MonroeCountyLandfill Gas-to-Energy/Food Waste Diversion Project
The Monroe County Landfill Gas-to-Energy/Food Waste Diversion Project is an environmentally proactive landfill gas management project designed to reduce the amount of methane gas released to the environment by the landfill, processspecific food waste outside the landfill to create biogas, andusethose gas products for constructive purposes. This projectwould reduce landfill odors from decomposing food waste, extend the life of the landfill, and develop a new revenue source (sale of electricity) to pay a capital cost loan. After the loan is repaid the revenue would be used to offset landfill costs, which means anyone using the landfill will share in the benefits.
This project would be a working partnership among Monroe County Solid Waste, federal facilities (Fort McCoy and the Tomah Veterans Administration Hospital), private business (VPP Group [Valley PrideProducts]and other food waste generators), and Alliant Energy.
The Monroe County Solid Waste Department is an enterprise business fund that does not receive any County tax dollars. Our current acreage has the ability to host three municipal solid waste landfills. Ridgeville I is full and closed. The current Ridgeville II is 50% full and will continue accepting waste until 2019. Preliminary testing of Ridgeville III has been completed, but it is not yet licensed for a future landfill site. If we are able to develop this new revenue source and divert food waste from the landfill, the current operation can continue providing landfill, recycling, and other requested services for more than 30 years. We understand that if we want to remain your disposal service provider long term, we must accomplish this using no County tax dollars and by not exposing MonroeCounty to any unacceptable financial risks.
The directive of the Solid Waste Committee was to keep the actual cost liability to the Solid Waste Department at or less than what it would cost to operate the landfill without the project. The projected cost of this project is $6,053,126, which includes $2,490,085 in landfill development costs that are necessary operational expenses without the project. An active gas extraction system will soon be required by the Wisconsin Department of Natural Resources (WDNR), and that $2.4 million represents the cost to install such a system and to fund thefuture development of Ridgeville II. Moving forward now with the full Gas-to-Energy/Food Waste Diversion Project would allow the County to reap the benefits of a $6million project for at least the 40 years the WDNR requires MonroeCounty to maintain the landfill and actively manage the landfill gas after the landfill is closed.
The proposed revenue bond for the total project is scheduled to be a 10-year loan that would be paid off in nine years; this period is within the active life of the current Ridgeville II landfill. The revenue bond only encumbers the landfill tipping fee revenue and has no negative effects on the borrowing power or credit rating of MonroeCounty.
Potential funding partners for this project are Focus on Energy, U.S. Department of Agriculture Rural Development, Alliant Energy, GundersenLutheranHospital, and Monroe County Solid Waste.
The Monroe County Landfill Gas-to-Energy/Food Waste Diversion Projecthas several components, each of which is described in detail on the following pages:
- Anaerobic digester system
- Transportation and pretreatment of digester materials
- Combining biogas energy sources to generate electricity
- Beneficial use of waste heat
- Landfill upgrade and construction activities
A conservative approach was used for the calculations listed in this report, including full list prices of equipment; “Cadillac” equipment alternatives; conservative biogas production estimates; engineering contingency of 15%; project cost contingency of 15%; and total rebuild of electrical generation equipment during the bond term.
Anaerobic Digester System
Large Wisconsin dairy farms have proven the technology behind anaerobic digester systems. These systems are used to process animal manure, converting it into biogas. The biogas fuels a generator to produce electricity that is used on the farm or sold to the electric utility. Continuing research at the University of Wisconsin-Madison has found that paunch manure (the undigested stomach contents of slaughtered animals) has twice the biogas-generating potential of dairy animal manure and that food waste has fivetimes the biogas potential.
The paunch manure for this system would come from the VPP Group, LLC, one of the nation’s largest federal contractors for ground beef. VPP has a processing plant 6 miles from the Monroe County Landfill. In the late 1990s, VPP processed approximately 1,500 head of cattle per day but cut production to 400 head of cattle per day because of the cost associated with waste treatment and disposal. Paunch manure is land spread on farm fields in a 75-mile radius of the plant. Each harvested animal produces approximately 100 pounds of paunch manure, which amounts to more than 10 million pounds of paunch manure produced at VPP each year, along with 2.8 million gallons of wastewater sludge with 3.5% volatile organic solids (this waste data does not include animal offal that is destined for rendering).
The core of the MonroeCounty project is a scalable and modular anaerobic digester. It is scalable to fit various system sizes; additional digester tanks may be added as the need arises. The modular configuration allows easier and faster construction and interconnections with the landfill gas system. The digester tanks will be connected to a shared computerized control system. It’s also a movable system, which means it can be relocated to a different site if necessary.
The proposed anaerobic digester has a short hydraulic retention time, allowing it to generate biogas from waste in only three to five days; other systems have hydraulic retention times of 18 to 30 days. This digester operates in the thermophilic temperature range, meaning the heat generated in the digester kills 99% of all pathogens in the paunch manure and food waste. This would help to protect MonroeCounty’s biosecurity when byproducts are sold to local farmers.
Because this use of the anaerobic digester is a new adaptation of existing technology, the University of Wisconsin-Madison Department of Biological Systems Engineering would like to use MonroeCounty’s system to research how to maximize biogas production. This research would focus on using paunch manure as the influent, using food waste as a co-substrate (a substrate is the base on which the microbes live), and creating customized microbe colonies responsible for digesting volatile organic solids that make biogas.
Preliminary estimates are that the biogas yield from paunch manure and food waste co-substrates may be up to four times the biogas production when compared to just manure. Biogas production models conservatively estimate that nearly 4.05 billion BTUs of biogas will be generated from the available 10million pounds of paunch manure when blended with a 10% ratio of food waste co-substrate. The BTUs generated by the MonroeCounty anaerobic digester will be enough to heat 360 Wisconsin homes per year.
The paunch manure acts as a buffer, stabilizing the process of digesting volatile food waste. The waste material ismechanically prescreened and sorted to remove foreign objects. The waste material is then ground and carefully blended as it goes into a mixing tank to be preheated before entering the digester. The system uses large tanks to digest liquid waste materials, producing biogas as well as waste heat,liquid fertilizer, and fibrous solids. The biogas from the digester will be combined with methane gas from the landfill and used as fuel to power electric generators 24 hours a day, seven days a week. The organic liquid fertilizer and the fibrous solids (animal bedding) can be sold to neighboring farmers, and the waste heat can be recovered to heat a greenhouse on the landfill property for year-round vegetable production.
This project has the potential of creating between 70 and 90 local jobs. VPP would have the option of adding a second shift of production staff to its meat processing plant. The greenhouse and other byproduct-related operations could also create many job opportunities.
Insulated equipment building (40’ x 80’) / $400,800Digester system equipment (including one 30,000-gallon tank) / $400,000
200-day liquid by-product storage lagoon / $100,000
Total for anaerobic digester system / $900,800
Transportation and Pretreatment of Digester Materials
Food waste and paunch manure are excellent sources of biogas, containing many types of beneficial microbes and enzymes. Beneficial use of these waste materials extends the useful life of the landfill, reduces landfill stability issues, and limits runoff problems associated with land spreading paunch manure.WDNR and Environmental Protection Agency (EPA) Region 5 leaders are excited about the possibility of using anaerobic digestion to alleviate concerns about the environmental hazards of spreading paunch manure on farm fields. These agencies also recognize the MonroeCounty project as a transferable model that could be used at other small landfills around the nation.
Adding the biogas created by the anaerobic digester to landfill methane gas creates the volume necessary to make a gas-to-energy project financially feasible. Specific equipment would be needed to collect, transport, and process these waste streams. We must be able to get the waste to the landfill when we need it to limit storage requirements and maintain a clean and sanitary operation. The digester must remain constantly full to keep consistent gas flows. Equipment would be needed to transport unacceptable waste to the landfill and to process acceptable waste materials to be digested.
One new roll-off truck (quad axle) / $125,000Four 30-yard and six 20-yard sealed dumpsters / $47,000
Thirty 2- and 4-yard poly dumpsters / $19,500
Waste acceptance/grinder/pumps/storage tanks / $133,500
One new 2-yard loader / $90,000
Total for food waste, paunch manure, and byproduct handling / $415,000
Combining Biogas Energy Sources to Generate Electricity
This project includes installing an active gas extraction system at the landfill. A gas extraction system uses a vacuum process to pump and capturemethane gas generated by the landfill. This system is required as part of any modern landfill operation and will be needed whetheror not the gas-to-energy project proceeds. The captured gas can be burned off with a flare or used as a fuel source. Using the captured gas to generate electricity will lower operational costs for the landfill and minimize the amount of fugitive landfill gas emitted to the atmosphere.
Landfill gas system (header pipes, blower, flare, and controls) / $350,000Electric utility three-phase upgrade and interconnections / $125,000
Engine generator and gas conditioning equipment / $1,100,000
Gas compression, storage, and fill station / $50,000
Total for landfill gas extraction system / $1,625,000
Beneficial Use of Waste Heat
Another component of the Monroe County Landfill Gas-to-Energy/Food Waste Diversion Project is to use waste heat from the digester and generator to heat a greenhouse, which would be used for 12month food production. The option of having fresh local food produced in the winter months has great community support in this part of Wisconsin. This community-run facility has the potential to create jobs for displaced workers, the elderly, and disabled community members. The produce would be made available to local schools, hospitals, and care facilities. The greenhouse would also serve as a living laboratory to provide community education on sustainable growing practices.
Total for greenhouse / $150,000Landfill Upgrade and Construction Activities
Planned landfill upgrade activities include installing a water line to purchase water from a neighboring landowner’s high-capacity well; installing a site security system; installing a modular leachate treatment system; and acquiringa used bulldozer.
Construction activities include final construction of the current landfill (Phase IV), procuring and hauling clay (this material is necessary for all liner and capping activities), and planting a 1.5-acre plantation of hybrid poplar trees as an alternative cap on the closed Ridgeville I landfill, which does not have a plastic-lined cap. Use of hybrid poplar trees for landfill capping is a “green” sustainable technology in which the poplars are engineered to absorb all rain and snow melt to keep moisture infiltration into the waste to a minimum.
Landfill upgradeWater line / $20,000
Site security system / $50,000
Used D-6 bulldozer / $85,000
Modular leachate treatment system / $200,000
Landfill construction
Site preparation/roads/parking lot / $75,000
Phase IV excavation (95,800 cubic yards @ $1.70/yard) / $162,860
Phase IV materials
Drainage layer sand – 6,500 yards @ $11.50/yard
¾-inch clean stone – 350 yards @ $26/yard
60 mil HDPE liner – 173,000 square feet @ $0.75/square foot
Geosynthetic clay liner – 173,000 square feet @ $0.63/square foot / $322,590
Additional items
Purchase of land or purchase and haul clay
70,000 cubic yards @ $9/yard / $630,000
Hybrid poplar plantation for landfill capping / $20,000
Total for landfill upgrade and construction / $1,565,450
TOTAL PROJECT / $4,656,250
Engineering and legal (15%) / $698,438
Contingency (15%) / $698,438
GRAND TOTAL / $6,053,126
Summary
The Monroe County Solid Waste Department, with the help of several interested potential partners,has been researching the possibility for this project for more than 16 months. The gas-to-energy feasibility study was completed by Ayres Associates of Eau Claire and was funded with a grant received from FocusonEnergy. Additional technical support was provided by SCS and RMT (two EPA contract consultants) and Ayres Associates professional staff from the firm’s Madison office.
The project has heavily weighted upfront capital costs but has reasonable payback potential made possible by many short-term renewable energy grants funded by federal stimulus dollars. Also considered in the nine-year payback timeline are costs associated with an additional gas technician employee, who will be needed to operate the landfill gas collection system even without this project.The future Ridgeville III landfill was not considered as part of this project. However, all equipment and buildings will be located to serve both the Ridgeville II and III landfills.
This project is environmentally safe, financially strong, and has the support of our neighbors surrounding the current landfill operation. Funds needed to pay back the Solid Waste Department’srevenue bond would come from the sale of electricity, calculated at $200,000per year, and from the $100,000per year that landfill operations is putting aside for future landfill development costs. For operating year 2009, the Department placed $149,000 into that account after all operating costs and general obligation bond payments were made. The economic situation in 2009 was very difficult for any business, and we are confident that improvements that were made to the operation in the last 18 months will continue to pay dividends in the future.
We will continue our conservative approach if the Monroe County Board allows us to continue into the Request for Proposal phase. We would include construction specifications, timelines, and performance standards to provide a comfort level to Board members, knowing that final payments will not be made until the predicted feasibility study performance standards have been met.
This project will solidify MonroeCounty as a leader in creating 24/7 renewable electrical energy using only waste materials. Just in the last couple of months there have been several technical articles in solid waste publications that discuss and support similar design concepts to those proposed for the Monroe County Landfill Gas-to-Energy/Food Waste Diversion Project. Copies of some of these articles will be available at the special meeting.
If you have any questions concerning this document, please call Solid Waste Manager Gail Frie at (608) 269-8783 or (608) 372-8783.