In-vessel,Mechanical Rotating Drum Composting Of Institutional Food Residuals

Use of composting technology as a treatment/disposal method for food residuals has been investigated by numerous researchers. This project evaluated the applicability of in-vessel, mechanical, rotating drum composting for food residuals. Three batches of food residuals (plate scrapings) were collected from a Texas prison and mixed with fine-textured soft-wood shavings at 2/1, 3/1 and 4/1 (ratios of shavings to food residual on a volumetric basis) to produce 0.4 m³ of compost blend. Temperature, oxygen, pH, bulk density and porosity were tracked throughout a fifteen-day composting trial. Volume and weight reductions were noticed for all blends. All blends reached thermophilic temperatures (> 45°C) while remaining aerobic during the trials. Initial pH was low in all blends, occasionally reaching 3.55 before returning to optimal levels (6.0 to 7.5) for composting. Temperature increases into the thermophilic range during composting corresponded to increases in compost pH. Most nutrients (P, K, Ca, Mg, S, Na and Zn) increased in concentration during the composting period, with the exception of N, which in some instances decreased over time. Composts utilizing the 3/1 ratio of bulking agent/food residual achieved thermophilic temperatures quickest and maintained temperatures longer than did other blending ratios. From this study, it appears that use of the mechanical, in-vessel, rotating drum composter may be a viable alternative for food residual disposal.     

Nitrogen Availability Seven Years After a High-Rate Food Waste Compost Application

Long-term effects of compost application are expected, but rarely measured. A 7-yr growth trial was conducted to determine nitrogen availability following a one-time compost application. Six food waste composts were produced in a pilot-scale project using two composting methods (aerated static pile and aerated, turned windrow), and three bulking agents (yard trimmings, yard trimmings + mixed paper waste, and wood waste + sawdust). For the growth trial, composts were incorporated into the top 8 to 10 cm of a sandy loam soil at application rates of approximately 155 Mg ha^?1 (about 7 yd³ 1000 ft²). Tall fescue (Festuca arundinacea Schreb. ‘A.U. Triumph’) was seeded after compost incorporation, and was harvested 40 times over a 7-yr period. Grass yield and grass N uptake for the compost treatments was greater than that produced without compost at the same fertilizer N rate. The one-time compost application increased grass N uptake by a total of 294 to 527 kg ha^?1 during the 7-yr. field experiment. The greatest grass yield response to compost application occurred during the second and third years after compost application, when annual grass N uptake was increased by 93 to 114 kg ha^?1 yr^?1. Grass yield response to the one-time compost application continued at about the same level for Years 4 through 7, increasing grass N uptake by 42 to 62 kg ha^?1 yr^?1. Soil mineralizable N tests done at 3 and 6 yr. after application also demonstrated higher N availability with compost. The increase in grass N uptake accounted for 15 to 20% of compost N applied after 7-yr. for food waste composts produced with any of the bulking agents. After 7-yr, increased soil organic matter (total soil C and N) in the compost-amended soil accounted for approximately 18% of compost-C and 33% of compost-N applied. This study confirmed the long-term value of compost amendment for supplying slow-release N for crop growth.     

Nitrogen and Phosphorus Availability in Groundfish Waste and Chitin-Sludge Cocomposts

Seafood processing generates a substantial volume of wastes. This study examined the feasibility of converting the fish waste into useful fertilizer by composting. Groundfish waste and chitin sludge generated from the production of chitin were composted with red alder or a mixture of western hemlock and Douglas-fir sawdust to produce four composts: alder with groundfish waste (AGF); hemlock/fir with groundfish waste (HGF); alder with chitin sludge (ACS); and hemlock/fir with chitin sludge (HCS). The resulting AGF had a higher total N and a lower C:N ratio than the other three composts. A large portion of the total N in the AGF, HGF, and HCS composts was in inorganic forms (NH₄⁺-N and NO₃^?-N), as opposed to only two percent in the ACS compost. Alder sawdust is more quickly decomposed, which favored N retention and limited nitrification during the composting period. It was less favorable than the hemlock/Douglas fir sawdust for composting with chitin sludge. Corn growth on soil amended with compost was dependent upon both compost type and rate. Nitrogen and P availabilities in all composts except the ACS were high and compost addition enhanced corn yields, tissue N and P concentrations, and N and P up-take. Neither the total N concentration nor the C:N ratio of the composts was an effective measure of compost N availability in the soil. Because soil inorganic N test levels correlated well with the corn biomass, tissue N and N uptake, they should be an effective measure of the overall compost effects on soil N availability and corn growth response. Phosphorus concentration, which increased linearly with increasing compost rates, was related to soil P availability from compost additions and correlated well with corn biomass, tissue P concentration and P uptake under uniform treatments of N and K fertilizers. Composting groundfish waste with alder or hemlock/Douglas-fir sawdust can produce composts with sufficient amounts of available N and P to promote plant growth and is considered to be a viable approach for recycling and utilizing groundfish waste.     

Evolution of organic matter and nitrogen during co-composting of olive mill wastewater with solid organic wastes

 Four olive mill wastewater (OMW) composts, prepared with three N-rich organic wastes and two different bulking agents, were studied in a pilot plant using the Rutgers system. Organic matter (OM) losses during composting followed a first-order kinetic equation in all the piles, the slowest being the OM mineralisation rate in the pile using maize straw (MS). The highest N losses through NH₃ volatilisation occurred in the mixtures which had a low initial C/N ratio and high pH values during the process. Such losses were reduced considerably when MS was used as the bulking agent instead of cotton waste (CW). N fixation activity increased during the bio-oxidative phase before falling during maturation. This N fixation capacity was higher in piles with a lower NH₄ ⁺-N concentration. Only the composts prepared with OMW, CW and poultry manure or sewage sludge reached water-soluble organic C (C_W) and NH₄ ⁺-N concentrations and C_W/N_org and NH₄ ⁺/NO₃ ^– ratios within the established limits which indicate a good degree of compost maturity. Increases in the cation-exchange capacity, the percentage of humic acid-like C and the polymerisation ratio revealed that the OM had been humified during composting. The germination index indicated the reduction of phytotoxicity during composting. Received: 14 June 1999     

The Influence of Bulking Material Type and Volume On In-house Composting in High-Rise,Caged Layer Facilities

In-house composting involves treating manure where it accumulates on the floor of high-rise, caged layer facilities. This process produces a partially composted material and can aid in house fly (Musca domestica L.) control by generating temperatures in the thermophilic range (≥43°C). Two trials were conducted to determine the effect of material volume and the use of previously composted material (starter) or wheat (Triticum aestivum L.) straw as bulking agents on compost temperatures and material properties. In Trial 1, starter combined with wheat straw or wheat straw alone were added to separate quadrants in a layer building, formed into windrows, and turned biweekly. Temperatures were consistently higher with the starter treatment, but both treatments followed a distinct pattern where temperatures peaked on the day of turning and declined rapidly thereafter. The starter treatment had higher initial volume (0.19 m³ m^?1 row) than straw alone (0.13 m³ m^?1 row), and maintained proportionately higher volumes throughout the trial. Volume in both treatments increased linearly with time and was correlated with peak compost temperature on the day of turning. Regression analysis indicated that a critical volume of 0.18 m³ m^?1 row was required to consistently achieve compost temperatures ≥43°C. In a second trial, starter alone was compared to wheat straw at two rates. Volumes for all treatments initially ranged from 0.20 to 0.28 m³ m^?1 row and increased linearly throughout the trial. Temperatures consistently exceeded 43°C on the day of turning. Analysis of the materials from both trials indicated that starter or straw had little effect on %moisture, %carbon, %nitrogen, or carbon:nitrogen ratio of composting materials beyond the first week after windrow establishment. These results indicate that material volume is more important than the use of starter or straw materials as bulking agents to achieve in-house composting temperatures ≥ 43°C.     

The Maturity and CH4, N2O,NH3 Emissions from Vermicomposting with Agricultural Waste

This study investigated the maturity and gaseous emissions from vermicomposing with agricultural waste. A vermicomposting treatment (inoculated Eisenia fetida) was conducted over a 50-day period, taking tomato stems as the processing object and using cow dung as the nutrient substrate. A thermophilic composting treatment without earthworm inoculation was operated as a control treatment. During the experiment, maturity indexes such as temperature, pH, C/N ratio, and germination index (GI) were determined and continuous measurements of earthworm biomass and CH₄, N₂O, and NH₃ emissions were carried out. The results showed that the temperature during vermicomposting was suitable for earthworm survival, and the earthworm biomass increased from 10.0 to 63.1 kg m^?3. Vermicomposting took less time on average to reach the compost maturity standard (GI 80%), and reached a higher GI (132%) in the compost product compared with the thermophilic composting treatment. Moreover, the decrease of the C/N ratio in vermicompost indicated stabilization of the waste. The activities of earthworms played a positive role in reducing gaseous emissions in vermicompost, resulting in less emissions of NH₃ (12.3% NH₃-N of initial nitrogen) and total greenhouse gases (8.1 kg CO₂-eq/t DM) than those from thermophilic compost (24.9% NH₃-N of initial nitrogen, 22.8 kg CO₂-eq/t DM). Therefore, it can be concluded that vermicomposting can shorten the period required to reach compost maturity, can obtain better maturity compost, and at the same time reduce gaseous emissions. As an added advantage, the earthworms after processing could have commercial uses.     

膨松剂对厨余垃圾堆肥CH4、N2O和NH3排放的影响

厨余垃圾有别于混合生活垃圾,具有高有机质含量和高含水率等特点,单独堆肥会产生大量CH4、N2O、NH3和渗滤液,为减少厨余垃圾堆肥过程污染物的排放,该文以居民小区产生的经大类粗分后的厨余垃圾为研究对象,以菌糠为膨松剂,设置15%、25%、35% 3个添加质量比（湿基）的堆肥处理,以纯厨余垃圾单独堆肥为对照处理,研究菌糠作为膨松剂对厨余垃圾堆肥过程中CH4、N2O、NH3和渗滤液排放的影响及其最佳添加比例。结果表明,堆肥过程中,添加菌糠可以完全避免厨余垃圾堆肥过程中渗滤液的产生;堆肥结束时,添加15%和25%菌糠的处理堆肥达到腐熟标准,但添加35%的菌糠使堆肥高温期缩短,不利于有机质分解;与对照处理相比,添加15%、25%和35%比例的菌糠均可以减少堆肥过程中CH4和NH3的累计排放量,且减排量与添加比例正相关,但只有添加15%菌糠的堆肥处理明显降低了N2O的排放量;添加质量比为15%和25%菌糠的堆肥处理,CH4和N2O排放总量比厨余垃圾单独堆肥分别减少45.8%、19.6%,而添加质量比为35%的菌糠使CH4和N2O排放总量为厨余垃圾单独堆肥的1.14倍（每t物料,干基）。综上,菌糠作为食用菌种植废弃物,可用作厨余垃圾堆肥膨松剂,在适宜的添加比例条件下,能够在避免堆肥过程中渗滤液产生的同时,减少CH4、N2O和NH3的排放量。研究结果可为厨余垃圾堆肥过程温室气体减排、氮素损失控制和工艺改进提供理论依据和试验基础。     

Design and Performance of a Simulated Feedstock for Composting Experiments

This paper reviews the composition and performance of simulated feedstock mixtures previously employed in composting research, and presents a new simulated feedstock. The new feedstock was prepared using readily available dry ingredients — ostrich feed pellets, office paper, finished compost and woodchips — representing the substrate, amendment, seed, and bulking agent components of a composting mixture respectively. The design criteria chosen were a) a substrate plus amendment C:N ratio of 30:1, b) an energy ratio of > 800 cal/g-H₂O, c) a water ratio of < 8 g-H₂O/g-BVS, d) a wet bulk density of < 600 kg/m³ and e) a moisture content of 60% (w/w). Resultant final proportions of the substrate:amendment:seed:bulking-agent:added-water mix were 0.071:0.098:0.009:0.267:0.555 (w/w). When composted in a controlled temperature difference (CTD), forced-aeration reactor operated with condensate return, the mixture was shown to self-heat rapidly and remain at realistic temperatures for extended periods. Thermophilic temperatures were reached within 22-33 h of start-up, following lag periods of 13-22 h, and maintained for up to 34 d. Final compost characteristics were consistent with a normal composting process. It is suggested that future variations in the simulated feedstock composition could be made, and proposed that use of this type of feedstock would facilitate future experimental work associated with composting kinetics and temperature profile modeling.     

Comparison of Cassava Distillery Residues and Straw as Bulking Agents for Full-scale Sewage Sludge Composting

To solve problems of bulking agents shortage for sewage sludge (SS) composting and of disposal of cassava distillery residues (CDR) in the alcohol industry, the effects of using CDR instead of maize straw as bulking agents were investigated at full scale in Rizhao, China. This was done by comparing CDR-added and straw-added piles. Both CDR and straw promoted sanitation achievement of SS composts. CDR was effective at increasing fermentation temperature, whereas straw was superior in maintaining the thermophilic phase. The free air space (FAS) of matrices provided by CDR or straw were sufficient (>30%) for fermentation, and showed rising trends during composting. Extensive mass reduction was also accomplished in composting even after considering the weight of added straw or CDR. Compared with straw-added piles, CDR-added piles showed less average FAS (51.42%), water removal (49.68%), and organic matter (OM) loss (21.51%), but greater volume reduction (16.34%). The time-dependence of OM loss varied between the CDR-added (which followed zero-order kinetics) and straw-added (first-order kinetics) piles. After fermentation, the composts were phytotoxin-free in both treatments. The CDR-added piles had lower EC (2,221 μS cm^?1) and C/N (13.29) than straw-added piles. A smaller germination index (73.59%) for CDR-added piles, combined with higher pH (7.33) and oxygen consumption rate (4.33 mL L^?1 min^?1), suggests that SS composting with CDR requires a longer time to reach maturity than with straw. However, CDR can be used instead of maize straw as a bulking agent for full-scale SS composting.     

Evaluation of Changes in CEC During Composting

Changes in cation exchange capacity (CEC) during composting were evaluated with respect to compost amending, and compost processing. CEC_dm (CEC on dry matter basis), CEC_om (CEC on organic matter basis), and CEC_C (CEC on carbon basis) are parameters used for describing properties of composts. In this study effective cation exchange capacity (ECEC) was determined during drum composting; sampling from the infeed (FM) and the outfeed (DC0), and during curing in experimental heaps; sampling when the compost was turned first time (DC1), second time (DC2), and third time (DC3). The ECEC_dm was 18.1 (cmol+/kg) in FM, 35.5 in DC0 and 70.5 in DC3; this rise in ECEC_dm being beneficial from compost amendment standpoint. The ECEC_om was 20.6 (cmol+/kg) in FM, 41.5 in DCO and 89.8 in DC3, whereas ECEC_C was 39.3 (cmol+/kg) in FM, 77.2 in DCO and 183.1 in DC3. When ECEC was expressed on carbon mole basis (ECEC_molC), it was c. 0.5 (cmol+/Cmol) in FM, c. 0.9 in DC0 and c. 2.2 in DC3. These changes in ECEC_om, ECEC_C and ECEC_molC are valuable from the compost quality standpoint. Because the basis of CECdm, as well as, of CEC_om and CEC_C, is affected by composting, they can not be used in determining the effects of composting on the actual number of CEC sites. The amount of ash is not affected by composting, and thus ash basis can be used for determining the effects of composting on the actual number of cation sites. It was shown in this study, that during composting of manure the actual number of effective cation exchange sites increased from DC1 to DC3 by 34 percent, whereas at the same time ECEC_dm, ECEC_om and ECEC_C increased by 99 percent, 116 percent, and 137 percent, respectively. Based on CEC data reported in this paper and in compost literature, it was concluded, that changes in the number of CEC sites due to composting is overemphasized, when unanchored CEC_dm, CEC_om or CEC_C is used.     

Maturity indices for composted dairy and pig manures

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.     

不同调理剂对猪粪好氧堆肥效果的影响

分别以木屑、药渣、菇渣、砻糠灰作为猪粪堆肥的调理剂,研究其在堆肥过程中温度、含水率、pH、EC和主要营养元素N、P、K的动态变化。结果表明,在整个堆制过程中,4个处理的堆温变化明显呈现出升温期、高温期和降温期3个阶段,其中,木屑处理堆体升温最快,且高温持续时间最长,砻糠灰处理高温持续时间最短;与初始值相比,堆肥后每个处理pH均有所上升,其中菇渣处理上升幅度最大,达0.9个单位;堆制过程中,4个处理有机质总体呈现下降的规律;堆肥后药渣处理的TN和TP含量最高;堆肥后砻糠灰处理的TK含量最高;堆肥后4个处理的pH和EC值都在腐熟堆肥的适宜范围之内,从N+P2O5+K2O总养分和保氮角度来看,应选药渣作调理剂,从提高堆肥TK含量来看,应选砻糠灰作调理剂。     

Maturity and Stability Evaluation of Composted Yard Trimmings

The objective of this research was to evaluate a variety of stability and maturity indices for yard trimmings compost produced in the Puget Sound region of western Washington State. Compost samples were collected periodically during a 133-d composting cycle at a commercial composting facility, showing that indices of compost respiration rate were sensitive indicators of compost quality. All respiration rate indices identified a period of high respiration rates during active composting (first 27 d), and a period of relatively stable respiration rates during the latter part of curing (70 to 133 d). Chemical tests of compost solids showed less promise as maturity indicators, but provided valuable information on final compost quality. Mature yard trimmings compost had a C:N of 12, an NH₄-N to NO₃-N ratio of less than 4, a cation exchange capacity (CEC) of 400 cmol per kg of compost-C, and a pH between 6.5 and Seed germination tests and sensory tests (color and odor) were of limited value in assessing compost maturity. Fully-cured compost produced with forced aeration had a Solvita CO₂ test value of 6 to 7 and a respiration rate via the alkaline trap method of 2 mg CO₂-C g compost-C^?1 d^?1. It reheated less than 2°C in an insulated Dewar flask in a 7 d incubation. Further evaluation and calibration of respiration test protocols for compost quality assurance testing programs are recommended.     

A Comparison of Different Bulking Agents for the Composting of Fish Offal

An experiment comparing the effectiveness of three different bulking agents in the composting of fish processing wastes was carried out using small-scale composters operated at ambient temperatures. Fish offal was mixed with each of peat moss, sawdust and wood shavings in a 5:1 ratio by weight. The mixed materials were left undisturbed in the composters for an initial 55 days. They were then mixed and reloaded into their respective composters for a further 95 days of composting. Temperatures were monitored throughout the experiment, while serial physical and chemical analyses of the compost materials were initiated after the mixing. Headspace-gas chromatography was also used to determine the levels of phytotoxic organic acids and phenol. All the compost piles reached thermophilic temperature levels (40–70°C). Due to insufficient pile mass, temperatures over 55°C were not sustained for a sufficient length of time to satisfy the EPA requirements for pathogen reduction. The temperature profiles suggest that ambient temperatures near the freezing point can significantly influence the temperature of compost piles with volumes of 63 liters or less. The results reaffirm the potential of composting as a viable option for utilizing fish processing wastes and the suitability of peat moss, sawdust, and wood shavings as bulking materials. The physical and chemical qualities of the 150-day old composts were comparable to other seafood compost products. Peat moss gave the best results in terms of nitrogen conservation, but is the most expensive option. Monitoring the concentrations of phytotoxic organic acids and phenol using headspace-gas chromatography proved to be a useful method for establishing compost maturity.     

Characteristics of Composts Derived from Waxed Corrugated Cardboard

The characteristics of 12 composts containing, by volume, spent mushroom substrate (SMS, 50 percent), waste waxed corrugated cardboard (WCC, 0 percent, 25 percent or 50 percent), and/or pulverized wood wastes (WW, 50 percent, 25 percent or 0 percent) were measured during two separate windrow composting periods (12-16 weeks). Supplemental N was added to some of the composts in the form of poultry manure, and/or soybean processing wastes. During the first eight to 10 weeks, composts containing 50 percent WCC tended to reach and maintain the highest temperatures, but subsequently cooled most rapidly. Microbial activity (CO₂ evolution) also was initially highest in these composts but fell by the twelfth week to levels comparable to composts containing lower levels of WCC. The paraffin wax in WCC containing composts was almost completely degraded (>95 percent). After 12 weeks of composting N (1.2-1.6 percent DW), P (0.30-0.55 percent), and K (0.9-1.2 percent) concentrations were within typical ranges and N and P were highest in composts containing 50 percent WCC. KC1 extractable NH₄-N (494 mg-N kg^?1) and NO₃+NO₂-N (281 mg-N kg^?1) were highest and lowest, respectively, in composts containing 50 percent WCC. Electrical conductivity (4.5-8.5mS/cm) and pH (7.5-8.5) were high in all composts and highest in composts with 50 percent WCC. Concentrations of phenolic compounds were highest in composts containing 50 percent WCC, manure, and soybean wastes and were positively correlated with NH₄-N. C:N ratios of all composts were within an acceptable range (18-23:1).     

Paper Mill Sludge Composting and Compost Utilization

Economically viable and environmentally acceptable methods to recycle organic wastes are needed by the pulp and paper industry. We assessed the potential for composting the Virginia Fibre Corporation's (VFC) combined primary and secondary dewatered paper mill sludge (PMS) and evaluated the suitability of the finished product as a potting soil substitute. Composting treatments were: 1) PMS with no supplemental N (control), 2) PMS + 15 kg N/Mg PMS (dry weight), and 3) PMS + 30 kg N/Mg PMS (dry weight). Composting was conducted for 129 days and treatment effects were evaluated by windrow temperature trends. A container plant growth study employing various particle size fractions and proportions of the control PMS compost and a commercial potting medium (Promix^tm) was conducted in a greenhouse to assess the capability of the compost to support growth of radish (Raphanus sativus L.), snap bean (Phaseolus vulgaris L.), marigold (Tagetes erecta L.), and green pepper (Capsicum sp.). Windrow temperatures were lower with no supplemental N than with the N additions during the initial three weeks and were higher with increasing N rate during the last month of composting, which indicated that the unamended sludge may have been N-limited for maximum biological activity. Reduced temperatures in the high N treatments during the midpoint of the composting process may have been induced by ammonia toxicity. However, cured compost chemical properties and stability were not influenced by treatment and were indicative of good quality compost. The lower amount of plant-available water and greater amounts of plant-available nutrients supplied by the compost than the commercial potting medium resulted in less dry matter produced by all plants except green pepper, whose higher nutrient needs were supplied better by the compost than the commercial potting medium alone. Therefore, the paper mill sludge compost may best be used as an organic fertilizer, soil amendment, or supplemental nutrient source for potting media, rather than as a potting medium alone.     

不同调理剂对牛粪好氧堆肥的影响

养殖业的发展造成了周边环境的严重污染。好氧堆肥技术是处理固体有机废弃物的一种有效方法。该文利用自制发酵箱进行了牛粪与不同调理剂-玉米芯、玉米秸秆和稻草的混合好氧堆肥试验。试验结果表明，当堆肥底料的初始碳氮比为27：1，初始含水率为65%时，玉米芯、玉米秸杆和稻草均可作为调理剂与牛粪进行好氧堆肥，且可达到无害化要求。而采用粒径大、多孔、疏松的玉米芯作为调理剂，有利于通风供氧，堆体升温和降温均较快，高温持续时间长，堆料腐熟快，有利于加快堆肥的进程。     

不同调理剂对牛粪好氧堆肥的影响

养殖业的发展造成了周边环境的严重污染。好氧堆肥技术是处理固体有机废弃物的一种有效方法。该文利用自制发酵箱进行了牛粪与不同调理剂一玉米芯、玉米秸秆和稻草的混合好氧堆肥试验。试验结果表明,当堆肥底料的初始碳氮比为27:1,初始含水率为65％时,玉米芯、玉米秸杆和稻草均可作为调理剂与牛粪进行好氧堆肥,且可达到无害化要求。而采用粒径大、多孔、疏松的玉米芯作为调理剂,有利于通风供氧,堆体升温和降温均较快,高温持续时间长,堆料腐熟快,有利于加快堆肥的进程。     

Composting and Evaluating a Pulp and Paper Sludge for Use as a Soil Amendment/Mulch

Composting could be used in the pulp and paper industry to treat primary sludges as an alternative to landfilling. The objective of this project was to compost and evaluate a pulp and paper sludge for use as a soil amendment/mulch. Primary sludge, tailings, wood ash (0, 5 or 10 percent by volume), and paunch (cattle stomach contents and tissue) from a slaughterhouse were composted in a 91 m windrow that was turned one to two times per week. The pile moisture content and temperature were controlled at 50 percent and 57–63°C during 14 weeks of composting. The compost was then cured for 4 weeks for a total treatment time of 18 weeks. Sludge dry mass decreased by approximately 50 percent, pH increased slightly to 8.2 to 8.5, and carbon-nitrogen ratio decreased from 270:1 to 14–67:1 after composting and curing. Electrical conductivity of all final composts was over 4 dS/m. Shoot biomass of tomato plants grown in a compost-amended medium (50 percent compost, 25 percent sand, 25 percent perlite by volume) improved with composting time but was still only 35–65 percent that of plants grown in a peat moss-amended medium (control). Shoot weight and height of poplar plants grown in soil amended with aged compost were unaffected by compost application rate (incorporated or as a mulch) at less than or equal to 180 Mg/ha. In summary, this study demonstrated that a pulp and paper sludge and wood ash mixture yielded a compost that could be used as a low quality mulch or soil amendment for poplar.