Home Biogas system- part four- the mulch pit

Since the toilet is up and running, we need to get the mulch pit finished. At the moment it is hard to concentrate on any project. The constant threat of fire and the despair that comes with knowing that so much of our ecosystem is destroyed keeps us in a constant state of depression. It is hard to concentrate on anything except watching the media releases about the fires all over Australia. However, it is important to keep working towards the future we want; how else will we reach it? In between the fire threats and increadibly hot days we made a plan that involved digging a pit to drain the effluent into then covering the lot with gravel, wood chip, soil and mulch.

The biogas system continues to impress me, the only down side I have discovered is the flammable nature of methane (which is kind of the point) and the fact that we can’t move the unit away from the house in the event of a bushfire threat (we are at a count of three direct threat situations so far in the last twelve months). We have countered this by releasing the methane into the atmosphere when there is any risk of fire. There is a handy tap that allows the gas to be vented easily. The refill time is getting less every day; currently the tank will fill in about ten hours and the effluent has proven fairly easy to bucket into the old toilet pit on a weekly basis.

Since the effluent is from human poop, it needs to be handled carefully. The effluent is passed through a chlorine chamber before it emerges from the unit. Treatment with chlorine is the accepted way to treat human effluent, it kills off a lot of nasties and oxygenation and exposure to sun takes care of the rest. After it emerges from the unit our effluent goes into a bucket, which is then emptied into the old toilet pit (which helps the waste in this pit continue to decompose). It is time to put in a hands free option for handling the effluent. In our situation we have several options; we could feed it into our septic system (except we don’t have one), we could build a dedicated transpiration pit or we could build a mulch basin. We went with a combination of the transpiration pit and the mulch pit ideas.

First we (and by ‘we’ I mean my hard working partner) dug a pit that was about 40cm deep.

I took this photo after we had begun to fill the bottom with gravel.

Then we put in a layer of gravel in the bottom. This layer is about 5cm deep. The plumbing part of the project was then completed before the pit could be filled up all the way.

Next step was adding a straw layer to slow down the migration of soil into the gravel.

After that there is a layer of wood chips (to soak up any nitrogen rich moisture that makes it that far) and a layer of soil to seal the pit off from the surface.

After that I planted the passionfruit vine I bought to (hopefully) take advantage of all that moisture and nutrient. I mulched around the vine, then realised that it is now a fire risk and would be raked away when the next fire threatens. To counter this a little, I buried the mulch under a deep layer of soil again. I hope this will protect the mulch from ember attack in the event of a fire.

So now we have a new garden bed that doubles as a transpiration pit. Hopefully the roots of the passionfruit won’t bung up the draining system and hopefully the buried mulch will be safe from ember attack (I am thinking that this method might be good for the new vegetable beds when we get to that). We, like most of Australia, are still in shock from the magnitude of the fires this year. We fear that next year will be more of the same, so everything we do from now on needs to be focused on fire safety and how to keep our family safe.

Home Biogas system- part three- the toilet

We finally got around to putting the toilet on the biogas system. Mostly because the old pit toilet is VERY full (no pictures), and I developed a tummy bug over the weekend. These two factors in combination drove me to push everyone to throw together at least a temporary fix for the increasingly urgent problem of the full pit toilet.

The inside of our new toilet. Only another humpy dweller is likely to understand just how exciting this moment actually is.

The pit toilet has been great for about five and a half years. It took a month to build, and it was a great relief to have it finished at the time. If you click the links, you can read all about that adventure. Since the worms seem to no longer be living in the pit, and there are very few flies around (a worry of a deeper kind), the pit has filled to the point of being in danger of over flowing. We never did get the toilet building built, instead we continued to replace the tarp stretched over the top on a yearly basis.

The new biogas toilet will have a similar privacy situation, and the plan is to build a solid structure over it (but given our past experience, I don’t know when/if that will happen). The kit came with almost everything we needed, so instead of taking a month of labor (on and off) to build, it took me a frantic two hours (and a bit of help with lifting and drilling) to put the basics together.

First, I found a solid pallet in the useful pile in the sheep pen. This pallet will need to be replaced fairly soon as it is not made from hardwood, but it serves the purpose for the moment. The pedestal is bolted onto it using four roofing screws and another piece of timber under the screw holes to give it a bit of security. The pedestal feels solid and reliable, and the extra height brings it up to the western conventional position.

The temporary bucket set up
The kit even has a filter for the flush water.

Secondly, the flush side of the plumbing was set up. I just pushed the inlet hoses onto the inlet spout on the toilet and put the filter on the pipe, then dropped the free end into an old bucket (with water in it). The bucket holds some precious second use water from the sink where we wash our hands. Usually we use this water on the garden, but we are forced to put some of it through the biogas system now.

You can clearly see the hose connections in this photo
The outlet hose goes into the biogas unit. There is about 2 metres of hose inside the unit to be sure the poop is delivered to the bottom of the bacteria colony.

The last step is to connect the outlet pipe to the toilet and feed about two metres of pipe into the unit to be sure the poop goes where it needs to go; to the bottom of the unit where the most bacteria live.

The toilet is operated by setting a switch to either a 1 or a 2 (I figured out that this is 1 for pee or 2 for poop) and pumping the handle up and down until everything goes away. It is comfortable and easy to use.

The effluent currently flows into the white tub and is used on the garden, but now there will be human effluent rather than just horse poop going into it that will need to change.

My next job is to connect the effluent pipe to a transpiration or mulch pit. Since we have been using only horse and occasionally dog poop in the unit (along with some food scraps) and the effluent is filtered through a chlorine tablet, I have been using it on the garden to feed all my plants. Now the human poop element has been added, I will have to divert the effluent to a mulch pit or another underground absorption situation. The tummy bug that made this job so urgent also means that I am introducing some not so human friendly bacteria into the unit and I don’t want to risk those bugs getting loose among the other humans of the house. Since my fairly useful partner is in town getting fittings for this phase of the job, I will make that the subject of another post.

The biogas situation at the moment is wonderful; I feed the unit about half a bucket of horse manure and any food scraps or dog poop I collect through the day (most food scraps go to the chooks though) and we can burn the methane for about two hours a day. I expect to get better gas once we are feeding the unit fresh manure (ours) rather than days old horse poop.

Biogas system update

I realise I should have posted about how the biogas system is working a while ago, but…better late than never.

The system took a while to produce gas, it sat for weeks looking sad and deflated, even though I fed it a bucket of horse manure every day for the first week.

Eventually the weather got warm enough and the microbes in the tank woke up and started to feed. The gas holder slowly filled up until it was just over half full. I really wanted to try out the burner to see if we have methane in the tank or just carbon dioxide (which is apparently common in the first few months).

We connected the gas line to the stove that came with the kit as soon as the gas holding…balloon? (I’m not sure what to call the thing that holds the gas) got to almost full.

The gas balloon about half full.
The gas line connected and running through PVC pipe to the house.
The gas line into the house.
This is the cute little burner that came with the kit.

The first lighting of the flame ; this was a momentous occasion. We lit the flame and it just hissed at us for a few seconds, then an almost invisible blue flame was born. We boiled the kettle for the washing up in about 5 minutes and celebrated with a coffee…then I made soy milk…and my daughter made a stew…and so on.

Our first water boil using biogas. The flame is almost invisible.

The gas balloon went down a lot in that first afternoon as we used the burner constantly (that’s what you do with new toys isn’t it?). After that I went back to feeding the system a bucket of manure every day. The colder weather certainly slows down the gas production and we don’t have enough gas to use as our only supply just yet. Once the toilet is connected to the system the feeding of the digester will hopefully take care of itself.

I am sold on biogas; even though the initial set up of the bacterial colonies takes so long (especially in Winter) and the refill time is fairly long at first, the system works and is improving daily.

Home biogas system- (part two)

It’s finally warm enough to start setting up our biogas system. A few weeks ago we got one of our neighbors down to help us level a pad for the unit and we gathered together all the bits and pieces we needed to set up the first part of the unit (the digester and gas collector part), we will set up the cooker that came with the unit once it is producing gas. The toilet attachment will be installed as part three of this project as we have to wait until the unit is active before we add human manure to the mix.

The unit will be to the North of the humpy, close to the kitchen and right beside the toilet. That way the gas does not have to travel far and neither does the poop.

Thanks for the help Louise.
A nice level pad for our biogas unit.

Next we laid down a ute mat made of rubber to protect the digester from any sharp stones that might be in the soil. The unit came with it’s own rubber mat, but we wanted to be sure it was protected. The extra rubber also insulates the unit from the cold soil a little.

Then it was time to put the pieces together and set up the unit itself. There is a really handy app that talks you through the whole process.

It looks like putting up a tent.
Can you believe the kit also includes a tiny tub of Vasoline to use as a lubricant for putting the puzzle pieces together?
There is even a little bucket to use as a measure when filling the sand bags (provided).

Filling the unit with water felt like a real achievement after all the brain work of putting the jig saw together. While it was filling up we got busy filling up the sand bags that become weights for the gas collector (the unit uses these weights to put the gas under low pressure so it is pushed through the gas line to the stove).

Filling with water took all afternoon.

The following sequence of photos show fairly clearly how to fill and seal the bags so there is not much air in them. This is important as the pockets the bags go into are quite narrow and the bags have to be squeezed into them.

The gas collecting bag is strapped onto the top of the digester then the gas and inlet lines are attached.
As the sun sinks rapidly into the West, we begin to fill the unit with cow manure.
A total of 3 feed bags of cow manure went into the unit tonight, we will add more over the next week.

The unit will begin to bubble and produce methane over the next few weeks and we will add the gas line and the toilet as part of the next stage. Look out for the next installment in a fortnight…