A CSIR-designed and constructed anaerobic biodigester was granted a provisional patent recently. The pilot-scale biodigester is located on the CSIR campus in Pretoria.
Dr Thulani Dlamini (right), CSIR Group Executive: Research and Development, and CSIR researcher Mauritz Lindeque at the newly designed anaerobic biodigester that was granted a provisional patent recently.
"While not the first anaerobic digester on the market, this digester could potentially have a huge impact on renewable energy requirements of rural areas that are off the national electricity grid," says Mauritz Lindeque of the CSIR. "The biodigester could treat the separated sludge for up to 50 households and contribute to their daily energy needs by producing biogas as a renewable fuel source. The pilot digester can hold 360 litre of municipal waste, which includes human and animal sludge and other organic material," comments Lindeque.
The biodigester project follows on earlier research funded by the CSIR and the South African National Energy Research Institute (SANERI) to investigate the conversion of organic waste, such as human waste, into biogas via the anaerobic digestion process. The first phase of this project consisted of investigations undertaken by Dr Harma Greben and other CSIR colleagues to establish whether paper waste could be digested. The success of that research led to the digestion of kitchen waste and other waste products, which resulted in the production of biogas.
Greben involved colleague Steve Szewczuk at that stage, who pursued the establishment of an automated pilot-scale anaerobic digester. Lindeque based his MSc thesis on this project, submitting a dissertation on the engineering design of a biological process to the Centre for Alternative Technology of the University of East London in the UK.
The CSIR biodigester has been designed and constructed with off-the-shelf hardware that will be readily available in remote areas. Most general dealers and hardware shops will be able to supply the equipment needed for construction and maintenance. Due to the simplistic design, people with limited skills will be able to maintain the hardware. Operators won't have to manage the required parameters - these are computer-controlled, which will also reduce failures and shut downs due to human error.
"We use renewable energy - solar energy - for converting the digester's energy into a renewable fuel like biogas. The digester allows for the safe harvesting of biogas, a green house gas with a methane component that is 22 times more damaging to the environment than CO2," Lindeque notes. In addition to producing biogas, the process will render stabilised sludge as an organic fertiliser and treated grey water, which can also be used as an organic fertiliser.
"The equipment runs on an automated system and reduces the retention time of the sludge by maintaining the parameters that assist in the biological breakdown of organic waste. The reduced retention time results in smaller infrastructure needed, thus reducing the space for accommodating the digester."
"We designed and developed the digester with the idea of growing the biogas market. We'll now aim to refine it with a specific market in mind, looking at the biggest impact and return-on-investment; the agricultural sector in rural, off-grid areas comes to mind," Lindeque concludes.