HomeBiogas Toilet Turns Poop Into Fuel

HomeBiogas is one of those companies we’ve been following for a while. From their very first crowdfunding campaign to the launch of HomeBiogas 2.0, the promise of a domestic, anaerobic waste digester feels like the type of story that this website was built to cover. Here’s what I wrote at the launch of their new, improved 2.0 product: 

“Given the huge problem of food waste going to landfill, an appliance like this could go a significant way toward reducing a household's carbon footprint. Not only does it prevent methane emissions related to food rotting in landfill (yes, it can take cooked food, including meat and fish!), but it can provide up to three hours' worth of gas for cooking, too—replacing natural gas that might otherwise be fracked and transported from hundreds or even thousands of miles away. As an added bonus, you also get free fertilizer for your garden.”

One of the questions I remember being asked the last time is whether the system could handle pet and/or human waste. The answer, apparently, is a resounding yes. In fact, not only is the HomeBiogas system capable of turning toilet waste into cooking fuel, but the company has now actually launched a fully flushing bio-toilet kit designed specifically for this purpose.

Here’s the scoop from their website: 

The HomeBiogas Bio-Toilet Kit is a superior alternative to regular compost toilets. It frees you to live in a self-sustainable manner by turning your pollutant body waste into a valuable resource. Using an anaerobic system it decomposes waste and transforms it into renewable biogas for cooking. It’s easy to install, safe, hassle-free, non-pollutant, environmentally friendly, and completes a full eco-cycle in your own home with no need for outside resources.

Included in the kit are a ceramic toilet bowl and pump; a HomeBiogas 2 anaerobic digester, waste and gas pipes, water and gas filers, as well as a custom ready-for-biogas cooking stove. And clocking in at $1,150, it compares pretty darned favorably to some of the manufactured composting toilet systems out on the market—which often carries a similar price tag, and yet don’t produce a fuel source or have the ability to also deal with your households cooking waste. (For the squeamish, the added bonus of a familiar flush toilet mechanism that simply takes your waste "away" is likely a bonus too.) 

It’s still unlikely to become a plug-and-play option for the vast majority of the population. But for folks who are into the DIY, off-grid version of lower carbon living, it’s a pretty attractive proposition. 

There are, of course, some caveats. The digester itself has to sit in full sun to work, apparently, and can’t be more than 32 feet away from the toilet bowl. It also looks like you need both electricity and running water in order to make this thing work, meaning some more primitive off-grid "cabin"-type locations may not work. The makers also include a caveat that you shouldn’t use the resulting effluent as fertilizer, as one would if just putting food waste in the digester. (Although, given the number of people using "humanure" on their fruit trees and ornamentals, I am curious as to how many folks flout that caveat...)

The biggest question I have, which I have yet to find a clear answer for, is how much we should be concerned about methane leakage and/or venting. The site does say that if the storage bag gets too full, then biogas is simply vented off through a safety valve. Yet given what we know about methane emissions and the climate, we should probably hope that this is not a common occurrence. 

I mentioned this caveat to my fellow treehugger, design editor Lloyd Alter, and he reminded me that many "regular" composting toilets are likely a source of biogenic methane. (Municipal waste infrastructure is a source of methane emissions too.) While it's unclear how much methane could be expected to leak and/or vent off from a system like this, I suspect this is a pretty good option for folks with a) sunlight b) space, and c) an interest in turning human waste into something more useful.