Carbonized Solid Fuel Production from Polylactic Acid and Paper Waste Due to Torrefaction

Area of Science:

• Waste Management
• Renewable Energy
• Materials Science

Background:

• Increasing quantities of biodegradable plastics in waste streams lower the calorific value of municipal solid waste and refuse-derived fuel.
• This reduction impacts feedstock suitability for cement and incineration plants.

Purpose of the Study:

• To investigate the torrefaction of biodegradable waste, specifically polylactic acid (PLA) and paper, for carbonized solid fuel (CSF) production.
• To evaluate process yields, fuel properties, kinetics, and energy/mass balance.

Main Methods:

• Torrefaction experiments were conducted on polylactic acid (PLA) and paper.
• Thermogravimetric analysis (TGA) was used to determine decomposition kinetics of PLA.
• Process yields, fuel properties, and theoretical energy/mass balances were determined.

Main Results:

• Torrefaction did not improve the calorific value of polylactic acid (PLA); the process was not self-sufficient.
• The calorific value of paper was improved by up to 10% through torrefaction.
• Thermogravimetric analysis showed PLA decomposes in one stage (290-400 °C) with a maximum at 367 °C, following a 0.42 reaction order and 160.05 kJ·(mol·K)^-1 activation energy.

Conclusions:

• Torrefaction is not a viable method for enhancing the fuel properties of polylactic acid (PLA).
• Torrefaction can improve the calorific value of paper, making it a potentially more suitable feedstock.
• Understanding the decomposition kinetics of PLA is crucial for waste-to-energy process design.