Landfill Gas to Energy Plant Design

DTE BioMass Energy – Statesville, NC, Denton, TX, Bellefontaine, OH
Howard R. Green (HR Green) was retained by DTE Biomass Energy to assist with the planning, design and construction of three landfill gas to energy plants in three states in 2008. An initial study effort  included a cost benefit analysis between a modularized component plant or a full building housing the entire process. The modular system as pictured to the right, in addition to being more cost effective in this case brings the added benefit of being more portable for DTE BioMass Energy. The facility designs are based on the Caterpillar 3520 engine generator platforms each producing 1.6 MegaWatts (MW) each at full capacity, a separate fuel skid and a containerized switch gear arrangement.

Green Construction LLC, a sister company to HR Green  was the general contractor on all three plants. Two of the facilities generating 3.2 MW (2 units) and 1.6 MW (1 unit) were commissioned in 2008.  The remaining 4.8 MW (3 units) plant was commissioned in February 2009 and was on line in March 2009.

Waste Management Renewable Energy –  Five Oaks Landfill,
Taylorville, IL
HR Green designed a 3.2 MW power plant for Waste Management Renewable Energy at their Five Oaks Landfill in Taylorville Illinois. Each of four Caterpillar 3516 engine generator units is rated at 800 KW and the electrical energy generated is interconnected through a switchyard to the local electric utility grid through an Ameren substation and 69kV transmission line adjacent to the facility. In addition to the electric power generation, waste heat from the engine water jacket is recovered through four heat exchangers. The hot water is then piped to an adjacent greenhouse complex where it provides enough heated water to sustain greenhouse needs year round.

Waste Management Renewable Energy – Timberline Trail Landfill, Bruce, WI
In conjunction to the design expansion at the Waste Management Renewable Energy facility for Timberline landfill, HR Green designed a heat recovery loop that recovered waste heat from the engine’s water jacket through a heat exchanger. This is used to thaw ice from the hauling company’s drop-off containers. The hot water is then piped to the adjacent shop building where it provides heat to the shop area as well.

Sunshine Gas Producers – Sylmar, CA
HR Green was retained to design a landfill gas to energy facility utilizing five (5) Solar Turbines’ Mercury 50s at the Sunshine Canyon Landfill in Sylmar, California.  The five ultra-low emissions producing Mercury 50s are each capable of producing 4.6 MW for a combined plant total of 23 MW, of which a maximum of 20 MW will be provided to the grid and the balance utilized to power the plant’s auxiliary loads. Besides some very difficult site/access road improvements that must be accounted for, HR Green’s work includes the design of the landfill gas compression system, associated chillers, aftercoolers/heat exchangers, siloxane removal treatment system, regen flare, and all associated electrical systems and controls needed to convert the gas to electricity. The site is very restrictive and has required multiple layout iterations to find just the right combination of equipment that is robust/reliable, has the lowest auxiliary power needs, and can fit into a very small space. To minimize construction complexity, the specifications have focused on a number of pre-manufactured system components commonly used in landfill gas-to-energy projects. These specifications will require that the various system components be provided/delivered as “skid packages,” allowing for construction to focus on site/civil work and the required interconnecting gas piping, electrical lines and associated facilities.

Gas Collection System Design

Bluestem Solid Waste Agency –
Site #1 Gas Collection for Beneficial Use –  Cedar Rapids, IA
Bluestem Solid Waste Agency (Bluestem) Site No. 1 occupies 95 acres of which approximately 76 acres have been land filled. A private developer, in partnership with Bluestem and the local utility company, pursued a project with the intent to supply landfill gas to a nearby electrical generating station. The gas would be used as supplement fuel in the utility’s coal fired boilers. Bluestem retained HR Green to coordinate the design and installation of the collection system.

The landfill had no leachate collection system and excessive leachate in the waste had become a potential environmental problem as well as an impediment to landfill gas collection. To operate as a dual or co-collection system, the collection wells were designed to extract both leachate and gas simultaneously. The design of the co-collection system included quantifying the amount and location of extractable leachate, and developing a radius of influence for the spacing of landfill gas extraction wells and a header system to transport the products to control locations.

The system included 18 extraction wells, extending from the ground surface to the base of the refuse. Each well consisted of an eight-inch diameter HDPE slotted well casing surrounded by a 36” diameter gravel pack. A header system connects each of the wells and conveys the landfill gas to a compressor and gas dryer prior to transmission to the utility via a buried line from the fill area to the generating station in south Cedar Rapids. The collected leachate and gas condensate are discharged to the City of Cedar Rapids sewer system via a direct connection.