Norman R. Scott

Biochemical methane potential and biodegradability of complex organic substrates.

The biomethane potential and biodegradability of an array of substrates with highly heterogeneous characteristics, including mono- and co-digestion samples with dairy manure, was determined using the biochemical methane potential (BMP) assay. In addition, the ability of two theoretical methods to estimate the biomethane potential of substrates and the influence of biodegradability was evaluated. The results of about 175 individual BMP assays indicate that substrates rich in lipids and easily-degradable carbohydrates yield the highest methane potential, while more recalcitrant substrates with a high lignocellulosic fraction have the lowest. Co-digestion of dairy manure with easily-degradable substrates increases the specific methane yields when compared to manure-only digestion. Additionally, biomethane potential of some co-digestion mixtures suggested synergistic activity. Evaluated theoretical methods consistently over-estimated experimentally-obtained methane yields when substrate biodegradability was not accounted. Upon correcting the results of theoretical methods with observed biodegradability data, an agreement greater than 90% was achieved.

Conventional mesophilic vs. thermophilic anaerobic digestion: A trade-off between performance and stability?

A long-term comparative study using continuously-stirred anaerobic digesters (CSADs) operated at mesophilic and thermophilic temperatures was conducted to evaluate the influence of the organic loading rate (OLR) and chemical composition on process performance and stability. Cow manure was co-digested with dog food, a model substrate to simulate a generic, multi-component food-like waste and to produce non-substrate specific, composition-based results. Cow manure and dog food were mixed at a lower - and an upper co-digestion ratio to produce a low-fiber, high-strength substrate, and a more recalcitrant, lower-strength substrate, respectively. Three increasing OLRs were evaluated by decreasing the CSADs hydraulic retention time (HRT) from 20 to 10 days. At longer HRTs and lower manure-to-dog food ratio, the thermophilic CSAD was not stable and eventually failed as a result of long-chain fatty acid (LCFA) accumulation/degradation, which was triggered by the compounded effects of temperature on reaction rates, mixing intensity, and physical state of LCFAs. At shorter HRTs and upper manure-to-dog food ratio, the thermophilic CSAD marginally outperformed the biomethane production rates and substrate stabilization of the mesophilic CSAD. The increased fiber content relative to lipids at upper manure-to-dog food ratios improved the stability and performance of the thermophilic process by decreasing the concentration of LCFAs in solution, likely adsorbed onto the manure fibers. Overall, results of this study show that stability of the thermophilic co-digestion process is highly dependent on the influent substrate composition, and particularly for this study, on the proportion of manure to lipids in the influent stream. In contrast, mesophilic co-digestion provided a more robust and stable process regardless of the influent composition, only with marginally lower biomethane production rates (i.e., 7%) for HRTs as short as 10 days (OLR = 3 g VS/L-d).

A Time Dependent Analysis of Greenhouse Thermal Environment

ABSTRACT RISING fuel prices are having a significant effect on further development of the greenhouse industry. This has directed research efforts along two paths: (a) improving the greenhouse structure to reduce energy losses, while maintaining a desirable growth environ-ment; and (b) developing alternate energy sources such as solar, wind, waste heat from power plants, and geo-thermal energy to meet greenhouse heating demand. Although a number of greenhouse thermal environ-ment models (analytical and numerical) are available at present, each model is restrictive in its applicability. A more general time-dependent analysis of greenhouse thermal environment is desirable to detect and control thermal stress on plants, to design so as to reduce heat-ing and cooling requirements, and to consider intermit-tent sources of heating and cooling such as solar and wind.

Steady-Periodic Analysis of Glasshouse Thermal Environment

ABSTRACT A mathematical model is developed to predict steady-periodic thermal behavior of glasshouses. The model is shown to predict temperatures of the internal air, plant canopy, and floor surface with reasonable accur-acy. The utility of the model is demonstrated through simulations predicting the effects of several potential glasshouse design modifications.

Effects of feathers on instrumental thermoregulatory behavior in chickens

Abstract Experiments with domestic fowl confirm that normally feathered chickens utilize species-specific behavior and autonomic responses to cold (at least to−5°C) rather than initiate an instrumental response. When the thermally insulative feathers are removed chickens readily utilize the instrumental response and are able to maintain physiological temperatures not significantly different from feathered birds. Simultaneous measurements of the mean radiant temperature of the chamber and body, skin, and hypothalamic temperatures suggested an approximately equal influence of these three temperatures in the determination of chamber mean radiant temperature.

The low-speed non-isothermal wall jet

Abstract This study uses similarity techniques to predict the form of the temperature profile development in a 2-dimensional non-isothermal wall jet. Experimental data completes and confirms the analysis. The temperature profile is characterized by its max. value and its thickness. An expression for the rate of convective heat transfer between a wall jet and a wall was obtained by experiment only. Comparing the dimensionless velocity and temperature profiles provides insight into the fluid dynamics of wall jet flow. Also discussed are implications of the slotted inlet ventilation system to heat losses by conduction through building walls.

Livestock buildings and equipment: A review☆

Abstract It is widely acknowledged that animal production is affected by “stress” imposed on the animal by environmental, nutritional, pathological and other factors. Morrison states that the environment in which the animal is maintained is the single most important factor affecting productivity. He defines environment to mean the air the animal breathes, the floor on which it stands, the number of its companions in a given area and the means by which it is confined. Livestock structures are widely utilized, especially in northern climates although, except for the young (new-born) animal, the primary reason is often not for environmental control. Rather, the structure is designed and built to permit efficient livestock handling, feeding and disease control, and to provide for security of animals. Not to be ignored are aspects of human comfort and reduction of drudgery in animal production systems. This paper attempts to provide a succinct review of livestock buildings and equipment, but it is impossible to provide an exhaustive analysis of developments in this area. The importance of the subject is reflected in the number of national and international symposiums or conferences which have been held in the last four years and the reader should refer to these for a more exhaustive review of specific developments.

Nanotechnology Environmental, Health, and Safety Issues

The environmental, health, and safety (EHS) of nanomaterials has been defined as “the collection of fields associated with the terms ‘environmental health, human health, animal health, and safety’ when used in the context of risk assessment and risk management” ([1], p. 2). In this chapter, the term “nano-EHS” is used for convenience to refer specifically to environmental, health, and safety research and related activities as they apply to nanoscale science, technology, and engineering. This chapter outlines the major advances in nano EHS over the last 10 years and the major challenges, developments, and achievements that we can expect over the next 10 years without providing comprehensive coverage or a review of all the important issues in this field.

Energy budget of the chicken foot

Abstract 1. 1.|A mathematical model predicts the energy loss from a chicken foot provided the following variables are known: body temperature, air temperature, wind velocity, blood flow to the foot, and the relative partitioning of blood flow via two distinct venous returns. 2. 2.|Chickens are capable of keeping their feet from freezing at temperatures as low as −30°C ambient, but at a high energy cost. 3. 3.|Chickens can modulate blood flow to their feet at thermoneutral temperatures enough to vary heat loss to environment by about one-fourth metabolic heat production.

Instantaneous Milk Flow Rate Patterns from Conventional Teat Cups

ABSTRACT AN ultrasonic flow meter was inserted in the short milk tube of a conventional two-chambered teat cup and instantaneous milk flow rates were measured during the course of machine milking. Flow rate characteristics were analysed with a pulsator ratio of 60% for pulsation frequencies of 1.0, 0.3, and 0.1 Hz, and vacuum levels of 50 and 35 kPa. A factorial experiment was conducted over six consecutive days on six cows with all treatment combinations. Data were sampled by computer and statistically analysed for treatment effects. Results showed that total flow rates per pulsation cycle were substantially larger than similar measurements made with a linerless milking unit. Large cyclic fluctuations in liner vacuum were observed, affecting liner wall movement, flow direction, and milk pulse phase with respect to pulsator operation. No significant differences between total pulse flow rates were calculated for the different pulsation frequencies or vacuum levels. Flow rates between cows were significantly different, with several animals showing distinct sensitivity to pulsation frequency. Rhythmic oscillation of the peak milk flow rate were measured for five of the six cows at both vacuum levels, but only at the more rapid pulsation frequency.