Garbage In, Power Out: How Trash Can Power Ethanol Plants

Deck: 

A win-win situation for the local government, utilities, and industry.

Fortnightly Magazine - February 2007

Ethanol plants either are operating, under construction, or planned for several areas in the Midwest. These same areas also have municipal solid waste (MSW) produced daily in an existing landfill. In addition, these areas have a need for establishing or extending a landfill.

As an alternative to the existing concept of a landfill, plasma-arc technology has been applied to the treatment of MSW. Known as plasma-arc gasification for the treatment of MSW, this recent development would eliminate or minimize the need for a landfill.

Plasma-arc gasification can generate an abundant amount of energy and electricity, or steam. Nearby ethanol plants using corn require electricity and a large amount of steam for fermentation, distillation, and drying operations.

In this article, we offer a preliminary economic analysis of a joint process operation for a typical ethanol plant using corn, with a capacity of 50 million gallons/year with a plasma-arc plant processing MSW. A simplified schematic for such a hybrid process (combined plasma-arc plant and ethanol plant) is shown below.

Plasma arc gasification for the treatment of municipal solid waste (MSW) is a very high-temperature pyrolysis type of process (7,200 oF to 12,600 oF) whereby the organics of waste solids are converted to a synthesis gas, and the inorganic and minerals of the waste solids produce a rock-like byproduct.1,4,6,8,9

The synthesis gas6,7,9 is predominantly carbon monoxide (CO) and hydrogen (H2). The inorganic material and minerals in the waste solids (MSW) are converted to a vitrified slag typically of metals and silica glass. This vitrified slag basically is non-leaching and exceeds EPA standards. Metals can be recovered from the slag and the slag can be used to produce other byproducts1,4,6,8,9 such as rock wool, floor tiles, roof tiles, insulation, and landscaping blocks. One of the simpler recyclable uses of the slag is as a road material[1] but at much lower economic value. The synthesis type of gas can be used to produce electricity and the rock-like byproduct as a material for road construction, since it is environmentally acceptable. The fuel/synthesis gas produces byproducts hydrochloric acid (HCl) and sulfur via the gas cleanup step8.

In this article, the economics are performed on a process for converting MSW by a plasma-arc gasification (a pyrolysis process) to a synthesis gas and a vitrified slag. The synthesis gas will be used to generate electricity—steam—and the slag will be used as a road material.

The bottom line: This process for treating MSW eliminates the need for a landfill and can be used to process existing landfill MSW sites.

MSW can be processed using the plasma arc gasification1,4 process and simply represented in Figure 1.

Note, 1 ton of MSW uses 500 kWh of the total electricity produced by the process, but recent technological advances have reduced this usage to 200 kWh/ton of MSW.10 The vitrified slag or rock residue produced is 400 pounds.

The above-simplified representation of the MSW pyrolysis step can be shown as a simplified process flow diagram8 but the fuel/gas could be used for generation of electricity, steam and/or for synthesis of chemicals (see Fig.2).

A simplified process-flow diagram14 is shown here for a typical ethanol plant converting the raw material, corn, into ethanol: (see Diagram 1).

The capital cost for a plasma arc gasification process to produce electricity and a vitrified slag can be deduced from the following figure (see Figure 3) of capital cost versus capacity.5

Thus, with the information presented so far, a preliminary evaluation and economics can be deduced for a plasma-arc plant using MSW12 with sufficient capacity to supply both electricity and steam for an adjacent ethanol plant producing 50 million gallons of ethanol per year from corn.11

Consequently, we evaluate the following economic cases: (see Table 1).

Basis

A plasma arc gasification facility operates at 706 tons/day capacity1,2,3 for treatment of MSW with a “total” capital investment of $97,344,000.5 This plasma plant capacity supplies sufficient energy as electricity and steam to an ethanol plant for the production of 50 million gallons of ethanol per year.11

Capital cost of the ethanol plant is $65 million.11 Capital financed for both plants would be at 5.75 percent interest for 20 years, making two payments per year. The plasma-arc facility would generate 30,000,000 kWh/year4 of electrical energy (renewable energy) for sale to the ethanol plant at 4.5 cents/ kWh. A 2.0 cents/kWh revenue from green tags associated with renewable energy electrical production was used in the financial analysis for the plasma arc plant.

In addition, the plasma arc plant would supply 1,421,405,000 lbs/year steam for sale to the ethanol plant at a sale price of $5.50/1,000 lbs steam. The byproduct rock material would be sold as a road construction material at $15/ton.1 On the ethanol facility, 18,518,500 bushels/year of corn are purchased at $3.75/bushel.11 A byproduct, dried distillers grain with solubles (DDGS), is produced at 166,667 tons/year and sold as a cattle feed for $90/ton.11

Cost considerations for operations and maintenance, a capital budget reserve, process water, and sewer have been considered in the economic evaluation. More than 100 jobs would be created by a combined plasma and ethanol facility. The combined facility is self-sufficient in electrical and steam energy requirements, since this energy is produced internally from a renewable raw material, MSW.

Economic Cases

From these “initial” economic analyses, one likely approach to a business plan is for a cooperative effort among a local utility, local industry, and local governmental entities. Thus, the local government participates in the MSW treatment part of the plasma-arc facility while the local utility participates in the electrical and steam energy (renewable energy) producing part of the facility. A local industrial/business entity could own/operate the ethanol facility. Thus, the local government remains in the MSW business, while the utility or industry stays in the electrical, steam, or ethanol energy businesses. This appears to be a win-win situation for the local government, utility, and local industry.

Case 1 presents the preliminary economics of a plasma-arc gasification facility combined with an ethanol plant (such as for the Linn County/Cedar Rapids, Iowa, area) for a facility processing 706 tons/day of MSW. The cooperative venture results in a “tipping fee” for the MSW of $35/ton and a selling price of ethanol at $1.80 per gallon. A tipping fee of $35/ton of MSW is typical for Linn County, Iowa2,3.

Net revenue before taxes from combined facility operation = [revenue-expenditures] = $16.95 million per year.

Both the plasma arc plant and the ethanol plant contribute to positive net revenue.

Case 2 presents an economic evaluation similar to the previous case, but the selling price of ethanol is $2.5541/ gallon.13

The net revenue before taxes from combined facility operation = [revenue-expenditures] = $54.655 million per year. As before, both the plasma arc plant and the ethanol plant contribute to positive net revenue.

Future Progress

A logical approach is to take the initial economics presented for a particular area and periodically update the analysis through a cooperative effort among governmental bodies and industrial entities, so both parties will have a fully transparent evolvement and trust in the final economic analysis. Thus, this factual, transparent, updated economic analysis therefore will determine the final approach taken by both government and industry for that particular area investigated to determine if plasma arc gasification is an economically and environmentally attractive alternative to a landfill when integrated with an ethanol plant.

A utility or business company in partnership with a local government likely would be the most economical combination, and it would have the most positive benefit to the environment and financial reward to the local area. The economics presented here are preliminary; such evaluations are site specific, and plasma processing of MSW is an emerging technology.

With some diligence, a viable business plan can be developed from the consideration of the many factors influencing the economics associated with a specific site selection and surrounding community.

 

Endnotes:

1. Dr. Louis J. Circeo, Engineering & Environmental Applications of Plasma Arc Technology, Technological Forum, Kirkwood Training and Outreach Services center, Marion, Iowa, Nov. 22, 2005

 

2. “Expert touts plasma torch,” The Gazette, November 22, 2005

3. “Plasma arc technology may help Linn garbage woes,” The Gazette, Nov. 20, 2005

4. Circeo, Louis, J., “Engineering & Environmental Applications of Plasma Arc Technology,” Presentation, Georgia Tech Research Institute, Atlanta, GA, 2005

5. Circeo, Louis, J. and Smith, Michael S., “Plasma Processing of MSW at Coal-Fired Power Plants,” Presentation, Health and Environmental Systems Laboratory, Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, GA; 2005

6. Vera, Rod, “Organic Waste, Gasification and Cogeneration,” Presentation, Trinity Plasma Tech

nology, Technologies International Corp., Trinity Consultants Inc., 2005

7. Lee, C.C., “Plasma Systems,” Standard Handbook of Hazardous Waste Treatment and Disposal, McGraw-Hill Book Co., New York, (1989), p. 8.169

8. Recovered Energy, Inc., Pocatello, Idaho, www.recoveredenergy.com, “Process Flow Diagram,” MSW into energy and useable by-products

9. “Summary Report: Evaluation of Alternative Solid Waste Processing Technologies,” Prepared for: City of Los Angeles, Department of Public Works, Bureau of Sanitation, 419 S. Spring Street, Suite 900, Los Angeles, CA 90013; Prepared by: URS Corporation, 915 Wilshire Boulevard, Suite 700, Los Angeles, CA 90017, September 2005.

10. Dr. Louis J. Circeo, Private Communication, April 4, 2006 and Dec. 22, 2006.

11. Ulrich, Ken, Private Communication, ICM Inc., Dec. 21, 2006.

12. Young, Gary C., “Zapping MSW with Plasma Arc,” Pollution Engineering, November 2006

13. American Coalition for Ethanol, www.ethanol.org, averages provided by Axis Petroleum, State Average Ethanol Rack Prices, Iowa, Tuesday, Dec. 19, 2006.

14. Iowa Corn, Organization, www.iowacorn.org and Iowa Corn Promotion Board/Iowa Corn Growers Association, December 2006.