Curt Gooch

HEAT TRANSFER MODEL FOR PLUG-FLOW ANAEROBIC DIGESTERS

A comprehensive and fundamental mathematical model that predicts energy requirements to operate a plug-flow anaerobic digester at a specified temperature was developed. This information is supportive to designers as they determine heating requirements and energy use by the digester system. The model accounts for heat loss/gain by the influent and effluent flows, the digester floor, and the top-covering material and walls. In addition, the model accounts for frozen ground surrounding digester walls, thus increasing heat loss through the walls. Solar energy transmitted through the top-covering material is also accounted for in the model. Predicted heat was validated against experimental data, and the results agree reasonably well. The model can be used to estimate energy requirements to operate a plug-flow anaerobic digester on a daily, monthly, or yearly basis. Low energy was required to operate the digester in June through August, the lowest being in July, and more energy was required in November through March. Considerable energy could be saved if the effluent manure heat was used to pre-heat the influent manure.

Lifecycle Greenhouse Gas Analysis of an Anaerobic Codigestion Facility Processing Dairy Manure and Industrial Food Waste

Anaerobic codigestion (AcoD) can address food waste disposal and manure management issues while delivering clean, renewable energy. Quantifying greenhouse gas (GHG) emissions due to implementation of AcoD is important to achieve this goal. A lifecycle analysis was performed on the basis of data from an on-farm AcoD in New York, resulting in a 71% reduction in GHG, or net reduction of 37.5 kg CO2e/t influent relative to conventional treatment of manure and food waste. Displacement of grid electricity provided the largest reduction, followed by avoidance of alternative food waste disposal options and reduced impacts associated with storage of digestate vs undigested manure. These reductions offset digester emissions and the net increase in emissions associated with land application in the AcoD case relative to the reference case. Sensitivity analysis showed that using feedstock diverted from high impact disposal pathways, control of digester emissions, and managing digestate storage emissions were opportunities to improve the AcoD GHG benefits. Regional and parametrized emissions factors for the storage emissions and land application phases would reduce uncertainty.

Performance of Tunnel Ventilation for Freestall Dairy Facilities as Compared to Natural Ventilation with Supplemental Cooling Fans

Three pairs of naturally ventilated and tunnel-ventilated dairy barns were monitored during the summer of 2000 to compare the thermal environments developed by the two warm-season ventilation systems. Supplemental cooling fans were used within each of the naturally ventilated barns to direct airflow onto the cows. Ambient air temperatures during midsummer were cooler than normal in both New York and Ohio, but both states had near-normal cooling seasons. Both ventilation systems performed well during these temperate summer conditions with indoor thermal conditions closely tracking those outdoors. Tunnel ventilation provided only a slight advantage during the heat of the day in terms of moderating dry-bulb air temperature and THI. Each of the tunnel-ventilated barns provided a slightly cooler interior environment than its naturally ventilated counterpart when outdoor conditions were potentially stressful (THI greater than 70). The average advantages in terms of reduced differentials between indoor and outdoor environments were -0.4 C and -0.3 for air temperature and THI, respectively, for the tunnel-ventilated barns. Average air speeds within the cow spaces of the barn pairs were equal – no difference existed for the two summertime ventilation systems. Considerable spatial variation in air speed existed with both systems - at least a spread of 1 m/s in all barns. There was also no difference in temporal variation of airspeed in the cow spaces of the barns – both ventilation systems produced fluctuating airspeeds at cow level in one or more barn quadrants. Therefore, microclimate control should be an area of emphasis with both ventilation systems. Risk management approaches should be used to evaluate these systems on a regional basis using historical weather data. Improved designs are needed for tunnel ventilation to enable systems to maintain desired air velocities throughout the cow space and to better accommodate large barns..

Comparison of Five Anaerobic Digestion Systems on Dairy Farms

As environmental regulations controlling direct land application of livestock waste increase, farmers search for ways to cost-effectively handle manure from their farms. Farmers’ goals include efficient and effective means to remove the objectionable characteristics of their manure so that it may be recycled in an environmentally friendly manner. Anaerobic digestion is one way to control odors, liquefy manure and decrease pathogen loading, while reducing system costs by selling byproducts from the manure treatment system. Odor control allows digested effluent to be recycled in an environmentally friendly manner by applying it to cropland. Economic, nutrient, pathogen, energy production, and mass flows are under an ongoing quantification process for five integrated manure treatment systems in New York State. Each of these farms has recently installed an anaerobic digester as a method to control odor. The mass flow, nutrient flow, pathogen reduction, energy production and use, and economics of these systems are presented and compared. The systems vary by 1) type of digester: fixed film, plug flow, or mixed, 2) type of energy conversion: boiler, internal combustion, engine, or micro turbine, 3) digester feed: scraped manure from freestalls, separated tie stall manure, or manure with food waste added, and 4) farm size.

Evaluation of Laboratory Biochemical Methane Potentials as a Predictor of Anaerobic Dairy Manure Digester Biogas and Methane Production

Estimates of the quantity of biogas and methane produced by a dairy manure-based anaerobic digester are an important design parameter; they are used to size collection, transport, and biogas clean-up and utilization equipment prior to digester construction. They are also used to estimate potential return on the producers investment. Current methane production estimation methods include stoichiometric methane production calculations based on manure Chemical Oxygen Demand (COD) content, an estimate of digester COD removal, and data from the past performance of other dairy manure digesters. However, these methods can overestimate the actual biogas and methane production. This paper compares measured anaerobic digester biogas and methane production to estimated production based on laboratory biochemical methane potential (BMP) data developed from manure samples collected at six New York State dairy farms operating anaerobic digesters. Laboratory BMP tests of each digesters influent (manure and food wastes) were compared to on-farm monitored biogas and methane quantities calculated from biogas methane content. These comparisons were used to determine the ability of laboratory BMPs to predict on-farm production from dairy manure digesters. The results suggest that BMP assays could provide useful information to estimate methane production for dairy manure anaerobic systems. The results showed that using BMPs to estimate biogas production may not be accurate, but that predicting methane production with BMPs may be feasible. The linear regression results did not show a relationship that could be used for predicting biogas production from BMPs. However, a relationship and statistical similarities were found for predicting methane production from BMPs.

Greenhouse Gas Emission Reductions for Seven On-Farm Dairy Manure-based Anaerobic Digestion Systems – Final Results

Greenhouse gas (GHG) emission reduction calculations were performed following four different accounting methodologies for seven New York State on-farm dairy manure-based anaerobic digesters. The four methodologies followed were: Climate Action Registry (CAR), EPA Climate Leaders (EPA), Regional Greenhouse Gas Initiative (RGGI), and Chicago Climate Exchange (CCX). The Power Profiler tool was used to assess the GHG implications of the farms’ reduced use of traditional fossil fuel-based electricity usage, which was offset with renewable bio-methane derived electricity.

DESIGN PARAMETERS FOR HOT-WEATHER VENTILATION OF DAIRY HOUSING: A CRITICAL REVIEW

Good ventilation is critical for housed dairy cattle during hot weather. Three ventilation parameters – rate of air exchange, air distribution, and air velocity at animal level – need to be considered in assessing ventilation. This paper describes each parameter, discusses relevant research, and points out deficiencies in the existing information pool. Research is needed to establish the minimum air-exchange rate during hot weather for modern dairy cattle. Recommended rates are likely being attained in modern naturally ventilated and tunnel-ventilated barns for most situations. Exceptions would include naturally ventilated barns that are poorly sited and/or oriented, very wide and/or densely stocked, or located in a region that experiences a significant number of summer days with calm or low-wind conditions; as well as tunnel-ventilated barns that are longer or more densely stocked than is warranted based on fan and inlet capacity. Proper air distribution presents a challenge for natural ventilation in terms of site planning and for tunnel ventilation in terms of maintaining airflow through occupied areas. Achieving desired air velocity at cow level in the presence of adequate air exchange appears to be the key design challenge. A variety of approaches are being used to move air within occupied areas to enhance evaporative cooling and maintain thermal comfort. While these approaches have been shown to produce desirable interior airflow, further study is needed to determine the most effective and economically advantageous methods.

TUNNEL VENTILATION FOR FREESTALL FACILITIES – DESIGN, ENVIRONMENTAL CONDITIONS, COW BEHAVIOR, AND ECONOMICS

Tunnel ventilation, the practice of installing large exhaust fans with high flow rates in oneendwall of a barn to draw air longitudinally down the barn’s length from an inlet located in theopposite end wall, has recently received favorable usage by many dairy producers in the UnitedStates. The success of tunnel ventilation varies depending on several key variables. Severalrecently published research reports compare and contrast tunnel ventilation to natural ventilation.Tunnel barns were shown to provide a slight improvement in some aspects of the cow’senvironment during potentially stressful conditions. Overall many barns that employ tunnelventilation provide a better environment for housed cows than if they were naturally ventilated.Economically, an analysis of all associated cost for employing tunnel ventilation shows thatpayback, measured in sustained milk production, is achievable, especially for longer barns. Thispaper aggregates our research work and field observations to provide a single reference that canbe used to obtain up–to-date knowledge of tunnel ventilation for dairy freestall barns.

Mechanical Solid-Liquid Manure Separation: Performance Evaluation on Four New York State Dairy Farms – A Preliminary Report

Five mechanical solid-liquid manure separators manufactured by three different companies and located on four production dairy farms in New York State were sampled monthly from May 2001 to December 2004 (not every separator was sampled continuously throughout this period). Samples were analyzed in an EPA approved commercial laboratory for total solids, total volatile solids, total phosphorus, ortho phosphorus, total Kjeldahl nitrogen, ammonia nitrogen, and potassium. Organic nitrogen was determined by subtraction. The efficiency of capture of each effluent stream was calculated for each constituent analyzed. All separators, regardless of farm specific affects on separation performance, captured no more than 25 percent of the nitrogen and phosphorus in the solid effluent stream. Implications on each farm’s CAFO plan were analyzed and the results are presented.

Pump Performance Tests as a Method of Determining Influent Mass Flows to Dairy Farm Anaerobic Digesters

A new on-farm anaerobic digester (AD) monitoring protocol, recently released by the Association of State Energy Research Technology and Transfer Institutions (ASERTTI) is being used to assess seven anaerobic digesters on dairy farms in New York State. A key component of the ASERTTI protocol is to perform a mass balance of the AD system. Mass balance data is needed to determine system performance values such as: degree of manure stabilization, biogas produced per unit of influent, and subsequent electrical power produced per unit of influent. The optimal location in the system to obtain AD influent mass flow data is at the AD influent pump. However, pumps used to pump manure generally lack performance data, making it difficult to quantify mass flow without knowing the performance characteristics of the influent pump.