Energy Systems

PRI Sunshine Coast – Biogas Project Update, March 2013

On the 18th of March we started our biogas project. This project involves making a bio-digester which will turn manure into methane gas for cooking and other energy needs.

An update on a previous post, by Zaia Kendall


Outline of the bio-digester

Tom had to re-do some fencing and clear the site for the bio-digester. He calculated that with the amount of manure we are getting (around 30kg per day), we need a 5 cubic metre bio-digester, which will give us around 1 1/2 cubic metres of gas per day.

Lead up time to get the gas going will be around 60 days once we start filling the bio-digester. But we are not there yet, and here I have documented the start of the project.

We got a lot of questions about how we dealt with council etc. Since this is for private use and we are not selling the gas commercially, there are no hoops we need to jump through. So we cleared the site and started digging


The dig is started

Tom drew where he needed to dig on the ground, whereupon he used the excavator to dig the round hole (2.8 diameter), plus a square hole which will be part of the outlet. He also marked out where the inlet will be (small round circle on the right). He had to regularly check levels, to ensure the bottom was level and the sides of the hole were straight.


Completing the hole by hand

The hole was then further dug out by hand, ensuring the levels were correct and walls were straight. Tom then put a pole in the middle and measured the inner radius, thus determining where the bricks would need to go.


A pole in the middle to measure the inner circle (inside of the bio-digester).
The outer circle will consist of the double brick wall.

A tarp had to be placed over the hole, since we were experiencing some wet weather, and we needed a dry area to pour the concrete and did not want the hole to fill up with water.


A tarp placed over the hole to keep out the rain.
Bricks to be used for the walls in the background.


Deeper outer circle for better foundation

To ensure a good foundation, the outer circle (where the bricks will be for the walls) was dug out deeper. This way there is more concrete under the wall to hold its weight, which makes it stronger. We were lucky, there was only a little bit of water in the bottom of the outer circle, which meant that water had only just been struck. This was of no concern at this time, but strategies will be put in place to divert water past the bio-digester in wetter times.


Rio mesh put down (all materials apart from cement is second hand)

We put down rio mesh and then the concrete was poured. The post stayed in the middle so that we could still measure where the bricks were supposed to go. Once the concrete was hard, Tom attached some wire to the centre post which was as long as the inner radius, and then measured out where the bricks had to go. He marked the concrete with blue pencil and laid the bricks out so everyone could see where they were supposed to go and how they needed to be laid.


Starting the concreting, constantly leveling the concrete
to ensure a straight and level floor.


Concrete laid, with the pole in the middle


Wire attached to pole to measure inner and outer circle,
so the bricks would end up on top of the thicker concrete.


Bricks marked out and put down, ready to be cemented in.


Double layer of bricks, how they need to be laid.

They laid one layer of bricks that day. In the coming weeks we will add some more layers until we have a wall about a metre high. Then we can start the second stage of the bio-digester: The dome!

To be involved in the next stage of the bio-digester, "The Dome", please click here for dates and to book.

Further Reading:

Zaia Kendall

Zaia grew up in a family of musicians in Holland, and has a background in top sport and web development and design. She co-founded the PRI Luganville and PRI Sunshine Coast Inc with Tom, and runs all the background stuff, like finances, business administration, website design and maintenance, writes articles, records and edits videos and also organises the cooking and the kitchen on site. She has been researching and studying nutrition and health for 20+ years, has a certificate in Nutrition and continues to study by research, reading and daily observation. She is a certified member of the International Institute of Complementary Therapists and is a holistic food, health and lifestyle coach. She is also an active member of several musical projects and bands, involved in community music and runs occasional percussion workshops. Visit Zaia's website at DIY Food and Health.

One Comment

  1. No council permit or regulations at all? that is surprising – I wonder if this is Queensland wide or just your local council? Does a plumber not have to connect up/sign off on the gas lines?

    Thanks for sharing this project, great to watch and read your process, cheers

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