[GreenYes] health and environmental concerns with anaerobic digestion and biogas

["Alan Muller" <amuller@no.address>]

Dear folks:

Some enthusiasm is developing in Minnesota for anaerobic digestion of
various wastes.  I share that enthusiasm somewhat but am not finding
much about the health/environmental implications.  Some of my
concerns are in the email below.  Can anybody point me towards some
answers?

Thanks,

am

        

**********************
[heading deleted]

AD seems to have a lot of potential for managing various waste
streams.  But possible health and environmental hazards should be
considered in advance using the precautionary
principle.

Exposure to nuisances and health hazards could come from several sources
including (1) transporting feedstocks to the AD facility (diesel and gas
engine exhaust, road dust, traffic accidents, etc), (2) fugitive
emissions from the digester itself, (3) exposure to the biogas produced,
and its products of combustion, and (4) exposures to the digestate
and wastewater produced, including exposures from post-processing of
these streams.

However, not much attention is being given so far to the issues of toxic
constituents in biogas and its products of combustion, and the possible
health implications.   these are the focus of the rest of this
brief, non-comprehensive note. 

I am not saying these issues are necessarily "deal killers,"
for AD generally, but I am saying the same level of scrutiny needs to be
applied to AD as has been applied to, say, garbage incineration.

For example, wood burning ("biomass") has been widely promoted
as a "green" activity.  People have assumed or pretended
that wood is a clean fuel.  It isn't.   The permit
documents for a proposed wood burner in Minneapolis ("Midtown"
project by the Green Institute then Kandiyohi Development Partners)
showed the emissions would be around a million pounds per year. 
Neither the promoters nor the MPCA presented this information to the
community in a meaningful way.  When the community found out the
truth, the project went away.  The Virginia and Hibbing biomass
burners have apparently been unable to comply with their permits and have
been fined.  I am concerned that the MPCA's ultimate response may be
to loosed up the permits.

What are the health implications of feeding AD gas into the natural gas
distribution system?  People living near a digester might get a high
proportion of AD gas, and some of it would be burned in gas stoves and
unvented heaters, such that the products of combustion would be released
directly into their homes and they would be breathing them
directly.

None of the "feasibility studies" of AD that I've so far found
have addressed this issue.

We know that households using gas stoves, as opposed to electric stoves,
already experience measurable health effects such as increased asthma
attacks.

What harmful constituents might be in digester gas, in addition to what
is already in "natural gas?"

We know that "landfill gas," a biogas produced by anaerobic
digestion in dumps and often misrepresented as a "green" fuel,
contains hundreds of different contaminants, many of them toxic and/or
carcinogenic.  According to an Energy Information Administration
site, landfill gas contains an average of 2,700 ppmv of
"non-methane-organic compounds" and 132 ppmv of halides. (

http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/chap10.html
 ).  

According to the Agency for Toxic Substances and Disease Registry
(ATSDR): "NMOCs most commonly found in landfills include
acrylonitrile, benzene, 1,1-dichloroethane, 1,2-cis dichloroethylene,
dichloromethane, carbonyl sulfide, ethyl-benzene, hexane, methyl ethyl
ketone, tetrachloroethylene, toluene, trichloroethylene, vinyl chloride,
and xylenes." (

http://www.atsdr.cdc.gov/HAC/landfill/html/ch2.html#t2_1).

In 1991 EPA identified health effects from landfill gas including
"leukemia, aplastic anemia, multiple myeloma, cytogenic changes,
damage to liver, lung, kidney, central nervous system, possible
embryotoxicity, brain, liver & lung cancer, possible
teratogenicity" (

http://www.epa.gov/ttn/atw/landfill/laurv1.pdf , Table 2.1)

In the same report, EPA "focused on nine carcinogenic constituents
known to be present in MSW landfill air emissions, (benzene, carbon
tetrachloride, chloroform, ethylene dichloride, methylene chloride,
perchloroethylene, trichloroethylene, vinyl chloride, and vinylidene
chloride ....)"

We know that landfill gas produces "hazardous air pollutants"
when burned, including dioxins.

We know that landfill gas and sewage sludge digester gas contains
siloxanes, compounds that when burned produce finely divided silicon
dioxide (sand).  This tends to eat up the innards of engines and
turbines burning digester gas, in a way similar to what would happen if
you drove a car on dirt roads without an air filter element in
place.  (Some interesting images and discussion here: 
http://www.appliedfiltertechnology.com/Userfiles/Docs/AFT_CWEA_2006_Paper.pdf
)

Silicon dioxide is harmful when inhaled, and known to cause asthma,
bronchitis, silicosis, and possibly lung cancer.   Is AD gas a
credible exposure route if siloxane removal is not attended to?  I
haven't looked into it enough to know, but I think it is important to
know.

Now, people will point out correctly that AD gas is not the same as
"landfill gas" and I agree.  I expect that AD gas would
tend to be somewhat less contaminated than landfill gas, because the
digester feed would hopefully be more controlled than dumping into a
landfill.  it might be reasonable to consider LFG as a sort of
"worst case" baseline.

But "the devil is in the details."  Incinerators tend to
end up taking a wider range of stuff than originally stated, and this
might also be the case for a digester.

Another question is how the permitting of a digester would be handled,
and where the authority and responsibility would lie.  How rigorous
would the permitting be, and would the impacts of digester gas at the
points of consumption be fully considered?

Probably answers to many of my concerns exist in the literature. 
I'm sure there are other issues I haven't thought of.  Since
LHP&L has been looking into AD for some time, perhaps you could point
me towards some answers?  

I hope that all those interested in AD can work together.

Regards,


Alan Muller



--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "GreenYes" group. 
 To post to this group, send email to GreenYes@no.address 
 To unsubscribe from this group, send email to GreenYes+unsubscribe@no.address 
 For more options, visit this group at http://groups.google.com/group/GreenYes?hl=en 
 -~----------~----~----~----~------~----~------~--~---