Health risks with regards to biogas systems - Clostridium botulinum in substrates and fermentation residues of biogas plants? - Botulism disease


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Re: Pathogen destruction in biogas plant vs ABR (Anaerobic Baffled Reactor)

Other than clostridium botulinum, another pathogenic clostridia of concern in biogas is clostridium perfringens.

High concentration of Clostridium perfringens found at 45 days reveals a risk to use the digested slurry on the arable land. Some Clostridium spp. may cause infection in animals e.g. blackleg (Clostridium chauveoi), malignant (Clostridium septicum and Clostridium
sordelli edema), black disease (Clostridium novyi), and enterotoxemia (three types of Clostridium perfringens).

Pathogen Reduction in Small-Scale Biogas Plants
in a Tropical Region - Bench-Scale Experiments
, 2008

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Re: High-throughput microbial gene detection seems like the future? - and technology used to identify dysbiosis

It is not the biogas technology who increases the risk for botulism, it is canned food.
(see also:

Clostridium botulinum is also a food borne illness and results from the ingestion of pre-formed toxin in food. Botulinum toxin can be found in foods that have not been properly handled or canned and is often present in canned vegetables, meat, and seafood products. Home canned products, especially low acid food products, are attributed to most cases of food borne botulism. Foods commonly associated with botulism are canned asparagus, green beans, garlic in oil, corn, soups, ripe olives, tuna fish, sausage, luncheon meats, fermented meats, salad dressings, and smoked fish. Spores have also been found on the surfaces of vegetables and fruits. During the canning process, foods undergo a hot fill process and oxygen is removed, leaving the food in an anaerobic environment. Certain foods, such as meat, are able to bind oxygen to create an anaerobic environment that allows C. botulinum to grow. Home canning processes for low acid foods are extremely risky because the time and temperature food are heated are often inadequate. On a commercial scale, improperly handled food products have also contributed to outbreaks.

As this is valid for canned food, the same is valid for ensiling feed.

The essential steps in the ensiling process are to maintain anaerobic conditions, discourage the activities of undesirable microorganisms such as clostridia, enterobacteria and yeasts, and stimulate the growth of lactic acid bacteria. When lactic acid bacteria produce lactic acid and acidify the forage, the development of other undesirable microorganisms is decreased or inhibited. Each piece of dead animal in the silage will promote C. botulinum to grow. Nowadays, often animal cadavers are co-ensiled due to full mechanised agriculture silage baling on the field, or in high mechanised silage process as used in industrial dairy farms for energy crop biogas plant. There the risk comes from. As (bale) silage is now on the way to be introduced worldwide, botulism kills cows also in Cambodia (see also the 2012 doctor thesis: Nutrient Utilisation in Growing
Cambodian Cattle - Effect of Different Feed Sources and Feed Conservation Techniques, from Keo Sath, Faculty of Veterinary Medicine and Animal Science, Department of Animal Nutrition and Management, Uppsala).

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Re: High-throughput microbial gene detection seems like the future? - and technology used to identify dysbiosis

Considering how the biogas/anaerobic digestion industry is poised for dramatic growth in the USA and everywhere, I'd like to know more about government regulation regarding disposal and treatment of residual waste. Perhaps we should add probiotics to the waste in order to balance the skewed ecosystem.

Global Biogas Market to Nearly Double in Size to $33 Billion by 2022

Forecast Report on Global Biodiesel Market and Biogas Industry

Anaerobic digestion pipeline valued at £650m, says Green Investment Bank

Waste to energy power plants could generate an eighth of U.S. power says Cleveland's Quasar Energy

"The company's newest business model -- locating Quasar's technology inside a municipal wastewater treatment plant -- is beginning to smell like money. A lot of money."

Is this really the best use of our organic resources? We're shattering microbiomes akin to deforestation.

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Re: High-throughput microbial gene detection seems like the future? - and technology used to identify dysbiosis

Thanks for pointing that thread out, Elisabeth. The biogas controversy continues in Germany and people should take notice everywhere. It's not just a problem of botulism, however, but all strains of clostridia where spores are apparently not killed in anaerobic digestion. What other resistant organisms are we growing based on this technology? By the way, it's interesting that high clostridia counts are known in the imbalanced guts of autistic children, an insidious gut-brain connection.

Here's the latest PCR study where it's concluded biogas plants:

" . . . could present a biohazard risk of clostridia for humans and animals."

"The increasing number of biogas plants in Germany presents a danger of spreading pathogenic clostridia to arable land."
Detection of pathogenic clostridia in biogas plant wastes July, 2014

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Re: High-throughput microbial gene detection seems like the future? - and technology used to identify dysbiosis

Hi Keith,

As you brought of botulism, a disease which some people fear could be spread via clostridium botulinum in digestate from biogas plants (your example of dairy farms in Germany), I would like to point you to an existing thread on the forum where this was discussed:

Further discussions on this link - which is suspected by some but also rejected by many others - should be discussed there. I am not an expert in biogas systems but the detailed arguments by biogas specialist Heinz-Peter Mang in response to a statement by Prof. Ralf Otterpohl in 2012 put my mind at ease on this issue.

Please see the other thread (link above) if you are interested in this issue.
Heinz-Peter really went through quite some trouble to list all the relevant literature and studies from Germany on this topic. Well worth reading.

Dr. Elisabeth von Muench
Freelance consultant on environmental and climate projects
Located in Ulm, Germany
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Re: High-throughput microbial gene detection seems like the future? - and technology used to identify dysbiosis

Note by moderator: the following 3 posts were originally in this thread but have now been moved to this thread.
Original thread was:


Anaerobic digestion (AD) is another area studied using new molecular techniques, helping us understand in fine detail how we are shifting flora balance with this waste disposal technology. My fear is both AD and WWTP damage ecosystems on the microbial level akin to deforestation. Why not concentrate on more natural systems, i.e., aerobic composting? AD is poised for explosive growth in the global marketplace. Sexy biogas technology generates electricity in disregard of long-term collateral damage.

In this swine manure AD study, first of its type, clostridia was not surprisingly found dominant. Is this why anaerobic digestion of waste is associated with chronic botulism in the environment?
Multiple approaches to characterize the microbial community in a thermophilic anaerobic digester running on swine manure: A case study

I'd like to read the full paper of this new AD study which states anaerobic digestion sludge samples
"were different from other microbial communities from activated sludge, human faeces, ocean and soil."
How were they different and what are the ramifications?
Metagenomic analysis of sludge from full-scale anaerobic digesters operated in municipal wastewater treatment plants.

Do operators of AD plants understand these issues? I've read many dairy farms in Germany were destroyed by chronic botulism in the environment when residual waste was allowed contact with livestock. This is a very controversial, hot topic.

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Health risks with regards to biogas systems - Clostridium botulinum in substrates and fermentation residues of biogas plants? - Botulism disease

There was recently an interesting posting by Ralf Otterpohl about health risks from biogas systems in the old ecosanres discussion forum. It is (also) a reaction to earlier postings, including a very detailed one by Heinz-Peter Mang. As it would be a shame that these postings would get lost in a closed e-mail list, I have copied them here to bring them out in the open (by EvM in my role as moderator).

You see 4 posts here in inverse chronological order, i.e. the most recent post comes first (I have added some formatting to make it easier to follow the discussion):


Posted by: "Ralf Otterpohl"
Fri May 18, 2012 1:22 am (PDT)

Dear All,

It can be ok to apply biogas systems with wet waste low protein biomass,
stuff that requires treatment anyway and would often consume energy for
aerobic treatment otherwise.

However, converting biomass (even the waste) to energy on a large scale
will deprive soils of organic matter, this is a clear and simple
connection from the farming textbooks. Living soil with LOTS of organic
matter is a key element for water and food security and by far more
important that energy Living soil needs to be fed and is a high value
energy producer, it does not reqire energy intensive synthethis
fertilisers and pesticiedes, too.

One of the most terrible environmental desasters of the last decades is
the over subsidised construction of food-to-biogas plants that has been
massively pushed in Germany. Farms for food production,also organic
farms are partly pushed out of business by rising prices for land. Soil
quality is detoriating fast, pesticide concentrations rising and many
milk farms face bancrupcy through the dramatic rise in botulism cases. Of
70 food-to-biogas plants recently checked by Hygiene Institute of
University Leipzig all had chlostridium perifrenges and around 30%
chlostiridium botulinum. Now mesophilic plants with protein are ideal
for multiplying botulinum forming bacteria.

Many self help meetings by farmers who are at risk of losing their farms by botulism have come up at the same time, the link is likely and frigthening. Botulinum can also
enter groundwater and has been found there, too. These plants should not
be built any more, operated thermophilic and instead of corn/maize they
should switch to plant alternatives that are there. With or wihtout
botulism, it does not make any sense. All of Germanys arable land could
supply 2% of its energy demand, so forget about it. Misguided
politicians are driven by lobbyists who make big profits, society is the

The energy yield from biomass (appropriate waste excluded, there
treatment is the issue)
is so ridicolously low that compared to food
production it does not make any sense. Including soil degradation it is
risky business, increasing hunger. Woodgas stoves and co-generators with
charcoal production for soil improvement is a very viable alternative.
Otherwise it is simple to get enegy from other sources (direct solar,
wind, small hydropower, efficiency) with less damage.

Myself, I am working more and more towards composting, humus building,
reforestation. Still also with waste to biogas :)


Earlier posting from Heinz-Peter:
> *From:* heinzpetermang
> *To:* This email address is being protected from spambots. You need JavaScript enabled to view it.
> *Sent:* Sunday, 6 February 2011 7:48 AM
> *Subject:* EcoSanRes: Re: biogas from ecosan, here botox
> Dear all,
> I followed the discussion with great interest, and I am really
> surprised about a non-proofed sentence from Prof. Ralph Otterpohl as:
> "This makes biogas plants a clear risk technology for a very very
> severe illness."

> This discussion has already happened in the Biogas Scene between 2004
> and 2009, and again inside GIZ initiated by Prof. Helge Boehnel in
> 2006, and again in 2008.
> Prof. Monika Krueger (University of Leipzig) and Prof. Helge Boehnel
> (University of Goettingen) are publishing since 10 years in various
> articles the opinion that fermentation residues from biogas plants
> present a significant hazard potential; poisoning of animals and
> humans may be caused by the toxins of C. perfringens and C. botulinum.
> In particular, C. botulinum is known for the formation of toxic poison
> under certain circumstances (botulism). Both scientists recommend the
> permanent control of the digestate for the presence of pathogenic
> organisms, especially since these also are generated by the
> multiplication of bacteria during fermentation and storage of the
> digestate.
> But C. botulinum is part of the soil degradation process bacteria.
> During each anaerobic degradation process of organic material, amino
> acids are degraded pairwise by Clostridium botulinum (BOTOX) using the
> "Stickland reaction" in which one amino acid serves as a hydrogen
> donor and the other as acceptor, resulting in acetate, ammonia, and
> CO2. During the splitting of cysteine, hydrogen sulphide is released.
> 1988: Already in September 1988, in the "Design Manual for Constructed
> Wetlands and Aquatic Plant Systems for Municipal Wastewater Treatment"
> of the U.S. Environmental Protection Agency it is written that
> "Wildlife may be affected by wetlands systems because anaerobic muds
> may contain the causative organism of avian botulism (Clostridium
> botulinum). Control of this wildlife pathogen can be accomplished
> largely by multiple dispersion points for free water surface (FWS)
> wetlands. This pathogen is not a problem for wild fowl in subsurface
> flow system (SFS) wetlands or aquatic plant systems."
> Does this make FWS wetlands a clear risk technology for a very very
> severe illness?

> 2002: In the UK-Risk Assessment: Use of Composting and Biogas
> Treatment to Dispose of Catering Waste Containing Meat, of the
> Department for Environment, Food and Rural Affairs, from May 2002, is
> recommended that a warning label is put on bio-waste compost sold for
> home use to ensure infants under 6 months are kept away, even they
> found that the "estimated" spore loading in compost is lower than for
> some soils in The Netherlands."
> Does this make composting a clear risk technology for a very very
> severe illness?

> 2006: In the IWAS Journal Water Health 04 (2006) 277-288,
> an article about
> "Watershed issues associated with Clostridium botulinum: A literature
> review", from Sharon C. Long and Tiffany Tauscher, reviewed aspects of
> naturally occurring C. botulinum in light of concerns for source water
> watersheds. C. botulinum has been detected in raw water storage areas,
> trout farms, fish and environmental samples from coastal area, dust,
> wetland sediments and other sources. A number of incidents of
> detection of the different types of C. botulinum in varying
> environments around the globe are analysed. Soils and dusts have often
> been cited as a significant reservoir of C. botulinum. Serious
> outbreaks of botulism have occurred in beef cattle that were fed
> chicken litter. In The Netherlands, botulism has occurred in cattle
> that were fed wet brewer's grains. In another case C. botulinum type
> spores were found in bales of round bale barley haylage that were fed
> to cattle. Haylage harvested green and encased in black plastic bags
> to facilitate lacto-fermentation, was presumably contaminated by the
> botulinum toxin when fermentation failed to produce enough acid to
> lower the pH to 4.5, the pH below which C. botulinum growth is
> inhibited. Thus, hay fermentation presents a potential problem for
> farmers who use round hay balers to produce haylage.
> Does this make haylage in round plastic packed bales a clear risk
> technology for a very very severe illness?

> 2009: In the « Evaluation du programme latrine Medair à Madagascar »,
> August 2009, WASTE NL and Practica Foundation, C. botulinum have been
> identified in the faeces of urine diversion toilets as part of the
> GRAM-positive bacteria package.
> Does this make UDDTs a clear risk technology for a very very severe
> illness?

> When canning food it is important to completely control the botulinum
> bacteria, because if these bacteria survive and grow inside a sealed
> jar of food, they can produce the poisonous toxin. Even tasting of
> food containing this toxin can be fatal. Whether food should be
> processed in a pressure canner or boiling water canner depends on the
> acidity of the food. Acidity may be natural, as in most fruits, or
> added. Low-acid (pH>4.6) canned foods contain too little acidity to
> prevent the growth of the botulinum bacteria, while acid foods
> (pH<4.6) contain enough acid to block their growth or destroy them
> more rapidly when heated. Fruits are acid foods, but vegetables are
> not. Therefore they should be acidified with lemon juice, citric acid
> or vinegar. If low acid foods are not acidified, the processing in
> boiling water is not recommended.
> Does this make canned fruits a clear risk technology for a very very
> severe illness?

> Already based on German research data collected before November 2005
> it could be stated that no cross-contamination of botulism from
> infected animals through digestate to animal fodder was detected in
> Germany.
Also the German Federal Institute for Risk Assessment (BfR)
> published in a statement the fact that the occurrence of symptoms
> caused 'visceral botulism' by the interaction of 4 important factors
> is determined:
> 1. Clostridiums are increased in the environment by over-fertilization
> with manure or poultry litter
> 2. Increased incidence of the disease in high-yielding cattle with
> unstable immune system
> 3. Poor nutrition of high-yielding cattle (rarely ruminant fair, too
> low fibre content)
> 4. Poor feeding hygiene (poor hygienic quality of silage, etc.)
> In addition, the department "cattle diseases" of the German Veterinary
> Society (DVG) published in a statement already 2006 the fact that C.
> botulinum is almost everywhere common, and could be occasionally
> demonstrated in the gastrointestinal tract of completely healthy
> cattle. The clinical pictures of the "visceral Botulismus" could also
> be caused by many other factors than by C. botulinum, namely
> unfavourable feeding and housing conditions, metabolic disorders or
> other infectious diseases.

> Industrially processed, vacuum-packaged, hotsmoked salmanoids have
> been responsible for a cluster of outbreaks in northern Europe. The
> consumers' demand for reduced use of sodium salts and the vacuum
> packaging used to prolong shelf lives have apparently created
> high-risk botulinogenic products that are largely dependent on
> refrigeration for safety.
> It appears that C. botulinum spores naturally occur in soils and
> sediments with specific strains predominating in different
> geographical regions. However, considering current source water
> protection practices in the U.S., threats of waterborne botulism
> outbreaks among human populations is low. Threats of forage botulism
> can be minimized by education of farmers regarding hay and feed
> management practices. Threats to source waters from wildlife outbreaks
> can be minimized by proper detection and carcass management when avian
> and fish outbreaks occur. Conventional treatment processes have been
> demonstrated to be adequately effective at removing Clostridium spores
> from drinking water.
> IRDCurrents No.13 and 14 from July 1997, edited by the Department of
> Rural Development Studies of the Swedish University of Agricultural
> Sciences in UPPSALA, and financed by Sida (Swedish International
> Development Cooperation Agency) published by René Sansoucy on page 8:
> "Biodigestion has positive public health aspects, particularly where
> toilets are coupled with the biodigester, and the anaerobic conditions
> kill pathogenic organisms as well as digesting toxins, for example,
> botulinum toxin."
> Research work about "Biotic and abiotic components from effluents of
> anaerobic plants with a potential risks for water protection areas",
> published in February 2010 by Dr. W. Philipp, Institut für Umwelt- und
> Tierhygiene, Universität Hohenheim, Stuttgart shows that anaerobic
> digestion does not increase, but reduce usually accomplished by good
> anaerobic process management. This finding is not, however directly
> for C. botulinum, because C. perfringens has been used for the test,
> and C. botulinum may be different.
> The Federal Agricultural Research Centre under the leadership of Prof.
> Weiland conducted appropriate investigations in June 2007 on C.
> botulinum in substrates and fermentation residues of biogas plants:
> The data do not indicate any increase in pathogen load in digestate.
> During the fermentation no pathogenic clostridia or close relatives of
> the C. could be characterized as C. botulinum. Also during the
> fermentation of cattle manure in biogas plants, the amount of
> available clostridia had been reduced. (Published from the German
> Biogas Association in May 2010: "Informationen über Clostridium
> botulinum")
> Of course for precautionary reasons, the concentration of C. botulinum
> in the environment should not be increased. Therefore it would be
> appropriate to conduct quantitative research in bio-compost, faecal
> compost, dry faeces, and digestate in connection with investigations
> of the impacted soil to determine a possible longer-term increase of
> concentration in the soil. Also interesting would be the possible
> survival of C. botulinum spores on grassland after application with
> naturally contaminated compost and / or fermentation residues and
> their possible transition to the plants in experience.
> As long as potentially contaminated feedstock is crushed and heated to
> 133°C/3bar/20 one can be sure that C. botulinum spores are not
> surviving the composting or anaerobic reactor, and thus the discussion
> of possible high swings in biogas would be obsolete. Critical
> substrates are mainly chicken manure and chicken litter.
> Summarizing it should be clearly stated that the discussion about C.
> botulinum in Germany and the EU is pushed to a political level by some
> circles, but the recycling of organic waste and other bio-degradable
> waste materials will not be stopped, at least not in foreseeable future.

> Heinz-Peter Mang, University of Science and Technology Beijing, Centre
> for Sustainable Environmental Sanitation

> --- In This email address is being protected from spambots. You need JavaScript enabled to view it. ,
> Ralf Otterpohl <ro@...> wrote:
> >
> > Dear Margaret,
> >
> > Due to the long time lag from application of sludge from biogas to ill
> > animals there is little chance that the connection is becoming wisible.
> > Yes, the concern is definitely with municipal digesters for sludge
> > management if land application is done - and this is still very common
> > around the world. There are many clostridium bacteria around and as far
> > as I know also those producing botulinum are nor really rare. The
> > massive growth and with that toxin production is dependent on clearly
> > anaerobic conditions. This makes biogas plants a clear risk technology
> > for a very very severe illness.
[emphasis added by moderator, EvM, on 26 July 2014]
> >
> > Please let us know about your findings, I think ecosan is clearly about
> > caring for the overall systems, too. Loss of cattle is a severe risk
> for
> > the livelyhood of rural people around the world. There are some legal
> > resticions in working with clostridium botulinum.
> >
> > Best regards
> >
> > Ralf
> >
> >
> > Am 03.02.2011 02:07, schrieb Margaret McCauley:
> > >
> > > Ralf,
> > > Thank you for alerting us to potential hazards of biogas systems. My
> > > German skills are weak, so I will be looking for information in
> > > English on the issues you raise.
> > >
> > > It may be a little out of the EcosanRes mainstream, but I am curious
> > > if you (or anyone else here) think these hazards would be a concern
> > > for municipalities with sewer systems considering options besides
> > > sending the sewage to the nearest waterway. For example, the Lille,
> > > France use of organic waste to make biogas for buses. Obviously any
> > > land application of any excreta product needs to consider pathogens;
> > > from what I am reading in your message, it seems like the issue you
> > > describe in Germany is similar or perhaps the same as sludge
> > > application generally, and is not particularly linked to bio-gas?
> > >
> > > I am scheduled to conduct such an evaluation for a municipality, and
> > > want to make sure I am not missing significant costs or benefits.
> > >
> > > Sincerely,
> > > Margaret McCauley
> > > Seattle, USA
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