Does anyone have any experience with the Home Biogas toilet system? Right now it seems like one of the best options I've seen, but one of my concerns is temperature. I spoke to the company and the system should be around 20c or higher for best results. But I'm wondering how much of a loss I should be expecting as the temp drops? Winter, where I live, is relatively mild (averaging between 5-0c) and, though I can add a greenhouse or an aquarium heater, I realise that I will still be below that target temp.
I'm perfectly willing to set up an alternative solution (a basic composting toilet or likewise) for the few colder weeks. But at what point will the system stop functioning at all? will the biogas system be damaged by lower temps? Do I need to be concerned about changing out the digester contents? Will it need to be emptied completely and then reassembled once it warms up some?
I know it's a lot of questions. Any help would be greatly appreciated!
Thanks so much!
At 0° to 5°C you will get 0 to nothing in biogas production. Even worth the water inside the digester will start freezing at 0°C and by that could damage the system. I don't know how much gas you expect to be produced but within feces there isn't that much energy left that can become biogas. Then heating the system with additional energy might get you on the negative side of the energy balance. And on a side node 20°C isn't the right temperature: it is 37°C.
From what I remember from reading about biogas, it works ideally at temperatures like 37C (ie body temperature, for obvious reasons), and processes slower and slower as it gets cooler. At 20C it slows almost to a stop. We live in a cold climate and have cows at our school, so we were thinking we'd have to put the digester in a passive solar heated situation. If the process slows to a stop, not only would we not get gas at that time, but undigested manure would come out as the slurry. With cow dung that's not a problem, but human excrement would be unpleasant. One way around this, we thought, is to use a tank big enough to hold 3 months of manure, so that even if digestion slows down to stop in the winter, the manure remains in the digester and gives gas when it warms up after the coldest part of winter is finished. However your homebiogas.com link says that this is not a solution as the slurry in the digester changes its ph and is hard to recuperate from.
If you can't use the heater as suggested on their website, you might have to use a different toilet system for the coldest months, such as a Humanurebucket system, if you don't want any extra cost.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
posted 3 days ago
Thanks for all the info. I will definitely keep this all in mind. I really appreciate the help!
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