September 22, 2008 | General

Not So Green Energy

BioCycle September 2008, Vol. 49, No. 9, p. 53

AT A TIME when both environmental and energy policies take their place in presidential election debates, too many organics continue to end up in landfills. While many communities are working hard to get organics out of landfills, Michigan and Missouri are considering lifting their landfill disposal bans for yard trimmings.
State bans on disposing of leaves, grass clippings and/or brush were adopted in the late 1980s and early 1990s, primarily in response to a disposal capacity concern. There are 21 states with some sort of ban in place (see “The State of Garbage In America,” April 2006).
Often driven by local landfill owners, arguments in favor of overturning these bans focus on the benefits of landfill gas capture and its use as a “green” energy source. But a closer examination of the details of landfill gas generation, collection and utilization suggests very different conclusions.
According to the U.S. Environmental Protection Agency (EPA), there are 425 landfill gas (LFG) recovery projects nationwide, generating about 10 million megawatt (MW) hours/year. EPA projects that another 560 landfills are candidates for similar projects. But even if all of those candidate landfills were to generate electricity from LFG, a total of less than 23.2 million MW hours could be generated annually. According to the U.S. Department of Energy (DOE), electricity consumption in the U.S. in 2006 was nearly 4.1 billion MW hours – therefore, LFG-generated electricity could only fulfill 0.57 percent of America’s electricity needs.
In the case of Michigan, the impact of adding yard trimmings to this small energy potential is minor. According to publicly available reports, allowing the current major landfills in Michigan with LFG-to-energy systems to add yard trimmings to the waste stream would increase LFG power output no more than 15.3 percent. According to the same documents, LFG energy potential as a percentage of total energy demand is less than one percent. That means the actual increase in energy availability would result in approximately one tenth of one percent of statewide production.
On the other hand, composting – currently utilized to manage these organics waste streams – is a growth industry with established best management practices (BMPs). According to the Institute for Local Self-Reliance, composting creates four jobs for every one job created through landfilling or incineration. So while the inclusion of yard trimmings in landfills will have an insignificant impact on the amount of electricity available, it will have a detrimental effect on the composting industry by diverting important feedstock and revenue from locally owned and operated businesses. This will undoubtedly result in lost jobs.
In addition, it should be noted that the operational concerns raised about composting sites by advocates of landfilling organics are misleading. Like any business, there have been site operators that haven’t performed to industry standards. However, there are plenty of well-run composting sites throughout the country and numerous steps have been taken to develop professional associations and BMPs that have significantly limited operational problems encountered.
Further, composting not only reduces greenhouse gas emissions by avoiding methane generation, it also provides significant environmental benefits. The use of compost decreases fertilizer and pesticide use, improves soil structure, reduces irrigation needs, decreases the effects of high salinity, increases soil productivity, limits erosion and helps store carbon in soil.
Finally, state and local governments have spent considerable effort establishing yard trimmings collection programs designed to comply with the existing regulations, and promoting to residents the importance of composting and earth-friendly ways to manage our waste. Allowing landfills to accept yard clippings confounds these programs and the message that we have shared with residents and taxpayers for years.
Also of vital importance is the impact on local government, businesses and consumers that will result from the accelerated depletion of landfill space and the consequential increase in prices. The availability of low cost landfilling in many parts of the country is no secret. Landfills are often in fierce competition for waste volumes. Should organics landfill bans be overturned or other exemptions created, it is likely that landfills will be anxious to qualify to accept yard clippings.
Data estimates from the Michigan Department of Environmental Quality (MDEQ) indicate that an additional 500,000 to 1.2 million tons of yard trimmings could become available for landfill disposal if the ban is lifted. This will hasten the depletion of existing landfill capacity and cause an increase in prices. Not surprisingly, this quantity of waste would yield additional revenues for landfill owners in the state of Michigan between $7.5 and $18.0 million. Could this be the real motivation for the proposed changes?
One of the most important factors that argues strongly against disposal of organics in landfills is the impact of organics management on global climate change. It seems like yard waste organics might not matter in the GHG emission calculation because they are all going to become carbon dioxide in any case. For the most part this is true, however, there are carbon-based gasses into which organics can transform that are considerably worse than CO2, including methane (CH4). Methane has been scientifically shown to be 23 times more effective in retaining heat in our atmosphere than carbon dioxide, creating quite an incentive to prevent uncontrolled production of this gas.
The significant difference (23:1) between the impact of methane and carbon dioxide on the potential for warming of the earth lays at the core of the discussion about the costs and benefits of banning organics from landfills. Landfills place heavily compacted wastes in deep holes in the ground where oxygen seldom penetrates – creating circumstances that lead to the transformation of organic material to methane. Original EPA estimates suggested that collection of methane in well-designed systems could reach 75 percent, but later empirical evidence and a full analysis of the landfilling system now estimates that only 20 percent of the total generated methane can be collected. The rest makes its way to the surface by other routes and is emitted to the atmosphere or is never captured at all because the gas collection systems are installed late or ineffectively.
A quick analysis of the situation shows that approximately 95 percent collection efficiency of methane in landfills would need to occur if that organics management option were to equal the GHG outcome of aerobic decomposition (like composting or land application). At a collection efficiency of 75 percent, which was erroneously claimed, the outcome would actually be four times worse in a landfill setting. In the circumstance that collection efficiencies are closer to 20 percent, the outcome is 15 times worse.
In short, although it is a good idea for all landfills to capture as much generated methane as possible, and make electricity from it when feasible and safe. However, this can be effectively done without adding more organics to the waste stream. And, action on this front will not have a significant impact on the generation of electrical power. The contributions of LFG to the electricity needs of our country is less than one percent. It seems then, that there are few legitimate technical reasons for expanding the role of landfills in organics management.
Why then do these proposals persist and get serious attention at the state legislative level? “The answer to that
is easy,” says Michael Csapo, General Manager of the Resource Recovery and Recycling Authority of Southwestern Oakland County, Michigan (RRRASOC). “They want the additional tip fee revenues.”
JD Lindeberg, P.E. and LEED AP, is Principal and CFO of Resource Recycling Systems Inc. in Ann Arbor, Michigan (

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