BCR - Landfill Gas: An Alternative Fuel
Such was the case in Montgomery, Ala., where the city was faced with compliance to the New Source Performance Standards of the Clean Air Act, as related to landfill gas emissions. In early 1996, the city began considering a landfill gas recovery project to meet that obligation.
The landfill site is made up of “cells” that are lined with an impermeable material, such as clay. Soil is then used to surround and contain the waste. Once the mound of waste has reached a certain height, it is covered with at least two feet of soil. As this solid waste decays and decomposes, it generates a gas called biogas—a mixture of methane and carbon dioxide (CO2), with trace amounts of hydrogen and oxygen. This gas is an inexpensive source of energy—energy that can be successfully used to fire brick.
Slowing “Global Warming”Atmospheric methane has been blamed as a contributor to what environmental science terms the “greenhouse effect” of global warming—the effect that certain variable constituents of earth’s lower atmosphere have on surface temperatures. These gases—water vapor, CO2 and methane—keep ground temperatures at a global average of about 60°F.
Environmental scientists are concerned that changes in the variable contents of the atmosphere, particularly changes caused by human activities such as landfills, could cause the earth’s surface to warm to a dangerous level. Variations in the atmosphere’s CO2 content have been said to play a major role in past climatic changes, and there has been a global increase in atmospheric CO2 in recent decades.
Capturing landfill gases at their source and reusing them in other applications is one way to help solve the problem. But while a large number of U.S. landfills are currently equipped to collect biogas, it is not a simple operation. After learning about the gas-producing potential of the Montgomery landfill, DTE Biomass Energy, a subsidiary of Detroit Edison, contacted the city in April 1996. Biomass explained that it would be better to have a third party developer take the overall responsibility for the project because of its cost and operating complexity.
Federal tax credits were available under Section 29 of the Internal Revenue Service Code. However, a number of actions had to be carried out by December 31, 1996, in order to take advantage of these tax credits. First, an RFP (request for proposal) had to be drafted and issued. Next, the city had to analyze bidder responses and award the contract. A gas rights agreement then had to be negotiated between the city and the prevailing developer, and another RFP, this one concerning the well field construction, had to be issued by the developer. Finally, a binding contract for construction of the landfill well field had to be executed—all before the December 31 deadline.
Montgomery Finds a BuyerThe city of Montgomery issued an RFP for installation and operation of a landfill gas recovery project in September 1996. Biomass forwarded a response to the RFP on October 7, 1996, won the award, and subsequently executed a gas rights agreement with the city. Under the agreement, the city avoided a substantial investment in a landfill gas collection system and the long-term operating and maintenance expenses associated with it. In return, Biomass received the rights to all gas generated at the site and would receive the federal tax credits, in addition to the price of the fuel, when the gas was sold as a fuel.
As early as 1994, Jenkins Brick, located in Montgomery and the only large consumer of gas in the area, had begun considering the use of landfill gases to fire its products. So when Biomass contacted Jenkins in 1996 with an offer for the landfill gas, the company readily agreed.
In September 1998, Jenkins commissioned Harrop Industries to convert its kiln to accommodate landfill gas. A new gas train was run parallel to the natural gas train and tied together with a three-way valve at each zone on each side of the kiln. Eight valves were used in all, one each for both preheats and both fire zones on each side.
Additionally, all 30 of the burners in the preheat section were replaced with Hauck RSVG burners due to the increased flow of fuel required to fire the product. Flow meters that read both natural and landfill gas were added to all burners. No changes were made to the combustion air. To transport the gas from the landfill to the plant, Jenkins Brick constructed a 1.5 mile, 10-in. diameter high-density polyethylene pipeline between the two locations.
A Successful SwitchIn January 1999, Jenkins Brick switched its fuel supply from natural gas to landfill gas one zone at a time on each side of the first kiln. It took one week to convert the entire kiln. Since that time, with the exception of a short period in August, the company has burned landfill gas continually.
Methane, or marsh gas, is the main component (usually about 88% to 95%) of natural gas. It is nonpoisonous and burns with a pale blue flame. The other main component of landfill gas, CO2, is also found in natural gas but in very small amounts (0.5% to 2%). CO2 detracts from the heating value of gas and, as a result, the BTU content of landfill gas is only about half that of natural gas.
The natural gas used by Jenkins Brick has a BTU content of 1030 BTUs per cubic foot of gas, while the landfill gas BTU content is only about 555 BTUs per cubic foot. If the landfill gas BTU content drops below 500, natural gas must be blended in.
In June 1999, Jenkins Brick began construction of a second kiln and installed a booster blower station to boost the pressure from the landfill to the kilns. An important part of the booster station is a natural gas blending station, which automatically blends natural gas into the landfill gas line to augment the landfill gas if needed. The kiln is expected to begin production in March 2000.
Jenkins Brick still flashes its product using natural gas, since market demands have not permitted the company to experiment with flashing with landfill gas. However, the company plans to equip the new kiln with landfill gas flashing capabilities. The first kiln’s flash zone was modified in mid-December 1999 to handle landfill gas as well.
In total, plant manager Buddy Hibbard estimates that the upgrades needed to accommodate the landfill gas—including the pipeline stretching between the landfill and the plant—cost around $1 million. But the payback will be tremendous. “Because of the arrangement that we have with Biomass, the use of the landfill gas should pay for all of our upgrades within four or five years once our second kiln is brought on-line,” says Buddy.
And there are the environmental benefits as well. On July 29, 1999, Jenkins Brick was awarded the Governor’s Conservation Achievement Award for Air Conservator of the Year from the Alabama Wildlife Federation—a notable achievement in an era in which brick and ceramic manufacturers generally receive more condemnation than praise from environmental agencies.