Chamber measurement methods and aeration effect on greenhouse gas fluxes during composting

Composting has the potential to mitigate methane (CH4) and nitrous oxide (N2O) emissions from manure.  The heterogeneous nature of emitting surfaces makes it difficult to quantify these emissions.  CH4 and N2O fluxes measured using eight small chambers (0.72 m2) and a mega chamber (90 m2) were compared, and the effect of aeration on the fluxes during composting was studied.  Two batches of compost were placed in three channels and 2-3 small flux chambers were deployed on each channel.  The channels were enclosed by a building serving as a mega chamber.  Chamber location significantly affected gas fluxes, pointing to strong spatial heterogeneity.  Mean CH4 fluxes from the small chambers were similar or 1.4 times higher compared to the mega chamber.  Mean N2O fluxes from the small chambers were 50%-55% lower compared to the mega chamber.  Channel edges, not captured by the small chambers, were potentially significant ‘hot spots’ for N2O production.  When only small chambers are used for flux measurements, a large number should be strategically positioned to cover different areas of the emitting surface so as to capture a representative flux.  On the other hand, if a few small chambers are used, they should be moved frequently to different locations on the emitting surface.  Temporal variations in CH4 and N2O fluxes were similar for all the chambers, including periods with active aeration.  Correlation of total aeration time with CH4 fluxes was insignificant (r = -0.097), but was positive with N2O (r = 0.556).  The flushing of stored CH4 at the onset of aeration, likely promoted fluxes, as opposed to the expected flux decrease with higher aeration time.  The purging of stored N2O enhanced the expected stimulation of N2O production at high aeration times, resulting in the positive trend observed for N2O fluxes.  Our results suggest that a mega chamber that covers a larger emitting surface area can avoid biases in flux estimates due to spatial variability of the source.   Keywords: chamber measurements, compost, greenhouse gases, aeration, flu

Influence of environmental factors and the addition of wood shavings on ammonia and odour emissions from fresh livestock manure

 N. M. Ngwabie, K.-H. Jeppsson, G. Gustafsson, S. Nimmermark(Department of Rural Buildings and Animal Husbandry, Swedish University of Agricultural Sciences,P.O. Box 86, S-230 53 Alnarp, Sweden) Abstract: Gaseous emissions from livestock manure may adversely affect human and animal health as well as the surrounding environment.  In an effort to understand and mitigate these emissions, the effects of different environmental factors and the addition of wood shavings on ammonia and odour emissions from fresh pig and dairy cow manure were studied.  The manure was divided into two portions and wood shavings (25% pine and 75% spruce) were mixed with one portion.  Emissions from equal volumes (0.009 m3) of both portions were measured at different environmental conditions in a flux chamber.  The manure temperature was varied between 15 – 30 ºC.  Fresh air at temperatures between 16 – 26 ºC was passed at a fixed rate over the manure.  The addition of wood shavings decreased the total-N and NH4+-N, but increased the pH of the manure at the end of the experiment.  The temperature of the manure with wood shavings increased faster than that of the manure without wood shavings.  The ammonia emission from the pig manure (0.08 – 0.41 mg m-2 s-1) was on average much higher than the ammonia emission from the cow manure (0 – 0.08 mg m-2 s-1).  The odour emission from the pig manure was high (21 –   930 OU m-2 s-1), and significantly higher than the odour emission from the cow manure (1–6 OU m-2 s-1).  A positive correlation was found between the ammonia emissions and the manure temperature.  Ammonia emissions were about twice higher at manure temperatures of about 25 ºC than emissions at about 15 ºC.  Odour emissions were positively correlated with the temperature of cow manure.  Ammonia emissions at 25 ºC were high, while odour emissions at 25 ºC were lower than those at 20 ºC for the pig manure with wood shavings.  The emissions from the cow manure but not from the pig manure were positively correlated to the water vapour pressure.  The measurements indicated a positive correlation between ammonia and odour emissions for the cow manure as well as for the pig manure without wood shavings.  The addition of wood shavings to animal manure does not seem to automatically mitigate ammonia or odour emissions as it also affects the temperature and the pH.Keywords: dry matter, C/N ratio, volatilization, temperature, ammonium, Sweden Citation: Ngwabie N. M, K.-H. Jeppsson, G. Gustafsson, S. Nimmermark.  Influences of environmental factors and the addition of wood shavings on ammonia and odour emissions from fresh livestock manure.  Agric Eng Int: CIGR Journal, 2010, 12(3): 68-81.&nbsp

Concentrations and Settling Rates of Particulate Matter in Laying Hen Barns in the Hot Climatic Region of Cameroon

Particulate matter (PM) serves as a carrier of adhesive gaseous compounds, and may result to an underestimation of gas emissions from livestock barns when only filtered air samples are analysed. PM concentrations have hardly been studied in the unique livestock production system of Sub-Saharan Africa. This study was aimed at generating baseline data for PM (total suspended particulates) concentrations and settling rates in laying hen barns with cemented floors and wood shavings added as an initial bedding material. Measurements were conducted in two naturally ventilated laying hen barns in Cameroon; a barn with 4 months old hens that had just stated laying eggs and a barn with 18 months old egg laying hens. PM concentration was determined gravimetrically from the mass collected on a 1.2 µm diameter filter. Four plates with a surface area of 0.09 m2 each, hung at a height of 1.7 m from the floor were used to gravimetrically determine PM settling rates over a fixed duration. Results revealed that PM concentrations correlated with the age of the hens. PM concentrations were 6.61 mg m-3 (6.33 µg hen m-3) and 10.17 mg m-2 (16.95 µg hen m-3) in the barns with 4 and 18 months old hens respectively. PM settling rates were 53.79 mg m-2 h-1 (51.5 µg hen m-2 h-1) and 115.52 mg m-2 h-1 (192.5 µg hen m-2 h-1) in the barns with 4 and 18 months old hens respectively. No fixed location within the barn experienced consistently high or low PM settling rates. Temporal and spatial variations in settling rates could be related to management routines and hen activity. Results also indicated that variations in PM concentrations in the air accounted for about 60% of the variations in the settling rates. This research highlights the need for PM emission mitigation strategies that are applicable to the climate and production system in Sub-Saharan Africa

Gas emissions from dairy cow and fattening pig buildings

The objective of this research is to contribute to the knowledge concerning the abatement of gas emissions from livestock production. Investigations regarding the choice of sampling locations for gas concentration measurements, quantification of gas emissions and the factors that affect gas emissions were conducted. NH₃, CH₄, CO₂ and N₂O emissions were measured from two naturally ventilated buildings for dairy cows and from a mechanically ventilated building for fattening pigs. Animal activity, temperature and humidity were also measured. Gas and odour emissions from manure samples with and without the addition of wood shavings were measured in a flux chamber at different air and manure temperatures. Significant differences existed in the mean concentrations of all the gases at various indoor sampling locations in a naturally ventilated building for dairy cows. The differences in gas concentrations between various sampling locations were much smaller for long-term, relative to short-term, measurements, suggesting that a single sampling location during long-term measurements may generate representative data. Decreasing daily animal activity was associated with increasing pig weight, and with increasing air temperatures for the cows. Diurnal variations in gas emissions were related to feeding/cleaning routines and to animal activity. Daily emissions from the pig building increased with pig weight and temperature. Air temperature was more important than cow activity for daily NH₃ emissions while cow activity was more important than air temperatures for daily CH₄ emissions. Reducing manure temperatures and increasing manure carbon-to-nitrogen ratio are potential NH₃ abatement techniques. However, low air temperatures may increase cow activity which may in turn increase CH₄ emissions. Increasing the frequency of manure removal from the floor and from animal buildings reduces indoor emissions of most gases. Low N₂O emissions were measured from the buildings in this study; hence the use of liquid manure systems might reduce N₂O emissions

Effect of Wood shavings on the Temperature Profile of Livestock Waste during Composting with Daily Turning

Measurements were conducted to assess the impact of wood shavings on the temperature profiles of cattle and pig manure during aerated composting. Cattle stomach waste to wood shavings were mixed in mass ratios of 100:0%, 80:25%, and 75:25% and placed in three different chambers. Pig manure was also mixed with wood shavings in ratios similar to that of cattle stomach waste and placed in three different chambers. The piles were left to compost for 21 days after which the experiment was repeated. During composting, each pile temperature and pH were measured daily. On each measurement day, the compost pile in each chamber was weighed and aerated by moving into an empty chamber. Compost samples were collected from each chamber twice a week for dry matter and volatile solid contents analyses. Results showed that composting pile temperatures increased with increasing levels of wood shavings added to manure. Pile temperature profiles followed a three-stage configuration; mesophilic, thermophilic, and a further mesophilic stage. The duration of each stage depended on the type of livestock manure and the quantity of wood shavings used for amendment. The duration of the thermophilic stage for composting piles amended with wood shavings more than doubled that of piles not amended with wood shavings. Aerated composting of livestock manure significantly reduced the mass with a greater reduction favoured for manure amended with wood shavings. There was no clear trend in pile volatile solid contents during composting. The pH profiles indicated an increasing trend throughout the composting duration

A Review of Cocoa Drying Technologies and the Effect on Bean Quality Parameters

Considering drying as a key farm-based, quality determining unit operation in the cocoa processing chain, this paper reviews recent studies in the drying methods and quality parameters of cocoa beans. Open sun, solar, oven, microwave, and freeze drying methods have been investigated at various levels in the drying of cocoa beans with objectives to improve the drying properties and final quality of cocoa beans. While an open sun dryer employs natural passive mechanisms, the solar drying methods can employ a combination of passive and active mechanisms. The oven, microwave, and freeze drying methods are fully active requiring electrical energy inputs. To improve drying rates in the open sun method, dryer materials and location of drying trays are the parameters optimized since the drying temperature depends on solar intensity. For solar dryers, materials, angles of elevation, heaters, and fans are manipulated to optimize energy absorption and drying parameters. For the oven and microwave methods, drying air properties are directly controlled by electronic systems. Moisture content, mouldiness, bean colour, pH, titratable acidity, fat content, and acetic acid concentration are the most widely evaluated bean quality parameters