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Comment by z92 | Hacker News Reader

Unanswered question, where does the remaining waste from the plant go? Surely not all of the mass is converted into gas. And with 1000 tons per day, there should be a lot of waste to dispose off somewhere.

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Anaerobic biodigesters are very common here in Germany. The residue is a really good fertilizer that can be applied to the fields. At least here in G the nitrogen application from this has to be documented and subtracts from the N fertilizer budget farmers are allowed to apply.

The only downside is that to the best of my knowledge, those installations tend to be designed without storage in mind, running the generator at whatever time is convenient thanks to flat feed-in rates. Making them dispatchible would be by far the single lowest-hanging fruit in the whole field of grid storage.

(Correct me if I'm wrong, I'd love to be)

They provide such a minuscule amount of power that I'm not sure whether making them dispatchable is worth the effort.

Take a look at https://energy-charts.de/power.htm : pumped storage peak discharge hardly ever reaches a level of contribution as high has biomass and that is basically all the non-fossil dispatchability that we have. Meanwhile, biomass is running as baseload more stubbornly than even nuclear.

Making the biomass contribution dispatchible would be huge.

Changes in regulation in G require operators to upgrade generator capacity in order to utilize gas storage to produce electricity at peak demand and not flat all the time.

Is that change already in place? Do you have any links or keyword suggestions for a bit of news googling? (German would be fine for me, but English is obviously preferable for the benefit of other readers)

It is already in place since Jan 2017 I think. Energieeinspeisegesetz is the relevant keyword. But this redesign of the regulation is really complicated with a lot of different cases and exceptions. No concise summary in english I'm afraid.

edit: fixed typo

Thanks, 2017 was already quite useful for narrowing down search results.

Pre-existing requirements for the seasonal storage of manure on dairy farms (primarily because you aren't supposed to spread manure in the winter) means that many dairy farms already have large manure storage lagoons/tanks. These are adapted into digestate storage tanks when the system is installed, although the additional food waste volume can result in additional storage volumes being required. What is nice about some of the manure storage tanks is that you can sometimes just add a 'ring' onto them to increase storage volume.

the digestate is then spread on farm fields using similar methods/equipment used to previously spread manure.

It's used as fertilizer on the fields.

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