ASSESSMENT OF HEAVY METALS IN HYDROCHAR PRODUCED BY HYDROTHERMAL CARBONIZATION OF DAIRY MANURE

Hydrochar produced from dairy manure is a regulated biosolid if being promoted for agricultural applications thus must have the properties that comply with all environmental standards and government regulations,including the levels of heavy metals(HMs).In this study,systematic research was conducted on HM levels in hydrochar from dairy manure and on the effects of processing conditions,including processing temperature(180–255℃),holding time(30–120 min)and solid content of manure slurry(2%–15%),through a central composite design and statistical analyses.It was found that HMs can be retained in hydrochar,ranging from 40%to 100%.The processing temperature and solid content in the feed were the most influential process parameters that affected HMs retention in hydrochar.Statistical analysis showed that there was no single optimal point to minimize HMs retained in hydrochar,but there were minimization points at given processing time and solid content.Most HMs concentrations were higher in hydrochar than those initially in dairy manure but were greatly below the thresholds as set by the US government regulations.Thus,hydrochar is feasible for use as a phosphorus-enriched organic fertilizer and/or soil amendment for agricultural applications without serious concerns about HMs it might contain.

Microorganism population in two-phase anaerobic fermentation of separated liquid of dairy manure

In order to reduce incomplete fermentation caused by high substrate viscosity and low mass transfer efficiency during fermentation process,batch and two-phase anaerobic fermentation experiments were conducted in this study.Dairy manure was separated by using solid-liquid separator firstly.Separated liquid(SL)and diluted dairy manure(DDM)as raw materials were evaluated in terms of gas production performance for both batch and two-phase anaerobic fermentation.The microorganism population was characterized by scanning electron microscope(SEM)and Denaturing Gradient Gel Electrophoresis(DGGE).The results showed that Volatile Solid(VS)methane yield of SL was 124.51 L/kg VS,which was 2.09 times higher than that of DDM(59.50 L/kg VS)in batch anaerobic fermentation.The Bacteroides and Veillonella with higher activity were the majority microorganism population in acidogenic phase,whereas the Firmicutes and Corynebacterium with methanogenic properties became the predominant microorganism population in methanogenic phase.This study achieved the phase separation and improved the gas production performance.

Two-phase anaerobic co-digestion of dairy manure with swine manure

In order to solve the problems associated with high fiber content,and the ensuing lower biogas volume yield in anaerobic digestion of dairy manure,a study of the co-digestion of separated liquids from dairy manure combined with swine manure using a two-phase anaerobic digestion process was conducted.The influence of level of total solids(TS)and hydraulic retention time(HRT)of the mixed liquor on the specific methane production were studied.Three TS levels 8%,10%and 12%were investigated.Analysis of the results show that a maximum specific methane yield of 132.99 L/kg volatile solids(VS),can be obtained with a TS of 9%,an inoculation rate of 30%,the duration of hydrolytic acidification phase of 5 d,and an HRT of the methanogenic phase of 10 d.These findings could provide directions for improving the biogas production by performing the co-digestion of dairy manure with swine manure.

Anaerobic co-digestion of sodium hydroxide pretreated sugarcane leaves with pig manure and dairy manure

Sugarcane leaves(SL)pretreated by alkali was used as substrate to enhance biogas production via mesophilic anaerobic digestion(AD)in this study.Effectiveness of different concentrations of NaOH pretreatment on AD performance was investigated.Results showed that compared to untreated sample of SL,the lignocellulose(LCH)content of NaOH pretreated group was decreased by 5.79%-16.85%.However,the cumulative biogas production of the pretreated samples increased in the range of 34.54%-82.67%;moreover,T90 was shorten by 5-7 d.The highest anaerobic digestibility of SL was achieved at 6%NaOH pretreatment,which produced 287.30 mL/g TS of biogas.A significant interactive effect of the three parameters(temperature,SL/manure mixing ratio and C/N ratio)was found on the biogasification of anaerobic co-digestion,and a maximum biogas production was achieved at 36.2oC,mixing ratio of 1.6 and C/N ratio of 29.2.These show that the verification experiment confirmed the optimization results.This study provides meaningful insight for exploring efficient pretreatment strategy and optimal condition to stabilize and enhance AD performance for practical application.

Effects of anaerobic digestion and aerobic treatment on the reduction of gaseous emissions from dairy manure storages

Effects of anaerobic digestion and aerobic treatment on the reduction of gaseous emissions from dairy manure storages were evaluated in this study.Screened dairy manure containing 3.5%volatile solids(VS)was either anaerobically digested or aerobically treated prior to storage in air-tight vessels.Anaerobic digestion was carried out using a mesophilic anaerobic sequencing batch reactor operated at a hydraulic retention time of 20 days and an organic loading rate(OLR)of 1 gVS/L/day.Aerobic treatment was achieved using an aerobic reactor operated at a hydraulic retention time(HRT)of 10 days and an OLR of 2 gVS/(L·d).The treated manure was put into the storage on a daily basis for a period of 180 days.All the gases produced during this period were captured and analyzed for methane,carbon dioxide and volatile organic compounds(VOCs).Untreated manure was stored and analyzed in the same way as the treated manure and used as a control for comparison.The results show that low amounts of gases were produced during the first 84 days of storage in both treated and untreated manure,but increased significantly after this time point.The generally expected positive impacts of anaerobic and aerobic treatment on the reductions of methane and VOCs were confirmed in this study.However,the effects of anaerobic and aerobic treatment varied over the time of storage,especially for VOCs.The results of this study indicate that to achieve significant reductions in VOC emission the storage time of anaerobic digester or aerobic reactor effluent should be limited to no more than 100 days.

Patterns of dairy manure management in China

The dairy industry in China is rapidly developing,particularly in terms of the upscaling of dairy farms.However,nutrient-rich manure brings challenges to the sustainability of the dairy industry.This study investigated and reviewed the patterns of dairy manure management in China,and the results indicate that dairy manure could be used as an organic fertilizer because of its high organic nutrient content and low metal content.However,legislation prohibits the application of untreated(raw)dairy manure.An existing technology for handling animal slurry is the separation into a liquid and a solid manure fraction.The solid fraction can be used as compost and bedding materials,and it has limited environmental risk.However,the emissions from the storage of liquid manure need further attention.The cycle of manure production,collection,transportation,separation and storage can only be closed if the nutrients are eventually applied to grass and arable land according to crop needs.Therefore,distribution of knowledge on nutrient levels,crop needs and nutrient management plans,supported by legislation on maximum application standards,is needed.In this way,an environmentally friendly development of dairy manure management might be possible.

Succession of bacteria communities during production and application of dairy bedding by membrane-covered aerobic fermentation

The cost of dairy manure treatment and bedding material purchase increases the operating cost of the dairy farm.Membrane-covered aerobic fermentation system has been widely used for dealing with dairy manure and recycling the final product as bedding material.However,the microbial safety in each processing step is still uncertain.To better understand the bacterial community dynamics during the whole bedding conversion process,a full-chain and large-scale experiment including 16-day membrane-covered aerobic fermentation and 11-day bedding material application was conducted.The results showed that the pile temperatures in the fermentation stage rapidly increased to 80°C and maintained>50°C for more than 11 days and the use of fermentation product as bedding material provided cows with a stable and comfortable bedding environment.The Chao1 and Shannon index decreased at the end of the fermentation stage and remained stable in the application stage,indicating that membrane-covered aerobic fermentation effectively killed some pathogenic bacteria and guaranteed both the maturity and stability of the final product.The dominant bacteria in the fermentation stage were Acinetobacter,Thermus,and Rhodothermus at genus level.Seven common potential pathogens of mastitis(Staphylococcus,Enterococcus,Serratia,Pseudomonas,Corynebacterium,Mycobacterium,and Bacillus)were found at the end of fermentation stage but the relative abundance was low(0.0025%-0.2727%).The dominant bacteria in the application stage mainly included Acinetobacter,Pseudomonas,and Flavobacterium at the genus level.The relative abundance of Pseudomonas increased in the application stage,which was a reminder to the dairy farm to pay attention to the disinfection and timely replacement of bedding material to prevent the occurrence of dairy mastitis.The results of this study contributed deep understanding of the microorganism-driven bedding conversion process and provide practical guidance and cautions for the bedding materials application.

Manure nutrient application on a Chinese dairy farm with arable land:A case study based on Dutch experience of equilibrium fertilization

For a Chinese dairy farm with 2200 milking cows,the annual manure production and manure nutrients(nitrogen and phosphorus)were estimated.Gaseous nitrogen losses from cattle housing with scraped solid floors were based on on-farm measurements.Based on experiences from the Netherlands,nutrient levels in the solid and liquid fractions after slurry separation were estimated.On the basis of assumptions for nutrient losses during covered lagoon storage and land application of the liquid fraction,nitrogen and phosphorous fertilization rates were calculated for the 67 hm^(2)of agricultural land that receive the liquid fraction by gravity irrigation.The results show that the application rates of nitrogen and phosphorous significantly exceed the crop needs,which will probably result in losses to soil and water.In order to aim for a balance between nutrient application and crop needs and,as such,reduce environmental harm,the authors recommend to establish application standards for nitrogen and phosphorous on arable land in China and to formulate farm-specific Nutrient Management Plans.

Cu(Ⅱ)and ammonium adsorption from dairy cattle breeding sewage by phosphorus-modified dairy cow manure hydrochar

To realize the synergistic treatment of dairy cow manure solids and dairy cattle breeding sewage,this study produced phosphorus-modified hydrochar by dairy cow manure solids impregnated with potassium phosphate(K_(3)PO_(4)).And then,the adsorption characteristics of Cu(Ⅱ)and ammonium(NH_(4)^(+))in dairy cattle breeding sewage under different dosages and adsorption time conditions of modified hydrochar were explored.The results show that the specific surface area and total pore volume of the hydrochar were increased by phosphorus-modified.The adsorption amount of hydrochar per unit-mass decreased with the increase in the dosage.With the increase in the dosage,the adsorption capacity of Cu(Ⅱ)decreased from the initial 26.16 mg/g to 3.38 mg/g.The adsorption of Cu(Ⅱ)and NH_(4)^(+)in sewage by hydrochar was mainly chemical adsorption,which was mainly affected by chelation and ion exchange.This adsorption was more inclined to single-molecular layer adsorption.Both the pH values and the ionic strength influenced the competitive adsorption between Cu(Ⅱ)and NH_(4)^(+).The higher the pH value was,the greater the adsorption amount,and the stronger the adsorption capacity by hydrochar.Moreover,the increase in the ionic strength decreases the adsorption capacity of hydrochar.

Modeling temperature and moisture dependent emissions of carbon dioxide and methane from drying dairy cow manure

Greenhouse gas emissions due to biological degradation processes of animal wastes are significant sources of air pollution from agricultural areas. The major environmental controls on these microbe-induced gas fluxes are temperature and moisture content. The objective of this study was to model the effects of temperature and moisture content on emissions of CO2 and CH4 during the ambient drying process of dairy manure under controlled conditions. Gas emissions were continuously recorded over 15 d with paired fully automated closed dynamic chambers coupled with a Fourier Transformed Infrared gas analyzer. Water content and temperature were measured and monitored with capacitance sensors. In addition, on days 0, 3, 6, 9, 12 and 15, p H, moisture content, dissolved organic carbon and total carbon(TC) were determined. An empirical model derived from the Arrhenius equation confirmed high dependency of carbon emissions on temperature and moisture content. Results indicate that for the investigated dairy manure, 6.83% of TC was lost in the form of CO2 and 0.047% of TC was emitted as CH4.Neglecting the effect of temperature, the moisture contents associated with maximum gas emissions were estimated as0.75 and 0.79 g$g–1 for CO2 and CH4, respectively.

Effect of Deficit Irrigation Practice on Nitrogen Mineralization and Nitrate Nitrogen Leaching under Semi-Arid Conditions

Agricultural sector acts as a major consumer of water which accounts for 70 percent of global freshwater use. Water scarcity acts as an imminent threat to agriculture, there is a need to use those irrigation and management practices that could overcome this overwhelming situation of water scarcity. Lab incubation study was designed to evaluate the effect of different moisture levels (50%, 60%, 70%, 80%, 90%, and 100% FC) on nitrogen mineralization rate. Net nitrogen mineralization was shown at 60% and 80% FC levels. Two optimized irrigation levels (I0.6 and I0.8) along with four levels of dairy manure (10, 15, 20, and 25 Mg ha-1) were used in a lysimetric trial. Nitrate-nitrogen was measured at four depths (D1: 30 cm, D2: 60 cm, D3: 90 cm, and D4: 120 cm). Results showed strong interaction of irrigation and dairy manure at all depths. Mean maximum nitrate-nitrogen concentration was shown under full irrigation at 120 cm soil depth with the application of DM ®25 Mg ha-1. Under two levels of deficit irrigation, I0.8 has shown maximum nitrate-nitrogen concentration at 90 cm soil depth with the application of DM25, however, deficit irrigation level I0.6 restricted nitrate-nitrogen movement up to 60 cm soil depth, and high concentration was found at 30 cm soil depth. We concluded that deficit irrigation practice along with dairy manure resulted in more nitrate-nitrogen in the upper 60 cm layer of soil where it can be more available for the crops.

Methane emissions during storage of different treatments from cattle manure in Tianjin

Many studies on methane emissions from animal manure have revealed that animal manure is a major source of methane emissions to the atmosphere that can have negative consequences for people, animals and environment. In general, the release of methane can be influenced by the type of feed taken by animals, temperature, manure characteristics and so on. This study aimed at quantifying and comparing methane release from dairy manure with different piling treatments. Four treatments were designed including manure piling height 30, 45, 60 cm and adding 6 cm manure every day until the piling height was 60 cm. Static chamber method and gas chromatography were adopted to measure the methane emissions from April to June in 2009. Methane emission rates of all four manure treatments were low in the first week and then increased sharply until reaching the peak values. Subsequently, all the methane emission rates decreased and fluctuated within the steady range till the end of the experiment. Wilcoxon nonparametfic tests analysis indicated that methane emission rate was greatly influenced by manure piling height and manner. There were no significant relationships between methane emission rates and the temperatures of ambience and heap. However, regression analysis showed that the quadratic equations were found between emission rates of all treatments and the gas temperature in the barrels.

Bioreactor performance and microbial community dynamics in a production-scale biogas plant in northeastern China

In cold regions,heating is necessary to maintain the continuous and steady year-round operation of biogas fermentation.In this study,changes in the liquid composition,biogas production,and microbial diversity in heated-and unheated-phase samples were evaluated in a production-scale biogas plant that was fed continuously with cattle manure as a mono-substrate in Heilongjiang province in northeastern China.The volatile solid(VS)and volatile fatty acid(VFA)contents both gradually decreased in the heated and unheated fermentation processes.The chemical oxygen demand(COD)removal efficiency in the unheated phase sampled on June 15(s-6-15)and October 15(a-10-15)and in the heated phase sampled on January 15(w-1-15)was 63.35%,44.2%and 44.0%,respectively.The biogas production yields were in agreement with the results obtained for the VS and VFA contents and COD removal efficiency.The performance of the reactor in the heated phase was less efficient than that in the unheated phase,and the biogas production efficiency in June-August was higher than that in the other months.However,the CH4 content in the biogas remained similar all year.Moreover,ARDRA(Amplified Ribosomal DNA Restriction Analysis)was used to study the microbial community composition in the fermentation process.The results showed that the methanogenic archaeal consortium consisted mainly of members of the genera Methanomicrobiales and Methanosarcinales.In the heated phase,hydrogenotrophic methanogens represented the dominant methanogen in w-1-15 feedstock.After fermentation,the strict aceticlastic methanogen Methanosaeta became the dominant methanogen.In the unheated phase,the hydrogenotrophic methanogens and aceticlastic methanogens were equivalent in s-6-15 feedstock and effluent,and aceticlastic methanogens were dominant in both a-10-15 feedstock and effluent.Assessments of the bacteria diversity of the microbial communities revealed that the common strains in the feed and effluent of the three samples included the rumen bacteria,Bacteroides,Clostridium,Ruminococcaceae and Proteobacteria.

INTEGRATED CROP-LIVESTOCK SYSTEMS:LESSONS FROM NEW YORK,BRITISH COLUMBIA,AND THE SOUTH-EASTERN UNITED STATES

Livestock production in the United States(US)and Canada is diverse,but shows a common trend in most livestock sectors toward fewer farms producing the majority of animal products despite a large number of farms still small in production scale.The migration to larger and more concentrated animal feeding operations in beef finishing and poultry,swine,and dairy production allows processors to streamline supplies to meet market demand for abundant,low-cost livestock products,whether that be for packaged meat,dairy products,or eggs.With concentration of livestock operations comes the challenge of managing manures.When sufficient land is available and nutrients are needed,livestock manure is an excellent nutrient source and land application is the preferred method of recycling this resource.However,when livestock production is constrained in a geographical area and animal densities are high,manure may become an environmental liability with potentially greater risk for runoff and leaching of nutrients,emission of odors,ammonia,and greenhouse gases,and release to the environment of pathogens and chemicals of emerging concern.Addressing these challenges now and into the future requires learning from mistakes and adopting successful approaches.We describe different levels of integration between livestock and crop producers in New York,British Columbia,and the south-eastern US as learning opportunities to improve economic and environmental sustainability.Examples show that effective solutions should recognize(1)manure has value and is not just a cost,(2)farmers,farm advisors,extension educators,nutrient management planners,crop advisors,nutritionists,state agency personnel,regulators,and university researchers need to be active participants in development of solutions,and(3)change to a sustainable future requires a combination of government regulation and outcome-based incentives.