REEF Project Update: Heat from Compost

Three students from the polytechnic have joined forces to develop a project producing heat from biomass compost. The project tackles two problems in Malawi:

Waste biomass – currently discarded ending up in rotting piles next to local markets
Lack of hot water – energy costs make heating water expensive

In addition the process produces a high quality compost as well as the secondary benefit of creating cleaner streets as biowaste becomes more valuable.

Technical

The system is relatively simple compromising a custom made steel drum raised off the ground with metal legs. The underside is fitted with mesh to allow for oxygen to enter and allow the composting process to occur. An opening is fitted to the top of the device to allow for feed stock biomass to be added. As the biomass degrades heat is produced. The decomposing biomass makes its way to the bottom of the container and can be removed via a small door at the bottom of the device.

The temperature is greatest in the centre of the drum. Insulation of the drum has helped increase the temperature further. The team have currently reached temperature over 50C and are aiming to reach over 60C. Research is being undertaken regarding the optimum feed stock for heat creation.

Once a suitable heat has been reached the team will then work on a system for heating water, probably involving some sort of coil system inside the drum to heat the water as it flows through.

Challenges

The principal challenges faced by the team include:

Getting the temperature to a high level and sustaining it
Calculating the optimum feed stock for heat production
Developing a better system for accurately measuring the internal temperature
Developing a system for heating water

The system has been designed to be low cost and sustainable. The device was manufactured from cheap scrap metal using a local tinsmith. These skills and materials are present across Malawi, so with just a few drawings the design could be replicated elsewhere. There is also the potential to manufacture whole systems for sale. The feedstock is sustainable since there is always a ready supply of bio-waste from households, markets and farming.