Compost Compressor Category: fun

Tom Rasmussen
Fri, 04 Nov 2016 11:47 AM


By Kevin Qian, Tom Rasmussen, Rhys Watkins, Arthur Kuan


Task given: Use what you have got to make the world a better place


Initial thoughts

  • Would be good to use materials which would otherwise be disposed of or wasted.
  • Also to increase accessibility of the design, would be good to have it reasonably simple


Understanding of the topic

  • Making the world a better place doesn’t necessarily mean create an invention which solves all problems but rather one which could make the world a little better.


Our initial possibilities:


Water purifier

Cheap mosquito repellent

Portable air conditioner

Trash compactor

Biomass compressor




We decided to make a the biomass compressor. In today’s increasingly industrialised society, our unfortunate dependence on non-renewable sources of energy is at extreme levels and thus the need for renewable sources of energy is at unprecedented levels. One of these sources is biomass. Biomass power is created by using organic waste materials and turning them into usable fuel, which in turn can be used to produce electricity or burned for heat. As a result, we decided that our first step of thinking would be to create something that can make something useful out of organic waste.


In our product, we are planning to compress biomass so that it may be used as fuel. This will be achieved via a simple lever system. Essentially, raw biomass with be put into into a tube, and then a plunger will be inserted into that tube, and lastly a lever will be pulled up which will push the plunger down, compressing the biomass. This contraption will be mostly made of wood, and the tube will be a section from a PVC pipe. Note that both of these materials are very common found, thus increasing accessibility to this design.


Organic waste is an underutilized resource. In a recent study, it is estimated that 50-70% of developing countries’ Municipal Solid Waste, AKA common garbage is organic material. This waste is normally dumped in landfills with only 10% of this organic matter being used as a resource. Not only is this a waste of a resource but also the build up of this organic material in landfills produces methane, a greenhouse gas more potent than carbon dioxide. Global methane emissions from landfill are estimated to be between 30 and 70 million tonnes each year. Now imagine if we could divert this waste from ending up in a landfill while producing something useful.


Our group’s vision is to try and utilize the underappreciated resource of organic waste. We looked at composting as a current strategy for utilization of organic material. When we looked at composting we noticed the reason why it was such an effective strategy was because it was so simple and could be adopted by almost any household. We took this idea and then began to start thinking about strategies we could develop to then use in countries that would need it most. We want our strategy to be locally deployable and cost efficient. This is because if our strategy isn’t cost efficient there is a very slim chance developing countries will adopt it in the future.


Our group initially recognised that biomass is a far more sustainable and less pollutant resource in comparison to non-renewable sources of energy. Kevin’s chemistry knowledge helped us develop our strategy for the way to utilize this organic waste: organic waste can also be called biomass. Biomass refers to living or recently living organisms. Biomass is mostly composed of carbon, hydrogen and oxygen. When carbon based materials such as biomass are converted into useful forms of energy (for example via burning), the carbon within them is converted in carbon dioxide. Although carbon dioxide, a greenhouse gas, is released from biomass, a major difference between biomass and non-renewable sources of energy is that biomass is produced at far greater rates than non-renewable resources such as coal. Thus, while on one hand the carbon released from coal has already been trapped from millions of years, the carbon released from biomass forms was recently already in circulation. Therefore a constant balanced cycle of carbon has formed between plants absorbing carbon dioxide and biomass being burnt and creating carbon dioxide. Nevertheless, when non-renewable sources of energy are utilised, this cycle becomes unbalanced as additional carbon normally trapped within fossils fuels are released.


Our idea was to apply Kevin’s findings and knowledge to create our design, Rhys’s knowledge of physics and Tom’s knowledge of biomechanics helped our group come up with a design which can compress organic waste to become biomass fuel.


The physics behind the compressor is very simple. When a force is applied on the lever upwards, it pushes the plunger mechanism downwards with equal force on the material in the pipe. Because of this it puts a lot of strain on the pole that the lever is attached to with the bolt. The larger the force that is applied to the lever handle, the more force that will be applied on the base of the pole. As a result we used a combination of PVA glue and screws to secure the pole to the base. The force applied on the object is used to crush and compress the organic waste into a hard brick of what is essentially biomass. The holes in the PVC piping allow for both air and water to escape. The air is released so that we can compress the biomass, without any dangerous buildup of pressure. It is important that the water is released so that the biomass can be dry, an important requirement for any carbon based fuel to be used. Secondly, this water can be collected and be reused.




The first image shows our initial very rough design for this compressor. The idea is that of a class one lever, which uses a fulcrum  the 1.2m plank of wood. On the longer side of the fulcrum is the where a person would lift up the plank of wood, which then forces the other side downwards. The longer the plank on the side where the person is pushing upwards more force can be generated. This is because the distance the plank of wood travels is increased meaning the amount of effort needed move the plank upwards is decreased because the force is dispersed over a greater distance. Another practical benefit of the longer plank is that more people can lift upwards. On the other side of the machine is a plunger attached by a bolt to the main plank. When the person, or people lift up the main plank the plunger is forced downwards to then compress the biomass. We took the idea of a class one lever and applied it to our design to create the first prototype for this idea.




We talked to Mr. Burgess from the technology department at the start of the morning. The most important thing that we’ve learnt from talking to him is that the materials we are going to use (wood and screws) will be cheap, which means that our design will be under twenty dollars. Furthermore, the fact that our design would be made from mostly offcuts/unwanted pieces of wood further decreases the price of the materials. Additionally, before we start building, we were told that we needed to come up with a solid design.


Acquiring the materials we required for the construction of our design was more challenging than we expected. Though we had our dimensions, we still had to cut the wood that the tech department had given to us into the dimensions required. For this process, we had to use a variety of tools including hacksaws and tenants. Rhys had also managed to acquire a PVC pipe that could be utilised to extract the liquid from waste.


Compared to acquiring the materials, the construction of our design was easier. Using a combination of screws, bolts, nails and glue, we managed to effectively construct the shape of our design. We had issues gaining long enough screws, but after talking to Mr. Burgess these were solved. All the joints work effectively, and everything is fastened to an degree.


Construction of the contraption took place in a number of steps:

Firstly, we connected the fulcrum to the potential lever via use of a bolt. Secondly, we attached a base to this, consisted of two planks of wood. Lastly, we made a plunger system, where potential biomass would be deposited and compressed. Throughout the process, we encountered a number of setbacks and made some mistakes. For example, we initially accidentally attached a very thin, flimsy block of wood as the fulcrum, which we later corrected. Note how all of the wood on our contraption are sturdy, with a square cross section.


After finishing the construction of our prototype, we brought it back science block from the technology block quite easily, meaning that it was portable and lightweight.




The Final Product

Our product was a success to an extent. The final prototype did not meet our expectations. When we started to test our design by crushing apples. We found that there was a major issue with the central fulcrum point, as the amount of pressure required to crush organic material could not be applied without the central point of the lever being put under a critical amount of stress. However, we found that one could still crush the apples and squeeze the liquids out of them if one did so carefully.


The first of these was that the materials were simply not strong enough to cope with the large force that we were trying to use to crush organic material. Whenever we attempted to crush the test apple core’s it would crack the wood or the piping. And despite our attempts to secure the pole to the base, the wood still cracked if too much force was used.


The second issue was the design. This was the first time any of us attempted to build anything like this. So all of the design was purely theoretical and while we used a rudimentary design, it would have been more beneficial if it looked more similar to the design below. Part of the scientific process involves refining ideas and for us it means improving the concept. The concept design below is preferable to ours because it is stronger and the site we found it on, claimed it should generate at least two tonnes of force. The main difference between this new design and ours is that ours was long and flimsy, where as this one is very strong and the strength comes from its compact nature. If we were given more time it is very likely that we would try to take the best aspects of both designs to create a working model.  


Conclusion and Evaluation


Overall, we believe that the group worked well and used its members’ various areas of specialties to create something of value. All members have different skills and ways of thinking. We tried to combine the best aspects from each discipline of our sciences to create this prototype. Arthur’s knowledge of biomass and Kevin’s understanding of chemistry helped reach the idea of compressing organic material to create biomass. Rhys and Tom’s knowledge of physics and biomechanics allowed us to actually create the product. Everyone assisted in creating this product.


The actual prototype was a mixture of success and failure, as previously discussed. In some ways the prototype was a success. It could compact, to a certain extent, organic waste. However, the amount of pressure needed to create Biomass fuel would have broken our fulcrum point.


The main success was the way our group came together and worked collaboratively. Our thought process and our scientific method was great and it was fun working together and it shows how a mixture of all sciences can create something brilliant. There was also cultural and social significance in the making of our product. We knew this product needed to not only help people but empower them. A more finished version of a product can be used locally and by the people who are actually in need. This means those people use this product the way they want to, this gives them a sense of achievement as well as productivity.


If we were to do this again we would spend more time thinking theoretically. Due to the time limits, after a few quick sketches we dove straight into crafting and building the contraption. If we had thought to draft some other ways a compressor could be effectively built we might have designed a more effective lever to begin with. Nonetheless our experimental process has still proven how an effective compost compressor could be made with recycled materials and some bolts. Overall, we believe that the concept of our biomass compressor is very good and with time, it may be developed at a far bigger scale. For example, a way this compressor may be improved is by using cheap, yet heavy duty materials such as iron to increase the amount of potential force able to be applied.

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