Yes, it is safe.
Since this is a commercial system that has been deployed in many countries and tested for years for safety in people's homes and gardens and schools, it has the CE rating and government approvals for safety standards in Israel and the US.
HomeBiogas has a team dedicated to answering questions for new users, so we don't have to try and reinvent anything; the system is just new to the US so people are unfamiliar with it.
Basically it is a "sealed liquid compost bin" rather than a machine. It is always filled with water and hence can never pose a fire hazard. The compost it produces, which is a liquid compost tea, is odorless and bacteria free thanks to a chlorine sterilizing disk at the output side. It doesn't attract any flies or vermin, unlike solid compost bins.
The amount of biogas that slowly bubbles out during warm days when fed, can only reach a certain volume, is contained within the flexible bag above the water reservoir and is under such low pressure that it represents no bursting hazard. It contains no air so it is not flammable except when lit at a stove, and it can not explode.
If a saboteur were to puncture the bag and light it deliberately it would flare off in a few seconds. If a flaming arrow was shot into the bag it would flare off in a few seconds. And since the bag is made of flexible plastic, if a saboteur were to inject air from a scuba tank into the gas bag and try to plunge a flaming spear into the bag the plastic would simply rupture and the gas would flare off in seconds. There would be no explosion and no noise other than a slight "whoosh" even in this most extreme of unlikely scenarios. We've been doing home biogas indoors in New York and Pennsylvania for 3 years and can't find a way to make the systems even remotely dangerous. Outdoors the risk is essentially near zero, by the laws of biology, chemistry and physics. The only risk posed would come from deliberately drinking the compost tea perhaps or by deliberately lighting the gas in one's face or sticking one's hand in the stove. We routinely bring full bags of biogas into our classrooms and cook eggs and bacon and pancakes with the gas, and have had fire inspector approval for this in several states.
In Alaska in a high school the fire marshall gave his approval saying, "even if you set the system on fire deliberately, it would be self-extinguishing due to the full bladder of water beneath the small quantity of biogas, which itself is 30% carbon dioxide which acts as a flame extinguisher and ensures the biomethane portion never accumulates... the biomethane almost instantly disperses when not captured and directed to the stove. Even a stove left on poses no hazard. And the regulated flame on an active stove only lasts two hours from each bucket of food waste fed, which occurs at most once a day. If lit, it is thus more like a pilot light with a limited supply of gas. The gas runs out quickly if the valve is opened, posing no risk. If it is not fed, it won't produce gas at all. So it is very easy to control.
It also takes about three weeks to start bubbling any gas out when first filled with liquid and inoculant. So once it is set up it won't do anything for nearly a month. Then the gas bubbles from the liquid bag into the gas bag at a rate of a few bubbles every 5 seconds or so. If the gas bag is full and people kept feeding it (which they would not) then it would bubble out the overspill so slowly that it would be almost undetectable and certainly could not pose a hazard (think of it like a pond which itself is a biodigester, releasing little bubbles of biogas every 5 or 10 seconds. Our bodies actually do the same thing. These can not be easily ignited and certainly pose no hazard, as many children have discovered trying to light flatulence.)
HomeBiogas can supply more thorough information and will send you results from the many installations in homes in Israel and elsewhere. I just thought it would be nice to give you my analysis after my own many years of use. I allow my children to play around mine because I feel it is so safe and so much better than our previous compost bins or garbage bins. We put one in our house because it eliminated rather than created problems.
I hope that as more and more people install these simple systems around the world you will find an opportunity to walk around a homebiogas system and see it and get a sense of what it is all about rather than just using pictures and your imagination. It is lightweight when it is unfilled with water and when first set up completely inactive so it can be easily carried around to different locations by a couple of people so you can see where you might want to place it in or around your home before committing and filling it with water. You don't have to make quick decisions with this system; you can set it up and move it about and can get people in your family, neighborhood or community to actually see and touch this exciting new problem solving appliance to get everyone comfortable and get total buy-in before you commission it with innoculant and put it into service. Once it is filled it will weigh about 700 kilograms, so you don't have to worry about somebody walking away with it, but if you want to move it you can always drain it conveniently and put it in a more suitable location.
At some point they will be as ubiquitous as washing machines and garbage cans (and a whole lot better!).
Thanks for taking the time to meet with us the other day and brainstorm and I look forward to more problem solving with you!
T.H. Culhane, Ph.D.Question:
Is the HomeBiogas system from Ecogas Israel safe for use in MY home?