Date of Graduation

5-2013

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor

Thomas S. Soerens

Committee Member

Andrew N. Sharpley

Second Committee Member

Brian E. Haggard

Abstract

For every ten kilograms of biodiesel that is produced from the transesterification of vegetable oil, approximately 1 kg of glycerol is produced as a byproduct. Also known as glycerin, it is a chemical used in many products including cosmetics, foods, and desiccants. However, the crude glycerol created during biodiesel production is tainted with potassium hydroxide and methanol making it unsuitable for commercial use without costly refinement. With increase in production of biodiesel driven by rising fuel prices, the market has become glutted with glycerol and it is on the threshold of becoming a waste product. Common methods for disposing glycerol include incineration which releases carbon dioxide into the atmosphere. A more carbon neutral option is land application where glycerol can increase soil organic matter and may sequester carbon. Possible problems involved with land application include its effects on plants, microbes, and broader biological systems.

The objectives of this research project were to evaluate the effects of methanol-stripped crude glycerol on microbial, plant, soil, and animal systems in relation to soils and the potential for runoff contamination as well as incidental contact with insects during land application. Four methods were used: microbial activity in soil measured with respirometry, plant germination and growth, runoff testing by test plot application, and analysis of medium to large insect mortality.

Respirometry showed that microbial action is not inhibitory at tested concentrations between 0.03% and 10%. In plant tests, a concentration of 0.3% showed greater growth over control samples and concentrations above 1% showed inhibitory effects. In land application runoff studies, glycerol showed similar amounts of total organic carbon in runoff to controls and less than plots fertilized with NaNO3. Crickets treated with glycerol in a similar manner to field application showed higher mortality than control. In conclusion, the land application of glycerol does have an effect on the soil fauna in and on the soil upon which it is applied. In moderation, this effect is minimal and this research has demonstrated upper limits to its usage (<1% by weight). Finally, care should be taken to assure that no endangered insects are harmed if land applied.

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