Overview of Torrefaction Technologies: A Path Getaway for Waste-to-Energy

Abstract

The ever-increasing demand for cleaner energy to meet the rising demands of the technologically advancing population coupled with the serious impact of climate change has opened the door for research on different renewable energy sources to be researched and commercialised. Most of the power used for industrial and household use has been generated using mostly coal, water and nuclear over the years. However, all these energy sources are finite and beside water, they cause pollution mostly leading to greenhouse gases (GHG) emissions that are accelerating global warming. To reduce our reliance on coal as an energy source, biomass can be used alongside coal or as a direct substitute of coal. Torrefaction helps us to achieve this aim and the torrefied biomass has the net effect of reducing GHG emissions. Even without any significant upgrades to existing coalfired power stations, torrefied biomass has the distinct advantage of working in those power generation boilers as well. Nowadays, large-scale biomass-based boilers with a rating of over 500 MWth are being operated to produce power. Another advantage of biomass is that it does not usually contain a lot of sulphur and chlorine making it attractive for use in boilers as this reduces corrosion effects from such deposits. Torrefaction improves biomass properties by increasing the C/H and C/O ratios through removing permanent gases (CO2, CO, etc.) and volatile liquids (H2O, organic compounds, etc). In addition, torrefaction can be used to improve municipal solid waste, sewage sludge, food waste, agricultural waste, livestock waste, forestry residues and other waste generated thereby improving the recycling rate and promoting a circular economy.