Biomeiler is a solution where we can get water-based heat (45-60°C) from wood chips, while creating carbon rich soil, instead of burning the materials for heat. It is basically a large compost with a heat exchanger, containing wood chips (70-80%) and manure (20-30%), watered to kickstart the composting process and for microbes to start breaking down the mixture to soil, while producing heat.
By pumping in cold water through plastic pipes (>130 meter), the compost is cooled so that it doesn’t burn too hot (otherwise reducing the quality of the resulting soil) while the warmed up the water can be used, for example to heat a small house.
A biomeiler of about 10 m3 in size produces 1 kW heat, but it depends on many factors, for example on what kind of manure you use. There is also a minimum size in colder climates, such as the Baltics, in order for the process to not die off, often >30m3. The working time of a Biomeiler is between 6 to 18 months before being taken down and rebuilt with fresh organic materials.
Complexity and cost of building and operating
Building and operating:
Medium (partially DIY, medium maintenance/operating complexity)
High (>500 EUR)
Building a biomeiler needs some tractor work and a few people. Material costs are high, because fresh woodchips can be expensive, unless you have your own access to them. Pipes, wire mesh, pumps and other materials are also needed for the system to function. These are however reusable for many seasons.
Materials, skills and tools required
Materials for building a biomeiler:
- Fresh wood chips – 70-80 % of the total volume;
- plastic to bottom;
- culvert pipe in the bottom to remove excess water;
- manure (free from antibiotics ) – 20-30% of the total volume;
- water to make biomeiler wet - 32mm plastic pipes ca 600meters (depending on the total volume);
- iron net / wire mesh for shaping the biomeiler into a round pile;
- small circulation pump for heating water.
Equipment and labor force:
To build a biomeiler you need a tractor, hand-tools (like shovels, etc.) and a group of people (at least 2-3 people or more)
Wood chips must be fresh
(less than 3 weeks from cutting) and compost must be wet enough.
Take care of its irrigation during the construction!
Description of the solution
Biomeiler, also knows as Jean-Pain Compost, is a solution providing water-based heat up to 45-60°C produced by composting process. The compost provides both the heat and the material for carbon-rich soil, instead of burning the materials for heat. It is basically a massive heat exchanger consisting of wood chips (70-80%) and manure (20-30%), watered to kickstart the composting process and for microbes to start breaking down the mixture to soil, while producing heat.
Life Cycle Analysis
A good functioning biomeiler are suppose to produce more heat over its lifetime from the microbial process than what could be extracted if burning/combusting the woodchips. As new soil is produced from the compost, the lifecycle or footprint of the solution can be viewed as positive or regenerative.
The materials used for the system, such as plastic for the pipes or metals for pump or mesh, should be taken into the LCA of the solution, but since these are reused for many years before being recycled, the total footprint of building and using a biomeiler can be considered very low.
The initial costs of building a biomeiler are quite high as all the materials and systems that later can be reused needs to be purchased. The annual cost of rebuilding the biomeiler are about 500€ for woodchips and transport of these, depending on location and size of the biomeiler.
Biomeiler produces heat ca. 800-1000 kWh/m3, depending on woodchips. Woodchips price is same when we are burning and composting.
The working time of a Biomeiler producing heat is between 6 to 18 months after which the compost material is to be used for soil improvement.
Step by step guidelines for building
1. Build the walls to round shape and lay plastic on the bottom. (In the picture straw bales are used for walls instead of wire mesh)
2. Add to bottom culvert pipes that collect excess water away.
3. Fill the biomeiler with mixture woodchips and manure and add plastic pipe in spirals in 2-3 layers to compost during building. Make sure that both ends of the pipe are accessible from the outside of the biomeiler.
4.Connect the composts heating line. Add a circulation pump in an insulated place.
5. When compost is ready it is good fertilised soil for plants or for example greenhouses. Other materials and equipment can be used for the next biomeiler.
Before starting constructing a biomeiler, check your local regulations on what is needed as the construction involves manure. Local regulation connected to groundwater may apply.
Local Prototype – Vaasa Meteoria Biomeiler
The biomeiler in Meteoria Vaasa was completed in December 2019 and heat energy extraction started in that same month. The heat collected is used for the heating up of the conference room (barn). Shown in the figure 1 below, the schematic drawing of the boiler energy system, showing the different elements and layout of the systems.
Construction and Dimensions of Vaasa Meteoria biomeiler
The biomeiler has a capacity volume for biomass of 50 m3 as can be seen from the schematic figure above. The biomass used in this biomeiler is horse manure due to its slow decomposition rate consisting of 40% of the total biomass. The rest of the material used is wood chips (60%). In the initial stage, about 10-12 m3 of water was added, some added to the pile and some mixed with the biomass before adding the biomass to the biomeiler.
No plastic material was added to the borders of the biomeiler, this was to allow for aeration and it cannot be proven that omitting the plastic material has a negative impact as will be shown in the coming chapter. The construction wire is for holding the structure in place and the wire mesh inside is for holding the biomass.
The biomeiler has a 300 m hose running through it coiled in 100 m lengths in three layers (the bottom, middle and about 70 % to the top) of the biomeiler to spread the collection of the heat. The temperature sensors are installed at each layer on different positions, accounting for more than 25 temperature sensors in the biomeiler alone and are connected to an online data collecting tool via Raspberry Pi. The biomeler is insulated with hay to reduce heat losses to the environment caused by the temperature difference of the surrounding environment.
The local residents assisted in the construction of the biomeiler providing free manpower, horse manure and some other resources as can be seen in figure 3 below.
Instructions and installation
Heat extraction started in the mid of December 2019 and the figure below shows the timeline of production by the biomeiler and steps taken to try and increase heat generation in the compost.
The temperatures shown in the graph are an average from various temperature sensors in three different positions of the biomeiler. The blue line indicates the temperature readings from the sensors located in the middle of the composts, the orange line represents sensors in between the middle and the edge of the biomeiler and the grey line is for the sensors on the edge of the compost. The various temperature outputs from the compost can be seen and the period of these outputs ranging from the middle of December 2019 to the mid of March 2020. The graph below also shows the timeline of activities that has occurred during the recorded period.
In order to extract more heat from the compost, 750 liters of warm water and 50 liters of horse urine was added to the compost in the end of January, to boost the nitrogen levels in the compost and also maintain the moisture levels.
The outer insulation made of hay was removed in February, in order to see the effect on temperature sensors and check for the moistureness of the biomass in the compost. In the beginning of March, 1.500 liters of water and 30 liters of urea was added to the compost. Not shown in the graph, the end of March, about 1 m3 mixture of cow dung and urine. The mixture was added to the compost by creating a crater on top of the compost and let the mixture sip down gradually. No further data has been recorded in the period from the beginning of April due to some problems in the weather station.
Observation and Conclusion from heat extraction results
As seen from the graph on the Figure 6, there is a clear drop of heat in the biomeiler from the mid of January from a staggering ~60˚C to below 30˚C, but still a significant difference in locations of sensors. Given that horse manure decomposes very slowly, it still raises a question of how the decomposition occurred so fast. It was also observed that the outer sensors showed much lower temperatures throughout, an indication that there was air flow from the surrounding environment. It is also an indication that this is an aerobic process and was getting oxygen from the surroundings.
Another indicator of the presence of oxygen and moisture was when the tarpaulin was removed, the biomass was still moist and all temperature sensors showed a tiny drop in temperature. Nitrogen is an important element in this process and it is an element that is present in urine and excretion matter. After the addition of horse urine, the temperatures from the middle and intermediate sensors showed an increase in temperature of about 5 ˚C but the temperatures dropped after removing
the tarpaulin. When next urea and water was added, only the middle sensors showed an increase in temperature. One explanation for this is that the water and nutrients do not evenly spread out in the compost, it takes the easiest way down.
Not shown on the graph was when cow excreta mixture was added, on the occasions the readings were observed, the temperature sensors showed temperature readings of above 30 ˚C. However, it was the same observation as in previous steps that it is difficult to evenly distribute the extra nutrients in the biomeiler once it is compiled. Adding nutrients to a compost at a later stage is a challenge as there is no even
distribution of the extra nutrients. This makes having a correct biomass composition from the initial stage important.
Further observing the biomeiler, it was noted that it had been transitioning into hibernation from the time the temperatures start dropping to below 20℃ as can be seen on Figure 6. The temperature started rising gradually towards the end of May
2020. Looking at the weather patterns in Finland, the period the biomeiler was in hibernation falls in the cold season for Finland, leading to a conclusion that the insulation around it did not help much and could have fallen below the optimal
operating temperature for the enzymes. A clear conclusion can be researched by observing the biomeiler for a longer time and observing the change in temperatures during different times of the year.
From Figure 7 above, it can be seen that the biomeiler has reached the peak values of temperature and has remained stable to time of writing this (September 2020). The biomeiler’s live data as well as back data can be followed and accessed through the website http://iot.novia.fi/data/meteoria_biomeiler.html.
Basing a conclusion on this biomeiler, further observations should be made to concretely connect the impact of atmospheric conditions on a biomeiler. The earlier conclusion
reached that since the difference in particle size between horse manure and wood chips is wide, some of the horse manure ran out with water and the wood chips were too big
to start breaking down in such a short time frame so that they compensate for the depletion in the horse manure is now hard to fully support. Other questions are if the extra nitrogen added to biomeiler was necessary in the first place and on one hand if this could be a solution to sustain biomeilers in very cold regions during the cold season.
Community or Organisation operating the prototype
Meteoria, Vaasa, ProAgria Länsi-Suomi ry.
Energy expert: Jukka Kontulainen
Seppälä Agricultural College: Renne Sänisalmi, teacher.
Jukka Kontulainen – firstname.lastname@example.org
Mari Korhonen – email@example.com
Shiva Sharma – firstname.lastname@example.org
Cynthia Söderbacka – email@example.com
> Summary in Finnish
Experiences from the Meteoria site
Future data and experiences from the Meteoria biomeiler will be submitted here.
During Off Grid DIY project two prototypes were built in Finland: One in Seppälä Agricultural College in Kajaani, one in Meteoria, Vaasa.