[Digestion] ID China biogas projects

Takamoto kyle at takamotobiogas.com
Thu Nov 22 00:12:03 PST 2012

Dear Nicolas,

Very exciting work and I will be interested to hear your results. Corn stalks would also be a potential additive here for us.

For measuring gas flow, we use diaphragm meters which have not proved to be a problem. Based on the calibration they should be good over a range of pressures. 

We measure gas produced per day at our lab by emptying the digesters once per day, but for clients who still need to use the gas we use the following protocol:

1. Empty digester to reasonable pressure (5kPa for example)
2. Let the digester fill with gas over 1 hour (pressure might rise to 7kPa, this number is not important)
3. Attach a gas meter to the outlet pipe and let the gas flow out until it reaches the pressure of step 1. (e.g. 5kPa)
4. Calculate gas produced in a day by multiplying the gas passed through the meter in step 3 by 24 (there are 24 hours in a day)

This is quick and dirty but usually good enough within a ±0.2m3 accuracy.

Please send your results out when you get them.

Managing Director
Schutter Energy Ltd.

On Nov 22, 2012, at 9:51 AM, Nicolas Borchers wrote:

Dear all,

I have been subscribed to the list for only a few days, and am pleasantly surprised by the relevance of the ongoing discussions, especially since our NGO is also working on the temperature management / insulation of household digesters.

Let me introduce our projects. Our NGO, Initiative Développement (ID), www.id-ong.org/cn , has built in China more than 2500 household digesters in poorly developed areas. These are of the Chinese fixed dome model, 10m3, and made of either brick/concrete, or concrete alone. We are following up these digesters and their users very closely, in particular since we certify the emission reductions with Gold Standard and sell the ERs to further self-fund our projects. This close monitoring allows us to detect and solve ongoing technical problems, and to provide regular biogas trainings and knowledge recycling for the households.

We are now looking more closely at how to further improve the management of our digesters, as well as the use of the slurry for agriculture. For this purpose, we are designing a series of field tests/experiments:
* measuring the influence of a layer of organic insulating material or compost, on top of the digester, on the temperature of the content and the gas production
* measuring the influence of different input mixes on the gas production (pig/cow manure alone; manure + corn stalks; manure + pine needles; manure + leftover tobacco leaves; these are the substrates available locally)
* testing the use of the slurry for soaking seeds: impact on germination rate, shoot growth and diseases (test plots)
* testing the use of the slurry for fertilising and spraying apple trees: impact on tree health, action against pests&diseases, tree nutrient uptake, apple yield (test plots)
* testing the efficiency of an optimised mixed fertilisation plan (biogas slurry+compost+mineral fertiliser) on corn, potato and tobacco test plots

We will implement these tests on our project sites in the south-eastern province of Yunnan in China, with half a dozen selected households. This represents a lot of work and follow-up in remote areas, so we clearly won't reach the accuracy of a proper research team. However, our goal is not to make research as such, but instead:
* to test the efficiency and practicality of methods developed elsewhere and tune them to the local conditions
* to use the experiments sites as hinges to spread adapted practices within the communities, in particular by organising village meetings and community trainings around the test sites

If any of you would have advice or documentation relevant to our projects/experiments, I would be more than happy to hear from you. I'd also be glad to share our results with people interested.

Furthermore, we are facing two urgent measurement issues:

1 - how to measure the volume of biogas produced (or rather, consumed by the user on their stove)? The gas indeed varies in pressure, so that positive displacement flow meters (such as diaphragm meters), are not suitable. What kind of system would you advice to measure the gas flow out of a digester, that would be compensated in pressure, or measure the actual mass flow of the gas? Our typical daily production is in the 1m3 range.

2 - temperature measurement: we would like to measure the temperature within the digester with 0.5°C accuracy, and are looking at thermistor (NTC) or pt100 measuring devices with a 3m long cable. The probe could be introduced through the compensation chamber for each measurement, or left in place depending on the cost. We've also been thinking of using data-loggers. Could you advice cost-efficient solutions? We're also wondering about the temperature layering inside the digester? Can you suggest an upper limit on the temperature gradient?

Any advice would be welcome!


Nicolas Borchers

Nicolas Borchers 博石屹
Organic Farming Officer 有机农业项目官员

+86 159 2552 3303
Skype: nborchers

Initiative Développement – China  法国发起发展组织
402, B2, Fubang garden, Shulin st., 650100 Kunming, Yunnan province, China
云南省昆明市书林 街富邦花园B座2单元402室  邮编:650100
+86 (0)871 3181557

Energy Globe Award 2009 and 2011
International Solidarity Award (HCCI) 2007

Offset your carbon emissions with ID – www.id-ong.org
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