Hi Michael, thanks for getting touch. I'm currently based in Sydney and not regularly in Cambodia. This project is being continued through the ATEC* enterprise: www.atecbio.com/

The best person to contact would be Ben Jeffrey's of ATEC*.

Cheers,
Rob

Hi Rob - I live in Phnom Penh and would like to get together sometime to discuss biogas digesters (BGD) - I've just finished design of a radical new BGD that flatpacks and would like to discuss it with someone who has first hand experience - I'd also like to come and look at your project out at Tonle Sap sometime if i may - also, love the floating gardens idea - great stuff
cheers
Michael

Hi again,
Just wanted to let you know we were successful in the Google Impact Challenge, and will receive AUD$500,000 towards this project.

impactchallenge.withgoogle.com/australia2014

So keep an eye out for further development of this work, including transitioning to scale - we are hopeful this phase of work will provide some useful models for others to learn from and replicate around the world - both for 'challenging environments', and for where feasibly producing biogas at a small scale can encourage greater sanitation uptake.

Dear colleagues,
I just wanted to update you about this project. Our pilot & demonstrations were fairly successful at showing operation in some quite challenging situations and I'd be willing to share further information for anyone interested.

We have a 4 in 10 chance of receiving AUD$500,000 to further improve the small scale and adaptable biodigesters we have developed and establish the business models and enterprises to make them more widely accessible and scale up. Despite successful and promising pilots and demonstrations we have so far been unable to find funding to continue the work and get it ‘across the line’ to be self-sustaining in the community, but may be about to do that with this grant.

Live & Learn will be partnering with Engineers Without Borders Australia, who will be coordinating the overall project and linking to other strategic partners.

There are 10 finalists, and there is currently a public online vote that will determine at least one of the 4 grantees, and may influence the result of the other 3. So it would be very helpful if you could vote for “Engineers Without Borders Australia”, here: g.co/australiachallenge , or here: impactchallenge.withgoogle.com/australia...eers-without-borders

Additionally, if you could further publicise this and encourage voting, it could be very helpful. There are facebook, twitter, and website links below for your use.

The biodigesters are designed to not be dependent on subsidies, ideal ground conditions, or large numbers of animals, which are some of the main barriers to an otherwise quite appropriate technology. Let me know if you would like more info that isn’t covered in this thread above!

Thanks a lot!
Rob

www.facebook.com/sharer/sharer.php?u=htt...eers-without-borders

twitter.com/intent/tweet?url=https%3A%2F...eers-without-borders

www.ewb.org.au/

Hi,

Thanks for the transcript Elisabeth. I think your answers summate the questions well.

In answer to your questions. Pig pens do infact float, I've attached a photo for those interested in the floating pig pens.

We are just finalising some of the results from our initial experiments now and will hopefully have a document uploaded onto the library soon. But preliminary results have shown that the biodigesters are very robust systems and capable of working with feeds of pigwaste, pigwaste (75%) and water hyacinthe (25%), and pig waste(92%) and human waste(8%). All feeds deliver similar results in terms of pathogen reduction and gas production, though mixed feeds appear to produce slightly higher amounts of gas than the pig waste alone.

Some villagers have been able to replace all of their firewood with gas, this is due to the use of pigwaste in the biodigesters. Though work from NBP suggests that if you could collect similar amounts of human waste you would produce similar amounts of biogas it just happens that pigs produce more waste and hence more gas. More information for the National Biodigester Program (NBP) can be found here www.nbp.org.kh/

The safety bottle that Julius mentioned is the one we use in our systems.

Julius to aid digestion of the water hyacinthe at this stage we have been cutting it into pieces of approximately 2 cm using a machete, I don't have any experience with the plantain/matoke products you mentioned.

Kind Regards,
Gabrielle

Interesting updates.

With the "safety bottles" she meant most likely a pretty standard flame trap like illustrated here: www.adelaide.edu.au/biogas/safety/flametrap.jpg
(They are usually made out of bottles, hence the name)

Regarding the use of water hyacinth:
Do they have any easy way to shred it to small easily digested pieces? The lack of such is the main problem with using those as biogas feedstock here in Uganda. Even worse in that regards are all the plantain/matoke waste products which are created in rather large quantities on markets and in the households.

Here comes my fourth and last transcription from the expert talk on 1 July (see here for an explanation about the expert talk in general: forum.susana.org/forum/categories/98-res...-dealing-with-biogas). Gabrielle’s topic was different from the other three because she is not working in the lab but doing applied research.

I welcome you to watch the online discussion that we recorded with Gabrielle McGill on 1 July where you can learn more about the research with floating biogas digesters on the Tonle Sap, carried out by the NGO Live and Learn Environmental Education in Phnom Penh in Cambodia. Gabrielle’s explanation about her project (with 3 powerpoint slides - see file below - and with that lovely Australian accent!) starts at 51:37 into the recording; it is followed by questions and answers that start at around 1:00:00 (sorry there are some small technical problems with the sounds towards the end).

I have added the Youtube link below to start at exactly the right time:



I found the following points from her presentation and from the questions very interesting:

(1)
Unlike the other three experts, her research is very applied, working directly in the community with real people and real waste. She said they now have 30 systems in the community. There are actually 1.6 million people around Tonle Sap Lake, most of them are “floating communities” with “floating houses” and lacking sanitation systems. She also mentioned that there are many pigs (are the pig stables floating, too? Or how does that work?).
They were experimenting with two types of digesters together with the local university; the digesters are also in the water and float. The one type is cheaper and from plastic sheets (read and white stripes on the photo, see pdf file below); the other is from plastic water tanks (same photo).



In the experiments they were using pig waste, because pig waste is also a big problem with the communities – normally it just goes into the lake, I presume.
They are working with a 30 day detention time in the digesters and were experimenting with different combinations of pig waste to human waste and different retention times. They were focusing on gas production and pathogen removal as performance indicators (Gabrielle: can you share the research results with us?)
They ran training sessions with the villagers on how to fix things if something is broken with the digester. There is a flexible hose to connect the biogas from the biogas reservoir to the house where the biogas is used. The villagers can replace all their firewood needs with the biogas which is very impressive (must be due to the pig waste, as you get a lot of biogas out of the pig waste).

(2)
She mentioned a National Biodigester Program in Cambodia, which offers subsidies for different types of digesters. In the future, LLEE will partner with them. This National Biodigester Program has developed a simple sulfur removal system to clean the biogas of sulfur (Gabrielle: photos for this system?).

(3)
In terms of cost, she said their smaller systems cost 200 USD (made from a plastic water tank). This is still a lot for a Cambodian household, but it would pay back after 2 years when considering the value of the biogas produced compared to the costs of firewood.

(4)
I asked her if she had added algae to their digesters. She said they have not tried it with algae but with water hyacinth which is a noxious weed on the lake (what were the results?). She said there is probably some people who would be interested in having even more biogas, even though they already have a lot.

(5)
I also ask her about safety aspects with the biogas systems (possibility of explosion). She explained their risk management measures:

• They use safety bottles (what is that?)
• The systems operate at low pressure: the sludge should be pushed out through the outlet rather than allowing gas build-up in the tank.
• The gas reservoirs are installed well away from the houses and from flames.

And she pointed out that the perception of risks is also different in Cambodia because it has to be seen in relation to other risks that the communities have to live with and manage.

(6)
Jianmin asked if there was any mixing in the digesters? Gabrielle explained that there is no particular mixing system inside because that would be too expensive and complex. Mixing takes place by the new waste that is added per day. Also the waves (in the case of floating digesters) will help with the mixing.

I hope that some of you find this useful. Please don’t hesitate to ask further follow-on questions to Gabrielle and Rob, as this is an ongoing applied research project which is continually producing more results and increasing their level of experience.

Regards,
Elisabeth

Hi

I'm Gabrielle McGill. I'm a volunteer with Engineers without Borders who is working at Live and Learn Environmental Education Cambodia on this project.

On Monday I, on behalf of Live and Learn, participated in an online discussion with 3 other BMGF grantees who are also working with biogas systems.

You can view the discussion on SuSanA's youtube channel here. The discussion of our project starts at around the 52 minute mark:

Thanks Julius and Gökce,
Yes external damage is a key issue with the plastic-style digesters, so we have been trying different materials such as more durable fibre-reinforced plastic, as well as protection options (eg against UV damage). We're also currently using modified HDPE water tanks.

Julius I'm not sure rotation around the axis would help mix very much unless there were large seams etc? Also would need to consider gas offtake.

We're also looking at using the bioslurry in aquaculture ponds at our test site and land-based sites, however on the lake itself direct output to fairly open fishcages is more likely. This is already done with the manure, so essentially we're adding a stage to reduce pathogens and extract energy. We're also working on floating gardens and planned to have these also part of an integrated system producing pigs, fish, vegetables, and biogas - basic versions are operating, but still need improvement. Gökce we've tried to encourage climbing & small shrubs eg beans, tomatoes, gourds, eggplants etc - so there is separation between the slurry application and the produce itself.

The temperature in the lake water is typically around 26-33 degrees, so fairly stable. Due to this, thermal transmission in water, and the simple/low-cost nature of materials involved we're only going to be able to achieve mesophilic biodigestion. The first round of systems are achieving 2-log pathogen reduction, which we can hopefully improve with some modifications.

We're still collecting data on the gas production - but it seems to be around 300L biogas daily average for a 500L system (say with 2 pigs - around 6kg/day = 13L bioslurry). We've been very happy in most cases with the amount of biogas being produced and used by people with small systems and few animals. Our next round of experiments should give us a better idea of the potential with human waste and water hyacinth. Of course the gas production by human waste will be less than with pigs due to the quantities, and we're keen to discover if we can supplement the feed to make it feasible without animals.

Cheers,
Rob

Dear Rob,

I would like to ask you couple of questions regarding your innovative work.

How much gas is produced daily and for which purpose do Tonle Sap Lake communities prefer to benefit from the produced gas (for cooking or electricity production)?

What is the average temperature of the water? Do you achieve mesophilic or psychrophilic conditions and how is the pathogen removal efficiency? What is the amount of digested sludge that you remove and how frequently you do it? As I understand, you use the digested sludge in floating gardens. What kind of plants have you selected for these gardens?

Thank you in advance.

Regards,

Gökce

Ahh, interesting.

I recently looked into floating plastic-bag biodigestors as that seemed like a great way to avoid the (apparently in Uganda significant) problems with external damage to the plastic tube which is caused (by anecdotal evidence) through playing children & rodents (and probably other forms of neglect and misuse).
However except for a few short paragraphs and pictures, it was impossible to find good examples of such a design.

Contrary to what you are proposing, it was my idea however to integrate them with aquaculture ponds, with the effluent directly fertilizing the micro-algae growth to feed tilapia.
As a beneficial side-effect the surface of the digester would probably be a good substrate to facilitate the surface growth of the tilapia preferred feed algae (that normally grow on the surface of stones and water plants etc.) and provide shadow and cover against bird predators.

Another interesting design aspect could be that such a floating tube digestor could be manually rotated along its axis to provide for a better mixing of the slurry and thus increased bio-gas production.
Edit: Ah, and the mean temperature of the digestor should be more stable (but a bit lower due to evaporation) also, thus likely resulting in a more consistent digestion especially where there are bigger day/night temperature differences.

Anyways, please keep us updated on the results of this!

I've attached a recent Masters Thesis on the Environmental Sustainability of Floating Biodigesters on the Tonle Sap.