics of soil, including phosphorus, potassium, organic matter, and pH. In all experiments, compost significantly reduced abundance of F. oxysporum and altered the taxonomic composition of soil bacterial communities. Sixteen bacterial genera were significantly increased from compost in every experiment, potentially playing a role in pathogen suppression. In all experiments, there was a consistent negative effect of compost on functions related to carbohydrate use and a positive effect on bacteria with flagella. Results from this work demonstrate that compost can reduce the abundance of soilborne plant pathogens and raise questions about the role of microbes in plant pathogen suppression.