MSW Compost Reduces Nitrogen Volatilization During Dairy Manure Composting

Manures lose N through volatilization almost immediately after deposit. Attempts to control losses include the addition of a C source to stimulate nitrogen immobilization. Composting is a treatment process that recommends the addition of carbonaceous materials to achieve a C:N ratio of 30:1 to stimulate degradation and immobilize nitrogen. Dairies near cities may be able to reduce N loss from manures by composting with urban carbonaceous residues such as municipal solid waste (MSW) or MSW compost that, by themselves, have little agronomic value. Studies were conducted using a self-heating laboratory composter where dairy solids were mixed with MSW compost to determine the reduction of N loss during composting. One-to-one mixtures (v/v) of dairy manure solids and MSW compost were composted and NH₃ volatilization, CO₂ evolution and temperatures were compared to composting of manure alone. Addition of MSW compost resulted in increased CO₂ evolution and reduced N loss. Nitrogen loss from composting dairy manure alone was four to ten times greater than that from composting dairy manure mixed with MSW compost. Adjustment of the C:N ratio to 25 by adding MSW compost to manure appeared to be the major factor in reducing N losses.     

Composting Short Paper Fiber with Broiler Litter and Additives: Part I: Effects of Initial pH and Carbon/Nitrogen Ratio On Ammonia Emission

Short paper fiber (SPF), a by-product of the paper mill industry, was cocomposted with broiler litter (BL) to determine decomposition rate and NH₃-N loss as functions of C/N ratio and pH of the compost mixes. The SPF generally had a high C/N ratio >200 while the BL, consisting of bedding material (sawdust) and poultry manure, had a low C/N ratio of 10–12. A total of seven series (27 tests) of pilot-scale studies were conducted using two different SPFs mixed with BL. Additives used for pH control were alum (aluminum sulfate), HiClay® Alumina and sulfuric acid. Mixing ratios [SPF/(SPF+BL), kg/kg(dry basis)] used were 0.8 to 0.4. Test conditions were C/N of 17 to 49, pH of 6.6 to 8.3, initial temperatures of ?1 to 22°C, composting temperature of 60°C, water content of 50-55% w.b. and remixing two times per week. Composting temperature was controlled using forced ventilation with a high/low fan setting. Composting trials lasted two weeks. Ammonia loss, O₂, CO₂, compost temperatures and dry solids loss were measured. Evaluations of ammonia emissions versus initial C/N and pH showed: (1) NH₃-N loss decreased as initial C/N increased, even above C/N = 38; (2) NH3-N loss decreased rapidly below pH = 7 and increased rapidly for initial pH above 8. Addition of alum and/or sulfuric acid was found to decrease NH₃- N loss while HiClay® Alumina had little or no effect. Results on dry solids loss are not presented in this article.     

Operational Parameters for Composting Night Soil in Korea

Recently composting of organic wastes started to gain popularity in Korea. The purpose of this study was to investigate the effect of operational parameters on night soil composting. Operational parameters investigated included compost recycle ratio and temperature control. Lab-scale composting reactors were used in this study. At the recycle ratio of 10 percent, reduction of both volatile solids and moisture content was greater than that at the recycle ratio of 0 percent and 30 percent. This result means that composting reaction was the most active at 10 percent recycle ratio. Temperature control played a important role in the night soil composting process. The greatest decrease in volatile solids was observed when the temperature of composting process was set below 60°C. Also, the amount of CO₂ evolved was the greatest when the maximum temperature was set below 60°C. Kinetic study indicated that first order kinetics described volatile solids reduction very well.     

Stability Evaluation of Mixed Food Waste Composts

As interest in food waste composting grows, so does the need for proven composting methods. Stability testing has been proposed as a compost quality assurance tool. We conducted this study to: (i) to evaluate the efficacy of simple outdoor composting methods in producing a compost with a low, stable decomposition rate, and (ii) to determine the reliability of simple, 4-h compost stability evaluation methods. Composting was conducted outdoors in winter and spring in Eugene, Oregon without moisture addition. Mixed food waste was combined with screened dairy solids and ground yard trimmings. Sawdust was used to cover windrows for the first 27 d of composting. Compost windrow temperatures remained above 55°C for 30+ d. Carbon dioxide evolved with several 4-h test methods was strongly correlated (r² > 0.7) with CO₂ evolved using a 48-h test. A limited-turn windrow (LTW) composting system produced compost with slightly greater stability than a passively aerated windrow (PAW) composting system. Food waste compost samples had a low CO₂ evolution rate after 71 to 99 d using either composting system. Compost CO₂ evolution rate at 25°C decreased with composting time, reaching approximately 1 to 4 mg CO₂-C g compost C^?1 d^?1 for the PAW method and 0.5 to 2 mg CO₂-C g compost C^?1 d^?1 for the LTW method. Putrescible organic matter in food waste was effectively decomposed in outdoor windrows using composting methods that did not employ forced aeration, self-propelled windrow turners, or manufactured composting vessels. Several 4-h stability tests showed promise for implementation as quality assurance tools.     

垃圾堆肥对难溶性磷转化及土壤磷素吸附特性影响

在城市生活垃圾进行工厂化堆肥过程中,加入难溶性磷矿粉,探讨堆肥对难溶性磷的转化能力及堆肥产品培肥后对土壤磷素吸附特性的影响。结果表明,加入磷矿粉可使堆肥中活性有机磷、中等活性有机磷、中稳性有机磷、高稳性有机磷及速效磷含量均有不同程度的提高,与对照相比分别增加212.69%、80.36%、61.21%、62.74%、157.89%。通过电镜观察表明,堆肥后磷矿粉典型的矿物特征消失,表面呈蜂窝状。将堆肥后的产品进行培肥试验表明,富磷垃圾肥处理可明显改善土壤磷素的吸附特性,与施化肥相比,最大吸附量(Q_m)下降8.76%,最大缓冲容量(Q_m·K)下降13.58%,而磷素的吸附饱和度(DPS)、零净吸附浓度磷(EPC₀)则呈不同程度的增加,幅度依次为98.52%、7.13%。试验结果显示,通过堆肥生产富磷垃圾肥可为解决中国磷素资源缺乏、化学磷肥利用率低等问题提供一条生物学途径。     

Combined effects of nitrogen deposition and biochar application on emissions of N2O,CO2 and NH3 from agricultural and forest soils

Abstract

Both nitrogen (N) deposition and biochar can affect the emissions of nitrous oxide (N₂O), carbon dioxide (CO₂) and ammonia (NH₃) from different soils. Here, we have established a simulated wet N deposition experiment to investigate the effects of N deposition and biochar addition on N₂O and CO₂ emissions and NH₃ volatilization from agricultural and forest soils. Repacked soil columns were subjected to six N deposition events over a 1-year period. N was applied at rates of 0 (N0), 60 (N60), and 120 (N120) kg Nh a^?1 yr^?1 without or with biochar (0 and 30 t ha^?1 yr^?1). For agricultural soil, adding N increased cumulative N₂O emissions by 29.8% and 99.1% (p < 0.05) from the N60 and N120 treatments, respectively as compared to without N treatments, and N120 emitted 53.4% more (p < 0.05) N₂O than the N60 treatment; NH₃ volatilization increased by 33.6% and 91.9% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 43.6% more (p < 0.05) NH₃ than N60; cumulative CO₂ emissions were not influenced by N addition. For forest soil, adding N significantly increased cumulative N₂O emissions by 141.2% (p < 0.05) and 323.0% (p < 0.05) from N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 75.4% more (p < 0.05) N₂O than N60; NH₃ volatilization increased by 39.0% (p < 0.05) and 56.1% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and there was no obvious difference between N120 and N60 treatments; cumulative CO₂ emissions were not influenced by N addition. Biochar amendment significantly (p < 0.05) decreased cumulative N₂O emissions by 20.2% and 25.5% from agricultural and forest soils, respectively, and increased CO₂ emissions slightly by 7.2% and NH₃ volatilization obviously by 21.0% in the agricultural soil, while significantly decreasing CO₂ emissions by 31.5% and NH₃ volatilization by 22.5% in the forest soil. These results suggest that N deposition would strengthen N₂O and NH₃ emissions and have no effect on CO₂ emissions in both soils, and treatments receiving the higher N rate at N120 emitted obviously more N₂O and NH₃ than the lower rate at N60. Under the simulated N deposition circumstances, biochar incorporation suppressed N₂O emissions in both soils, and produced contrasting effects on CO₂ and NH₃ emissions, being enhanced in the agricultural soil while suppressed in the forest soil.     

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.     

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.     

A Quantitative Respirometric Method for Monitoring Compost Stability

Compost stability was quantified using dissolved oxygen (D. O.) respirometry during composting of municipal solid waste (MSW) in a pilot-scale system. Changes in stability of samples taken at various times during the composting process were verified with chemical and physical tests. Rates of change of oxygen level in air over a compost sample incubated in a flask at 37°C were converted to a rate of O₂ uptake/(g volatile solids · hour). Oxygen uptake, determined with D. O. respirometry and converted to rates of dry matter loss, was correlated with actual rates, calculated from energy balances observed in the pilot-scale system. The method can be used either as a simple quality control measure or in a more complex way to calculate rates so that efficiency within or among composting facilities can be compared.     

Temperature response of ammonia and greenhouse gas emission from manure amended silty clay soil

Soil temperature plays an important role in organic matter decomposition, thus likely to affect ammonia and gaseous emission from land application of manure. An incubation experiment was conducted to quantify ammonia and greenhouse gas (GHG) (N₂O, CO₂ and CH₄) emissions from manure and urea applied at 215?kg N ha^?1 to Fargo-Ryan silty clay soil. Soil (250?g) amended with solid beef manure (SM), straw-bedded solid beef manure (BM), urea only (UO), and control (CT) were incubated at 5, 10, 15, and 25 °C for 31 days at constant 60% water holding capacity (WHC). The cumulative GHGs and NH₃ emission generally increased with temperature and highest emission observed at 25 °C. Across temperature levels, 0.11–1.3% and 0.1–0.7% of the total N was lost as N₂O and NH₃, respectively. Cumulative CO₂ emission from manure was higher than UO and CT at all temperatures (P?<?0.05). Methane accounted for <0.1% of the total C (CO₂?+?CH₄) emission across temperatures. The Q₁₀ values (temperature sensitivity coefficient) derived from Arrhenius and exponential models ranged 1.5–3.7 for N₂O, 1.4–6.4 for CO₂, 1.6–5.8 for CH₄, and 1.4–5.0 for NH_3. Our results demonstrated that temperature significantly influences NH₃ and GHG emissions irrespective of soil amendment but the magnitude of emission varied with soil nutrient availability and substrate quality. Overall, the highest temperature resulted in the highest emission of NH₃ and GHGs.     

糠醛渣添加量对奶牛粪堆肥腐熟及氨气释放量的影响

为解决奶牛场粪污和糠醛渣的贮存及其对环境的污染问题,我们探究不同添加量的糠醛渣对奶牛粪条垛式堆肥腐熟及氨气释放量的影响,以新鲜奶牛粪和小麦秸秆为主料,分别添加质量分数为3%、6%、9%的糠醛渣进行为期35 d的堆肥试验。结果表明,当糠醛渣添加量质量分数为3%~9%时,新鲜奶牛粪和小麦秸秆堆肥的产品的含水率、pH、NH₃释放量分别比对照不添加糠醛渣下降13.86%~20.91%、1.09%~4.37%、12.86%~30.82%,种子发芽指数和C/N分别提高24.35%~43.48%、12.54%~31.22%。综上考虑认为,采用奶牛粪堆肥时,添加质量分数为3%~9%的糠醛渣,可促进堆肥物料的分解转化,加快腐熟速度,降低氨气释放量。     

二氧化锰对微好氧堆肥腐熟、温室气体及臭气排放的影响

为探究锰矿物添加对微好氧堆肥过程腐熟、温室气体和臭气排放的影响,以由厨余垃圾、水稻秸秆、羊粪和尾菜组成的多元混合物料堆肥为研究对象,共设3个处理,采用间歇通风方式,将通风速率为0.14 L/（kg·min）设置为好氧堆肥对照（CK）,速率为0.06 L/（kg·min）为微好氧处理（T1）,添加二氧化锰（MnO₂）的微好氧处理为T2。结果表明：多元废弃物好氧或微好氧堆肥在堆制70 d后均能腐熟,但T2处理腐熟度显著高于T1。微好氧处理T1、T2减少了26.47%～30.29%的NH₃和33.19%～38.60%的N₂O的排放,总温室效应减少了29.26%～31.38%。臭气的排放集中在前14 d,T1、T2处理的H₂S和VOCs的释放量显著增加了320.35%～501.04%和39.82%～53.63%。因此,微好氧堆肥可达到减排目的,但却加剧臭气的排放;MnO₂可提高促进堆肥腐熟,降低温室气体和臭气的排放。     

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).     

Cocomposting of Crawfish and Agricultural Processing By-Products

Disposal of crawfish processing residuals (hereinafter, referred to as crawfish residuals) poses a challenging problem to the rapidly expanding crawfish industry. Cocomposting is examined as a waste management alternative to landfill disposal. Four agricultural processing by-products were evaluated for use as bulking agents in composting crawfish residuals: wood chips, rice hulls, bagasse, and bark. Approximately 5 to 6.5 volumes of each bulking agents were mixed with one volume of crawfish residuals in 0.3-m³ composting reactors. Compost temperature was continuously monitored, and moisture content was maintained within a desirable range. Samples were collected twice weekly throughout the 50-d composting process. Use of bagasse as a bulking agent led to the largest reduction in volatile solids (27.6 percent), organic C (55.3 percent), particle size (64.7 percent), and compost volume (52.8 percent). Finished compost using bagasse contained the greatest concentration of N (18.4 g N/kg and 160 mg NH₄-N/kg). Self-heating patterns and decomposition of crawfish residuals were satisfactory using all four bulking agents, and no odor, insect or other nuisance problems were detected. The finished products of all compost mixtures were suitable for use as mulch or reuse as bulking agents.     

The Use of Bacillus Licheniformis HA1 To Accelerate Composting of Organic Wastes

The effect of Bacillus licheniformis HA1 cell density on the acceleration of organic waste composting was tested in a bench-scale composting system utilizing a process limit temperature of 60°C. Variables measured during composting were CO₂ evolution rate, conversion of substrate carbon and pH. When an initial cell density of 2.0×10⁴ cfu/g-dry solid was used, the strain HA1 increased in number and prevented the decrease in pH during the early stage of composting. This resulted in enhanced populations of other thermophiles and increased the rate of organic matter decomposition. By contrast, no effect was observed at a lower cell density of HA1. It was found that the minimum cell density of HA1 to accelerate organic decomposition was around 10⁴-10⁵ cfu/g dry solid of raw material.     

Yard Waste Composting: Studies Using Different Mixes of Leaves and Grass in a Laboratory Scale System

Composting has become a widely used method of recycling yard wastes such as leaves and grass. However, very little information is available on the chemical changes that occur during the composting of different mixtures of leaves and grass. In this study, three different mixes of leaves and grass were composted at approximately 60% moisture in a temperature controlled laboratory scale system. The mixes, which consisted of all leaves (Mix 1); 2/3 leaves + 1/3 grass (Mix 2); and 1/3 leaves + 2/3 grass (Mix 3), had initial C:N ratios of 48, 30 and 22, respectively. The compost process was monitored by measuring the rate of CO₂ evolution, pH, stability, the degree of humification and changes in polysaccharide, carbon, nitrogen and organic matter content. Results showed that the greater the grass content of the mix, the higher the initial pH and the faster the rate of CO₂ evolution, organic matter loss and nitrogen loss. After 43 days of composting, Mixes 1, 2 and 3, lost, respectively 61%, 74% and 78% of the cellulose, 57%, 79% and 82% of the hemicellulose and 40%, 49% and 42% of the acid-insoluble organic matter. Humification indices and stability tests indicated that composts produced from the three mixes were well humified and stable.     

Ammoniakemissionen aus alternden Pflanzen und bei der Zersetzung von Ernterückständen

Ammonia emissions from senescing plants and during decomposition of crop residues NH₃ emissions from plant stands, measured under simulated environmental conditions with the wind tunnel method, ranged between 0.8 and 1.4% of the N content of the shoot, equivalent to 1.1 to 2.9 kg NH₃-N ha^?1. The highest emissions were observed in faba beans whereas the emissions in winter wheat, spring rape and white mustard were lower. The total NH₃ emissions were not affected by removing a part of the ears (sink reduction), but emissions occurred earlier, as did the plant senescence. This suggests that the NH₃ emissions are closely related to senescence. NH₃ emissions from decomposing crop residues ranged from 0.9 to 3.7% of the N content. The emissions from sugar beet leaves and potato shoots with high water content reached from 8.6 up to 12.6 kg N ha^?1, whereas the emissions from field bean straw with high dry matter and N content were relatively low. (3.1 kg N ha^?1, or 0.9% of the N content). The NH₃ emissions from sugar beet leaves were reduced by 81% by ploughing and 63% by mulching.     

Composting of Source-Separated Household Organics At Different Oxygen Levels: Gaining an Understanding of the Emission Dynamics

Source-separated household organics were composted in a reactor at three oxygen levels, 16%, 2.5% and 1% in the compost gas. Short-chained fatty acids were initially present in the compost material, and were also produced during the mesophilic phase at all three oxygen levels. This indicated that partial anaerobic conditions existed. No NH₃ emissions occurred during the mesophilic phase due to acidic conditions. Composting at 2.5% and 1% O₂ concentrations prolonged the mesophilic phase and reduced the microbial activity as compared to 16% O₂. This led to delayed and decreased emissions of NH₃. Nitrous oxide was not formed during thermophilic conditions. Methane, which was measured at 2.5% and 1% O₂, was only found during thermophilic conditions. The emission of methane indicates that anaerobic conditions occurred during the thermophilic phase. The main reactions regulating pH during composting were outlined involving the ion species VFA, NH₄⁺/NH₃ and CO₂/HCO₃^?/CO₃^2?.     

Variability of Atmospheric Ammonia In High-Rise,Caged Layer Composting

High concentrations of atmospheric ammonia (NH₃) can impact poultry and human health. During composting inside high-rise, caged layer facilities, high concentrations of NH₃ are produced due to low carbon to nitrogen ratios of composting materials and the confined building environment. This study characterized the spatial and temporal variability of NH₃ during in-house composting as a preliminary step to identifying control measures. Boric acid solutions and gas sensors were used to measure NH₃ in 2 m × 7.5 m grid patterns for three high-rise laying hen structures during composting. Spatial variability was evident in all buildings, with areas of higher NH₃ concentration near the center of buildings away from ventilation fans. Ammonia concentrations in the composting area frequently exceeded human health standards for 8-hour and 10-minute exposure periods of 25 and 35 μL L^?1, respectively. Ammonia concentrations were lower in cage areas of high-rise structures due to the negative pressure ventilation system venting gas directly from the composting area to the outside of buildings. Over a 6-week composting cycle, NH₃ generally increased as compost accumulated in the structure. Over 1-day periods of time, NH₃ concentrations varied with fluctuations in outdoor air temperatures and fan operation. During turning of compost, atmospheric NH₃ reached a high of nearly 50 μL L^?1 for over 30 minutes. Monitoring NH₃ and altering the ventilation of poultry houses could reduce NH₃ concentrations below critical levels at peak times such as during turning. However, ventilation as a solution to high NH₃ levels may not be environmentally sustainable. Other alternatives such as chemical and process controls, structural changes, or biofiltration should be explored to prevent NH₃ volatilization or remove NH₃ from air vented during in-house composting.     

Kinetics of Aerobic Bioremediation of a Diesel-Contaminated Sandy Soil: Effect of Nitrogen Addition

In this paper, the effect of nitrogen addition on the aerobic bioremediation of a diesel-contaminated soil was studied. Soil was artificially contaminated with diesel at an initial 2% concentration (on a dry soil basis). Nitrogen was added as NH₄Cl in a single load at the start of the experiment at concentration levels of 0, 100, 250, 500, 1,000, and 2,000 mg N/dry kg soil, and uncontaminated and unamended soil O₂ consumptions were studied. Diesel degradation was indirectly studied via measurements of O₂ consumption and CO₂ production, using manometric respirometers. Results showed that the 250 mg N/dry kg concentration resulted in the highest O₂ consumption among all runs, whereas O₂ consumption was reduced by N additions greater than 500 mg N/dry kg. Zero to 0.6 order degradation kinetics appeared to prevail, as was calculated via the oxygen consumption rates. A theoretical biochemical reaction for diesel degradation was developed, based on measurement of the final diesel concentration in one of the runs. According to the stoichiometry, the optimal N requirements to allow complete diesel degradation should be approximately 0.15 g N/g diesel degraded or 1,400 mg N/dry kg of soil, based on the initial diesel concentration used in this study. This implies that N should be added in incremental loads.