AD Feeding with Auger or Pumped System?

[thesilentone]

Same here, hydraulic ram pushes our feed to one end of the hopper and then a single auger puts it direct into the digester. Grass whole crop beet and hen litter, no issues incorporating into the digester and no shock load? The tank is nearly a million gallons so 600kg every half hour doesn't get much of a chance to cool it!

To clarify the point between cooling and shock loading. When new material is fed to the process, the gas production immediately go's down below it's current level.However, this is only temporary and increases again quickly, not only back to it's existing level, but above this by the new VS added. A cold biomass temperature increases that curve and time. Pre-homogenised, per-heated biomass has a similar effect, just the curve is less, as is the time. Shock loading in terminology for new and fresh biomass added. (A bit like you having a very cold beer when very hot)

 

[sjt01]

When new material is fed to the process, the gas production immediately go's down below it's current level.However, this is only temporary and increases again quickly

What timescale are you talking about? If we have an interruption in feeding for a couple of hours, then restart, gas production rises within 30 mins.

 

[sjt01]

The tank is nearly a million gallons so 600kg every half hour

A million gallons is 4500 m3 approx, or 4500 tonnes. Feeding 600 kg per 1/2 hour is 28.8 tonnes per day, so your HRT (hydraulic residence time) is 156 days. That's about the longest I have heard of, massive invesetment in tank. What sort of gas yield do you get or engine output?
We run at 50 days, but most of the crop fed digesters around here run at 35 days in the primary digester, then go to an unheated second stage.

 

[thesilentone]

Retention time should not exceed the slowest growing bacterial group.

 

[sjt01]

Retention time should not exceed the slowest growing bacterial group.

How do you determine that? We have DNA profiles of our bug population, and are doing this every week as part of a research project. When we started we had good bacteria but a weak Archaean population, so our VFAs were too high. I look forward to seeing the dynamics of the Archaeans and the Bacteria in the digester; as far as I am aware this is the first time such a project has been undertaken. We are one of 7 digesters taking part in the study, the first results showed over 700 different genera in our bug population.

 

[Digester Man]

We have a 34-18m ring in ring,gross outer ring is 875,000gal and inner about 320,000gal. The two fermenters run at about 90% volume so more like 800,000 and 290,000 respectively. I have fed in the range from 25-35 tons a day depending on quality and dry matter,but around 28-30 is the norm. Retention time was calculated by my lab at about 130 days. Output is about 270m3/hr and 500kw

 

[sjt01]

Is yours a Marches design?
Output looks similar in proportion to our single stage 720 m3 working volume. In January we averaged 157 kW and fed daily on average 7.7 tonnes slurry, 5.5 tonnes maize, 3.6 tonnes beet and 0.5 tonnes whey. Bugs behaving well for the month, got trace elements sorted out.

 

[Digester Man]

No it's a German outfit by the name of Biogas Hochreiter, they have been in the game since the early days, 1500 plants to their name so far in probably 20 countries. We have no macerators, extruders or hydrolysis etc, instead the plant relies on a long retention period to let the bugs do the work. The material moves through the two fermenters and on to the final storage tank by overflow, so there is no pumping requirement other than adding some fresh slurry if desired. The system took some adaptation when they firstcame to N.Ireland but with 10 or so plants now built and a 2.5MW plant under construction in Carlisle they have a proven system for handling high inputs of grass silage.

 

[sjt01]

Sounds a nice simple system, How is it stirred and heated?
The first people to quote us were offering a similar system, as agents for a German company. Called Renewable Zukunft or similar, headed by Tim Evans, until they went bust. It must have been 10 years ago that he visited us.

 

[thesilentone]

How do you determine that? We have DNA profiles of our bug population, and are doing this every week as part of a research project. When we started we had good bacteria but a weak Archaean population, so our VFAs were too high. I look forward to seeing the dynamics of the Archaeans and the Bacteria in the digester; as far as I am aware this is the first time such a project has been undertaken. We are one of 7 digesters taking part in the study, the first results showed over 700 different genera in our bug population.

Something to follow: https://www.linkedin.com/groups/727...ro-12-view~discussion-null-104e9s~iymryioi~5g

 

[sjt01]

Something to follow: https://www.linkedin.com/groups/727...ro-12-view~discussion-null-104e9s~iym

Interesting to note that of 50 participants offered places a year ago, there are 48 places left.

Our digester analysis is done as part of this project
http://osslab.lifesci.warwick.ac.uk/adLola_rsrcs.html

If you follow the links through to http://anaerodynamics.com/ we are AD07

 

[thesilentone]

Interesting to note that of 50 participants offered places a year ago, there are 48 places left.

Our digester analysis is done as part of this project
http://osslab.lifesci.warwick.ac.uk/adLola_rsrcs.html

If you follow the links through to http://anaerodynamics.com/ we are AD07

What caused the spike in CH4 quality in Dec 16 ? Who is AD16/1 ?

 

[sjt01]

What caused the spike in CH4 quality in Dec 16 ? Who is AD16/1 ?

The spike in methane was the start of trace element addition, resulting in a dramatic reduction in VFAs as the methanogens caught up with the actogens.

The other plants are all anonymous, all we get told is our own number.

Just come across this:
https://www.wur.nl/en/show/3rd-International-Conference-on-Biogas-Microbiology-ICBM-3.htm
and wondering how much over my head this will be.

 

[thesilentone]

The spike in methane was the start of trace element addition, resulting in a dramatic reduction in VFAs as the methanogens caught up with the actogens.

The other plants are all anonymous, all we get told is our own number.

Just come across this:
https://www.wur.nl/en/show/3rd-International-Conference-on-Biogas-Microbiology-ICBM-3.htm
and wondering how much over my head this will be.

It looks like you have missed the first two

My experience of this type of meeting is ' boring as hell ' however, seeing positive results from experimental work is great. Most of the cutting edge research is being done by the technology providers own labs, or in conjunction with a University funded by tech company.

http://www.au.dk/en/search/all/?q=anaerobic+digestion

 

[Digester Man]

Sounds a nice simple system, How is it stirred and heated?
The first people to quote us were offering a similar system, as agents for a German company. Called Renewable Zukunft or similar, headed by Tim Evans, until they went bust. It must have been 10 years ago that he visited us.

Hi Stephen, outer ring has 4no 6" stainless heating pipes around the walls pumping hot water from the engine. We have 3 Mississippi paddles which work the top layer, one standard submersible propellor mixer on a guide rail that can work any depth (rarely turned on) and a side mixer through the wall.

The inner has 3 pipes around the walls and also benefits from the outer ring keeping it warm. It has one vertical paddle mixer with 5 blades top to bottom, and a submersible on guide rail.

It takes every bit of it when things get thick but haven't just been beaten yet!

Ps - great to see some other operators on here and hear their experiences.

 

[sjt01]

when things get thick

Sounds as though you have quite a bit of installed power for mixing. You say "when things get thick", what sort of total solids do you work at? Our feed system does not work well outside the range 7.5-9.5% TS. Most of the time it stays there without intervention. When we fed fodder beet (rather than energy beet) we had to feed back separated solids to keep it up. If it goes too thick, we pump some liquor in from the dirty water lagoon.

Stephen

 

[sjt01]

Anyone going to Energy Now on Weds? If so could meet up.

Also thinking of going to the first day of the ADBA R&I conference next month, agenda looks interesting

Chair:
• Thomas Minter, Director, Malaby Biogas

Speakers:
• Dr. Yue Zhang, Lecturer in Environmental Engineering, University of Southampton
“Competition for trace elements between different players in anaerobic digesters”
• Erik Nordell, Development Engineer Biogas, Tekniska verken i Linköping AB
“The effect of trace element addition at different process conditions”
• Frank Scholwin, Director and owner of Institute for Biogas, Waste Management and Energy and Honorary Professor for biogas / bioenergy at University of Rostock
“How to control output variability in industrial AD? Experiences with trace elements supplementation, trace elements circulation and large scale process data evaluation”
Questions and comments from the floor
14.55-15.25
Afternoon Break and Exhibition
15.25-17.05

Digestate risk management and income-generating opportunities

Chair:
• David Tompkins, Bioresources Development Manager, Aqua Enviro
“Digestate hazard management: Known unknowns”
• Dr. Ewan McAdam, Reader in Process Engineering, Cranfield Water Science Institute
• Nina Sweet OBE, Special Adviser, WRAP
“Next generation ammonia separation from digestate: Introducing the Membrane Ammonia Crystallisation Reactor (MAC-R)”
• Mary Dimambro, Managing Director, Cambridge Eco
“Innovative uses for digestate: Urban and protected crop production”
Questions and comments from the floor

 

[Digester Man]

I was at 11% DM last year and it was bloody thick. The mixers were just at the limit running 24/7 and it took a prolonged amount of slurry and the addition of beet to thin it down again! Had some very poor silage last year and surprisingly dry, so to maintain the output I had to increase feed a lot and things just didn't go according to plan. Back on the straight and narrow now, we are also using trace elements, I think a necessary evil unfortunately. Won't get across to the Energy Now event unfortunately, looks interesting though!

 

[sjt01]

We have gas mixing, which keeps everything that needs servicing away from the tank, also relatively low power but works best in "square" or tall tanks - ours is 10 m diameter, 10 m tall.

 

[The Son]

Have the same issues as you @Rob_AD in the winter dm is around 9% as I am using sugar beet, apple pomace, and all the dirty water off the silage pits goes through the system. In the summer I am feeding wholecrop and grass silage and dm increases.
My plan this year is to try and find a reasonably priced tank and source a liquid with gas in it over the summer, perhaps whey?