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[greenyes] Landfills Greenhouse Gas Emissions
Patty asks: "Do landfills contribute CO2 and methane in somewhat similar
amounts, or is methane the major gas coming from landfills?"

The answer is yes. The bulk of landfill gases are methane and carbon 
dioxide, averaging about 47.5% and 47%, respectively.  The other 5.5% is, by 
volume, mostly nitrogen, 68.5%, and also includes oxygen, 14.8%, 
hydrocarbons, 5.6%, hydrogen, 1.9%, and trace constituents (hydrogen 
sulfide, sulfur dioxide, benzene, toluene, vinyl chloride, methylene 
chloride, perchlorethylene, trichlorethylene and carbonyl sulfide), 9.3%. 
Source: Robinson, The Solid Waste Handbook, at p. 314 Table 11.16.

Three things to draw from this.


First, although there are large volumes of CO2, as well as the methane, even 
though CO2 is a greenhouse gas, its emission from a landfill does not add to 
global warming on a net basis, as contrasted with methane, which otherwise, 
were it not for our practice of burying organics in oxygen starved 
conditions in the ground, would not exist.  Therefore, only the methane part 
of landfill gases is a net addition to climate change.


Second, I indicated that these percentage values are averages only, and that 
the precise number will vary by landfill and over time. There is a very 
important point that arises from that fact.  Energy recovery of the methane 
in landfill gases is put forward as a very good thing, because it displaces 
energy production, with all its emissions elsewhere in power plants and 
boilers, much of which burns dirty coal.

However, those same energy recovery systems require high Btu content in the 
gas, most comfortably when the gas is especially methane rich over 48%.  To 
maximize the efficiency of the energy recovery systems the landfill 
operators will typically manage the site in a way that, in the process of 
increasing the methane fraction, lessens the efficiency of gas collection. 
This happens because the extracted gas is about half moisture (with 100% 
saturation, at 40 C (104 F), the condensate is 51% by weight of the weight 
of the gas), and, since lots of water is a necessary ingredient to produce 
methane, the waste load is dried out to the point where methane production 
declines below the level needed to generate power.  In order to avoid this, 
in those landfills managed for energy (instead of exclusively to minimize 
gas releases), the operator will ramp back gas collection in dried out 
fields until moisture levels recover sufficient for strong methanogenisis.

Interestingly, the regulatory agencies remain steadfast in their refusal to 
determine how significant a loss in methane recovery this practice causes, 
and also will not even organize data collection so that others can use 
statistical techniques to infer how substantial the problem is.

Instead, they entire engines of government remains committed to the "good 
news" story about energy recovery from landfills for political reasons, 
completely impervious to technical considerations.  (At the same time, 
landfills managed for energy production may take greater care in properly 
installing covers and piping, and it is the net of these two offsetting 
forces that is the relevant measure of concern.)


Third, those trace compounds included in landfill gases (e.g. benzene and 
toluene) may be very small in volume (<0.5%), but they are extremely toxic 
and are suspected of being associated with causing injury to the surrounding 
population, such as quadrupling of leukemia rates in pregnant mothers. 
Source: State of New York Department of Health, Investigation of Cancer 
Incidence and Residence Near 38 Landfills With Soil Gas Migration 
Conditions, New York State, 1980-1989 (1998). Unfortunately, to run 
statistically significant epidemological studies requires major funding, and 
EPA has shown no interest in resolving the many studies that raise concerns. 
(The problem is that, without major funding, associations between exposure 
and incidence are tracked by using zip codes or other gross indices of 
proximity to a landfill, even though these gross measures include 
substantial numbers of people not in any exposure trajectory, and that 
washes out detecting impacts.)


Peter Anderson, President
4513 Vernon Blvd. Suite 15
Madison, WI 53705-4964
Ph: (608) 231-1100
Fax: (608) 233-0011
Cell: (608) 698-1314
eMail: anderson@no.address


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