[Digestion] Introduction to Pay As You Go Biogas and a Strange biogas startup problem

Kyle Schutter kyle at takamotobiogas.com
Thu Sep 19 02:50:48 CDT 2013


Dear David, Alex, Vishwas, and the Group,

The cost of our meter right now adds 10% to the cost of a 3 cubic meter system but of course if the system is larger the percentage drops.

In our case, the smell of the digester isn't all that bad. Instead, the gas that is produced smells very bad. The slurry temperature in our case is always below 25C whether it is the warm season or the cold season.

In response to Vishwas, it seems like temperature shock cannot be the only thing (though in combination with other factors may be the cause) because in May and June we would have flammable gas produced 3 to 7 days after installation. In July 50% of digesters didn't even start up after 1 month. In both cases the temperature of the dung dropped from 37 inside the cow to less than 25 outside the cow. I guess it could be that in May it was a drop of 37 to 24ish, while in july it was 37 to 15ish. We work in a very cold part of Kenya so some of the rules of thumb about working with biogas in the tropics don't apply.

The solution sounds like we should start slower. Put in cow dung and innoculant. Wait for 14-90 days until flammable gas is produced. Make sure rain water is not falling into the digester which could start to make the effluent come out. Only once flammable gas is produced should we add more cow dung and even then the addition should slowly ramp up. It is interesting to hear that Alex doesn't start his digesters in the coldest two months. That is good to know.

Alex, really good questions in relation to Pay as you go biogas. We are wondering some of the exact same things. Last year we were deciding between whether to charge per cubic meter of biogas or per day. Because our system produces a fixed amount per day, at first it seemed to make more sense to charge per day and the client uses as much as they want. However, this became more complicated when we considered that we would be installing different sized biogas systems. We would need a different daily charge for each of these systems. And then what happens if we improve the efficiency of a biogas system (let's say we heat it but it remains the same size) how do we explain to the client that they will now pay more per day because they are using more gas? And what if the digester isn't running well, should the client still pay the same daily rate enough though they are getting less gas then their neighbor, through no fault of their own?  And payment per cubic meter leaves open the possibility of net metering of biogas (our clients are usually 50 feet apart.) But outweighing all of this we wanted to incentivize our company to increase gas that a customer can use, not increase days that a customer buys gas. There are cons to having a per cubic meter charge for biogas, more gas may escape to atmosphere (though this will happen to some extent anyways) and a customer doesnt pay for this gas that is leaked. Right now, 50% of our clients use all the gas that is produced and we are working on training to increase this. Eventually, we want to flare excess gas or meter it to a grid. The smell of gas leaking hasn't been a problem, even at our office in the city where we have three biogas systems for testing.

I am not worried that our farmers will not be incentivized to use the biogas systems. First they make a payment of $100 for the installation of the system which makes them put skin in the game and proves they really want the biogas system. Second, we have selected farmers who are currently using fuels that are more costly per unit of cooking than the price of our biogas so they are incentivized to use the biogas whenever possible as it is cheaper. If a farmer doesn't use their biogas we can (according to our contract) remove the system. Of our 70+ installs we have done this for two and it was an easy process.

System management is an interesting one and you bring up a good point. If the client doesn't have an incentive to use more biogas they will not fill it. Our systems typically produce 1.1 cubic meters of biogas per day. Some early clients who do not have sufficient need for biogas (we later learned how to weed these out) only fill their system 2 times per week as those clients realized they don't need much biogas. What we have done for systems management is that every day we get an update on each system in the field by data connection or SMS (data is cheaper) that tells us:
the pH of the system
temperature of the system
if the system has been feed (flapper door on inlet)
the pressure in the system
if the client has tampered with the meter
the battery charge on the meter
height of the drum
gas usage by hour
leak alerts
meter connectivity to the network
If the group has ideas for other things that we should monitor please let me know and we will see if it is cost effective. One that I was thinking of was ORP sensor (oxidation reduction potential) but I am not sure what this would tell us.

I think this aspect of system management is quite interesting. When you go to a farmer and ask them how many times a week they feed the system they will say whatever you initially told them to do. But if you can monitor this you actually can know how often the client is feeding and see if that is a problem. In some cases we have had clients say that the system is only producing enough gas for tea but we can go back to the records and see that they used .1 cubic meters in the morning, .5 at lunch time and .4 at dinner and we know that the system is working fine, we just need to train the client on using the gas more efficiently (not cooking with a flame that wraps around the pot, using a lid to boil water, use a pressure cooker to cook dry beans, etc)

Right now our pricing is Ksh55 (about USD 0.65) per unit (a unit is a cubic meter of biogas at STP). It would be interesting to have different pricing to encourage more biogas usage. I am not sure how the below pricing schemes could be implemented, but here are some ideas:
a fixed amount for the first cubic meter per day and a lower rate per cubic meter for all gas beyond that. e.g. Ksh 65 for first cubic meter and 35 for each cubic meter after that
a fixed rate per day (e.g. Ksh 70 per day)
ksh55 for gas consumed and ksh35 for gas sold to the grid
monthly unlimited for Ksh 1,650
maybe you have some other suggestions


Thanks for all your suggestions and I look forward to your thoughts on our metering and pricing. I am counting on you to give us your constructive criticism!!



Kyle
Founder and Director of Technology
Schutter Energy Ltd.
+254 703113383
kyleschutter (skype)
www.takamotobiogas.com



On Sep 18, 2013, at 1:46 PM, David wrote:

Kyle, Hello,
 
The meter system looks very interesting. How much does it add to the cost of a biogas system?
 
Are you using above ground plastic tank plant, as shown in the website? If so, the gas production will be strongly affected by air temperature. Once the slurry temperature drops below about 25 deg.C, digestion will take a long time to get started. It is possible that the acid formers will be generating volatile fatty acids faster than the methanogens can work, so the plant goes acid (and smells bad). Have you measured the slurry temperatures of the plants that do not work well?
 
Methanogens take a long time to grow, especially at lower temperatures. There is also the issue of temperature shock. When the dung is dumped by the cow in a cold place (less than 25 deg.C), the temperature drops (from the temperature inside the cow of about 37 deg.C). Methanogens are affected by a temperature drop of less than 5 deg.C in one day. They do not die, but go into a quiescent state and take time to start again, especially if the temperature remains low.  
 
Best wishes,
David
davidf at kingdombio.com
 
******************************************************
Dr David Fulford CEnv MEI, 15, Brandon Ave, Woodley, Reading RG5 4PU
       Tel: +44(0)118 326 9779 Mob: +44(0)7746 806401
Kingdom Bioenergy Ltd, www.kingdombio.com, davidf at kindombio.com
                                Skype Identity: djfulford
 
 
 
------ Original Message ------
From: "Kyle Schutter" <kyle at takamotobiogas.com>
To: Digestion at bioenergylists.org
Sent: 18/09/2013 09:35:39
Subject: [Digestion] Introduction to Pay As You Go Biogas and a Strange biogas startup problem
> Hi All,
> 
> I would like to introduce our business to you all that we have been working on for the last 12 months.
> 
> We have developed a Pay As You Go biogas meter that charges clients for gas as they use it, instead of a single high upfront cost of purchasing a whole biogas system. Our clients pay by mobile money and when they run out of credit the meter automatically shuts off. Our system also communicates to us by GSM on the status of the system (if there is any leak, pH of the system, pressure, etc) every day by text message. See a diagram of how this works here http://www.takamotobiogas.com/takamoto-pay-as-you-go-biogas-50-unit-pilot-is-a-success/ I look forward to getting your feedback.
> 
> We have 70 systems installed in the last 4 months using our Pay as you go meter which is a huge success for us. However, we are having a seemingly unrelated problem with system startup and I would love to get your advice on how I figure out what is going wrong.
> 
> When we install a biogas system we fill it with dung and water and for systems installed in the last month we have added 5% of the total volume as innoculant from a biogas systems that is working well. We have made sure that the cow dung is not from cows that have received antibiotics and the cow stalls haven't been sprayed with dissinfectant. For the first 30 systems we installed, there was no problem startingup; the first 30 required no innoculant and started producing flammable biogas in 3 days. But since then, especially during the rainy and cold season, digesters have not started up reliably. I would say that more than 50% took more than a month to work efficiently and at least three systems had their pH drop so low (around pH 6.0) that we decided to replace the cow dung. For the systems that are not starting up very well, we add 200 kg of innoculant every week until it starts working. I tested the water that our clients use to mix with the cow dung and found that it was rather acidic (pH 5 to pH7) but this was true of clients whose systems were working too, so the acidity of the water can't be the only problem. 
> 
> The symtoms we are seeing are as follow: 
> -The pH is below 7 (but not less than 6.5) 
> -Some gas is usually produced but it is not flammable and usually smells very bad (lots of hydrogen sulfide) 
> 
> It seems that there could be several possibilities here: 
> 1. There is a breakdown of the biological pathway. Either we are missing some bacteria or there is some inhibitor. 
> 2. There are a combination or problems involving cold temperature, rain water and low pH mixing water (though we are still having a problem after the cold rainy season). 
> 3.There is some toxic substance in our tanks or the cow dung that is causing the problem.
> 
> I look forward to your feedback on both the new meter and on the startup problem we are having.
> 
> Best wishes,
> Kyle
> Founder and Director of Technology
> Schutter Energy Ltd.
> +254 703113383
> kyleschutter (skype)
> www.takamotobiogas.com
> 
> 
> 
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