Carl S. Hansen

Anaerobic Digestion and Bio-gas

A clear understanding of the start up phase for an anaerobic digester is essential to continual digester success. Samples were taken 2-3 times a week over the period of nine months during the start up phase of a hog manure digester in Benson Utah. These samples focused on the influent, recirculation pipe, and effluent sections of the in-vessel digester. Lab analysis on the samples pH, chemical oxygen demand, ammonia content, temperature, volatile fatty acids and solids including; total, suspended, volatile, volatile suspended solid, total and soluble. In addition, biogas quantity and quality (% methane, ammonia, and hydrogen sulphide) were recorded. The compiled data with charts show the nature of the digester during start up. These graphs detailing the start up period of an induced blanket reactor (IBR) are important both during digester start up phase, and in diagnosing possible digester problems in the future. These results led to improved sampling techniques, and contributed directly to improvements in digester design. Furthermore, the effects of design changes were monitored to justify their implementation. Although influent manure properties were not consistent, the nine-month study period allowed for a considerable improvement in digester analysis.

Inexpensive biogas Conditioning for small Digesters

There are a growing number of anaerobic digesters being used on animal feeding operations both for pollution control and for energy production. Most anaerobic digester projects use the biogas produced to generate electricity. However, the generation of electricity alone does not produce enough income in order to create an economic rate of return for the construction and operation of the anaerobic digester system (See: Analysis of Energy Production Costs from Anaerobic Digestion NRCS, web site October, 2007). Because of the present high cost of fuels, revenues form anaerobic digestion (AD) could increase two fold if a farmer or other captive fleet operators could use biogas as a fuel for their automobiles, farm equipment, and fleet vehicles. AD could become economically feasible and would encourage the installation of these pollution preventing digester systems. However, impurities in the biogas have been a major obstacle to using biogas as a vehicle fuel. Traditional methods of biogas cleaning have been expensive, messy to maintain or unreliable.

Anaerobic Hydrogen Production using Agricultural and Food Processing Wastes

Despite its clean and green nature when utilized in fuel cells and other devices, most hydrogen is currently produced from non-renewable sources such as natural gas, oil, and coal. Anaerobic digestion provides a better alternative to manufacturing hydrogen than fossil fuels. Anaerobic digesters can produce hydrogen from inexpensive and renewable energy sources such as organic wastes. The objectives of this research were to perform anaerobic fermentations to produce hydrogen from substrates such as cheese processing wastes and animal manure. The quality and quantity of the hydrogen produced has been demonstrated and the chemical oxygen demand and solids information analyzed. Three anaerobic batch reactors were constructed for the experiments to monitor pH, temperature, and agitation. Cheese whey and animal manure proved to be excellent substrates for hydrogen production producing as much as 1.57 liters of hydrogen per liter substrate. COD and total solids removal were also observed for each of the trials performed. Anaerobic hydrogen production utilizing food processing and animal wastes supplies a clean, inexpensive energy and also treats environmentally harmful wastes. Although these results are promising, further research is necessary to develop a continuous anaerobic digestion process to produce a constant hydrogen supply.

Using Biogas as a Fuel for Trucks

Anaerobic digestion on the farm has been promoted for decades as an effective method to reduce pollution and produce fuel. However, because of the high cost and problems associated with anaerobic digestion of animal manures, plus the lack of return on the investment, there are relatively few digesters being installed in the United States. Most of the biogas produced by anaerobic digestion is used to generate electricity. Grid interconnect agreements require lengthy negotiations and are difficult to finalize. Usually the electrical rates received are below the cost of production because equipment for electrical generation is expensive to install and expensive to maintain. By showing that biogas can be used as a fuel in trucks and/or tractors, anaerobic digestion would be more attractive.

Utilization of the nutrients from an anaerobic digester treating animal waste

A multi-disciplinary team of Utah State University researchers is working to develop a sustainable biofuels research program that integrates via a business model, basic science, fundamental, and applied engineering research, pilot scale research facility, and commercial demonstrations of biofuel technologies. Biofuels are combustible gases or liquids (such as methane, alcohols, biodiesel, or hydrogen) that are the product of biological processes. The biological process is either a fermentation of biomass or the photosynthetic conversion of sunlight into the combustible gas or liquid product. Biofuels are attractive because they are renewable as long as there is sunlight and/or biomass (animal waste, food waste, garbage or any other organic material) and because they produce fuels that can be used in existing or slightly modified engines, boilers, and turbines. Further, biofuels are net CO2 neutral, consuming as much CO2 as is produced. Utah State University is focused on this approach to meeting our future energy needs. This presentation will report the first six months progress on this multi-year initiative. We will report results of pilot studies indicating efficaciousness of using the nutrients in effluent from an induced blanket reactor (IBR) anaerobic digester, treating animal waste, to grow microalgae for biodiesel.