Cows are typically raised in concentrated feedlots which generate too much manure to be locally useful as fertilizer, so alternative methods of utilization/disposal are needed. Meanwhile, nearby cement kilns face problems associated with high fuel costs and increasing scrutiny with respect to emissions of air pollutants. This project will develop a technology to utilize cow manure as an environmentally friendly substitute for cement kiln fuels. OBJECTIVES: The general objective of the Phase I project will be to assess the technical and economic feasibility of burning cow manure in cement kilns. Specific technical objectives of the Phase I work include: 1) Determination of manure composition; 2) Assessment of technical feasibility; and 3) Assessment of economic feasibility and commercialization potential. The Phase I effort is designed to address the following questions: a) How will feeding of cow manure impact cement quality and gaseous emissions from cement kilns? b) How should the manure be introduced to the kiln? c) Is gasification and/or oxygen enhancement necessary? d) What is the optimum location in the kiln to feed manure? and e) What are the fuel and equipment costs? APPROACH: The objectives of the Phase I project will be met in three tasks. TASK 1. MANURE COMPOSITION - The composition of local dairy manure will be determined, including heating value, ultimate and proximate analysis, and ash content (amount of silica, calcium, sodium, potassium, iron, and magnesium). TASK 2. TECHNICAL FEASIBILITY ASSESSMENT. Task 2a. Cement Clinker Quality - Mixes representing typical cement raw materials mixed with ash from cow manure will be ground and homogenized and then will be processed into clinker by heating to the appropriate temperature in a bench scale furnace. The clinker will be ground and mixed with gypsum and the resulting mixture's properties will be compared to the ASTM Standard Specification for Portland Cement. Task 2b. Energy and Mass Balance - System mass and energy balances will be performed to determine the optimum feedrate and feed location(s) for manure in the cement making process - and potential impacts on clinker temperature, energy efficiency, clinker production rate, draft fan flue gas handling requirements, coal displacement, etc. Both direct injection and gasification of the cow manure prior to injection will be examined. Task 2c, Assessment of Emissions Impacts - NOx emissions impacts will be estimated based on manure nitrogen content, projected gas temperature profile from the point of manure injection, and on NOx reduction estimates based on review of selective noncatalytic NOx reduction literature. CO2 emission impacts will be estimated from the mass and energy balances based on the predicted reduction in coal feedrate due to the displacement of coal with cow manure. Note that, although cow manure also contains carbon that forms CO2 when it burns, the CO2 from combustion of biomass such as cow manure does not count from a global warming perspective because it is CO2 that would be released to the atmosphere anyway as the biomass decays as a part of the normal biocycle. Emissions impacts for SO2 and toxic metals will be estimated based on the composition of coal and cow manure assuming that the system removal efficiency for each remains constant. TASK 3. ECONOMIC FEASIBILITY ASSESSMENT AND COMMERCIALIZATION STUDIES. Task 3a. Selection of a Candidate Cement Kiln - A candidate cement kiln will be selected based on location, interest, and suitability for manure burning; and design information on that kiln will be collected. Task 3b. Preliminary Engineering Design - Preliminary designs will be prepared of the manure storage, feeding, gasifying, and combustion equipment needed for the integration of the use of manure in cement kilns, using the candidate facility as an example application. Task 3c. Economics - Installed capital equipment costs for the manure handling and feeding equipment will be determined. Operating and maintenance (O&M) costs will be estimated. Total annualized costs will be assessed from both capital and O&M costs. These costs will be compared with alternative cement kiln fuels and with alternative methods of manure utilization/disposal.
